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Sample records for cerevisiae microbial cell

  1. Thionine increases electricity generation from microbial fuel cell using Saccharomyces cerevisiae and exoelectrogenic mixed culture.

    PubMed

    Rahimnejad, Mostafa; Najafpour, Ghasem Darzi; Ghoreyshi, Ali Asghar; Talebnia, Farid; Premier, Giuliano C; Bakeri, Gholamreza; Kim, Jung Rae; Oh, Sang-Eun

    2012-08-01

    Microbial fuel cells (MFCs) have been shown to be capable of clean energy production through the oxidation of biodegradable organic waste using various bacterial species as biocatalysts. In this study we found Saccharomyces cerevisiae, previously known electrochemcially inactive or less active species, can be acclimated with an electron mediator thionine for electrogenic biofilm formation in MFC, and electricity production is improved with facilitation of electron transfer. Power generation of MFC was also significantly increased by thionine with both aerated and non-aerated cathode. With electrochemically active biofilm enriched with swine wastewater, MFC power increased more significantly by addition of thionine. The optimum mediator concentration was 500 mM of thionine with S. cerevisae in MFC with the maximum voltage and current generation in the microbial fuel cell were 420 mV and 700 mA/m(2), respectively. Cyclic voltametry shows that thionine improves oxidizing and reducing capability in both pure culture and acclimated biofilm as compared to non-mediated cell. The results obtained indicated that thionine has great potential to enhance power generation from unmediated yeast or electrochemically active biofilm in MFC.

  2. Outward electron transfer by Saccharomyces cerevisiae monitored with a bi-cathodic microbial fuel cell-type activity sensor.

    PubMed

    Ducommun, Raphaël; Favre, Marie-France; Carrard, Delphine; Fischer, Fabian

    2010-03-01

    A Janus head-like bi-cathodic microbial fuel cell was constructed to monitor the electron transfer from Saccharomyces cerevisiae to a woven carbon anode. The experiments were conducted during an ethanol cultivation of 170 g/l glucose in the presence and absence of yeast-peptone medium. First, using a basic fuel-cell type activity sensor, it was shown that yeast-peptone medium contains electroactive compounds. For this purpose, 1% solutions of soy peptone and yeast extract were subjected to oxidative conditions, using a microbial fuel cell set-up corresponding to a typical galvanic cell, consisting of culture medium in the anodic half-cell and 0.5 M K(3)Fe(CN)(6) in the cathodic half-cell. Second, using a bi-cathodic microbial fuel cell, it was shown that electrons were transferred from yeast cells to the carbon anode. The participation of electroactive compounds in the electron transport was separated as background current. This result was verified by applying medium-free conditions, where only glucose was fed, confirming that electrons are transferred from yeast cells to the woven carbon anode. Knowledge about the electron transfer through the cell membrane is of importance in amperometric online monitoring of yeast fermentations and for electricity production with microbial fuel cells. Copyright (c) 2009 John Wiley & Sons, Ltd.

  3. Increasing cell biomass in Saccharomyces cerevisiae increases recombinant protein yield: the use of a respiratory strain as a microbial cell factory

    PubMed Central

    2010-01-01

    Background Recombinant protein production is universally employed as a solution to obtain the milligram to gram quantities of a given protein required for applications as diverse as structural genomics and biopharmaceutical manufacture. Yeast is a well-established recombinant host cell for these purposes. In this study we wanted to investigate whether our respiratory Saccharomyces cerevisiae strain, TM6*, could be used to enhance the productivity of recombinant proteins over that obtained from corresponding wild type, respiro-fermentative strains when cultured under the same laboratory conditions. Results Here we demonstrate at least a doubling in productivity over wild-type strains for three recombinant membrane proteins and one recombinant soluble protein produced in TM6* cells. In all cases, this was attributed to the improved biomass properties of the strain. The yield profile across the growth curve was also more stable than in a wild-type strain, and was not further improved by lowering culture temperatures. This has the added benefit that improved yields can be attained rapidly at the yeast's optimal growth conditions. Importantly, improved productivity could not be reproduced in wild-type strains by culturing them under glucose fed-batch conditions: despite having achieved very similar biomass yields to those achieved by TM6* cultures, the total volumetric yields were not concomitantly increased. Furthermore, the productivity of TM6* was unaffected by growing cultures in the presence of ethanol. These findings support the unique properties of TM6* as a microbial cell factory. Conclusions The accumulation of biomass in yeast cell factories is not necessarily correlated with a proportional increase in the functional yield of the recombinant protein being produced. The respiratory S. cerevisiae strain reported here is therefore a useful addition to the matrix of production hosts currently available as its improved biomass properties do lead to increased

  4. A closed concept of extractive whole cell microbial transformation of benzaldehyde into L-phenylacetylcarbinol by Saccharomyces cerevisiae in novel polyethylene-glycol-induced cloud-point system.

    PubMed

    Wang, Zhilong; Liang, Rui; Xu, Jian-He; Liu, Yubo; Qi, Hanshi

    2010-03-01

    Extractive microbial transformation of benzaldehyde into L-phenylacetylcarbinol (L-PAC) by Saccharomyces cerevisiae (Baker's yeast) has been carried out in a novel polyethylene-glycol-induced cloud-point system (PEG-CPS). The extractive microbial transformation in the PEG-CPS and a downstream process for stripping of the product from the microbial transformation broth with microemulsion extraction are demonstrated. The results indicate that the PEG-CPS maintains the advantage of CPS for in situ extraction of polar product in the microbial transformation. At the same time, the utilization of hydrophilic nonionic surfactant in the PEG-CPS is favorable for stripping of product from the nonionic surfactant in the microbial transformation broth by Winsor I microemulsion extraction. Thus, a closed concept of in situ extraction of polar product in microbial transformation and its downstream process of product recovery are fulfilled at the same time.

  5. Dominance of Saccharomyces cerevisiae in alcoholic fermentation processes: role of physiological fitness and microbial interactions.

    PubMed

    Albergaria, Helena; Arneborg, Nils

    2016-03-01

    Winemaking, brewing and baking are some of the oldest biotechnological processes. In all of them, alcoholic fermentation is the main biotransformation and Saccharomyces cerevisiae the primary microorganism. Although a wide variety of microbial species may participate in alcoholic fermentation and contribute to the sensory properties of end-products, the yeast S. cerevisiae invariably dominates the final stages of fermentation. The ability of S. cerevisiae to outcompete other microbial species during alcoholic fermentation processes, such as winemaking, has traditionally been ascribed to its high fermentative power and capacity to withstand the harsh environmental conditions, i.e. high levels of ethanol and organic acids, low pH values, scarce oxygen availability and depletion of certain nutrients. However, in recent years, several studies have raised evidence that S. cerevisiae, beyond its remarkable fitness for alcoholic fermentation, also uses defensive strategies mediated by different mechanisms, such as cell-to-cell contact and secretion of antimicrobial peptides, to combat other microorganisms. In this paper, we review the main physiological features underlying the special aptitude of S. cerevisiae for alcoholic fermentation and discuss the role of microbial interactions in its dominance during alcoholic fermentation, as well as its relevance for winemaking.

  6. Microbial Cell Imaging

    SciTech Connect

    Doktycz, Mitchel John; Sullivan, Claretta; Mortensen, Ninell P; Allison, David P

    2011-01-01

    the maximum scan size (roughly 100 x 100 {mu}m) and the restricted movement of the cantilever in the Z (or height) direction. In most commercial AFMs, the Z range is restricted to roughly 10 {mu}m such that the height of cells to be imaged must be seriously considered. Nevertheless, AFM can provide structural-functional information at nanometer resolution and do so in physiologically relevant environments. Further, instrumentation for scanning probe microscopy continues to advance. Systems for high-speed imaging are becoming available, and techniques for looking inside the cells are being demonstrated. The ability to combine AFM with other imaging modalities is likely to have an even greater impact on microbiological studies. AFM studies of intact microbial cells started to appear in the literature in the 1990s. For example, AFM studies of Saccharomyces cerevisiae examined buddings cars after cell division and detailed changes related to cell growth processes. Also, the first AFM studies of bacterial biofilms appeared. In the late 1990s, AFM studies of intact fungal spores described clear changes in spore surfaces upon germination, and studies of individual bacterial cells were also described. These early bacterial imaging studies examined changes in bacterial morphology due to antimicrobial peptides exposure and bacterial adhesion properties. The majority of these early studies were carried out on dried samples and took advantage of the resolving power of AFM. The lack of cell mounting procedures presented an impediment for cell imaging studies. Subsequently, several approaches to mounting microbial cells have been developed, and these techniques are described later. Also highlighted are general considerations for microbial imaging and a description of some of the various applications of AFM to microbiology.

  7. Cell Wall Assembly in Saccharomyces cerevisiae

    PubMed Central

    Lesage, Guillaume; Bussey, Howard

    2006-01-01

    An extracellular matrix composed of a layered meshwork of β-glucans, chitin, and mannoproteins encapsulates cells of the yeast Saccharomyces cerevisiae. This organelle determines cellular morphology and plays a critical role in maintaining cell integrity during cell growth and division, under stress conditions, upon cell fusion in mating, and in the durable ascospore cell wall. Here we assess recent progress in understanding the molecular biology and biochemistry of cell wall synthesis and its remodeling in S. cerevisiae. We then review the regulatory dynamics of cell wall assembly, an area where functional genomics offers new insights into the integration of cell wall growth and morphogenesis with a polarized secretory system that is under cell cycle and cell type program controls. PMID:16760306

  8. Cell wall construction in Saccharomyces cerevisiae.

    PubMed

    Klis, Frans M; Boorsma, Andre; De Groot, Piet W J

    2006-02-01

    In this review, we discuss new insights in cell wall architecture and cell wall construction in the ascomycetous yeast Saccharomyces cerevisiae. Transcriptional profiling studies combined with biochemical work have provided ample evidence that the cell wall is a highly adaptable organelle. In particular, the protein population that is anchored to the stress-bearing polysaccharides of the cell wall, and forms the interface with the outside world, is highly diverse. This diversity is believed to play an important role in adaptation of the cell to environmental conditions, in growth mode and in survival. Cell wall construction is tightly controlled and strictly coordinated with progression of the cell cycle. This is reflected in the usage of specific cell wall proteins during consecutive phases of the cell cycle and in the recent discovery of a cell wall integrity checkpoint. When the cell is challenged with stress conditions that affect the cell wall, a specific transcriptional response is observed that includes the general stress response, the cell wall integrity pathway and the calcineurin pathway. This salvage mechanism includes increased expression of putative cell wall assemblases and some potential cross-linking cell wall proteins, and crucial changes in cell wall architecture. We discuss some more enzymes involved in cell wall construction and also potential inhibitors of these enzymes. Finally, we use both biochemical and genomic data to infer that the architectural principles used by S. cerevisiae to build its cell wall are also used by many other ascomycetous yeasts and also by some mycelial ascomycetous fungi.

  9. Metabolic Differences in Microbial Cell Populations Revealed by Nanophotonic Ionization

    SciTech Connect

    Walker, Bennett; Antonakos, Cory; Retterer, Scott T; Vertes, Akos

    2013-01-01

    ellular differences are linked to cell differentiation, the proliferation of cancer and to the development of drug resistance in microbial infections. Due to sensitivity limitations, however, large- scale metabolic analysis at the single cell level is only available for cells significantly larger in volume than Saccharomyces cerevisiae (~30 fL). Here we demonstrate that by a nanophotonic ionization platform and mass spectrometry, over one hundred up to 108 metabolites, or up to 18% of the known S. cerevisiae metabolome, can be identified in very small cell populations (n < 100). Under ideal conditions, r Relative quantitation of up to 4% of the metabolites is achieved at the single cell level.

  10. Exploration and comparison of inborn capacity of aerobic and anaerobic metabolisms of Saccharomyces cerevisiae for microbial electrical current production.

    PubMed

    Mao, Longfei; Verwoerd, Wynand S

    2013-01-01

    Saccharomyces cerevisiae possesses numerous advantageous biological features, such as being robust, easily handled, mostly non-pathogenic and having high catabolic rates, etc., which can be considered as merits for being used as a promising biocatalyst in microbial fuel cells (MFCs) for electricity generation. Previous studies have developed efficient MFC configurations to convert metabolic electron shuttles, such as cytoplasmic NADH, into usable electric current. However, no studies have elucidated the maximum potential of S. cerevisiae for current output and the underlying metabolic pathways, resulting from the interaction of thousands of reactions inside the cell during MFC operation. To address these two key issues, this study used in silico metabolic engineering techniques, flux balance analysis (FBA), and flux variability analysis with target flux minimization (FATMIN), to model the metabolic perturbation of S. cerevisiae under the MFC-energy extraction. The FBA results showed that, in the cytoplasmic NADH-dependent mediated electron transfer (MET) mode, S. cerevisiae had a potential to produce currents at up to 5.781 A/gDW for the anaerobic and 6.193 A/gDW for the aerobic environments. The FATMIN results showed that the aerobic and anaerobic metabolisms are resilient, relying on six and five contributing reactions respectively for high current production. Two reactions, catalyzed by glutamate dehydrogenase (NAD) (EC 1.4.1.3) and methylene tetrahydrofolate dehydrogenase (NAD) (EC 1.5.1.5), were shared in both current-production modes and contributed to over 80% of the identified maximum current outputs. It is also shown that the NADH regeneration was much less energy costly than biomass production rate. Taken together, our finding suggests that S. cerevisiae should receive more research effort for MFC electricity production.

  11. Exploration and comparison of inborn capacity of aerobic and anaerobic metabolisms of Saccharomyces cerevisiae for microbial electrical current production

    PubMed Central

    Mao, Longfei; Verwoerd, Wynand S

    2013-01-01

    Saccharomyces cerevisiae possesses numerous advantageous biological features, such as being robust, easily handled, mostly non-pathogenic and having high catabolic rates, etc., which can be considered as merits for being used as a promising biocatalyst in microbial fuel cells (MFCs) for electricity generation. Previous studies have developed efficient MFC configurations to convert metabolic electron shuttles, such as cytoplasmic NADH, into usable electric current. However, no studies have elucidated the maximum potential of S. cerevisiae for current output and the underlying metabolic pathways, resulting from the interaction of thousands of reactions inside the cell during MFC operation. To address these two key issues, this study used in silico metabolic engineering techniques, flux balance analysis (FBA), and flux variability analysis with target flux minimization (FATMIN), to model the metabolic perturbation of S. cerevisiae under the MFC-energy extraction. The FBA results showed that, in the cytoplasmic NADH-dependent mediated electron transfer (MET) mode, S. cerevisiae had a potential to produce currents at up to 5.781 A/gDW for the anaerobic and 6.193 A/gDW for the aerobic environments. The FATMIN results showed that the aerobic and anaerobic metabolisms are resilient, relying on six and five contributing reactions respectively for high current production. Two reactions, catalyzed by glutamate dehydrogenase (NAD) (EC 1.4.1.3) and methylene tetrahydrofolate dehydrogenase (NAD) (EC 1.5.1.5), were shared in both current-production modes and contributed to over 80% of the identified maximum current outputs. It is also shown that the NADH regeneration was much less energy costly than biomass production rate. Taken together, our finding suggests that S. cerevisiae should receive more research effort for MFC electricity production. PMID:23969939

  12. Identification of novel GAPDH-derived antimicrobial peptides secreted by Saccharomyces cerevisiae and involved in wine microbial interactions.

    PubMed

    Branco, Patrícia; Francisco, Diana; Chambon, Christophe; Hébraud, Michel; Arneborg, Nils; Almeida, Maria Gabriela; Caldeira, Jorge; Albergaria, Helena

    2014-01-01

    Saccharomyces cerevisiae plays a primordial role in alcoholic fermentation and has a vast worldwide application in the production of fuel-ethanol, food and beverages. The dominance of S. cerevisiae over other microbial species during alcoholic fermentations has been traditionally ascribed to its higher ethanol tolerance. However, recent studies suggested that other phenomena, such as microbial interactions mediated by killer-like toxins, might play an important role. Here we show that S. cerevisiae secretes antimicrobial peptides (AMPs) during alcoholic fermentation that are active against a wide variety of wine-related yeasts (e.g. Dekkera bruxellensis) and bacteria (e.g. Oenococcus oeni). Mass spectrometry analyses revealed that these AMPs correspond to fragments of the S. cerevisiae glyceraldehyde 3-phosphate dehydrogenase (GAPDH) protein. The involvement of GAPDH-derived peptides in wine microbial interactions was further sustained by results obtained in mixed cultures performed with S. cerevisiae single mutants deleted in each of the GAPDH codifying genes (TDH1-3) and also with a S. cerevisiae mutant deleted in the YCA1 gene, which codifies the apoptosis-involved enzyme metacaspase. These findings are discussed in the context of wine microbial interactions, biopreservation potential and the role of GAPDH in the defence system of S. cerevisiae.

  13. Applications of Microbial Cell Sensors

    NASA Astrophysics Data System (ADS)

    Shimomura-Shimizu, Mifumi; Karube, Isao

    Since the first microbial cell sensor was studied by Karube et al. in 1977, many types of microbial cell sensors have been developed as analytical tools. The microbial cell sensor utilizes microbes as a sensing element and a transducer. The characteristics of microbial cell sensors as sensing devices are a complete contrast to those of enzyme sensors or immunosensors, which are highly specific for the substrates of interest, although the specificity of the microbial cell sensor has been improved by genetic modification of the microbe used as the sensing element. Microbial cell sensors have the advantages of tolerance to measuring conditions, a long lifetime, and good cost performance, and have the disadvantage of a long response time. In this review, applications of microbial cell sensors are summarized.

  14. Glucose-based microbial production of the hormone melatonin in yeast Saccharomyces cerevisiae.

    PubMed

    Germann, Susanne M; Baallal Jacobsen, Simo A; Schneider, Konstantin; Harrison, Scott J; Jensen, Niels B; Chen, Xiao; Stahlhut, Steen G; Borodina, Irina; Luo, Hao; Zhu, Jiangfeng; Maury, Jérôme; Forster, Jochen

    2016-05-01

    Melatonin is a natural mammalian hormone that plays an important role in regulating the circadian cycle in humans. It is a clinically effective drug exhibiting positive effects as a sleep aid and a powerful antioxidant used as a dietary supplement. Commercial melatonin production is predominantly performed by complex chemical synthesis. In this study, we demonstrate microbial production of melatonin and related compounds, such as serotonin and N-acetylserotonin. We generated Saccharomyces cerevisiae strains that comprise heterologous genes encoding one or more variants of an L-tryptophan hydroxylase, a 5-hydroxy-L-tryptophan decarboxylase, a serotonin acetyltransferase, an acetylserotonin O-methyltransferase, and means for providing the cofactor tetrahydrobiopterin via heterologous biosynthesis and recycling pathways. We thereby achieved de novo melatonin biosynthesis from glucose. We furthermore accomplished increased product titers by altering expression levels of selected pathway enzymes and boosting co-factor supply. The final yeast strain produced melatonin at a titer of 14.50 ± 0.57 mg L(-1) in a 76h fermentation using simulated fed-batch medium with glucose as sole carbon source. Our study lays the basis for further developing a yeast cell factory for biological production of melatonin.

  15. Metabolic engineering of Saccharomyces cerevisiae: a key cell factory platform for future biorefineries.

    PubMed

    Hong, Kuk-Ki; Nielsen, Jens

    2012-08-01

    Metabolic engineering is the enabling science of development of efficient cell factories for the production of fuels, chemicals, pharmaceuticals, and food ingredients through microbial fermentations. The yeast Saccharomyces cerevisiae is a key cell factory already used for the production of a wide range of industrial products, and here we review ongoing work, particularly in industry, on using this organism for the production of butanol, which can be used as biofuel, and isoprenoids, which can find a wide range of applications including as pharmaceuticals and as biodiesel. We also look into how engineering of yeast can lead to improved uptake of sugars that are present in biomass hydrolyzates, and hereby allow for utilization of biomass as feedstock in the production of fuels and chemicals employing S. cerevisiae. Finally, we discuss the perspectives of how technologies from systems biology and synthetic biology can be used to advance metabolic engineering of yeast.

  16. Microbial fuel cells

    SciTech Connect

    Nealson, Kenneth H; Pirbazari, Massoud; Hsu, Lewis

    2013-04-09

    A microbial fuel cell includes an anode compartment with an anode and an anode biocatalyst and a cathode compartment with a cathode and a cathode biocatalyst, with a membrane positioned between the anode compartment and the cathode compartment, and an electrical pathway between the anode and the cathode. The anode biocatalyst is capable of catalyzing oxidation of an organic substance, and the cathode biocatalyst is capable of catalyzing reduction of an inorganic substance. The reduced organic substance can form a precipitate, thereby removing the inorganic substance from solution. In some cases, the anode biocatalyst is capable of catalyzing oxidation of an inorganic substance, and the cathode biocatalyst is capable of catalyzing reduction of an organic or inorganic substance.

  17. Identification of Two Saccharomyces cerevisiae Cell Wall Mannan Chemotypes

    PubMed Central

    Cawley, T. N.; Ballou, Clinton E.

    1972-01-01

    We have obtained evidence for two structurally and antigenically different Saccharomyces cerevisiae cell wall mannans. One, which occurs widely and is found in S. cerevisiae strain 238C, is already known to be a neutral mannan which yields mannose, mannobiose, mannotriose, and mannotetraose on acetolysis of the (1 → 6)-linked backbone. The other, which was found in S. cerevisiae brewer's strains, is a phosphomannan with a structure very similar to that of Kloeckera brevis mannan. S. cerevisiae (brewer's yeast strain) was agglutinated by antiserum prepared against Kloeckera brevis cells. The mannan, isolated from a proteolytic digest of the cell wall of the former, did not react with S. cerevisiae 238C antiserum, whereas it cross-reacted strongly with K. brevis antiserum. Controlled acetolysis cleaved the (1 → 6)-linkages in the polysaccharide backbone and released mannose, mannobiose, mannotriose, and mannotriose phosphate. Mild acid treatment of the phosphomannan hydrolyzed the phosphodiester linkage, yielding phosphomonoester mannan and mannose. The resulting phosphomonoester mannan reacted with antiserum prepared against K. brevis possessing monoester phosphate groups on the cell surface. α-d-Mannose-1-phosphate completely inhibited the precipitin reaction between brewer's yeast mannan and the homologous antiserum. Flocculent and nonflocculent strains of this yeast were shown to have similar structural and immunological properties. PMID:4559821

  18. Microbial Fuel Cells and Microbial Electrolyzers

    SciTech Connect

    Borole, Abhijeet P

    2015-01-01

    Microbial Fuel Cells and microbial electrolyzers represent an upcoming technology for production of electricity and hydrogen using a hybrid electrocatalytic-biocatalytic approach. The combined catalytic efficiency of these processes has potential to make this technology highly efficient among the various renewable energy production alternatives. This field has attracted electrochemists, biologists and many other disciplines due to its potential to contribute to the energy, water and environment sectors. A brief introduction to the technology is provided followed by current research needs from a bioelectrochemical perspective. Insights into the operation and limitations of these systems achieved via cyclic voltammetry and impedance spectroscopy are discussed along with the power management needs to develop the application aspects. Besides energy production, other potential applications in bioenergy, bioelectronics, chemical production and remediation are also highlighted.

  19. Evaluation of microbial qPCR workflows using engineered Saccharomyces cerevisiae

    PubMed Central

    Da Silva, S.M.; Vang, L.K.; Olson, N.D.; Lund, S.P.; Downey, A.S.; Kelman, Z.; Salit, M.L.; Lin, N.J.; Morrow, J.B.

    2016-01-01

    Aims We describe the development and interlaboratory study of modified Saccharomyces cerevisiae as a candidate material to evaluate a full detection workflow including DNA extraction and quantitative polymerase chain reaction (qPCR). Methods and results S. cerevisiae NE095 was prepared by stable insertion of DNA sequence External RNA Control Consortium-00095 into S. cerevisiae BY4739 to convey selectivity. For the interlaboratory study, a binomial regression model was used to select three cell concentrations, high (4 × 107 cells ml−1), intermediate (4 × 105 cells ml−1) and low (4 × 103 cells ml−1), and the number of samples per concentration. Seven participants, including potential end users, had combined rates of positive qPCR detection (quantification cycle <37) of 100%, 40%, and 0% for high, intermediate, and low concentrations, respectively. Conclusions The NE095 strain was successfully detected by all participants, with the high concentration indicating a potential target concentration for a reference material. Significance and impact of the study The engineered yeast has potential to support measurement assurance for the analytical process of qPCR, encompassing the method, equipment, and operator, to increase confidence in results and better inform decision-making in areas of applied microbiology. This material can also support process assessment for other DNA-based detection technologies. PMID:27077050

  20. A novel process-based model of microbial growth: self-inhibition in Saccharomyces cerevisiae aerobic fed-batch cultures.

    PubMed

    Mazzoleni, Stefano; Landi, Carmine; Cartenì, Fabrizio; de Alteriis, Elisabetta; Giannino, Francesco; Paciello, Lucia; Parascandola, Palma

    2015-07-30

    Microbial population dynamics in bioreactors depend on both nutrients availability and changes in the growth environment. Research is still ongoing on the optimization of bioreactor yields focusing on the increase of the maximum achievable cell density. A new process-based model is proposed to describe the aerobic growth of Saccharomyces cerevisiae cultured on glucose as carbon and energy source. The model considers the main metabolic routes of glucose assimilation (fermentation to ethanol and respiration) and the occurrence of inhibition due to the accumulation of both ethanol and other self-produced toxic compounds in the medium. Model simulations reproduced data from classic and new experiments of yeast growth in batch and fed-batch cultures. Model and experimental results showed that the growth decline observed in prolonged fed-batch cultures had to be ascribed to self-produced inhibitory compounds other than ethanol. The presented results clarify the dynamics of microbial growth under different feeding conditions and highlight the relevance of the negative feedback by self-produced inhibitory compounds on the maximum cell densities achieved in a bioreactor.

  1. Microbial Fuel Cells and Sensors

    DTIC Science & Technology

    2007-11-02

    funding foreign research over Quality U.S. research needs to be investigated by government officials. PATENT INFORMATION: Improved fuel cell designs and...Zeikus. Analysis of microbial electrochemical activity in marine sediment. (In preparation) REPOT D CUM NTA ON AGEForm Approved REPOT D CUM NTATON

  2. The microbial cell cycle

    SciTech Connect

    Nurse, P.; Streiblova, E.

    1984-01-01

    This book concentrates on the major problems of cell cycle control in microorganisms. A wide variety of microorganisms, ranging from bacteria and yeasts to hyphal fungi, algae, and ciliates are analyzed, with emphasis on the basic similarities among the organisms. Different ways of looking at cell cycle control which emphasize aspects of the problem such as circadian rhythms, limit cycle oscillators, and cell size models, are considered. New approaches such as the study of cell cycle mutants, and cloning of cell cycle control genes are also presented.

  3. Indentation with atomic force microscope, Saccharomyces cerevisiae cell gains elasticity under ethanol stress.

    PubMed

    Niu, Yuan-Pu; Lin, Xiang-Hua; Dong, Shi-Jun; Yuan, Qi-Peng; Li, Hao

    2016-10-01

    During bioethanol fermentation process, Saccharomyces cerevisiae cell membrane is the first target to be attacked by the accumulated ethanol. In such a prominent position, S. cerevisiae cell membrane could reversely provide protection through changing fluidity or elasticity secondary to remodeled membrane components or structure during the fermentation process. However, there is yet to be a direct observation of the real effect of the membrane compositional change. In this study, atomic force microscope-based strategy was performed to determine Young's modulus of S. cerevisiae to directly clarify ethanol stress-associated changes and roles of S. cerevisiae cell membrane fluidity and elasticity. Cell survival rate decreased while the cell swelling rate and membrane permeability increased as ethanol concentration increased from 0% to 20% v/v. Young's modulus decreased continuously from 3.76MPa to 1.53MPa while ethanol stress increased from 0% to 20% v/v, indicating that ethanol stress induced the S. cerevisiae membrane fluidity and elasticity changes. Combined with the fact that membrane composition varies under ethanol stress, to some extent, this could be considered as a forced defensive act to the ethanol stress by S. cerevisiae cells. On the other hand, the ethanol stress induced loosening of cell membrane also caused S. cerevisiae cell to proactively remodel membrane to make cell membrane more agreeable to the increase of environmental threat. Increased ethanol stress made S. cerevisiae cell membrane more fluidized and elastic, and eventually further facilitated yeast cell's survival. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Symmetric cell division in pseudohyphae of the yeast Saccharomyces cerevisiae.

    PubMed Central

    Kron, S J; Styles, C A; Fink, G R

    1994-01-01

    Laboratory strains of Saccharomyces cerevisiae are dimorphic; in response to nitrogen starvation they switch from a yeast form (YF) to a filamentous pseudohyphal (PH) form. Time-lapse video microscopy of dividing cells reveals that YF and PH cells differ in their cell cycles and budding polarity. The YF cell cycle is controlled at the G1/S transition by the cell-size checkpoint Start. YF cells divide asymmetrically, producing small daughters from full-sized mothers. As a result, mothers and daughters bud asynchronously. Mothers bud immediately but daughters grow in G1 until they achieve a critical cell size. By contrast, PH cells divide symmetrically, restricting mitosis until the bud grows to the size of the mother. Thus, mother and daughter bud synchronously in the next cycle, without a G1 delay before Start. YF and PH cells also exhibit distinct bud-site selection patterns. YF cells are bipolar, producing their second and subsequent buds at either pole. PH cells are unipolar, producing their second and subsequent buds only from the end opposite the junction with their mother. We propose that in PH cells a G2 cell-size checkpoint delays mitosis until bud size reaches that of the mother cell. We conclude that yeast and PH forms are distinct cell types each with a unique cell cycle, budding pattern, and cell shape. Images PMID:7841518

  5. Microbial transformations of ferulic acid by Saccharomyces cerevisiae and Pseudomonas fluorescens.

    PubMed Central

    Huang, Z; Dostal, L; Rosazza, J P

    1993-01-01

    Saccharomyces cerevisiae (dry baker's yeast) and Pseudomonas fluorescens were used to convert trans-ferulic acid into 4-hydroxy-3-methoxystyrene in 96 and 89% yields, respectively. The metabolites were isolated by solid-phase extraction and analyzed by thin-layer chromatography and high-performance liquid chromatography. The identities of the metabolites were determined by 1H- and 13C-nuclear magnetic resonance spectroscopy and by mass spectrometry. The mechanism of the decarboxylation of ferulic acid was investigated by measuring the degree and position of deuterium incorporated into the styrene derivative from D2O by mass spectrometry and by both proton and deuterium nuclear magnetic resonance spectroscopies. Resting cells of baker's yeast reduced ferulic acid to 4-hydroxy-3-methoxyphenylpropionic acid in 54% yield when incubations were under an argon atmosphere. PMID:8395165

  6. Towards a Microbial Thermoelectric Cell

    PubMed Central

    Rodríguez-Barreiro, Raúl; Abendroth, Christian; Vilanova, Cristina; Moya, Andrés; Porcar, Manuel

    2013-01-01

    Microbial growth is an exothermic process. Biotechnological industries produce large amounts of heat, usually considered an undesirable by-product. In this work, we report the construction and characterization of the first microbial thermoelectric cell (MTC), in which the metabolic heat produced by a thermally insulated microbial culture is partially converted into electricity through a thermoelectric device optimized for low ΔT values. A temperature of 41°C and net electric voltage of around 250–600 mV was achieved with 1.7 L baker’s yeast culture. This is the first time microbial metabolic energy has been converted into electricity with an ad hoc thermoelectric device. These results might contribute towards developing a novel strategy to harvest excess heat in the biotechnology industry, in processes such as ethanol fermentation, auto thermal aerobic digestion (ATAD) or bioremediation, which could be coupled with MTCs in a single unit to produce electricity as a valuable by-product of the primary biotechnological product. Additionally, we propose that small portable MTCs could be conceived and inoculated with suitable thermophilic of hyperthermophilic starter cultures and used for powering small electric devices. PMID:23468862

  7. Immobilized cell cross-flow reactor. [Saccharomyces cerevisiae

    SciTech Connect

    Chotani, G.K.; Constantinides, A.

    1984-01-01

    A cross-current flow reactor was operated using sodium alginate gel entrapped yeast cells (Saccharomyces cerevisiae) under growth conditions. Micron-sized silica, incorporated into the biocatalyst particles (1 mm mean diameter) improved mechanical strength and internal surface adhesion. The process showed decreased productivity and stability at 35/sup 0/C compared to the normal study done at 30/sup 0/C. The increased number of cross flows diminish the product inhibition effect. The residence time distribution shows that the cross-flow bioreactor system can be approximated to either a train of backmixed fermentors in series or a plug flow fermentor with moderate axial dispersion.

  8. Photosynthetic Microbial Fuel Cells.

    PubMed

    Laureanti, Joseph A; Jones, Anne K

    2017-01-10

    This chapter presents the current state of research on bioelectrochemical systems that include phototrophic organisms. First, we describe what is known of how phototrophs transfer electrons from internal metabolism to external substrates. This includes efforts to understand both the source of electrons and transfer pathways within cells. Second, we consider technological progress toward producing bio-photovoltaic devices with phototrophs. Efforts to improve these devices by changing the species included, the electrode surfaces, and chemical mediators are described. Finally, we consider future directions for this research field.

  9. Yeast surface display of dehydrogenases in microbial fuel-cells.

    PubMed

    Gal, Idan; Schlesinger, Orr; Amir, Liron; Alfonta, Lital

    2016-12-01

    Two dehydrogenases, cellobiose dehydrogenase from Corynascus thermophilus and pyranose dehydrogenase from Agaricus meleagris, were displayed for the first time on the surface of Saccharomyces cerevisiae using the yeast surface display system. Surface displayed dehydrogenases were used in a microbial fuel cell and generated high power outputs. Surface displayed cellobiose dehydrogenase has demonstrated a midpoint potential of -28mV (vs. Ag/AgCl) at pH=6.5 and was used in a mediator-less anode compartment of a microbial fuel cell producing a power output of 3.3μWcm(-2) using lactose as fuel. Surface-displayed pyranose dehydrogenase was used in a microbial fuel cell and generated high power outputs using different substrates, the highest power output that was achieved was 3.9μWcm(-2) using d-xylose. These results demonstrate that surface displayed cellobiose dehydrogenase and pyranose dehydrogenase may successfully be used in microbial bioelectrochemical systems. Copyright © 2016 Elsevier B.V. All rights reserved.

  10. Proteome analysis of aerobically and anaerobically grown Saccharomyces cerevisiae cells.

    PubMed

    Bruckmann, Astrid; Hensbergen, Paul J; Balog, Crina I A; Deelder, André M; Brandt, Raymond; Snoek, I S Ishtar; Steensma, H Yde; van Heusden, G Paul H

    2009-01-30

    The yeast Saccharomyces cerevisiae is able to grow under aerobic as well as anaerobic conditions. We and others previously found that transcription levels of approximately 500 genes differed more than two-fold when cells from anaerobic and aerobic conditions were compared. Here, we addressed the effect of anaerobic growth at the post-transcriptional level by comparing the proteomes of cells isolated from steady-state glucose-limited anaerobic and aerobic cultures. Following two-dimensional gel electrophoresis and mass spectrometry we identified 110 protein spots, corresponding to 75 unique proteins, of which the levels differed more than two-fold between aerobically and anaerobically-grown cells. For 21 of the 110 spots, the intensities decreased more than two-fold whereas the corresponding mRNA levels increased or did not change significantly under anaerobic conditions. The intensities of the other 89 spots changed in the same direction as the mRNA levels of the corresponding genes, although to different extents. For some genes of glycolysis a small increase in mRNA levels, 1.5-2 fold, corresponded to a 5-10 fold increase in protein levels. Extrapolation of our results suggests that transcriptional regulation is the major but not exclusive mechanism for adaptation of S. cerevisiae to anaerobic growth conditions.

  11. Cell Wall β-(1,6)-Glucan of Saccharomyces cerevisiae

    PubMed Central

    Aimanianda, Vishukumar; Clavaud, Cécile; Simenel, Catherine; Fontaine, Thierry; Delepierre, Muriel; Latgé, Jean-Paul

    2009-01-01

    Despite its essential role in the yeast cell wall, the exact composition of the β-(1,6)-glucan component is not well characterized. While solubilizing the cell wall alkali-insoluble fraction from a wild type strain of Saccharomyces cerevisiae using a recombinant β-(1,3)-glucanase followed by chromatographic characterization of the digest on an anion exchange column, we observed a soluble polymer that eluted at the end of the solvent gradient run. Further characterization indicated this soluble polymer to have a molecular mass of ∼38 kDa and could be hydrolyzed only by β-(1,6)-glucanase. Gas chromatographymass spectrometry and NMR (1H and 13C) analyses confirmed it to be a β-(1,6)-glucan polymer with, on average, branching at every fifth residue with one or two β-(1,3)-linked glucose units in the side chain. This polymer peak was significantly reduced in the corresponding digests from mutants of the kre genes (kre9 and kre5) that are known to play a crucial role in the β-(1,6)-glucan biosynthesis. In the current study, we have developed a biochemical assay wherein incubation of UDP-[14C]glucose with permeabilized S. cerevisiae yeasts resulted in the synthesis of a polymer chemically identical to the branched β-(1,6)-glucan isolated from the cell wall. Using this assay, parameters essential for β-(1,6)-glucan synthetic activity were defined. PMID:19279004

  12. Identification of new cell size control genes in S. cerevisiae

    PubMed Central

    2012-01-01

    Cell size homeostasis is a conserved attribute in many eukaryotic species involving a tight regulation between the processes of growth and proliferation. In budding yeast S. cerevisiae, growth to a “critical cell size” must be achieved before a cell can progress past START and commit to cell division. Numerous studies have shown that progression past START is actively regulated by cell size control genes, many of which have implications in cell cycle control and cancer. Two initial screens identified genes that strongly modulate cell size in yeast. Since a second generation yeast gene knockout collection has been generated, we screened an additional 779 yeast knockouts containing 435 new ORFs (~7% of the yeast genome) to supplement previous cell size screens. Upon completion, 10 new strong size mutants were identified: nine in log-phase cells and one in saturation-phase cells, and 97% of the yeast genome has now been screened for cell size mutations. The majority of the logarithmic phase size mutants have functions associated with translation further implicating the central role of growth control in the cell division process. Genetic analyses suggest ECM9 is directly associated with the START transition. Further, the small (whi) mutants mrpl49Δ and cbs1Δ are dependent on CLN3 for cell size effects. In depth analyses of new size mutants may facilitate a better understanding of the processes that govern cell size homeostasis. PMID:23234503

  13. A flow injection analysis system with encapsulated high-density Saccharomyces cerevisiae cells for rapid determination of biochemical oxygen demand.

    PubMed

    Seo, Kyo Seong; Choo, Kwang Ho; Chang, Ho Nam; Park, Joong Kon

    2009-05-01

    The biochemical oxygen demand (BOD) determination was studied using a novel flow injection analysis (FIA) system with encapsulated Saccharomyces cerevisiae cells and an oxygen electrode and was compared with conventional 5-day BOD tests. S. cerevisiae cells were packed in a calcium alginate capsule at a dry cell weight of 250 g/l of capsule core. The level of dissolved oxygen (DO) was reduced due to the enhanced respiratory activity of the microbial cells when the injected nutrient passed through the bioreactor. The decrease in DO (DeltaDO) was intensified with the amount of microbial cells packed in the bioreactor. However, the specific DeltaDO decreased as the amount of cells loaded in the bioreactor increased. The DeltaDO value was dependent on the pH and temperature of the mobile phase and reached its maximum value at 35 degrees C and pH 7-8. Also, DeltaDO became larger at longer response times as the flow rate of the mobile phase decreased. The measurement of DeltaDO was repeated more than six times consecutively using a 20-ppm standard glucose and glutamic acid solution, which confirmed the reproducibility with a standard deviation of 0.95%. A strong linear correlation between DeltaDO and BOD was also observed. The 5-day BOD values of actual water and wastewater samples were in accordance with the BOD values obtained by this FIA method using encapsulated S. cerevisiae cells. Unlike the cell-immobilized bead system, there was no contamination of the bioreactor resulting from any leak of yeast cells from the sensor capsules during BOD measurements.

  14. Dynamics of cell wall structure in Saccharomyces cerevisiae.

    PubMed

    Klis, Frans M; Mol, Pieternella; Hellingwerf, Klaas; Brul, Stanley

    2002-08-01

    The cell wall of Saccharomyces cerevisiae is an elastic structure that provides osmotic and physical protection and determines the shape of the cell. The inner layer of the wall is largely responsible for the mechanical strength of the wall and also provides the attachment sites for the proteins that form the outer layer of the wall. Here we find among others the sexual agglutinins and the flocculins. The outer protein layer also limits the permeability of the cell wall, thus shielding the plasma membrane from attack by foreign enzymes and membrane-perturbing compounds. The main features of the molecular organization of the yeast cell wall are now known. Importantly, the molecular composition and organization of the cell wall may vary considerably. For example, the incorporation of many cell wall proteins is temporally and spatially controlled and depends strongly on environmental conditions. Similarly, the formation of specific cell wall protein-polysaccharide complexes is strongly affected by external conditions. This points to a tight regulation of cell wall construction. Indeed, all five mitogen-activated protein kinase pathways in bakers' yeast affect the cell wall, and additional cell wall-related signaling routes have been identified. Finally, some potential targets for new antifungal compounds related to cell wall construction are discussed.

  15. Production of recombinant Agaricus bisporus tyrosinase in Saccharomyces cerevisiae cells.

    PubMed

    Lezzi, Chiara; Bleve, Gianluca; Spagnolo, Stefano; Perrotta, Carla; Grieco, Francesco

    2012-12-01

    It has been demonstrated that Agaricus bisporus tyrosinase is able to oxidize various phenolic compounds, thus being an enzyme of great importance for a number of biotechnological applications. The tyrosinase-coding PPO2 gene was isolated by reverse-transcription polymerase chain reaction (RT-PCR) using total RNA extracted from the mushroom fruit bodies as template. The gene was sequenced and cloned into pYES2 plasmid, and the resulting pY-PPO2 recombinant vector was then used to transform Saccharomyces cerevisiae cells. Native polyacrylamide gel electrophoresis followed by enzymatic activity staining with L-3,4-dihydroxyphenylalanine (L-DOPA) indicated that the recombinant tyrosinase is biologically active. The recombinant enzyme was overexpressed and biochemically characterized, showing that the catalytic constants of the recombinant tyrosinase were higher than those obtained when a commercial tyrosinase was used, for all the tested substrates. The present study describes the recombinant production of A. bisporus tyrosinase in active form. The produced enzyme has similar properties to the one produced in the native A. bisporus host, and its expression in S. cerevisiae provides good potential for protein engineering and functional studies of this important enzyme.

  16. Industrial systems biology of Saccharomyces cerevisiae enables novel succinic acid cell factory.

    PubMed

    Otero, José Manuel; Cimini, Donatella; Patil, Kiran R; Poulsen, Simon G; Olsson, Lisbeth; Nielsen, Jens

    2013-01-01

    Saccharomyces cerevisiae is the most well characterized eukaryote, the preferred microbial cell factory for the largest industrial biotechnology product (bioethanol), and a robust commerically compatible scaffold to be exploitted for diverse chemical production. Succinic acid is a highly sought after added-value chemical for which there is no native pre-disposition for production and accmulation in S. cerevisiae. The genome-scale metabolic network reconstruction of S. cerevisiae enabled in silico gene deletion predictions using an evolutionary programming method to couple biomass and succinate production. Glycine and serine, both essential amino acids required for biomass formation, are formed from both glycolytic and TCA cycle intermediates. Succinate formation results from the isocitrate lyase catalyzed conversion of isocitrate, and from the α-keto-glutarate dehydrogenase catalyzed conversion of α-keto-glutarate. Succinate is subsequently depleted by the succinate dehydrogenase complex. The metabolic engineering strategy identified included deletion of the primary succinate consuming reaction, Sdh3p, and interruption of glycolysis derived serine by deletion of 3-phosphoglycerate dehydrogenase, Ser3p/Ser33p. Pursuing these targets, a multi-gene deletion strain was constructed, and directed evolution with selection used to identify a succinate producing mutant. Physiological characterization coupled with integrated data analysis of transcriptome data in the metabolically engineered strain were used to identify 2(nd)-round metabolic engineering targets. The resulting strain represents a 30-fold improvement in succinate titer, and a 43-fold improvement in succinate yield on biomass, with only a 2.8-fold decrease in the specific growth rate compared to the reference strain. Intuitive genetic targets for either over-expression or interruption of succinate producing or consuming pathways, respectively, do not lead to increased succinate. Rather, we demonstrate how

  17. Industrial Systems Biology of Saccharomyces cerevisiae Enables Novel Succinic Acid Cell Factory

    PubMed Central

    Otero, José Manuel; Cimini, Donatella; Patil, Kiran R.; Poulsen, Simon G.; Olsson, Lisbeth; Nielsen, Jens

    2013-01-01

    Saccharomyces cerevisiae is the most well characterized eukaryote, the preferred microbial cell factory for the largest industrial biotechnology product (bioethanol), and a robust commerically compatible scaffold to be exploitted for diverse chemical production. Succinic acid is a highly sought after added-value chemical for which there is no native pre-disposition for production and accmulation in S. cerevisiae. The genome-scale metabolic network reconstruction of S. cerevisiae enabled in silico gene deletion predictions using an evolutionary programming method to couple biomass and succinate production. Glycine and serine, both essential amino acids required for biomass formation, are formed from both glycolytic and TCA cycle intermediates. Succinate formation results from the isocitrate lyase catalyzed conversion of isocitrate, and from the α-keto-glutarate dehydrogenase catalyzed conversion of α-keto-glutarate. Succinate is subsequently depleted by the succinate dehydrogenase complex. The metabolic engineering strategy identified included deletion of the primary succinate consuming reaction, Sdh3p, and interruption of glycolysis derived serine by deletion of 3-phosphoglycerate dehydrogenase, Ser3p/Ser33p. Pursuing these targets, a multi-gene deletion strain was constructed, and directed evolution with selection used to identify a succinate producing mutant. Physiological characterization coupled with integrated data analysis of transcriptome data in the metabolically engineered strain were used to identify 2nd-round metabolic engineering targets. The resulting strain represents a 30-fold improvement in succinate titer, and a 43-fold improvement in succinate yield on biomass, with only a 2.8-fold decrease in the specific growth rate compared to the reference strain. Intuitive genetic targets for either over-expression or interruption of succinate producing or consuming pathways, respectively, do not lead to increased succinate. Rather, we demonstrate how

  18. Carbon nanotube dispersed conductive network for microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Matsumoto, S.; Yamanaka, K.; Ogikubo, H.; Akasaka, H.; Ohtake, N.

    2014-08-01

    Microbial fuel cells (MFCs) are promising devices for capturing biomass energy. Although they have recently attracted considerable attention, their power densities are too low for practical use. Increasing their electrode surface area is a key factor for improving the performance of MFC. Carbon nanotubes (CNTs), which have excellent electrical conductivity and extremely high specific surface area, are promising materials for electrodes. However, CNTs are insoluble in aqueous solution because of their strong intertube van der Waals interactions, which make practical use of CNTs difficult. In this study, we revealed that CNTs have a strong interaction with Saccharomyces cerevisiae cells. CNTs attach to the cells and are dispersed in a mixture of water and S. cerevisiae, forming a three-dimensional CNT conductive network. Compared with a conventional two-dimensional electrode, such as carbon paper, the three-dimensional conductive network has a much larger surface area. By applying this conductive network to MFCs as an anode electrode, power density is increased to 176 μW/cm2, which is approximately 25-fold higher than that in the case without CNTs addition. Maximum current density is also increased to approximately 8-fold higher. These results suggest that three-dimensional CNT conductive network contributes to improve the performance of MFC by increasing surface area.

  19. Microbial electrolysis cell with a microbial biocathode.

    PubMed

    Jeremiasse, Adriaan W; Hamelers, Hubertus V M; Buisman, Cees J N

    2010-04-01

    This study demonstrates, for the first time, the proof-of-principle of an MEC in which both the anodic and cathodic reaction are catalyzed by microorganisms. No expensive chemical catalysts, such as platinum, are needed. Two of these MECs were simultaneously operated and reached a maximum of 1.4 A/m(2) at an applied cell voltage of 0.5 V. At a cathode potential of -0.7 V, the biocathode in the MECs had a higher current density (MEC 1: 1.9 A/m(2), MEC 2: 3.3 A/m(2)) than a control cathode (0.3 A/m(2), graphite felt without biofilm) in an electrochemical half cell. This indicates that hydrogen production is catalyzed at the biocathode, likely by electrochemically active microorganisms. The cathodic hydrogen recovery was 17% for MEC 1 and 21% for MEC 2. Hydrogen losses were ascribed to diffusion through membrane and tubing, and methane formation. After 1600 h of operation, the current density of the MECs had decreased to 0.6 A/m(2), probably caused by precipitation of calcium phosphate on the biocathode. The slow deteriorating effect of calcium phosphate, and the production of methane show the importance of studying the combination of bioanode and biocathode in one electrochemical cell, and of studying long term performance of such an MEC.

  20. Hydrogen peroxide removal with magnetically responsive Saccharomyces cerevisiae cells.

    PubMed

    Safarik, Ivo; Sabatkova, Zdenka; Safarikova, Mirka

    2008-09-10

    Hydrogen peroxide (HP) is a promising chemical sanitizer for use in the food industry. Its residues have to be decomposed, usually using an enzyme process employing catalase. In order to offer an inexpensive biocatalyst and to simplify subsequent manipulation, we have prepared magnetically responsive alginate beads containing entrapped Saccharomyces cerevisiae cells and magnetite microparticles. Larger beads (2-3 mm in diameter) were prepared by dropping the mixture into calcium chloride solution, while microbeads (the diameter of majority of particles ranged between 50 and 100 microm) were prepared using the water in oil emulsification process. In general, microbeads enabled more efficient HP decomposition. The prepared microparticulate biocatalyst caused efficient decomposition of HP in water solutions (up to 2% concentration), leaving very low residual HP concentration after treatment (below 0.001% under appropriate conditions). The biocatalyst was stable; the same catalytic activity was observed after one month storage at 4 degrees C, and the microbeads could be used at least five times.

  1. Architecture and Biosynthesis of the Saccharomyces cerevisiae Cell Wall

    PubMed Central

    Orlean, Peter

    2012-01-01

    The wall gives a Saccharomyces cerevisiae cell its osmotic integrity; defines cell shape during budding growth, mating, sporulation, and pseudohypha formation; and presents adhesive glycoproteins to other yeast cells. The wall consists of β1,3- and β1,6-glucans, a small amount of chitin, and many different proteins that may bear N- and O-linked glycans and a glycolipid anchor. These components become cross-linked in various ways to form higher-order complexes. Wall composition and degree of cross-linking vary during growth and development and change in response to cell wall stress. This article reviews wall biogenesis in vegetative cells, covering the structure of wall components and how they are cross-linked; the biosynthesis of N- and O-linked glycans, glycosylphosphatidylinositol membrane anchors, β1,3- and β1,6-linked glucans, and chitin; the reactions that cross-link wall components; and the possible functions of enzymatic and nonenzymatic cell wall proteins. PMID:23135325

  2. Calcium signaling and copper toxicity in Saccharomyces cerevisiae cells.

    PubMed

    Ruta, Lavinia L; Popa, Claudia V; Nicolau, Ioana; Farcasanu, Ileana C

    2016-12-01

    To respond to metal surpluses, cells have developed intricate ways of defense against the excessive metallic ions. To understand the ways in which cells sense the presence of toxic concentration in the environment, the role of Ca(2+) in mediating the cell response to high Cu(2+) was investigated in Saccharomyces cerevisiae cells. It was found that the cell exposure to high Cu(2+) was accompanied by elevations in cytosolic Ca(2+) with patterns that were influenced not only by Cu(2+) concentration but also by the oxidative state of the cell. When Ca(2+) channel deletion mutants were used, it was revealed that the main contributor to the cytosolic Ca(2+) pool under Cu(2+) stress was the vacuolar Ca(2+) channel, Yvc1, also activated by the Cch1-mediated Ca(2+) influx. Using yeast mutants defective in the Cu(2+) transport across the plasma membrane, it was found that the Cu(2+)-dependent Ca(2+) elevation could correlate not only with the accumulated metal, but also with the overall oxidative status. Moreover, it was revealed that Cu(2+) and H2O2 acted in synergy to induce Ca(2+)-mediated responses to external stress.

  3. Microbial fuel cells: novel microbial physiologies and engineering approaches.

    PubMed

    Lovley, Derek R

    2006-06-01

    The possibility of generating electricity with microbial fuel cells has been recognized for some time, but practical applications have been slow to develop. The recent development of a microbial fuel cell that can harvest electricity from the organic matter stored in marine sediments has demonstrated the feasibility of producing useful amounts of electricity in remote environments. Further study of these systems has led to the discovery of microorganisms that conserve energy to support their growth by completely oxidizing organic compounds to carbon dioxide with direct electron transfer to electrodes. This suggests that self-sustaining microbial fuel cells that can effectively convert a diverse range of waste organic matter or renewable biomass to electricity are feasible. Significant progress has recently been made to increase the power output of systems designed to convert organic wastes to electricity, but substantial additional optimization will be required for large-scale electricity production.

  4. Ethanol fermentation in an immobilized cell reactor using Saccharomyces cerevisiae.

    PubMed

    Najafpour, Ghasem; Younesi, Habibollah; Syahidah Ku Ismail, Ku

    2004-05-01

    Fermentation of sugar by Saccharomyces cerevisiae, for production of ethanol in an immobilized cell reactor (ICR) was successfully carried out to improve the performance of the fermentation process. The fermentation set-up was comprised of a column packed with beads of immobilized cells. The immobilization of S. cerevisiae was simply performed by the enriched cells cultured media harvested at exponential growth phase. The fixed cell loaded ICR was carried out at initial stage of operation and the cell was entrapped by calcium alginate. The production of ethanol was steady after 24 h of operation. The concentration of ethanol was affected by the media flow rates and residence time distribution from 2 to 7 h. In addition, batch fermentation was carried out with 50 g/l glucose concentration. Subsequently, the ethanol productions and the reactor productivities of batch fermentation and immobilized cells were compared. In batch fermentation, sugar consumption and ethanol production obtained were 99.6% and 12.5% v/v after 27 h while in the ICR, 88.2% and 16.7% v/v were obtained with 6 h retention time. Nearly 5% ethanol production was achieved with high glucose concentration (150 g/l) at 6 h retention time. A yield of 38% was obtained with 150 g/l glucose. The yield was improved approximately 27% on ICR and a 24 h fermentation time was reduced to 7 h. The cell growth rate was based on the Monod rate equation. The kinetic constants (K(s) and mu(m)) of batch fermentation were 2.3 g/l and 0.35 g/lh, respectively. The maximum yield of biomass on substrate (Y(X-S)) and the maximum yield of product on substrate (Y(P-S)) in batch fermentations were 50.8% and 31.2% respectively. Productivity of the ICR were 1.3, 2.3, and 2.8 g/lh for 25, 35, 50 g/l of glucose concentration, respectively. The productivity of ethanol in batch fermentation with 50 g/l glucose was calculated as 0.29 g/lh. Maximum production of ethanol in ICR when compared to batch reactor has shown to increase

  5. Molecular basis of cell integrity and morphogenesis in Saccharomyces cerevisiae.

    PubMed Central

    Cid, V J; Durán, A; del Rey, F; Snyder, M P; Nombela, C; Sánchez, M

    1995-01-01

    In fungi and many other organisms, a thick outer cell wall is responsible for determining the shape of the cell and for maintaining its integrity. The budding yeast Saccharomyces cerevisiae has been a useful model organism for the study of cell wall synthesis, and over the past few decades, many aspects of the composition, structure, and enzymology of the cell wall have been elucidated. The cell wall of budding yeasts is a complex and dynamic structure; its arrangement alters as the cell grows, and its composition changes in response to different environmental conditions and at different times during the yeast life cycle. In the past few years, we have witnessed a profilic genetic and molecular characterization of some key aspects of cell wall polymer synthesis and hydrolysis in the budding yeast. Furthermore, this organism has been the target of numerous recent studies on the topic of morphogenesis, which have had an enormous impact on our understanding of the intracellular events that participate in directed cell wall synthesis. A number of components that direct polarized secretion, including those involved in assembly and organization of the actin cytoskeleton, secretory pathways, and a series of novel signal transduction systems and regulatory components have been identified. Analysis of these different components has suggested pathways by which polarized secretion is directed and controlled. Our aim is to offer an overall view of the current understanding of cell wall dynamics and of the complex network that controls polarized growth at particular stages of the budding yeast cell cycle and life cycle. PMID:7565410

  6. Effect of beta-cyclodextrin on production of L-phenylacetyl carbinol by immobilized cells of Saccharomyces cerevisiae.

    PubMed

    Mahmoud, W M; El-Sayed, A H; Coughlin, R W

    1990-07-01

    The rate and extent of microbial transformation of higher concentrations of benzaldehyde substrate to L-phenylacetyl carbinol (L-PAC) by immobilized cells of Saccharomyces cerevisiae ATCC 834 was markedly stimulated by addition of different concentrations of beta-cyclodextrin (BCD) to the fermentation medium. With 0.5, 1.0, and 1.5% BCD in the fermentation medium and cumulative doses of benzaldehyde of 12 and 14 g/L, significantly higher yields of L-PAC were obtained, about one- to twofold that of the yields of the control experiments. The favorable effects of BCD were evident in spite of its presence in stoichiometric concentrations significantly lower than those of benzaldehyde. The presence of BCD also appeared to stimulate microbial growth slightly. Enhanced cellular activity was reflected by faster D-glucose consumption and faster benzaldehyde utilization in the presence of BCD.

  7. Cell cycle regulation of homologous recombination in Saccharomyces cerevisiae.

    PubMed

    Mathiasen, David P; Lisby, Michael

    2014-03-01

    Homologous recombination (HR) contributes to maintaining genome integrity by facilitating error-free repair of DNA double-strand breaks (DSBs) primarily during the S and G2 phases of the mitotic cell cycle, while nonhomologous end joining (NHEJ) is the preferred pathway for DSB repair in G1 phase. The decision to repair a DSB by NHEJ or HR is made primarily at the level of DSB end resection, which is inhibited by the Ku complex in G1 and promoted by the Sae2 and Mre11 nucleases in S/G2 . The cell cycle regulation of HR is accomplished both at the transcription level and at the protein level through post-translational modification, degradation and subcellular localization. Cyclin-dependent kinase Cdc28 plays an established key role in these events, while the role of transcriptional regulation and protein degradation are less well understood. Here, the cell cycle regulatory mechanisms for mitotic HR in Saccharomyces cerevisiae are reviewed, and evolutionarily conserved principles are highlighted. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

  8. Micromechanical and surface adhesive properties of single saccharomyces cerevisiae cells

    NASA Astrophysics Data System (ADS)

    Farzi, Bahman; Cetinkaya, Cetin

    2017-09-01

    The adhesion and mechanical properties of a biological cell (e.g. cell membrane elasticity and adhesiveness) are often strong indicators for the state of its health. Many existing techniques for determining mechanical properties of cells require direct physical contact with a single cell or a group of cells. Physical contact with the cell can trigger complex mechanotransduction mechanisms, leading to cellular responses, and consequently interfering with measurement accuracy. In the current work, based on ultrasonic excitation and interferometric (optical) motion detection, a non-contact method for characterizing the adhesion and mechanical properties of single cells is presented. It is experimentally demonstrated that the rocking (rigid body) motion and internal vibrational resonance frequencies of a single saccharomyces cerevisiae (SC) (baker’s yeast) cell can be acquired with the current approach, and the Young’s modulus and surface tension of the cell membrane as well as surface adhesion energy can be extracted from the values of these acquired resonance frequencies. The detected resonance frequency ranges for single SC cells include a rocking (rigid body) frequency of 330  ±  70 kHz and two breathing resonance frequencies of 1.53  ±  0.12 and 2.02  ±  0.31 MHz. Based on these values, the average work-of-adhesion of SC cells on a silicon substrate in aqueous medium is extracted, for the first time, as WASC-Si=16.2+/- 3.8 mJ {{m}-2} . Similarly, the surface tension and the Young’s modulus of the SC cell wall are predicted as {{σ }SC}=0.16+/- 0.02 N {{m}-1} and {{E}SC}= 9.20  ±  2.80 MPa, respectively. These results are compared to those reported in the literature by utilizing various methods, and good agreements are found. The current approach eliminates the measurement inaccuracies associated with the physical contact. Exciting and detecting cell dynamics at micro-second time-scales is significantly faster than the

  9. Interaction between lanthanide ions and Saccharomyces cerevisiae cells.

    PubMed

    Ene, Cristian D; Ruta, Lavinia L; Nicolau, Ioana; Popa, Claudia V; Iordache, Virgil; Neagoe, Aurora D; Farcasanu, Ileana C

    2015-10-01

    Lanthanides are a group of non-essential elements with important imaging and therapeutic applications. Although trivalent lanthanide ions (Ln³⁺) are used as potent blockers of Ca²⁺ channels, the systematic studies correlating Ln³⁺ accumulation and toxicity to Ca²⁺ channel blocking activity are scarce. In this study, we made use of the eukaryotic model Saccharomyces cerevisiae to investigate the correlation between Ln³⁺ accumulation, their toxicity and their capacity to block the exogenous stress-induced Ca²⁺ influx into the cytosol. It was found that the Ln³⁺ blocked the Ca²⁺ entry into the yeast cells only when present at concentration high enough to allow rapid binding to cell surface. At lower concentrations, Ln³⁺ were taken up by the cell, but Ca²⁺ blockage was no longer achieved. At 1 mM concentration, all ions from the Ln³⁺ series could block Ca²⁺ entry into cytosol with the exception of La³⁺, and to a lesser extent, Pr³⁺ and Nd³⁺. The plasma membrane Ca²⁺-channel Cch1/Mid1 contributed to La³⁺ and Gd³⁺ entry into the cells, with a significant preference for La³⁺. The results open the possibility to obtain cells loaded with controlled amounts and ratios of Ln³⁺.

  10. Effects of organic and inorganic additives on flotation recovery of washed cells of Saccharomyces cerevisiae resuspended in water.

    PubMed

    DeSousa, Sandro Rogério; Laluce, Cecilia; Jafelicci, Miguel

    2006-03-01

    Separation of microbial cells by flotation recovery is usually carried out in industrial reactors or wastewater treatment systems, which contain a complex mixture of microbial nutrients and excretion products. In the present study, the separation of yeast cells by flotation recovery was carried out using a simple flotation recovery systems containing washed yeast cells resuspended in water in order to elucidate the effects of additives (defined amounts of organic and inorganic acids, ethanol, surfactants and sodium chloride) on the cellular interactions at interfaces (cell/aqueous phase and cell/air bubble). When sodium chloride, organic acids (notably propionic, succinic and acetic acids) and organic surfactants (sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromide (CTAB) and Nonidet P40) were added to the flotation recovery system, significant increases in the cell recovery of yeast hydrophobic cells (Saccharomyces cerevisiae, strain FLT-01) were observed. The association of ethanol to acetic acid solution (a minor by-product of alcoholic fermentation) in the flotation recovery system, containing washed cells of strain FLT-01 resuspended in water, leading to an increased flotation recovery at pH 5.5. Thus, the association among products of the cellular metabolism (e.g., ethanol and acetic acid) can improve yeast cell recovery by flotation recovery.

  11. The Saccharomyces cerevisiae BEM1 homologue in Neurospora crassa promotes co-ordinated cell behaviour resulting in cell fusion.

    PubMed

    Schürg, Timo; Brandt, Ulrike; Adis, Christian; Fleissner, André

    2012-10-01

    Directed growth or movement is a common feature of microbial development and propagation. In polar growing filamentous fungi, directed growth requires the interaction of signal sensing machineries with factors controlling polarity and cell tip extension. In Neurospora crassa an unusual mode of cell-cell signalling mediates mutual attraction of germinating spores, which subsequently fuse. During directed growth of the two fusion partners, the cells co-ordinately alternate between two physiological stages, probably associated with signal sending and receiving. Here, we show that the Saccharomyces cerevisiae BEM1 homologue in N. crassa is essential for the robust and efficient functioning of this MAP kinase-based signalling system. BEM1 localizes to growing hyphal tips suggesting a conserved function as a polarity component. In the absence of BEM1, activation of MAK-2, a MAP kinase essential for germling fusion, is strongly reduced and delayed. Germling interactions become highly instable and successful fusion is greatly reduced. In addition, BEM1 is actively recruited around the forming fusion pore, suggesting potential functions after cell-cell contact has been established. By genetically dissecting the contribution of BEM1 to additional various polarization events, we also obtained first hints that BEM1 might function in different protein complexes controlling polarity and growth direction. © 2012 Blackwell Publishing Ltd.

  12. Cell size and budding during starvation of the yeast Saccharomyces cerevisiae.

    PubMed Central

    Johnston, G C

    1977-01-01

    When starved for nitrogen, cells of the yeast Saccharomyces cerevisiae produced abnormally small cells. Nonetheless, during starvation, only cells of a size characteristic of growing cells were capable of initiating a bud. Even when growth was severely limited, some event(s) in G1 required growth to a critical size for completion. PMID:334753

  13. Microbial Fuel Cells for Powering Navy Devices

    DTIC Science & Technology

    2014-01-20

    the anode is generated by fermentation of glucose by other microorganisms in the sediment represented by clostridium in Fig. 4. The products of the...MICROBIAL FUEL CELLS (ADAPTED FROM REF. A1) INTRODUCTION Dissimilatory metal-reducing bacteria (DMRB) are a class of microorganisms that...anode catalysts in microbial fuel cells. In the case of Geobacter spp., which are Deltaproteobacteria, a group of bacteria that share many similar

  14. Effects of low-intensity ultrasound on the growth, cell membrane permeability and ethanol tolerance of Saccharomyces cerevisiae.

    PubMed

    Dai, Chunhua; Xiong, Feng; He, Ronghai; Zhang, Weiwei; Ma, Haile

    2017-05-01

    Effects of low-intensity ultrasound (at different frequency, treatment time and power) on Saccharomyces cerevisiae in different growth phase were evaluated by the biomass in the paper. In addition, the cell membrane permeability and ethanol tolerance of sonicated Saccharomyces cerevisiae were also researched. The results revealed that the biomass of Saccharomyces cerevisiae increased by 127.03% under the optimum ultrasonic conditions such as frequency 28kHz, power 140W/L and ultrasonic time 1h when Saccharomyces cerevisiae cultured to the latent anaphase. And the membrane permeability of Saccharomyces cerevisiae in latent anaphase enhanced by ultrasound, resulting in the augment of extracellular protein, nucleic acid and fructose-1,6-diphosphate (FDP) contents. In addition, sonication could accelerate the damage of high concentration alcohol to Saccharomyces cerevisiae although the ethanol tolerance of Saccharomyces cerevisiae was not affected significantly by ultrasound.

  15. Microbial Cell Factories for Diol Production.

    PubMed

    Sabra, W; Groeger, C; Zeng, An-Ping

    2016-01-01

    Diols are compounds with two hydroxyl groups and have a wide range of appealing applications as chemicals and fuels. In particular, five low molecular diol compounds, namely 1,3-propanediol (1,3-PDO), 1,2-propanediol (1,2-PDO), 2,3-butanediol (2,3-BDO), 1,3-butanediol (1,3-BDO), and 1,4-butanediol (1,4-BDO), can be biotechnologically produced by direct microbial bioconversion of renewable materials. In this review, we summarize recent developments in the microbial production of diols, especially regarding the engineering of typical microbial strains as cell factory and the development of corresponding bioconversion processes.

  16. Changes of Saccharomyces cerevisiae cell membrane components and promotion to ethanol tolerance during the bioethanol fermentation.

    PubMed

    Dong, Shi-Jun; Yi, Chen-Feng; Li, Hao

    2015-12-01

    During bioethanol fermentation process, Saccharomyces cerevisiae cell membrane might provide main protection to tolerate accumulated ethanol, and S. cerevisiae cells might also remodel their membrane compositions or structure to try to adapt to or tolerate the ethanol stress. However, the exact changes and roles of S. cerevisiae cell membrane components during bioethanol fermentation still remains poorly understood. This study was performed to clarify changes and roles of S. cerevisiae cell membrane components during bioethanol fermentation. Both cell diameter and membrane integrity decreased as fermentation time lasting. Moreover, compared with cells at lag phase, cells at exponential and stationary phases had higher contents of ergosterol and oleic acid (C18:1) but lower levels of hexadecanoic (C16:0) and palmitelaidic (C16:1) acids. Contents of most detected phospholipids presented an increase tendency during fermentation process. Increased contents of oleic acid and phospholipids containing unsaturated fatty acids might indicate enhanced cell membrane fluidity. Compared with cells at lag phase, cells at exponential and stationary phases had higher expressions of ACC1 and HFA1. However, OLE1 expression underwent an evident increase at exponential phase but a decrease at following stationary phase. These results indicated that during bioethanol fermentation process, yeast cells remodeled membrane and more changeable cell membrane contributed to acquiring higher ethanol tolerance of S. cerevisiae cells. These results highlighted our knowledge about relationship between the variation of cell membrane structure and compositions and ethanol tolerance, and would contribute to a better understanding of bioethanol fermentation process and construction of industrial ethanologenic strains with higher ethanol tolerance. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Microbial fuel cells: Running on gas

    NASA Astrophysics Data System (ADS)

    Ren, Zhiyong Jason

    2017-06-01

    Methane is an abundant energy source that is used for power generation in thermal power plants via combustion, but direct conversion to electricity in fuel cells remains challenging. Now, a microbial fuel cell is demonstrated to efficiently convert methane directly to current by careful selection of a consortium of microorganisms.

  18. Why should cell biologists study microbial pathogens?

    PubMed

    Welch, Matthew D

    2015-12-01

    One quarter of all deaths worldwide each year result from infectious diseases caused by microbial pathogens. Pathogens infect and cause disease by producing virulence factors that target host cell molecules. Studying how virulence factors target host cells has revealed fundamental principles of cell biology. These include important advances in our understanding of the cytoskeleton, organelles and membrane-trafficking intermediates, signal transduction pathways, cell cycle regulators, the organelle/protein recycling machinery, and cell-death pathways. Such studies have also revealed cellular pathways crucial for the immune response. Discoveries from basic research on the cell biology of pathogenesis are actively being translated into the development of host-targeted therapies to treat infectious diseases. Thus there are many reasons for cell biologists to incorporate the study of microbial pathogens into their research programs.

  19. Analysis of Cell Cycle Progression in Saccharomyces cerevisiae Using the Budding Index and Tubulin Staining.

    PubMed

    Muñoz-Barrera, Marta; Monje-Casas, Fernando

    2017-01-01

    The budding index and the morphology of the spindle and the nucleus are excellent markers for the analysis of the progression through the different stages of the cell cycle in Saccharomyces cerevisiae. Here, we describe a protocol to evaluate the budding index in this model organism using phase contrast microscopy. We also describe an indirect immunofluorescence method designed for the visualization of microtubules and the nucleus in S. cerevisiae. Finally, we explain how both methodologies can be used in order to analyze cell cycle progression in the budding yeast.

  20. Bioconversion of lactose/whey to fructose diphosphate with recombinant Saccharomyces cerevisiae cells

    SciTech Connect

    Compagno, C.; Tura, A.; Ranzi, B.M.; Martegani, E. )

    1993-07-01

    Genetically engineered Saccharomyces cerevisiae strains that express Escherichia coli [beta]-galactosidase gene are able to bioconvert lactose or whey into fructose-1,6-diphosphate (FDP). High FDP yields from whey were obtained with an appropriate ratio between cell concentration and inorganic phosphate. The biomass of transformed cells can be obtained from different carbon sources, according to the expression vector bearing the lacZ gene. The authors showed that whey can be used as the carbon source for S. cerevisiae growth and as the substrate for bioconversion to fructose diphosphate.

  1. Analysis of rumen microbial populations in lactating dairy cattle fed diets varying in carbohydrate profiles and Saccharomyces cerevisiae fermentation product.

    PubMed

    Mullins, C R; Mamedova, L K; Carpenter, A J; Ying, Y; Allen, M S; Yoon, I; Bradford, B J

    2013-09-01

    The rumen microbial ecosystem is a critical factor that links diets to bovine physiology and productivity; however, information about dietary effects on microbial populations has generally been limited to small numbers of samples and qualitative assessment. To assess whether consistent shifts in microbial populations occur in response to common dietary manipulations in dairy cattle, samples of rumen contents were collected from 2 studies for analysis by quantitative real-time PCR (qPCR). In one study, lactating Holstein cows (n=8) were fed diets in which a nonforage fiber source replaced an increasing proportion of forages and concentrates in a 4×4 Latin square design, and samples of ruminal digesta were collected at 9-h intervals over 3 d at the end of each period. In the second study, lactating Holstein cows (n=15) were fed diets with or without the inclusion of a Saccharomyces cerevisiae fermentation product (SCFP) in a crossover design. In this study, rumen liquid and solid samples were collected during total rumen evacuations before and after feeding in a 42-h period. In total, 146 samples of ruminal digesta were used for microbial DNA isolation and analysis by qPCR. Validated primer sets were used to quantify total bacterial and anaerobic fungal populations as well as 12 well-studied bacterial taxa. The relative abundance of the target populations was similar to those previously reported. No significant treatment effects were observed for any target population. A significant interaction of treatment and dry matter intake was observed, however, for the abundance of Eubacterium ruminantium. Increasing dry matter intake was associated with a quadratic decrease in E. ruminantium populations in control animals but with a quadratic increase in E.ruminantium populations in cows fed SCFP. Analysis of sample time effects revealed that Fibrobacter succinogenes and fungal populations were more abundant postfeeding, whereas Ruminococcus albus tended to be more abundant

  2. A novel approach to regulate cell membrane permeability for ATP and NADH formation in Saccharomyces cerevisiae induced by air cold plasma

    NASA Astrophysics Data System (ADS)

    Dong, Xiaoyu; Liu, Tingting; Xiong, Yuqin

    2017-02-01

    Air cold plasma has been used as a novel method for enhancing microbial fermentation. The aim of this work was to explore the effect of plasma on membrane permeability and the formation of ATP and NADH in Saccharomyces cerevisiae, so as to provide valuable information for large-scale application of plasma in the fermentation industry. Suspensions of S. cerevisiae cells were exposed to air cold plasma for 0, 1, 2, 3, 4 and 5 min, and then subjected to various analyses prior to fermentation (0 h) and at the 9 and 21 h stages of fermentation. Compared with non-exposed cells, cells exposed to plasma for 1 min exhibited a marked increase in cytoplasmic free Ca2+ concentration as a result of the significant increase in membrane potential prior to fermentation. At the same time, the ATP level in the cell suspension decreased by about 40%, resulting in a reduction of about 60% in NADH prior to culturing. However, the levels of ATP and NADH in the culture at the 9 and 21 h fermentation stages were different from the level at 0 h. Taken together, the results indicated that exposure of S. cerevisiae to air cold plasma could increase its cytoplasmic free Ca2+ concentration by improving the cell membrane potential, consequently leading to changes in ATP and NADH levels. Supported by National Natural Science Foundation of China (Nos. 21246012, 21306015 and 21476032).

  3. A novel approach to regulate cell membrane permeability for ATP and NADH formation in Saccharomyces cerevisiae induced by air cold plasma

    NASA Astrophysics Data System (ADS)

    Xiaoyu, DONG; Tingting, LIU; Yuqin, XIONG

    2017-02-01

    Air cold plasma has been used as a novel method for enhancing microbial fermentation. The aim of this work was to explore the effect of plasma on membrane permeability and the formation of ATP and NADH in Saccharomyces cerevisiae, so as to provide valuable information for large-scale application of plasma in the fermentation industry. Suspensions of S. cerevisiae cells were exposed to air cold plasma for 0, 1, 2, 3, 4 and 5 min, and then subjected to various analyses prior to fermentation (0 h) and at the 9 and 21 h stages of fermentation. Compared with non-exposed cells, cells exposed to plasma for 1 min exhibited a marked increase in cytoplasmic free Ca2+ concentration as a result of the significant increase in membrane potential prior to fermentation. At the same time, the ATP level in the cell suspension decreased by about 40%, resulting in a reduction of about 60% in NADH prior to culturing. However, the levels of ATP and NADH in the culture at the 9 and 21 h fermentation stages were different from the level at 0 h. Taken together, the results indicated that exposure of S. cerevisiae to air cold plasma could increase its cytoplasmic free Ca2+ concentration by improving the cell membrane potential, consequently leading to changes in ATP and NADH levels. Supported by National Natural Science Foundation of China (Nos. 21246012, 21306015 and 21476032).

  4. [Advances in microbial solar cells--A review].

    PubMed

    Guo, Xiaoyun; Yu, Changping; Zheng, Tianling

    2015-08-04

    The energy crisis has become one of the major problems hindering the development of the world. The emergence of microbial fuel cells provides a new solution to the energy crisis. Microbial solar cells, integrating photosynthetic organisms such as plants and microalgae into microbial fuel cells, can convert solar energy into electrical energy. Microbial solar cell has steady electric energy, and broad application prospects in wastewater treatment, biodiesel processing and intermediate metabolites production. Here we reviewed recent progress of microbial solar cells from the perspective of the role of photosynthetic organisms in microbial fuel cells, based on a vast amount of literature, and discussed their advantages and deficiency. At last, brief analysis of the facing problems and research needs of microbial fuel cells are undertaken. This work was expected to be beneficial for the application of the microbial solar cells technology.

  5. Autonomous, Retrievable, Deep Sea Microbial Fuel Cell

    NASA Astrophysics Data System (ADS)

    Richter, K.

    2014-12-01

    Microbial fuel cells (MFCs) work by providing bacteria in anaerobic sediments with an electron acceptor (anode) that stimulates metabolism of organic matter. The buried anode is connected via control circuitry to a cathode exposed to oxygen in the overlying water. During metabolism, bacteria release hydrogen ions into the sediment and transfer electrons extra-cellularly to the anode, which eventually reduce dissolved oxygen at the cathode, forming water. The open circuit voltage is approximately 0.8 v. The voltage between electrodes is operationally kept at 0.4 v with a potentiastat. The current is chiefly limited by the rate of microbial metabolism at the anode. The Office of Naval Research has encouraged development of microbial fuel cells in the marine environment at a number of academic and naval institutions. Earlier work in shallow sediments of San Diego Bay showed that the most important environmental parameters that control fuel cell power output in San Diego Bay were total organic carbon in the sediment and seasonal water temperature. Current MFC work at SPAWAR includes extension of microbial fuel cell tests to the deep sea environment (>1000 m) and, in parallel, testing microbial fuel cells in the laboratory under deep sea conditions. One question we are asking is whether MFC power output from deep water sediments repressurized and chilled in the laboratory comparable to those measured in situ. If yes, mapping the power potential of deep sea sediments may be made much easier, requiring sediment grabs and lab tests rather than deployment and retrieval of fuel cells. Another question we are asking is whether in situ temperature and total organic carbon in the deep sea sediment can predict MFC power. If yes, then we can make use of the large collection of publicly available, deep sea oceanographic measurements to make these predictions, foregoing expensive work at sea. These regressions will be compared to those derived from shallow water measurements.

  6. Interval scanning photomicrography of microbial cell populations.

    NASA Technical Reports Server (NTRS)

    Casida, L. E., Jr.

    1972-01-01

    A single reproducible area of the preparation in a fixed focal plane is photographically scanned at intervals during incubation. The procedure can be used for evaluating the aerobic or anaerobic growth of many microbial cells simultaneously within a population. In addition, the microscope is not restricted to the viewing of any one microculture preparation, since the slide cultures are incubated separately from the microscope.

  7. Electricity production and microbial characterization of thermophilic microbial fuel cells.

    PubMed

    Dai, Kun; Wen, Jun-Li; Zhang, Fang; Ma, Xi-Wen; Cui, Xiang-Yu; Zhang, Qi; Zhao, Ting-Jia; Zeng, Raymond J

    2017-07-01

    Thermophilic microbial fuel cell (TMFC) offers many benefits, but the investigations on the diversity of exoelectrogenic bacteria are scarce. In this study, a two-chamber TMFC was constructed using ethanol as an electron donor, and the microbial dynamics were analyzed by high-throughput sequencing and 16S rRNA clone-library sequencing. The open-circuit potential of TMFC was approximately 650mV, while the maximum voltage was around 550mV. The maximum power density was 437mW/m(2), and the columbic efficiency in this work was 20.5±6.0%. The Firmicutes bacteria, related to the uncultured bacterium clone A55_D21_H_B_C01 with a similarity of 99%, accounted for 90.9% of all bacteria in the TMFC biofilm. This unknown bacterium has the potential to become a new thermophilic exoelectrogenic bacterium that is yet to be cultured. The development of TMFC-involved biotechnologies will be beneficial for the production of valuable chemicals and generation of energy in the future. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Cell wall dynamics modulate acetic acid-induced apoptotic cell death of Saccharomyces cerevisiae

    PubMed Central

    Rego, António; Duarte, Ana M.; Azevedo, Flávio; Sousa, Maria J.; Côrte-Real, Manuela; Chaves, Susana R.

    2014-01-01

    Acetic acid triggers apoptotic cell death in Saccharomyces cerevisiae, similar to mammalian apoptosis. To uncover novel regulators of this process, we analyzed whether impairing MAPK signaling affected acetic acid-induced apoptosis and found the mating-pheromone response and, especially, the cell wall integrity pathways were the major mediators, especially the latter, which we characterized further. Screening downstream effectors of this pathway, namely targets of the transcription factor Rlm1p, highlighted decreased cell wall remodeling as particularly important for acetic acid resistance. Modulation of cell surface dynamics therefore emerges as a powerful strategy to increase acetic acid resistance, with potential application in industrial fermentations using yeast, and in biomedicine to exploit the higher sensitivity of colorectal carcinoma cells to apoptosis induced by acetate produced by intestinal propionibacteria. PMID:28357256

  9. Saccharomyces cerevisiae accumulates GAPDH-derived peptides on its cell surface that induce death of non-Saccharomyces yeasts by cell-to-cell contact.

    PubMed

    Branco, Patrícia; Kemsawasd, Varongsiri; Santos, Lara; Diniz, Mário; Caldeira, Jorge; Almeida, Maria Gabriela; Arneborg, Nils; Albergaria, Helena

    2017-05-01

    During wine fermentations, Saccharomyces cerevisiae starts to excrete antimicrobial peptides (AMPs) into the growth medium that induce death of non-Saccharomyces yeasts at the end of exponential growth phase (24-48 h). Those AMPs were found to derive from the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). On the other hand, the early death of non-Saccharomyces yeasts during wine fermentations was also found to be mediated by a cell-to-cell contact mechanism. Since GAPDH is a cell-wall-associated protein in S. cerevisiae, we put forward the hypothesis that the GAPDH-derived AMPs could accumulate on the cell surface of S. cerevisiae, thus inducing death of non-Saccharomyces yeasts by cell-to-cell contact. Here we show that 48-h grown (stationary phase) cells of S. cerevisiae induce death of Hanseniaspora guilliermondii and Lachancea thermotolerans by direct cell-to-cell contact, while 12-h grown cells (mid-exponential phase) do not. Immunological tests performed with a specific polyclonal antibody against the GAPDH-derived AMPs revealed their presence in the cell wall of S. cerevisiae cells grown for 48 h, but not for 12 h. Taken together, our data show that accumulation of GAPDH-derived AMPs on the cell surface of S. cerevisiae is one of the factors underlying death of non-Saccharomyces yeasts by cell-to-cell contact. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  10. Expression of a Dianthus flavonoid glucosyltransferase in Saccharomyces cerevisiae for whole-cell biocatalysis.

    PubMed

    Werner, Sean R; Morgan, John A

    2009-07-15

    Glycosyltransferases are promising biocatalysts for the synthesis of small molecule glycosides. In this study, Saccharomyces cerevisiae expressing a flavonoid glucosyltransferase (GT) from Dianthus caryophyllus (carnation) was investigated as a whole-cell biocatalyst. Two yeast expression systems were compared using the flavonoid naringenin as a model substrate. Under in vitro conditions, naringenin-7-O-glucoside was formed and a higher specific glucosyl transfer activity was found using a galactose inducible expression system compared to a constitutive expression system. However, S. cerevisiae expressing the GT constitutively was significantly more productive than the galactose inducible system under in vivo conditions. Interestingly, the glycosides were recovered directly from the culture broth and did not accumulate intracellularly. A previously uncharacterized naringenin glycoside formed using the D. caryophyllus GT was identified as naringenin-4'-O-glucoside. It was found that S. cerevisiae cells hydrolyze naringenin-7-O-glucoside during whole-cell biocatalysis, resulting in a low final glycoside titer. When phloretin was added as a substrate to the yeast strain expressing the GT constitutively, the natural product phlorizin was formed. This study demonstrates S. cerevisiae is a promising whole-cell biocatalyst host for the production of valuable glycosides.

  11. Recovery of Saccharomyces cerevisiae sublethally injured cells after Pulsed Electric Fields.

    PubMed

    Somolinos, M; Mañas, P; Condón, S; Pagán, R; García, D

    2008-07-31

    The objective was to investigate the influence of the recovery liquid medium on the repair of Saccharomyces cerevisiae sublethally injured cells after Pulsed Electric Fields (PEF) in media of different pH. Sublethal injury was detected in the yeast S. cerevisiae after 50 pulses at 12.0 kV cm(-1) in both pH 4.0 and 7.0, by using a selective medium plating technique. PEF treatments cause a repairable sublethal injury in S. cerevisiae. Injured cells showed their maximum repair capacity when suspended in Sabouraud Broth compared to Peptone Water or citrate-phosphate buffer of pH 4.0. The extent to which cells repair their injuries depended on the treatment medium pH, and on the nature of the storage medium. No repair was detected when the recovery liquid medium was citrate-phosphate buffer of pH 7.0. Acid conditions favour repair and survival of PEF-treated S. cerevisiae cells. This work contributes to the description of the mechanisms of PEF injury and inactivation, which would be useful in defining adequate PEF treatments, alone or in combination with additional hurdles, to assure food stability.

  12. Single-cell transcriptomics for microbial eukaryotes.

    PubMed

    Kolisko, Martin; Boscaro, Vittorio; Burki, Fabien; Lynn, Denis H; Keeling, Patrick J

    2014-11-17

    One of the greatest hindrances to a comprehensive understanding of microbial genomics, cell biology, ecology, and evolution is that most microbial life is not in culture. Solutions to this problem have mainly focused on whole-community surveys like metagenomics, but these analyses inevitably loose information and present particular challenges for eukaryotes, which are relatively rare and possess large, gene-sparse genomes. Single-cell analyses present an alternative solution that allows for specific species to be targeted, while retaining information on cellular identity, morphology, and partitioning of activities within microbial communities. Single-cell transcriptomics, pioneered in medical research, offers particular potential advantages for uncultivated eukaryotes, but the efficiency and biases have not been tested. Here we describe a simple and reproducible method for single-cell transcriptomics using manually isolated cells from five model ciliate species; we examine impacts of amplification bias and contamination, and compare the efficacy of gene discovery to traditional culture-based transcriptomics. Gene discovery using single-cell transcriptomes was found to be comparable to mass-culture methods, suggesting single-cell transcriptomics is an efficient entry point into genomic data from the vast majority of eukaryotic biodiversity.

  13. Microbial fuel cells for biosensor applications.

    PubMed

    Yang, Huijia; Zhou, Minghua; Liu, Mengmeng; Yang, Weilu; Gu, Tingyue

    2015-12-01

    Microbial fuel cells (MFCs) face major hurdles for real-world applications as power generators with the exception of powering small sensor devices. Despite tremendous improvements made in the last two decades, MFCs are still too expensive to build and operate and their power output is still too small. In view of this, in recently years, intensive researches have been carried out to expand the applications into other areas such as acid and alkali production, bioremediation of aquatic sediments, desalination and biosensors. Unlike power applications, MFC sensors have the immediate prospect to be practical. This review covers the latest developments in various proposed biosensor applications using MFCs including monitoring microbial activity, testing biochemical oxygen demand, detection of toxicants and detection of microbial biofilms that cause biocorrosion.

  14. Biosorption of water-soluble dyes on magnetically modified Saccharomyces cerevisiae subsp. uvarum cells.

    PubMed

    Safaríková, M; Ptácková, L; Kibriková, I; Safarík, I

    2005-05-01

    Brewer's yeast (bottom yeast, Saccharomyces cerevisiae subsp. uvarum) cells were magnetically modified using water based magnetic fluid stabilized with perchloric acid. Magnetically modified yeast cells efficiently adsorbed various water soluble dyes. The dyes adsorption can be described by the Langmuir adsorption model. The maximum adsorption capacity of the magnetic cells differed substantially for individual dyes; the highest value was found for aniline blue (approx. 220 mg per g of dried magnetic adsorbent).

  15. Molecular mechanisms of Saccharomyces cerevisiae stress adaptation and programmed cell death in response to acetic acid.

    PubMed

    Giannattasio, Sergio; Guaragnella, Nicoletta; Zdralević, Maša; Marra, Ersilia

    2013-01-01

    Beyond its classical biotechnological applications such as food and beverage production or as a cell factory, the yeast Saccharomyces cerevisiae is a valuable model organism to study fundamental mechanisms of cell response to stressful environmental changes. Acetic acid is a physiological product of yeast fermentation and it is a well-known food preservative due to its antimicrobial action. Acetic acid has recently been shown to cause yeast cell death and aging. Here we shall focus on the molecular mechanisms of S. cerevisiae stress adaptation and programmed cell death in response to acetic acid. We shall elaborate on the intracellular signaling pathways involved in the cross-talk of pro-survival and pro-death pathways underlying the importance of understanding fundamental aspects of yeast cell homeostasis to improve the performance of a given yeast strain in biotechnological applications.

  16. Rapid count of microbial cells in dialysate.

    PubMed

    Shimakita, Tomonori; Yamamoto, Hidenori; Naramura, Tomotaka; Fujimori, Akira; Ide, Takao; Tashiro, Yoshikazu; Saito, Mikako; Matsuoka, Hideaki

    2007-10-01

    An apparatus for the non-culture method (NCM) of microbial cell count was formerly developed and named a bioplorer. The bioplorer NCM is based on the double staining of cells with 4', 6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI) and the automatic analysis of their fluorescent microscopic images. Viable cells can be stained with DAPI, while dead cells can be stained with DAPI and PI. In this study, the bioplorer NCM has been applied to the dialysate. The viable and dead cells in dialysate could be counted within 20 min. The detection limit expressed by log(10)[cells/100 mL] was 2.0. When cell-spiked dialysate samples containing prescribed number of Bacillus subtilis cells were assayed, the numbers of cells determined by the bioplorer NCM (N(VIA)(NCM)) and a conventional culture method (CM) on R2A medium (N(VIA)(R2A-CM)) were similar in the range of 2.6-4.6 within the 95% confidence interval (NCM-CM equivalent range). When test solutions sampled from a practical facility in a hospital were assayed, N(VIA)(NCM) was greater than, but comparable to, N(VIA)(R2A-CM). The endotoxin (ET) in the test samples were assayed as well using a test kit for limulus amoebocyte lysate assay. The results of microbial cells and ET concentration indicated that the dialysate supplying line was clean and well maintained. The bioplorer NCM can determine if the microbial contamination of dialysate supplying facilities is greater than 2.6 (398 cells/100 mL).

  17. Membrane fluidity sensoring microbial fuel cell.

    PubMed

    Choi, Youngjin; Jung, Eunkyoung; Kim, Sunghyun; Jung, Seunho

    2003-04-01

    A study has been performed to examine the effect of temperature and ethanolic stresses on the coulombic efficiency of a microbial fuel cell. The conventional-type fuel cell containing Gram-negative bacteria, Proteus vulgaris, was investigated as a model system. From current output measurements, it was found that the coulombic yields were altered by environmental stresses such as temperature shock or ethanol treatment to the bacteria. While high-temperature or ethanolic shock led to a remarkable decrement in coulombic output, the low-temperature shock induced a slight increase in microbial fuel cell efficiency. These results indicate that the membrane fluidity is affected considerably by environmental stress, which in turn affects the electron transfer process through the bacterial cell membrane to and from the electrode. This interpretation was confirmed by the cyclic voltammetric study of a mediator on an electrode surface modified with the lipids extracted from the membrane of P. vulgaris under the given stress. Markedly different electrochemical behaviors were observed depending on the environmental stress. A reciprocal relationship between coulomb output and the ratio of saturation/unsaturation of fatty acids has been observed. This is the first report, to our knowledge, that the structural adaptation of membrane fatty acids in response to the environmental shock can regulate the coulombic efficiency of a microbial fuel cell.

  18. Ethanol production from nonsterilized carob pod extract by free and immobilized Saccharomyces cerevisiae cells using fed-batch culture

    SciTech Connect

    Roukas, T. . Dept. of Food Science and Technology)

    1994-02-05

    The production of ethanol from carob pod extract by free and immobilized Saccharomyces cerevisiae cells in batch and fed-batch culture was investigated. Fed-batch culture proved to be a better fermentation system for the production of ethanol than batch culture. In fed-batch culture, both free and immobilized S. cerevisiae cells gave the same maximum concentration of final ethanol at an initial sugar concentration of 300 g/L and F = 167 mL/h. The maximum ethanol productivity was obtained with both free and immobilized cells at a substrate concentration of 300 g/L and F = 334 mL/h. In repeated fed-batch culture, immobilized S. cerevisiae cells gave a higher overall ethanol concentration compared with the free cells. The immobilized S. cerevisiae cells in Ca-alginate beads retained their ability to produce ethanol for 10 days.

  19. A theoretical study of the thermodynamics of microbial growth using Saccharomyces cerevisiae and a different free energy equation.

    PubMed

    Battley, Edwin H

    2013-06-01

    Microbial growth is a biological process that has been previously treated as a chemical reaction operating in accord with the Gibbs free energy equation, Delta G = Delta H-T Delta S. The heat of yeast growth was the first to be measured, in 1856, by direct calorimetry of a large wine vat. Until then there was a tendency for biologists to continue with the old notion that the energy change accompanying the growth of microorganisms was reflected in the amount of heat that was produced during this process. The application of chemical thermodynamics to systems involving microbial growth did not occur until much later. The full application of the Gibbs equation to microbial growth did not take place until the experimental measurement of yeast cell entropy was made in 1997 Further investigations then showed that the quantity of thermal energy for solid substances represented by TS was twice that of the quantity of thermal energy represented by Qab that is experimentally necessary to raise T of a substance from 0/K to T/K. Since there can only be one value for this, the use of the equation Delta X = Delta H-Delta Qab was investigated with respect to microbial growth, and is described in this review.

  20. From microbial communities to cells

    NASA Technical Reports Server (NTRS)

    Margulis, L.

    1985-01-01

    The eukraotic cell, the unit of structure of protoctists, plants, fungi, and animals, is not at all homologous to prokaryotic cells. Instead the eukaryotic cell is homologous to communities of microorganisms such as those of the sulfuretum. This research is based on the hypothesis that at least four different interacting community members entered the original associations that, when stabilized, led to the emergence of eukaryotic cells. These are: (1) host nucleocytoplasm (thermoplasma like archaebacteria); (2) mitochrondria (paracoccus or bdellovibryo like respiring bacteria; and (3) plastids (cyanobacteria) and undulipodia. Tubulin like protein was found in the free living spirochete Spirochaeta bajacaliforniensis and in several other spirochetes. The amino acid sequence was to see if the spirochete protein is homologous to the tubulin of undulipodial and mitotic spindle microtubules.

  1. Regulation of Cell Wall Biogenesis in Saccharomyces cerevisiae: The Cell Wall Integrity Signaling Pathway

    PubMed Central

    Levin, David E.

    2011-01-01

    The yeast cell wall is a strong, but elastic, structure that is essential not only for the maintenance of cell shape and integrity, but also for progression through the cell cycle. During growth and morphogenesis, and in response to environmental challenges, the cell wall is remodeled in a highly regulated and polarized manner, a process that is principally under the control of the cell wall integrity (CWI) signaling pathway. This pathway transmits wall stress signals from the cell surface to the Rho1 GTPase, which mobilizes a physiologic response through a variety of effectors. Activation of CWI signaling regulates the production of various carbohydrate polymers of the cell wall, as well as their polarized delivery to the site of cell wall remodeling. This review article centers on CWI signaling in Saccharomyces cerevisiae through the cell cycle and in response to cell wall stress. The interface of this signaling pathway with other pathways that contribute to the maintenance of cell wall integrity is also discussed. PMID:22174182

  2. Characterization of Cell Wall Proteins in Saccharomyces cerevisiae Clinical Isolates Elucidates Hsp150p in Virulence

    PubMed Central

    Hsu, Pang-Hung; Chiang, Pei-Chi; Liu, Chia-Hsun; Chang, Ya-Wen

    2015-01-01

    The budding yeast Saccharomyces cerevisiae has recently been described as an emerging opportunistic fungal pathogen. Fungal cell wall mannoproteins have been demonstrated to be involved in adhesion to inert surfaces and might be engaged in virulence. In this study, we observed four clinical isolates of S. cerevisiae with relatively hydrophobic cell surfaces. Yeast cell wall subproteome was evaluated quantitatively by liquid chromatography/tandem mass spectrometry. We identified totally 25 cell wall proteins (CWPs) from log-phase cells, within which 15 CWPs were quantified. The abundance of Scw10p, Pst1p, and Hsp150p/Pir2p were at least 2 folds higher in the clinical isolates than in S288c lab strain. Hsp150p is one of the members in Pir family conserved in pathogenic fungi Candida glabrata and Candida albicans. Overexpression of Hsp150p in lab strain increased cell wall integrity and potentially enhanced the virulence of yeast. Altogether, these results demonstrated that quantitative cell wall subproteome was analyzed in clinical isolates of S. cerevisiae, and several CWPs, especially Hsp150p, were found to be expressed at higher levels which presumably contribute to strain virulence and fungal pathogenicity. PMID:26270963

  3. Characterization of Cell Wall Proteins in Saccharomyces cerevisiae Clinical Isolates Elucidates Hsp150p in Virulence.

    PubMed

    Hsu, Pang-Hung; Chiang, Pei-Chi; Liu, Chia-Hsun; Chang, Ya-Wen

    2015-01-01

    The budding yeast Saccharomyces cerevisiae has recently been described as an emerging opportunistic fungal pathogen. Fungal cell wall mannoproteins have been demonstrated to be involved in adhesion to inert surfaces and might be engaged in virulence. In this study, we observed four clinical isolates of S. cerevisiae with relatively hydrophobic cell surfaces. Yeast cell wall subproteome was evaluated quantitatively by liquid chromatography/tandem mass spectrometry. We identified totally 25 cell wall proteins (CWPs) from log-phase cells, within which 15 CWPs were quantified. The abundance of Scw10p, Pst1p, and Hsp150p/Pir2p were at least 2 folds higher in the clinical isolates than in S288c lab strain. Hsp150p is one of the members in Pir family conserved in pathogenic fungi Candida glabrata and Candida albicans. Overexpression of Hsp150p in lab strain increased cell wall integrity and potentially enhanced the virulence of yeast. Altogether, these results demonstrated that quantitative cell wall subproteome was analyzed in clinical isolates of S. cerevisiae, and several CWPs, especially Hsp150p, were found to be expressed at higher levels which presumably contribute to strain virulence and fungal pathogenicity.

  4. Wireless sensors powered by microbial fuel cells.

    PubMed

    Shantaram, Avinash; Beyenal, Haluk; Raajan, Raaja; Veluchamy, Angathevar; Lewandowski, Zbigniew

    2005-07-01

    Monitoring parameters characterizing water quality, such as temperature, pH, and concentrations of heavy metals in natural waters, is often followed by transmitting the data to remote receivers using telemetry systems. Such systems are commonly powered by batteries, which can be inconvenient at times because batteries have a limited lifetime and must be recharged or replaced periodically to ensure that sufficient energy is available to power the electronics. To avoid these inconveniences, a microbial fuel cell was designed to power electrochemical sensors and small telemetry systems to transmit the data acquired by the sensors to remote receivers. The microbial fuel cell was combined with low-power, high-efficiency electronic circuitry providing a stable power source for wireless data transmission. To generate enough power for the telemetry system, energy produced by the microbial fuel cell was stored in a capacitor and used in short bursts when needed. Since commercial electronic circuits require a minimum 3.3 V input and our cell was able to deliver a maximum of 2.1 V, a DC-DC converter was used to boost the potential. The DC-DC converter powered a transmitter, which gathered the data from the sensor and transmitted it wirelessly to a remote receiver. To demonstrate the utility of the system, temporal variations in temperature were measured, and the data were wirelessly transmitted to a remote receiver.

  5. Preparation of a Saccharomyces cerevisiae cell-free extract for in vitro translation.

    PubMed

    Wu, Cheng; Sachs, Matthew S

    2014-01-01

    Eukaryotic cell-free in vitro translation systems have been in use since the 1970s. These systems can faithfully synthesize polypeptides when programmed with mRNA, enabling the production of polypeptides for analysis as well as permitting analyses of the cis- and trans-acting factors that regulate translation. Here we describe the preparation and use of cell-free translation systems from the yeast Saccharomyces cerevisiae.

  6. Exoelectrogenic bacteria that power microbial fuel cells.

    PubMed

    Logan, Bruce E

    2009-05-01

    There has been an increase in recent years in the number of reports of microorganisms that can generate electrical current in microbial fuel cells. Although many new strains have been identified, few strains individually produce power densities as high as strains from mixed communities. Enriched anodic biofilms have generated power densities as high as 6.9 W per m(2) (projected anode area), and therefore are approaching theoretical limits. To understand bacterial versatility in mechanisms used for current generation, this Progress article explores the underlying reasons for exocellular electron transfer, including cellular respiration and possible cell-cell communication.

  7. Microbial fuel cell with improved anode

    DOEpatents

    Borole, Abhijeet P.

    2010-04-13

    The present invention relates to a method for preparing a microbial fuel cell, wherein the method includes: (i) inoculating an anodic liquid medium in contact with an anode of the microbial fuel cell with one or more types of microorganisms capable of functioning by an exoelectrogenic mechanism; (ii) establishing a biofilm of the microorganisms on and/or within the anode along with a substantial absence of planktonic forms of the microorganisms by substantial removal of the planktonic microorganisms during forced flow and recirculation conditions of the anodic liquid medium; and (iii) subjecting the microorganisms of the biofilm to a growth stage by incorporating one or more carbon-containing nutritive compounds in the anodic liquid medium during biofilm formation or after biofilm formation on the anode has been established.

  8. Molecular characterization of propolis-induced cell death in Saccharomyces cerevisiae.

    PubMed

    de Castro, Patrícia Alves; Savoldi, Marcela; Bonatto, Diego; Barros, Mário Henrique; Goldman, Maria Helena S; Berretta, Andresa A; Goldman, Gustavo Henrique

    2011-03-01

    Propolis, a natural product of plant resins, is used by the bees to seal holes in their honeycombs and protect the hive entrance. However, propolis has also been used in folk medicine for centuries. Here, we apply the power of Saccharomyces cerevisiae as a model organism for studies of genetics, cell biology, and genomics to determine how propolis affects fungi at the cellular level. Propolis is able to induce an apoptosis cell death response. However, increased exposure to propolis provides a corresponding increase in the necrosis response. We showed that cytochrome c but not endonuclease G (Nuc1p) is involved in propolis-mediated cell death in S. cerevisiae. We also observed that the metacaspase YCA1 gene is important for propolis-mediated cell death. To elucidate the gene functions that may be required for propolis sensitivity in eukaryotes, the full collection of about 4,800 haploid S. cerevisiae deletion strains was screened for propolis sensitivity. We were able to identify 138 deletion strains that have different degrees of propolis sensitivity compared to the corresponding wild-type strains. Systems biology revealed enrichment for genes involved in the mitochondrial electron transport chain, vacuolar acidification, negative regulation of transcription from RNA polymerase II promoter, regulation of macroautophagy associated with protein targeting to vacuoles, and cellular response to starvation. Validation studies indicated that propolis sensitivity is dependent on the mitochondrial function and that vacuolar acidification and autophagy are important for yeast cell death caused by propolis.

  9. Growth performance and gastrointestinal microbial ecology responses of piglets receiving Saccharomyces cerevisiae fermentation products after an oral challenge with Escherichia coli (K88).

    PubMed

    Kiarie, E; Bhandari, S; Scott, M; Krause, D O; Nyachoti, C M

    2011-04-01

    The effects of Saccharomyces cerevisiae fermentation products (YFP) on growth performance and gastrointestinal (GIT) microbial ecology in 90 weanling pigs orally challenged with Escherichia coli K88(+) (ETEC) were investigated. The YFP were an original YFP product (XPC) and a water-suspendable yeast fermentation prototype (WSYFP) from a commercial company. Treatments consisted of a negative control (NC, no in-feed or in-water additive), carbadox (AB, 55 mg of carbadox/kg of feed), XPC (in feed, 0.2%), and WSYFP (in water, 0.5, 1, or 2 g/pig per day), and each was allotted to 5 pens (3 pigs/pen). The diets met the 1998 NRC specifications. Pigs were acclimated to treatments for a 7-d period before an ETEC challenge. On d 8, blood was collected from pigs to determine the baseline packed cell volume (PCV) measurement, and pigs were orally challenged with ETEC. At various time points postchallenge, blood samples were taken, performance measures and fecal consistency scores were recorded, and gut digesta and tissue samples were taken to evaluate GIT morphology, microbial ecology, and metabolites. Preplanned contrasts were used for comparison. Pigs receiving YFP had greater ADFI than NC pigs on d 3 (424 vs. 378 g/d; P = 0.01) and d 7 (506 vs. 458 g/d; P = 0.03) postchallenge. This effect of YFP on ADFI was similar to that of AB on d 3, but pigs receiving AB ate more (576 vs. 506 g/d; P = 0.03) at d 7 than pigs receiving YFP. Pigs exhibited reduced (P < 0.001) PCV upon ETEC challenge; however, pigs receiving additives sustained a greater (P < 0.05) PCV at 72 h compared with the NC group. Compared with the NC pigs, pigs receiving YFP showed a smaller (P < 0.05) number of ileal mucosa adherent ETEC and prevalence of the order Enterobacteriales in the ileal digesta, which corresponded to less (5.09 vs. 6.97 mg/dL; P = 0.03) colonic ammonia on d 7 postchallenge. Most of the indices for ileal digesta bacterial richness and diversity were greater (P < 0.01) for YFP pigs compared

  10. Microbial fuel cells: Their application and microbiology

    NASA Astrophysics Data System (ADS)

    He, Zhen

    The energy crisis is an urgent global issue due to the increased consumption of the finite amount of fossil fuel. As a result, looking for alternative energy sources is of critical importance. Microbial fuel cell (MFC) technology can extract electric energy from wastewater, and thus is a sustainable approach to supply energy to our electricity-based society. My research focuses on the development of a suitable MFC reactor for wastewater treatment and the understanding of the microbial function in the MFC process. First, together with colleagues, I have developed a novel MFC reactor, named upflow microbial fuel cell (UMFC), by combining upflow and MFC technologies. The power output from the UMFC was improved by 10-fold after it was modified with a U-shape cathode. The UMFC appears to be a practical reactor for continuous operation, though the output of electric power requires further improvement. In addition, a sediment MFC with a rotating cathode was also developed and its performance was examined. Second, I have adopted a human distal gut anaerobe, Bacteroides thetaiotaomicron, as the model organism to study the role of fermentative bacterium in electricity generation. When B. thetaiotaomicron grew under an applied electric potential, an electric current was generated. GeneChip data indicated that this bacterium did not alter its metabolism during this process. Although B. thetaiotaomicron may not be capable of respiration with an electrode as the electron acceptor, the experiment has demonstrated that fermentative bacteria may play an important role in electricity generation.

  11. Monitoring of Saccharomyces cerevisiae cell proliferation on thiol-modified planar gold microelectrodes using impedance spectroscopy.

    PubMed

    Heiskanen, Arto R; Spégel, Christer F; Kostesha, Natalie; Ruzgas, Tautgirdas; Emnéus, Jenny

    2008-08-19

    An impedance spectroscopic study of the interaction between thiol-modified Au electrodes and Saccharomyces cerevisiae of strain EBY44 revealed that the cells formed an integral part of the interface, modulating the capacitive properties until a complete monolayer was obtained, whereas the charge transfer resistance ( R ct) to the redox process of [Fe(CN)6] 3-/4- showed a linear relationship to the number of cells even beyond the monolayer coverage. R ct showed strong pH dependence upon increasing the pH of the utilized buffer to 7.2. Upon addition of S. cerevisiae cells at pH 7.2, the obtained value of R ct showed over 560% increase with respect to the value obtained on the same thiol-modified electrode without cells. It was demonstrated that real-time monitoring of S. cerevisiae proliferation, with frequency-normalized imaginary admittance (real capacitance) as the indicator, was possible using a miniaturized culture system, ECIS Cultureware, with integrated planar cysteamine-modified Au microelectrodes. A monolayer coverage was reached after 20-28 h of cultivation, observed as an approximately 15% decrease in the real capacitance of the system.

  12. Endomitotic effect of a cell cycle mutation of Saccharomyces cerevisiae

    SciTech Connect

    Schild, D.; Ananthaswamy, H.N.; Mortimer, R.K.

    1981-03-01

    A recessive temperature-sensitive mutation of Saccharomyces cerevisiae has been isolated and shown to cause an increase in ploidy in both haploids and diploids. Genetic analysis revealed that the strain carrying the mutation was an aa diploid, although MNNG mutagenesis had been done on an a haploid strain. When the mutant strain was crossed with an ..cap alpha cap alpha.. diploid and the resultant tetraploid sporulated, some of the meiotic progeny of this tetraploid were themselves tetraploid, as shown by both genetic analysis and DNA measurements, instead of diploid as expected of tetraploid meiosis. The ability of these tetraploids to continue to produce tetraploid meiotic progeny was followed for four generations. It was found that tetraploidization was independent of sporulation temperature, but was dependent on the temperature of germination and the growth of the spores. Increase in ploidy occurred when the spores were germinated and grown at 30/sup 0/, but did not occur at 23/sup 0/. Two cycles of sporulation and growth at 23/sup 0/ resulted in haploids, which were shown to diploidize within 24 hr when grown at 30/sup 0/.

  13. Brazilian propolis protects Saccharomyces cerevisiae cells against oxidative stress

    PubMed Central

    de Sá, Rafael A.; de Castro, Frederico A.V.; Eleutherio, Elis C.A.; de Souza, Raquel M.; da Silva, Joaquim F.M.; Pereira, Marcos D.

    2013-01-01

    Propolis is a natural product widely used for humans. Due to its complex composition, a number of applications (antimicrobial, antiinflammatory, anesthetic, cytostatic and antioxidant) have been attributed to this substance. Using Saccharomyces cerevisiae as a eukaryotic model we investigated the mechanisms underlying the antioxidant effect of propolis from Guarapari against oxidative stress. Submitting a wild type (BY4741) and antioxidant deficient strains (ctt1Δ, sod1Δ, gsh1Δ, gtt1Δ and gtt2Δ) either to 15 mM menadione or to 2 mM hydrogen peroxide during 60 min, we observed that all strains, except the mutant sod1Δ, acquired tolerance when previously treated with 25 μg/mL of alcoholic propolis extract. Such a treatment reduced the levels of ROS generation and of lipid peroxidation, after oxidative stress. The increase in Cu/Zn-Sod activity by propolis suggests that the protection might be acting synergistically with Cu/Zn-Sod. PMID:24516431

  14. Effect of Saccharomyces cerevisiae on alfalfa nutrient degradation characteristics and rumen microbial populations of steers fed diets with different concentrate-to-forage ratios.

    PubMed

    Ding, Gengzhi; Chang, Ying; Zhao, Liping; Zhou, Zhenming; Ren, Liping; Meng, Qingxiang

    2014-01-01

    Live yeast (Saccharomyces cerevisiae) constitutes an effective additive for animal production; its probiotic effect may be related to the concentrate-to-forage ratio (CTFR). The objective of this study was to assess the effects of S. cerevisiae (SC) on fiber degradation and rumen microbial populations in steers fed diets with different levels of dietary concentrate. Ten Simmental × Local crossbred steers (450 ± 50 kg BW) were assigned to a control group or an SC group. Both groups were fed the same basal diet but the SC group received SC supplementation (8 × 10(9) cfu/h/d through the ruminal fistula) following a two-period crossover design. Each period consisted of four phases, each of which lasted 17 d: 10 d for dietary adaptation, 6 d for degradation study, and 1 d for rumen sample collection. From the 1(st) to the 4(th) phase, steers were fed in a stepwise fashion with increasing CTFRs, i.e., 30:70, 50:50, 70:30, and 90:10. The kinetics of dry matter and fiber degradation of alfalfa pellets were evaluated; the rumen microbial populations were detected using real-time PCR. The results revealed no significant (P > 0.05) interactions between dietary CTFR and SC for most parameters. Dietary CTFR had a significant effect (P < 0.01) on degradation characteristics of alfalfa pellets and the copies of rumen microorganism; the increasing concentrate level resulted in linear, quadratic or cubic variation trend for these parameters. SC supplementation significantly (P < 0.05) affected dry matter (DM) and neutral detergent fiber (NDF) degradation rates (c DM, c NDF) and NDF effective degradability (EDNDF). Compared with the control group, there was an increasing trend of rumen fungi and protozoa in SC group (P < 0.1); copies of total bacteria in SC group were significantly higher (P < 0.05). Additionally, percentage of Ruminobacter amylophilus was significantly lower (P < 0.05) but percentage of Selenomonas ruminantium was

  15. Effect of Saccharomyces cerevisiae on alfalfa nutrient degradation characteristics and rumen microbial populations of steers fed diets with different concentrate-to-forage ratios

    PubMed Central

    2014-01-01

    Live yeast (Saccharomyces cerevisiae) constitutes an effective additive for animal production; its probiotic effect may be related to the concentrate-to-forage ratio (CTFR). The objective of this study was to assess the effects of S. cerevisiae (SC) on fiber degradation and rumen microbial populations in steers fed diets with different levels of dietary concentrate. Ten Simmental × Local crossbred steers (450 ± 50 kg BW) were assigned to a control group or an SC group. Both groups were fed the same basal diet but the SC group received SC supplementation (8 × 109 cfu/h/d through the ruminal fistula) following a two-period crossover design. Each period consisted of four phases, each of which lasted 17 d: 10 d for dietary adaptation, 6 d for degradation study, and 1 d for rumen sample collection. From the 1st to the 4th phase, steers were fed in a stepwise fashion with increasing CTFRs, i.e., 30:70, 50:50, 70:30, and 90:10. The kinetics of dry matter and fiber degradation of alfalfa pellets were evaluated; the rumen microbial populations were detected using real-time PCR. The results revealed no significant (P > 0.05) interactions between dietary CTFR and SC for most parameters. Dietary CTFR had a significant effect (P < 0.01) on degradation characteristics of alfalfa pellets and the copies of rumen microorganism; the increasing concentrate level resulted in linear, quadratic or cubic variation trend for these parameters. SC supplementation significantly (P < 0.05) affected dry matter (DM) and neutral detergent fiber (NDF) degradation rates (cDM, cNDF) and NDF effective degradability (EDNDF). Compared with the control group, there was an increasing trend of rumen fungi and protozoa in SC group (P < 0.1); copies of total bacteria in SC group were significantly higher (P < 0.05). Additionally, percentage of Ruminobacter amylophilus was significantly lower (P < 0.05) but percentage of Selenomonas ruminantium was significantly

  16. Production of L-phenylacetyl carbinol by immobilized cells of Saccharomyces cerevisiae.

    PubMed

    Mandwal, A K; Tripathi, C K M; Trivedi, P D; Joshi, A K; Agarwal, S C; Bihari, Vinod

    2004-02-01

    Conversion of benzaldehyde to L-phenylacetyl carbinol (L-PAC) was achieved with immobilized, growing cells of Saccharomyces cerevisiae in different reactors. Product formation increased (31%) with the subsequent initial reuses of the entrapped cells. Biomass production and PAC formation depleted (40 and 57%, respectively) after 4-5 continuous growth and biotransformation cycles. With the regeneration of the biocatalysts, catalytic activity of the cells was resumed. The highest yields were in a stirred tank reactor (29 g PAC) from 77 g benzeldehyde with 14 repeated uses of entrapped cells.

  17. Glucose signaling-mediated coordination of cell growth and cell cycle in Saccharomyces cerevisiae.

    PubMed

    Busti, Stefano; Coccetti, Paola; Alberghina, Lilia; Vanoni, Marco

    2010-01-01

    Besides being the favorite carbon and energy source for the budding yeast Sacchromyces cerevisiae, glucose can act as a signaling molecule to regulate multiple aspects of yeast physiology. Yeast cells have evolved several mechanisms for monitoring the level of glucose in their habitat and respond quickly to frequent changes in the sugar availability in the environment: the cAMP/PKA pathways (with its two branches comprising Ras and the Gpr1/Gpa2 module), the Rgt2/Snf3-Rgt1 pathway and the main repression pathway involving the kinase Snf1. The cAMP/PKA pathway plays the prominent role in responding to changes in glucose availability and initiating the signaling processes that promote cell growth and division. Snf1 (the yeast homologous to mammalian AMP-activated protein kinase) is primarily required for the adaptation of yeast cell to glucose limitation and for growth on alternative carbon source, but it is also involved in the cellular response to various environmental stresses. The Rgt2/Snf3-Rgt1 pathway regulates the expression of genes required for glucose uptake. Many interconnections exist between the diverse glucose sensing systems, which enables yeast cells to fine tune cell growth, cell cycle and their coordination in response to nutritional changes.

  18. Glucose Signaling-Mediated Coordination of Cell Growth and Cell Cycle in Saccharomyces Cerevisiae

    PubMed Central

    Busti, Stefano; Coccetti, Paola; Alberghina, Lilia; Vanoni, Marco

    2010-01-01

    Besides being the favorite carbon and energy source for the budding yeast Sacchromyces cerevisiae, glucose can act as a signaling molecule to regulate multiple aspects of yeast physiology. Yeast cells have evolved several mechanisms for monitoring the level of glucose in their habitat and respond quickly to frequent changes in the sugar availability in the environment: the cAMP/PKA pathways (with its two branches comprising Ras and the Gpr1/Gpa2 module), the Rgt2/Snf3-Rgt1 pathway and the main repression pathway involving the kinase Snf1. The cAMP/PKA pathway plays the prominent role in responding to changes in glucose availability and initiating the signaling processes that promote cell growth and division. Snf1 (the yeast homologous to mammalian AMP-activated protein kinase) is primarily required for the adaptation of yeast cell to glucose limitation and for growth on alternative carbon source, but it is also involved in the cellular response to various environmental stresses. The Rgt2/Snf3-Rgt1 pathway regulates the expression of genes required for glucose uptake. Many interconnections exist between the diverse glucose sensing systems, which enables yeast cells to fine tune cell growth, cell cycle and their coordination in response to nutritional changes. PMID:22219709

  19. Molecular mechanisms of pyrimidine dimer excision in Saccharomyces cerevisiae: excision of dimers in cell extracts

    SciTech Connect

    Reynolds, R.J.; Love, J.D.; Friedberg, E.C.

    1981-08-01

    Cell-free extracts prepared from rad1-19, rad2-2, rad3-1, rad4-3, rad7-1, rad10-1, rad14-1, rad16-1, and cycl-1 (rad7) mutants of Saccharomyces cerevisiae all catalyze the preferential excision of thymine-containing pyrimidine dimers from ultraviolet-irradiated DNA specifically incised with M. luteus ultraviolet deoxyribonucleic acid incising activity.

  20. Proton transfer in microbial electrolysis cells

    DOE PAGES

    Borole, Abhijeet P.; Lewis, Alex J.

    2017-02-15

    Proton transfer and electron transfer are of prime importance in the development of microbial electrochemical cells. While electron transfer is primarily controlled by biology, proton transfer is controlled by process engineering and cell design. To develop commercially feasible technologies around the concept of a bioelectrochemical cell, real feedstocks have to be explored and associated limitations have to be identified. Here in this study, the proton transfer rate was quantified for a microbial electrolysis cell (MEC) and its dependence on process parameters was investigated using a proton balance model. The reaction system consisted of a biomass-derived pyrolytic aqueous stream as amore » substrate producing hydrogen in a flow-through MEC. The proton transfer rate increased with anode flow rate and organic loading rate up to a maximum of 0.36 ± 0.01 moles per m2 per h, equivalent to a hydrogen production rate of 9.08 L per L per day. Higher rates of hydrogen production, reaching 11.7 ± 0.2 L per L per day were achieved, when additional protons were provided via the cathode buffer. Electrochemical impedance spectroscopy shows that proton transfer was the dominant resistance in the production of hydrogen. The quantification of proton transfer rates for MECs with potential for biorefinery application and the demonstration of high hydrogen production rates approaching those required for commercial consideration indicate the strong potential of this technology for renewable hydrogen production. Understanding the transport phenomenon in bioelectrochemical cells is of great significance since these systems have potential for wide-ranging applications including energy production, bioremediation, chemical and nanomaterial synthesis, electro-fermentation, energy storage, desalination, and produced water treatment. Electron transfer in anode biofilms has been investigated extensively, but proton transfer studies are also important, since many cathodic half reactions

  1. Involvement of Rho-type GTPase in control of cell size in Saccharomyces cerevisiae.

    PubMed

    Kikuchi, Yo; Mizuuchi, Eri; Nogami, Satoru; Morishita, Shinichi; Ohya, Yoshikazu

    2007-06-01

    Maintaining specific cell size, which is important for many organisms, is achieved by coordinating cell growth and cell division. In the budding yeast Saccharomyces cerevisiae, the existence of two cell-size checkpoints is proposed: at the first checkpoint, cell size is monitored before budding at the G1/S transition, and at the second checkpoint, actin depolymerization occurring in the small bud is monitored before the G2/M transition. Morphological analyses have revealed that the small GTPase Rho1p participates in cell-size control at both the G1/S and the G2/M boundaries. One group of rho1 mutants (rho1A) underwent premature entry into mitosis, leading to the birth of abnormally small cells. In another group of rho1 mutants (rho1B), the mother cells failed to reach an appropriate size before budding, and expression of the G1 cyclin Cln2p began at an earlier phase of the cell cycle. Analyses of mutants defective in Rho1p effector proteins indicate that Skn7p, Fks1p and Mpk1p are involved in cell-size control. Thus, Rho1p and its downstream regulatory pathways are involved in controlling cell size in S. cerevisiae.

  2. Development of stress tolerant Saccharomyces cerevisiae strains by metabolic engineering: New aspects from cell flocculation and zinc supplementation.

    PubMed

    Cheng, Cheng; Zhang, Mingming; Xue, Chuang; Bai, Fengwu; Zhao, Xinqing

    2017-02-01

    Budding yeast Saccharomyces cerevisiae is widely studied for the production of biofuels from lignocellulosic biomass. However, economic production is currently challenged by the repression of cell growth and compromised fermentation performance of S. cerevisiae strains in the presence of various environmental stresses, including toxic level of final products, inhibitory compounds released from the pretreatment of cellulosic feedstocks, high temperature, and so on. Therefore, it is important to improve stress tolerance of S. cerevisiae to these stressful conditions to achieve efficient and economic production. In this review, the latest advances on development of stress tolerant S. cerevisiae strains are summarized, with the emphasis on the impact of cell flocculation and zinc addition. It was found that cell flocculation affected ethanol tolerance and acetic acid tolerance of S. cerevisiae, and addition of zinc to a suitable level improved stress tolerance of yeast cells to ethanol, high temperature and acetic acid. Further studies on the underlying mechanisms by which cell flocculation and zinc status affect stress tolerance will not only enrich our knowledge on stress response and tolerance mechanisms of S. cerevisiae, but also provide novel metabolic engineering strategies to develop robust yeast strains for biofuels production. Copyright © 2016 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  3. Discriminative power of fatty acid methyl ester (FAME) analysis using the microbial identification system (MIS) for Candida (Torulopsis) glabrata and Saccharomyces cerevisiae.

    PubMed

    Peltroche-Llacsahuanga, H; Schmidt, S; Lütticken, R; Haase, G

    2000-12-01

    Candida (Torulopsis) glabrata is frequently isolated in cases of fungal infection and commonly shows acquired or innate fluconazole resistance. Saccharomyces cerevisiae, an emerging opportunistic yeast pathogen, causes serious systemic infections in immunocompromised, and vaginitis and superficial infections in immunocompetent patients. For both species reliable identification in the routine laboratory is mandatory, but species identification of strains, e.g. trehalose-negative C. glabrata, may be difficult. Therefore, gas-liquid chromatography (GLC) of whole cell fatty acid methyl ester (FAME) profiles, that is independent of assimilation profiles of strains and suitable for reliable and rapid identification of clinically important yeasts, was applied. However, frequent misidentification of C. glabrata as S. cerevisiae has been reported when using the Yeast Clinical Database of MIS. Accuracy of MIS identification may be strongly influenced by the amounts of cell mass analyzed. Therefore, the present study compared the MIS results of these two yeasts achieved with different cell masses. Primarily we optimized, especially with respect to cost-effectiveness, the recommended streaking technique yielding a maximal recovery of 90-130 mg of cell mass from one plate, enabling testing of poor growing strains of C. glabrata. For all C. glabrata strains tested (n = 10) the highest identification scores (SI [Similarity Index] range 0.525-0.963, median 0.832) were achieved with 30 to 45 mg of cell mass. Only 5 of 10 S. cerevisiae strains revealed good library comparisons (SI > or = 0.5) when using 30 mg of cell mass, whereas with 45 mg all strains but two revealed this SI-level. For S. cerevisiae a higher amount of cell mass processed (up to 90 mg) was correlated with better identification scores (SI range using 90 mg: 0.464-0.870, median, 0.737). Several passages prior to FAME analysis of C. glabrata strains on recommended media revealed narrowing of SI ranges, but

  4. Cell-recycle batch process of Scheffersomyces stipitis and Saccharomyces cerevisiae co-culture for second generation bioethanol production.

    PubMed

    Ashoor, Selim; Comitini, Francesca; Ciani, Maurizio

    2015-11-01

    To achieve an optimized co-culture ratio of Scheffersomyces stipitis and Saccharomyces cerevisiae for the production of second generation bioethanol under a cell-recycle batch process. Three Sacc. cerevisiae strains were evaluated in co-culture with Sch. stipitis CBS 5773 at different ratios using synthetic medium containing glucose and xylose. Bioreactor trials indicated that the optimal condition for ethanol production using Sacc. cerevisiae EC1118 and Sch. stipitis co-culture was 1 % of O2 concentration. To increase ethanol production with Sacc. cerevisiae/Sch. stipitis co-culture a cell-recycle batch process was evaluated. Using this process, the maximum ethanol production (9.73 g l(-1)) and ethanol yield (0.42 g g(-1)) were achieved exhibiting a tenfold increase in ethanol productivity in comparison with batch process (2.1 g l(-1) h(-1)). In these conditions a stabilization of the cells ratio Sacc. cerevisiae/Sch. stipitis (1:5) at steady state condition was obtained. Batch cells recycling fermentation is an effective process to use Sch. stipitis/Sacc. cerevisiae co-culture for second generation ethanol production.

  5. Impact of Photocatalysis on Fungal Cells: Depiction of Cellular and Molecular Effects on Saccharomyces cerevisiae

    PubMed Central

    Thabet, Sana; Simonet, France; Lemaire, Marc; Guillard, Chantal

    2014-01-01

    We have investigated the antimicrobial effects of photocatalysis on the yeast model Saccharomyces cerevisiae. To accurately study the antimicrobial mechanisms of the photocatalytic process, we focused our investigations on two questions: the entry of the nanoparticles in treated cells and the fate of the intracellular environment. Transmission electronic microscopy did not reveal any entry of nanoparticles within the cells, even for long exposure times, despite degradation of the cell wall space and deconstruction of cellular compartments. In contrast to proteins located at the periphery of the cells, intracellular proteins did not disappear uniformly. Disappearance or persistence of proteins from the pool of oxidized intracellular isoforms was not correlated to their functions. Altogether, our data suggested that photocatalysis induces the establishment of an intracellular oxidative environment. This hypothesis was sustained by the detection of an increased level of superoxide ions (O2°−) in treated cells and by greater cell cultivability for cells expressing oxidant stress response genes during photocatalytic exposure. The increase in intracellular ROS, which was not connected to the entry of nanoparticles within the cells or to a direct contact with the plasma membrane, could be the result of an imbalance in redox status amplified by chain reactions. Moreover, we expanded our study to other yeast and filamentous fungi and pointed out that, in contrast to the laboratory model S. cerevisiae, some environmental strains are very resistant to photocatalysis. This could be related to the cell wall composition and structure. PMID:25261515

  6. Quantitation of alpha-factor internalization and response during the Saccharomyces cerevisiae cell cycle.

    PubMed Central

    Zanolari, B; Riezman, H

    1991-01-01

    The alpha-factor pheromone binds to specific cell surface receptors on Saccharomyces cerevisiae a cells. The pheromone is then internalized, and cell surface receptors are down-regulated. At the same time, a signal is transmitted that causes changes in gene expression and cell cycle arrest. We show that the ability of cells to internalize alpha-factor is constant throughout the cell cycle, a cells are also able to respond to pheromone throughout the cycle even though there is cell cycle modulation of the expression of two pheromone-inducible genes, FUS1 and STE2. Both of these genes are expressed less efficiently near or just after the START point of the cell cycle in response to alpha-factor. For STE2, the basal level of expression is modulated in the same manner. Images PMID:1656226

  7. Shape recognition of microbial cells by colloidal cell imprints

    NASA Astrophysics Data System (ADS)

    Borovička, Josef; Stoyanov, Simeon D.; Paunov, Vesselin N.

    2013-08-01

    We have engineered a class of colloids which can recognize the shape and size of targeted microbial cells and selectively bind to their surfaces. These imprinted colloid particles, which we called ``colloid antibodies'', were fabricated by partial fragmentation of silica shells obtained by templating the targeted microbial cells. We successfully demonstrated the shape and size recognition between such colloidal imprints and matching microbial cells. High percentage of binding events of colloidal imprints with the size matching target particles was achieved. We demonstrated selective binding of colloidal imprints to target microbial cells in a binary mixture of cells of different shapes and sizes, which also resulted in high binding selectivity. We explored the role of the electrostatic interactions between the target cells and their colloid imprints by pre-coating both of them with polyelectrolytes. Selective binding occurred predominantly in the case of opposite surface charges of the colloid cell imprint and the targeted cells. The mechanism of the recognition is based on the amplification of the surface adhesion in the case of shape and size match due to the increased contact area between the target cell and the colloidal imprint. We also tested the selective binding for colloid imprints of particles of fixed shape and varying sizes. The concept of cell recognition by colloid imprints could be used for development of colloid antibodies for shape-selective binding of microbes. Such colloid antibodies could be additionally functionalized with surface groups to enhance their binding efficiency to cells of specific shape and deliver a drug payload directly to their surface or allow them to be manipulated using external fields. They could benefit the pharmaceutical industry in developing selective antimicrobial therapies and formulations.

  8. Properties of catalase activity in vegetative and sporulating cells of yeast Saccharomyces cerevisiae.

    PubMed

    Ota, A

    1986-01-01

    Properties of catalase activities have been examined in the intact cells of early stationary phase and cells 3 hr after transfer to sporulation medium in Saccharomyces cerevisiae. The catalase activities of the two cells had a broad optimal pH from 6 to 8. Catalase activity in the intact cells increased throughout a 4-hr period of the observation following transfer to sporulation medium. Almost all the catalase activity in vegetative cells was lost by the treatment at 60 degrees C for 10 min. Catalase activities of both cells were inhibited by KCN, NaN3, o-phenanthroline, and PCMB. The catalase activity of the vegetative cells was slightly more inhibited and inactivated than that of the sporulating cells by the inhibitors and by the treatment with HCl or NaOH.

  9. Microbial fuel cells: From fundamentals to applications. A review.

    PubMed

    Santoro, Carlo; Arbizzani, Catia; Erable, Benjamin; Ieropoulos, Ioannis

    2017-07-15

    In the past 10-15 years, the microbial fuel cell (MFC) technology has captured the attention of the scientific community for the possibility of transforming organic waste directly into electricity through microbially catalyzed anodic, and microbial/enzymatic/abiotic cathodic electrochemical reactions. In this review, several aspects of the technology are considered. Firstly, a brief history of abiotic to biological fuel cells and subsequently, microbial fuel cells is presented. Secondly, the development of the concept of microbial fuel cell into a wider range of derivative technologies, called bioelectrochemical systems, is described introducing briefly microbial electrolysis cells, microbial desalination cells and microbial electrosynthesis cells. The focus is then shifted to electroactive biofilms and electron transfer mechanisms involved with solid electrodes. Carbonaceous and metallic anode materials are then introduced, followed by an explanation of the electro catalysis of the oxygen reduction reaction and its behavior in neutral media, from recent studies. Cathode catalysts based on carbonaceous, platinum-group metal and platinum-group-metal-free materials are presented, along with membrane materials with a view to future directions. Finally, microbial fuel cell practical implementation, through the utilization of energy output for practical applications, is described.

  10. Microbial fuel cells: From fundamentals to applications. A review

    NASA Astrophysics Data System (ADS)

    Santoro, Carlo; Arbizzani, Catia; Erable, Benjamin; Ieropoulos, Ioannis

    2017-07-01

    In the past 10-15 years, the microbial fuel cell (MFC) technology has captured the attention of the scientific community for the possibility of transforming organic waste directly into electricity through microbially catalyzed anodic, and microbial/enzymatic/abiotic cathodic electrochemical reactions. In this review, several aspects of the technology are considered. Firstly, a brief history of abiotic to biological fuel cells and subsequently, microbial fuel cells is presented. Secondly, the development of the concept of microbial fuel cell into a wider range of derivative technologies, called bioelectrochemical systems, is described introducing briefly microbial electrolysis cells, microbial desalination cells and microbial electrosynthesis cells. The focus is then shifted to electroactive biofilms and electron transfer mechanisms involved with solid electrodes. Carbonaceous and metallic anode materials are then introduced, followed by an explanation of the electro catalysis of the oxygen reduction reaction and its behavior in neutral media, from recent studies. Cathode catalysts based on carbonaceous, platinum-group metal and platinum-group-metal-free materials are presented, along with membrane materials with a view to future directions. Finally, microbial fuel cell practical implementation, through the utilization of energy output for practical applications, is described.

  11. Asymmetric biocatalysis with microbial enzymes and cells.

    PubMed

    Wohlgemuth, Roland

    2010-06-01

    Microbial enzymes and cells continue to be important tools and nature's privileged chiral catalysts for performing asymmetric biocatalysis from the analytical small scale to the preparative and large scale in synthesis and degradation. The application of biocatalysts for preparing molecular asymmetry has achieved high efficiency, enantioselectivity and yield and is experiencing today a worldwide renaissance. Recent developments in the discovery, development and production of stable biocatalysts, in the design of new biocatalytic processes and in the product recovery and purification processes have made biocatalytic approaches using microbial cells and enzymes attractive choices for the synthesis of chiral compounds. The methodologies of kinetic resolution and kinetic asymmetric transformation, dynamic kinetic resolution and deracemization, desymmetrization, asymmetric synthesis with or without diastereo control and multi-step asymmetric biocatalysis are finding increasing applications in research. The ever-increasing use of hydrolytic enzymes has been accompanied by new applications of oxidoreductases, transferases and lyases. Isomerases, already used in large-scale processes, and ligases, are emerging as interesting biocatalysts for new synthetic applications. The production of a wide variety of industrial products by asymmetric biocatalysis has even become the preferred method of production. Copyright 2010 Elsevier Ltd. All rights reserved.

  12. Genetic improvement of Saccharomyces cerevisiae wine strains for enhancing cell viability after desiccation stress.

    PubMed

    López-Martínez, Gema; Pietrafesa, Rocchina; Romano, Patrizia; Cordero-Otero, Ricardo; Capece, Angela

    2013-08-01

    In the last few decades spontaneous grape must fermentations have been replaced by inoculated fermentation with Saccharomyces cerevisiae strains as active dry yeast (ADY). Among the essential genes previously characterized to overcome the cell-drying/rehydration process, six belong to the group of very hydrophilic proteins known as hydrophilins. Among them, only SIP18 has shown early transcriptional response during dehydration stress. In fact, the overexpression in S. cerevisiae of gene SIP18 increases cell viability after the dehydration process. The purpose of this study was to characterize dehydration stress tolerance of three wild and one commercial S. cerevisiae strains of wine origin. The four strains were submitted to transformation by insertion of the gene SIP18. Selected transformants were submitted to the cell-drying-rehydration process and yeast viability was evaluated by both viable cell count and flow cytometry. The antioxidant capacity of SIP18p was illustrated by ROS accumulation reduction after H2 O2 attack. Growth data as cellular duplication times and lag times were calculated to estimate cell vitality after the cell rehydration process. The overexpressing SIP18 strains showed significantly longer time of lag phase despite less time needed to stop the leakage of intracellular compounds during the rehydration process. Subsequently, the transformants were tested in inoculated grape must fermentation at laboratory scale in comparison to untransformed strains. Chemical analyses of the resultant wines indicated that no significant change for the content of secondary compounds was detected. The obtained data showed that the transformation enhances the viability of ADY without affecting fermentation efficiency and metabolic behaviour. Copyright © 2013 John Wiley & Sons, Ltd.

  13. The cell wall compound of Saccharomyces cerevisiae as a novel wall material for encapsulation of probiotics.

    PubMed

    Mokhtari, Samira; Jafari, Seid Mahdi; Khomeiri, Morteza; Maghsoudlou, Yahya; Ghorbani, Mohammad

    2017-06-01

    Yeast cell wall is known as a food grade ingredient which is recently being used increasingly as a novel coating for encapsulation of different materials in the food industry. This application is limited to core materials smaller than yeast in size. In this study, we have tried to encapsulate larger particles by crushing yeast cells. Hence, probiotic bacteria of Lactobacillus acidophilus and Bifidobacterium bifidum were encapsulated firstly by calcium alginate using the emulsion method and these microbeads were coated again by Saccharomyces cerevisiae cell wall compound and another layer of calcium alginate. The average diameter of microcapsules for single layer microbeads (M), microbeads coated by two layers of alginate (MCA), and microbeads coated by a layer of yeast cell and two layers of alginate (MCYA) were 54.25±0.18, 77.43±8.24 and 103.66±13.33μm, respectively. In simulated gastrointestinal conditions, there was a significant (P<0.05) enhancement in resistance of L. acidophilus when applying a layer of S. cerevisiae cell wall compound. For MCA and MCYA after 2h exposure to simulated gastric juice, it was revealed a log reduction of 1.53±0.1 and 1.1±0.02 with pH1.55 and in simulated intestinal juice, 2.92±0.04 and 2.42±0.06 with 0.6% bile after previous 1h incubation in gastric conditions, respectively. It can be concluded that the cell wall compound of S. cerevisiae is a suitable protective coating for probiotics and it can improve the survival of probiotics within food products. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Decreased fluidity of cell membranes causes a metal ion deficiency in recombinant Saccharomyces cerevisiae producing carotenoids.

    PubMed

    Liu, Peitong; Sun, Liang; Sun, Yuxia; Shang, Fei; Yan, Guoliang

    2016-04-01

    The genome-wide transcriptional responses of S. cerevisiae to heterologous carotenoid biosynthesis were investigated using DNA microarray analysis. The results show that the genes involved in metal ion transport were specifically up-regulated in the recombinant strain, and metal ions, including Cu(2+), Fe(2+), Mn(2+), and Mg(2+), were deficient in the recombinant strain compared to the ion content of the parent strain. The decrease in metal ions was ascribed to a decrease in cell membrane (CM) fluidity caused by lower levels of unsaturated fatty acids and ergosterol. This was confirmed by the observation that metal ion levels were restored when CM fluidity was increased by supplying linoleic acid. In addition, a 24.3 % increase in the β-carotene concentration was observed. Collectively, our results suggest that heterologous production of carotenoids in S. cerevisiae can induce cellular stress by rigidifying the CM, which can lead to a deficiency in metal ions. Due to the importance of CM fluidity in cellular physiology, maintaining normal CM fluidity might be a potential approach to improving carotenoid production in genetically engineered S. cerevisiae.

  15. Anti-oxidant effects of pomegranate juice on Saccharomyces cerevisiae cell growth.

    PubMed

    Aslan, Abdullah; Can, Muhammed İsmail; Boydak, Didem

    2014-01-01

    Pomegranate juice has a number of positive effects on both human and animal subjects. Four groups were used in this study. i: Control group, ii: H2O2 group, iii: Pomegranate juice (PJ) group and iv: PJ + H2O2 group. Following the sterilization method for pomegranate juice (10%) and H2O2 (6% v/v), Saccharomyces cerevisiae cultures were added and the cultivation incubated at 35°C for 72 hours. Fatty acids and vitamin concentrations were measured using HPLC and GC and the total protein bands profile were determined by SDS-PAGE. According to our results statistically significant differences have been determined among the study groups in terms of fatty acids and vitamin (p<0,05). Fatty acid synthesis, vitamin control and cell density increased in groups to which PJ was given in comparison with the control group (p<0,05). Pomegranate juice increased vitamins, fatty acids and total protein expression in Saccharomyces cerevisiae in comparison with the control. Pomegranate juice has a positive effect on fatty acid, vitamin and protein synthesis by Saccharomyces cerevisiae. Accordingly, we believe that it has significantly decreased oxidative damage thereby making a positive impact on yeast development.

  16. Invert sugar formation with Saccharomyces cerevisiae cells encapsulated in magnetically responsive alginate microparticles

    NASA Astrophysics Data System (ADS)

    Safarik, Ivo; Sabatkova, Zdenka; Safarikova, Mirka

    2009-05-01

    Invert sugar (an equimolar mixture of glucose and fructose prepared by sucrose hydrolysis) is a very important food component. We have prepared magnetically responsive alginate microbeads containing entrapped Saccharomyces cerevisiae cells and magnetite microparticles which can be easily separated in an appropriate magnetic separator. The microbeads (typical diameter between 50 and 100 μm) were prepared using the water-in-oil emulsification process. The prepared microbeads containing yeast cells with invertase activity enabled efficient sucrose conversion. The biocatalyst was quite stable; the same catalytic activity was observed after one month storage at 4 °C and the microbeads could be used at least six times.

  17. Cells of the yeast Saccharomyces cerevisiae are transformable by DNA under non-artificial conditions.

    PubMed

    Nevoigt, E; Fassbender, A; Stahl, U

    2000-09-15

    Transformants of bakers' yeast (Saccharomyces cerevisiae) can be generated when non-growing cells metabolize sugars (without additional nutrients) in the presence of plasmid DNA. These results suggest that there is a mechanism by which DNA can naturally be taken up by the yeast cell. Natural transformation does not take place in common complete or minimal yeast culture media such as YPD and YNB. The starvation conditions used in our experiments thus seem to be an important prerequisite for such transformation events. Copyright 2000 John Wiley & Sons, Ltd.

  18. Members of the Hsp70 family of proteins in the cell wall of Saccharomyces cerevisiae.

    PubMed Central

    López-Ribot, J L; Chaffin, W L

    1996-01-01

    Western blot (immunoblot) analysis of cell wall and cytosolic extracts obtained from parental and ssa1 and ssa2 single- and double-mutant strains of Saccharomyces cerevisiae showed that the heat shock protein 70 (Hsp70) products of these genes, previously thought to be restricted to the cell interior, are also present in the cell wall. A cell wall location was further confirmed by indirect immunofluorescence with intact cells and biotinylation of extracellular Hsp70. Hsp70s have been implicated in translocation across the membrane and as molecular chaperones, and changes in the profile of cell wall proteins suggested that these proteins may have a similar role in the cell wall. PMID:8755907

  19. Dynactin is involved in a checkpoint to monitor cell wall synthesis in Saccharomyces cerevisiae.

    PubMed

    Suzuki, Masaya; Igarashi, Ryoji; Sekiya, Mizuho; Utsugi, Takahiko; Morishita, Shinichi; Yukawa, Masashi; Ohya, Yoshikazu

    2004-09-01

    Checkpoint controls ensure the completion of cell cycle events with high fidelity in the correct order. Here we show the existence of a novel checkpoint that ensures coupling of cell wall synthesis and mitosis. In response to a defect in cell wall synthesis, S. cerevisiae cells arrest the cell-cycle before spindle pole body separation. This arrest results from the regulation of the M-phase cyclin Clb2p at the transcriptional level through the transcription factor Fkh2p. Components of the dynactin complex are required to achieve the G2 arrest whilst keeping cells highly viable. Thus, the dynactin complex has a function in a checkpoint that monitors cell wall synthesis.

  20. Ohmic resistance affects microbial community and electrochemical kinetics in a multi-anode microbial electrochemical cell

    EPA Science Inventory

    Multi-anode microbial electrochemical cells (MXCs) are considered as one of the most promising configurations for scale-up of MXCs, but fundamental understanding of anode kinetics governing current density is limited in the MXCs. In this study we first assessed microbial communi...

  1. Ohmic resistance affects microbial community and electrochemical kinetics in a multi-anode microbial electrochemical cell

    EPA Science Inventory

    Multi-anode microbial electrochemical cells (MXCs) are considered as one of the most promising configurations for scale-up of MXCs, but fundamental understanding of anode kinetics governing current density is limited in the MXCs. In this study we first assessed microbial communi...

  2. Production of non-alcoholic beer using free and immobilized cells of Saccharomyces cerevisiae deficient in the tricarboxylic acid cycle.

    PubMed

    Navrátil, Marián; Dömény, Zoltán; Sturdík, Ernest; Smogrovicová, Daniela; Gemeiner, Peter

    2002-04-01

    Production of non-alcoholic beer using Saccharomyces cerevisiae has been studied. Non-recombinant mutant strains with a defect in the synthesis of tricarboxylic-acid-cycle enzymes were used and applied in both free and pectate-immobilized form, using both batch and packed-bed continuous systems. After fermentation, basic parameters of the beer produced by five mutant strains were compared with a standard strain of brewing yeast. Results showed that the beer prepared by mutant yeast cells was characterized by lower levels of total alcohols, with ethanol concentrations between 0.07 and 0.31% (w/w). The organic acids produced, especially lactic acid, in concentrations up to 1.38 g x l(-1) had a strong protective effect on the microbial stability of the final product and thus the usual addition of lactic acid could be omitted. Application of the yeast mutants appears to be a good alternative to the classical methods for the production of non-alcoholic beer.

  3. Immune-modulatory effects of dietary Saccharomyces cerevisiae cell wall in broiler chickens inoculated with Escherichia coli lipopolysaccharide.

    PubMed

    Morales-Lopez, R; Brufau, J

    2013-01-01

    1. An experiment was conducted to study the effect of yeast (Saccharomyces cerevisiae) cell wall (YCW) supplemented in diets of broiler chickens challenged with Escherichia coli lipopolysaccharide (LPS). 2. One-day-old broiler chicks were randomly distributed into 24 cages (6 replicate cages; 8 birds/cage) and were inoculated with 0 or 1 mg/kg body weight E. coli-LPS (d 4 and 9) and 0 or 500 mg YCW/kg feed, resulting in a 2 × 2 factorial arrangement of treatments. Experimental diets did not include coccidiostats, in-feed antibiotics or enzymes. 3. On d 21, the inoculation of E. coli-LPS reduced weight gain and feed intake and increased feed conversion ratio (FCR) of birds, an effect maintained until 28 d. In contrast, chickens given diets with YCW improved the FCR at both 21 and 28 d of age. 4. E. coli-LPS challenge reduced the relative weight of bursa of Fabricius, except when chickens were given YCW, which resulted in an interaction. Supplementation of broiler diets with YCW exacerbated the cellular immune response as measured by the delayed cutaneous hypersensitivity response test. 5. The results of this study suggested a benefit on feed efficiency when YCW was added to diets fed to broiler chickens challenged with E. coli-LPS. Part of the mode of action of YCW might be related to better maintenance of immune status in response to microbial challenge.

  4. Combining microbial cultures for efficient production of electricity from butyrate in a microbial electrochemical cell.

    PubMed

    Miceli, Joseph F; Garcia-Peña, Ines; Parameswaran, Prathap; Torres, César I; Krajmalnik-Brown, Rosa

    2014-10-01

    Butyrate is an important product of anaerobic fermentation; however, it is not directly used by characterized strains of the highly efficient anode respiring bacteria (ARB) Geobacter sulfurreducens in microbial electrochemical cells. By combining a butyrate-oxidizing community with a Geobacter rich culture, we generated a microbial community which outperformed many naturally derived communities found in the literature for current production from butyrate and rivaled the highest performing natural cultures in terms of current density (∼ 11A/m(2)) and Coulombic efficiency (∼ 70%). Microbial community analyses support the shift in the microbial community from one lacking efficient ARB in the marine hydrothermal vent community to a community consisting of ∼ 80% Geobacter in the anode biofilm. This demonstrates the successful production and adaptation of a novel microbial culture for generating electrical current from butyrate with high current density and high Coulombic efficiency, by combining two mixed microbial cultures containing complementing biochemical pathways. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Engineering Robustness of Microbial Cell Factories.

    PubMed

    Gong, Zhiwei; Nielsen, Jens; Zhou, Yongjin J

    2017-08-31

    Metabolic engineering and synthetic biology offer great prospects in developing microbial cell factories capable of converting renewable feedstocks into fuels, chemicals, food ingredients, and pharmaceuticals. However, prohibitively low production rate and mass concentration remain the major hurdles in industrial processes even though the biosynthetic pathways are comprehensively optimized. These limitations are caused by a variety of factors unamenable for host cell survival, such as harsh industrial conditions, fermentation inhibitors from biomass hydrolysates, and toxic compounds including metabolic intermediates and valuable target products. Therefore, engineered microbes with robust phenotypes is essential for achieving higher yield and productivity. In this review, the recent advances in engineering robustness and tolerance of cell factories is described to cope with these issues and briefly introduce novel strategies with great potential to enhance the robustness of cell factories, including metabolic pathway balancing, transporter engineering, and adaptive laboratory evolution. This review also highlights the integration of advanced systems and synthetic biology principles toward engineering the harmony of overall cell function, more than the specific pathways or enzymes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. The Saccharomyces cerevisiae Fin1 protein forms cell cycle-specific filaments between spindle pole bodies.

    PubMed

    van Hemert, Martijn J; Lamers, Gerda E M; Klein, Dionne C G; Oosterkamp, Tjerk H; Steensma, H Yde; van Heusden, G Paul H

    2002-04-16

    The FIN1 gene from the yeast Saccharomyces cerevisiae encodes a basic protein with putative coiled-coil regions. Here we show that in large-budded cells a green fluorescent protein-Fin1 fusion protein is visible as a filament between the two spindle pole bodies. In resting cells the protein is undetectable, and in small-budded cells it is localized in the nucleus. During late mitosis it localizes on the spindle pole bodies. Filaments of cyano fluorescent protein-tagged Fin1 colocalize with filaments of green fluorescent protein-tagged Tub1 only in large-budded cells. By electron and atomic force microscopy we showed that purified recombinant Fin1p self-assembles into filaments with a diameter of approximately 10 nm. Our results indicate that the Fin1 protein forms a cell cycle-specific filament, additional to the microtubules, between the spindle pole bodies of dividing yeast cells.

  7. The Saccharomyces cerevisiae Fin1 protein forms cell cycle-specific filaments between spindle pole bodies

    PubMed Central

    van Hemert, Martijn J.; Lamers, Gerda E. M.; Klein, Dionne C. G.; Oosterkamp, Tjerk H.; Steensma, H. Yde; van Heusden, G. Paul H.

    2002-01-01

    The FIN1 gene from the yeast Saccharomyces cerevisiae encodes a basic protein with putative coiled-coil regions. Here we show that in large-budded cells a green fluorescent protein-Fin1 fusion protein is visible as a filament between the two spindle pole bodies. In resting cells the protein is undetectable, and in small-budded cells it is localized in the nucleus. During late mitosis it localizes on the spindle pole bodies. Filaments of cyano fluorescent protein-tagged Fin1 colocalize with filaments of green fluorescent protein-tagged Tub1 only in large-budded cells. By electron and atomic force microscopy we showed that purified recombinant Fin1p self-assembles into filaments with a diameter of ≈10 nm. Our results indicate that the Fin1 protein forms a cell cycle-specific filament, additional to the microtubules, between the spindle pole bodies of dividing yeast cells. PMID:11929974

  8. Energy from algae using microbial fuel cells.

    PubMed

    Velasquez-Orta, Sharon B; Curtis, Tom P; Logan, Bruce E

    2009-08-15

    Bioelectricity production from a phytoplankton, Chlorella vulgaris, and a macrophyte, Ulva lactuca was examined in single chamber microbial fuel cells (MFCs). MFCs were fed with the two algae (as powders), obtaining differences in energy recovery, degradation efficiency, and power densities. C. vulgaris produced more energy generation per substrate mass (2.5 kWh/kg), but U. lactuca was degraded more completely over a batch cycle (73 +/- 1% COD). Maximum power densities obtained using either single cycle or multiple cycle methods were 0.98 W/m(2) (277 W/m(3)) using C. vulgaris, and 0.76 W/m(2) (215 W/m(3)) using U. lactuca. Polarization curves obtained using a common method of linear sweep voltammetry (LSV) overestimated maximum power densities at a scan rate of 1 mV/s. At 0.1 mV/s, however, the LSV polarization data was in better agreement with single- and multiple-cycle polarization curves. The fingerprints of microbial communities developed in reactors had only 11% similarity to inocula and clustered according to the type of bioprocess used. These results demonstrate that algae can in principle, be used as a renewable source of electricity production in MFCs.

  9. Microbial fuel cells meet with external resistance.

    PubMed

    Katuri, Krishna P; Scott, Keith; Head, Ian M; Picioreanu, Cristian; Curtis, Tom P

    2011-02-01

    The influence of external load on the composition of the anodic biofilm microbial community and biomass yield was investigated in a microbial fuel cell fed with glucose and domestic wastewater was used as source of electrogens. Denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR) amplified 16S rRNA gene fragments revealed distinct differences in anodic bacterial communities formed at the anode of each MFC operated under a different external load. These results implied that in an MFC, electrogenic bacteria were enriched under higher current densities, i.e., low external load, and were able to sustain better current and effluent quality. The influence of the external resistance applied to the MFCs during formation of the bacterial communities from sewage wastewater was shown to have no significant effect on power performance of the MFCs nor to have a significant influence on their anodic activity with both glucose and brewery wastewater as fuel. As expected, current generation, COD removal and the biomass yield were all directly influenced by the external load. Significantly, when operated under lower external load, the biomass yield in the MFC was less than that in conventional anaerobic digestion (i.e., control). Copyright © 2010 Elsevier Ltd. All rights reserved.

  10. Involvement of mitochondria and metacaspase elevation in harpin Pss-induced cell death of Saccharomyces cerevisiae.

    PubMed

    Sripriya, Paranthaman; Vedantam, Lakshmi Vasudev; Podile, Appa Rao

    2009-08-15

    Expression of a proteinaceous elicitor harpin(Pss,) encoded by hrpZ of Pseudomonas syringae pv. syringae 61, under GAL1 promoter in Saccharomyces cerevisiae Y187 resulted in galactose-inducible yeast cell death (YCD). Extracellular treatment of harpin did not affect the growth of yeast. The observed YCD was independent of the stage of cell cycle. "Petite" mutant of S. cerevisiae Y187 pYEUT-hrpZ was insensitive to cell death indicating the involvement of mitochondria in this YCD. Loss in mitochondrial potential, but no leakage of Cytochrome c from mitochondria into the cytosol, were notable features in harpin(Pss)-induced YCD. Cyclosporin A had no effect on hrpZ expressing yeast cells, further confirmed that there was no release of Cytochrome c. Elevation of caspase activity has been reported for the first time in this form of cell death induced by harpin expression. Release of reactive oxygen species and clear loss of membrane integrity were evident with the absence of nuclear fragmentation and chromosomal condensation, while annexin V and propidium iodide staining showed features typical of necrosis.

  11. Electrochemical detection of intracellular and cell membrane redox systems in Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Rawson, Frankie J.; Downard, Alison J.; Baronian, Keith H.

    2014-06-01

    Redox mediators can interact with eukaryote cells at a number of different cell locations. While cell membrane redox centres are easily accessible, the redox centres of catabolism are situated within the cytoplasm and mitochondria and can be difficult to access. We have systematically investigated the interaction of thirteen commonly used lipophilic and hydrophilic mediators with the yeast Saccharomyces cerevisiae. A double mediator system is used in which ferricyanide is the final electron acceptor (the reporter mediator). After incubation of cells with mediators, steady state voltammetry of the ferri/ferrocyanide redox couple allows quantitation of the amount of mediator reduced by the cells. The plateau current at 425 mV vs Ag/AgCl gives the analytical signal. The results show that five of the mediators interact with at least three different trans Plasma Membrane Electron Transport systems (tPMETs), and that four mediators cross the plasma membrane to interact with cytoplasmic and mitochondrial redox molecules. Four of the mediators inhibit electron transfer from S. cerevisiae. Catabolic inhibitors were used to locate the cellular source of electrons for three of the mediators.

  12. Electrochemical detection of intracellular and cell membrane redox systems in Saccharomyces cerevisiae

    PubMed Central

    Rawson, Frankie J.; Downard, Alison J.; Baronian, Keith H.

    2014-01-01

    Redox mediators can interact with eukaryote cells at a number of different cell locations. While cell membrane redox centres are easily accessible, the redox centres of catabolism are situated within the cytoplasm and mitochondria and can be difficult to access. We have systematically investigated the interaction of thirteen commonly used lipophilic and hydrophilic mediators with the yeast Saccharomyces cerevisiae. A double mediator system is used in which ferricyanide is the final electron acceptor (the reporter mediator). After incubation of cells with mediators, steady state voltammetry of the ferri/ferrocyanide redox couple allows quantitation of the amount of mediator reduced by the cells. The plateau current at 425 mV vs Ag/AgCl gives the analytical signal. The results show that five of the mediators interact with at least three different trans Plasma Membrane Electron Transport systems (tPMETs), and that four mediators cross the plasma membrane to interact with cytoplasmic and mitochondrial redox molecules. Four of the mediators inhibit electron transfer from S. cerevisiae. Catabolic inhibitors were used to locate the cellular source of electrons for three of the mediators. PMID:24910017

  13. Microbial fuel cells and microbial electrolysis cells for the production of bioelectricity and biomaterials.

    PubMed

    Zhou, Minghua; Yang, Jie; Wang, Hongyu; Jin, Tao; Xu, Dake; Gu, Tingyue

    2013-01-01

    Today's global energy crisis requires a multifaceted solution. Bioenergy is an important part of the solution. The microbial fuel cell (MFC) technology stands out as an attractive potential technology in bioenergy. MFCs can convert energy stored in organic matter directly into bioelectricity. MFCs can also be operated in the electrolysis mode as microbial electrolysis cells to produce bioproducts such as hydrogen and ethanol. Various wastewaters containing low-grade organic carbons that are otherwise unutilized can be used as feed streams for MFCs. Despite major advances in the past decade, further improvements in MFC power output and cost reduction are needed for MFCs to be practical. This paper analysed MFC operating principles using bioenergetics and bioelectrochemistry. Several major issues were explored to improve the MFC performance. An emphasis was placed on the use of catalytic materials for MFC electrodes. Recent advances in the production of various biomaterials using MFCs were also investigated.

  14. Two stage bioethanol refining with multi litre stacked microbial fuel cell and microbial electrolysis cell.

    PubMed

    Sugnaux, Marc; Happe, Manuel; Cachelin, Christian Pierre; Gloriod, Olivier; Huguenin, Gérald; Blatter, Maxime; Fischer, Fabian

    2016-12-01

    Ethanol, electricity, hydrogen and methane were produced in a two stage bioethanol refinery setup based on a 10L microbial fuel cell (MFC) and a 33L microbial electrolysis cell (MEC). The MFC was a triple stack for ethanol and electricity co-generation. The stack configuration produced more ethanol with faster glucose consumption the higher the stack potential. Under electrolytic conditions ethanol productivity outperformed standard conditions and reached 96.3% of the theoretically best case. At lower external loads currents and working potentials oscillated in a self-synchronized manner over all three MFC units in the stack. In the second refining stage, fermentation waste was converted into methane, using the scale up MEC stack. The bioelectric methanisation reached 91% efficiency at room temperature with an applied voltage of 1.5V using nickel cathodes. The two stage bioethanol refining process employing bioelectrochemical reactors produces more energy vectors than is possible with today's ethanol distilleries.

  15. Increasing ethanol productivity during xylose fermentation by cell recycling of recombinant Saccharomyces cerevisiae.

    PubMed

    Roca, C; Olsson, L

    2003-01-01

    The influence of cell recycling of xylose-fermenting Saccharomyces cerevisiae TMB3001 was investigated during continuous cultivation on a xylose-glucose mixture. By using cell recycling at the dilution rate ( D) of 0.05 h(-1), the cell-mass concentration could be increased from 2.2 g l(-1) to 22 g l(-1). Consequently, the volumetric ethanol productivity increased ten-fold, from 0.5 g l(-1) h(-1) to 5.35 g l(-1) h(-1). By increasing the biomass concentration, the xylose consumption rate increased from 0.75 g xylose l(-1) h(-1) without recycling to 1.9 g l(-1) h(-1) with recycling. The specific ethanol productivity was in the range of 0.23-0.26 g g(-1) h(-1) with or without cell recycling, showing that an increased cell-mass concentration did not influence the efficiency of the yeast.

  16. Deep sea microbial fuel cell output as a proxy for microbial activity

    NASA Astrophysics Data System (ADS)

    Richter, K.; George, R.; Hardy, K. R.

    2016-02-01

    Abstract: Microbial fuel cells (MFCs) work by providing bacteria in anaerobic sediments with an electron acceptor (anode) that stimulates metabolism of organic matter. The buried anode is connected via control circuitry to a cathode exposed to oxygen in the overlying water. During metabolism, bacteria release hydrogen ions into the sediment and transfer electrons extra-cellularly to the anode, which eventually reduce dissolved oxygen at the cathode, forming water. The current is chiefly limited by the rate of microbial metabolism at the anode and serves as a proxy for microbial activity. The Office of Naval Research has encouraged development of microbial fuel cells in the marine environment at a number of academic and naval institutions and studies of important environmental parameters that affect fuel cell performance. Earlier work in shallow sediments of San Diego Bay showed that the most important environmental parameters that control fuel cell power output in San Diego Bay were total organic carbon in the sediment and seasonal water temperature. Current MFC work at SPAWAR includes extension of microbial fuel cell tests to the deep sea environment (>4000 m) and, in parallel, testing microbial fuel cells in the laboratory under deep sea conditions. We are pursuing a field efforts to deploy a microbial fuel cell in progressively deeper water, record in situ power and temperature over several weeks, and retrieve the fuel cell along with sediment samples for analysis. We are also pursuing a laboratory effort to build a matching microbial fuel cell in a pressure vessel capable of matching the pressure and temperature of deep water, and stocking the pressure vessel with deep water sediment in order to take measurements analogous to those in the field. We also hope to determine whether bacteria growing on the anode are different from bacteria growing in the bulk sediment via DNA analysis. The current progress and results from this work at SPAWAR will be presented.

  17. Microbial Fuel Cells and Microbial Ecology: Applications in Ruminant Health and Production Research

    PubMed Central

    Osterstock, Jason B.; Pinchak, William E.; Ishii, Shun’ichi; Nelson, Karen E.

    2009-01-01

    Microbial fuel cell (MFC) systems employ the catalytic activity of microbes to produce electricity from the oxidation of organic, and in some cases inorganic, substrates. MFC systems have been primarily explored for their use in bioremediation and bioenergy applications; however, these systems also offer a unique strategy for the cultivation of synergistic microbial communities. It has been hypothesized that the mechanism(s) of microbial electron transfer that enable electricity production in MFCs may be a cooperative strategy within mixed microbial consortia that is associated with, or is an alternative to, interspecies hydrogen (H2) transfer. Microbial fermentation processes and methanogenesis in ruminant animals are highly dependent on the consumption and production of H2in the rumen. Given the crucial role that H2 plays in ruminant digestion, it is desirable to understand the microbial relationships that control H2 partial pressures within the rumen; MFCs may serve as unique tools for studying this complex ecological system. Further, MFC systems offer a novel approach to studying biofilms that form under different redox conditions and may be applied to achieve a greater understanding of how microbial biofilms impact animal health. Here, we present a brief summary of the efforts made towards understanding rumen microbial ecology, microbial biofilms related to animal health, and how MFCs may be further applied in ruminant research. PMID:20024685

  18. Microbial fuel cells and microbial ecology: applications in ruminant health and production research.

    PubMed

    Bretschger, Orianna; Osterstock, Jason B; Pinchak, William E; Ishii, Shun'ichi; Nelson, Karen E

    2010-04-01

    Microbial fuel cell (MFC) systems employ the catalytic activity of microbes to produce electricity from the oxidation of organic, and in some cases inorganic, substrates. MFC systems have been primarily explored for their use in bioremediation and bioenergy applications; however, these systems also offer a unique strategy for the cultivation of synergistic microbial communities. It has been hypothesized that the mechanism(s) of microbial electron transfer that enable electricity production in MFCs may be a cooperative strategy within mixed microbial consortia that is associated with, or is an alternative to, interspecies hydrogen (H(2)) transfer. Microbial fermentation processes and methanogenesis in ruminant animals are highly dependent on the consumption and production of H(2)in the rumen. Given the crucial role that H(2) plays in ruminant digestion, it is desirable to understand the microbial relationships that control H(2) partial pressures within the rumen; MFCs may serve as unique tools for studying this complex ecological system. Further, MFC systems offer a novel approach to studying biofilms that form under different redox conditions and may be applied to achieve a greater understanding of how microbial biofilms impact animal health. Here, we present a brief summary of the efforts made towards understanding rumen microbial ecology, microbial biofilms related to animal health, and how MFCs may be further applied in ruminant research.

  19. Programming microbial population dynamics by engineered cell-cell communication.

    PubMed

    Song, Hao; Payne, Stephen; Tan, Cheemeng; You, Lingchong

    2011-07-01

    A major aim of synthetic biology is to program novel cellular behavior using engineered gene circuits. Early endeavors focused on building simple circuits that fulfill simple functions, such as logic gates, bistable toggle switches, and oscillators. These gene circuits have primarily focused on single-cell behaviors since they operate intracellularly. Thus, they are often susceptible to cell-cell variations due to stochastic gene expression. Cell-cell communication offers an efficient strategy to coordinate cellular behavior at the population level. To this end, we review recent advances in engineering cell-cell communication to achieve reliable population dynamics, spanning from communication within single species to multispecies, from one-way sender-receiver communication to two-way communication in synthetic microbial ecosystems. These engineered systems serve as well-defined model systems to better understand design principles of their naturally occurring counterparts and to facilitate novel biotechnology applications.

  20. Programming microbial population dynamics by engineered cell-cell communication

    PubMed Central

    Song, Hao; Payne, Stephen; Tan, Cheemeng; You, Lingchong

    2013-01-01

    A major aim of synthetic biology is to program novel cellular behaviors using engineered gene circuits. Early endeavors focused on building simple circuits that fulfill simple functions, such as logic gates, bistable toggle switches, and oscillators. These gene circuits have primarily focused on single-cell behaviors since they operate intracellularly. Thus, they are often susceptible to cell-cell variations due to stochastic gene expression. Cell-cell communication offers an efficient strategy to coordinate cellular behaviors at the population level. To this end, we review recent advances in engineering cell-cell communication to achieve reliable population dynamics, spanning from communication within single species to multispecies, from one-way sender-receiver communication to two-way communication in synthetic microbial ecosystems. These engineered systems serve as well-defined model systems to better understand design principles of their naturally occurring counterparts and to facilitate novel biotechnology applications. PMID:21681967

  1. Methanogenesis in membraneless microbial electrolysis cells.

    PubMed

    Clauwaert, Peter; Verstraete, Willy

    2009-04-01

    Operation of microbial electrolysis cells (MECs) without an ion exchange membrane could help to lower the construction costs while lowering the ohmic cell resistance and improving MEC conversion rates by minimizing the pH gradient between anode and cathode. In this research, we demonstrate that membraneless MECs with plain graphite can be operated for methane production without pH adjustment and that the ohmic cell resistance could be lowered with approximately 50% by removing the cation exchange membrane. As a result, the current production increased from 66 +/- 2 to 156 +/- 1 A m(-3) MEC by removing the membrane with an applied voltage of -0.8 V. Methane was the main energetic product despite continuous operation under carbonate-limited and slightly acidified conditions (pH 6.1-6.2). Our results suggest that continuous production of hydrogen in membraneless MECs will be challenging since methane production might not be avoided easily. The electrical energy invested was not always completely recovered under the form of an energy-rich biogas; however, our results indicate that membraneless MECs might be a viable polishing step for the treatment of the effluent of anaerobic digesters as methane was produced under low organic loading conditions and at room temperature.

  2. Biological denitrification in microbial fuel cells.

    PubMed

    Clauwaert, Peter; Rabaey, Korneel; Aelterman, Peter; de Schamphelaire, Liesje; Pham, The Hai; Boeckx, Pascal; Boon, Nico; Verstraete, Willy

    2007-05-01

    Microbial fuel cells (MFCs) that remove carbon as well as nitrogen compounds out of wastewater are of special interest for practice. We developed a MFC in which microorganisms in the cathode performed a complete denitrification by using electrons supplied by microorganisms oxidizing acetate in the anode. The MFC with a cation exchange membrane was designed as a tubular reactor with an internal cathode and was able to remove up to 0.146 kg NO(3-)-N m(-3) net cathodic compartment (NCC) d(-1) (0.080 kg NO(3-)-N m(-3) total cathodic compartment d(-1) (TCC)) at a current of 58 A m(-3) NCC (32 A m(-3) TCC) and a cell voltage of 0.075 V. The highest power output in the denitrification system was 8 W m(-3) NCC (4 W m(-3) TCC) with a cell voltage of 0.214 V and a current of 35 A m(-3) NCC. The denitrification rate and the power production was limited bythe cathodic microorganisms, which only denitrified significantly at a cathodic electrode potential below 0 V versus standard hydrogen electrode (SHE). This is, to our knowledge, the first study in which a MFC has both a biological anode and cathode performing simultaneous removal of an organic substrate, power production, and complete denitrification without relying on H2-formation or external added power.

  3. Fermentation temperature modulates phosphatidylethanolamine and phosphatidylinositol levels in the cell membrane of Saccharomyces cerevisiae.

    PubMed

    Henderson, Clark M; Zeno, Wade F; Lerno, Larry A; Longo, Marjorie L; Block, David E

    2013-09-01

    During alcoholic fermentation, Saccharomyces cerevisiae is exposed to a host of environmental and physiological stresses. Extremes of fermentation temperature have previously been demonstrated to induce fermentation arrest under growth conditions that would otherwise result in complete sugar utilization at "normal" temperatures and nutrient levels. Fermentations were carried out at 15°C, 25°C, and 35°C in a defined high-sugar medium using three Saccharomyces cerevisiae strains with diverse fermentation characteristics. The lipid composition of these strains was analyzed at two fermentation stages, when ethanol levels were low early in stationary phase and in late stationary phase at high ethanol concentrations. Several lipids exhibited dramatic differences in membrane concentration in a temperature-dependent manner. Principal component analysis (PCA) was used as a tool to elucidate correlations between specific lipid species and fermentation temperature for each yeast strain. Fermentations carried out at 35°C exhibited very high concentrations of several phosphatidylinositol species, whereas at 15°C these yeast strains exhibited higher levels of phosphatidylethanolamine and phosphatidylcholine species with medium-chain fatty acids. Furthermore, membrane concentrations of ergosterol were highest in the yeast strain that experienced stuck fermentations at all three temperatures. Fluorescence anisotropy measurements of yeast cell membrane fluidity during fermentation were carried out using the lipophilic fluorophore diphenylhexatriene. These measurements demonstrate that the changes in the lipid composition of these yeast strains across the range of fermentation temperatures used in this study did not significantly affect cell membrane fluidity. However, the results from this study indicate that fermenting S. cerevisiae modulates its membrane lipid composition in a temperature-dependent manner.

  4. Fermentation Temperature Modulates Phosphatidylethanolamine and Phosphatidylinositol Levels in the Cell Membrane of Saccharomyces cerevisiae

    PubMed Central

    Henderson, Clark M.; Zeno, Wade F.; Lerno, Larry A.; Longo, Marjorie L.

    2013-01-01

    During alcoholic fermentation, Saccharomyces cerevisiae is exposed to a host of environmental and physiological stresses. Extremes of fermentation temperature have previously been demonstrated to induce fermentation arrest under growth conditions that would otherwise result in complete sugar utilization at “normal” temperatures and nutrient levels. Fermentations were carried out at 15°C, 25°C, and 35°C in a defined high-sugar medium using three Saccharomyces cerevisiae strains with diverse fermentation characteristics. The lipid composition of these strains was analyzed at two fermentation stages, when ethanol levels were low early in stationary phase and in late stationary phase at high ethanol concentrations. Several lipids exhibited dramatic differences in membrane concentration in a temperature-dependent manner. Principal component analysis (PCA) was used as a tool to elucidate correlations between specific lipid species and fermentation temperature for each yeast strain. Fermentations carried out at 35°C exhibited very high concentrations of several phosphatidylinositol species, whereas at 15°C these yeast strains exhibited higher levels of phosphatidylethanolamine and phosphatidylcholine species with medium-chain fatty acids. Furthermore, membrane concentrations of ergosterol were highest in the yeast strain that experienced stuck fermentations at all three temperatures. Fluorescence anisotropy measurements of yeast cell membrane fluidity during fermentation were carried out using the lipophilic fluorophore diphenylhexatriene. These measurements demonstrate that the changes in the lipid composition of these yeast strains across the range of fermentation temperatures used in this study did not significantly affect cell membrane fluidity. However, the results from this study indicate that fermenting S. cerevisiae modulates its membrane lipid composition in a temperature-dependent manner. PMID:23811519

  5. Types of cell death and methods of their detection in yeast Saccharomyces cerevisiae.

    PubMed

    Wloch-Salamon, D M; Bem, A E

    2013-02-01

    The occurrence of programmed cell death in unicellular organisms is a subject that arouses great interest of theoreticians and experimental scientists. Already found evolutionarily conserved genes and metabolic pathways confirmed its existence in yeast, protozoa and even bacteria. In the yeast Saccharomyces cerevisiae, at least three main types of death are distinguished: apoptosis, necrosis and autophagy. Their classification suggested by the Nomenclature Committee on Cell Death initially based on the morphological characteristics has now been extended to include the measurable biochemical characteristics. Several laboratory methods previously used to detect the types of cell death of higher eucaryotes and later developed and successfully used for the analysis of yeast cells are here critically reviewed. Their advantages and limitations are described.

  6. The immunosuppressant SR 31747 blocks cell proliferation by inhibiting a steroid isomerase in Saccharomyces cerevisiae.

    PubMed Central

    Silve, S; Leplatois, P; Josse, A; Dupuy, P H; Lanau, C; Kaghad, M; Dhers, C; Picard, C; Rahier, A; Taton, M; Le Fur, G; Caput, D; Ferrara, P; Loison, G

    1996-01-01

    SR 31747 is a novel immunosuppressant agent that arrests cell proliferation in the yeast Saccharomyces cerevisiae, SR 31747-treated cells accumulate the same aberrant sterols as those found in a mutant impaired in delta 8- delta 7-sterol isomerase. Sterol isomerase activity is also inhibited by SR 31747 in in vitro assays. Overexpression of the sterol isomerase-encoding gene, ERG2, confers enhanced SR resistance. Cells growing anaerobically on ergosterol-containing medium are not sensitive to SR. Disruption of the sterol isomerase-encoding gene is lethal in cells growing in the absence of exogenous ergosterol, except in SR-resistant mutants lacking either the SUR4 or the FEN1 gene product. The results suggest that sterol isomerase is the target of SR 31747 and that both the SUR4 and FEN1 gene products are required to mediate the proliferation arrest induced by ergosterol depletion. PMID:8649379

  7. Permeabilization of yeast Saccharomyces cerevisiae cell walls using nanosecond high power electrical pulses

    NASA Astrophysics Data System (ADS)

    Stirke, A.; Zimkus, A.; Balevicius, S.; Stankevic, V.; Ramanaviciene, A.; Ramanavicius, A.; Zurauskiene, N.

    2014-12-01

    The electrical field-induced changes of the yeast Saccharomyces cerevisiae cells permeabilization to tetraphenylphosphonium (TPP+) ions were studied using square-shaped, nanosecond duration high power electrical pulses. It was obtained that pulses having durations ranging from 10 ns to 60 ns, and generating electric field strengths up to 190 kV/cm significantly (up to 65 times) increase the absorption rate of TPP+ ions without any detectible influence on the yeast cell viability. The modelling of the TPP+ absorption process using a second order rate equation demonstrates that depending on the duration of the pulses, yeast cell clusters of different sizes are homogeniously permeabilized. It was concluded, that nanosecond pulse-induced permeabilization can be applied to increase the operational speed of whole cell biosensors.

  8. Yeast and carbon nanotube based biocatalyst developed by synergetic effects of covalent bonding and hydrophobic interaction for performance enhancement of membraneless microbial fuel cell.

    PubMed

    Christwardana, Marcelinus; Kwon, Yongchai

    2017-02-01

    Membraneless microbial fuel cell (MFC) employing new microbial catalyst formed as yeast cultivated from Saccharomyces cerevisiae and carbon nanotube (yeast/CNT) is suggested. To analyze its catalytic activity and performance and stability of MFC, several characterizations are performed. According to the characterizations, the catalyst shows excellent catalytic activities by facile transfer of electrons via reactions of NAD, FAD, cytochrome c and cytochrome a3, while it induces high maximum power density (MPD) (344mW·m(-2)). It implies that adoption of yeast induces increases in catalytic activity and MFC performance. Furthermore, MPD is maintained to 86% of initial value even after eight days, showing excellent MFC stability.

  9. Display of wasp venom allergens on the cell surface of Saccharomyces cerevisiae

    PubMed Central

    2010-01-01

    Background Yeast surface display is a technique, where the proteins of interest are expressed as fusions with yeast surface proteins and thus remain attached to the yeast cell wall after expression. Our purpose was to study whether allergens expressed on the cell surface of baker's yeast Saccharomyces cerevisiae preserve their native allergenic properties and whether the yeast native surface glycoproteins interfere with IgE binding. We chose to use the major allergens from the common wasp Vespula vulgaris venom: phospholipase A1, hyaluronidase and antigen 5 as the model. Results The proteins were expressed on the surface as fusions with a-agglutinin complex protein AGA2. The expression was confirmed by fluorescent cytometry (FACS) after staining the cells with antibody against a C-tag attached to the C-terminal end of the allergens. Phospholipase A1 and hyaluronidase retained their enzymatic activities. Phospholipase A1 severely inhibited the growth of the yeast cells. Antigen 5 - expressing yeast cells bound IgE antibodies from wasp venom allergic patient sera but not from control sera as demonstrated by FACS. Moreover, antigen 5 - expressing yeast cells were capable of mediating allergen-specific histamine release from human basophils. Conclusions All the three major wasp venom allergens were expressed on the yeast surface. A high-level expression, which was observed only for antigen 5, was needed for detection of IgE binding by FACS and for induction of histamine release. The non-modified S. cerevisiae cells did not cause any unspecific reaction in FACS or histamine release assay despite the expression of high-mannose oligosaccharides. In perspective the yeast surface display may be used for allergen discovery from cDNA libraries and possibly for sublingual immunotherapy as the cells can serve as good adjuvant and can be produced in large amounts at a low price. PMID:20868475

  10. Adsorption of Zearalenone by beta-D-glucans in the Saccharomyces cerevisiae cell wall.

    PubMed

    Yiannikouris, A; François, J; Poughon, L; Dussap, C G; Bertin, G; Jeminet, G; Jouany, J P

    2004-06-01

    Cell walls of yeasts and bacteria are able to complex with mycotoxins and limit their bioavailability in the digestive tract when these yeasts and bacteria are given as feed additives to animals. To identify the component(s) of the yeast cell wall and the chemical interaction(s) involved in complex formation with zearalenone, four strains of Saccharomyces cerevisiae differing in their cell wall glucan and mannan content were tested. Laboratory strains wt292, fks1, and mnn9 were compared with industrial S. cerevisiae strain sc1026. The complex-forming capacity of the yeast cell walls was determined in vitro by modelling the plots of amount of toxin bound versus amount of toxin added using Hill's model. A cooperative relationship between toxin and adsorbent was shown, and a correlation between the amount of beta-D-glucans in cell walls and complex-forming efficacy was revealed (R2 = 0.889). Cell walls of strains wt292 and mnn9, which have higher levels of beta-D-glucans, were able to complex larger amounts of zearalenone, with higher association constants and higher affinity rates than those of the fks1 and sc1026 strains. The high chitin content in strains mnn9 and fks1 increased the alkali insolubility of beta-D-glucans from isolated cell walls and decreased the flexibility of these cell walls, which restricted access of zearalenone to the chemical sites of the beta-D-glucans involved in complex formation. The strains with high chitin content thus had a lower complex-forming capacity than expected based on their beta-D-glucans content. Cooperativity and the three-dimensional structure of beta-D-glucans indicate that weak noncovalent bonds are involved in the complex-forming mechanisms associated with zearalenone. The chemical interactions between beta-D-glucans and zearalenone are therefore more of an adsorption type than a binding type.

  11. Performance and microbial diversity of palm oil mill effluent microbial fuel cell.

    PubMed

    Jong, B C; Liew, P W Y; Lebai Juri, M; Kim, B H; Mohd Dzomir, A Z; Leo, K W; Awang, M R

    2011-12-01

    To evaluate the bioenergy generation and the microbial community structure from palm oil mill effluent using microbial fuel cell. Microbial fuel cells enriched with palm oil mill effluent (POME) were employed to harvest bioenergy from both artificial wastewater containing acetate and complex POME. The microbial fuel cell (MFC) showed maximum power density of 3004 mW m(-2) after continuous feeding with artificial wastewater containing acetate substrate. Subsequent replacement of the acetate substrate with complex substrate of POME recorded maximum power density of 622 mW m(-2). Based on 16S rDNA analyses, relatively higher abundance of Deltaproteobacteria (88.5%) was detected in the MFCs fed with acetate artificial wastewater as compared to POME. Meanwhile, members of Gammaproteobacteria, Epsilonproteobacteria and Betaproteobacteria codominated the microbial consortium of the MFC fed with POME with 21, 20 and 18.5% abundances, respectively. Enriched electrochemically active bacteria originated from POME demonstrated potential to generate bioenergy from both acetate and complex POME substrates. Further improvements including the development of MFC systems that are able to utilize both fermentative and nonfermentative substrates in POME are needed to maximize the bioenergy generation. A better understanding of microbial structure is critical for bioenergy generation from POME using MFC. Data obtained in this study improve our understanding of microbial community structure in conversion of POME to electricity. © 2011 The Authors. Letters in Applied Microbiology © 2011 The Society for Applied Microbiology.

  12. Microbial community analysis of a single chamber microbial fuel cell using potato wastewater.

    PubMed

    Li, Zhen; Haynes, Rishika; Sato, Eugene; Shields, Malcolm S; Fujita, Yoshiko; Sato, Chikashi

    2014-04-01

    Microbial fuel cells (MFCs) convert chemical energy to electrical energy via bio-electrochemical reactions mediated by microorganisms. This study investigated the diversity of the microbial community in an air cathode single chamber MFC that used potato-process wastewater as substrate. Terminal restriction fragment length polymorphism results indicated that the bacterial communities on the anode, cathode, control electrode, and MFC bulk fluid were similar, but differed dramatically from that of the anaerobic domestic sludge and potato wastewater inoculum. The 16S ribosomal DNA sequencing results showed that microbial species detected on the anode were predominantly within the phyla of Proteobacteria, Firmicutes, and Bacteroidetes. Fluorescent microscopy results indicated that there was a clear enhancement of biofilm formation on the anode. Results of this study could help improve understanding of the complexity of microbial communities and optimize the microbial composition for generating electricity by MFCs that use potato wastewater.

  13. Combining microbial cultures for efficient production of electricity from butyrate in a microbial electrochemical cell

    PubMed Central

    Miceli, Joseph F.; Garcia-Peña, Ines; Parameswaran, Prathap; Torres, César I.; Krajmalnik-Brown, Rosa

    2014-01-01

    Butyrate is an important product of anaerobic fermentation; however, it is not directly used by characterized strains of the highly efficient anode respiring bacteria (ARB) Geobacter sulfurreducens in microbial electrochemical cells. By combining a butyrate-oxidizing community with a Geobacter rich culture, we generated a microbial community which outperformed many naturally derived communities found in the literature for current production from butyrate and rivaled the highest performing natural cultures in terms of current density (~11 A/m2) and Coulombic efficiency (~70%). Microbial community analyses support the shift in the microbial community from one lacking efficient ARB in the marine hydrothermal vent community to a community consisting of ~80% Geobacter in the anode biofilm. This demonstrates the successful production and adaptation of a novel microbial culture for generating electrical current from butyrate with high current density and high Coulombic efficiency, by combining two mixed micro bial cultures containing complementing biochemical pathways. PMID:25048958

  14. Microbial Community Analysis of a Single Chamber Microbial Fuel Cell Using Potato Wastewater

    SciTech Connect

    Zhen Li; Rishika Haynes; Eugene Sato; Malcolm Shields; Yoshiko Fujita; Chikashi Sato

    2014-04-01

    Microbial fuel cells (MFCs) convert chemical energy to electrical energy via bioelectrochemical reactions mediated by microorganisms. We investigated the diversity of the microbial community in an air cathode single chamber MFC that utilized potato-process wastewater as substrate. Terminal Restriction Fragment Length Polymorphism (T-RFLP) results indicated that the bacterial communities on the anode, cathode, control electrode, and MFC bulk fluid were similar, but differed dramatically from that of the anaerobic domestic sludge and potato wastewater inoculum. The 16S rDNA sequencing results showed that microbial species detected on the anode were predominantly within the phyla of Proteobacteria, Firmicutes, and Bacteroidetes. Fluorescent microscopy results indicated that there was a clear enhancement of biofilm formation on the anode. Results of this study could help improve understanding of the complexity of microbial communities and optimize the microbial composition for generating electricity by MFCs that utilize potato wastewater.

  15. Changes in reactive oxygen species begin early during replicative aging of Saccharomyces cerevisiae cells.

    PubMed

    Lam, Yuen T; Aung-Htut, May T; Lim, Yu L; Yang, Hongyuan; Dawes, Ian W

    2011-04-15

    Increased reactive oxygen species (ROS) are a feature of aging cells, but little is known about when ROS generation begins as cells age. Here we show how ROS change in Saccharomyces cerevisiae cells throughout their early replicative life span using the fluorescent ROS indicator dihydroethidium (DHE), which has some specificity for the superoxide anion. Cells in a particular age range were heterogeneous with respect to their ROS burden. Surprisingly, some cells as young as 5-7 generations acquired a greatly increased level of ROS detected by DHE relative to virgin cells. By 12 generations 50% of cells had a substantial ROS burden despite being only halfway through their life span. In contrast to the wild type, cells of a sir2 mutant had lower levels of ROS reacting with DHE. Daughters from older mothers had low ROS levels, and this asymmetric distribution of ROS was SIR2-independent. Mitochondrial fragmentation also began to occur in cells after 4 generations and increased markedly as cells aged. Daughter cells regenerated normal tubular mitochondria despite the fragmentation of mitochondria in the mother cells, whereas daughters of the sir2 mutant had fragmented mitochondria at all ages.

  16. Comparative study of stability of soluble and cell wall invertase from Saccharomyces cerevisiae.

    PubMed

    Margetić, Aleksandra; Vujčić, Zoran

    2017-03-16

    Yeast Saccharomyces cerevisiae is the most significant source of enzyme invertase. It is mainly used in the food industry as a soluble or immobilized enzyme. The greatest amount of invertase is located in the periplasmic space in yeast. In this work, it was isolated into two forms of enzyme from yeast S. cerevisiae cell, soluble and cell wall invertase (CWI). Both forms of enzyme showed same temperature optimum (60°C), similar pH optimum, and kinetic parameters. The significant difference between these biocatalysts was observed in their thermal stability, stability in urea and methanol solution. At 60°C, CWI had 1.7 times longer half-life than soluble enzyme, while at 70°C CWI showed 8.7 times longer half-life than soluble enzyme. After 2-hr of incubation in 8 M urea solution, soluble invertase and CWI retained 10 and 60% of its initial activity, respectively. During 22 hr of incubation of both enzymes in 30 and 40% methanol, soluble invertase was completely inactivated, while CWI changed its activity within the experimental error. Therefore, soluble invertase and CWI have not shown any substantial difference, but CWI showed better thermal stability and stability in some of the typical protein-denaturing agents.

  17. Over-pressurized bioreactors: application to microbial cell cultures.

    PubMed

    Lopes, Marlene; Belo, Isabel; Mota, Manuel

    2014-01-01

    In industrial biotechnology, microbial cultures are exposed to different local pressures inside bioreactors. Depending on the microbial species and strains, the increased pressure may have detrimental or beneficial effects on cellular growth and product formation. In this review, the effects of increased air pressure on various microbial cultures growing in bioreactors under moderate total pressure conditions (maximum, 15 bar) will be discussed. Recent data illustrating the diversity of increased air pressure effects at different levels in microbial cells cultivation will be presented, with particular attention to the effects of oxygen and carbon dioxide partial pressures on cellular growth and product formation, and the concomitant effect of oxygen pressure on antioxidant cellular defense mechanisms.

  18. Saccharomyces Cerevisiae Cell Wall Components as Tools for Ochratoxin A Decontamination

    PubMed Central

    Piotrowska, Małgorzata; Masek, Anna

    2015-01-01

    The aim of this study was to evaluate the usefulness of Saccharomyces cerevisiae cell wall preparations in the adsorption of ochratoxin A (OTA). The study involved the use of a brewer’s yeast cell wall devoid of protein substances, glucans obtained by water and alkaline extraction, a glucan commercially available as a dietary supplement for animals and, additionally, dried brewer’s yeast for comparison. Fourier Transform Infrared (FTIR) analysis of the obtained preparations showed bands characteristic for glucans in the resulting spectra. The yeast cell wall preparation, water-extracted glucan and the commercial glucan bound the highest amount of ochratoxin A, above 55% of the initial concentration, and the alkaline-extracted glucan adsorbed the lowest amount of this toxin. It has been shown that adsorption is most effective at a close-to-neutral pH, while being considerably limited in alkaline conditions. PMID:25848694

  19. The Saccharomyces cerevisiae Wss1 protein is only present in mother cells.

    PubMed

    van Heusden, G Paul H; Steensma, H Yde

    2008-05-01

    The Saccharomyces cerevisiae WSS1 (Weak Suppressor of Smt3) gene has initially been identified as a multicopy suppressor of a mutation in SMT3 encoding the small ubiquitin-like modifier. Later, multiple functions related to DNA replication and repair have been found for WSS1. Here, we report the subcellular location of the Wss1 protein. Fluorescence microscopy of strains expressing a Wss1p-green fluorescent protein (GFP) fusion shows that the protein is present in a single sharp spot near the nuclear membrane, distinct from the spindle pole bodies and nucleolus. In dividing cells, the spot is exclusively present in the mother cell, suggesting a mother cell-specific function of WSS1.

  20. Enzymatic process for the fractionation of baker's yeast cell wall (Saccharomyces cerevisiae).

    PubMed

    Borchani, Chema; Fonteyn, Fabienne; Jamin, Guilhem; Paquot, Michel; Blecker, Christophe; Thonart, Philippe

    2014-11-15

    β-Glucans, homopolymers of glucose, are widespread in many microorganisms, mushrooms and plants. They have attracted attention because of their bioactive and medicinal functions. One important source of β-glucans is the cell wall of yeasts, especially that of baker's yeast Saccharomyces cerevisiae. Several processes for the isolation of β-glucans, using alkali, acid or a combination of both, result in degradation of the polymeric chains. In this paper, we have an enzymatic process for the isolation of glucans from yeast cell walls. As a result, β-glucans were obtained in a yield of 18.0% of the original ratio in the yeast cell walls. Therefore, this isolation process gave a better yield and higher β-glucan content than did traditional isolation methods. Furthermore, results showed that each extraction step of β-glucan had a significant effects on its chemical properties. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Physiological responses to acid stress by Saccharomyces cerevisiae when applying high initial cell density

    PubMed Central

    Guo, Zhong-peng; Olsson, Lisbeth

    2016-01-01

    High initial cell density is used to increase volumetric productivity and shorten production time in lignocellulosic hydrolysate fermentation. Comparison of physiological parameters in high initial cell density cultivation of Saccharomyces cerevisiae in the presence of acetic, formic, levulinic and cinnamic acids demonstrated general and acid-specific responses of cells. All the acids studied impaired growth and inhibited glycolytic flux, and caused oxidative stress and accumulation of trehalose. However, trehalose may play a role other than protecting yeast cells from acid-induced oxidative stress. Unlike the other acids, cinnamic acid did not cause depletion of cellular ATP, but abolished the growth of yeast on ethanol. Compared with low initial cell density, increasing initial cell density reduced the lag phase and improved the bioconversion yield of cinnamic acid during acid adaptation. In addition, yeast cells were able to grow at elevated concentrations of acid, probable due to the increase in phenotypic cell-to-cell heterogeneity in large inoculum size. Furthermore, the specific growth rate and the specific rates of glucose consumption and metabolite production were significantly lower than at low initial cell density, which was a result of the accumulation of a large fraction of cells that persisted in a viable but non-proliferating state. PMID:27620460

  2. Formaldehyde fixation is detrimental to actin cables in glucose-depleted S. cerevisiae cells

    PubMed Central

    Vasicova, Pavla; Rinnerthaler, Mark; Haskova, Danusa; Novakova, Lenka; Malcova, Ivana; Breitenbach, Michael; Hasek, Jiri

    2016-01-01

    Actin filaments form cortical patches and emanating cables in fermenting cells of Saccharomyces cerevisiae. This pattern has been shown to be depolarized in glucose-depleted cells after formaldehyde fixation and staining with rhodamine-tagged phalloidin. Loss of actin cables in mother cells was remarkable. Here we extend our knowledge on actin in live glucose-depleted cells co-expressing the marker of actin patches (Abp1-RFP) with the marker of actin cables (Abp140-GFP). Glucose depletion resulted in appearance of actin patches also in mother cells. However, even after 80 min of glucose deprivation these cells showed a clear network of actin cables labeled with Abp140-GFP in contrast to previously published data. In live cells with a mitochondrial dysfunction (rho0 cells), glucose depletion resulted in almost immediate appearance of Abp140-GFP foci partially overlapping with Abp1-RFP patches in mother cells. Residual actin cables were clustered in patch-associated bundles. A similar overlapping “patchy” pattern of both actin markers was observed upon treatment of glucose-deprived rho+ cells with FCCP (the inhibitor of oxidative phosphorylation) and upon treatment with formaldehyde. While the formaldehyde-targeted process stays unknown, our results indicate that published data on yeast actin cytoskeleton obtained from glucose-depleted cells after fixation should be considered with caution.

  3. Recovery of Saccharomyces cerevisiae mating-type a cells from G1 arrest by alpha factor.

    PubMed Central

    Chan, R K

    1977-01-01

    Mating-type a cells of the yeast Saccharomyces cerevisiae that had been specifically arrested in the G1 phase of the cell cycle by alpha factor, an oligopeptide pheromone made by alpha cells, recovered and resumed cell division after a period of inhibition which was dependent on the concentration of alpha factor used. These treated a cells were more resistant to alpha factor than untreated a cells, but lost their resistance upon further cell division. However, cells arrested for 6 h were no more resistant to alpha factor than cells arrested for only 2.5 h. Mating-type a strains could inactivate or remove alpha factor from the culture fluid, but two a sterile (nonmating) mutants and an a/alpha diploid strain could not. These results suggest that a cells have a mechanism, which may involve uptake or inactivation of alpha factor, for recovering from alpha factor arrest. However, the results do not distinguish between a recovery mechanism which is constitutive and one which is induced by alpha factor. The loss of alpha factor activity during recovery appeared to be primarily cell contact mediated, although an extracellular, diffusible inhibitor of alpha factor that is labile or that functions stoichiometrically could not be ruled out. PMID:400792

  4. Physiological responses to acid stress by Saccharomyces cerevisiae when applying high initial cell density.

    PubMed

    Guo, Zhong-Peng; Olsson, Lisbeth

    2016-11-01

    High initial cell density is used to increase volumetric productivity and shorten production time in lignocellulosic hydrolysate fermentation. Comparison of physiological parameters in high initial cell density cultivation of Saccharomyces cerevisiae in the presence of acetic, formic, levulinic and cinnamic acids demonstrated general and acid-specific responses of cells. All the acids studied impaired growth and inhibited glycolytic flux, and caused oxidative stress and accumulation of trehalose. However, trehalose may play a role other than protecting yeast cells from acid-induced oxidative stress. Unlike the other acids, cinnamic acid did not cause depletion of cellular ATP, but abolished the growth of yeast on ethanol. Compared with low initial cell density, increasing initial cell density reduced the lag phase and improved the bioconversion yield of cinnamic acid during acid adaptation. In addition, yeast cells were able to grow at elevated concentrations of acid, probable due to the increase in phenotypic cell-to-cell heterogeneity in large inoculum size. Furthermore, the specific growth rate and the specific rates of glucose consumption and metabolite production were significantly lower than at low initial cell density, which was a result of the accumulation of a large fraction of cells that persisted in a viable but non-proliferating state. © FEMS 2016.

  5. Human lactoferrin triggers a mitochondrial- and caspase-dependent regulated cell death in Saccharomyces cerevisiae.

    PubMed

    Acosta-Zaldívar, M; Andrés, M T; Rego, A; Pereira, C S; Fierro, J F; Côrte-Real, M

    2016-02-01

    We have previously shown that the antifungal activity of human lactoferrin (hLf) against Candida albicans relies on its ability to induce cell death associated with apoptotic markers. To gain a deeper understanding of the mechanisms underlying hLf-induced apoptosis, we characterized this cell death process in the well-established Saccharomyces cerevisiae model. Our results indicate that hLf induces cell death in S. cerevisiae in a manner that requires energy and de novo protein synthesis. Cell death is associated with nuclear chromatin condensation, preservation of plasma membrane integrity, and is Yca1p metacaspase-dependent. Lactoferrin also caused mitochondrial dysfunction associated with ROS accumulation and release of cytochrome c. Pre-incubation with oligomycin, an oxidative phosphorylation inhibitor, increased resistance to hLf and, accordingly, mutants deficient in the F1F0-ATP synthase complex were more resistant to death induced by hLf. This indicates that mitochondrial energetic metabolism plays a key role in the killing effect of hLf, though a direct role of F1F0-ATP synthase cannot be precluded. Overexpression of the anti-apoptotic protein Bcl-xL or pre-incubation with N-acetyl cysteine reduced the intracellular level of ROS and increased resistance to hLf, confirming a ROS-mediated mitochondrial cell death process. Mitochondrial involvement was further reinforced by the higher resistance of cells lacking mitochondrial DNA, or other known yeast mitochondrial apoptosis regulators, such as, Aif1p, Cyc3p and Aac1/2/3p. This study provides new insights into a detailed understanding at the molecular level of hLf-induced apoptosis, which may allow the design of new strategies to overcome the emergence of resistance of clinically relevant fungi to conventional antifungals.

  6. Impact of Ferrous Iron on Microbial Community of the Biofilm in Microbial Fuel Cells.

    PubMed

    Liu, Qian; Liu, Bingfeng; Li, Wei; Zhao, Xin; Zuo, Wenjing; Xing, Defeng

    2017-01-01

    The performance of microbial electrochemical cells depends upon microbial community structure and metabolic activity of the electrode biofilms. Iron as a signal affects biofilm development and enrichment of exoelectrogenic bacteria. In this study, the effect of ferrous iron on microbial communities of the electrode biofilms in microbial fuel cells (MFCs) was investigated. Voltage production showed that ferrous iron of 100 μM facilitated MFC start-up compared to 150 μM, 200 μM, and without supplement of ferrous iron. However, higher concentration of ferrous iron had an inhibitive influence on current generation after 30 days of operation. Illumina Hiseq sequencing of 16S rRNA gene amplicons indicated that ferrous iron substantially changed microbial community structures of both anode and cathode biofilms. Principal component analysis showed that the response of microbial communities of the anode biofilms to higher concentration of ferrous iron was more sensitive. The majority of predominant populations of the anode biofilms in MFCs belonged to Geobacter, which was different from the populations of the cathode biofilms. An obvious shift of community structures of the cathode biofilms occurred after ferrous iron addition. This study implied that ferrous iron influenced the power output and microbial community of MFCs.

  7. Impact of Ferrous Iron on Microbial Community of the Biofilm in Microbial Fuel Cells

    PubMed Central

    Liu, Qian; Liu, Bingfeng; Li, Wei; Zhao, Xin; Zuo, Wenjing; Xing, Defeng

    2017-01-01

    The performance of microbial electrochemical cells depends upon microbial community structure and metabolic activity of the electrode biofilms. Iron as a signal affects biofilm development and enrichment of exoelectrogenic bacteria. In this study, the effect of ferrous iron on microbial communities of the electrode biofilms in microbial fuel cells (MFCs) was investigated. Voltage production showed that ferrous iron of 100 μM facilitated MFC start-up compared to 150 μM, 200 μM, and without supplement of ferrous iron. However, higher concentration of ferrous iron had an inhibitive influence on current generation after 30 days of operation. Illumina Hiseq sequencing of 16S rRNA gene amplicons indicated that ferrous iron substantially changed microbial community structures of both anode and cathode biofilms. Principal component analysis showed that the response of microbial communities of the anode biofilms to higher concentration of ferrous iron was more sensitive. The majority of predominant populations of the anode biofilms in MFCs belonged to Geobacter, which was different from the populations of the cathode biofilms. An obvious shift of community structures of the cathode biofilms occurred after ferrous iron addition. This study implied that ferrous iron influenced the power output and microbial community of MFCs. PMID:28638368

  8. Power overshoot in two-chambered microbial fuel cell (MFC).

    PubMed

    Nien, Po-Chin; Lee, Chin-Yu; Ho, Kuo-Chuan; Adav, Sunil S; Liu, Lihong; Wang, Aijie; Ren, Nanqi; Lee, Duu-Jong

    2011-04-01

    A two-chamber microbial fuel cell was started using iron-reducing strains as inoculum and acetate as carbon sources. The tested microbial fuel cell had an open-circuit voltage of 0.67 V, and reached 1045 mA m(-2) and a power density of 486 mW m(-2) at 0.46 V before power overshoot occurred. Anodic reactions were identified as the rate-determining steps. Stirring the anolyte insignificantly increased cell performance, suggesting a minimal external mass transfer resistance from the anolyte to the anodic biofilm. Data regression analysis indicates that charge transfer resistance at the biofilm-anode junction was negligible. The order of magnitude estimation of electrical conductance indicates that electron transfer resistance had an insignificant effect on microbial fuel cell performance. Resistance in electrogens for substrate utilization is proposed to induce microbial fuel cell power overshoot.

  9. Microbial community structure elucidates performance of Glyceria maxima plant microbial fuel cell.

    PubMed

    Timmers, Ruud A; Rothballer, Michael; Strik, David P B T B; Engel, Marion; Schulz, Stephan; Schloter, Michael; Hartmann, Anton; Hamelers, Bert; Buisman, Cees

    2012-04-01

    The plant microbial fuel cell (PMFC) is a technology in which living plant roots provide electron donor, via rhizodeposition, to a mixed microbial community to generate electricity in a microbial fuel cell. Analysis and localisation of the microbial community is necessary for gaining insight into the competition for electron donor in a PMFC. This paper characterises the anode-rhizosphere bacterial community of a Glyceria maxima (reed mannagrass) PMFC. Electrochemically active bacteria (EAB) were located on the root surfaces, but they were more abundant colonising the graphite granular electrode. Anaerobic cellulolytic bacteria dominated the area where most of the EAB were found, indicating that the current was probably generated via the hydrolysis of cellulose. Due to the presence of oxygen and nitrate, short-chain fatty acid-utilising denitrifiers were the major competitors for the electron donor. Acetate-utilising methanogens played a minor role in the competition for electron donor, probably due to the availability of graphite granules as electron acceptors.

  10. Anodic and cathodic microbial communities in single chamber microbial fuel cells.

    PubMed

    Daghio, Matteo; Gandolfi, Isabella; Bestetti, Giuseppina; Franzetti, Andrea; Guerrini, Edoardo; Cristiani, Pierangela

    2015-01-25

    Microbial fuel cells (MFCs) are a rapidly growing technology for energy production from wastewater and biomasses. In a MFC, a microbial biofilm oxidizes organic matter and transfers electrons from reduced compounds to an anode as the electron acceptor by extracellular electron transfer (EET). The aim of this work was to characterize the microbial communities operating in a Single Chamber Microbial Fuel Cell (SCMFC) fed with acetate and inoculated with a biogas digestate in order to gain more insight into anodic and cathodic EET. Taxonomic characterization of the communities was carried out by Illumina sequencing of a fragment of the 16S rRNA gene. Microorganisms belonging to Geovibrio genus and purple non-sulfur (PNS) bacteria were found to be dominant in the anodic biofilm. The alkaliphilic genus Nitrincola and anaerobic microorganisms belonging to Porphyromonadaceae family were the most abundant bacteria in the cathodic biofilm.

  11. Enhanced cell-surface display and secretory production of cellulolytic enzymes with Saccharomyces cerevisiae Sed1 signal peptide.

    PubMed

    Inokuma, Kentaro; Bamba, Takahiro; Ishii, Jun; Ito, Yoichiro; Hasunuma, Tomohisa; Kondo, Akihiko

    2016-11-01

    Recombinant yeast strains displaying aheterologous cellulolytic enzymes on their cell surfaces using a glycosylphosphatidylinositol (GPI) anchoring system are a promising strategy for bioethanol production from lignocellulosic materials. A crucial step for cell wall localization of the enzymes is the intracellular transport of proteins in yeast cells. Therefore, the addition of a highly efficient secretion signal sequence is important to increase the amount of the enzymes on the yeast cell surface. In this study, we demonstrated the effectiveness of a novel signal peptide (SP) sequence derived from the Saccharomyces cerevisiae SED1 gene for cell-surface display and secretory production of cellulolytic enzymes. Gene cassettes with SP sequences derived from S. cerevisiae SED1 (SED1SP), Rhizopus oryzae glucoamylase (GLUASP), and S. cerevisiae α-mating pheromone (MFα1SP) were constructed for cell-surface display of Aspergillus aculeatus β-glucosidase (BGL1) and Trichoderma reesei endoglucanase II (EGII). These gene cassettes were integrated into the S. cerevisiae genome. The recombinant strains with the SED1SP showed higher cell-surface BGL and EG activities than those with the conventional SP sequences (GLUASP and MFα1SP). The novel SP sequence also improved the secretory production of BGL and EG in S. cerevisiae. The extracellular BGL activity of the recombinant strains with the SED1SP was 1.3- and 1.9-fold higher than the GLUASP and MFα1SP strains, respectively. Moreover, the utilization of SED1SP successfully enhanced the secretory production of BGL in Pichia pastoris. The utilization of the novel SP sequence is a promising option for highly efficient cell-surface display and secretory production of heterologous proteins in various yeast species. Biotechnol. Bioeng. 2016;113: 2358-2366. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  12. Visualization of calcium and zinc ions in Saccharomyces cerevisiae cells treated with PEFs (pulse electric fields) by laser confocal microscopy.

    PubMed

    Urszula, Pankiewicz; Jerzy, Jamroz; Sujka, Monika; Kowalski, Radosław

    2015-12-01

    The aim of the present work was to visualize the areas of increased concentration of calcium and zinc ions inside Saccharomyces cerevisiae cells with the use of confocal microscopy and to make an attempt to asses semi-quantitatively their concentration within the limits of the cells. Semi-quantitative analysis revealed that fluorescence inside cells from control samples was three-times lower than that observed for cells from the sample enriched with calcium. Differences in distribution of fluorescence intensity between cells originated from the samples enriched with zinc and control samples were also observed. On the basis of the optical sections, the 3D reconstructions of ion-rich areas distribution in the cell were made. The obtained results showed that confocal microscopy is a useful technique for visualization of the areas in S. cerevisiae cells which contain higher amount of calcium and zinc and it may be also used for semi-quantitative analysis.

  13. AC power generation from microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Lobo, Fernanda Leite; Wang, Heming; Forrestal, Casey; Ren, Zhiyong Jason

    2015-11-01

    Microbial fuel cells (MFCs) directly convert biodegradable substrates to electricity and carry good potential for energy-positive wastewater treatment. However, the low and direct current (DC) output from MFC is not usable for general electronics except small sensors, yet commercial DC-AC converters or inverters used in solar systems cannot be directly applied to MFCs. This study presents a new DC-AC converter system for MFCs that can generate alternating voltage in any desired frequency. Results show that AC power can be easily achieved in three different frequencies tested (1, 10, 60 Hz), and no energy storage layer such as capacitors was needed. The DC-AC converter efficiency was higher than 95% when powered by either individual MFCs or simple MFC stacks. Total harmonic distortion (THD) was used to investigate the quality of the energy, and it showed that the energy could be directly usable for linear electronic loads. This study shows that through electrical conversion MFCs can be potentially used in household electronics for decentralized off-grid communities.

  14. The selection of S. cerevisiae mutants defective in the start event of cell division.

    PubMed

    Reed, S I

    1980-07-01

    Thirty-three temperature-sensitive mutations defective in the start event of the cell division cycle of Saccharomyces cerevisiae were isolated and subjected to preliminary characterization. Complementation studies assigned thes mutations to four complementation groups, one of which, cdc28, has been described previously. Genetic analysis revealed that these complementation groups define single nuclear genes, unlinked to one another. One of the three newly identified genes, cdc37, has been located in the yeast linkage map on chromosome IV, two meiotic map units distal to hom2.--Each mutation produces stage-specific arrest of cell division at start, the same point where mating pheromone interrupts division. After synchronization at start by incubation at the restrictive temperature, the mutants retain the capacity to enlarge and to conjugate.

  15. Combining magnetic sorting of mother cells and fluctuation tests to analyze genome instability during mitotic cell aging in Saccharomyces cerevisiae.

    PubMed

    Patterson, Melissa N; Maxwell, Patrick H

    2014-10-16

    Saccharomyces cerevisiae has been an excellent model system for examining mechanisms and consequences of genome instability. Information gained from this yeast model is relevant to many organisms, including humans, since DNA repair and DNA damage response factors are well conserved across diverse species. However, S. cerevisiae has not yet been used to fully address whether the rate of accumulating mutations changes with increasing replicative (mitotic) age due to technical constraints. For instance, measurements of yeast replicative lifespan through micromanipulation involve very small populations of cells, which prohibit detection of rare mutations. Genetic methods to enrich for mother cells in populations by inducing death of daughter cells have been developed, but population sizes are still limited by the frequency with which random mutations that compromise the selection systems occur. The current protocol takes advantage of magnetic sorting of surface-labeled yeast mother cells to obtain large enough populations of aging mother cells to quantify rare mutations through phenotypic selections. Mutation rates, measured through fluctuation tests, and mutation frequencies are first established for young cells and used to predict the frequency of mutations in mother cells of various replicative ages. Mutation frequencies are then determined for sorted mother cells, and the age of the mother cells is determined using flow cytometry by staining with a fluorescent reagent that detects bud scars formed on their cell surfaces during cell division. Comparison of predicted mutation frequencies based on the number of cell divisions to the frequencies experimentally observed for mother cells of a given replicative age can then identify whether there are age-related changes in the rate of accumulating mutations. Variations of this basic protocol provide the means to investigate the influence of alterations in specific gene functions or specific environmental conditions on

  16. Cell-based detection of microbial biomaterial contaminations.

    PubMed

    Roch, Toralf; Ma, Nan; Kratz, Karl; Lendlein, Andreas

    2015-01-01

    A major challenge in biomaterial synthesis and functionalization is the prevention of microbial contaminations such as endotoxins (lipopolysaccharides (LPS)). In addition to LPS, which are exclusively expressed by Gram negative bacteria, also other microbial products derived from fungi or Gram positive bacteria can be found as contaminations in research laboratories. Typically, the Limulus amebocyte lysate (LAL)-test is used to determine the endotoxin levels of medical devices. However, this test fails to detect material-bound LPS and other microbial contaminations and, as demonstrated in this study, detects LPS from various bacterial species with different sensitivities.In this work, a cell-based assay using genetically engineered RAW macrophages, which detect not only soluble but also material-bound microbial contaminations is introduced.The sensitivity of this cell-line towards different LPS species and different heat-inactivated microbes was investigated. As proof of principle a soft hydrophobic poly(n-butyl acrylate) network (cPnBA), which may due to adhesive properties strongly bind microbes, was deliberately contaminated with heat-inactivated bacteria. While the LAL-test failed to detect the microbial contamination, the cell-based assay clearly detected material-bound microbial contaminations. Our data demonstrate that a cell-based detection system should routinely be used as supplement to the LAL-test to determine microbial contaminations of biomaterials.

  17. [Biomass energy utilization in microbial fuel cells: potentials and challenges].

    PubMed

    Huang, Liping; Cheng, Shaoan

    2010-07-01

    Microbial fuel cells (MFCs) that can harvest biomass energy from organic wastes through microbial catalysis have garnered more and more attention within the past decade due to its potential benefits to ecological environment. In this article, the updated progress in MFCs is reviewed, with a focus on frontier technologies such as chamber configurations, feedstock varieties and the integration of MFCs with microbial electrolysis cells for hydrogen production. And on the other hand, the challenges like development of cost-effective electrode materials, improvement of biomass energy recovery and power output, design and optimization of commercial MFC devices are presented.

  18. Microalgae-microbial fuel cell: A mini review.

    PubMed

    Lee, Duu-Jong; Chang, Jo-Shu; Lai, Juin-Yih

    2015-12-01

    Microalgae-microbial fuel cells (mMFCs) are a device that can convert solar energy to electrical energy via biological pathways. This mini-review lists new research and development works on microalgae processes, microbial fuel cell (MFC) processes, and their combined version, mMFC. The substantial improvement and technological advancement are highlighted, with a discussion on the challenges and prospects for possible commercialization of mMFC technologies.

  19. Synthesis of mannosylinositol phosphorylceramides is involved in maintenance of cell integrity of yeast Saccharomyces cerevisiae.

    PubMed

    Morimoto, Yuji; Tani, Motohiro

    2015-02-01

    Complex sphingolipids play important roles in many physiologically important events in yeast Saccharomyces cerevisiae. In this study, we screened yeast mutant strains showing a synthetic lethal interaction with loss of mannosylinositol phosphorylceramide (MIPC) synthesis and found that a specific group of glycosyltransferases involved in the synthesis of mannan-type N-glycans is essential for the growth of cells lacking MIPC synthases (Sur1 and Csh1). The genetic interaction was also confirmed by repression of MNN2, which encodes alpha-1,2-mannosyltransferase that synthesizes mannan-type N-glycans, by a tetracycline-regulatable system. MNN2-repressed sur1Δ csh1Δ cells exhibited high sensitivity to zymolyase treatment, and caffeine and sodium dodecyl sulfate (SDS) strongly inhibited the growth of sur1Δ csh1Δ cells, suggesting impairment of cell integrity due to the loss of MIPC synthesis. The phosphorylated form of Slt2, a mitogen-activated protein (MAP) kinase activated by impaired cell integrity, increased in sur1Δ csh1Δ cells, and this increase was dramatically enhanced by the repression of Mnn2. Moreover, the growth defect of MNN2-repressed sur1Δ csh1Δ cells was enhanced by the deletion of SLT2 or RLM1 encoding a downstream target of Slt2. These results indicated that loss of MIPC synthesis causes impairment of cell integrity, and this effect is enhanced by impaired synthesis of mannan-type N-glycans. © 2014 John Wiley & Sons Ltd.

  20. Cell Wall-Related Bionumbers and Bioestimates of Saccharomyces cerevisiae and Candida albicans

    PubMed Central

    de Koster, Chris G.; Brul, Stanley

    2014-01-01

    Bionumbers and bioestimates are valuable tools in biological research. Here we focus on cell wall-related bionumbers and bioestimates of the budding yeast Saccharomyces cerevisiae and the polymorphic, pathogenic fungus Candida albicans. We discuss the linear relationship between cell size and cell ploidy, the correlation between cell size and specific growth rate, the effect of turgor pressure on cell size, and the reason why using fixed cells for measuring cellular dimensions can result in serious underestimation of in vivo values. We further consider the evidence that individual buds and hyphae grow linearly and that exponential growth of the population results from regular formation of new daughter cells and regular hyphal branching. Our calculations show that hyphal growth allows C. albicans to cover much larger distances per unit of time than the yeast mode of growth and that this is accompanied by strongly increased surface expansion rates. We therefore predict that the transcript levels of genes involved in wall formation increase during hyphal growth. Interestingly, wall proteins and polysaccharides seem barely, if at all, subject to turnover and replacement. A general lesson is how strongly most bionumbers and bioestimates depend on environmental conditions and genetic background, thus reemphasizing the importance of well-defined and carefully chosen culture conditions and experimental approaches. Finally, we propose that the numbers and estimates described here offer a solid starting point for similar studies of other cell compartments and other yeast species. PMID:24243791

  1. Cellular and molecular engineering of yeast Saccharomyces cerevisiae for advanced biobutanol production.

    PubMed

    Kuroda, Kouichi; Ueda, Mitsuyoshi

    2016-02-01

    Butanol is an attractive alternative energy fuel owing to several advantages over ethanol. Among the microbial hosts for biobutanol production, yeast Saccharomyces cerevisiae has a great potential as a microbial host due to its powerful genetic tools, a history of successful industrial use, and its inherent tolerance to higher alcohols. Butanol production by S. cerevisiae was first attempted by transferring the 1-butanol-producing metabolic pathway from native microorganisms or using the endogenous Ehrlich pathway for isobutanol synthesis. Utilizing alternative enzymes with higher activity, eliminating competitive pathways, and maintaining cofactor balance achieved significant improvements in butanol production. Meeting future challenges, such as enhancing butanol tolerance and implementing a comprehensive strategy by high-throughput screening, would further elevate the biobutanol-producing ability of S. cerevisiae toward an ideal microbial cell factory exhibiting high productivity of biobutanol.

  2. Implementation of microbial fuel cell in harvesting energy using wastewater

    NASA Astrophysics Data System (ADS)

    Ramli, N. L.; Wahab, M. S. Abdul; Sharif, S. A. Md; Ramly, N. H.

    2016-02-01

    In this century, most of the companies use the electricity from the fossils fuels such as oil, gas and coal. This method will give negative impact to the environment and the fossils fuel will be run out. This project is to develop a microbial fuels cell that can produce electricity. There are several types of the microbial fuel cell, which are a single chamber, double chamber and continuous. In this paper, the double chamber microbial fuel cell was selected to investigate the effect of suspended sludge into the double chamber microbial fuels cell. The salt bridge will construct between both chambers of the double chamber microbial fuels cell. Carbon graphite rod is selected as an electrode at the cathode and anode to transfer the electron from the anode to the cathode. Electricity is generated from the anaerobic oxidation of organic matter by bacteria. At the end of this project, the microbial fuels cell was successful in generating electricity that can be used for a specific application.

  3. Direct observation of cell wall glucans in whole cells of Saccharomyces cerevisiae by magic-angle spinning 13C-NMR.

    PubMed

    Krainer, E; Stark, R E; Naider, F; Alagramam, K; Becker, J M

    1994-12-01

    Intact cells of Saccharomyces cerevisiae were examined as an aqueous paste by 13C-nmr spectroscopy with direct polarization and magic-angle spinning. The spectra obtained were highly resolved, showing numerous resonances in the 60-105 ppm range that were assigned to carbons of a liquid-like domain of the cell wall glucan. Assignments were confirmed by running the spectrum of S. cerevisiae in which the cell wall glucans were labeled with [13C] by feeding the cell [13C]galactose. The spectra indicate that the glucan in the cell wall of intact S. cerevisiae assumes a helical conformation and suggest that strain 17A fed with galactose preferentially incorporates the resulting glucose into beta (1-->3)-linkages.

  4. Invertase activity of intact cells of Saccharomyces cerevisiae growing on sugar cane molasses. 1. Steady-state continuous culture tests

    SciTech Connect

    Vitolo, M.; Vairo, M.L.R.; Borzani, W.

    1985-08-01

    During the steady-state continuous culture of Saccharomyces cerevisiae on sugar cane blackstrap molasses under different experimental conditions, oscillatory variations of the invertase activity of the intact yeast cells were observed. The continuous morphological changes of the cells wall and of the periplasmic space affecting the interaction between invertase and sucrose molecules could be responsible by the observed oscillatory phenomena. The average invertase activity at the steady state is linearly correlated to the cell's growth rate.

  5. Analysis of oxygen reduction and microbial community of air-diffusion biocathode in microbial fuel cells.

    PubMed

    Wang, Zejie; Zheng, Yue; Xiao, Yong; Wu, Song; Wu, Yicheng; Yang, Zhaohui; Zhao, Feng

    2013-09-01

    Microbes play irreplaceable role in oxygen reduction reaction of biocathode in microbial fuel cells (MFCs). In this study, air-diffusion biocathode MFCs were set up for accelerating oxygen reduction and microbial community analysis. Linear sweep voltammetry and Tafel curve confirmed the function of cathode biofilm to catalyze oxygen reduction. Microbial community analysis revealed higher diversity and richness of community in plankton than in biofilm. Proteobacteria was the shared predominant phylum in both biofilm and plankton (39.9% and 49.8%) followed by Planctomycetes (29.9%) and Bacteroidetes (13.3%) in biofilm, while Bacteroidetes (28.2%) in plankton. Minor fraction (534, 16.4%) of the total operational taxonomic units (3252) was overlapped demonstrating the disproportionation of bacterial distribution in biofilm and plankton. Pseudomonadales, Rhizobiales and Sphingobacteriales were exoelectrogenic orders in the present study. The research obtained deep insight of microbial community and provided more comprehensive information on uncultured rare bacteria.

  6. Predictive Potential of Flux Balance Analysis of Saccharomyces cerevisiae Using as Optimization Function Combinations of Cell Compartmental Objectives

    PubMed Central

    García Sánchez, Carlos Eduardo; Vargas García, César Augusto; Torres Sáez, Rodrigo Gonzalo

    2012-01-01

    Background The main objective of flux balance analysis (FBA) is to obtain quantitative predictions of metabolic fluxes of an organism, and it is necessary to use an appropriate objective function to guarantee a good estimation of those fluxes. Methodology In this study, the predictive performance of FBA was evaluated, using objective functions arising from the linear combination of different cellular objectives. This approach is most suitable for eukaryotic cells, owing to their multiplicity of cellular compartments. For this reason, Saccharomyces cerevisiae was used as model organism, and its metabolic network was represented using the genome-scale metabolic model iMM904. As the objective was to evaluate the predictive performance from the FBA using the kind of objective function previously described, substrate uptake and oxygen consumption were the only input data used for the FBA. Experimental information about microbial growth and exchange of metabolites with the environment was used to assess the quality of the predictions. Conclusions The quality of the predictions obtained with the FBA depends greatly on the knowledge of the oxygen uptake rate. For the most of studied classifications, the best predictions were obtained with “maximization of growth”, and with some combinations that include this objective. However, in the case of exponential growth with unknown oxygen exchange flux, the objective function “maximization of growth, plus minimization of NADH production in cytosol, plus minimization of NAD(P)H consumption in mitochondrion” gave much more accurate estimations of fluxes than the obtained with any other objective function explored in this study. PMID:22912775

  7. Reduction of volatile acidity of acidic wines by immobilized Saccharomyces cerevisiae cells.

    PubMed

    Vilela, A; Schuller, D; Mendes-Faia, A; Côrte-Real, M

    2013-06-01

    Excessive volatile acidity in wines is a major problem and is still prevalent because available solutions are nevertheless unsatisfactory, namely, blending the filter-sterilized acidic wine with other wines of lower volatile acidity or using reverse osmosis. We have previously explored the use of an empirical biological deacidification procedure to lower the acetic acid content of wines. This winemaker's enological practice, which consists in refermentation associated with acetic acid consumption by yeasts, is performed by mixing the acidic wine with freshly crushed grapes, musts, or marc from a finished wine fermentation. We have shown that the commercial strain Saccharomyces cerevisiae S26 is able to decrease the volatile acidity of acidic wines with a volatile acidity higher than 1.44 g L(-1) acetic acid, with no detrimental impact on wine aroma. In this study, we aimed to optimize the immobilization of S26 cells in alginate beads for the bioreduction of volatile acidity of acidic wines. We found that S26 cells immobilized in double-layer alginate-chitosan beads could reduce the volatile acidity of an acidic wine (1.1 g L(-1) acetic acid, 12.5 % (v/v) ethanol, pH 3.12) by 28 and 62 % within 72 and 168 h, respectively, associated with a slight decrease in ethanol concentration (0.7 %). Similar volatile acidity removal efficiencies were obtained in medium with high glucose concentration (20 % w/v), indicating that this process may also be useful in the deacidification of grape musts. We, therefore, show that immobilized S. cerevisiae S26 cells in double-layer beads are an efficient alternative to improve the quality of wines with excessive volatile acidity.

  8. Chemical and enzymatic extraction of heavy metal binding polymers from isolated cell walls of Saccharomyces cerevisiae

    SciTech Connect

    Brady, D.; Stoll, A.D.; Starke, L.; Duncan, J.R. . Dept. of Biochemistry and Microbiology)

    1994-07-01

    Isolated cell walls of the yeast Saccharomyces cerevisiae were treated by either chemical (alkali and acid) or enzymatic (protease, mannanase or [beta]-glucuronidase) processes to yield partially purified products. These products were partially characterized by infrared analysis. They were subsequently reacted with heavy metal cation solutions and the quantity of metal accumulated by the cell wall material determined. The Cu[sup 2+] ion (0.24, 0.36, 1.12, and 0.60 [mu]mol/mg) was accumulated to a greater extent than either Co[sup 2+] (0.13, 0.32, 0.43, and 0.32 [mu]mol/mg) or Cd[sup 2+] (0.17, 0.34, 0.39, and 0.46 [mu]mol/mg) by yeast cell walls, glucan, mannan, and chitin, respectively. The isolated components each accumulated greater quantities of the cations than the intact cell wall. Removal of the protein component of the yeast cell wall by Pronase caused a 29.5% decrease in metal accumulation by yeast cell walls per mass, indicating that protein is a heavy metal accumulating component. The data indicate that the outer mannan-protein layer of the yeast cell wall is more important than the inner glucan-chitin layer in heavy metal cation accumulation.

  9. Rapid detection of microbial cell abundance in aquatic systems

    DOE PAGES

    Rocha, Andrea M.; Yuan, Quan; Close, Dan M.; ...

    2016-06-01

    The detection and quantification of naturally occurring microbial cellular densities is an essential component of environmental systems monitoring. While there are a number of commonly utilized approaches for monitoring microbial abundance, capacitance-based biosensors represent a promising approach because of their low-cost and label-free detection of microbial cells, but are not as well characterized as more traditional methods. Here, we investigate the applicability of enhanced alternating current electrokinetics (ACEK) capacitive sensing as a new application for rapidly detecting and quantifying microbial cellular densities in cultured and environmentally sourced aquatic samples. ACEK capacitive sensor performance was evaluated using two distinct and dynamicmore » systems the Great Australian Bight and groundwater from the Oak Ridge Reservation in Oak Ridge, TN. Results demonstrate that ACEK capacitance-based sensing can accurately determine microbial cell counts throughout cellular concentrations typically encountered in naturally occurring microbial communities (103 – 106 cells/mL). A linear relationship was observed between cellular density and capacitance change correlations, allowing a simple linear curve fitting equation to be used for determining microbial abundances in unknown samples. As a result, this work provides a foundation for understanding the limits of capacitance-based sensing in natural environmental samples and supports future efforts focusing on evaluating the robustness ACEK capacitance-based within aquatic environments.« less

  10. Rapid detection of microbial cell abundance in aquatic systems.

    PubMed

    Rocha, Andrea M; Yuan, Quan; Close, Dan M; O'Dell, Kaela B; Fortney, Julian L; Wu, Jayne; Hazen, Terry C

    2016-11-15

    The detection and quantification of naturally occurring microbial cellular densities is an essential component of environmental systems monitoring. While there are a number of commonly utilized approaches for monitoring microbial abundance, capacitance-based biosensors represent a promising approach because of their low-cost and label-free detection of microbial cells, but are not as well characterized as more traditional methods. Here, we investigate the applicability of enhanced alternating current electrokinetics (ACEK) capacitive sensing as a new application for rapidly detecting and quantifying microbial cellular densities in cultured and environmentally sourced aquatic samples. ACEK capacitive sensor performance was evaluated using two distinct and dynamic systems - the Great Australian Bight and groundwater from the Oak Ridge Reservation in Oak Ridge, TN. Results demonstrate that ACEK capacitance-based sensing can accurately determine microbial cell counts throughout cellular concentrations typically encountered in naturally occurring microbial communities (10(3)-10(6) cells/mL). A linear relationship was observed between cellular density and capacitance change correlations, allowing a simple linear curve fitting equation to be used for determining microbial abundances in unknown samples. This work provides a foundation for understanding the limits of capacitance-based sensing in natural environmental samples and supports future efforts focusing on evaluating the robustness ACEK capacitance-based within aquatic environments. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  11. Mutants of Saccharomyces cerevisiae unresponsive to cell division control by polypeptide mating hormone

    PubMed Central

    1980-01-01

    Temperature-sensitive mutations that produce insensitivity to division arrest by alpha-factor, a mating pheromone, were isolated in an MATa strain of Saccharomyces cerevisiae and shown by complementation studies to difine eight genes. All of these mutations (designated ste) produce sterility at the restrictive temperature in MATa cells, and mutations in seven of the genes produce sterility in MAT alpha cells. In no case was the sterility associated with these mutations coorectible by including wild-type cells of the same mating type in the mating test nor did nay of the mutants inhibit mating of the wild-type cells; the defect appears to be intrinsic to the cell for mutations in each of the genes. Apparently, none of the mutants is defective exclusively in division arrest by alpha-factor, as the sterility of none is suppressed by a temperature-sensitive cdc 28 mutation (the latter imposes division arrest at the correct cell cycle stage for mating). The mutants were examined for features that are inducible in MATa cells by alpha-factor (agglutinin synthesis as well as division arrest) and for the characteristics that constitutively distinguish MATa from MAT alpha cells (a-factor production, alpha-factor destruction). ste2 Mutants are defective specifically in the two inducible properties, whereas ste4, 5, 7, 8, 9, 11, and 12 mutants are defective, to varying degrees, in constitutive as well as inducible aspects. Mutations in ste8 and 9 assume a polar budding pattern unlike either MATa or MAT alpha cells but characteristic of MATa/alpha cells. This study defines seven genes that function in two cell types (MATa and alpha) to control the differentiation of cell type and one gene, ste2, that functions exclusively in MATa cells to mediate responsiveness to polypeptide hormone. PMID:6993497

  12. An efficient magnetically modified microbial cell biocomposite for carbazole biodegradation

    PubMed Central

    2013-01-01

    Magnetic modification of microbial cells enables to prepare smart biocomposites in bioremediation. In this study, we constructed an efficient biocomposite by assembling Fe3O4 nanoparticles onto the surface of Sphingomonas sp. XLDN2-5 cells. The average particle size of Fe3O4 nanoparticles was about 20 nm with 45.5 emu g-1 saturation magnetization. The morphology of Sphingomonas sp. XLDN2-5 cells before and after Fe3O4 nanoparticle loading was verified by scanning electron microscopy and transmission electronic microscopy. Compared with free cells, the microbial cell/Fe3O4 biocomposite had the same biodegradation activity but exhibited remarkable reusability. The degradation activity of the microbial cell/Fe3O4 biocomposite increased gradually during recycling processes. Additionally, the microbial cell/Fe3O4 biocomposite could be easily separated and recycled by an external magnetic field due to the super-paramagnetic properties of Fe3O4 nanoparticle coating. These results indicated that magnetically modified microbial cells provide a promising technique for improving biocatalysts used in the biodegradation of hazardous compounds. PMID:24330511

  13. An efficient magnetically modified microbial cell biocomposite for carbazole biodegradation

    NASA Astrophysics Data System (ADS)

    Li, Yufei; Du, Xiaoyu; Wu, Chao; Liu, Xueying; Wang, Xia; Xu, Ping

    2013-12-01

    Magnetic modification of microbial cells enables to prepare smart biocomposites in bioremediation. In this study, we constructed an efficient biocomposite by assembling Fe3O4 nanoparticles onto the surface of Sphingomonas sp. XLDN2-5 cells. The average particle size of Fe3O4 nanoparticles was about 20 nm with 45.5 emu g-1 saturation magnetization. The morphology of Sphingomonas sp. XLDN2-5 cells before and after Fe3O4 nanoparticle loading was verified by scanning electron microscopy and transmission electronic microscopy. Compared with free cells, the microbial cell/Fe3O4 biocomposite had the same biodegradation activity but exhibited remarkable reusability. The degradation activity of the microbial cell/Fe3O4 biocomposite increased gradually during recycling processes. Additionally, the microbial cell/Fe3O4 biocomposite could be easily separated and recycled by an external magnetic field due to the super-paramagnetic properties of Fe3O4 nanoparticle coating. These results indicated that magnetically modified microbial cells provide a promising technique for improving biocatalysts used in the biodegradation of hazardous compounds.

  14. Vaccinium corymbosum L. (blueberry) extracts exhibit protective action against cadmium toxicity in Saccharomyces cerevisiae cells.

    PubMed

    Oprea, Eliza; Ruta, Lavinia L; Nicolau, Ioana; Popa, Claudia V; Neagoe, Aurora D; Farcasanu, Ileana C

    2014-01-01

    Blueberries (Vaccinium corymbosum L.) are a rich source of antioxidants and their consumption is believed to contribute to food-related protection against oxidative stress. In the present study, the chemoprotective action of blueberry extracts against cadmium toxicity was investigated using a cadmium-hypersensitive strain of Saccharomyces cerevisiae. Four varieties of blueberries were used in the study, and it was found that the extracts with high content of total anthocyanidins exhibited significant protective effect against the toxicity of cadmium and H2O2. Both the blueberry extracts and pure cyanidin exhibited protective effects against cadmium in a dose-dependent manner, but without significantly interfering with the cadmium accumulation by the yeast cells. The results imply that the blueberry extracts might be a potentially valuable food supplement for individuals exposed to high cadmium.

  15. Calcium signaling mediates the response to cadmium toxicity in Saccharomyces cerevisiae cells.

    PubMed

    Ruta, Lavinia L; Popa, Valentina C; Nicolau, Ioana; Danet, Andrei F; Iordache, Virgil; Neagoe, Aurora D; Farcasanu, Ileana C

    2014-08-25

    The involvement of Ca(2+) in the response to high Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), and Hg(2+) was investigated in Saccharomyces cerevisiae. The yeast cells responded through a sharp increase in cytosolic Ca(2+) when exposed to Cd(2+), and to a lesser extent to Cu(2+), but not to Mn(2+), Co(2+), Ni(2+), Zn(2+), or Hg(2+). The response to high Cd(2+) depended mainly on external Ca(2+) (transported through the Cch1p/Mid1p channel) but also on vacuolar Ca(2+) (released into the cytosol through the Yvc1p channel). The adaptation to high Cd(2+) was influenced by perturbations in Ca(2+) homeostasis. Thus, the tolerance to Cd(2+) often correlated with sharp Cd(2+)-induced cytosolic Ca(2+) pulses, while the Cd(2+) sensitivity was accompanied by the incapacity to rapidly restore the low cytosolic Ca(2+).

  16. Production of single cell protein (SCP) from food and agricultural waste by using Saccharomyces cerevisiae.

    PubMed

    Gervasi, Teresa; Pellizzeri, Vito; Calabrese, Giorgio; Di Bella, Giuseppa; Cicero, Nicola; Dugo, Giacomo

    2017-05-25

    Food waste is the single-largest component of the waste stream, in order to protect and safeguard the public health, useful and innovative recycling methods are investigated. The conversion of food wastes in value-added products is becoming a more economically viable and interesting practice. Food waste, collected in the distribution sector and citrus industries, was characterised for its potential as a raw material to use in fermentation processes. In this study, the production of single-cell protein (SCP) using food waste as a substrate was investigated. The purpose of this study has been to produce SCP from mixtures of food waste using Saccharomyces cerevisiae. The main fermentation test was carried out using a 25 l bioreactor. The utilisation of food waste can allow us to not only to reduce environmental pollution, but also to obtain value-added products such as protein supply for animal feed.

  17. Electricity generation in a microbial fuel cell with a microbially catalyzed cathode.

    PubMed

    Zhang, Jin-Na; Zhao, Qing-Liang; Aelterman, Peter; You, Shi-Jie; Jiang, Jun-Qiu

    2008-10-01

    A microbial fuel cell using aerobic microorganisms as the cathodic catalysts is described. By using anaerobic sludge in the anode and aerobic sludge in the cathode as inocula, the microbial fuel cell could be started up after a short lag time of 9 days, generating a stable voltage of 0.324 V (R (ex) = 500 Omega). At an aeration rate of 300 ml min(-1) in the cathode, a maximum volumetric power density of up to 24.7 W m(-3) (117.2 A m(-3)) was reached. This research demonstrates an economic system for recovering electrical energy from organic compounds.

  18. Importance of cell damage causing growth delay for high pressure inactivation of Saccharomyces cerevisiae

    NASA Astrophysics Data System (ADS)

    Nanba, Masaru; Nomura, Kazuki; Nasuhara, Yusuke; Hayashi, Manabu; Kido, Miyuki; Hayashi, Mayumi; Iguchi, Akinori; Shigematsu, Toru; Hirayama, Masao; Ueno, Shigeaki; Fujii, Tomoyuki

    2013-06-01

    A high pressure (HP) tolerant (barotolerant) mutant a2568D8 and a variably barotolerant mutant a1210H12 were generated from Saccharomyces cerevisiae using ultra-violet mutagenesis. The two mutants, a barosensitive mutant a924E1 and the wild-type strain, were pressurized (225 MPa), and pressure inactivation behavior was analyzed. In the wild-type strain, a proportion of the growth-delayed cells were detected after exposure to HP. In a924E1, the proportion of growth-delayed cells significantly decreased compared with the wild-type. In a2568D8, the proportion of growth-delayed cells increased and the proportion of inactivated cells decreased compared with the wild-type. In a1210H12, the growth-delayed cells could not be detected within 120 s of exposure to HP. The proportion of growth-delayed cells, which incurred the damage, would affect the survival ratio by HP. These results suggested that cellular changes in barotolerance caused by mutations are remarkably affected by the ability to recover from cellular damage, which results in a growth delay.

  19. Lack of cortical endoplasmic reticulum protein Ist2 alters sodium accumulation in Saccharomyces cerevisiae cells.

    PubMed

    Papouskova, Klara; Andrsova, Marketa; Sychrova, Hana

    2017-03-01

    The maintenance of intracellular alkali-metal-cation homeostasis is a fundamental property of all living organisms, including the yeast Saccharomyces cerevisiae. Several transport systems are indispensable to ensure proper alkali-metal-cation levels in the yeast cytoplasm and organelles. Ist2 is an endoplasmic reticulum (ER)-resident protein involved, together with other tethering proteins, in the formation of contacts between the plasma and ER membranes. As IST2 gene deletion was shown to influence yeast growth in the presence of sodium, we focused on the roles of Ist2 in the cell response to the presence of various concentrations of alkali metal cations, and its interactions with characterised plasma membrane alkali-metal-cation transporters. Most importantly, we show that, in BY4741 background, the lack of Ist2 results in the accumulation of higher amounts of sodium when the cells are exposed to the presence of this cation, demonstrating the importance of Ist2 for the maintenance of low intracellular levels of toxic sodium. As the function and localisation of alkali-metal-cation exporters is not affected in ist2Δ cells, IST2 deletion results in an increased non-specific uptake of sodium to cells. Moreover, the deletion of IST2 influences relative cell membrane potential, pHin and the growth of cells in the presence of a limiting K+ concentration. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  20. Identification of Proteins Whose Synthesis Is Modulated During the Cell Cycle of Saccharomyces cerevisiae

    PubMed Central

    Lörincz, Attila T.; Miller, Mark J.; Xuong, Nguyen-Huu; Geiduschek, E. Peter

    1982-01-01

    We examined the synthesis and turnover of individual proteins in the Saccharomyces cerevisiae cell cycle. Proteins were pulse-labeled with radioactive isotope (35S or 14C) in cells at discrete cycle stages and then resolved on two-dimensional gels and analyzed by a semiautomatic procedure for quantitating gel electropherogram-autoradiographs. The cells were obtained by one of three methods: (i) isolation of synchronous subpopulations of growing cells by zonal centrifugation; (ii) fractionation of pulse-labeled steady-state cultures according to cell age; and (iii) synchronization of cells with the mating pheromone, α-factor. In confirmation of previous studies, we found that the histones H4, H2A, and H2B were synthesized almost exclusively in the late G1 and early S phases. In addition, we identified eight proteins whose rates of synthesis were modulated in the cell cycle, and nine proteins (of which five, which may well be related, were unstable, with half-lives of 10 to 15 min) that might be regulated in the cell cycle by periodic synthesis, modification, or degradation. Based on the time of maximal labeling in the cell cycle and on experiments with α-factor and hydroxyurea, we assigned the cell cycle proteins to two classes: proteins in class I were labeled principally in early G1 phase and at a late stage of the cycle, whereas those in class II were primarily synthesized at times ranging from late G1 to mid S phase. At least one major control point for the cell cycle proteins occurred between “start” and early S phase. A set of stress-responsive proteins was also identified and analyzed. The rates of synthesis of these proteins were affected by certain perturbations that resulted during selection of synchronous cell populations and by heat shock. Images PMID:14582195

  1. Enrichment of microbial electrolysis cell biocathodes from sediment microbial fuel cell bioanodes.

    PubMed

    Pisciotta, John M; Zaybak, Zehra; Call, Douglas F; Nam, Joo-Youn; Logan, Bruce E

    2012-08-01

    Electron-accepting (electrotrophic) biocathodes were produced by first enriching graphite fiber brush electrodes as the anodes in sediment-type microbial fuel cells (sMFCs) using two different marine sediments and then electrically inverting the anodes to function as cathodes in two-chamber bioelectrochemical systems (BESs). Electron consumption occurred at set potentials of -439 mV and -539 mV (versus the potential of a standard hydrogen electrode) but not at -339 mV in minimal media lacking organic sources of energy. Results at these different potentials were consistent with separate linear sweep voltammetry (LSV) scans that indicated enhanced activity (current consumption) below only ca. -400 mV. MFC bioanodes not originally acclimated at a set potential produced electron-accepting (electrotrophic) biocathodes, but bioanodes operated at a set potential (+11 mV) did not. CO(2) was removed from cathode headspace, indicating that the electrotrophic biocathodes were autotrophic. Hydrogen gas generation, followed by loss of hydrogen gas and methane production in one sample, suggested hydrogenotrophic methanogenesis. There was abundant microbial growth in the biocathode chamber, as evidenced by an increase in turbidity and the presence of microorganisms on the cathode surface. Clone library analysis of 16S rRNA genes indicated prominent sequences most similar to those of Eubacterium limosum (Butyribacterium methylotrophicum), Desulfovibrio sp. A2, Rhodococcus opacus, and Gemmata obscuriglobus. Transfer of the suspension to sterile cathodes made of graphite plates, carbon rods, or carbon brushes in new BESs resulted in enhanced current after 4 days, demonstrating growth by these microbial communities on a variety of cathode substrates. This report provides a simple and effective method for enriching autotrophic electrotrophs by the use of sMFCs without the need for set potentials, followed by the use of potentials more negative than -400 mV.

  2. Enrichment of Microbial Electrolysis Cell Biocathodes from Sediment Microbial Fuel Cell Bioanodes

    SciTech Connect

    Pisciotta, JM; Zaybak, Z; Call, DF; Nam, JY; Logan, BE

    2012-07-18

    Electron-accepting (electrotrophic) biocathodes were produced by first enriching graphite fiber brush electrodes as the anodes in sediment-type microbial fuel cells (sMFCs) using two different marine sediments and then electrically inverting the anodes to function as cathodes in two-chamber bioelectrochemical systems (BESs). Electron consumption occurred at set potentials of -439 mV and -539 mV (versus the potential of a standard hydrogen electrode) but not at -339 mV in minimal media lacking organic sources of energy. Results at these different potentials were consistent with separate linear sweep voltammetry (LSV) scans that indicated enhanced activity (current consumption) below only ca. -400 mV. MFC bioanodes not originally acclimated at a set potential produced electron-accepting (electrotrophic) biocathodes, but bioanodes operated at a set potential (+11 mV) did not. CO, was removed from cathode headspace, indicating that the electrotrophic biocathodes were autotrophic. Hydrogen gas generation, followed by loss of hydrogen gas and methane production in one sample, suggested hydrogenotrophic methanogenesis. There was abundant microbial growth in the biocathode chamber, as evidenced by an increase in turbidity and the presence of microorganisms on the cathode surface. Clone library analysis of 16S rRNA genes indicated prominent sequences most similar to those of Eubacterium limosum (Butyribacterium methylotrophicum), Desulfovibrio sp. A2, Rhodococcus opacus, and Gemmata obscuriglobus. Transfer of the suspension to sterile cathodes made of graphite plates, carbon rods, or carbon brushes in new BESs resulted in enhanced current after 4 days, demonstrating growth by these microbial communities on a variety of cathode substrates. This report provides a simple and effective method for enriching autotrophic electrotrophs by the use of sMFCs without the need for set potentials, followed by the use of potentials more negative than -400 mV.

  3. Enrichment of Microbial Electrolysis Cell Biocathodes from Sediment Microbial Fuel Cell Bioanodes

    PubMed Central

    Pisciotta, John M.; Zaybak, Zehra; Call, Douglas F.; Nam, Joo-Youn

    2012-01-01

    Electron-accepting (electrotrophic) biocathodes were produced by first enriching graphite fiber brush electrodes as the anodes in sediment-type microbial fuel cells (sMFCs) using two different marine sediments and then electrically inverting the anodes to function as cathodes in two-chamber bioelectrochemical systems (BESs). Electron consumption occurred at set potentials of −439 mV and −539 mV (versus the potential of a standard hydrogen electrode) but not at −339 mV in minimal media lacking organic sources of energy. Results at these different potentials were consistent with separate linear sweep voltammetry (LSV) scans that indicated enhanced activity (current consumption) below only ca. −400 mV. MFC bioanodes not originally acclimated at a set potential produced electron-accepting (electrotrophic) biocathodes, but bioanodes operated at a set potential (+11 mV) did not. CO2 was removed from cathode headspace, indicating that the electrotrophic biocathodes were autotrophic. Hydrogen gas generation, followed by loss of hydrogen gas and methane production in one sample, suggested hydrogenotrophic methanogenesis. There was abundant microbial growth in the biocathode chamber, as evidenced by an increase in turbidity and the presence of microorganisms on the cathode surface. Clone library analysis of 16S rRNA genes indicated prominent sequences most similar to those of Eubacterium limosum (Butyribacterium methylotrophicum), Desulfovibrio sp. A2, Rhodococcus opacus, and Gemmata obscuriglobus. Transfer of the suspension to sterile cathodes made of graphite plates, carbon rods, or carbon brushes in new BESs resulted in enhanced current after 4 days, demonstrating growth by these microbial communities on a variety of cathode substrates. This report provides a simple and effective method for enriching autotrophic electrotrophs by the use of sMFCs without the need for set potentials, followed by the use of potentials more negative than −400 mV. PMID:22610438

  4. B cell-helping functions of gut microbial metabolites

    PubMed Central

    Kim, Chang H.

    2016-01-01

    Commensal microflora profoundly affects the host immune system. It has long been observed that commensal bacteria enhance antibody production in the host by producing antigens for B cell receptors (BCR) and ligands for Toll-like receptors (TLR). We recently reported that the microbial metabolites short-chain fatty acids (SCFAs) regulate the metabolism and gene expression in B cells to promote antibody production (Kim et al. Gut Microbial Metabolites Fuel Host Antibody Responses. Cell Host & Microbe. 2016; 20(2):202-14). The B-cell helping function of SCFAs and its implication in the host immune system are discussed in this article. PMID:28357321

  5. B cell-helping functions of gut microbial metabolites.

    PubMed

    Kim, Chang H

    2016-09-23

    Commensal microflora profoundly affects the host immune system. It has long been observed that commensal bacteria enhance antibody production in the host by producing antigens for B cell receptors (BCR) and ligands for Toll-like receptors (TLR). We recently reported that the microbial metabolites short-chain fatty acids (SCFAs) regulate the metabolism and gene expression in B cells to promote antibody production (Kim et al. Gut Microbial Metabolites Fuel Host Antibody Responses. Cell Host & Microbe. 2016; 20(2):202-14). The B-cell helping function of SCFAs and its implication in the host immune system are discussed in this article.

  6. Microbial communities involved in electricity generation from sulfide oxidation in a microbial fuel cell.

    PubMed

    Sun, Min; Tong, Zhong-Hua; Sheng, Guo-Ping; Chen, Yong-Zhen; Zhang, Feng; Mu, Zhe-Xuan; Wang, Hua-Lin; Zeng, Raymond J; Liu, Xian-Wei; Yu, Han-Qing; Wei, Li; Ma, Fang

    2010-10-15

    Simultaneous electricity generation and sulfide removal can be achieved in a microbial fuel cell (MFC). In electricity harvesting from sulfide oxidation in such an MFC, various microbial communities are involved. It is essential to elucidate the microbial communities and their roles in the sulfide conversion and electricity generation. In this work, an MFC was constructed to enrich a microbial consortium, which could harvest electricity from sulfide oxidation. Electrochemical analysis demonstrated that microbial catalysis was involved in electricity output in the sulfide-fed MFC. The anode-attached and planktonic communities could perform catalysis independently, and synergistic interactions occurred when the two communities worked together. A 16S rRNA clone library analysis was employed to characterize the microbial communities in the MFC. The anode-attached and planktonic communities shared similar richness and diversity, while the LIBSHUFF analysis revealed that the two community structures were significantly different. The exoelectrogenic, sulfur-oxidizing and sulfate-reducing bacteria were found in the MFC anodic chamber. The discovery of these bacteria was consistent with the community characteristics for electricity generation from sulfide oxidation. The exoelectrogenic bacteria were found both on the anode and in the solution. The sulfur-oxidizing bacteria were present in greater abundance on the anode than in the solution, while the sulfate-reducing bacteria preferably lived in the solution.

  7. Modeling of Sustainable Base Production by Microbial Electrolysis Cell.

    PubMed

    Blatter, Maxime; Sugnaux, Marc; Comninellis, Christos; Nealson, Kenneth; Fischer, Fabian

    2016-07-07

    A predictive model for the microbial/electrochemical base formation from wastewater was established and compared to experimental conditions within a microbial electrolysis cell. A Na2 SO4 /K2 SO4 anolyte showed that model prediction matched experimental results. Using Shewanella oneidensis MR-1, a strong base (pH≈13) was generated using applied voltages between 0.3 and 1.1 V. Due to the use of bicarbonate, the pH value in the anolyte remained unchanged, which is required to maintain microbial activity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Electricity production from municipal solid waste using microbial fuel cells.

    PubMed

    Chiu, H Y; Pai, T Y; Liu, M H; Chang, C A; Lo, F C; Chang, T C; Lo, H M; Chiang, C F; Chao, K P; Lo, W Y; Lo, S W; Chu, Y L

    2016-07-01

    The organic content of municipal solid waste has long been an attractive source of renewable energy, mainly as a solid fuel in waste-to-energy plants. This study focuses on the potential to use microbial fuel cells to convert municipal solid waste organics into energy using various operational conditions. The results showed that two-chamber microbial fuel cells with carbon felt and carbon felt allocation had a higher maximal power density (20.12 and 30.47 mW m(-2) for 1.5 and 4 L, respectively) than those of other electrode plate allocations. Most two-chamber microbial fuel cells (1.5 and 4 L) had a higher maximal power density than single-chamber ones with corresponding electrode plate allocations. Municipal solid waste with alkali hydrolysis pre-treatment and K3Fe(CN)6 as an electron acceptor improved the maximal power density to 1817.88 mW m(-2) (~0.49% coulomb efficiency, from 0.05-0.49%). The maximal power density from experiments using individual 1.5 and 4 L two-chamber microbial fuel cells, and serial and parallel connections of 1.5 and 4 L two-chamber microbial fuel cells, was found to be in the order of individual 4 L (30.47 mW m(-2)) > serial connection of 1.5 and 4 L (27.75) > individual 1.5 L (20.12) > parallel connection of 1.5 and 4 L (17.04) two-chamber microbial fuel cells . The power density using municipal solid waste microbial fuel cells was compared with information in the literature and discussed. © The Author(s) 2016.

  9. Efficiency Analysis and Mechanism Insight of that Whole-Cell Biocatalytic Production of Melibiose from Raffinose with Saccharomyces cerevisiae.

    PubMed

    Zhou, Yingbiao; Zhu, Yueming; Dai, Longhai; Men, Yan; Wu, Jinhai; Zhang, Juankun; Sun, Yuanxia

    2017-01-01

    Melibiose is widely used as a functional carbohydrate. Whole-cell biocatalytic production of melibiose from raffinose could reduce its cost. However, characteristics of strains for whole-cell biocatalysis and mechanism of such process are unclear. We compared three different Saccharomyces cerevisiae strains (liquor, wine, and baker's yeasts) in terms of concentration variations of substrate (raffinose), target product (melibiose), and by-products (fructose and galactose) in whole-cell biocatalysis process. Distinct difference was observed in whole-cell catalytic efficiency among three strains. Furthermore, activities of key enzymes (invertase, α-galactosidase, and fructose transporter) involved in process and expression levels of their coding genes (suc2, mel1, and fsy1) were investigated. Conservation of key genes in S. cerevisiae strains was also evaluated. Results show that whole-cell catalytic efficiency of S. cerevisiae in the raffinose substrate was closely related to activity of key enzymes and expression of their coding genes. Finally, we summarized characteristics of producing strain that offered advantages, as well as contributions of key genes to excellent strains. Furthermore, we presented a dynamic mechanism model to achieve some mechanism insight for this whole-cell biocatalytic process. This pioneering study should contribute to improvement of whole-cell biocatalytic production of melibiose from raffinose.

  10. Activation of chitin synthetase in permeabilized cells of a Saccharomyces cerevisiae mutant lacking proteinase B.

    PubMed Central

    Fernandez, M P; Correa, J U; Cabib, E

    1982-01-01

    Digitonin treatment at 30 degrees C of a Saccharomyces cerevisiae mutant lacking proteinase B permeabilized the cells and caused rapid and extensive activation of chitin synthetase in situ. The same result was obtained with a mutant generally defective in vacuolar proteases. By lowering the temperature and using different permeabilization procedures, we showed that increases in permeability and activation are distinct processes. Activation was inhibited by the protease inhibitors antipain and leupeptin, but by pepstatin or chymostatin. Metal chelators were also inhibitory, and their effect was reversed by the addition of Ca2+ but not by Mg2+. Antipain added together with Ca2+ after incubation of the cells in the presence of a chelating agent prevented reversal of inhibition, a result that was interpreted as indicating that antipain acts either on the same step affected by Ca2+ or on a subsequent step. Efforts to obtain activation in cell-free extracts were unsuccessful, but it was possible to extract the synthetase, once activated, by breaking permeabilized cells with glass beads. Treatment of the cell-free extracts with trypsin led not only to increased activity of chitin synthetase, but also to a change in the pH-activity curve and a diminished requirement by the enzyme for free N-acetylglucosamine. These observations suggest that the modification undergone by the synthetase during endogenous activation is different from that brought about by trypsin treatment. Images PMID:6216245

  11. Assessment of yeast Saccharomyces cerevisiae component binding to Mycobacterium avium subspecies paratuberculosis using bovine epithelial cells.

    PubMed

    Li, Ziwei; You, Qiumei; Ossa, Faisury; Mead, Philip; Quinton, Margaret; Karrow, Niel A

    2016-03-01

    Since yeast Saccharomyces cerevisiae and its components are being used for the prevention and treatment of enteric diseases in different species, they may also be useful for preventing Johne's disease, a chronic inflammatory bowel disease of ruminants caused by Mycobacterium avium spp. paratuberculosis (MAP). This study aimed to identify potential yeast derivatives that may be used to help prevent MAP infection. The adherence of mCherry-labeled MAP to bovine mammary epithelial cell line (MAC-T cells) and bovine primary epithelial cells (BECs) co-cultured with yeast cell wall components (CWCs) from four different yeast strains (A, B, C and D) and two forms of dead yeast from strain A was investigated. The CWCs from all four yeast strains and the other two forms of dead yeast from strain A reduced MAP adhesion to MAC-T cells and BECs in a concentration-dependent manner after 6-h of exposure, with the dead yeast having the greatest effect. The following in vitro binding studies suggest that dead yeast and its' CWCs may be useful for reducing risk of MAP infection.

  12. Potentiation of gene targeting in human cells by expression of Saccharomyces cerevisiae Rad52

    PubMed Central

    Di Primio, Cristina; Galli, Alvaro; Cervelli, Tiziana; Zoppè, Monica; Rainaldi, Giuseppe

    2005-01-01

    When exogenous DNA is stably introduced in mammalian cells, it is typically integrated in random positions, and only a minor fraction enters a pathway of homologous recombination (HR). The complex Rad51/Rad52 is a major player in the management of exogenous DNA in eukaryotic organisms and plays a critical role in the choice of repair system. In Saccharomyces cerevisiae, the pathway of choice is HR, mediated by Rad52 (ScRad52), which differs slightly from its human homologue. Here, we present an approach that utilizes ScRad52 to enhance HR in human cells containing a specific substrate for recombination. Clones of HeLa cells were produced expressing functional ScRad52. These cells showed enhanced resistance to DNA damaging treatments and revealed a different distribution of Rad51 foci (a marker of recombination complex formation). More significantly, ScRad52 expression resulted in an up to 37-fold increase in gene targeting by HR. In the same cells, random integration of exogenous DNA was significantly reduced, consistent with the view that HR and non-homologous end joining are alternative competing pathways. Expression of ScRad52 could offer a major improvement for experiments requiring gene targeting by HR, both in basic research and in gene therapy studies. PMID:16106043

  13. Valproate inhibits MAP kinase signalling and cell cycle progression in S. cerevisiae

    PubMed Central

    Desfossés-Baron, Kristelle; Hammond-Martel, Ian; Simoneau, Antoine; Sellam, Adnane; Roberts, Stephen; Wurtele, Hugo

    2016-01-01

    The mechanism of action of valproate (VPA), a widely prescribed short chain fatty acid with anticonvulsant and anticancer properties, remains poorly understood. Here, the yeast Saccharomyces cerevisiae was used as model to investigate the biological consequences of VPA exposure. We found that low pH strongly potentiates VPA-induced growth inhibition. Transcriptional profiling revealed that under these conditions, VPA modulates the expression of genes involved in diverse cellular processes including protein folding, cell wall organisation, sexual reproduction, and cell cycle progression. We further investigated the impact of VPA on selected processes and found that this drug: i) activates markers of the unfolded protein stress response such as Hac1 mRNA splicing; ii) modulates the cell wall integrity pathway by inhibiting the activation of the Slt2 MAP kinase, and synergizes with cell wall stressors such as micafungin and calcofluor white in preventing yeast growth; iii) prevents activation of the Kss1 and Fus3 MAP kinases of the mating pheromone pathway, which in turn abolishes cellular responses to alpha factor; and iv) blocks cell cycle progression and DNA replication. Overall, our data identify heretofore unknown biological responses to VPA in budding yeast, and highlight the broad spectrum of cellular pathways influenced by this chemical in eukaryotes. PMID:27782169

  14. TOR2 is part of two related signaling pathways coordinating cell growth in Saccharomyces cerevisiae.

    PubMed Central

    Helliwell, S B; Howald, I; Barbet, N; Hall, M N

    1998-01-01

    The Saccharomyces cerevisiae genes TOR1 and TOR2 encode phosphatidylinositol kinase homologs. TOR2 has two essential functions. One function overlaps with TOR1 and mediates protein synthesis and cell cycle progression. The second essential function of TOR2 is unique to TOR2 and mediates the cell-cycle-dependent organization of the actin cytoskeleton. We have isolated temperature-sensitive mutants that are defective for either one or both of the two TOR2 functions. The three classes of mutants were as follows. Class A mutants, lacking only the TOR2-unique function, are defective in actin cytoskeleton organization and arrest within two to three generations as small-budded cells in the G2/M phase of the cell cycle. Class B mutants, lacking only the TOR-shared function, and class C mutants, lacking both functions, exhibit a rapid loss of protein synthesis and a G1 arrest within one generation. To define further the two functions of TOR2, we isolated multicopy suppressors that rescue the class A or B mutants. Overexpression of MSS4, PKC1, PLC1, RHO2, ROM2, or SUR1 suppressed the growth defect of a class A mutant. Surprisingly, overexpression of PLC1 and MSS4 also suppressed the growth defect of a class B mutant. These genes encode proteins that are involved in phosphoinositide metabolism and signaling. Thus, the two functions (readouts) of TOR2 appear to involve two related signaling pathways controlling cell growth. PMID:9475724

  15. Solar energy powered microbial fuel cell with a reversible bioelectrode.

    PubMed

    Strik, David P B T B; Hamelers, Hubertus V M; Buisman, Cees J N

    2010-01-01

    The solar energy powered microbial fuel cell is an emerging technology for electricity generation via electrochemically active microorganisms fueled by solar energy via in situ photosynthesized metabolites from algae, cyanobacteria, or living higher plants. A general problem with microbial fuel cells is the pH membrane gradient which reduces cell voltage and power output. This problem is caused by acid production at the anode, alkaline production at the cathode, and the nonspecific proton exchange through the membrane. Here we report a solution for a new kind of solar energy powered microbial fuel cell via development of a reversible bioelectrode responsible for both biocatalyzed anodic and cathodic electron transfer. Anodic produced protons were used for the cathodic reduction reaction which held the formation of a pH membrane gradient. The microbial fuel cell continuously generated electricity and repeatedly reversed polarity dependent on aeration or solar energy exposure. Identified organisms within biocatalyzing biofilm of the reversible bioelectrode were algae, (cyano)bacteria and protozoa. These results encourage application of solar energy powered microbial fuel cells.

  16. Challenges in microbial fuel cell development and operation.

    PubMed

    Kim, Byung Hong; Chang, In Seop; Gadd, Geoffrey M

    2007-09-01

    A microbial fuel cell (MFC) is a device that converts chemical energy into electricity through the catalytic activities of microorganisms. Although there is great potential of MFCs as an alternative energy source, novel wastewater treatment process, and biosensor for oxygen and pollutants, extensive optimization is required to exploit the maximum microbial potential. In this article, the main limiting factors of MFC operation are identified and suggestions are made to improve performance.

  17. Expression of a Fungal Hydrophobin in the Saccharomyces cerevisiae Cell Wall: Effect on Cell Surface Properties and Immobilization

    PubMed Central

    Nakari-Setälä, Tiina; Azeredo, Joana; Henriques, Mariana; Oliveira, Rosário; Teixeira, José; Linder, Markus; Penttilä, Merja

    2002-01-01

    The aim of this work was to modify the cell surface properties of Saccharomyces cerevisiae by expression of the HFBI hydrophobin of the filamentous fungus Trichoderma reesei on the yeast cell surface. The second aim was to study the immobilization capacity of the modified cells. Fusion to the Flo1p flocculin was used to target the HFBI moiety to the cell wall. Determination of cell surface characteristics with contact angle and zeta potential measurements indicated that HFBI-producing cells are more apolar and slightly less negatively charged than the parent cells. Adsorption of the yeast cells to different commercial supports was studied. A twofold increase in the binding affinity of the hydrophobin-producing yeast to hydrophobic silicone-based materials was observed, while no improvement in the interaction with hydrophilic carriers could be seen compared to that of the parent cells. Hydrophobic interactions between the yeast cells and the support are suggested to play a major role in attachment. Also, a slight increase in the initial adsorption rate of the hydrophobin yeast was observed. Furthermore, due to the engineered cell surface, hydrophobin-producing yeast cells were efficiently separated in an aqueous two-phase system by using a nonionic polyoxyethylene detergent, C12-18EO5. PMID:12089019

  18. Diamagnetic levitation changes growth, cell cycle, and gene expression of Saccharomyces cerevisiae.

    PubMed

    Coleman, Chasity B; Gonzalez-Villalobos, Romer A; Allen, Patricia L; Johanson, Kelly; Guevorkian, Karine; Valles, James M; Hammond, Timothy G

    2007-11-01

    Inhomogeneous magnetic fields are used in magnetic traps to levitate biological specimens by exploiting the natural diamagnetism of virtually all materials. Using Saccharomyces cerevisiae, this report investigates whether magnetic field (B) induces changes in growth, cell cycle, and gene expression. Comparison to the effects of gravity and temperature allowed determination of whether the responses are general pathways or stimulus specific. Growth and cell cycle analysis were examined in wild-type (WT) yeast and strains with deletions in transcription factors Msn4 or Sfp1. Msn4, Sfp1, and Rap1 have been implicated in responses to physical forces, but only Msn4 and Sfp1 deletions are viable. Gene expression changes were examined in strains bearing GFP-tagged reporters for YIL052C (Sfp1-dependent), YST-2 (Sfp1/Rap1-dependent), or SSA4 (Msn4-dependent). The cell growth and gene expression responses were highly stimulus specific. B increased growth only following Msn4 or Sfp1 deletion, associated with decreased G1 and G2/M and increased S phase of the cell cycle. In addition, B suppressed expression of both YIL052C and YST2. Gravity decreased growth in an Sfp1 but not Msn4-dependent manner, in association with decreased G2/M and increased S phase of the cell cycle. Additionally, gravity decreased expression of SSA4 and YIL052C genes. Temperature increased cell growth in an Msn4- and Sfp1-dependent manner in association with increased G1 and G2/M with decreased S phase of the cell cycle. In addition, temperature increased YIL052C gene expression. This study shows that B has selective effects on cell growth, cell cycle, and gene expression that are stimulus specific.

  19. Quantification of cell volume changes upon hyperosmotic stress in Saccharomyces cerevisiae.

    PubMed

    Petelenz-Kurdziel, Elzbieta; Eriksson, Emma; Smedh, Maria; Beck, Caroline; Hohmann, Stefan; Goksör, Mattias

    2011-11-01

    Cell volume is a biophysical property, which is of great importance for quantitative characterisations of biological processes, such as osmotic adaptation. It also is a crucial parameter in the most common type of mathematical description of cellular behaviour-ordinary differential equation (ODE) models, e.g. the integrative model of the osmotic stress response in baker's yeast (E. Klipp, B. Nordlander, R. Kruger, P. Gennemark and S. Hohmann, Nat. Biotechnol., 2005, 23, 975-982). Until recently only rough estimates of this value were available. In this study we measured the mean volume of more than 300 individual yeast cells (Saccharomyces cerevisiae). We quantitatively characterised the dependence between the relative cell volume and the concentration of osmoticum in the cell surrounding. We also followed the recovery of the cellular volume over time, as well as the influence of increased external osmolarity on the nuclear volume. We found that cell shrinkage caused by shifts in the external osmolarity is proportional to the stress intensity only up to 1000 mM NaCl. At this concentration the yeast cells shrink to approximately 55% of their unstressed volume and this volume is maintained even in the case of further osmolarity increase. We observed that returning to the initial, unstressed volume takes more than 45 minutes for stress concentrations exceeding 100 mM NaCl and that only cells treated with the latter concentration are able to fully regain their initial size within the course of the experiment. We postulate that the cytoplasm plays a protective role for the nucleus by buffering the changes in volume caused by external osmolarity shifts. In conclusion, we quantitatively characterised the dynamics of cell volume changes caused by hyperosmotic stress, providing an accurate description of a biophysical cell property, which is crucial for precise mathematical simulations of cellular processes.

  20. Recombinant Saccharomyces cerevisiae (yeast-CEA) as a potent activator of murine dendritic cells.

    PubMed

    Bernstein, Michael B; Chakraborty, Mala; Wansley, Elizabeth K; Guo, Zhimin; Franzusoff, Alex; Mostböck, Sven; Sabzevari, Helen; Schlom, Jeffrey; Hodge, James W

    2008-01-24

    Recombinant Saccharomyces cerevisiae (yeast) represents a unique and attractive vehicle to deliver antigens in vaccine immunotherapy protocols for cancer or infectious disease, in that it has been shown to be extremely safe and can be administered multiple times to hosts. In the studies reported here, we describe the effects of treatment with recombinant yeast on murine immature dendritic cells (DCs). Yeast expressing human carcinoembryonic antigen (CEA) as a model antigen was studied. Injection of mice subcutaneously with yeast-CEA resulted in rapid increases in MHC class II(+) cells and total antigen-presenting cells in draining lymph nodes. Post-treatment with yeast-CEA, DCs rapidly elevated both MHC class I and class II, numerous costimulatory molecules and other DC maturation markers, and secreted a range of Type I inflammatory cytokines. Gene expression arrays also revealed the rapid up-regulation of numerous cytokine and chemokine mRNAs, as well as genes involved in signal transduction and antigen uptake. Functional studies demonstrated enhanced allospecific reactivity of DCs following treatment with yeast-CEA or control yeast. Additionally, treatment of DCs with yeast-CEA resulted in specific activation of CEA-specific CD8(+) T cells in an MHC-restricted manner in vitro. Lastly, vaccination of CEA-transgenic mice with yeast-CEA elicited antigen-specific CD4(+) and CD8(+) immune responses in vivo. Thus, these studies taken together form a scientific rationale for the use of recombinant yeast in vaccination protocols for cancer or infectious diseases.

  1. The chromatin structure of Saccharomyces cerevisiae autonomously replicating sequences changes during the cell division cycle.

    PubMed Central

    Brown, J A; Holmes, S G; Smith, M M

    1991-01-01

    The chromatin structures of two well-characterized autonomously replicating sequence (ARS) elements were examined at their chromosomal sites during the cell division cycle in Saccharomyces cerevisiae. The H4 ARS is located near one of the duplicate nonallelic histone H4 genes, while ARS1 is present near the TRP1 gene. Cells blocked in G1 either by alpha-factor arrest or by nitrogen starvation had two DNase I-hypersensitive sites of about equal intensity in the ARS element. This pattern of DNase I-hypersensitive sites was altered in synchronous cultures allowed to proceed into S phase. In addition to a general increase in DNase I sensitivity around the core consensus sequence, the DNase I-hypersensitive site closest to the core consensus became more nuclease sensitive than the distal site. This change in chromatin structure was restricted to the ARS region and depended on replication since cdc7 cells blocked near the time of replication initiation did not undergo the transition. Subsequent release of arrested cdc7 cells restored entry into S phase and was accompanied by the characteristic change in ARS chromatin structure. Images PMID:1922046

  2. Behavior of spindles and spindle plaques in the cell cycle and conjugation of Saccharomyces cerevisiae.

    PubMed Central

    Byers, B; Goetsch, L

    1975-01-01

    The interdependence of spindle plaque with other aspects of cell division and conjugation in Saccharomyces cerevisiae has been investigated. Three forms of the spindle plaque appear sequentially before the formation of the complete, intranuclear spindle. The single plaque is present initially in the mitotic cycle; it becomes transformed into a satellite-bearing single plaque during the latter part of G1. Subsequently, plaque duplication yields the double plaque characteristic of the early phase of budding, which coincides with the period of chromosome replication (S). The eventual separation of these plaques to form a complete spindle, with a single plaque at each pole, is nearly coincident with the completion of S. The form of the plaque differs in two independent cases of G1 arrest: the single plaque is found in a cell in stationary arrest of growth, whereas a cell arrested by mating factors in preparation for conjugation contains a satellite-bearing single plaque. The latter form is retained during zygote formation, where it serves as the initial site of fusion of each prezygotic nuceus with the other. This fusion results in the formation of a single zygotic nucleus with a satellite-bearing single plaque, which is subsequently transformed into a double plaque as the zygote buds. The double plaque is situated adjacent to the site of bud emergence in both vegetative cells and zygotes. Images PMID:1100612

  3. An atypical active cell death process underlies the fungicidal activity of ciclopirox olamine against the yeast Saccharomyces cerevisiae.

    PubMed

    Almeida, Bruno; Sampaio-Marques, Belém; Carvalho, Joana; Silva, Manuel T; Leão, Cecília; Rodrigues, Fernando; Ludovico, Paula

    2007-05-01

    Ciclopirox olamine (CPO), a fungicidal agent widely used in clinical practice, induced in Saccharomyces cerevisiae an active cell death (ACD) process characterized by changes in nuclear morphology and chromatin condensation associated with the appearance of a population in the sub-G(0)/G(1) cell cycle phase and an arrest delay in the G(2)/M phases. This ACD was associated neither with intracellular reactive oxygen species (ROS) signaling, as revealed by the use of different classes of ROS scavengers, nor with a terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive phenotype. Furthermore, CPO-induced cell death seems to be dependent on unknown protease activity but independent of the apoptotic regulators Aif1p and Yca1p and of autophagic pathways involving Apg5p, Apg8p and Uth1p. Our results show that CPO triggers in S. cerevisiae an atypical nonapoptotic, nonautophagic ACD with as yet unknown regulators.

  4. Aspergillus oryzae–Saccharomyces cerevisiae Consortium Allows Bio-Hybrid Fuel Cell to Run on Complex Carbohydrates

    PubMed Central

    Jahnke, Justin P.; Hoyt, Thomas; LeFors, Hannah M.; Sumner, James J.; Mackie, David M.

    2016-01-01

    Consortia of Aspergillus oryzae and Saccharomyces cerevisiae are examined for their abilities to turn complex carbohydrates into ethanol. To understand the interactions between microorganisms in consortia, Fourier-transform infrared spectroscopy is used to follow the concentrations of various metabolites such as sugars (e.g., glucose, maltose), longer chain carbohydrates, and ethanol to optimize consortia conditions for the production of ethanol. It is shown that with proper design A. oryzae can digest food waste simulants into soluble sugars that S. cerevisiae can ferment into ethanol. Depending on the substrate and conditions used, concentrations of 13% ethanol were achieved in 10 days. It is further shown that a direct alcohol fuel cell (FC) can be coupled with these A. oryzae-enabled S. cerevisiae fermentations using a reverse osmosis membrane. This “bio-hybrid FC” continually extracted ethanol from an ongoing consortium, enhancing ethanol production and allowing the bio-hybrid FC to run for at least one week. Obtained bio-hybrid FC currents were comparable to those from pure ethanol—water mixtures, using the same FC. The A. oryzae–S. cerevisiae consortium, coupled to a bio-hybrid FC, converted food waste simulants into electricity without any pre- or post-processing. PMID:27681904

  5. The function of chitin synthases 2 and 3 in the Saccharomyces cerevisiae cell cycle

    PubMed Central

    1991-01-01

    The morphology of three Saccharomyces cerevisiae strains, all lacking chitin synthase 1 (Chs1) and two of them deficient in either Chs3 (calR1 mutation) or Chs2 was observed by light and electron microscopy. Cells deficient in Chs2 showed clumpy growth and aberrant shape and size. Their septa were very thick; the primary septum was absent. Staining with WGA-gold complexes revealed a diffuse distribution of chitin in the septum, whereas chitin was normally located at the neck between mother cell and bud and in the wall of mother cells. Strains deficient in Chs3 exhibited minor abnormalities in budding pattern and shape. Their septa were thin and trilaminar. Staining for chitin revealed a thin line of the polysaccharide along the primary septum; no chitin was present elsewhere in the wall. Therefore, Chs2 is specific for primary septum formation, whereas Chs3 is responsible for chitin in the ring at bud emergence and in the cell wall. Chs3 is also required for chitin synthesized in the presence of alpha-pheromone or deposited in the cell wall of cdc mutants at nonpermissive temperature, and for chitosan in spore walls. Genetic evidence indicated that a mutant lacking all three chitin synthases was inviable; this was confirmed by constructing a triple mutant rescued by a plasmid carrying a CHS2 gene under control of a GAL1 promoter. Transfer of the mutant from galactose to glucose resulted in cell division arrest followed by cell death. We conclude that some chitin synthesis is essential for viability of yeast cells. PMID:2050738

  6. Nanoparticle Facilitated Extracellular Electron Transfer in Microbial Fuel Cells

    DTIC Science & Technology

    2014-10-13

    KEYWORDS: Bacteria , facilitated electron transport, electrochemically active, iron sulfide, Shewanella Microbial fuel cells (MFCs) are capable of...to MFC technology is the unique capability of electrochemically active bacteria , such as Shewanella and Geobacter, to divert electrons from the...finger electrode by reactive ion etching. The electrochemical measurements were Figure 1. Current and cell morphology changes at early stage of

  7. MAPK cell-cycle regulation in Saccharomyces cerevisiae and Candida albicans.

    PubMed

    Correia, Inês; Alonso-Monge, Rebeca; Pla, Jesús

    2010-07-01

    The cell cycle is the sequential set of events that living cells undergo in order to duplicate. This process must be tightly regulated as alterations may lead to diseases such as cancer. The molecular events that control the cell cycle are directional and involve regulatory molecules such as cyclins and cyclin-dependent kinases (CDKs). The budding yeast Saccharomyces cerevisiae has become a model to study this complex system since it shares several mechanisms with higher eukaryotes. Signal transduction pathways are biochemical mechanisms that sense environmental changes and there is recent evidence that they control the progression through the cell cycle in response to several stimuli. In response to pheromone, the budding yeast arrests the cell cycle in the G1 phase at the START stage. Activation of the pheromone response pathway leads to the phosphorylation of Far1, which inhibits the function of complexes formed by G1 cyclins (Cln1 and Cln2) and the CDK (Cdc28), blocking the transition to the S phase. This response prepares the cells to fuse cytoplasms and nuclei to generate a diploid cell. Activation of the Hog1 MAP kinase in response to osmotic stress or arsenite leads to the transient arrest of the cell cycle in G1 phase, which is mediated by direct phosphorylation of the CDK inhibitor, Sic1, and by downregulation of cyclin expression. Osmotic stress also induces a delay in G2 phase by direct phosphorylation of Hsl7 via Hog1, which results in the accumulation of Swe1. As a consequence, cell cycle arrest allows cells to survive upon stress. Finally, cell wall damage can induce cell cycle arrest at G2 via the cell integrity MAPK Slt2. By linking MAPK signal transduction pathways to the cell cycle machinery, a tight and precise control of the cell division takes place in response to environmental changes. Research into similar MAPK-mediated cell cycle regulation in the opportunistic pathogen Candida albicans may result in the development of new antifungal

  8. Microbial diversity and population dynamics of activated sludge microbial communities participating in electricity generation in microbial fuel cells.

    PubMed

    Ki, D; Park, J; Lee, J; Yoo, K

    2008-01-01

    In this study, we performed microbial community analysis to examine microbial diversity and community structure in microbial fuel cells (MFCs) seeded with activated sludge from a municipal wastewater treatment plant in South Korea. Because anode-attached biofilm populations are particularly important in electricity transfer, the ecological characteristics of anode-attached biofilm microbes were explored and compared with those of microbes grown in suspension in an anode chamber. 16S rDNA-based community analysis showed that the degree of diversity in anode-attached biofilms was greater than that of the originally seeded activated sludge as well as that of the suspension-grown microbes in the anode bottle. In addition, Bacteroidetes and Clostridia grew preferentially during MFC electricity generation. Further phylogenetic analysis revealed that the anode biofilm populations described in this work are phylogenetically distant from previously characterized MFC anode biofilm microbes. These findings suggest that a phylogenetically diverse set of microbes can be involved in the electricity generation of MFC anode compartments, and that increased microbial diversity in anode biofilms may help to stabilize electricity production in the MFC. Copyright (c) IWA Publishing 2008.

  9. Functionally stable and phylogenetically diverse microbial enrichments from microbial fuel cells during wastewater treatment.

    PubMed

    Ishii, Shun'ichi; Suzuki, Shino; Norden-Krichmar, Trina M; Nealson, Kenneth H; Sekiguchi, Yuji; Gorby, Yuri A; Bretschger, Orianna

    2012-01-01

    Microbial fuel cells (MFCs) are devices that exploit microorganisms as biocatalysts to recover energy from organic matter in the form of electricity. One of the goals of MFC research is to develop the technology for cost-effective wastewater treatment. However, before practical MFC applications are implemented it is important to gain fundamental knowledge about long-term system performance, reproducibility, and the formation and maintenance of functionally-stable microbial communities. Here we report findings from a MFC operated for over 300 days using only primary clarifier effluent collected from a municipal wastewater treatment plant as the microbial resource and substrate. The system was operated in a repeat-batch mode, where the reactor solution was replaced once every two weeks with new primary effluent that consisted of different microbial and chemical compositions with every batch exchange. The turbidity of the primary clarifier effluent solution notably decreased, and 97% of biological oxygen demand (BOD) was removed after an 8-13 day residence time for each batch cycle. On average, the limiting current density was 1000 mA/m(2), the maximum power density was 13 mW/m(2), and coulombic efficiency was 25%. Interestingly, the electrochemical performance and BOD removal rates were very reproducible throughout MFC operation regardless of the sample variability associated with each wastewater exchange. While MFC performance was very reproducible, the phylogenetic analyses of anode-associated electricity-generating biofilms showed that the microbial populations temporally fluctuated and maintained a high biodiversity throughout the year-long experiment. These results suggest that MFC communities are both self-selecting and self-optimizing, thereby able to develop and maintain functional stability regardless of fluctuations in carbon source(s) and regular introduction of microbial competitors. These results contribute significantly toward the practical application

  10. Functionally Stable and Phylogenetically Diverse Microbial Enrichments from Microbial Fuel Cells during Wastewater Treatment

    PubMed Central

    Ishii, Shun'ichi; Suzuki, Shino; Norden-Krichmar, Trina M.; Nealson, Kenneth H.; Sekiguchi, Yuji; Gorby, Yuri A.; Bretschger, Orianna

    2012-01-01

    Microbial fuel cells (MFCs) are devices that exploit microorganisms as biocatalysts to recover energy from organic matter in the form of electricity. One of the goals of MFC research is to develop the technology for cost-effective wastewater treatment. However, before practical MFC applications are implemented it is important to gain fundamental knowledge about long-term system performance, reproducibility, and the formation and maintenance of functionally-stable microbial communities. Here we report findings from a MFC operated for over 300 days using only primary clarifier effluent collected from a municipal wastewater treatment plant as the microbial resource and substrate. The system was operated in a repeat-batch mode, where the reactor solution was replaced once every two weeks with new primary effluent that consisted of different microbial and chemical compositions with every batch exchange. The turbidity of the primary clarifier effluent solution notably decreased, and 97% of biological oxygen demand (BOD) was removed after an 8–13 day residence time for each batch cycle. On average, the limiting current density was 1000 mA/m2, the maximum power density was 13 mW/m2, and coulombic efficiency was 25%. Interestingly, the electrochemical performance and BOD removal rates were very reproducible throughout MFC operation regardless of the sample variability associated with each wastewater exchange. While MFC performance was very reproducible, the phylogenetic analyses of anode-associated electricity-generating biofilms showed that the microbial populations temporally fluctuated and maintained a high biodiversity throughout the year-long experiment. These results suggest that MFC communities are both self-selecting and self-optimizing, thereby able to develop and maintain functional stability regardless of fluctuations in carbon source(s) and regular introduction of microbial competitors. These results contribute significantly toward the practical application of

  11. Batteryless, wireless sensor powered by a sediment microbial fuel cell.

    PubMed

    Donovan, Conrad; Dewan, Alim; Heo, Deukhyoun; Beyenal, Haluk

    2008-11-15

    Sediment microbial fuel cells (SMFCs) are considered to be an alternative renewable power source for remote monitoring. There are two main challenges to using SMFCs as power sources: 1) a SMFC produces a low potential at which most sensor electronics do not operate, and 2) a SMFC cannot provide continuous power, so energy from the SMFC must be stored and then used to repower sensor electronics intermittently. In this study, we developed a SMFC and a power management system (PMS) to power a batteryless, wireless sensor. A SMFC operating with a microbial anode and cathode, located in the Palouse River, Pullman, Washington, U.S.A., was used to demonstrate the utility of the developed system. The designed PMS stored microbial energy and then started powering the wireless sensor when the SMFC potential reached 320 mV. It continued powering until the SMFC potential dropped below 52 mV. The system was repowered when the SMFC potential increased to 320 mV, and this repowering continued as long as microbial reactions continued. We demonstrated that a microbial fuel cell with a microbial anode and cathode can be used as an effective renewable power source for remote monitoring using custom-designed electronics.

  12. Functional Assembly of Minicellulosomes on the Saccharomyces cerevisiae Cell Surface for Cellulose Hydrolysis and Ethanol Production▿

    PubMed Central

    Tsai, Shen-Long; Oh, Jeongseok; Singh, Shailendra; Chen, Ruizhen; Chen, Wilfred

    2009-01-01

    We demonstrated the functional display of a miniscaffoldin on the Saccharomyces cerevisiae cell surface consisting of three divergent cohesin domains from Clostridium thermocellum (t), Clostridium cellulolyticum (c), and Ruminococcus flavefaciens (f). Incubation with Escherichia coli lysates containing an endoglucanase (CelA) fused with a dockerin domain from C. thermocellum (At), an exoglucanase (CelE) from C. cellulolyticum fused with a dockerin domain from the same species (Ec), and an endoglucanase (CelG) from C. cellulolyticum fused with a dockerin domain from R. flavefaciens (Gf) resulted in the assembly of a functional minicellulosome on the yeast cell surface. The displayed minicellulosome retained the synergistic effect for cellulose hydrolysis. When a β-glucosidase (BglA) from C. thermocellum tagged with the dockerin from R. flavefaciens was used in place of Gf, cells displaying the new minicellulosome exhibited significantly enhanced glucose liberation and produced ethanol directly from phosphoric acid-swollen cellulose. The final ethanol concentration of 3.5 g/liter was 2.6-fold higher than that obtained by using the same amounts of added purified cellulases. The overall yield was 0.49 g of ethanol produced per g of carbohydrate consumed, which corresponds to 95% of the theoretical value. This result confirms that simultaneous and synergistic saccharification and fermentation of cellulose to ethanol can be efficiently accomplished with a yeast strain displaying a functional minicellulosome containing all three required cellulolytic enzymes. PMID:19684173

  13. Saccharomyces cerevisiae STE6 gene product: a novel pathway for protein export in eukaryotic cells.

    PubMed Central

    Kuchler, K; Sterne, R E; Thorner, J

    1989-01-01

    Saccharomyces cerevisiae MATa cells release a lipopeptide mating pheromone, a-factor. Radiolabeling and immunoprecipitation show that MATa ste6 mutants produce pro-a-factor and mature a-factor intracellularly, but little or no extracellular pheromone. Normal MATa cells carrying a multicopy plasmid containing both MFa1 (pro-a-factor structural gene) and the STE6 gene secrete a-factor at least five times faster than the same cells carrying only MFa1 in the same vector. The nucleotide sequence of the STE6 gene predicts a 1290 residue polypeptide with multiple membrane spanning segments and two hydrophilic domains, each strikingly homologous to a set of well-characterized prokaryotic permeases (including hlyB, oppD, hisP, malK and pstB) and sharing even greater identity with mammalian mdr (multiple drug resistance) transporters. These results suggest that the STE6 protein in yeast, and possibly mdr in animals, is a transmembrane translocator that exports polypeptides by a route independent of the classical secretory pathway. Images PMID:2686977

  14. Localization of Saccharomyces cerevisiae Protein Phosphatase 2A Subunits throughout Mitotic Cell Cycle

    PubMed Central

    Gentry, Matthew S.; Hallberg, Richard L.

    2002-01-01

    Protein phosphatase 2A (PP2A) regulates a broad spectrum of cellular processes. This enzyme is a collection of varied heterotrimeric complexes, each composed of a catalytic (C) and regulatory (B) subunit bound together by a structural (A) subunit. To understand the cell cycle dynamics of this enzyme population, we carried out quantitative and qualitative analyses of the PP2A subunits of Saccharomyces cerevisiae. We found the following: the level of each subunit remained constant throughout the cell cycle; there is at least 10 times more of one of the regulatory subunits (Rts1p) than the other (Cdc55p); Tpd3p, the structural subunit, is limiting for both catalytic and regulatory subunit binding. Using green fluorescent protein-tagged forms of each subunit, we monitored the sites of significant accumulation of each protein throughout the cell cycle. The two regulatory subunits displayed distinctly different dynamic localization patterns that overlap with the A and C subunits at the bud tip, kinetochore, bud neck, and nucleus. Using strains null for single subunit genes, we confirmed the hypothesis that regulatory subunits determine sites of PP2A accumulation. Although Rts1p and Tpd3p required heterotrimer formation to achieve normal localization, Cdc55p achieved its normal localization in the absence of either an A or C subunit. PMID:12388751

  15. Cell-autonomous mechanisms of chronological aging in the yeast Saccharomyces cerevisiae

    PubMed Central

    Arlia-Ciommo, Anthony; Leonov, Anna; Piano, Amanda; Svistkova, Veronika; Titorenko, Vladimir I.

    2014-01-01

    A body of evidence supports the view that the signaling pathways governing cellular aging - as well as mechanisms of their modulation by longevity-extending genetic, dietary and pharmacological interventions - are conserved across species. The scope of this review is to critically analyze recent advances in our understanding of cell-autonomous mechanisms of chronological aging in the budding yeast Saccharomyces cerevisiae. Based on our analysis, we propose a concept of a biomolecular network underlying the chronology of cellular aging in yeast. The concept posits that such network progresses through a series of lifespan checkpoints. At each of these checkpoints, the intracellular concentrations of some key intermediates and products of certain metabolic pathways - as well as the rates of coordinated flow of such metabolites within an intricate network of intercompartmental communications - are monitored by some checkpoint-specific ʺmaster regulatorʺ proteins. The concept envisions that a synergistic action of these master regulator proteins at certain early-life and late-life checkpoints modulates the rates and efficiencies of progression of such processes as cell metabolism, growth, proliferation, stress resistance, macromolecular homeostasis, survival and death. The concept predicts that, by modulating these vital cellular processes throughout lifespan (i.e., prior to an arrest of cell growth and division, and following such arrest), the checkpoint-specific master regulator proteins orchestrate the development and maintenance of a pro- or anti-aging cellular pattern and, thus, define longevity of chronologically aging yeast. PMID:28357241

  16. Differential importance of trehalose in stress resistance in fermenting and nonfermenting Saccharomyces cerevisiae cells.

    PubMed

    Van Dijck, P; Colavizza, D; Smet, P; Thevelein, J M

    1995-01-01

    The trehalose content in laboratory and industrial baker's yeast is widely believed to be a major determinant of stress resistance. Fresh and dried baker's yeast is cultured to obtain a trehalose content of more than 10% of the dry weight. Initiation of fermentation, e.g., during dough preparation, is associated with a rapid loss of stress resistance and a rapid mobilization of trehalose. Using specific Saccharomyces cerevisiae mutants affected in trehalose metabolism, we confirm the correlation between trehalose content and stress resistance but only in the absence of fermentation. We demonstrate that both phenomena can be dissociated clearly once the cells initiate fermentation. This was accomplished both for cells with moderate trehalose levels grown under laboratory conditions and for cells with trehalose contents higher than 10% obtained under pilot-scale conditions. Retention of a high trehalose level during fermentation also does not prevent the loss of fermentation capacity during preparation of frozen doughs. Although higher trehalose levels are always correlated with higher stress resistance before the addition of fermentable sugar, our results show that the initiation of fermentation causes the disappearance of any other factor(s) required for the maintenance of stress resistance, even in the presence of a high trehalose content.

  17. Raspberry wine fermentation with suspended and immobilized yeast cells of two strains of Saccharomyces cerevisiae.

    PubMed

    Djordjević, Radovan; Gibson, Brian; Sandell, Mari; de Billerbeck, Gustavo M; Bugarski, Branko; Leskošek-Čukalović, Ida; Vunduk, Jovana; Nikićević, Ninoslav; Nedović, Viktor

    2015-01-01

    The objectives of this study were to assess the differences in fermentative behaviour of two different strains of Saccharomyces cerevisiae (EC1118 and RC212) and to determine the differences in composition and sensory properties of raspberry wines fermented with immobilized and suspended yeast cells of both strains at 15 °C. Analyses of aroma compounds, glycerol, acetic acid and ethanol, as well as the kinetics of fermentation and a sensory evaluation of the wines, were performed. All fermentations with immobilized yeast cells had a shorter lag phase and faster utilization of sugars and ethanol production than those fermented with suspended cells. Slower fermentation kinetics were observed in all the samples that were fermented with strain RC212 (suspended and immobilized) than in samples fermented with strain EC1118. Significantly higher amounts of acetic acid were detected in all samples fermented with strain RC212 than in those fermented with strain EC1118 (0.282 and 0.602 g/l, respectively). Slightly higher amounts of glycerol were observed in samples fermented with strain EC1118 than in those fermented with strain RC212.

  18. Proteomic analysis reveals complex metabolic regulation in Saccharomyces cerevisiae cells against multiple inhibitors stress.

    PubMed

    Lv, Ya-Jin; Wang, Xin; Ma, Qian; Bai, Xue; Li, Bing-Zhi; Zhang, Weiwen; Yuan, Ying-Jin

    2014-03-01

    Toxic compounds including acids, furans, and phenols (AFP) were generated from the pretreatment of lignocellulose. We cultivated Saccharomyces cerevisiae cells in a batch mode, besides the cell culture of original yeast strain in AFP-free medium which was referred as C0, three independent subcultures were cultivated under multiple inhibitors AFP and were referred as C1, C2, and C3 in time sequence. Comparing to C0, the cell density was lowered while the ethanol yield was maintained stably in the three yeast cultures under AFP stress, and the lag phase of C1 was extended while the lag phases of C2 and C3 were not extended. In proteomic analysis, 194 and 215 unique proteins were identified as differently expressed proteins at lag phase and exponential phase, respectively. Specifically, the yeast cells co-regulated protein folding and protein synthesis process to prevent the generation of misfolded proteins and to save cellular energy, they increased the activity of glycolysis, redirected metabolic flux towards phosphate pentose pathway and the biosynthesis of ethanol instead of the biosynthesis of glycerol and acetic acid, and they upregulated several oxidoreductases especially at lag phase and induced programmed cell death at exponential phase. When the yeast cells were cultivated under AFP stress, the new metabolism homeostasis in favor of cellular energy and redox homeostasis was generated in C1, then it was inherited and optimized in C2 and C3, enabling the yeast cells in C2 and C3 to enter the exponential phase in a short period after inoculation, which thus significantly shortened the fermentation time.

  19. Electricity generation and microbial community changes in microbial fuel cells packed with different anodic materials.

    PubMed

    Sun, Yanmei; Wei, Jincheng; Liang, Peng; Huang, Xia

    2011-12-01

    Four materials, carbon felt cube (CFC), granular graphite (GG), granular activated carbon (GAC) and granular semicoke (GS) were tested as packed anodic materials to seek a potentially practical material for microbial fuel cells (MFCs). The microbial community and its correlation with the electricity generation performance of MFCs were explored. The maximum power density was found in GAC, followed by CFC, GG and GS. In GAC and CFC packed MFCs, Geobacter was the dominating genus, while Azospira was the most populous group in GG. Results further indicated that GAC was the most favorable for Geobacter adherence and growth, and the maximum power densities had positive correlation with the total biomass and the relative abundance of Geobacter, but without apparent correlation with the microbial diversity. Due to the low content of Geobacter in GS, power generated in this system may be attributed to other microorganisms such as Synergistes, Bacteroidetes and Castellaniella.

  20. Microbial community structure of different electrode materials in constructed wetland incorporating microbial fuel cell.

    PubMed

    Wang, Junfeng; Song, Xinshan; Wang, Yuhui; Abayneh, Befkadu; Ding, Yi; Yan, Denghua; Bai, Junhong

    2016-12-01

    The microbial fuel cell coupled with constructed wetland (CW-MFC) microcosms were operated under fed-batch mode for evaluating the effect of electrode materials on bioelectricity generation and microbial community composition. Experimental results indicated that the bioenergy output in CW-MFC increased with the substrate concentration; maximum average voltage (177mV) was observed in CW-MFC with carbon fiber felt (CFF). In addition, the four different materials resulted in the formation of significantly different microbial community distribution around the anode electrode. The relative abundance of Proteobacteria in CFF and foamed nickel (FN) was significantly higher than that in stainless steel mesh (SSM) and graphite rod (GR) samples. Notably, the findings indicate that CW-MFC utilizing FN anode electrode could apparently improve relative abundance of Dechloromonas, which has been regarded as a denitrifying and phosphate accumulating microorganism.

  1. Simultaneous microbial and electrochemical reductions of vanadium (V) with bioelectricity generation in microbial fuel cells.

    PubMed

    Zhang, Baogang; Tian, Caixing; Liu, Ying; Hao, Liting; Liu, Ye; Feng, Chuanping; Liu, Yuqian; Wang, Zhongli

    2015-03-01

    Simultaneous microbial and electrochemical reductions of vanadium (V) with bioelectricity generation were realized in microbial fuel cells (MFCs). With initial V(V) concentrations of 75 mg/l and 150 mg/l in anolyte and catholyte, respectively, stable power output of 419±11 mW/m(2) was achieved. After 12h operation, V(V) concentration in the catholyte decreased to the value similar to that of the initial one in the anolyte, meanwhile it was nearly reduced completely in the anolyte. V(IV) was the main reduction product, which subsequently precipitated, acquiring total vanadium removal efficiencies of 76.8±2.9%. Microbial community analysis revealed the emergence of the new species of Deltaproteobacteria and Bacteroidetes as well as the enhanced Spirochaetes mainly functioned in the anode. This study opens new pathways to successful remediation of vanadium contamination. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Microbially-reduced graphene scaffolds to facilitate extracellular electron transfer in microbial fuel cells.

    PubMed

    Yuan, Yong; Zhou, Shungui; Zhao, Bo; Zhuang, Li; Wang, Yueqiang

    2012-07-01

    A one-pot method is exploited by adding graphene oxide (GO) and acetate into an microbial fuel cell (MFC) in which GO is microbially reduced, leading to in situ construction of a bacteria/graphene network in the anode. The obtained microbially reduced graphene (MRG) exhibits comparable conductivity and physical characteristics to the chemically reduced graphene. Electrochemical measurements reveal that the number of exoelectrogens involved in extracellular electron transfer (EET) to the solid electrode, increases due to the presence of graphene scaffolds, and the EET is facilitated in terms of electron transfer kinetics. As a result, the maximum power density of the MFC is enhanced by 32% (from 1440 to 1905 mW m(-2)) and the coulombic efficiency is improved by 80% (from 30 to 54%). The results demonstrate that the construction of the bacteria/graphene network is an effective alternative to improve the MFC performance. Copyright © 2012 Elsevier Ltd. All rights reserved.

  3. Fast “Feast/Famine” Cycles for Studying Microbial Physiology Under Dynamic Conditions: A Case Study with Saccharomyces cerevisiae

    PubMed Central

    Suarez-Mendez, Camilo A.; Sousa, Andre; Heijnen, Joseph J.; Wahl, Aljoscha

    2014-01-01

    Microorganisms are constantly exposed to rapidly changing conditions, under natural as well as industrial production scale environments, especially due to large-scale substrate mixing limitations. In this work, we present an experimental approach based on a dynamic feast/famine regime (400 s) that leads to repetitive cycles with moderate changes in substrate availability in an aerobic glucose cultivation of Saccharomyces cerevisiae. After a few cycles, the feast/famine produced a stable and repetitive pattern with a reproducible metabolic response in time, thus providing a robust platform for studying the microorganism’s physiology under dynamic conditions. We found that the biomass yield was slightly reduced (−5%) under the feast/famine regime, while the averaged substrate and oxygen consumption as well as the carbon dioxide production rates were comparable. The dynamic response of the intracellular metabolites showed specific differences in comparison to other dynamic experiments (especially stimulus-response experiments, SRE). Remarkably, the frequently reported ATP paradox observed in single pulse experiments was not present during the repetitive perturbations applied here. We found that intracellular dynamic accumulations led to an uncoupling of the substrate uptake rate (up to 9-fold change at 20 s.) Moreover, the dynamic profiles of the intracellular metabolites obtained with the feast/famine suggest the presence of regulatory mechanisms that resulted in a delayed response. With the feast famine setup many cellular states can be measured at high frequency given the feature of reproducible cycles. The feast/famine regime is thus a versatile platform for systems biology approaches, which can help us to identify and investigate metabolite regulations under realistic conditions (e.g., large-scale bioreactors or natural environments). PMID:24957030

  4. Population dynamics of electrogenic microbial communities in microbial fuel cells started with three different inoculum sources.

    PubMed

    Ishii, Shun'ichi; Suzuki, Shino; Yamanaka, Yuko; Wu, Angela; Nealson, Kenneth H; Bretschger, Orianna

    2017-10-01

    Microbial fuel cells (MFCs) are one of the bioelectrochemical systems that exploit microorganisms as biocatalysts to degrade organic matters and recover energy as electric power. Here, we explored how the established electrogenic microbial communities were influenced by three different inoculum sources; anaerobic sludge of the wastewater plant, rice paddy field soil, and coastal lagoon sediment. We periodically characterized both electricity generation with sucrose consumption and 16S rRNA-basis microbial community composition. The electrochemical features of MFCs were slightly different among three inocula, and the lagoon sediment-inoculated MFC showed the highest performance in terms of the treatment time. Meanwhile, although the inoculated microbial communities were highly diverse and quite different, only twelve genera affiliated with δ-Proteobacteria, γ-Proteobacteria, Bacilli, Clostridia/Negativicutes or Bacteroidetes were abundantly enriched in all MFC anode communities. Within them, several fermentative genera were clearly different due to the inocula, while the inocula-specific phylotypes were identified in an electrogenic genus Geobacter. The relative abundances of phylotypes closely-related to Geobacter metallireducens were increased in later stages of all the sucrose-fed MFCs. These results indicate that key microbial members for the functional electrogenic community widely exist in natural ecosystems, but the community members presenting in inoculum sources affected the MFC performances. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Protozoan grazing reduces the current output of microbial fuel cells.

    PubMed

    Holmes, Dawn E; Nevin, Kelly P; Snoeyenbos-West, Oona L; Woodard, Trevor L; Strickland, Justin N; Lovley, Derek R

    2015-10-01

    Several experiments were conducted to determine whether protozoan grazing can reduce current output from sediment microbial fuel cells. When marine sediments were amended with eukaryotic inhibitors, the power output from the fuel cells increased 2-5-fold. Quantitative PCR showed that Geobacteraceae sequences were 120 times more abundant on anodes from treated fuel cells compared to untreated fuel cells, and that Spirotrichea sequences in untreated fuel cells were 200 times more abundant on anode surfaces than in the surrounding sediments. Defined studies with current-producing biofilms of Geobacter sulfurreducens and pure cultures of protozoa demonstrated that protozoa that were effective in consuming G. sulfurreducens reduced current production up to 91% when added to G. sulfurreducens fuel cells. These results suggest that anode biofilms are an attractive food source for protozoa and that protozoan grazing can be an important factor limiting the current output of sediment microbial fuel cells. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  6. Recognition of Microbial Glycolipids by Natural Killer T Cells

    PubMed Central

    Zajonc, Dirk M.; Girardi, Enrico

    2015-01-01

    T cells can recognize microbial antigens when presented by dedicated antigen-presenting molecules. While peptides are presented by classical members of the major histocompatibility complex (MHC) family (MHC I and II), lipids, glycolipids, and lipopeptides can be presented by the non-classical MHC member, CD1. The best studied subset of lipid-reactive T cells are type I natural killer T (iNKT) cells that recognize a variety of different antigens when presented by the non-classical MHCI homolog CD1d. iNKT cells have been shown to be important for the protection against various microbial pathogens, including B. burgdorferi, the causative agents of Lyme disease, and S. pneumoniae, which causes pneumococcal meningitis and community-acquired pneumonia. Both pathogens carry microbial glycolipids that can trigger the T cell antigen receptor (TCR), leading to iNKT cell activation. iNKT cells have an evolutionary conserved TCR alpha chain, yet retain the ability to recognize structurally diverse glycolipids. They do so using a conserved recognition mode, in which the TCR enforces a conserved binding orientation on CD1d. TCR binding is accompanied by structural changes within the TCR binding site of CD1d, as well as the glycolipid antigen itself. In addition to direct recognition of microbial antigens, iNKT cells can also be activated by a combination of cytokines (IL-12/IL-18) and TCR stimulation. Many microbes carry TLR antigens, and microbial infections can lead to TLR activation. The subsequent cytokine response in turn lower the threshold of TCR-mediated iNKT cell activation, especially when weak microbial or even self-antigens are presented during the cause of the infection. In summary, iNKT cells can be directly activated through TCR triggering of strong antigens, while cytokines produced by the innate immune response may be necessary for TCR triggering and iNKT cell activation in the presence of weak antigens. Here, we will review the molecular basis of iNKT cell

  7. Polarized Growth Controls Cell Shape and Bipolar Bud Site Selection in Saccharomyces cerevisiae

    PubMed Central

    Sheu, Yi-Jun; Barral, Yves; Snyder, Michael

    2000-01-01

    We examined the relationship between polarized growth and division site selection, two fundamental processes important for proper development of eukaryotes. Diploid Saccharomyces cerevisiae cells exhibit an ellipsoidal shape and a specific division pattern (a bipolar budding pattern). We found that the polarity genes SPA2, PEA2, BUD6, and BNI1 participate in a crucial step of bud morphogenesis, apical growth. Deleting these genes results in round cells and diminishes bud elongation in mutants that exhibit pronounced apical growth. Examination of distribution of the polarized secretion marker Sec4 demonstrates that spa2Δ, pea2Δ, bud6Δ, and bni1Δ mutants fail to concentrate Sec4 at the bud tip during apical growth and at the division site during repolarization just prior to cytokinesis. Moreover, cell surface expansion is not confined to the distal tip of the bud in these mutants. In addition, we found that the p21-activated kinase homologue Ste20 is also important for both apical growth and bipolar bud site selection. We further examined how the duration of polarized growth affects bipolar bud site selection by using mutations in cell cycle regulators that control the timing of growth phases. The grr1Δ mutation enhances apical growth by stabilizing G1 cyclins and increases the distal-pole budding in diploids. Prolonging polarized growth phases by disrupting the G2/M cyclin gene CLB2 enhances the accuracy of bud site selection in wild-type, spa2Δ, and ste20Δ cells, whereas shortening the polarized growth phases by deleting SWE1 decreases the fidelity of bipolar budding. This study reports the identification of components required for apical growth and demonstrates the critical role of polarized growth in bipolar bud site selection. We propose that apical growth and repolarization at the site of cytokinesis are crucial for establishing spatial cues used by diploid yeast cells to position division planes. PMID:10866679

  8. High-cell-density cultivation for co-production of ergosterol and reduced glutathione by Saccharomyces cerevisiae.

    PubMed

    Shang, Fei; Wang, Zheng; Tan, Tianwei

    2008-01-01

    Two different high-cell-density cultivation processes based on the mutant Saccharomyces cerevisiae GE-2 for simultaneous production of glutathione and ergosterol were investigated. Compared with keeping the ethanol volumetric concentration at a constant low level, feedback control of glucose feeding rate (F) by keeping the descending rate of ethanol volumetric concentration (DeltaE/Deltat) between -0.1% and 0.15% per hour was much more efficient to achieve a high glutathione and ergosterol productivity. This bioprocess overcomes some disadvantages of traditional S. cerevisiae-based cultivation process, especially shortening cultivation period and making the cultivation process steady-going. A classical on or off controller was used to manipulate F to maintain DeltaE/Deltat at its set point. The dry cell weight, glutathione yield and ergosterol yield reached 110.0 +/- 2.6 g/l, 2,280 +/- 76 mg/l, and 1,510 +/- 28 mg/l in 32 h, respectively.

  9. Characterization of Fluorescent Proteins for Three- and Four-Color Live-Cell Imaging in S. cerevisiae

    PubMed Central

    Higuchi-Sanabria, Ryo; Garcia, Enrique J.; Tomoiaga, Delia; Munteanu, Emilia L.; Feinstein, Paul; Pon, Liza A.

    2016-01-01

    Saccharomyces cerevisiae are widely used for imaging fluorescently tagged protein fusions. Fluorescent proteins can easily be inserted into yeast genes at their chromosomal locus, by homologous recombination, for expression of tagged proteins at endogenous levels. This is especially useful for incorporation of multiple fluorescent protein fusions into a single strain, which can be challenging in organisms where genetic manipulation is more complex. However, the availability of optimal fluorescent protein combinations for 3-color imaging is limited. Here, we have characterized a combination of fluorescent proteins, mTFP1/mCitrine/mCherry for multicolor live cell imaging in S. cerevisiae. This combination can be used with conventional blue dyes, such as DAPI, for potential four-color live cell imaging. PMID:26727004

  10. Expression of aldehyde dehydrogenase 6 reduces inhibitory effect of furan derivatives on cell growth and ethanol production in Saccharomyces cerevisiae.

    PubMed

    Park, Seong-Eon; Koo, Hyun Min; Park, Young Kyoung; Park, Sung Min; Park, Jae Chan; Lee, Oh-Kyu; Park, Yong-Cheol; Seo, Jin-Ho

    2011-05-01

    Yeast dehydrogenases and reductases were overexpressed in Saccharomyces cerevisiae D452-2 to detoxify 2-furaldehyde (furfural) and 5-hydroxymethyl furaldehyde (HMF), two potent toxic chemicals present in acid-hydrolyzed cellulosic biomass, and hence improve cell growth and ethanol production. Among those enzymes, aldehyde dehydrogenase 6 (ALD6) played the dual roles of direct oxidation of furan derivatives and supply of NADPH cofactor to their reduction reactions. Batch fermentation of S. cerevisiae D452-2/pH-ALD6 in the presence of 2g/L furfural and 0.5 g/L HMF resulted in 20-30% increases in specific growth rate, ethanol concentration and ethanol productivity, compared with those of the wild type strain. It was proposed that overexpression of ALD6 could recover the yeast cell metabolism and hence increase ethanol production from lignocellulosic biomass containing furan-derived inhibitors. Copyright © 2011 Elsevier Ltd. All rights reserved.

  11. COLCEMID INHIBITION OF CELL GROWTH AND THE CHARACTERIZATION OF A COLCEMID-BINDING ACTIVITY IN SACCHAROMYCES CEREVISIAE

    PubMed Central

    Haber, James E.; Peloquin, John G.; Halvorson, Harlyn O.; Borisy, Gary G.

    1972-01-01

    Under restricted culture conditions, the growth and division of Saccharomyces cerevisiae was inhibited by the antimitotic drug Colcemid; in contrast, the related drug colchicine had no effect. The difference in the sensitivity of yeast to these two agents was not dependent on their ability to permeate the cell but rather reflected an inherent difference in the affinity of the two drugs for a cellular-binding site. The binding moiety was characterized by gel filtration as a macromolecule of approximately 110,000 mol wt with an affinity constant for Colcemid of 0.5 x 104 liters per mole; in addition, this macromolecule was retained by diethylaminoethyl (DEAE) ion exchangers. On the basis of these properties, the Colcemid-binding substance in S. cerevisiae cells was provisionally identified as microtubule subunits. PMID:4561943

  12. Characterization of Fluorescent Proteins for Three- and Four-Color Live-Cell Imaging in S. cerevisiae.

    PubMed

    Higuchi-Sanabria, Ryo; Garcia, Enrique J; Tomoiaga, Delia; Munteanu, Emilia L; Feinstein, Paul; Pon, Liza A

    2016-01-01

    Saccharomyces cerevisiae are widely used for imaging fluorescently tagged protein fusions. Fluorescent proteins can easily be inserted into yeast genes at their chromosomal locus, by homologous recombination, for expression of tagged proteins at endogenous levels. This is especially useful for incorporation of multiple fluorescent protein fusions into a single strain, which can be challenging in organisms where genetic manipulation is more complex. However, the availability of optimal fluorescent protein combinations for 3-color imaging is limited. Here, we have characterized a combination of fluorescent proteins, mTFP1/mCitrine/mCherry for multicolor live cell imaging in S. cerevisiae. This combination can be used with conventional blue dyes, such as DAPI, for potential four-color live cell imaging.

  13. Plasmonic cell nanocoating: a new concept for rapid microbial screening.

    PubMed

    Xu, Ke; Bui, Minh-Phuong N; Fang, Aiqin; Abbas, Abdennour

    2017-09-13

    Nanocoating of single microbial cells with gold nanostructures can confer optical, electrical, thermal, and mechanical properties to microorganisms, thus enabling new avenues for their control, study, application, and detection. Cell nanocoating is often performed using layer-by-layer (LbL) deposition. LbL is time-consuming and relies on nonspecific electrostatic interactions, which limit potential applications for microbial diagnostics. Here, we show that, by taking advantage of surface molecules densely present in the microbial outer layers, cell nanocoating with gold nanoparticles can be achieved within seconds using surface molecules, including disulfide- bond-containing (Dsbc) proteins and chitin. A simple activation of these markers and their subsequent interaction with gold nanoparticles allow specific microbial screening and quantification of bacteria and fungi within 5 and 30 min, respectively. The use of plasmonics and fluorescence as transduction methods offers a limit of detection below 35 cfu mL(-1) for E. coli bacteria and 1500 cfu mL(-1) for M. circinelloides fungi using a hand-held fluorescent reader. Graphical abstract A new concept for rapid microbial screening by targeting disulfide - bond-containing (Dsbc) proteins and chitin with reducing agents and gold nanoparticles.

  14. New integrative modules for multicolor-protein labeling and live-cell imaging in Saccharomyces cerevisiae.

    PubMed

    Malcova, Ivana; Farkasovsky, Marian; Senohrabkova, Lenka; Vasicova, Pavla; Hasek, Jiri

    2016-05-01

    Live-imaging analysis is performed in many laboratories all over the world. Various tools have been developed to enable protein labeling either in plasmid or genomic context in live yeast cells. Here, we introduce a set of nine integrative modules for the C-terminal gene tagging that combines three fluorescent proteins (FPs)-ymTagBFP, mCherry and yTagRFP-T with three dominant selection markers: geneticin, nourseothricin and hygromycin. In addition, the construction of two episomal modules for Saccharomyces cerevisiae with photostable yTagRFP-T is also referred to. Our cassettes with orange, red and blue FPs can be combined with other fluorescent probes like green fluorescent protein to prepare double- or triple-labeled strains for multicolor live-cell imaging. Primers for PCR amplification of the cassettes were designed in such a way as to be fully compatible with the existing PCR toolbox representing over 50 various integrative modules and also with deletion cassettes either for single or repeated usage to enable a cost-effective and an easy exchange of tags. New modules can also be used for biochemical analysis since antibodies are available for all three fluorescent probes. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  15. Modification of thiamine pyrophosphate dependent enzyme activity by oxythiamine in Saccharomyces cerevisiae cells.

    PubMed

    Tylicki, Adam; Czerniecki, Jan; Dobrzyn, Pawel; Matanowska, Agnieszka; Olechno, Anna; Strumilo, Slawomir

    2005-10-01

    Oxythiamine is an antivitamin derivative of thiamine that after phosphorylation to oxythiamine pyro phosphate can bind to the active centres of thiamine-dependent enzymes. In the present study, the effect of oxythiamine on the viability of Saccharomyces cerevisiae and the activity of thiamine pyrophosphate dependent enzymes in yeast cells has been investigated. We observed a decrease in pyruvate decarboxylase specific activity on both a control and an oxythiamine medium after the first 6 h of culture. The cytosolic enzymes transketolase and pyruvate decarboxylase decreased their specific activity in the presence of oxythiamine but only during the beginning of the cultivation. However, after 12 h of cultivation, oxythiamine-treated cells showed higher specific activity of cytosolic enzymes. More over, it was established by SDS-PAGE that the high specific activity of pyruvate decarboxylase was followed by an increase in the amount of the enzyme protein. In contrast, the mitochondrial enzymes, pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase complexes, were inhibited by oxythiamine during the entire experiment. Our results suggest that the observed strong decrease in growth rate and viability of yeast on medium with oxythiamine may be due to stronger inhibition of mitochondrial pyruvate dehydrogenase than of cytosolic enzymes.

  16. Physical, functional and structural characterization of the cell wall fractions from baker's yeast Saccharomyces cerevisiae.

    PubMed

    Borchani, Chema; Fonteyn, Fabienne; Jamin, Guilhem; Paquot, Michel; Thonart, Philippe; Blecker, Christophe

    2016-03-01

    The yeast cell wall of Saccharomyces cerevisiae is an important source of β-d-glucan, a glucose homopolymer with many functional, nutritional and human health benefits. In the present study, the yeast cell wall fractionation process involving enzymatic treatments (savinase and lipolase enzymes) affected most of the physical and functional characteristics of extracted fractions. Thus, the fractionation process showed that β-d-glucan fraction F4 had significantly higher swelling power and fat binding capacity compared to other fractions (F1, F2 and F3). It also exhibited a viscosity of 652.12mPas and a high degree of brightness of extracted β-d-glucan fraction. Moreover, the fractionation process seemed to have an effect on structural and thermal properties of extracted fractions. Overall, results showed that yeast β-d-glucan had good potential for use as a prebiotic ingredient in food, as well as medicinal and pharmaceutical products. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Cell population modeling and parameter estimation for continuous cultures of Saccharomyces cerevisiae.

    PubMed

    Mhaskar, Prashant; Hjortsø, Martin A; Henson, Michael A

    2002-01-01

    Saccharomyces cerevisiae is known to exhibit sustained oscillations in chemostats operated under aerobic and glucose-limited growth conditions. The oscillations are reflected both in intracellular and extracellular measurements. Our recent work has shown that unstructured cell population balance models are capable of generating sustained oscillations over an experimentally meaningful range of dilution rates. A disadvantage of such unstructured models is that they lack variables that can be compared directly to easily measured extracellular variables. Thus far, most of our work in model development has been aimed at achieving qualitative agreement with experimental data. In this paper, a segregated model with a simple structured description of the extracellular environment is developed and evaluated. The model accounts for the three most important metabolic pathways involved in cell growth with glucose substrate. As compared to completely unstructured models, the major advantage of the proposed model is that predictions of extracellular variables can be compared directly to experimental data. Consequently, the model structure is well suited for the application of estimation techniques aimed at determining unknown model parameters from available extracellular measurements. A steady-state parameter selection method developed in our group is extended to oscillatory dynamics to determine the parameters that can be estimated most reliably. The chosen parameters are estimated by solving a nonlinear programming problem formulated to minimize the difference between predictions and measurements of the extracellular variables. The efficiency of the parameter estimation scheme is demonstrated using simulated and experimental data.

  18. Accumulation of phosphorylated sphingoid long chain bases results in cell growth inhibition in Saccharomyces cerevisiae.

    PubMed Central

    Kim, S; Fyrst, H; Saba, J

    2000-01-01

    Sphingolipid metabolites in mammals can function as signaling molecules with cell-specific functions. In Saccharomyces cerevisiae, phosphorylated long chain bases, such as dihydrosphingosine 1-phosphate and phytosphingosine 1-phosphate, have also been implicated in stress responses. To further explore the biological roles of these molecules, we created disruption mutants for LCB4, LCB5, DPL1, YSR2, YSR3, and SUR2. LCB4 and LCB5 encode kinases that phosphorylate long chain bases. DPL1 and YSR2/YSR3 are involved in degradation of the phosphorylated long chain bases. SUR2 catalyzes conversion of dihydrosphingosine to phytosphingosine. We adapted an HPLC method to measure intracellular concentrations of the phosphorylated long chain bases. Double mutants of dpl1 and ysr2 were inviable, whereas dpl1 ysr2 lcb4 triple mutants were viable. Further, growth inhibition associated with accumulated phosphorylated long chain bases was observed in the triple mutant dpl1 ysr2 lcb4 overexpressing LCB4 or LCB5. These results indicate that phosphorylated long chain bases can inhibit cell growth. Mutants defective in both YSR2 and SUR2, which accumulated dihydrosphingosine 1-phosphate only, grew poorly. The phenotypes of the ysr2 sur2 mutants were suppressed by overexpression of DPL1. Our results clearly show that elevated levels of phosphorylated long chain bases have an antiproliferative effect in yeast. PMID:11102354

  19. [Compartmentalization of Spo11p in vegetative cells of yeast Saccharomyces cerevisiae].

    PubMed

    Komakhin, R A; Komakhina, V V

    2008-01-01

    Double-stranded DNA breaks are currently thought to initiate homologous DNA recombination during meiosis. These breaks are mediated by several proteins, the key protein is Spol1p. Spo11 proteins being encoded by the highly conserved orthologs of SPO11 are present in most eukaryotes ranging from plants to man and are structurally similar to the subunit A of the archaea topoisomerase VI. The SPO11 of S. cerevisiae is currently known to be expressed during prophase I. It encodes a topoisomerase II that is apparently active as a dimer. Neither its localization in the native cells nor its nuclear localisation signals have been described in the literature. We report the expression of the coding region of SPO11 and its truncated variants C-terminally tagged by the egfp reporter in yeast. As judged by the EGFP fluorescence, the Spo11 p-EGFP fusion was localized in vegetative yeast nuclei whereas Spo11pdelta-EGFP lacking 25 N-terminal amino acids of Spollp was localized in cytoplasm. Nineteen N-terminal amino acids of Spo11p fused to EGFP made some reporter to be localized in the nucleus. Thus, we conclude that N-terminal part of Spo11p is a nuclear localization signal that is not specific for prophase I and is used to import proteins in vegetative yeast cells.

  20. Continuous bioethanol production from oilseed rape straw hydrosylate using immobilised Saccharomyces cerevisiae cells.

    PubMed

    Mathew, Anil Kuruvilla; Crook, Mitch; Chaney, Keith; Humphries, Andrea Clare

    2014-02-01

    The aim of the study was to evaluate continuous bioethanol production from oilseed rape (OSR) straw hydrolysate using Saccharomyces cerevisiae cells immobilised in Lentikat® discs. The study evaluated the effect of dilution rate (0.25, 0.50, 0.75 and 1.00 h(-1)), substrate concentration (15, 22, 40 and 60 g L(-1)) and cell loading (0.03, 0.16 and 0.24 g d.c.w.mL(-1) Lentikat®) on bioethanol production. Volumetric productivity was found to increase with increasing substrate concentration from 15 g L(-1) to 60 g L(-1). A maximum volumetric productivity of 12.88 g L(-1)h(-1) was achieved at a substrate concentration of 60 g L(-1) and at a dilution rate of 0.5h(-1). An overall mass balance for bioethanol production was created to determine the energy recovery from bioethanol and concluded that a biorefinery approach might be the most appropriate option for maximising the energy recovery from OSR straw. Copyright © 2013 Elsevier Ltd. All rights reserved.

  1. Anodic microbial community diversity as a predictor of the power output of microbial fuel cells.

    PubMed

    Stratford, James P; Beecroft, Nelli J; Slade, Robert C T; Grüning, André; Avignone-Rossa, Claudio

    2014-03-01

    The relationship between the diversity of mixed-species microbial consortia and their electrogenic potential in the anodes of microbial fuel cells was examined using different diversity measures as predictors. Identical microbial fuel cells were sampled at multiple time-points. Biofilm and suspension communities were analysed by denaturing gradient gel electrophoresis to calculate the number and relative abundance of species. Shannon and Simpson indices and richness were examined for association with power using bivariate and multiple linear regression, with biofilm DNA as an additional variable. In simple bivariate regressions, the correlation of Shannon diversity of the biofilm and power is stronger (r=0.65, p=0.001) than between power and richness (r=0.39, p=0.076), or between power and the Simpson index (r=0.5, p=0.018). Using Shannon diversity and biofilm DNA as predictors of power, a regression model can be constructed (r=0.73, p<0.001). Ecological parameters such as the Shannon index are predictive of the electrogenic potential of microbial communities.

  2. Production Strategies and Applications of Microbial Single Cell Oils

    PubMed Central

    Ochsenreither, Katrin; Glück, Claudia; Stressler, Timo; Fischer, Lutz; Syldatk, Christoph

    2016-01-01

    Polyunsaturated fatty acids (PUFAs) of the ω-3 and ω-6 class (e.g., α-linolenic acid, linoleic acid) are essential for maintaining biofunctions in mammalians like humans. Due to the fact that humans cannot synthesize these essential fatty acids, they must be taken up from different food sources. Classical sources for these fatty acids are porcine liver and fish oil. However, microbial lipids or single cell oils, produced by oleaginous microorganisms such as algae, fungi and bacteria, are a promising source as well. These single cell oils can be used for many valuable chemicals with applications not only for nutrition but also for fuels and are therefore an ideal basis for a bio-based economy. A crucial point for the establishment of microbial lipids utilization is the cost-effective production and purification of fuels or products of higher value. The fermentative production can be realized by submerged (SmF) or solid state fermentation (SSF). The yield and the composition of the obtained microbial lipids depend on the type of fermentation and the particular conditions (e.g., medium, pH-value, temperature, aeration, nitrogen source). From an economical point of view, waste or by-product streams can be used as cheap and renewable carbon and nitrogen sources. In general, downstream processing costs are one of the major obstacles to be solved for full economic efficiency of microbial lipids. For the extraction of lipids from microbial biomass cell disruption is most important, because efficiency of cell disruption directly influences subsequent downstream operations and overall extraction efficiencies. A multitude of cell disruption and lipid extraction methods are available, conventional as well as newly emerging methods, which will be described and discussed in terms of large scale applicability, their potential in a modern biorefinery and their influence on product quality. Furthermore, an overview is given about applications of microbial lipids or derived fatty

  3. Production Strategies and Applications of Microbial Single Cell Oils.

    PubMed

    Ochsenreither, Katrin; Glück, Claudia; Stressler, Timo; Fischer, Lutz; Syldatk, Christoph

    2016-01-01

    Polyunsaturated fatty acids (PUFAs) of the ω-3 and ω-6 class (e.g., α-linolenic acid, linoleic acid) are essential for maintaining biofunctions in mammalians like humans. Due to the fact that humans cannot synthesize these essential fatty acids, they must be taken up from different food sources. Classical sources for these fatty acids are porcine liver and fish oil. However, microbial lipids or single cell oils, produced by oleaginous microorganisms such as algae, fungi and bacteria, are a promising source as well. These single cell oils can be used for many valuable chemicals with applications not only for nutrition but also for fuels and are therefore an ideal basis for a bio-based economy. A crucial point for the establishment of microbial lipids utilization is the cost-effective production and purification of fuels or products of higher value. The fermentative production can be realized by submerged (SmF) or solid state fermentation (SSF). The yield and the composition of the obtained microbial lipids depend on the type of fermentation and the particular conditions (e.g., medium, pH-value, temperature, aeration, nitrogen source). From an economical point of view, waste or by-product streams can be used as cheap and renewable carbon and nitrogen sources. In general, downstream processing costs are one of the major obstacles to be solved for full economic efficiency of microbial lipids. For the extraction of lipids from microbial biomass cell disruption is most important, because efficiency of cell disruption directly influences subsequent downstream operations and overall extraction efficiencies. A multitude of cell disruption and lipid extraction methods are available, conventional as well as newly emerging methods, which will be described and discussed in terms of large scale applicability, their potential in a modern biorefinery and their influence on product quality. Furthermore, an overview is given about applications of microbial lipids or derived fatty

  4. Mating-defective ste mutations are suppressed by cell division cycle start mutations in Saccharomyces cerevisiae.

    PubMed Central

    Shuster, J R

    1982-01-01

    Temperature-sensitive mutants which arrest in the G1 phase of the cell cycle have been described for the yeast Saccharomyces cerevisiae. One class of these mutants (carrying cdc28, cdc36, cdc37, or cdc39) forms a shmoo morphology at restrictive temperature, characteristic of mating pheromone-arrested wild-type cells. Therefore, one hypothesis to explain the control of cell division by mating factors states that mating pheromones arrest wild-type cells by inactivating one or more of these CDC gene products. A class of mutants (carrying ste4, ste5, ste7, ste11, or ste12) which is insensitive to mating pheromone and sterile has also been described. One possible function of the STE gene products is the inactivation of the CDC gene products in the presence of a mating pheromone. A model incorporating these two hypotheses predicts that such STE gene products will not be required for mating in strains carrying an appropriate cdc lesion. This prediction was tested by assaying the mating abilities of double mutants for all of the pairwise combinations of cdc and ste mutations. Lesions in either cdc36 or cdc39 suppressed the mating defect due to ste4 and ste5. Allele specificity was observed in the suppression of both ste4 and ste5. The results indicate that the CDC36, CDC39, STE4, and STE5 gene products interact functionally or physically or both in the regulation of cell division mediated by the presence or absence of mating pheromones. The cdc36 and cdc39 mutations did not suppress ste7, ste11, or ste12. Lesions in cdc28 or cdc37 did not suppress any of the ste mutations. Other models of CDC and STE gene action which predicted that some of the cdc and ste mutations would be alleles of the same locus were tested. None of the cdc mutations was allelic to the ste mutations and, therefore, these models were eliminated. PMID:6757719

  5. Spatial colonization of microbial cells on the rhizoplane.

    NASA Astrophysics Data System (ADS)

    Raynaud, Xavier; Eickhorst, Thilo; Nunan, Naoise; Kaiser, Christina; Woebken, Dagmar; Schmidt, Hannes

    2017-04-01

    The rhizoplane is the region where the root surface is in contact with soil and corresponds to the inner limit of the rhizosphere. At the rhizoplane level, plants exchange elements with the surrounding soil and the rhizoplane can therefore be considered as the region that drives nutrient movement and transformation in the rhizosphere. The rhizoplane differs in many respects from the bulk soil due to the far larger supply of substrates derived from the roots, with far greater microbial cell densities and reduced levels of diversity (Philippot et al., 2013). This is likely to result in completely different interaction profiles among microorganisms which may affect rhizosphere biogeochemistry. While the diversity of microorganisms associated with the rhizosphere and on the rhizoplane is getting increasing attention, knowledge on the spatial organisation of this diversity is still scarce. We therefore aimed at investigating the spatial arrangement of microbial rhizoplane colonization to increase our understanding of potential interaction dynamics within soil-microbe-plant interfaces. To study the spatial distribution of microbial cells on roots we cultivated rice plants in water-logged paddy soil. Root samples were taken three months after germination. After removing adhering rhizosphere soil the root samples were chemically fixed and prepared for CARD-FISH (Schmidt & Eickhorst, 2014). For hybridization, the oligonucleotide probes EUB I-III (Daims et al., 1999) were applied to cover the majority of bacteria colonizing the rhizoplane. Root segments were then subjected to confocal laser scanning microscopy where triplicate image stacks of 10 µm thickness (0.5 µm layer distance) were acquired per region of interest (ROI). ROIs were defined as distances from the root tip (0, 5, 10, 15 mm) and corresponded to the root tip, elongation zone, and zone of maturation. Image stacks were processed using ImageJ software to extract microbial cells spatial coordinates, as well as

  6. Physiological and transcriptional responses of Saccharomyces cerevisiae to d-limonene show changes to the cell wall but not to the plasma membrane.

    PubMed

    Brennan, Timothy C R; Krömer, Jens O; Nielsen, Lars K

    2013-06-01

    Monoterpenes can, upon hydrogenation, be used as light-fraction components of sustainable aviation fuels. Fermentative production of monoterpenes in engineered microorganisms, such as Saccharomyces cerevisiae, has gained attention as a potential route to deliver these next-generation fuels from renewable biomass. However, end product toxicity presents a formidable problem for microbial synthesis. Due to their hydrophobicity, monoterpene inhibition has long been attributed to membrane interference, but the molecular mechanism remains largely unsolved. In order to gain a better understanding of the mode of action, we analyzed the composition and structural integrity of the cell envelope as well as the transcriptional response of yeast cells treated with an inhibitory amount of d-limonene (107 mg/liter). We found no alterations in membrane fluidity, structural membrane integrity, or fatty acid composition after the solvent challenge. A 4-fold increase in the mean fluorescence intensity per cell (using calcofluor white stain) and increased sensitivity to cell wall-degrading enzymes demonstrated that limonene disrupts cell wall properties. Global transcript measurements confirmed the membrane integrity observations by showing no upregulation of ergosterol or fatty acid biosynthesis pathways, which are commonly overexpressed in yeast to reinforce membrane rigidity during ethanol exposure. Limonene shock did cause a compensatory response to cell wall damage through overexpression of several genes (ROM1, RLM1, PIR3, CTT1, YGP1, MLP1, PST1, and CWP1) involved with the cell wall integrity signaling pathway. This is the first report demonstrating that cell wall, rather than plasma membrane, deterioration is the main source of monoterpene inhibition. We show that limonene can alter the structure and function of the cell wall, which has a clear effect on cytokinesis.

  7. Physiological and Transcriptional Responses of Saccharomyces cerevisiae to d-Limonene Show Changes to the Cell Wall but Not to the Plasma Membrane

    PubMed Central

    Brennan, Timothy C. R.; Nielsen, Lars K.

    2013-01-01

    Monoterpenes can, upon hydrogenation, be used as light-fraction components of sustainable aviation fuels. Fermentative production of monoterpenes in engineered microorganisms, such as Saccharomyces cerevisiae, has gained attention as a potential route to deliver these next-generation fuels from renewable biomass. However, end product toxicity presents a formidable problem for microbial synthesis. Due to their hydrophobicity, monoterpene inhibition has long been attributed to membrane interference, but the molecular mechanism remains largely unsolved. In order to gain a better understanding of the mode of action, we analyzed the composition and structural integrity of the cell envelope as well as the transcriptional response of yeast cells treated with an inhibitory amount of d-limonene (107 mg/liter). We found no alterations in membrane fluidity, structural membrane integrity, or fatty acid composition after the solvent challenge. A 4-fold increase in the mean fluorescence intensity per cell (using calcofluor white stain) and increased sensitivity to cell wall-degrading enzymes demonstrated that limonene disrupts cell wall properties. Global transcript measurements confirmed the membrane integrity observations by showing no upregulation of ergosterol or fatty acid biosynthesis pathways, which are commonly overexpressed in yeast to reinforce membrane rigidity during ethanol exposure. Limonene shock did cause a compensatory response to cell wall damage through overexpression of several genes (ROM1, RLM1, PIR3, CTT1, YGP1, MLP1, PST1, and CWP1) involved with the cell wall integrity signaling pathway. This is the first report demonstrating that cell wall, rather than plasma membrane, deterioration is the main source of monoterpene inhibition. We show that limonene can alter the structure and function of the cell wall, which has a clear effect on cytokinesis. PMID:23542628

  8. Single Cell Protein Production by Saccharomyces cerevisiae Using an Optimized Culture Medium Composition in a Batch Submerged Bioprocess.

    PubMed

    Hezarjaribi, Mehrnoosh; Ardestani, Fatemeh; Ghorbani, Hamid Reza

    2016-08-01

    Saccharomyces cerevisiae PTCC5269 growth was evaluated to specify an optimum culture medium to reach the highest protein production. Experiment design was conducted using a fraction of the full factorial methodology, and signal to noise ratio was used for results analysis. Maximum cell of 8.84 log (CFU/mL) was resulted using optimized culture composed of 0.3, 0.15, 1, and 50 g L(-1) of ammonium sulfate, iron sulfate, glycine, and glucose, respectively at 300 rpm and 35 °C. Glycine concentration (39.32 % contribution) and glucose concentration (36.15 % contribution) were determined as the most effective factors on the biomass production, while Saccharomyces cerevisiae growth had showed the least dependence on ammonium sulfate (5.2 % contribution) and iron sulfate (19.28 % contribution). The most interaction was diagnosed between ammonium sulfate and iron sulfate concentrations with interaction severity index of 50.71 %, while the less one recorded for glycine and glucose concentration was equal to 8.12 %. An acceptable consistency of 84.26 % was obtained between optimum theoretical cell numbers determined by software of 8.91 log (CFU/mL), and experimentally measured one at optimal condition confirms the suitability of the applied method. High protein content of 44.6 % using optimum culture suggests that Saccharomyces cerevisiae is a good commercial case for single cell protein production.

  9. Enhanced product formation in continuous fermentations with microbial cell recycle

    SciTech Connect

    Bull, D.N.; Young, M.D.

    1981-02-01

    The effect of partial recycle of microbial cells on the operation of a chemostat has been investigated for two fermentations. Stable steady states with and without partial cell recycle were obtained for the conversion of d-sorbitol to L-sorbose by Gluconobacter oxydans subsp. suboxydans 1916B and for the conversion of glucose to 2-ketogluconic acid by Serratia marcescens NRRl B-486. The employment of partial cell recycle dramatically increased product formation rates for both fermentations.

  10. Recent advances in microbial single cell genomics technology and applications

    NASA Astrophysics Data System (ADS)

    Stepanauskas, R.

    2015-12-01

    Single cell genomics is increasingly utilized as a powerful tool to decipher the metabolic potential, evolutionary histories and in situ interactions of environmental microorganisms. I will present several new developments of this exciting technology, which improve genomic data recovery from individual cells and allow its integration with cell's phenotypic properties. I will also demonstrate how these new technical capabilities help understanding the biology of the "microbial dark matter" inhabiting marine and terrestrial subsurface environments.

  11. Permeability of the cell envelope and osmotic behavior in Saccharomyces cerevisiae.

    PubMed

    Arnold, W N; Lacy, J S

    1977-08-01

    Bakers' yeast (Saccharomyces cerevisiae) was equilibrated with distilled water and then packed into standardized pellets by centrifugation. The fractional space (S value) that was accessible to passive permeation was probed with a variety of mono- and divalent salts, mono- and disaccharides, polyols, substrates and products of beta-fructofuranosidase (EC 3.2.1.26) and acid phosphatase (EC 3.1.3.2), and a cross-linked polymer of sucrose (Ficoll 400). A simple but very reproducible method was developed to measure pellet volume. At the limit of zero osmolality for bathing medium, the interstitial space was 0.223 ml/ml of pellet, and the aqueous volume of cell envelopes was 0.117 ml/ml of pellet. Thus the cell envelope for this yeast, under these conditions, was approximately 15% of the total cell volume. At a finite osmolality, the space in a yeast pellet that was accessible to salt was accounted for by the sum of initial interstitial space, the volume of the cell envelopes, and the volume of water abstracted from the cells by osmosis. Plots of S value versus osmolality were linear for uncharged probes and curvilinear for all salts. When Ficoll and potassium thiocyanate were presented to the yeast in admixture, the S values for the salt increased continuously over the range of osmolality studied. However, the S values for Ficoll 400 (which did not penetrate the cell wall) were lower by an amount equilivalent to the cell envelopes; they increased in parallel with the S curve for salt up to 1.15 osmol/kg and then plateaued. The results support the concept of incipient plasmolysis at 1.15 osmol/kg, and the separation of protoplasm from the cell wall is indicated with more concentrated solutions. Such cells were still viable if slowly diluted in distilled water, but they were injured by the shock of rapid dilution. However, shocking the cells did not release beta-fructofuranosidase into the medium. The complete accessibility of salts toward killed cells was demonstrated

  12. Studies concerning the temporal and genetic control of cell polarity in Saccharomyces cerevisiae

    PubMed Central

    1991-01-01

    The establishment of cell polarity was examined in the budding yeast, S. cerevisiae. The distribution of a polarized protein, the SPA2 protein, was followed throughout the yeast cell cycle using synchronized cells and cdc mutants. The SPA2 protein localizes to a patch at the presumptive bud site of G1 cells. Later it concentrates at the bud tip in budded cells. At cytokinesis, the SPA2 protein is at the neck between the mother and daughter cells. Analysis of unbudded haploid cells has suggested a series of events that occurs during G1. The SPA2 patch is established very early in G1, while the spindle pole body residues on the distal side of the nucleus. Later, microtubules emanating from the spindle pole body intersect the SPA2 crescent, and the nucleus probably rotates towards the SPA2 patch. By middle G1, most cells contain the SPB on the side of the nucleus proximal to the SPA2 patch, and a long extranuclear microtubule bundle intersects this patch. We suggest that a microtubule capture site exists in the SPA2 staining region that stabilizes the long microtubule bundle; this capture site may be responsible for rotation of the nucleus. Cells containing a polarized distribution of the SPA2 protein also possess a polarized distribution of actin spots in the same region, although the actin staining is much more diffuse. Moreover, cdc4 mutants, which form multiple buds at the restrictive temperature, exhibit simultaneous staining of the SPA2 protein and actin spots in a subset of the bud tips. spa2 mutants contain a polarized distribution of actin spots, and act1-1 and act1-2 mutants often contain a polarized distribution of the SPA2 protein suggesting that the SPA2 protein is not required for localization of the actin spots and the actin spots are not required for localization of the SPA2 protein. cdc24 mutants, which fail to form buds at the restrictive temperature, fail to exhibit polarized localization of the SPA2 protein and actin spots, indicating that the CDC

  13. Segregation of the Anodic Microbial Communities in a Microbial Fuel Cell Cascade.

    PubMed

    Hodgson, Douglas M; Smith, Ann; Dahale, Sonal; Stratford, James P; Li, Jia V; Grüning, André; Bushell, Michael E; Marchesi, Julian R; Avignone Rossa, C

    2016-01-01

    Metabolic interactions within microbial communities are essential for the efficient degradation of complex organic compounds, and underpin natural phenomena driven by microorganisms, such as the recycling of carbon-, nitrogen-, and sulfur-containing molecules. These metabolic interactions ultimately determine the function, activity and stability of the community, and therefore their understanding would be essential to steer processes where microbial communities are involved. This is exploited in the design of microbial fuel cells (MFCs), bioelectrochemical devices that convert the chemical energy present in substrates into electrical energy through the metabolic activity of microorganisms, either single species or communities. In this work, we analyzed the evolution of the microbial community structure in a cascade of MFCs inoculated with an anaerobic microbial community and continuously fed with a complex medium. The analysis of the composition of the anodic communities revealed the establishment of different communities in the anodes of the hydraulically connected MFCs, with a decrease in the abundance of fermentative taxa and a concurrent increase in respiratory taxa along the cascade. The analysis of the metabolites in the anodic suspension showed a metabolic shift between the first and last MFC, confirming the segregation of the anodic communities. Those results suggest a metabolic interaction mechanism between the predominant fermentative bacteria at the first stages of the cascade and the anaerobic respiratory electrogenic population in the latter stages, which is reflected in the observed increase in power output. We show that our experimental system represents an ideal platform for optimization of processes where the degradation of complex substrates is involved, as well as a potential tool for the study of metabolic interactions in complex microbial communities.

  14. Segregation of the Anodic Microbial Communities in a Microbial Fuel Cell Cascade

    PubMed Central

    Hodgson, Douglas M.; Smith, Ann; Dahale, Sonal; Stratford, James P.; Li, Jia V.; Grüning, André; Bushell, Michael E.; Marchesi, Julian R.; Avignone Rossa, C.

    2016-01-01

    Metabolic interactions within microbial communities are essential for the efficient degradation of complex organic compounds, and underpin natural phenomena driven by microorganisms, such as the recycling of carbon-, nitrogen-, and sulfur-containing molecules. These metabolic interactions ultimately determine the function, activity and stability of the community, and therefore their understanding would be essential to steer processes where microbial communities are involved. This is exploited in the design of microbial fuel cells (MFCs), bioelectrochemical devices that convert the chemical energy present in substrates into electrical energy through the metabolic activity of microorganisms, either single species or communities. In this work, we analyzed the evolution of the microbial community structure in a cascade of MFCs inoculated with an anaerobic microbial community and continuously fed with a complex medium. The analysis of the composition of the anodic communities revealed the establishment of different communities in the anodes of the hydraulically connected MFCs, with a decrease in the abundance of fermentative taxa and a concurrent increase in respiratory taxa along the cascade. The analysis of the metabolites in the anodic suspension showed a metabolic shift between the first and last MFC, confirming the segregation of the anodic communities. Those results suggest a metabolic interaction mechanism between the predominant fermentative bacteria at the first stages of the cascade and the anaerobic respiratory electrogenic population in the latter stages, which is reflected in the observed increase in power output. We show that our experimental system represents an ideal platform for optimization of processes where the degradation of complex substrates is involved, as well as a potential tool for the study of metabolic interactions in complex microbial communities. PMID:27242723

  15. [Detection of toxic substances in microbial fuel cells].

    PubMed

    Wang, Jiefu; Niu, Hao; Wu, Wenguo

    2017-05-25

    Microbial fuel cells (MFCs) is a highly promising bioelectrochemical technology and uses microorganisms as catalyst to convert chemical energy directly to electrical energy. Microorganisms in the anodic chamber of MFC oxidize the substrate and generate electrons. The electrons are absorbed by the anode and transported through an external circuit to the cathode for corresponding reduction. The flow of electrons is measured as current. This current is a linear measure of the activity of microorganisms. If a toxic event occurs, microbial activity will change, most likely decrease. Hence, fewer electrons are transported and current decreases as well. In this way, a microbial fuel cell-based biosensor provides a direct measure to detect toxicity for samples. This paper introduces the detection of antibiotics, heavy metals, organic pollutants and acid in MFCs. The existing problems and future application of MFCs are also analyzed.

  16. Defects in Protein Folding Machinery Affect Cell Wall Integrity and Reduce Ethanol Tolerance in S. cerevisiae.

    PubMed

    Narayanan, Aswathy; Pullepu, Dileep; Reddy, Praveen Kumar; Uddin, Wasim; Kabir, M Anaul

    2016-07-01

    The chaperonin complex CCT/TRiC (chaperonin containing TCP-1/TCP-1 ring complex) participates in the folding of many crucial proteins including actin and tubulin in eukaryotes. Mutations in genes encoding its subunits can affect protein folding and in turn, the physiology of the organism. Stress response in Saccharomyces cerevisiae is important in fermentation reactions and operates through overexpression and underexpression of genes, thus altering the protein profile. Defective protein folding machinery can disturb this process. In this study, the response of cct mutants to stress conditions in general and ethanol in specific was investigated. CCT1 mutants showed decreased resistance to different conditions tested including osmotic stress, metal ions, surfactants, reducing and oxidising agents. Cct1-3 mutant with the mutation in the conserved ATP-binding region showed irreversible defects than other mutants. These mutants were found to have inherent cell wall defects and showed decreased ethanol tolerance. This study reveals that cell wall defects and ethanol sensitivity are linked. Genetic and proteomic analyses showed that the yeast genes RPS6A (ribosomal protein), SCL1 (proteasomal subunit) and TDH3 (glyceraldehyde-3-phosphate dehydrogenase) on overexpression, improved the growth of cct1-3 mutant on ethanol. We propose the breakdown of common stress response pathways caused by mutations in CCT complex and the resulting scarcity of functional stress-responsive proteins, affecting the cell's defence against different stress agents in cct mutants. Defective cytoskeleton and perturbed cell wall integrity reduce the ethanol tolerance in the mutants which are rescued by the extragenic suppressors.

  17. Magnetic studies of ferrofluid-modified microbial cells.

    PubMed

    Mosiniewicz-Szablewska, Ewa; Safarikova, Mirka; Safarik, Ivo

    2010-04-01

    Microbial cells (Kluyveromyces fragilis and Chlorella vulgaris) efficiently interacted with maghemite nanoparticles stabilized as low-pH ionic magnetic fluid, leading to the formation of magnetically labeled cells. This simple procedure allows to use the prepared materials as new cheap and easy to get magnetic affinity adsorbents to the removal of water-soluble dyes from polluted water sources using magnetic separation techniques. Magnetically modified cells were investigated by means of electron spin resonance spectroscopy and conventional magnetic methods over the temperature range 4-300 K. The magnetic behavior of these materials was dominated by the superparamagnetic relaxation of isolated single domain maghemite particles although a little amount of agglomerates was also present on the cell surface. However, these agglomerates were sufficiently small to show at static conditions the superparamagnetic behavior at room temperature. Therefore, the ferrofluid-modified microbial cells represent new interesting magnetic affinity adsorbents which could be applied for large-scale magnetic separation processes.

  18. Improving flavor metabolism of Saccharomyces cerevisiae by mixed culture with Bacillus licheniformis for Chinese Maotai-flavor liquor making.

    PubMed

    Meng, Xing; Wu, Qun; Wang, Li; Wang, Diqiang; Chen, Liangqiang; Xu, Yan

    2015-12-01

    Microbial interactions could impact the metabolic behavior of microbes involved in food fermentation, and therefore they are important for improving food quality. This study investigated the effect of Bacillus licheniformis, the dominant bacteria in the fermentation process of Chinese Maotai-flavor liquor, on the metabolic activity of Saccharomyces cerevisiae. Results indicated that S. cerevisiae inhibited the growth of B. licheniformis in all mixed culture systems and final viable cell count was lower than 20 cfu/mL. Although growth of S. cerevisiae was barely influenced by B. licheniformis, its metabolism was changed as initial inoculation ratio varied. The maximum ethanol productions were observed in S. cerevisiae and B. licheniformis at 10(6):10(7) and 10(6):10(8) ratios and have increased by 16.8 % compared with single culture of S. cerevisiae. According to flavor compounds, the culture ratio 10(6):10(6) showed the highest level of total concentrations of all different kinds of flavor compounds. Correlation analyses showed that 12 flavor compounds, including 4 fatty acids and their 2 corresponding esters, 1 terpene, and 5 aromatic compounds, that could only be produced by S. cerevisiae were significantly correlated with the initial inoculation amount of B. licheniformis. These metabolic changes in S. cerevisiae were not only a benefit for liquor aroma, but may also be related to its inhibition effect in mixed culture. This study could help to reveal the microbial interactions in Chinese liquor fermentation and provide guidance for optimal arrangement of mixed culture fermentation systems.

  19. Bioaccumulation of the Selected Metal Ions in Saccharomyces cerevisiae Cells Under Treatment of the Culture with Pulsed Electric Field (PEF).

    PubMed

    Pankiewicz, Urszula; Sujka, Monika; Jamroz, Jerzy

    2015-12-01

    The obtained results demonstrated an influence of PEF on increase in accumulation of various ions in S. cerevisiae cells. Optimization of particular PEF parameters and ions concentrations in the medium caused twofold increase in accumulation of magnesium and zinc ions and 3.5-fold higher accumulation of calcium ions in the cells. In the case of ion couple, accumulation of magnesium and zinc was, respectively, 1.5-fold and twofold higher in comparison to the control cultures. Yeast cells biomass enriched with Mg(2+), Zn(2+), Ca(2+) as well as Mg(2+) and Zn(2+) (simultaneously) may be an alternative for pharmacological supplementation applied in deficiency of these cations.

  20. The first self-sustainable microbial fuel cell stack.

    PubMed

    Ledezma, Pablo; Stinchcombe, Andrew; Greenman, John; Ieropoulos, Ioannis

    2013-02-21

    This study reports for the first time on the development of a self-sustainable microbial fuel cell stack capable of self-maintenance (feeding, hydration, sensing & reporting). Furthermore, the stack system is producing excess energy, which can be used for improved functionality. The self-maintenance is performed by the stack powering single and multi-channel peristaltic pumps.

  1. Microbial Fuel Cell Performance with a Pressurized Cathode Chamber

    USDA-ARS?s Scientific Manuscript database

    Microbial fuel cell (MFC) power densities are often constrained by the oxygen reduction reaction rate on the cathode electrode. One important factor for this is the normally low solubility of oxygen in the aqueous cathode solution creating mass transport limitations, which hinder oxygen reduction a...

  2. The Microbial Fuel Cell as an Education Tool

    ERIC Educational Resources Information Center

    Dewan, Alim; Van Wie, Bernard; Beyenal, Haluk; Lewandowski, Zbigniew

    2010-01-01

    Many chemical engineering programs offer courses from a variety of disciplines to teach their students multidisciplinary concepts, but often these courses lack appropriate tools for linking newly learned concepts to principles learned in the core courses. This paper describes our experience of incorporating a microbial fuel cell education module…

  3. Oxygen - Enemy or Friend for Microbial Fuel Cell Anode Performance?

    USDA-ARS?s Scientific Manuscript database

    Until recently, scientists and engineers have held a strong belief that oxygen intrusion into the anode chamber of a bioelectrochemical system (BES) is detrimental to microbial fuel cell (MFC) performance because oxygen acts as an alternate electron acceptor. This would, according to recent beliefs...

  4. The Microbial Fuel Cell as an Education Tool

    ERIC Educational Resources Information Center

    Dewan, Alim; Van Wie, Bernard; Beyenal, Haluk; Lewandowski, Zbigniew

    2010-01-01

    Many chemical engineering programs offer courses from a variety of disciplines to teach their students multidisciplinary concepts, but often these courses lack appropriate tools for linking newly learned concepts to principles learned in the core courses. This paper describes our experience of incorporating a microbial fuel cell education module…

  5. Cytochrome c Release and Mitochondria Involvement in Programmed Cell Death Induced by Acetic Acid in Saccharomyces cerevisiae

    PubMed Central

    Ludovico, Paula; Rodrigues, Fernando; Almeida, Agostinho; Silva, Manuel T.; Barrientos, Antoni; Côrte-Real, Manuela

    2002-01-01

    Evidence is presented that mitochondria are implicated in the previously described programmed cell death (PCD) process induced by acetic acid in Saccharomyces cerevisiae. In yeast cells undergoing a PCD process induced by acetic acid, translocation of cytochrome c (CytC) to the cytosol and reactive oxygen species production, two events known to be proapoptotic in mammals, were observed. Associated with these events, reduction in oxygen consumption and in mitochondrial membrane potential was found. Enzymatic assays showed that the activity of complex bc1 was normal, whereas that of cytochrome c oxidase (COX) was strongly decreased. This decrease is in accordance with the observed reduction in the amounts of COX II subunit and of cytochromes a+a3. The acetic acid-induced PCD process was found to be independent of oxidative phosphorylation because it was not inhibited by oligomycin treatment. The inability of S. cerevisiae mutant strains (lacking mitochondrial DNA, heme lyase, or ATPase) to undergo acetic acid-induced PCD and in the ATPase mutant (knockout in ATP10) the absence of CytC release provides further evidence that the process is mediated by a mitochondria-dependent apoptotic pathway. The understanding of the involvement of a mitochondria-dependent apoptotic pathway in S. cerevisiae PCD process will be most useful in the further elucidation of an ancestral pathway common to PCD in metazoans. PMID:12181332

  6. Evaluation of industrial Saccharomyces cerevisiae strains as the chassis cell for second-generation bioethanol production

    PubMed Central

    Li, Hongxing; Wu, Meiling; Xu, Lili; Hou, Jin; Guo, Ting; Bao, Xiaoming; Shen, Yu

    2015-01-01

    To develop a suitable Saccharomyces cerevisiae industrial strain as a chassis cell for ethanol production using lignocellulosic materials, 32 wild-type strains were evaluated for their glucose fermenting ability, their tolerance to the stresses they might encounter in lignocellulosic hydrolysate fermentation and their genetic background for pentose metabolism. The strain BSIF, isolated from tropical fruit in Thailand, was selected out of the distinctly different strains studied for its promising characteristics. The maximal specific growth rate of BSIF was as high as 0.65 h−1 in yeast extract peptone dextrose medium, and the ethanol yield was 0.45 g g−1 consumed glucose. Furthermore, compared with other strains, this strain exhibited superior tolerance to high temperature, hyperosmotic stress and oxidative stress; better growth performance in lignocellulosic hydrolysate; and better xylose utilization capacity when an initial xylose metabolic pathway was introduced. All of these results indicate that this strain is an excellent chassis strain for lignocellulosic ethanol production. PMID:25616171

  7. A study of the phosphate linkages in phosphomannan in cell walls of Saccharomyces cerevisiae

    PubMed Central

    Cawley, T. N.; Harrington, M. G.; Letters, R.

    1972-01-01

    1. The phosphomannan of Saccharomyces cerevisiae was released by Pronase digestion of cell walls and isolated by chromatography on DEAE-cellulose or by precipitation with borate–Cetavlon solutions. Mannose and phosphorus were present in the molar ratio 18:1 and the phosphate groups were in the diester form. 2. Hydrolysis with acid gave mannose 6-phosphate. Under mild acid conditions (autohydrolysis) the phosphate groups were converted into the monoester form, mannose was released and the molecular size of the phosphomannan was substantially decreased. 3. Hydrolysis with alkali also gave a monoester phosphate and a similar decrease in molecular weight. Under mild alkaline conditions the serine and threonine content of the phosphomannan was decreased by about 80%. The phosphate content was not altered. 4. Treatment with 40% (v/v) HF removed 70% of the phosphorus from the phosphomannan with no detectable decrease in molecular weight. 5. Periodate oxidation gave an oxophosphomannan from which 80% of the phosphorus was eliminated under mild alkaline conditions. 6. The properties of the phosphomannan are consistent with a structure in which the phosphate groups are located on the outside of the molecule and link C-1 of a terminal mannose unit with C-6 of another mannose unit, which is in turn attached to the polysaccharide backbone of the molecule. 7. The implications of this structure are discussed in relation to flocculation. PMID:4349116

  8. Microbial community dynamics in continuous microbial fuel cells fed with synthetic wastewater and pig slurry.

    PubMed

    Sotres, Ana; Tey, Laura; Bonmatí, August; Viñas, Marc

    2016-10-01

    Two-chambered microbial fuel cells (MFCs) operating with synthetic wastewater and pig slurry were assessed. Additionally, the use of 2-bromoethanesulfonate (BES-Inh) was studied. The synthetic wastewater-fed MFC (MFCSW) showed a maximum power density (PDmax) of 2138mWm(-3), and the addition of BES-Inh (10mM) did not show any improvement in its performance (PDmax=2078mWm(-3)). When pig slurry was used as feed (MFCPS), PDmax increased up to 5623mWm(-3). The microbial community composition was affected by the type of substrate used. While, Pseudomonadaceae and Clostridiaceae were the most representative families within the acetate-based medium, Flavobacteriaceae, Chitinophagaceae, Comamonadaceae and Nitrosomonadaceae were predominant when pig slurry was used as feed. Otherwise, only the Eubacterial microbial community composition was strongly modified when adding BES-Inh, thus leading to an enrichment of the Bacteroidetes phylum. Oppositely, the Archaeal community was less affected by the addition of BES-Inh, and Methanosarcina sp., arose as the predominant family in both situations. Despite all the differences in microbial communities, 6 operational taxonomic units (OTUs) belonging to Bacteroidetes (Porphyromonadaceae and Marinilabiaceae) and Firmicutes (Clostridiales) were found to be common to both MFCs, also for different contents of COD and N-NH4(+), and therefore could be considered as the bioanode core microbiome.

  9. High shear enrichment improves the performance of the anodophilic microbial consortium in a microbial fuel cell

    PubMed Central

    Pham, Hai The; Boon, Nico; Aelterman, Peter; Clauwaert, Peter; De Schamphelaire, Liesje; Van Oostveldt, Patrick; Verbeken, Kim; Rabaey, Korneel; Verstraete, Willy

    2008-01-01

    Summary In many microbial bioreactors, high shear rates result in strong attachment of microbes and dense biofilms. In this study, high shear rates were applied to enrich an anodophilic microbial consortium in a microbial fuel cell (MFC). Enrichment at a shear rate of about 120 s−1 resulted in the production of a current and power output two to three times higher than those in the case of low shear rates (around 0.3 s−1). Biomass and biofilm analyses showed that the anodic biofilm from the MFC enriched under high shear rate conditions, in comparison with that under low shear rate conditions, had a doubled average thickness and the biomass density increased with a factor 5. The microbial community of the former, as analysed by DGGE, was significantly different from that of the latter. The results showed that enrichment by applying high shear rates in an MFC can result in a specific electrochemically active biofilm that is thicker and denser and attaches better, and hence has a better performance. PMID:21261869

  10. Electricity production and microbial biofilm characterization in cellulose-fed microbial fuel cells.

    PubMed

    Ren, Z; Steinberg, L M; Regan, J M

    2008-01-01

    Converting biodegradable materials into electricity, microbial fuel cells (MFCs) present a promising technology for renewable energy production in specific applications. Unlike typical soluble substrates that have been used as electron donors in MFC studies, cellulose is unique because it requires a microbial consortium that can metabolize both an insoluble electron donor (cellulose) and electron acceptor (electrode). In this study, electricity generation and the microbial ecology of cellulose-fed MFCs were analyzed using a defined co-culture of Clostridium cellulolyticum and Geobacter sulfurreducens. Fluorescent in situ hybridization and quantitative PCR showed that when particulate MN301 cellulose was used as sole substrate, most Clostridium cells were found adhered to cellulose particles in suspension, while most Geobacter cells were attached to the electrode. By comparison, both bacteria resided in suspension and biofilm samples when soluble carboxymethyl cellulose was used. This distinct function-related distribution of the bacteria suggests an opportunity to optimize reactor operation by settling cellulose and decanting supernatant to extend cellulose hydrolysis and improve cellulose-electricity conversion. (c) IWA Publishing 2008.

  11. Misregulation of Scm3p/HJURP causes chromosome instability in Saccharomyces cerevisiae and human cells.

    PubMed

    Mishra, Prashant K; Au, Wei-Chun; Choy, John S; Kuich, P Henning; Baker, Richard E; Foltz, Daniel R; Basrai, Munira A

    2011-09-01

    The kinetochore (centromeric DNA and associated proteins) is a key determinant for high fidelity chromosome transmission. Evolutionarily conserved Scm3p is an essential component of centromeric chromatin and is required for assembly and function of kinetochores in humans, fission yeast, and budding yeast. Overexpression of HJURP, the mammalian homolog of budding yeast Scm3p, has been observed in lung and breast cancers and is associated with poor prognosis; however, the physiological relevance of these observations is not well understood. We overexpressed SCM3 and HJURP in Saccharomyces cerevisiae and HJURP in human cells and defined domains within Scm3p that mediate its chromosome loss phenotype. Our results showed that the overexpression of SCM3 (GALSCM3) or HJURP (GALHJURP) caused chromosome loss in a wild-type yeast strain, and overexpression of HJURP led to mitotic defects in human cells. GALSCM3 resulted in reduced viability in kinetochore mutants, premature separation of sister chromatids, and reduction in Cse4p and histone H4 at centromeres. Overexpression of CSE4 or histone H4 suppressed chromosome loss and restored levels of Cse4p at centromeres in GALSCM3 strains. Using mutant alleles of scm3, we identified a domain in the N-terminus of Scm3p that mediates its interaction with CEN DNA and determined that the chromosome loss phenotype of GALSCM3 is due to centromeric association of Scm3p devoid of Cse4p/H4. Furthermore, we determined that similar to other systems the centromeric association of Scm3p is cell cycle regulated. Our results show that altered stoichiometry of Scm3p/HJURP, Cse4p, and histone H4 lead to defects in chromosome segregation. We conclude that stringent regulation of HJURP and SCM3 expression are critical for genome stability.

  12. An Endomitotic Effect of a Cell Cycle Mutation of SACCHAROMYCES CEREVISIAE

    PubMed Central

    Schild, David; Ananthaswamy, Honnavara N.; Mortimer, Robert K.

    1981-01-01

    A recessive temperature-sensitive mutation of Saccharomyces cerevisiae has been isolated and shown to cause an increase in ploidy in both haploids and diploids. Genetic analysis revealed that the strain carrying the mutation was an aa diploid, although MNNG mutagenesis had been done on an a haploid strain. When the mutant strain was crossed with an αα diploid and the resultant tetraploid sporulated, some of the meiotic progeny of this tetraploid were themselves tetraploid, as shown by both genetic analysis and DNA measurements, instead of diploid as expected of tetraploid meiosis. The ability of these tetraploids to continue to produce tetraploid meiotic progeny was followed for four generations. Homothallism was excluded as a cause of the increase in ploidy; visual pedigree analysis of spore clones to about the 32-cell stage failed to reveal any zygotes, and haploids that diploidized retained their mating type. An extra round of meiotic DNA synthesis was also considered and excluded. It was found that tetraploidization was independent of sporulation temperature, but was dependent on the temperature of germination and the growth of the spores. Increase in ploidy occurred when the spores were germinated and grown at 30°, but did not occur at 23°. Two cycles of sporulation and growth at 23° resulted in haploids, which were shown to diploidize within 24 hr when grown at 30°. Visual observation of the haploid cells incubated at 36° revealed a cell-division-cycle phenotype characteristic of mutations that affect nuclear division; complementation analysis demonstrated that the mutation, cdc31–2, is allelic to cdc31–1, a mutation isolated by Hartwell et al. (1973) and characterized as causing a temperature-sensitive arrest during late nuclear division. The segregation of cdc31–2 in heterozygous diploids was 2:2 and characteristic of a noncentromere-linked gene. PMID:7028565

  13. Role of glutathione metabolism status in the definition of some cellular parameters and oxidative stress tolerance of Saccharomyces cerevisiae cells growing as biofilms.

    PubMed

    Gales, Grégoire; Penninckx, Michel; Block, Jean-Claude; Leroy, Pierre

    2008-08-01

    The resistance of Saccharomyces cerevisiae to oxidative stress (H(2)O(2) and Cd(2+)) was compared in biofilms and planktonic cells, with the help of yeast mutants deleted of genes related to glutathione metabolism and oxidative stress. Biofilm-forming cells were found predominantly in the G1 stage of the cell cycle. This might explain their higher tolerance to oxidative stress and the young replicative age of these cells in an old culture. The reduced glutathione status of S. cerevisiae was affected by the growth phase and apparently plays an important role in oxidative stress tolerance in cells growing as a biofilm.

  14. Microbial fuel cell treatment of fuel process wastewater

    DOEpatents

    Borole, Abhijeet P; Tsouris, Constantino

    2013-12-03

    The present invention is directed to a method for cleansing fuel processing effluent containing carbonaceous compounds and inorganic salts, the method comprising contacting the fuel processing effluent with an anode of a microbial fuel ell, the anode containing microbes thereon which oxidatively degrade one or more of the carbonaceous compounds while producing electrical energy from the oxidative degradation, and directing the produced electrical energy to drive an electrosorption mechanism that operates to reduce the concentration of one or more inorganic salts in the fuel processing effluent, wherein the anode is in electrical communication with a cathode of the microbial fuel cell. The invention is also directed to an apparatus for practicing the method.

  15. The Transient Inactivation of the Master Cell Cycle Phosphatase Cdc14 Causes Genomic Instability in Diploid Cells of Saccharomyces cerevisiae.

    PubMed

    Quevedo, Oliver; Ramos-Pérez, Cristina; Petes, Thomas D; Machín, Félix

    2015-07-01

    Genomic instability is a common feature found in cancer cells . Accordingly, many tumor suppressor genes identified in familiar cancer syndromes are involved in the maintenance of the stability of the genome during every cell division and are commonly referred to as caretakers. Inactivating mutations and epigenetic silencing of caretakers are thought to be the most important mechanisms that explain cancer-related genome instability. However, little is known of whether transient inactivation of caretaker proteins could trigger genome instability and, if so, what types of instability would occur. In this work, we show that a brief and reversible inactivation, during just one cell cycle, of the key phosphatase Cdc14 in the model organism Saccharomyces cerevisiae is enough to result in diploid cells with multiple gross chromosomal rearrangements and changes in ploidy. Interestingly, we observed that such transient loss yields a characteristic fingerprint whereby trisomies are often found in small-sized chromosomes, and gross chromosome rearrangements, often associated with concomitant loss of heterozygosity, are detected mainly on the ribosomal DNA-bearing chromosome XII. Taking into account the key role of Cdc14 in preventing anaphase bridges, resetting replication origins, and controlling spindle dynamics in a well-defined window within anaphase, we speculate that the transient loss of Cdc14 activity causes cells to go through a single mitotic catastrophe with irreversible consequences for the genome stability of the progeny.

  16. The Transient Inactivation of the Master Cell Cycle Phosphatase Cdc14 Causes Genomic Instability in Diploid Cells of Saccharomyces cerevisiae

    PubMed Central

    Quevedo, Oliver; Ramos-Pérez, Cristina; Petes, Thomas D.; Machín, Félix

    2015-01-01

    Genomic instability is a common feature found in cancer cells . Accordingly, many tumor suppressor genes identified in familiar cancer syndromes are involved in the maintenance of the stability of the genome during every cell division and are commonly referred to as caretakers. Inactivating mutations and epigenetic silencing of caretakers are thought to be the most important mechanisms that explain cancer-related genome instability. However, little is known of whether transient inactivation of caretaker proteins could trigger genome instability and, if so, what types of instability would occur. In this work, we show that a brief and reversible inactivation, during just one cell cycle, of the key phosphatase Cdc14 in the model organism Saccharomyces cerevisiae is enough to result in diploid cells with multiple gross chromosomal rearrangements and changes in ploidy. Interestingly, we observed that such transient loss yields a characteristic fingerprint whereby trisomies are often found in small-sized chromosomes, and gross chromosome rearrangements, often associated with concomitant loss of heterozygosity, are detected mainly on the ribosomal DNA-bearing chromosome XII. Taking into account the key role of Cdc14 in preventing anaphase bridges, resetting replication origins, and controlling spindle dynamics in a well-defined window within anaphase, we speculate that the transient loss of Cdc14 activity causes cells to go through a single mitotic catastrophe with irreversible consequences for the genome stability of the progeny. PMID:25971663

  17. Coastal microbial fuel cell: scaling laws and systems

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, Promode R.; McNeilly, Frank J.; Thivierge, Daniel P.; Fredette, Albert R.

    2006-05-01

    Microbes, like Geobacters, have inhabited the seafloors around the world since the early days of earth. Such regions are anaerobic and they gain energy by using the widely prevalent iron oxides and organic matters. Because they appear to colonize conducting surfaces that act as sinks of electrons, microbial fuel cells have been shown to convert organic matter to electricity. A microbial fuel cell system has been deployed in Narragansett Bay in Newport, Rhode Island for a year. Currently, the cathode and anode areas are of the order of that of a small wind mill. Measurements have been carried out to determine the marine scaling laws of power harvesting in passive benthic microbial fuel cells. The focus has been on the ocean engineering aspects such as marine scaling laws and the integration of the biochemical and the electronic systems. The characteristics examined are: the relationship of electrode surface area and power produced, the stabilization rates of ionic paths, that is, the effects of location depth of cathodes on stabilization after deployment, the effects of solar and lunar cycles in the Narragansett Bay on the dynamic components of power produced, and the hysteresis effects between periods of active power harvesting and dormancy; the effects of 'on sediment surface' versus 'in sediment' anode deployment have been examined for smaller electrode areas so far. A capacitance model of power consumption and harvesting has been proposed for the marine environment. It is assumed that the primordial benthic microbe laden layer of the earth acts like a giant capacitor. In the microbial fuel cell, this charged benthic layer acts in series with a smaller constant voltage DC power source. This giant benthic capacitance is a result of untapped accumulated charge from the microbes while the DC source originates from the real-time production due to the microbes. Finally, the microbial fuel cell is integrated with a power conversion system to intermittently energize a

  18. Relation between cell death progression, reactive oxygen species production and mitochondrial membrane potential in fermenting Saccharomyces cerevisiae cells under heat-shock conditions.

    PubMed

    Pyatrikas, Darya V; Fedoseeva, Irina V; Varakina, Nina N; Rusaleva, Tatyana M; Stepanov, Alexei V; Fedyaeva, Anna V; Borovskii, Gennadii B; Rikhvanov, Eugene G

    2015-06-01

    Moderate heat shock increased reactive oxygen species (ROS) production that led to cell death in glucose-grown Saccharomyces cerevisiae cells. Conditions that disturb mitochondrial functions such as treatment by uncouplers and petite mutation were shown to inhibit ROS production and protects cell from thermal death. Hence, mitochondria are responsible for ROS production and play an active role in cell death. An increase in ROS production was accompanied by hyperpolarization of inner mitochondrial membrane. All agents suppressing hyperpolarization also suppressed heat-induced ROS production. It was supposed that generation of ROS under moderate heat shock in glucose-grown S. cerevisiae cells is driven by the mitochondrial membrane potential. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  19. Significant quantities of the glycolytic enzyme phosphoglycerate mutase are present in the cell wall of yeast Saccharomyces cerevisiae.

    PubMed Central

    Motshwene, Precious; Brandt, Wolf; Lindsey, George

    2003-01-01

    NaOH was used to extract proteins from the cell walls of the yeast Saccharomyces cerevisiae. This treatment was shown not to disrupt yeast cells, as NaOH-extracted cells displayed a normal morphology upon electron microscopy. Moreover, extracted and untreated cells had qualitatively similar protein contents upon disruption. When yeast was grown in the presence of 1 M mannitol, two proteins were found to be present at an elevated concentration in the cell wall. These were found to be the late-embryogenic-abundant-like protein heat-shock protein 12 and the glycolytic enzyme phosphoglycerate mutase. The presence of phosphoglycerate mutase in the cell wall was confirmed by immunocytochemical analysis. Not only was the phosphoglycerate mutase in the yeast cell wall found to be active, but whole yeast cells were also able to convert 3-phosphoglycerate in the medium into ethanol, provided that the necessary cofactors were present. PMID:12238949

  20. [Microbial fuel cells as an alternative power supply].

    PubMed

    Il'in, V K; Smirnov, I A; Soldatov, P É; Korshunov, D V; Tiurin-Kuz'min, A Iu; Starkova, L V; Chumakov, P E; Emel'ianova, L K; Novikova, L M; Debabov, V G; Voeĭkova, T A

    2012-01-01

    Purpose of the work was designing and prototyping of microbial fuel cells (MFC) and comparative evaluation of the electrogenic activity of wastewater autochthonous microorganisms as well as bacterial monocultures. Objects were model electrogenic strain Shewanella oneidensis MR-1, and an Ochrobactrum sp. strain isolated from the active anode biofilm of MFC composed as an electricity generating system. The study employed the methods typically used for aerobic and anaerobic strains, current measurement, identification of new electrogenic strains in microbial association of wastewater sludge and species definition by rRNA 16-S. As a result, two MFCs prototypes were tried out. Besides, it was shown that electrogenic activity of S. oneidensis MR-1 and Ochrobactrum sp. monocultures is similar but differs from that of the microbial association of the anode biofilm.

  1. Identifying the microbial communities and operational conditions for optimized wastewater treatment in microbial fuel cells.

    PubMed

    Ishii, Shun'ichi; Suzuki, Shino; Norden-Krichmar, Trina M; Wu, Angela; Yamanaka, Yuko; Nealson, Kenneth H; Bretschger, Orianna

    2013-12-01

    Microbial fuel cells (MFCs) are devices that exploit microorganisms as "biocatalysts" to recover energy from organic matter in the form of electricity. MFCs have been explored as possible energy neutral wastewater treatment systems; however, fundamental knowledge is still required about how MFC-associated microbial communities are affected by different operational conditions and can be optimized for accelerated wastewater treatment rates. In this study, we explored how electricity-generating microbial biofilms were established at MFC anodes and responded to three different operational conditions during wastewater treatment: 1) MFC operation using a 750 Ω external resistor (0.3 mA current production); 2) set-potential (SP) operation with the anode electrode potentiostatically controlled to +100 mV vs SHE (4.0 mA current production); and 3) open circuit (OC) operation (zero current generation). For all reactors, primary clarifier effluent collected from a municipal wastewater plant was used as the sole carbon and microbial source. Batch operation demonstrated nearly complete organic matter consumption after a residence time of 8-12 days for the MFC condition, 4-6 days for the SP condition, and 15-20 days for the OC condition. These results indicate that higher current generation accelerates organic matter degradation during MFC wastewater treatment. The microbial community analysis was conducted for the three reactors using 16S rRNA gene sequencing. Although the inoculated wastewater was dominated by members of Epsilonproteobacteria, Gammaproteobacteria, and Bacteroidetes species, the electricity-generating biofilms in MFC and SP reactors were dominated by Deltaproteobacteria and Bacteroidetes. Within Deltaproteobacteria, phylotypes classified to family Desulfobulbaceae and Geobacteraceae increased significantly under the SP condition with higher current generation; however those phylotypes were not found in the OC reactor. These analyses suggest that species

  2. Programmed Cell Death and Complexity in Microbial Systems.

    PubMed

    Durand, Pierre M; Sym, Stuart; Michod, Richard E

    2016-07-11

    Programmed cell death (PCD) is central to organism development and for a long time was considered a hallmark of multicellularity. Its discovery, therefore, in unicellular organisms presents compelling questions. Why did PCD evolve? What is its ecological effect on communities? To answer these questions, one is compelled to consider the impacts of PCD beyond the cell, for death obviously lowers the fitness of the cell. Here, we examine the ecological effects of PCD in different microbial scenarios and conclude that PCD can increase biological complexity. In mixed microbial communities, the mode of death affects the microenvironment, impacting the interactions between taxa. Where the population comprises groups of relatives, death has a more explicit effect. Death by lysis or other means can be harmful, while PCD can evolve by providing advantages to relatives. The synchronization of death between individuals suggests a group level property is being maintained and the mode of death also appears to have had an impact during the origin of multicellularity. PCD can result in the export of fitness from the cell to the group level via re-usable resources and PCD may also provide a mechanism for how groups beget new groups comprising kin. Furthermore, PCD is a means for solving a central problem of group living - the toxic effects of death - by making resources in dying cells beneficial to others. What emerges from the data reviewed here is that while PCD carries an obvious cost to the cell, it can be a driver of complexity in microbial communities.

  3. Annurca apple (M. pumila Miller cv Annurca) extracts act against stress and ageing in S. cerevisiae yeast cells.

    PubMed

    Stirpe, Mariarita; Palermo, Vanessa; Bianchi, Michele Maria; Silvestri, Romano; Falcone, Claudio; Tenore, Giancarlo; Novellino, Ettore; Mazzoni, Cristina

    2017-04-05

    During the past years, a number of studies have demonstrated the positive effect of apple on ageing and different diseases such as cancer, degenerative and cardiovascular diseases. The unicellular yeast Saccharomyces cerevisiae represents a simple eukaryotic model to study the effects of different compounds on lifespan. We previously demonstrated that apple extracts have anti-ageing effects in this organism because of their antioxidant properties. In particular, the effect is related to the presence in this fruit of polyphenols, which give a large contribution to the antioxidant activity of apples. We we used a clonogenic assay to assess the viability and the resistance to oxidative stress of S. cerevisiae cells in the presence of Annurca apple extracts. The production of ROS and the aberrant morphology of nuclei were detected by cell staining with the fluorescent dies Dihydrorhodamine 123 and DAPI, respectively. Mitochondrial morphology was analyzed by following the localization of the mito-GFP protein into the mitochondrial matrix. In this study, we show that apple extracts can increase yeast lifespan, reduce the levels of reactive oxygen species and cell sensitivity to oxidative stress, and prevent nuclei and mitochondria fragmentation protecting cells from regulated cell death. In this paper, by using the yeast S. cerevisiae as a model, we have demonstrated that Annurca extracts possess antioxidant properties thanks to which the extracts can reduce the intracellular ROS levels and have anti-apoptotic functions thus prolonging cell lifespan. These results contribute to knowledge on the effects of natural compounds on ageing and support the use of yeast as a model organism for the development of simple tests to assess the effectiveness of bioactive substances from natural sources.

  4. Bioethanol production from mixed sugars by Scheffersomyces stipitis free and immobilized cells, and co-cultures with Saccharomyces cerevisiae.

    PubMed

    De Bari, Isabella; De Canio, Paola; Cuna, Daniela; Liuzzi, Federico; Capece, Angela; Romano, Patrizia

    2013-09-25

    Bioethanol can be produced from several biomasses including lignocellulosic materials. Besides 6-carbon sugars that represent the prevalent carbohydrates, some of these feedstocks contain significant amounts of 5-carbon sugars. One common limit of the major part of the xylose-fermenting yeasts is the diauxic shift between the uptake of glucose and xylose during the fermentation of mixed syrups. Thus, optimized fermentation strategies are required. In this paper the ability of Scheffersomyces stipitis strain NRRLY-11544 to ferment mixed syrups with a total sugar concentration in the range 40-80 g/L was investigated by using mono cultures, co-cultures with Saccharomyces cerevisiae strain Bakers Yeast Type II and single cultures immobilized in silica-hydrogel films. The experimental design for the fermentations with immobilized cells included the process analysis in function of two parameters: the fraction of the gel in the broth and the concentration of the cells loaded in the gel. Furthermore, for each total sugars level, the fermentative course of S. stipitis was analyzed at several glucose-to xylose ratios. The results indicated that the use of S. stipitis and S. cerevisiae in free co-cultures ensured faster processes than single cultures of S. stipitis either free or immobilized. However, the rapid production of ethanol by S. cerevisiae inhibited S. stipitis and caused a stuck of the process. Immobilization of S. stipitis in silica-hydrogel increased the relative consumption rate of xylose-to-glucose by 2-6 times depending on the composition of the fermentation medium. Furthermore the films performances appeared stable over three weeks of continuous operations. However, on the whole, the final process yields obtained with the immobilized cells were not meaningfully different from that of the free cells. This was probably due to concurrent fermentations operated by the cells released in the broth. Optimization of the carrier characteristics could improve the

  5. Proximity Effect among Cellulose-Degrading Enzymes Displayed on the Saccharomyces cerevisiae Cell Surface

    PubMed Central

    Bae, Jungu; Kuroda, Kouichi

    2014-01-01

    Proximity effect is a form of synergistic effect exhibited when cellulases work within a short distance from each other, and this effect can be a key factor in enhancing saccharification efficiency. In this study, we evaluated the proximity effect between 3 cellulose-degrading enzymes displayed on the Saccharomyces cerevisiae cell surface, that is, endoglucanase, cellobiohydrolase, and β-glucosidase. We constructed 2 kinds of arming yeasts through genome integration: ALL-yeast, which simultaneously displayed the 3 cellulases (thus, the different cellulases were near each other), and MIX-yeast, a mixture of 3 kinds of single-cellulase-displaying yeasts (the cellulases were far apart). The cellulases were tagged with a fluorescence protein or polypeptide to visualize and quantify their display. To evaluate the proximity effect, we compared the activities of ALL-yeast and MIX-yeast with respect to degrading phosphoric acid-swollen cellulose after adjusting for the cellulase amounts. ALL-yeast exhibited 1.25-fold or 2.22-fold higher activity than MIX-yeast did at a yeast concentration equal to the yeast cell number in 1 ml of yeast suspension with an optical density (OD) at 600 nm of 10 (OD10) or OD0.1. At OD0.1, the distance between the 3 cellulases was greater than that at OD10 in MIX-yeast, but the distance remained the same in ALL-yeast; thus, the difference between the cellulose-degrading activities of ALL-yeast and MIX-yeast increased (to 2.22-fold) at OD0.1, which strongly supports the proximity effect between the displayed cellulases. A proximity effect was also observed for crystalline cellulose (Avicel). We expect the proximity effect to further increase when enzyme display efficiency is enhanced, which would further increase cellulose-degrading activity. This arming yeast technology can also be applied to examine proximity effects in other diverse fields. PMID:25304511

  6. Tomato QM-like protein protects Saccharomyces cerevisiae cells against oxidative stress by regulating intracellular proline levels.

    PubMed

    Chen, Changbin; Wanduragala, Srimevan; Becker, Donald F; Dickman, Martin B

    2006-06-01

    Exogenous proline can protect cells of Saccharomyces cerevisiae from oxidative stress. We altered intracellular proline levels by overexpressing the proline dehydrogenase gene (PUT1) of S. cerevisiae. Put1p performs the first enzymatic step of proline degradation in S. cerevisiae. Overexpression of Put1p results in low proline levels and hypersensitivity to oxidants, such as hydrogen peroxide and paraquat. A put1-disrupted yeast mutant deficient in Put1p activity has increased protection from oxidative stress and increased proline levels. Following a conditional life/death screen in yeast, we identified a tomato (Lycopersicon esculentum) gene encoding a QM-like protein (tQM) and found that stable expression of tQM in the Put1p-overexpressing strain conferred protection against oxidative damage from H2O2, paraquat, and heat. This protection was correlated with reactive oxygen species (ROS) reduction and increased proline accumulation. A yeast two-hybrid system assay was used to show that tQM physically interacts with Put1p in yeast, suggesting that tQM is directly involved in modulating proline levels. tQM also can rescue yeast from the lethality mediated by the mammalian proapoptotic protein Bax, through the inhibition of ROS generation. Our results suggest that tQM is a component of various stress response pathways and may function in proline-mediated stress tolerance in plants.

  7. Whole-cell biocatalytic and de novo production of alkanes from free fatty acids in Saccharomyces cerevisiae.

    PubMed

    Foo, Jee Loon; Susanto, Adelia Vicanatalita; Keasling, Jay D; Leong, Susanna Su Jan; Chang, Matthew Wook

    2017-01-01

    Rapid global industrialization in the past decades has led to extensive utilization of fossil fuels, which resulted in pressing environmental problems due to excessive carbon emission. This prompted increasing interest in developing advanced biofuels with higher energy density to substitute fossil fuels and bio-alkane has gained attention as an ideal drop-in fuel candidate. Production of alkanes in bacteria has been widely studied but studies on the utilization of the robust yeast host, Saccharomyces cerevisiae, for alkane biosynthesis have been lacking. In this proof-of-principle study, we present the unprecedented engineering of S. cerevisiae for conversion of free fatty acids to alkanes. A fatty acid α-dioxygenase from Oryza sativa (rice) was expressed in S. cerevisiae to transform C12-18 free fatty acids to C11-17 aldehydes. Co-expression of a cyanobacterial aldehyde deformylating oxygenase converted the aldehydes to the desired alkanes. We demonstrated the versatility of the pathway by performing whole-cell biocatalytic conversion of exogenous free fatty acid feedstocks into alkanes as well as introducing the pathway into a free fatty acid overproducer for de novo production of alkanes from simple sugar. The results from this work are anticipated to advance the development of yeast hosts for alkane production. Biotechnol. Bioeng. 2017;114: 232-237. © 2016 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc. © 2016 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.

  8. Cell Surface Display of Four Types of Solanum nigrum Metallothionein on Saccharomyces cerevisiae for Biosorption of Cadmium.

    PubMed

    Wei, Qinguo; Zhang, Honghai; Guo, Dongge; Ma, Shisheng

    2016-05-28

    We displayed four types of Solanum nigrum metallothionein (SMT) for the first time on the surface of Saccharomyces cerevisiae using an α-agglutinin-based display system. The SMT genes were amplified by RT-PCR. The plasmid pYES2 was used to construct the expression vector. Transformed yeast strains were confirmed by PCR amplification and custom sequencing. Surface-expressed metallothioneins were indirectly indicated by the enhanced cadmium sorption capacity. Flame atomic absorption spectrophotometry was used to examine the concentration of Cd(2+) in this study. The transformed yeast strains showed much higher resistance ability to Cd(2+) compared with the control. Strikingly, their Cd(2+) accumulation was almost twice as much as that of the wild-type yeast cells. Furthermore, surface-engineered yeast strains could effectively adsorb ultra-trace cadmium and accumulate Cd(2+) under a wide range of pH levels, from 3 to 7, without disturbing the Cu(2+) and Hg(2+). Four types of surfaceengineered Saccharomyces cerevisiae strains were constructed and they could be used to purify Cd(2+)-contaminated water and adsorb ultra-trace cadmium effectively. The surface-engineered Saccharomyces cerevisiae strains would be useful tools for the bioremediation and biosorption of environmental cadmium contaminants.

  9. Whole‐cell biocatalytic and de novo production of alkanes from free fatty acids in Saccharomyces cerevisiae

    PubMed Central

    Foo, Jee Loon; Susanto, Adelia Vicanatalita; Keasling, Jay D.; Leong, Susanna Su Jan

    2016-01-01

    ABSTRACT Rapid global industrialization in the past decades has led to extensive utilization of fossil fuels, which resulted in pressing environmental problems due to excessive carbon emission. This prompted increasing interest in developing advanced biofuels with higher energy density to substitute fossil fuels and bio‐alkane has gained attention as an ideal drop‐in fuel candidate. Production of alkanes in bacteria has been widely studied but studies on the utilization of the robust yeast host, Saccharomyces cerevisiae, for alkane biosynthesis have been lacking. In this proof‐of‐principle study, we present the unprecedented engineering of S. cerevisiae for conversion of free fatty acids to alkanes. A fatty acid α‐dioxygenase from Oryza sativa (rice) was expressed in S. cerevisiae to transform C12–18 free fatty acids to C11–17 aldehydes. Co‐expression of a cyanobacterial aldehyde deformylating oxygenase converted the aldehydes to the desired alkanes. We demonstrated the versatility of the pathway by performing whole‐cell biocatalytic conversion of exogenous free fatty acid feedstocks into alkanes as well as introducing the pathway into a free fatty acid overproducer for de novo production of alkanes from simple sugar. The results from this work are anticipated to advance the development of yeast hosts for alkane production. Biotechnol. Bioeng. 2017;114: 232–237. © 2016 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc. PMID:26717118

  10. Tomato QM-Like Protein Protects Saccharomyces cerevisiae Cells against Oxidative Stress by Regulating Intracellular Proline Levels

    PubMed Central

    Chen, Changbin; Wanduragala, Srimevan; Becker, Donald F.; Dickman, Martin B.

    2006-01-01

    Exogenous proline can protect cells of Saccharomyces cerevisiae from oxidative stress. We altered intracellular proline levels by overexpressing the proline dehydrogenase gene (PUT1) of S. cerevisiae. Put1p performs the first enzymatic step of proline degradation in S. cerevisiae. Overexpression of Put1p results in low proline levels and hypersensitivity to oxidants, such as hydrogen peroxide and paraquat. A put1-disrupted yeast mutant deficient in Put1p activity has increased protection from oxidative stress and increased proline levels. Following a conditional life/death screen in yeast, we identified a tomato (Lycopersicon esculentum) gene encoding a QM-like protein (tQM) and found that stable expression of tQM in the Put1p-overexpressing strain conferred protection against oxidative damage from H2O2, paraquat, and heat. This protection was correlated with reactive oxygen species (ROS) reduction and increased proline accumulation. A yeast two-hybrid system assay was used to show that tQM physically interacts with Put1p in yeast, suggesting that tQM is directly involved in modulating proline levels. tQM also can rescue yeast from the lethality mediated by the mammalian proapoptotic protein Bax, through the inhibition of ROS generation. Our results suggest that tQM is a component of various stress response pathways and may function in proline-mediated stress tolerance in plants. PMID:16751508

  11. Rapid Identification and Enumeration of Saccharomyces cerevisiae Cells in Wine by Real-Time PCR

    PubMed Central

    Martorell, P.; Querol, A.; Fernández-Espinar, M. T.

    2005-01-01

    Despite the beneficial role of Saccharomyces cerevisiae in the food industry for food and beverage production, it is able to cause spoilage in wines. We have developed a real-time PCR method to directly detect and quantify this yeast species in wine samples to provide winemakers with a rapid and sensitive method to detect and prevent wine spoilage. Specific primers were designed for S. cerevisiae using the sequence information obtained from a cloned random amplified polymorphic DNA band that differentiated S. cerevisiae from its sibling species Saccharomyces bayanus, Saccharomyces pastorianus, and Saccharomyces paradoxus. The specificity of the primers was demonstrated for typical wine spoilage yeast species. The method was useful for estimating the level of S. cerevisiae directly in sweet wines and red wines without preenrichment when yeast is present in concentrations as low as 3.8 and 5 CFU per ml. This detection limit is in the same order as that obtained from glucose-peptone-yeast growth medium (GPY). Moreover, it was possible to quantify S. cerevisiae in artificially contaminated samples accurately. Limits for accurate quantification in wine were established, from 3.8 × 105 to 3.8 CFU/ml in sweet wine and from 5 × 106 to 50 CFU/ml in red wine. PMID:16269715

  12. Ammodytoxin, a secretory phospholipase A2, inhibits G2 cell-cycle arrest in the yeast Saccharomyces cerevisiae.

    PubMed

    Petrovic, Uros; Sribar, Jernej; Matis, Maja; Anderluh, Gregor; Peter-Katalinić, Jasna; Krizaj, Igor; Gubensek, Franc

    2005-10-15

    Ammodytoxin (Atx), an sPLA2 (secretory phospholipase A2), binds to g and e isoforms of porcine 14-3-3 proteins in vitro. 14-3-3 proteins are evolutionarily conserved eukaryotic regulatory proteins involved in a variety of biological processes, including cell-cycle regulation. We have now shown that Atx binds to yeast 14-3-3 proteins with an affinity similar to that for the mammalian isoforms. Thus yeast Saccharomyces cerevisiae can be used as a model eukaryotic cell, which lacks endogenous phospholipases A2, to assess the in vivo relevance of this interaction. Atx was expressed in yeast cells and shown to be biologically active inside the cells. It inhibited G2 cell-cycle arrest in yeast, which is regulated by 14-3-3 proteins. Interference with the cell cycle indicates a possible mechanism by which sPLA2s are able to cause the opposing effects, proliferation and apoptosis, in mammalian cells.

  13. Electricity generation from food wastes and microbial community structure in microbial fuel cells.

    PubMed

    Jia, Jianna; Tang, Yu; Liu, Bingfeng; Wu, Di; Ren, Nanqi; Xing, Defeng

    2013-09-01

    Microbial fuel cell (MFC) was studied as an alternate and a novel way to dispose food wastes (FWs) in a waste-to-energy form. Different organic loading rate obviously affected the performance of MFCs fed with FWs. The maximum power density of ~18 W/m(3) (~556 mW/m(2)) was obtained at COD of 3200±400 mg/L and the maximum coulombic efficiency (CE) was ~27.0% at COD of 4900±350 mg/L. The maximum removals of COD, total carbohydrate (TC) and total nitrogen (TN) were ~86.4%, ~95.9% and ~16.1%, respectively. Microbial community analysis using 454 pyrosequencing of 16S rRNA gene demonstrated the combination of the dominant genera of the exoelectrogenic Geobacter and fermentative Bacteroides effectively drove highly efficient and reliable MFC systems with functions of organic matters degradation and electricity generation.

  14. Microbial community structure accompanied with electricity production in a constructed wetland plant microbial fuel cell.

    PubMed

    Lu, Lu; Xing, Defeng; Ren, Zhiyong Jason

    2015-11-01

    This study reveals the complex structure of bacterial and archaeal communities associated with a Canna indica plant microbial fuel cell (PMFC) and its electricity production. The PMFC produced a maximum current of 105 mA/m(2) by utilizing rhizodeposits as the sole electron donor without any external nutrient or buffer supplements, which demonstrates the feasibility of PMFCs in practical oligotrophic conditions with low solution conductivity. The microbial diversity was significantly higher in the PMFC than non-plant controls or sediment-only controls, and pyrosequencing and clone library reveal that rhizodeposits conversion to current were carried out by syntrophic interactions between fermentative bacteria (e.g., Anaerolineaceae) and electrochemically active bacteria (e.g., Geobacter). Denitrifying bacteria and acetotrophic methanogens play a minor role in organics degradation, but abundant hydrogenotrophic methanogens and thermophilic archaea are likely main electron donor competitors.

  15. Microbial fuel cell (MFC) for bioelectricity generation from organic wastes.

    PubMed

    Moqsud, M Azizul; Omine, Kiyoshi; Yasufuku, Noriyuki; Hyodo, Masayuki; Nakata, Yukio

    2013-11-01

    Microbial fuel cells (MFCs) have gained a lot of attention recently as a mode of converting organic matter into electricity. In this study, a compost-based microbial fuel cell that generates bioelectricity by biodegradation of organic matter is developed. Grass cuttings, along with leaf mold, rice bran, oil cake (from mustard plants) and chicken droppings (waste from chickens) were used as organic waste. The electric properties of the MFC under anaerobic fermentation condition were investigated along with the influence of different types of membranes, the mixing of fly ash, and different types of electrode materials. It is observed that the maximum voltage was increased by mixing fly ash. Cellophane showed the highest value of voltage (around 350mV). Bamboo charcoal is good for anode material; however carbon fiber is better for the cathode material in terms of optimization of power generated. This developed MFC is a simple cell to generate electricity from organic waste.

  16. SWITCH: a dynamic CRISPR tool for genome engineering and metabolic pathway control for cell factory construction in Saccharomyces cerevisiae.

    PubMed

    Vanegas, Katherina García; Lehka, Beata Joanna; Mortensen, Uffe Hasbro

    2017-02-08

    The yeast Saccharomyces cerevisiae is increasingly used as a cell factory. However, cell factory construction time is a major obstacle towards using yeast for bio-production. Hence, tools to speed up cell factory construction are desirable. In this study, we have developed a new Cas9/dCas9 based system, SWITCH, which allows Saccharomyces cerevisiae strains to iteratively alternate between a genetic engineering state and a pathway control state. Since Cas9 induced recombination events are crucial for SWITCH efficiency, we first developed a technique TAPE, which we have successfully used to address protospacer efficiency. As proof of concept of the use of SWITCH in cell factory construction, we have exploited the genetic engineering state of a SWITCH strain to insert the five genes necessary for naringenin production. Next, the naringenin cell factory was switched to the pathway control state where production was optimized by downregulating an essential gene TSC13, hence, reducing formation of a byproduct. We have successfully integrated two CRISPR tools, one for genetic engineering and one for pathway control, into one system and successfully used it for cell factory construction.

  17. Whole cell immobilized amperometric biosensor based on Saccharomyces cerevisiae for selective determination of vitamin B1 (thiamine).

    PubMed

    Akyilmaz, Erol; Yaşa, Ihsan; Dinçkaya, Erhan

    2006-07-01

    A new amperometric whole cell biosensor based on Saccharomyces cerevisiae immobilized in gelatin was developed for selective determination of vitamin B1 (thiamine). The biosensor was constructed by using gelatin and crosslinking agent glutaraldehyde to immobilize S. cerevisiae cells on the Teflon membrane of dissolved oxygen (DO) probe used as the basic electrode system combined with a digital oxygen meter. The cells were induced by vitamin B1 in the culture medium, and the cells used it as a carbon source in the absence of glucose. So, when the vitamin B1 solution is injected into the whole cell biosensor system, an increase in respiration activity of the cells results from the metabolic activity and causes a decrease in the DO concentration of interval surface of DO probe related to vitamin B1 concentration. The response time of the biosensor is 3 min, and the optimal working conditions of the biosensor were carried out as pH 7.0, 50mM Tris-HCl, and 30 degrees C. A linear relationship was obtained between the DO concentration decrease and vitamin B1 concentration between 5.0 x 10(-3) and 10(-1) microM. In the application studies of the biosensor, sensitive determination of vitamin B1 in the vitamin tablets was investigated.

  18. Engineering of global regulators and cell surface properties toward enhancing stress tolerance in Saccharomyces cerevisiae.

    PubMed

    Kuroda, Kouichi; Ueda, Mitsuyoshi

    2017-07-13

    Microbial cell factories are subject to various stresses, leading to the reductions of metabolic activity and bioproduction efficiency. Therefore, the development of stress-tolerant microorganisms is important for improving bio-production efficiency. Recently, modifications of cell surface properties and master regulators have been shown to be effective approaches for enhancing stress tolerance. The cell surface is an attractive target owing to its interactions with the environment and its role in transmitting environmental information. Cell surface engineering in yeast has enabled the convenient modification of cell surface properties. Displaying random peptide libraries and subsequent screening can successfully improve stress tolerance. Furthermore, master regulators including transcription factors are also promising target to be engineered because stress tolerance is determined by many cooperative factors and modification of master regulators can simultaneously affect the expression of multiple downstream genes. The key single amino acid mutations in transcription factors have been identified by analyzing tolerant yeasts that were isolated by adaptive evolution under stress conditions. This enabled the reconstruction of stress-tolerant yeast without burdening cells by introducing the identified mutations. Therefore, for the construction of stress-tolerant yeast from any strains, these two approaches are promising alternatives to conventional overexpression and deletion of stress-related genes. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  19. Design of acoustic cell settler for filtering and recycling microbial cells.

    PubMed

    Hwang, Sung-Ho; Koo, Yoon-Mo

    2003-02-01

    An acoustic cell settler (ACS) using ultrasound at cells of 3 MHz was used to recycle Saccharomyces cerevisiae in a fermenter. The locations of both the inlet and outlet in the acoustic cell settler, which have a relatively long distance between the transducer and reflector, were optimized. A tilted settler was designed to make up for the defect in the horizontal ACS, which has a low recovery ratio. The tilted ACS gave a recovery ratio of yeast cells of about 5 during the most period of operation, which was twice that of the horizontal ACS.

  20. Deployable Microbial Fuel Cell and Methods

    DTIC Science & Technology

    2011-09-08

    cells and batteries and in particular to cathodes which are suitable for use in galvanic cells that use an oxidant dissolved in the electrolyte as...is preferably dried so the battery is activated when liquid contacts the electrolyte and separator layer. Water swellable particles are included...required divers to install graphite plates in the marine sediment. As noted above, this is a costly and time consuming process. In addition, the graphite

  1. Development of microbial cell factories for bio-refinery through synthetic bioengineering.

    PubMed

    Kondo, Akihiko; Ishii, Jun; Hara, Kiyotaka Y; Hasunuma, Tomohisa; Matsuda, Fumio

    2013-01-20

    Synthetic bioengineering is a strategy for developing useful microbial strains with innovative biological functions. Novel functions are designed and synthesized in host microbes with the aid of advanced technologies for computer simulations of cellular processes and the system-wide manipulation of host genomes. Here, we review the current status and future prospects of synthetic bioengineering in the yeast Saccharomyces cerevisiae for bio-refinery processes to produce various commodity chemicals from lignocellulosic biomass. Previous studies to improve assimilation of xylose and production of glutathione and butanol suggest a fixed pattern of problems that need to be solved, and as a crucial step, we now need to identify promising targets for further engineering of yeast metabolism. Metabolic simulation, transcriptomics, and metabolomics are useful emerging technologies for achieving this goal, making it possible to optimize metabolic pathways. Furthermore, novel genes responsible for target production can be found by analyzing large-scale data. Fine-tuning of enzyme activities is essential in the latter stage of strain development, but it requires detailed modeling of yeast metabolic functions. Recombinant technologies and genetic engineering are crucial for implementing metabolic designs into microbes. In addition to conventional gene manipulation techniques, advanced methods, such as multicistronic expression systems, marker-recycle gene deletion, protein engineering, cell surface display, genome editing, and synthesis of very long DNA fragments, will facilitate advances in synthetic bioengineering.

  2. The steady-state level and stability of TLS polymerase eta are cell cycle dependent in the yeast S. cerevisiae.

    PubMed

    Plachta, Michal; Halas, Agnieszka; McIntyre, Justyna; Sledziewska-Gojska, Ewa

    2015-05-01

    Polymerase eta (Pol eta) is a ubiquitous translesion DNA polymerase that is capable of bypassing UV-induced pyrimidine dimers in an error-free manner. However, this specialized polymerase is error prone when synthesizing through an undamaged DNA template. In Saccharomyces cerevisiae, both depletion and overproduction of Pol eta result in mutator phenotypes. Therefore, regulation of the cellular abundance of this enzyme is of particular interest. However, based on the investigation of variously tagged forms of Pol eta, mutually contradictory conclusions have been reached regarding the stability of this polymerase in yeast. Here, we optimized a protocol for the detection of untagged yeast Pol eta and established that the half-life of the native enzyme is 80 ± 14 min in asynchronously growing cultures. Experiments with synchronized cells indicated that the cellular abundance of this translesion polymerase changes throughout the cell cycle. Accordingly, we show that the stability of Pol eta, but not its mRNA level, is cell cycle stage dependent. The half-life of the polymerase is more than fourfold shorter in G1-arrested cells than in those at G2/M. Our results, in concert with previous data for Rev1, indicate that cell cycle regulation is a general property of Y family TLS polymerases in S. cerevisiae.

  3. Characterization of microbial fuel cells at microbially and electrochemically meaningful time scales.

    PubMed

    Ren, Zhiyong; Yan, Hengjing; Wang, Wei; Mench, Matthew M; Regan, John M

    2011-03-15

    The variable biocatalyst density in a microbial fuel cell (MFC) anode biofilm is a unique feature of MFCs relative to other electrochemical systems, yet performance characterizations of MFCs typically involve analyses at electrochemically relevant time scales that are insufficient to account for these variable biocatalyst effects. This study investigated the electrochemical performance and the development of anode biofilm architecture under different external loadings, with duplicate acetate-fed single-chamber MFCs stabilized at each resistance for microbially relevant time scales. Power density curves from these steady-state reactors generally showed comparable profiles despite the fact that anode biofilm architectures and communities varied considerably, showing that steady-state biofilm differences had little influence on electrochemical performance until the steady-state external loading was much larger than the reactor internal resistance. Filamentous bacteria were dominant on the anodes under high external resistances (1000 and 5000 Ω), while more diverse rod-shaped cells formed dense biofilms under lower resistances (10, 50, and 265 Ω). Anode charge transfer resistance decreased with decreasing fixed external resistances, but was consistently 2 orders of magnitude higher than the resistance at the cathode. Cell counting showed an inverse exponential correlation between cell numbers and external resistances. This direct link of MFC anode biofilm evolution with external resistance and electricity production offers several operational strategies for system optimization.

  4. Temporal Microbial Community Dynamics in Microbial Electrolysis Cells – Influence of Acetate and Propionate Concentration

    PubMed Central

    Hari, Ananda Rao; Venkidusamy, Krishnaveni; Katuri, Krishna P.; Bagchi, Samik; Saikaly, Pascal E.

    2017-01-01

    Microbial electrolysis cells (MECs) are widely considered as a next generation wastewater treatment system. However, fundamental insight on the temporal dynamics of microbial communities associated with MEC performance under different organic types with varied loading concentrations is still unknown, nevertheless this knowledge is essential for optimizing this technology for real-scale applications. Here, the temporal dynamics of anodic microbial communities associated with MEC performance was examined at low (0.5 g COD/L) and high (4 g COD/L) concentrations of acetate or propionate, which are important intermediates of fermentation of municipal wastewaters and sludge. The results showed that acetate-fed reactors exhibited higher performance in terms of maximum current density (I: 4.25 ± 0.23 A/m2), coulombic efficiency (CE: 95 ± 8%), and substrate degradation rate (98.8 ± 1.2%) than propionate-fed reactors (I: 2.7 ± 0.28 A/m2; CE: 68 ± 9.5%; substrate degradation rate: 84 ± 13%) irrespective of the concentrations tested. Despite of the repeated sampling of the anodic biofilm over time, the high-concentration reactors demonstrated lower and stable performance in terms of current density (I: 1.1 ± 0.14 to 4.2 ± 0.21 A/m2), coulombic efficiency (CE: 44 ± 4.1 to 103 ± 7.2%) and substrate degradation rate (64.9 ± 6.3 to 99.7 ± 0.5%), while the low-concentration reactors produced higher and dynamic performance (I: 1.1 ± 0.12 to 4.6 ± 0.1 A/m2; CE: 52 ± 2.5 to 105 ± 2.7%; substrate degradation rate: 87.2 ± 0.2 to 99.9 ± 0.06%) with the different substrates tested. Correlating reactor’s performance with temporal dynamics of microbial communities showed that relatively similar anodic microbial community composition but with varying relative abundances was observed in all the reactors despite differences in the substrate and concentrations tested. Particularly, Geobacter was the predominant bacteria on the anode biofilm of all MECs over time suggesting

  5. Carbon and nitrogen assimilation in deep subseafloor microbial cells.

    PubMed

    Morono, Yuki; Terada, Takeshi; Nishizawa, Manabu; Ito, Motoo; Hillion, François; Takahata, Naoto; Sano, Yuji; Inagaki, Fumio

    2011-11-08

    Remarkable numbers of microbial cells have been observed in global shallow to deep subseafloor sediments. Accumulating evidence indicates that deep and ancient sediments harbor living microbial life, where the flux of nutrients and energy are extremely low. However, their physiology and energy requirements remain largely unknown. We used stable isotope tracer incubation and nanometer-scale secondary ion MS to investigate the dynamics of carbon and nitrogen assimilation activities in individual microbial cells from 219-m-deep lower Pleistocene (460,000 y old) sediments from the northwestern Pacific off the Shimokita Peninsula of Japan. Sediment samples were incubated in vitro with (13)C- and/or (15)N-labeled glucose, pyruvate, acetate, bicarbonate, methane, ammonium, and amino acids. Significant incorporation of (13)C and/or (15)N and growth occurred in response to glucose, pyruvate, and amino acids (∼76% of total cells), whereas acetate and bicarbonate were incorporated without fostering growth. Among those substrates, a maximum substrate assimilation rate was observed at 67 × 10(-18) mol/cell per d with bicarbonate. Neither carbon assimilation nor growth was evident in response to methane. The atomic ratios between nitrogen incorporated from ammonium and the total cellular nitrogen consistently exceeded the ratios of carbon, suggesting that subseafloor microbes preferentially require nitrogen assimilation for the recovery in vitro. Our results showed that the most deeply buried subseafloor sedimentary microbes maintain potentials for metabolic activities and that growth is generally limited by energy but not by the availability of C and N compounds.

  6. Effects of Saccharomyces cerevisiae fermentation product on in vitro fermentation and microbial communities of low-quality forages and mixed diets.

    PubMed

    Mao, Hui-ling; Mao, Hua-long; Wang, J K; Liu, J X; Yoon, I

    2013-07-01

    Two experiments were conducted to investigate the effects of a Saccharomyces cerevisiae fermentation product (XP, Diamond V, Cedar Rapids, IA) on in vitro ruminal fermentation of single forage and mixed diets. In Exp. 1, an in vitro test was used to determine the effects of various concentrations (0, 1, 2, and 3 g/L) of XP on ruminal fermentation of the major forage sources of China (rice straw, RS; corn stover, CS; corn silage without grain, CSNG; and corn silage with grain, CSG). Total VFA reached a peak at 1 g/L XP for RS, CSNG, and CSG and increased linearly (P < 0.01) for CS. The molar proportion of acetate decreased and propionate increased linearly (P < 0.01) with an increasing amount of XP for RS, CS, and CSNG. Microbial protein (MCP) increased linearly (P < 0.01) with an increasing level of XP for RS, and it reached peak values at 1 and 2 g/L XP for CSG and CSNG, respectively. Fungi population was increased (P < 0.05) with 1 g/L XP for all forages except CSNG. The population of Ruminococcus flavefaciens increased (P < 0.05) at 1 or 2 g/L XP for RS, CSNG, and CSG. In Exp. 2, the effects of 3 concentrations of XP (0, 1, and 2 g/L) were tested on in vitro ruminal fermentation of 3 mixed diets with various ingredient combinations: 1) CSC (corn:soybean meal:corn stover = 33:22:45), 2) CSCC (corn:soybean meal:corn stover:corn silage = 33:22:22.5:22.5), and 3) CSCCA (corn:soybean meal:corn stover:corn silage:alfalfa = 33:22:19:21:5). Total VFA concentrations were influenced by diets (P < 0.01) and were enhanced linearly by increasing concentrations of XP (P < 0.01). The molar proportion of acetate was reduced (P < 0.01), but the propionate proportion was enhanced with increasing concentrations of XP (P < 0.01). Ammonia N was decreased and MCP was increased by the addition of XP (linear, P < 0.01; quadratic, P < 0.05). The fungi population was greater with XP addition (quadratic, P < 0.01). The percentage of R. albus was affected by diets (P < 0.01), the level of

  7. Microbial communities change in an anaerobic digestion after application of microbial electrolysis cells.

    PubMed

    Lee, Beom; Park, Jun-Gyu; Shin, Won-Beom; Tian, Dong-Jie; Jun, Hang-Bae

    2017-06-01

    Microbial electrolysis cells (MECs) are being studied to improve the efficiency of anaerobic digesters and biogas production. In the present study, we investigated the effects of electrochemical reactions in AD-MEC (anaerobic digester combined with MECs) on changes in the microbial communities of bulk sludge through 454-pyrosequencing analysis, as well as the effect of these changes on anaerobic digestion. Methanobacterium beijingense and Methanobacterium petrolearium were the dominant archaeal species in AD, while Methanosarcina thermophila and Methanobacterium formicicum were dominant in AD-MEC at steady-state. There were no substantial differences in dominant bacterial species. Clostridia class was more abundant than Bacteroidia class in both reactors. Compared to AD, AD-MEC showed a 40% increase in overall bacterial population, increasing the removal of organic matters and the conversion of volatile fatty acids (VFAs). Thus, the MEC reaction more effectively converts organic matters to VFAs and activates microbial communities favorable for methane production. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Effect of electricity on microbial community of microbial fuel cell simultaneously treating sulfide and nitrate

    NASA Astrophysics Data System (ADS)

    Cai, Jing; Zheng, Ping; Xing, Yajuan; Qaisar, Mahmood

    2015-05-01

    The effect of electric current on microbial community is explored in Microbial Fuel Cells (MFCs) simultaneously treating sulfide and nitrate. The MFCs are operated under four different conditions which exhibited different characteristics of electricity generation. In batch mode, MFCs generate intermittently high current pulses in the beginning, and the current density is instable subsequently, while the current density of MFCs in continuous mode is relatively stable. All operational parameters show good capacity for substrate removal, and nitrogen and sulfate were the main reaction products. Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) analysis is employed to obtain profiles of the bacterial communities present in inoculum and suspension of four MFCs. Based on the community diversity indices and Spearman correlation analyses, significant correlation exists between Richness of the community of anode chamber and the electricity generated, while no strong correlation is evident between other indexes (Shannon index, Simpson index and Equitability index) and the electricity. Additionally, the results of Principal Component Analysis (PCA) suggest that MFCs suffering from current shock have similar suspension communities, while the others have diverse microbial communities.

  9. Enhanced microbial reduction of vanadium (V) in groundwater with bioelectricity from microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Hao, Liting; Zhang, Baogang; Tian, Caixing; Liu, Ye; Shi, Chunhong; Cheng, Ming; Feng, Chuanping

    2015-08-01

    Bioelectricity generated from the microbial fuel cell (MFC) is applied to the bioelectrical reactor (BER) directly to enhance microbial reduction of vanadium (V) (V(V)) in groundwater. With the maximum power density of 543.4 mW m-2 from the MFC, V(V) removal is accelerated with efficiency of 93.6% during 12 h operation. Higher applied voltage can facilitate this process. V(V) removals decrease with the increase of initial V(V) concentration, while extra addition of chemical oxygen demand (COD) has little effect on performance improvement. Microbial V(V) reduction is enhanced and then suppressed with the increase of conductivity. High-throughput 16S rRNA gene pyrosequencing analysis implies the accumulated Enterobacter and Lactococcus reduce V(V) with products from fermentative microorganisms such as Macellibacteroides. The presentation of electrochemically active bacteria as Enterobacter promotes electron transfers. This study indicates that application of bioelectricity from MFCs is a promising strategy to improve the efficiency of in-situ bioremediation of V(V) polluted groundwater.

  10. Ohmic resistance affects microbial community and electrochemical kinetics in a multi-anode microbial electrochemical cell

    NASA Astrophysics Data System (ADS)

    Dhar, Bipro Ranjan; Ryu, Hodon; Santo Domingo, Jorge W.; Lee, Hyung-Sool

    2016-11-01

    Multi-anode microbial electrochemical cells (MxCs) are considered as one of the most promising configurations for scale-up of MxCs, but understanding of anode kinetics in multiple anodes is limited in the MxCs. In this study we assessed microbial community and electrochemical kinetic parameters for biofilms on individual anodes in a multi-anode MxC to better comprehend anode fundamentals. Microbial community analysis targeting 16S rRNA Illumina sequencing showed that Geobacter genus was abundant (87%) only on the biofilm anode closest to a reference electrode (low ohmic energy loss) in which current density was the highest among three anodes. In comparison, Geobacter populations were less than 1% for biofilms on other two anodes distant from the reference electrode (high ohmic energy loss), generating small current density. Half-saturation anode potential (EKA) was the lowest at -0.251 to -0.242 V (vs. standard hydrogen electrode) for the closest biofilm anode to the reference electrode, while EKA was as high as -0.134 V for the farthest anode. Our study proves that electric potential of individual anodes changed by ohmic energy loss shifts biofilm communities on individual anodes and consequently influences electron transfer kinetics on each anode in the multi-anode MxC.

  11. Short polyhistidine peptides penetrate effectively into Nicotiana tabacum-cultured cells and Saccharomyces cerevisiae cells.

    PubMed

    Kimura, Sayaka; Kawano, Tsuyoshi; Iwasaki, Takashi

    2017-01-01

    The polyhistidine peptides (PHPs) have been previously reported as novel cell-penetrating peptides and are efficiently internalized into mammal cells; however, penetration of PHPs into other cell types is unknown. In this study, the cellular uptake of PHPs in plant and yeast cells was found to be dependent on the number of histidines, and short PHPs (H6-H10 peptides) showed effective internalization. The H8 peptide showed the highest cell-penetrating capacity and localized to vacuoles in plant and yeast cells. Low-temperature conditions inhibited significantly the cellular uptake of short PHPs by both cells. However, net charge neutralization of PHPs also completely inhibited cellular uptake by plant cells, but not by yeast cells. These results indicate that short PHPs penetrate effectively into plant and yeast cells by similar mechanism with the exception of net charge dependency. The findings show the short PHPs are promising candidates for new delivery tools into plant and yeast cells.

  12. Microbial community structures differentiated in a single-chamber air-cathode microbial fuel cell fueled with rice straw hydrolysate.

    PubMed

    Wang, Zejie; Lee, Taekwon; Lim, Bongsu; Choi, Chansoo; Park, Joonhong

    2014-01-17

    The microbial fuel cell represents a novel technology to simultaneously generate electric power and treat wastewater. Both pure organic matter and real wastewater can be used as fuel to generate electric power and the substrate type can influence the microbial community structure. In the present study, rice straw, an important feedstock source in the world, was used as fuel after pretreatment with diluted acid method for a microbial fuel cell to obtain electric power. Moreover, the microbial community structures of anodic and cathodic biofilm and planktonic culturewere analyzed and compared to reveal the effect of niche on microbial community structure. The microbial fuel cell produced a maximum power density of 137.6 ± 15.5 mW/m2 at a COD concentration of 400 mg/L, which was further increased to 293.33 ± 7.89 mW/m2 through adjusting the electrolyte conductivity from 5.6 mS/cm to 17 mS/cm. Microbial community analysis showed reduction of the microbial diversities of the anodic biofilm and planktonic culture, whereas diversity of the cathodic biofilm was increased. Planktonic microbial communities were clustered closer to the anodic microbial communities compared to the cathodic biofilm. The differentiation in microbial community structure of the samples was caused by minor portion of the genus. The three samples shared the same predominant phylum of Proteobacteria. The abundance of exoelectrogenic genus was increased with Desulfobulbus as the shared most abundant genus; while the most abundant exoelectrogenic genus of Clostridium in the inoculum was reduced. Sulfate reducing bacteria accounted for large relative abundance in all the samples, whereas the relative abundance varied in different samples. The results demonstrated that rice straw hydrolysate can be used as fuel for microbial fuel cells; microbial community structure differentiated depending on niches after microbial fuel cell operation; exoelectrogens were enriched; sulfate from rice straw

  13. Microbial cell retention in a melting High Arctic snowpack, Svalbard

    NASA Astrophysics Data System (ADS)

    Zarsky, Jakub; Björkman, Mats; Kühnel, Rafael; Hell, Katherina; Hodson, Andy; Sattler, Birgit; Psenner, Roland

    2014-05-01

    Introduction The melting snow pack represents a highly dynamic system not only for chemical compounds but also for bacterial cells. Microbial activity was found at subzero temperatures in ice veins when liquid water persists due to high concentration of ions on the surface of snow crystals and brine channels between large ice crystals in ice. Several observations also suggest microbial activity under subzero temperatures in seasonal snow. Even with regard to the spatial and temporal relevance of snow ecosystems, microbial activity in such an extreme habitat represents a relatively small proportion in the carbon flux of the global ecosystem and even of the glacial ecosystems specifically. On the other hand, it represents a remarkable piece of mosaic of the microbial activity in glacial ecosystems because the snow pack represents the first contact between the atmosphere and cryosphere. This topic also embodies vital crossovers to biogeochemistry and ecotoxicology, offering a quantitative view of utilization of various substrates relevant for downstream ecosystems. Here we present our study of the dynamics of both solvents and cells suspended in meltwater of the melting snowpack on a high arctic glacier to demonstrate the spatio-temporal constraint of interaction between solvent and bacterial cells in this environment. Method We used 6 lysimeters inserted into the bottom of the snowpack to collect replicated samples of melt water before it comes into contact with basal ice or slush layer at the base of the snow pack. The sampling site was chosen at Midre Lovénbreen (Svalbard, Kongsfjorden, MLB stake 6) where the snow pack showed melting on the surface but the basal ice was still dry. Sampling was conducted in June 2010 for a period of 10 days once per day and the snow profile was sampled according to distinguished layers in the profile at the beginning of the field mission and as bulk at its end. The height of snow above the lysimeters dropped from the initial 74 cm

  14. Composite materials for polymer electrolyte membrane microbial fuel cells.

    PubMed

    Antolini, Ermete

    2015-07-15

    Recently, the feasibility of using composite metal-carbon, metal-polymer, polymer-carbon, polymer-polymer and carbon-carbon materials in microbial fuel cells (MFCs) has been investigated. These materials have been tested as MFC anode catalyst (microorganism) supports, cathode catalysts and membranes. These hybrid materials, possessing the properties of each component, or even with a synergistic effect, would present improved characteristics with respect to the bare components. In this paper we present an overview of the use of these composite materials in microbial fuel cells. The characteristics of the composite materials as well as their effect on MFC performance were compared with those of the individual component and/or the conventionally used materials.

  15. Produced Water Treatment Using Microbial Fuel Cell Technology

    SciTech Connect

    Borole, A. P.; Campbell, R.

    2011-05-20

    ORNL has developed a treatment for produced water using a combination of microbial fuel cells and electrosorption. A collaboration between Campbell Applied Physics and ORNL was initiated to further investigate development of the technology and apply it to treatment of field produced water. The project successfully demonstrated the potential of microbial fuel cells to generate electricity from organics in produced water. A steady voltage was continuously generated for several days using the system developed in this study. In addition to the extraction of electrical energy from the organic contaminants, use of the energy at the representative voltage was demonstrated for salts removal or desalination of the produced water. Thus, the technology has potential to remove organic as well as ionic contaminants with minimal energy input using this technology. This is a novel energy-efficient method to treat produced water. Funding to test the technology at larger scale is being pursued to enable application development.

  16. Recent developments in microbial fuel cell technologies for sustainable bioenergy.

    PubMed

    Watanabe, Kazuya

    2008-12-01

    Microbial fuel cells (MFCs) are devices that exploit microbial catabolic activities to generate electricity from a variety of materials, including complex organic waste and renewable biomass. These sources provide MFCs with a great advantage over chemical fuel cells that can utilize only purified reactive fuels (e.g., hydrogen). A developing primary application of MFCs is its use in the production of sustainable bioenergy, e.g., organic waste treatment coupled with electricity generation, although further technical developments are necessary for its practical use. In this article, recent advances in MFC technologies that can become fundamentals for future practical MFC developments are summarized. Results of recent studies suggest that MFCs will be of practical use in the near future and will become a preferred option among sustainable bioenergy processes.

  17. New insights in Microbial Fuel Cells: novel solid phase anolyte

    NASA Astrophysics Data System (ADS)

    Tommasi, Tonia; Salvador, Gian Paolo; Quaglio, Marzia

    2016-07-01

    For the development of long lasting portable microbial fuel cells (MFCs) new strategies are necessary to overcome critical issues such as hydraulic pump system and the biochemical substrate retrieval overtime to sustain bacteria metabolism. The present work proposes the use of a synthetic solid anolyte (SSA), constituted by agar, carbonaceous and nitrogen sources dissolved into diluted seawater. Results of a month-test showed the potential of the new SSA-MFC as a long lasting low energy consuming system.

  18. New insights in Microbial Fuel Cells: novel solid phase anolyte

    PubMed Central

    Tommasi, Tonia; Salvador, Gian Paolo; Quaglio, Marzia

    2016-01-01

    For the development of long lasting portable microbial fuel cells (MFCs) new strategies are necessary to overcome critical issues such as hydraulic pump system and the biochemical substrate retrieval overtime to sustain bacteria metabolism. The present work proposes the use of a synthetic solid anolyte (SSA), constituted by agar, carbonaceous and nitrogen sources dissolved into diluted seawater. Results of a month-test showed the potential of the new SSA-MFC as a long lasting low energy consuming system. PMID:27375205

  19. New insights in Microbial Fuel Cells: novel solid phase anolyte.

    PubMed

    Tommasi, Tonia; Salvador, Gian Paolo; Quaglio, Marzia

    2016-07-04

    For the development of long lasting portable microbial fuel cells (MFCs) new strategies are necessary to overcome critical issues such as hydraulic pump system and the biochemical substrate retrieval overtime to sustain bacteria metabolism. The present work proposes the use of a synthetic solid anolyte (SSA), constituted by agar, carbonaceous and nitrogen sources dissolved into diluted seawater. Results of a month-test showed the potential of the new SSA-MFC as a long lasting low energy consuming system.

  20. Enzyme Amplified Detection of Microbial Cell Wall Components

    NASA Technical Reports Server (NTRS)

    Wainwright, Norman R.

    2004-01-01

    This proposal is MBL's portion of NASA's Johnson Space Center's Astrobiology Center led by Principal Investigator, Dr. David McKay, entitled: 'Institute for the Study of Biomarkers in Astromaterials.' Dr. Norman Wainwright is the principal investigator at MBL and is responsible for developing methods to detect trace quantities of microbial cell wall chemicals using the enzyme amplification system of Limulus polyphemus and other related methods.

  1. Enzyme Amplified Detection of Microbial Cell Wall Components

    NASA Technical Reports Server (NTRS)

    Wainwright, Norman R.

    2004-01-01

    This proposal is MBL's portion of NASA's Johnson Space Center's Astrobiology Center led by Principal Investigator, Dr. David McKay, entitled: 'Institute for the Study of Biomarkers in Astromaterials.' Dr. Norman Wainwright is the principal investigator at MBL and is responsible for developing methods to detect trace quantities of microbial cell wall chemicals using the enzyme amplification system of Limulus polyphemus and other related methods.

  2. Determining the fate of fluorescent quantum dots on surface of engineered budding S. cerevisiae cell molecular landscape.

    PubMed

    Chouhan, Raghuraj S; Qureshi, Anjum; Niazi, Javed H

    2015-07-15

    In this study, we surface engineered living S. cerevisiae cells by decorating quantum dots (QDs) and traced the fate of QDs on molecular landscape of single mother cell through several generation times (progeny cells). The fate of QDs on cell-surface was tracked through the cellular division events using confocal microscopy and fluorescence emission profiles. The extent of cell-surface QDs distribution among the offspring was determined as the mother cell divides into daughter cells. Fluorescence emission from QDs on progeny cells was persistent through the second-generation time (~240min) until all of the progeny cells lost their cell-bound QDs during the third generation time (~360min). The surface engineered yeast cells were unaffected by the QDs present on their molecular landscapes and retained their normal cellular growth, architecture and metabolic activities as confirmed by their viability, scanning electron microscopy (SEM) examinations and cytotoxicity tests, respectively. Our results demonstrated that QDs on mother cell landscape tend to distribute among its progeny cells that accompanied with concomitant reduction in QDs' fluorescence, which can be quantified. We suggest that surface engineered cells with QDs will enable investigating the cellular behavior and monitoring cell growth patterns as nanobiosensors for screening of drugs/chemicals at single cell level with fewer side effects. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Electricity generation from synthesis gas by microbial processes: CO fermentation and microbial fuel cell technology.

    PubMed

    Kim, Daehee; Chang, In Seop

    2009-10-01

    A microbiological process was established to harvest electricity from the carbon monoxide (CO). A CO fermenter was enriched with CO as the sole carbon source. The DGGE/DNA sequencing results showed that Acetobacterium spp. were enriched from the anaerobic digester fluid. After the fermenter was operated under continuous mode, the products were then continuously fed to the microbial fuel cell (MFC) to generate electricity. Even though the conversion yield was quite low, this study proved that synthesis gas (syn-gas) can be converted to electricity with the aid of microbes that do not possess the drawbacks of metal catalysts of conventional methods.

  4. Antimicrobial action of palmarosa oil (Cymbopogon martinii) on Saccharomyces cerevisiae.

    PubMed

    Prashar, Anjali; Hili, Pauline; Veness, Robert G; Evans, Christine S

    2003-07-01

    The essential oil extracted from palmarosa (Cymbopogon martinii) has proven anti-microbial properties against cells of Saccharomyces cerevisiae. Low concentrations of the oil (0.1%) inhibited the growth of S. cerevisiae cells completely. The composition of the sample of palmarosa oil was determined as 65% geraniol and 20% geranyl acetate as confirmed by GC-FTIR. The effect of palmarosa oil in causing K(+) leakage from yeast cells was attributed mainly to geraniol. Some leakage of magnesium ions was also observed. Blocking potassium membrane channels with caesium ions before addition of palmarosa oil did not change the extent of K(+) ion leakage, which was equal to the total sequestered K(+) in the cells. Palmarosa oil led to changes in the composition of the yeast cell membrane, with more saturated and less unsaturated fatty acids in the membrane after exposure of S. cerevisiae cells to the oil. Some of the palmarosa oil was lost by volatilization during incubation of the oil with the yeast cells. The actual concentration of the oil components affecting the yeast cells could not therefore be accurately determined.

  5. [Electricity production from surplus sludge using microbial fuel cells].

    PubMed

    Jia, Bin; Liu, Zhi-Hua; Li, Xiao-Ming; Yang, Yong-Lin; Yang, Qi; Zeng, Guang-Ming; Liu, Yi-Lin; Liu, Qian-Qian; Zheng, Shi-Wen

    2009-04-15

    A single-chamber and membrane-less microbial fuel cells were successfully started up using anaerobic sludge as inoculums without any chemical substance for 20 d. The electricity generation of the microbial fuel cell using surplus sludge as fuel and the change of substrate were investigated. The results showed that the obtained maximum voltage and power density were 495 mV and 44 mW x m(-2) (fixed 1,000 Omega), and the internal resistance was about 300 Omega during steady state. In a cycle, the removal efficiency of SS and VSS were 27.3% and 28.7%, pH was 6.5-8.0. In addition, the COD increased from 617 mg x L(-1) to 1,150 mg x L(-1) and decreased afterwards with time. The change of glucose was similar to that of COD, glucose increased from 47 mg x L(-1) to 60 mg x L(-1) and decreased afterwards with time. Consequently, the microbial fuel cell can transform chemical energy of surplus sludge into the cleanest electrical energy, and it provides a new way of sludge recycling.

  6. A computational model for biofilm-based microbial fuel cells.

    PubMed

    Picioreanu, Cristian; Head, Ian M; Katuri, Krishna P; van Loosdrecht, Mark C M; Scott, Keith

    2007-07-01

    This study describes and evaluates a computational model for microbial fuel cells (MFCs) based on redox mediators with several populations of suspended and attached biofilm microorganisms, and multiple dissolved chemical species. A number of biological, chemical and electrochemical reactions can occur in the bulk liquid, in the biofilm and at the electrode surface. The evolution in time of important MFC parameters (current, charge, voltage and power production, consumption of substrates, suspended and attached biomass growth) has been simulated under several operational conditions. Model calculations evaluated the effect of different substrate utilization yields, standard potential of the redox mediator, ratio of suspended to biofilm cells, initial substrate and mediator concentrations, mediator diffusivity, mass transfer boundary layer, external load resistance, endogenous metabolism, repeated substrate additions and competition between different microbial groups in the biofilm. Two- and three-dimensional model simulations revealed the heterogeneous current distribution over the planar anode surface for younger and patchy biofilms, but becoming uniform in older and more homogeneous biofilms. For uniformly flat biofilms one-dimensional models should give sufficiently accurate descriptions of produced currents. Voltage- and power-current characteristics can also be calculated at different moments in time to evaluate the limiting regime in which the MFC operates. Finally, the model predictions are tested with previously reported experimental data obtained in a batch MFC with a Geobacter biofilm fed with acetate. The potential of the general modeling framework presented here is in the understanding and design of more complex cases of wastewater-fed microbial fuel cells.

  7. Simultaneous Alcoholic and Malolactic Fermentations by Saccharomyces cerevisiae and Oenococcus oeni Cells Co-immobilized in Alginate Beads

    PubMed Central

    Bleve, Gianluca; Tufariello, Maria; Vetrano, Cosimo; Mita, Giovanni; Grieco, Francesco

    2016-01-01

    Malolactic fermentation (MLF) usually takes place after the end of alcoholic fermentation (AF). However, the inoculation of lactic acid bacteria together with yeast starter cultures is a promising system to enhance the quality and safety of wine. In recent years, the use of immobilized cell systems has been investigated, with interesting results, for the production of different fermented foods and beverages. In this study we have carried out the simultaneous immobilization of Saccharomyces cerevisiae and Oenococcus oeni in alginate beads and used them in microvinifications tests to produce Negroamaro wine. The process was monitored by chemical and sensorial analyses and dominance of starters and cell leaking from beads were also checked. Co-immobilization of S. cerevisiae and O. oeni allowed to perform an efficient fermentation process, producing low volatile acidity levels and ethanol and glycerol concentrations comparable with those obtained by cell sequential inoculum and co-inoculum of yeast and bacteria cells in free form. More importantly, co-immobilization strategy produced a significant decrease of the time requested to complete AF and MLF. The immobilized cells could be efficiently reused for the wine fermentation at least three times without any apparent loss of cell metabolic activities. This integrated biocatalytic system is able to perform simultaneously AF and MLF, producing wines similar in organoleptic traits in comparison with wines fermented following traditional sequential AF and MLF with free cell starters. The immobilized-cell system, that we here describe for the first time in our knowledge, offers many advantages over conventional free cell fermentations, including: (i) elimination of non-productive cell growth phases; (ii) feasibility of continuous processing; (iii) re-use of the biocatalyst. PMID:27379072

  8. Innate immune recognition of microbial cell wall components and microbial strategies to evade such recognitions.

    PubMed

    Sukhithasri, V; Nisha, N; Biswas, Lalitha; Anil Kumar, V; Biswas, Raja

    2013-08-25

    The innate immune system constitutes the first line of defence against invading microbes. The basis of this defence resides in the recognition of defined structural motifs of the microbes called "Microbial associated molecular patterns" that are absent in the host. Cell wall, the outer layer of both bacterial and fungal cells, a unique structure that is absent in the host and is recognized by the germ line encoded host receptors. Nucleotide oligomerization domain proteins, peptidoglycan recognition proteins and C-type lectins are host receptors that are involved in the recognition of bacterial cell wall (usually called peptidoglycan), whereas fungal cell wall components (N- and O-linked mannans, β-glucans etc.) are recognized by host receptors like C-type lectins (Dectin-1, Dectin-2, mannose receptor, DC-SIGN), Toll like receptors-2 and -4 (TLR-2 and TLR-4). These recognitions lead to activation of a variety of host signaling cascades and ultimate production of anti-microbial compounds including phospholipase A2, antimicrobial peptides, lysozyme, reactive oxygen and nitrogen species. These molecules act in cohort against the invading microbes to eradicate infections. Additionally pathogen recognition leads to the production of cytokines, which further activate the adaptive immune system. Both pathogenic and commensal bacteria and fungus use numerous strategies to subvert the host defence. These strategies include bacterial peptidoglycan glycan backbone modifications by O-acetylation, N-deacetylation, N-glycolylation and stem peptide modifications by amidation of meso-Diaminopimelic acid; fungal cell wall modifications by shielding the β-glucan layer with mannoproteins and α-1,3 glucan. This review focuses on the recent advances in understanding the role of bacterial and fungal cell wall in their innate immune recognition and evasion strategies. Copyright © 2013 Elsevier GmbH. All rights reserved.

  9. In Situ fuel processing in a microbial fuel cell.

    PubMed

    Bahartan, Karnit; Amir, Liron; Israel, Alvaro; Lichtenstein, Rachel G; Alfonta, Lital

    2012-09-01

    A microbial fuel cell (MFC) was designed in which fuel is generated in the cell by the enzyme glucoamylase, which is displayed on the surface of yeast. The enzyme digests starch specifically into monomeric glucose units and as a consequence enables further glucose oxidation by microorganisms present in the MFC anode. The oxidative enzyme glucose oxidase was coupled to the glucoamylase digestive enzyme. When both enzymes were displayed on the surface of yeast cells in a mixed culture, superior fuel-cell performance was observed in comparison with other combinations of yeast cells, unmodified yeast, or pure enzymes. The feasibility of the use of the green macroalgae Ulva lactuca in such a genetically modified MFC was also demonstrated. Herein, we report the performance of such fuel cells as a proof of concept for the enzymatic digestion of complex organic fuels in the anode of MFCs to render the fuel more available to microorganisms.

  10. Individual cells of Saccharomyces cerevisiae and Zygosaccharomyces bailii exhibit different short-term intracellular pH responses to acetic acid.

    PubMed

    Arneborg, N; Jespersen, L; Jakobsen, M

    2000-01-01

    The effects of perfusion with 2.7 and 26 mM undissociated acetic acid in the absence or presence of glucose on short-term intracellular pH (pH(i)) changes in individual Saccharormyces cerevisiae and Zygosaccharomyces bailii cells were studied using fluorescence-ratio-imaging microscopy and a perfusion system. In the S. cerevisiae cells, perfusion with acetic acid induced strong short-term pH(i) responses, which were dependent on the undissociated acetic acid concentration and the presence of glucose in the perfusion solutions. In the Z. bailii cells, perfusion with acetic acid induced only very weak short-term pH(i) responses, which were neither dependent on the undissociated acetic acid concentration nor on the presence of glucose in the perfusion solutions. These results clearly show that Z. bailii is more resistant than S. cerevisiae to short-term pH(i) changes caused by acetic acid.

  11. Binding Specificity of Piliated Strains of Escherichia coli and Salmonella typhimurium to Epithelial Cells, Saccharomyces cerevisiae Cells, and Erythrocytes

    PubMed Central

    Korhonen, Timo K.; Leffler, Hakon; Edén, Catharina Svanborg

    1981-01-01

    The binding to mammalian cells of piliated enteric bacteria and the inhibition of the binding by antibodies to purified pili were studied. The target cells were epithelial cells from human bucca and human and rat urinary tracts, erythrocytes from various species, and Saccharomyces cerevisiae cells. The strains were selected to represent the two main agglutination patterns of enteric bacteria: mannose-resistant agglutination of human and other erythrocytes and mannose-sensitive agglutination of guinea pig and other erythrocytes. Escherichia coli 3669 caused only mannose-resistant agglutination, E. coli 6013 caused only mannose-sensitive agglutination, and E. coli 3048 caused both types of agglutination simultaneously. Salmonella typhimurium SH6749 exhibited only mannose-sensitive hemagglutination and was included to allow comparison of its pili with those of E. coli strains. The range of epithelial cells to which the bacteria adhered was related to their agglutination patterns. All four strains attached to human buccal cells. Only E. coli strains 3669 and 3048, which caused mannose-resistant agglutination, adhered to human urinary tract epithelial cells, and only those strains that caused mannose-sensitive agglutination adhered to rat urinary tract epithelial cells. The binding of S. typhimurium SH6749, but not of the other strains with mannose-sensitive agglutination, was significantly inhibited by d-mannose. Globotetraosylceramide, a glycolipid present in the human urinary tract epithelium, inhibited attachment to human uroepithelial cells of the two strains with mannose-resistant hemagglutination. As tested by the enzyme-linked immunosorbent assay, cross-reactions between type 1 pili of the E. coli strains were strong, but those between S. typhimurium and E. coli mannose-sensitive pili were weak. The two pili that induced mannose-resistant hemagglutination on E. coli did not cross-react. Significant inhibition of adhesion of all four strains was obtained with the

  12. Proximity effect among cellulose-degrading enzymes displayed on the Saccharomyces cerevisiae cell surface.

    PubMed

    Bae, Jungu; Kuroda, Kouichi; Ueda, Mitsuyoshi

    2015-01-01

    Proximity effect is a form of synergistic effect exhibited when cellulases work within a short distance from each other, and this effect can be a key factor in enhancing saccharification efficiency. In this study, we evaluated the proximity effect between 3 cellulose-degrading enzymes displayed on the Saccharomyces cerevisiae cell surface, that is, endoglucanase, cellobiohydrolase, and β-glucosidase. We constructed 2 kinds of arming yeasts through genome integration: ALL-yeast, which simultaneously displayed the 3 cellulases (thus, the different cellulases were near each other), and MIX-yeast, a mixture of 3 kinds of single-cellulase-displaying yeasts (the cellulases were far apart). The cellulases were tagged with a fluorescence protein or polypeptide to visualize and quantify their display. To evaluate the proximity effect, we compared the activities of ALL-yeast and MIX-yeast with respect to degrading phosphoric acid-swollen cellulose after adjusting for the cellulase amounts. ALL-yeast exhibited 1.25-fold or 2.22-fold higher activity than MIX-yeast did at a yeast concentration equal to the yeast cell number in 1 ml of yeast suspension with an optical density (OD) at 600 nm of 10 (OD10) or OD0.1. At OD0.1, the distance between the 3 cellulases was greater than that at OD10 in MIX-yeast, but the distance remained the same in ALL-yeast; thus, the difference between the cellulose-degrading activities of ALL-yeast and MIX-yeast increased (to 2.22-fold) at OD0.1, which strongly supports the proximity effect between the displayed cellulases. A proximity effect was also observed for crystalline cellulose (Avicel). We expect the proximity effect to further increase when enzyme display efficiency is enhanced, which would further increase cellulose-degrading activity. This arming yeast technology can also be applied to examine proximity effects in other diverse fields. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  13. Efficacy of beer fermentation residue containing Saccharomyces cerevisiae cells for ameliorating aflatoxicosis in broilers.

    PubMed

    Bovo, F; Franco, L T; Kobashigawa, E; Rottinghaus, G E; Ledoux, D R; Oliveira, C A F

    2015-05-01

    This study aimed to determine the aflatoxin B1 (AFB1) binding capacity of a beer fermentation residue (BFR) containing Saccharomyces cerevisiae cells, and the efficacy of BFR to ameliorate the toxic effects of AFB1 on performance, serum biochemistry, and histology of broilers. The BFR was collected from a microbrewery, and the yeast cells were counted, dried, and milled before it was used in the study. In vitro evaluation of the BFR was conducted using different concentrations of AFB1 (2.0, 4.0, 8.0, 16.0, and 32.0 μg AFB1/mL) and 100 mg/10 mL of BFR at pH 3.0 or 6.0. Two hundred 1-day-old male broilers (Ross 308) were assigned to chick batteries and allowed ad libitum access to feed and water. A completely randomized design was used with 5 replicate pens of 5 chicks assigned to each of 4 dietary treatments from hatch to 21 d, which included: 1) basal diet (BD), with no BFR or AFB1; 2) BD supplemented with 1% BFR; 3) BD supplemented with 2 mg AFB1/kg of feed; and 4) BD supplemented with 2 mg AFB1/kg feed and 1% BFR. Performance variables were determined weekly, while serum analyses were performed on d 14 and 21. At the end of the study, chicks were anesthetized with carbon dioxide, euthanized by cervical dislocation, and the kidney, liver, and bursa of Fabricius were removed for determination of relative weights, and for histological evaluation. In vitro assays showed that the higher the initial AFB1 concentration in solution, the greater the AFB1 amount adsorbed by BFR at both pHs tested. Feed intake, BW gain, and concentrations of albumin, total protein, and globulin increased (P < 0.05) in broilers fed BFR+AFB1 (Diet 4), when compared to the birds receiving only AFB1 (Diet 2). Although BFR was not able to reduce or prevent the effects of AFB1 on relative weights of kidneys and liver, it reduced the severity of histological changes in the liver and kidney caused by AFB1.

  14. Interactions of Condensed Tannins with Saccharomyces cerevisiae Yeast Cells and Cell Walls: Tannin Location by Microscopy.

    PubMed

    Mekoue Nguela, Julie; Vernhet, Aude; Sieczkowski, Nathalie; Brillouet, Jean-Marc

    2015-09-02

    Interactions between grape tannins/red wine polyphenols and yeast cells/cell walls was previously studied within the framework of red wine aging and the use of yeast-derived products as an alternative to aging on lees. Results evidenced a quite different behavior between whole cells (biomass grown to elaborate yeast-derived products, inactivated yeast, and yeast inactivated after autolysis) and yeast cell walls (obtained from mechanical disruption of the biomass). Briefly, whole cells exhibited a high capacity to irreversibly adsorb grape and wine tannins, whereas only weak interactions were observed for cell walls. This last point was quite unexpected considering the literature and called into question the real role of cell walls in yeasts' ability to fix tannins. In the present work, tannin location after interactions between grape and wine tannins and yeast cells and cell walls was studied by means of transmission electron microscopy, light epifluorescence, and confocal microscopy. Microscopy observations evidenced that if tannins interact with cell walls, and especially cell wall mannoproteins, they also diffuse freely through the walls of dead cells to interact with their plasma membrane and cytoplasmic components.

  15. Substrate Degradation Kinetics, Microbial Diversity, and Current Efficiency of Microbial Fuel Cells Supplied with Marine Plankton▿

    PubMed Central

    Reimers, Clare E.; Stecher, Hilmar A.; Westall, John C.; Alleau, Yvan; Howell, Kate A.; Soule, Leslie; White, Helen K.; Girguis, Peter R.

    2007-01-01

    The decomposition of marine plankton in two-chamber, seawater-filled microbial fuel cells (MFCs) has been investigated and related to resulting chemical changes, electrode potentials, current efficiencies, and microbial diversity. Six experiments were run at various discharge potentials, and a seventh served as an open-circuit control. The plankton consisted of a mixture of freshly captured phytoplankton and zooplankton (0.21 to 1 mm) added at an initial batch concentration of 27.5 mmol liter−1 particulate organic carbon (OC). After 56.7 days, between 19.6 and 22.2% of the initial OC remained, sulfate reduction coupled to OC oxidation accounted for the majority of the OC that was degraded, and current efficiencies (of the active MFCs) were between 11.3 and 15.5%. In the open-circuit control cell, anaerobic plankton decomposition (as quantified by the decrease in total OC) could be modeled by three terms: two first-order reaction rate expressions (0.79 day−1 and 0.037 day−1, at 15°C) and one constant, no-reaction term (representing 10.6% of the initial OC). However, in each active MFC, decomposition rates increased during the third week, lagging just behind periods of peak electricity generation. We interpret these decomposition rate changes to have been due primarily to the metabolic activity of sulfur-reducing microorganisms at the anode, a finding consistent with the electrochemical oxidization of sulfide to elemental sulfur and the elimination of inhibitory effects of dissolved sulfide. Representative phylotypes, found to be associated with anodes, were allied with Delta-, Epsilon-, and Gammaproteobacteria as well as the Flavobacterium-Cytophaga-Bacteroides and Fusobacteria. Based upon these results, we posit that higher current efficiencies can be achieved by optimizing plankton-fed MFCs for direct electron transfer from organic matter to electrodes, including microbial precolonization of high-surface-area electrodes and pulsed flowthrough additions of

  16. Recent Advances in Genetic Technique of Microbial Report Cells and Their Applications in Cell Arrays

    PubMed Central

    Kim, Do Hyun; Kim, Moon Il; Park, Hyun Gyu

    2015-01-01

    Microbial cell arrays have attracted consistent attention for their ability to provide unique global data on target analytes at low cost, their capacity for readily detectable and robust cell growth in diverse environments, their high degree of convenience, and their capacity for multiplexing via incorporation of molecularly tailored reporter cells. To highlight recent progress in the field of microbial cell arrays, this review discusses research on genetic engineering of reporter cells, technologies for patterning live cells on solid surfaces, cellular immobilization in different polymers, and studies on their application in environmental monitoring, disease diagnostics, and other related fields. On the basis of these results, we discuss current challenges and future prospects for novel microbial cell arrays, which show promise for use as potent tools for unraveling complex biological processes. PMID:26436087

  17. Effect of Ethanol Stress on Fermentation Performance of Saccharomyces cerevisiae Cells Immobilized on Nypa fruticans Leaf Sheath Pieces

    PubMed Central

    Nguyen, Hoang Phong; Du Le, Hoang

    2015-01-01

    Summary The yeast cells of Saccharomyces cerevisiae immobilized on Nypa fruticans leaf sheath pieces were tested for ethanol tolerance (0, 23.7, 47.4, 71.0 and 94.7 g/L). Increase in the initial ethanol concentration from 23.7 to 94.7 g/L decreased the average growth rate and concentration of ethanol produced by the immobilized yeast by 5.2 and 4.1 times, respectively. However, in the medium with initial ethanol concentration of 94.7 g/L, the average growth rate, glucose uptake rate and ethanol formation rate of the immobilized yeast were 3.7, 2.5 and 3.5 times, respectively, higher than those of the free yeast. The ethanol stress inhibited ethanol formation by Saccharomyces cerevisiae cells and the yeast responded to the stress by changing the fatty acid composition of cellular membrane. The adsorption of yeast cells on Nypa fruticans leaf sheath pieces of the growth medium increased the saturated fatty acid (C16:0 and C18:0) mass fraction in the cellular membrane and that improved alcoholic fermentation performance of the immobilized yeast. PMID:27904338

  18. Correlation of cell growth and heterologous protein production by Saccharomyces cerevisiae.

    PubMed

    Liu, Zihe; Hou, Jin; Martínez, José L; Petranovic, Dina; Nielsen, Jens

    2013-10-01

    With the increasing demand for biopharmaceutical proteins and industrial enzymes, it is necessary to optimize the production by microbial fermentation or cell cultures. Yeasts are well established for the production of a wide range of recombinant proteins, but there are also some limitations; e.g., metabolic and cellular stresses have a strong impact on recombinant protein production. In this work, we investigated the effect of the specific growth rate on the production of two different recombinant proteins. Our results show that human insulin precursor is produced in a growth-associated manner, whereas α-amylase tends to have a higher yield on substrate at low specific growth rates. Based on transcriptional analysis, we found that the difference in the production of the two proteins as function of the specific growth rate is mainly due to differences in endoplasmic reticulum processing, protein turnover, cell cycle, and global stress response. We also found that there is a shift at a specific growth rate of 0.1 h(-1) that influences protein production. Thus, for lower specific growth rates, the α-amylase and insulin precursor-producing strains present similar cell responses and phenotypes, whereas for higher specific growth rates, the two strains respond differently to changes in the specific growth rate.

  19. Display of phytase on the cell surface of Saccharomyces cerevisiae to degrade phytate phosphorus and improve bioethanol production.

    PubMed

    Chen, Xianzhong; Xiao, Yan; Shen, Wei; Govender, Algasan; Zhang, Liang; Fan, You; Wang, Zhengxiang

    2016-03-01

    Currently, development of biofuels as an alternative fuel has gained much attention due to resource and environmental challenges. Bioethanol is one of most important and dominant biofuels, and production using corn or cassava as raw materials has become a prominent technology. However, phytate contained in the raw material not only decreases the efficiency of ethanol production, but also leads to an increase in the discharge of phosphorus, thus impacting on the environment. In this study, to decrease phytate and its phosphorus content in an ethanol fermentation process, Saccharomyces cerevisiae was engineered through a surface-displaying system utilizing the C-terminal half of the yeast α-agglutinin protein. The recombinant yeast strain, PHY, was constructed by successfully displaying phytase on the surface of cells, and enzyme activity reached 6.4 U/g wet biomass weight. Ethanol productions using various strains were compared, and the results demonstrated that the specific growth rate and average fermentation rate of the PHY strain were higher 20 and 18 %, respectively, compared to the control strain S. cerevisiae CICIMY0086, in a 5-L bioreactor process by simultaneous saccharification and fermentation. More importantly, the phytate phosphorus concentration decreased by 89.8 % and free phosphorus concentration increased by 142.9 % in dry vinasse compared to the control in a 5-L bioreactor. In summary, we constructed a recombinant S. cerevisiae strain displaying phytase on the cell surface, which could improve ethanol production performance and effectively reduce the discharge of phosphorus. The strain reported here represents a useful novel engineering platform for developing an environment-friendly system for bioethanol production from a corn substrate.

  20. Decreased cellular permeability to H2O2 protects Saccharomyces cerevisiae cells in stationary phase against oxidative stress.

    PubMed

    Sousa-Lopes, A; Antunes, F; Cyrne, L; Marinho, H S

    2004-12-03

    The higher resistance of stationary-phase Saccharomyces cerevisiae to H2O2 when compared with exponential phase is well characterized, but the molecular mechanisms underlying it remain mostly unknown. By applying the steady-state H2O2-delivery model, we show that (a) cellular permeability to H2O2 is five times lower in stationary--than in exponential phase; (b) cell survival to H2O2 correlates with H2O2 cellular gradients for a variety of cells; and, (c) cells in stationary phase are predicted to be more susceptible to intracellular H2O2 than in exponential phase. In conclusion, limiting H2O2 diffusion into cells is a key protective mechanism against extracellular H2O2.

  1. Crambescidin-816 acts as a fungicidal with more potency than crambescidin-800 and -830, inducing cell cycle arrest, increased cell size and apoptosis in Saccharomyces cerevisiae.

    PubMed

    Rubiolo, Juan A; Ternon, Eva; López-Alonso, Henar; Thomas, Olivier P; Vega, Félix V; Vieytes, Mercedes R; Botana, Luis M

    2013-11-08

    In this paper, we show the effect of crambescidin-816, -800, and -830 on Saccharomyces cerevisiae viability. We determined that, of the three molecules tested, crambescidin-816 was the most potent. Based on this result, we continued by determining the effect of crambescidin-816 on the cell cycle of this yeast. The compound induced cell cycle arrest in G2/M followed by an increase in cell DNA content and size. When the type of cell death was analyzed, we observed that crambescidin-816 induced apoptosis. The antifungal effect indicates that crambescidins, and mostly crambescidin-816, could serve as a lead compound to fight fungal infections.

  2. Sustainable wastewater treatment: how might microbial fuel cells contribute.

    PubMed

    Oh, Sung T; Kim, Jung Rae; Premier, Giuliano C; Lee, Tae Ho; Kim, Changwon; Sloan, William T

    2010-01-01

    The need for cost-effective low-energy wastewater treatment has never been greater. Clean water for our expanding and predominantly urban global population will be expensive to deliver, eats into our diminishing carbon-based energy reserves and consequently contributes to green house gases in the atmosphere and climate change. Thus every potential cost and energy cutting measure for wastewater treatment should be explored. Microbial fuel cells (MFCs) could potentially yield such savings but, to achieve this, requires significant advances in our understanding in a few critical areas and in our designs of the overall systems. Here we review the research which might accelerate our progress towards sustainable wastewater treatment using MFCs: system control and modelling and the understanding of the ecology of the microbial communities that catalyse the generation of electricity.

  3. Recent Progress of Nanostructure Modified Anodes in Microbial Fuel Cells.

    PubMed

    Kim, Marie; Kim, Hyeon Woo; Nam, Joo-Youn; In, Su-Il

    2015-09-01

    Microbial fuel cell (MFC) is a bio-electrochemical system which converts chemical energy into electrical energy by catalytic activity of microorganisms. Electrons produced by microbial oxidation from substrates such as organic matter, complex or renewable biomass are transferred to the anode. Protons produced at the anode migrate to the cathode via the wire and combine with oxygen to form water. Therefore MFC technologies are promising approach for generating electricity or hydrogen gas and wastewater treatment. Electrode materials are one of the keys to increase the power output of MFCs. To improve the cost effective performance of MFCs, various electrodes materials, modifications and configurations have been developed. In this paper, among other recent advances of nanostructured electrodes, especially carbon based anodes, are highlighted. The properties of these electrodes, in terms of surface characteristics, conductivity, modifications, and options were reviewed. The applications, challenges and perspectives of the current MFCs electrode for future development in bio or medical field are briefly discussed.

  4. Perchlorate reduction in microbial electrolysis cell with polyaniline modified cathode.

    PubMed

    Li, Jia-Jia; Gao, Ming-Ming; Zhang, Gang; Wang, Xin-Hua; Wang, Shu-Guang; Song, Chao; Xu, Yan-Yan

    2015-02-01

    Excellent perchlorate reduction was obtained under various initial concentrations in a non-membrane microbial electrolysis cell with polyaniline (PANI) modified graphite cathode as sole electron donor. PANI modification is conducive to the formation of biofilm due to its porous structure and good electrocatalytic performance. Compared with cathode without biofilm, over 12% higher reduction rates were acquired in the presence of biocathode. The study demonstrates that, instead of perchlorate reduction, the main contribution of biofilm is involved in facilitate electron transfer from cathode to electrolyte. Interestingly, hairlike structure, referred as to pili-like, was observed in the biofilm as well as in the electrolyte. Additionally, the results show that pili were prone to formation under the condition of external electron field as sole electron donor. Analysis of microbial community suggests that perchlorate reduction bacteria community was most consistent with Azospiraoryzae strain DSM 13638 in the subdivision of the class Proteobacteria.

  5. A hybrid biocathode: surface display of O2-reducing enzymes for microbial fuel cell applications.

    PubMed

    Szczupak, Alon; Kol-Kalman, Dan; Alfonta, Lital

    2012-01-04

    Laccase and bilirubin oxidase were successfully displayed on the surface of yeast cells. Subsequently, these modified yeast cells were used in the cathode compartment of a microbial fuel cell. The performance of the fuel cells is compared.

  6. Mating type-specific cell-cell recognition of Saccharomyces cerevisiae: cell wall attachment and active sites of a- and alpha-agglutinin.

    PubMed Central

    Cappellaro, C; Baldermann, C; Rachel, R; Tanner, W

    1994-01-01

    Mating type-specific agglutination of Saccharomyces cerevisiae a and alpha cells depends on the heterophilic interaction of two cell surface glycoproteins, the gene products of AG alpha 1 and AGA2. Evidence is presented with immunogold labelling that the alpha-agglutinin is part of the outer fimbrial cell wall coat. The a-agglutinin is bound via two S-S bridges (Cys7 and Cys50) to a cell wall component, most probably the gene product of AGA1. His273 of alpha-agglutinin has previously been shown to be essential for a- and alpha-agglutinin interaction and a model based on two opposing ion-pairs had been proposed. By site-directed mutagenesis this possibility has now been excluded. With the help of various peptides, either chemically synthesized, obtained by proteolysis of intact glycosylated a-agglutinin or prepared from a fusion protein expressed in Escherichia coli, the biologically active region of a-agglutinin was located at the C-terminus of the molecule. A peptide consisting of the C-terminal 10 amino acids (GSPIN-TQYVF) was active in nanomolar concentrations. Saccharide moieties, therefore, are not essential for the mating type-specific cell-cell interaction; glycosylated peptides are, however, four to five times more active than non-glycosylated ones. Comparisons of the recognition sequences of the S. cerevisiae agglutinins with that of the Dictyostelium contact site A glycoprotein (gp80), as well as with those of the various families of cell adhesion molecules of higher eucaryotes, have been made and are discussed. Images PMID:7957044

  7. Influences of dissolved oxygen concentration on biocathodic microbial communities in microbial fuel cells.

    PubMed

    Rago, Laura; Cristiani, Pierangela; Villa, Federica; Zecchin, Sarah; Colombo, Alessandra; Cavalca, Lucia; Schievano, Andrea

    2017-08-01

    Dissolved oxygen (DO) at cathodic interface is a critical factor influencing microbial fuel cells (MFC) performance. In this work, three MFCs were operated with cathode under different DO conditions: i) air-breathing (A-MFC); ii) water-submerged (W-MFC) and iii) assisted by photosynthetic microorganisms (P-MFC). A plateau of maximum current was reached at 1.06±0.03mA, 1.48±0.06mA and 1.66±0.04mA, increasing respectively for W-MFC, P-MFC and A-MFC. Electrochemical and microbiological tools (Illumina sequencing, confocal microscopy and biofilm cryosectioning) were used to explore anodic and cathodic biofilm in each MFC type. In all cases, biocathodes improved oxygen reduction reaction (ORR) as compared to abiotic condition and A-MFC was the best performing system. Photosynthetic cultures in the cathodic chamber supplied high DO level, up to 16mgO2L(-1), which sustained aerobic microbial community in P-MFC biocathode. Halomonas, Pseudomonas and other microaerophilic genera reached >50% of the total OTUs. The presence of sulfur reducing bacteria (Desulfuromonas) and purple non-sulfur bacteria in A-MFC biocathode suggested that the recirculation of sulfur compounds could shuttle electrons to sustain the reduction of oxygen as final electron acceptor. The low DO concentration limited the cathode in W-MFC. A model of two different possible microbial mechanisms is proposed which can drive predominantly cathodic ORR. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Energy generation by fermentation of glucose in a batch flow microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Badea, Silviu-Laurentiu; Enache, Stanica; Tamaian, Radu; Buga, Mihaela-Ramona; Pirvu, Cristian; Varlam, Mihai

    2016-04-01

    In the last years, microbial fuel cells (MFCs) have emerged like a novel research technologies for production of sustainable and clean electricity energy through bioxidation of organic materials, representing a promising alternative to combustion energy sources. In this study, production of bioelectricity in MFC in batch system (dual chambered MFC) was investigated. A dual chambered MFC from glass was built for this purpose. Saccharomyces cerevisiae as an active biocatalyst was explored for power generation. Graphite plates were used as electrodes and glucose as substrate. Saccharomyces cerevisiae was initially grown on a period of 72h at 30 degree Celsius, on medium of modified Sabouraud liquid medium containing 30 g glucose/L. A volume of inoculated medium (80 mL) was transferred in the anode compartment of MFC together with 20 mL glucose 1M, while neutral red was used as mediator (electron shuttle) in concentration of 200 μM in anaerobic anode chamber. Potassium permanganate (KMnO4) was used as oxidizing agent in the cathode in wide concentration range (400 μM-40 000 μM). Cathodic compartment was loaded initially with 40 mM potassium permanganate, and afterwards was supplied two times more with KMnO4 of the same concentration, in order to maintain MFC functionality. The MFC was operated on a water bath heated by a combined hot-plate magnetic-stirrer device at 30 degree Celsius and mixed at 180 rpm. The maximum open circuit potential (OCV) recorded of about 0.6 V was reached after the 3rd loading with 40 milimolles of potassium permanganate. Using a potentiostat, the polarization curve was recorded by varying the potential between 0.5 V and 0.0 V, while the intensity of current increased from 0.0 to about 1.5 mA respectively, corresponding to an anodic current density of about 0.81 A/m2. In order to optimize the design and performance of the MFC, the goal of the further research is to use variously concentrations of potassium permanganate. Furthermore, a dual

  9. Molecular Analysis of the Candida albicans Homolog of Saccharomyces cerevisiae MNN9, Required for Glycosylation of Cell Wall Mannoproteins

    PubMed Central

    Southard, Susan B.; Specht, Charles A.; Mishra, Chitra; Chen-Weiner, Joan; Robbins, Phillips W.

    1999-01-01

    The fungal cell wall has generated interest as a potential target for developing antifungal drugs, and the genes encoding glucan and chitin in fungal pathogens have been studied to this end. Mannoproteins, the third major component of the cell wall, contain mannose in either O- or N-glycosidic linkages. Here we describe the molecular analysis of the Candida albicans homolog of Saccharomyces cerevisiae MNN9, a gene required for the synthesis of N-linked outer-chain mannan in yeast, and the phenotypes associated with its disruption. CaMNN9 has significant homology with S. cerevisiae MNN9, including a putative N-terminal transmembrane domain, and represents a member of a similar gene family in Candida. CaMNN9 resides on chromosome 3 and is expressed at similar levels in both yeast and hyphal cells. Disruption of both copies of CaMNN9 leads to phenotypic effects characteristic of cell wall defects including poor growth in liquid media and on solid media, formation of aggregates in liquid culture, osmotic sensitivity, aberrant hyphal formation, and increased sensitivity to lysis after treatment with β-1,3-glucanase. Like all members of the S. cerevisiae MNN9 gene family the Camnn9Δ strain is resistant to sodium orthovanadate and sensitive to hygromycin B. Analysis of cell wall-associated carbohydrates showed the Camnn9Δ strain to contain half the amount of mannan present in cell walls derived from the wild-type parent strain. Reverse transcription-PCR and Northern analysis of the expression of MNN9 gene family members CaVAN1 and CaANP1 in the Camnn9Δ strain showed that transcription of those genes is not affected in the absence of CaMNN9 transcription. Our results suggest that, while the role MNN9 plays in glycosylation in both Candida and Saccharomyces is conserved, loss of MNN9 function in C. albicans leads to phenotypes that are inconsistent with the pathogenicity of the organism and thus identify CaMnn9p as a potential drug target. PMID:10601199

  10. Engineering microbial fuels cells: recent patents and new directions.

    PubMed

    Biffinger, Justin C; Ringeisen, Bradley R

    2008-01-01

    Fundamental research into how microbes generate electricity within microbial fuel cells (MFCs) has far outweighed the practical application and large scale development of microbial energy harvesting devices. MFCs are considered alternatives to standard commercial polymer electrolyte membrane (PEM) fuel cell technology because the fuel supply does not need to be purified, ambient operating temperatures are maintained with biologically compatible materials, and the biological catalyst is self-regenerating. The generation of electricity during wastewater treatment using MFCs may profoundly affect the approach to anaerobic treatment technologies used in wastewater treatment as a result of developing this energy harvesting technology. However, the materials and engineering designs for MFCs were identical to commercial fuel cells until 2003. Compared to commercial fuel cells, MFCs will remain underdeveloped as long as low power densities are generated from the best systems. The variety of designs for MFCs has expanded rapidly in the last five years in the literature, but the patent protection has lagged behind. This review will cover recent and important patents relating to MFC designs and progress.

  11. Osteoprotegerin Regulates Pancreatic β-Cell Homeostasis upon Microbial Invasion

    PubMed Central

    Kuroda, Yukiko; Maruyama, Kenta; Fujii, Hideki; Sugawara, Isamu; Ko, Shigeru B. H.; Yasuda, Hisataka; Matsui, Hidenori; Matsuo, Koichi

    2016-01-01

    Osteoprotegerin (OPG), a decoy receptor for receptor activator of NF-κB ligand (RANKL), antagonizes RANKL’s osteoclastogenic function in bone. We previously demonstrated that systemic administration of lipopolysaccharide (LPS) to mice elevates OPG levels and reduces RANKL levels in peripheral blood. Here, we show that mice infected with Salmonella, Staphylococcus, Mycobacteria or influenza virus also show elevated serum OPG levels. We then asked whether OPG upregulation following microbial invasion had an effect outside of bone. To do so, we treated mice with LPS and observed OPG production in pancreas, especially in β-cells of pancreatic islets. Insulin release following LPS administration was enhanced in mice lacking OPG, suggesting that OPG inhibits insulin secretion under acute inflammatory conditions. Consistently, treatment of MIN6 pancreatic β-cells with OPG decreased their insulin secretion following glucose stimulation in the presence of LPS. Finally, our findings suggest that LPS-induced OPG upregulation is mediated in part by activator protein (AP)-1 family transcription factors, particularly Fos proteins. Overall, we report that acute microbial infection elevates serum OPG, which maintains β-cell homeostasis by restricting glucose-stimulated insulin secretion, possibly preventing microbe-induced exhaustion of β-cell secretory capacity. PMID:26751951

  12. Design and development of synthetic microbial platform cells for bioenergy.

    PubMed

    Lee, Sang Jun; Lee, Sang-Jae; Lee, Dong-Woo

    2013-01-01

    The finite reservation of fossil fuels accelerates the necessity of development of renewable energy sources. Recent advances in synthetic biology encompassing systems biology and metabolic engineering enable us to engineer and/or create tailor made microorganisms to produce alternative biofuels for the future bio-era. For the efficient transformation of biomass to bioenergy, microbial cells need to be designed and engineered to maximize the performance of cellular metabolisms for the production of biofuels during energy flow. Toward this end, two different conceptual approaches have been applied for the development of platform cell factories: forward minimization and reverse engineering. From the context of naturally minimized genomes,non-essential energy-consuming pathways and/or related gene clusters could be progressively deleted to optimize cellular energy status for bioenergy production. Alternatively, incorporation of non-indigenous parts and/or modules including biomass-degrading enzymes, carbon uptake transporters, photosynthesis, CO2 fixation, and etc. into chassis microorganisms allows the platform cells to gain novel metabolic functions for bioenergy. This review focuses on the current progress in synthetic biology-aided pathway engineering in microbial cells and discusses its impact on the production of sustainable bioenergy.

  13. Design and development of synthetic microbial platform cells for bioenergy

    PubMed Central

    Lee, Sang Jun; Lee, Sang-Jae; Lee, Dong-Woo

    2013-01-01

    The finite reservation of fossil fuels accelerates the necessity of development of renewable energy sources. Recent advances in synthetic biology encompassing systems biology and metabolic engineering enable us to engineer and/or create tailor made microorganisms to produce alternative biofuels for the future bio-era. For the efficient transformation of biomass to bioenergy, microbial cells need to be designed and engineered to maximize the performance of cellular metabolisms for the production of biofuels during energy flow. Toward this end, two different conceptual approaches have been applied for the development of platform cell factories: forward minimization and reverse engineering. From the context of naturally minimized genomes,non-essential energy-consuming pathways and/or related gene clusters could be progressively deleted to optimize cellular energy status for bioenergy production. Alternatively, incorporation of non-indigenous parts and/or modules including biomass-degrading enzymes, carbon uptake transporters, photosynthesis, CO2 fixation, and etc. into chassis microorganisms allows the platform cells to gain novel metabolic functions for bioenergy. This review focuses on the current progress in synthetic biology-aided pathway engineering in microbial cells and discusses its impact on the production of sustainable bioenergy. PMID:23626588

  14. Microbial electricity generation in rice paddy fields: recent advances and perspectives in rhizosphere microbial fuel cells.

    PubMed

    Kouzuma, Atsushi; Kaku, Nobuo; Watanabe, Kazuya

    2014-12-01

    Microbial fuel cells (MFCs) are devices that use living microbes for the conversion of organic matter into electricity. MFC systems can be applied to the generation of electricity at water/sediment interfaces in the environment, such as bay areas, wetlands, and rice paddy fields. Using these systems, electricity generation in paddy fields as high as ∼80 mW m(-2) (based on the projected anode area) has been demonstrated, and evidence suggests that rhizosphere microbes preferentially utilize organic exudates from rice roots for generating electricity. Phylogenetic and metagenomic analyses have been conducted to identify the microbial species and catabolic pathways that are involved in the conversion of root exudates into electricity, suggesting the importance of syntrophic interactions. In parallel, pot cultures of rice and other aquatic plants have been used for rhizosphere MFC experiments under controlled laboratory conditions. The findings from these studies have demonstrated the potential of electricity generation for mitigating methane emission from the rhizosphere. Notably, however, the presence of large amounts of organics in the rhizosphere drastically reduces the effect of electricity generation on methane production. Further studies are necessary to evaluate the potential of these systems for mitigating methane emission from rice paddy fields. We suggest that paddy-field MFCs represent a promising approach for harvesting latent energy of the natural world.

  15. Comparative analysis of microbial community between different cathode systems of microbial fuel cells for denitrification.

    PubMed

    Li, Chao; Xu, Ming; Lu, Yi; Fang, Fang; Cao, Jiashun

    2016-01-01

    Two types of cathodic biofilm in microbial fuel cells (MFC) were established for comparison on their performance and microbial communities. Complete autotrophic simultaneous nitrification and denitrification (SND) without organics addition was achieved in nitrifying-MFC (N-MFC) with a total nitrogen (TN) removal rate of 0.35 mg/(L·h), which was even higher than that in denitrifying-MFC (D-MFC) at same TN level. Integrated denaturing gradient gel electrophoresis analysis based on both 16S rRNA and nirK genes showed that Alpha-, Gammaproteobacteria were the main denitrifier communities. Some potential autotrophic denitrifying bacteria which can use electrons and reducing power from cathodes, such as Shewanella oneidensis, Shewanella loihica, Pseudomonas aeruginosa, Starkeya novella and Rhodopseudomonas palustris were identified and selectively enriched on cathode biofilms. Further, relative abundance of denitrifying bacteria characterized by nirK/16S ratios was much higher in biofilm than suspended sludge according to real-time polymerase chain reaction. The highest enrichment efficiency for denitrifiers was obtained in N-MFC cathode biofilms, which confirmed autotrophic denitrifying bacteria enrichment is the key factor for a D-MFC system.

  16. Performance and microbial ecology of air-cathode microbial fuel cells with layered electrode assemblies.

    PubMed

    Butler, Caitlyn S; Nerenberg, Robert

    2010-05-01

    Microbial fuel cells (MFCs) can be built with layered electrode assemblies, where the anode, proton exchange membrane (PEM), and cathode are pressed into a single unit. We studied the performance and microbial community structure of MFCs with layered assemblies, addressing the effect of materials and oxygen crossover on the community structure. Four MFCs with layered assemblies were constructed using Nafion or Ultrex PEMs and a plain carbon cloth electrode or a cathode with an oxygen-resistant polytetrafluoroethylene diffusion layer. The MFC with Nafion PEM and cathode diffusion layer achieved the highest power density, 381 mW/m(2) (20 W/m(3)). The rates of oxygen diffusion from cathode to anode were three times higher in the MFCs with plain cathodes compared to those with diffusion-layer cathodes. Microsensor studies revealed little accumulation of oxygen within the anode cloth. However, the abundance of bacteria known to use oxygen as an electron acceptor, but not known to have exoelectrogenic activity, was greater in MFCs with plain cathodes. The MFCs with diffusion-layer cathodes had high abundance of exoelectrogenic bacteria within the genus Geobacter. This work suggests that cathode materials can significantly influence oxygen crossover and the relative abundance of exoelectrogenic bacteria on the anode, while PEM materials have little influence on anode community structure. Our results show that oxygen crossover can significantly decrease the performance of air-cathode MFCs with layered assemblies, and therefore limiting crossover may be of particular importance for these types of MFCs.

  17. Ammonia inhibition and microbial adaptation in continuous single-chamber microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Woo; Nam, Joo-Youn; Shin, Hang-Sik

    2011-08-01

    Here, we report that a continuous single-chamber microbial fuel cell (MFC) is applicable to wastewaters containing a high nitrogen concentration using a process of adaptation. Continuous experiments are conducted to investigate the inhibitory effect of total ammonia nitrogen (TAN) on the MFC using influents with various concentrations of TAN ranged from 84 to 10,000 mg N L-1. As the TAN concentration increases up to 3500 mg N L-1, the maximum power density remains at 6.1 W m-3. However, as the concentration further increases, TAN significantly inhibits the maximum power density, which is reduced at saturation to 1.4 W m-3 at 10,000 mg N L-1. We confirm that the adapted electrical performance of a continuous MFC can generate approximately 44% higher power density than the conductivity control. A comparative study reveals that the power densities obtained from a continuous MFC can sustain 7-fold higher TAN concentration than that of previous batch MFCs. TAN removal efficiencies are limited to less than 10%, whereas acetate removal efficiencies remain as high as 93-99%. The increased threshold TAN of the continuous MFC suggests that microbial acclimation in a continuous MFC can allow the electrochemical functioning of the anode-attached bacteria to resist ammonia inhibition.

  18. Vacuolar H+-ATPase Protects Saccharomyces cerevisiae Cells against Ethanol-Induced Oxidative and Cell Wall Stresses

    PubMed Central

    Charoenbhakdi, Sirikarn; Dokpikul, Thanittra; Burphan, Thanawat; Techo, Todsapol

    2016-01-01

    ABSTRACT During fermentation, increased ethanol concentration is a major stress for yeast cells. Vacuolar H+-ATPase (V-ATPase), which plays an important role in the maintenance of intracellular pH homeostasis through vacuolar acidification, has been shown to be required for tolerance to straight-chain alcohols, including ethanol. Since ethanol is known to increase membrane permeability to protons, which then promotes intracellular acidification, it is possible that the V-ATPase is required for recovery from alcohol-induced intracellular acidification. In this study, we show that the effects of straight-chain alcohols on membrane permeabilization and acidification of the cytosol and vacuole are strongly dependent on their lipophilicity. These findings suggest that the membrane-permeabilizing effect of straight-chain alcohols induces cytosolic and vacuolar acidification in a lipophilicity-dependent manner. Surprisingly, after ethanol challenge, the cytosolic pH in Δvma2 and Δvma3 mutants lacking V-ATPase activity was similar to that of the wild-type strain. It is therefore unlikely that the ethanol-sensitive phenotype of vma mutants resulted from severe cytosolic acidification. Interestingly, the vma mutants exposed to ethanol exhibited a delay in cell wall remodeling and a significant increase in intracellular reactive oxygen species (ROS). These findings suggest a role for V-ATPase in the regulation of the cell wall stress response and the prevention of endogenous oxidative stress in response to ethanol. IMPORTANCE The yeast Saccharomyces cerevisiae has been widely used in the alcoholic fermentation industry. Among the environmental stresses that yeast cells encounter during the process of alcoholic fermentation, ethanol is a major stress factor that inhibits yeast growth and viability, eventually leading to fermentation arrest. This study provides evidence for the molecular mechanisms of ethanol tolerance, which is a desirable characteristic for yeast strains

  19. Vacuolar H+-ATPase Protects Saccharomyces cerevisiae Cells against Ethanol-Induced Oxidative and Cell Wall Stresses.

    PubMed

    Charoenbhakdi, Sirikarn; Dokpikul, Thanittra; Burphan, Thanawat; Techo, Todsapol; Auesukaree, Choowong

    2016-05-15

    During fermentation, increased ethanol concentration is a major stress for yeast cells. Vacuolar H(+)-ATPase (V-ATPase), which plays an important role in the maintenance of intracellular pH homeostasis through vacuolar acidification, has been shown to be required for tolerance to straight-chain alcohols, including ethanol. Since ethanol is known to increase membrane permeability to protons, which then promotes intracellular acidification, it is possible that the V-ATPase is required for recovery from alcohol-induced intracellular acidification. In this study, we show that the effects of straight-chain alcohols on membrane permeabilization and acidification of the cytosol and vacuole are strongly dependent on their lipophilicity. These findings suggest that the membrane-permeabilizing effect of straight-chain alcohols induces cytosolic and vacuolar acidification in a lipophilicity-dependent manner. Surprisingly, after ethanol challenge, the cytosolic pH in Δvma2 and Δvma3 mutants lacking V-ATPase activity was similar to that of the wild-type strain. It is therefore unlikely that the ethanol-sensitive phenotype of vma mutants resulted from severe cytosolic acidification. Interestingly, the vma mutants exposed to ethanol exhibited a delay in cell wall remodeling and a significant increase in intracellular reactive oxygen species (ROS). These findings suggest a role for V-ATPase in the regulation of the cell wall stress response and the prevention of endogenous oxidative stress in response to ethanol. The yeast Saccharomyces cerevisiae has been widely used in the alcoholic fermentation industry. Among the environmental stresses that yeast cells encounter during the process of alcoholic fermentation, ethanol is a major stress factor that inhibits yeast growth and viability, eventually leading to fermentation arrest. This study provides evidence for the molecular mechanisms of ethanol tolerance, which is a desirable characteristic for yeast strains used in alcoholic

  20. Size and Carbon Content of Sub-seafloor Microbial Cells

    NASA Astrophysics Data System (ADS)

    Braun, S.; Morono, Y.; Littmann, S.; Jørgensen, B. B.; Lomstein, B. A.

    2015-12-01

    Into the seafloor, a radical decline in nutrient and energy availability poses strong metabolic demands to any residing life. However, a sedimentary microbial ecosystem seems to maintain itself close to what we understand to be the energetic limit of life. Since a complex sediment matrix is interfering with the analysis of whole cells and sub-cellular compounds such as cell wall and membrane molecules, little is known about the physiological properties of cells in the deep biosphere. Here we focus on the size and carbon content of cells from a 90-m sediment drill core retrieved in October 2013 at Landsort Deep, Baltic Sea, in 437 meters water depth. To determine their shape and volume, cells were separated from the sediment matrix by multi-layer density centrifugation and visualized via fluorescence microscopy (FM), scanning electron microscopy (SEM), and stimulated emission depletion microscopy (STED). Total cell-carbon was calculated from amino acid-carbon, which was analyzed by high-performance liquid chromatography after cells had additionally been purified by fluorescence activated cell sorting (FACS). Cell-carbon turnover times were estimated using an amino acid racemization model that is based on the built-in molecular clock of aspartic acid, which due to racemization alternates between the D- and L-isomeric configurations over timescales of thousands of years at low in-situ temperatures (≈4˚C). We find that the majority of microbial cells in the sediment have coccoid or rod-shaped morphology, and that absolute values for cell volume are strongly dependent on the method used, spanning three orders of magnitude from approximately 0.001 to 1 µm3 for both coccoid and rod-shaped cells. From the surface to the deepest sample measured (≈60 mbsf), cell volume decreases by an order of magnitude, and carbon content is in the lower range (<20 fg C cell-1) of what has been reported in the literature as conversion factors. Cell-carbon is turned over approximately

  1. High power density yeast catalyzed microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Ganguli, Rahul

    Microbial fuel cells leverage whole cell biocatalysis to convert the energy stored in energy-rich renewable biomolecules such as sugar, directly to electrical energy at high efficiencies. Advantages of the process include ambient temperature operation, operation in natural streams such as wastewater without the need to clean electrodes, minimal balance-of-plant requirements compared to conventional fuel cells, and environmentally friendly operation. These make the technology very attractive as portable power sources and waste-to-energy converters. The principal problem facing the technology is the low power densities compared to other conventional portable power sources such as batteries and traditional fuel cells. In this work we examined the yeast catalyzed microbial fuel cell and developed methods to increase the power density from such fuel cells. A combination of cyclic voltammetry and optical absorption measurements were used to establish significant adsorption of electron mediators by the microbes. Mediator adsorption was demonstrated to be an important limitation in achieving high power densities in yeast-catalyzed microbial fuel cells. Specifically, the power densities are low for the length of time mediator adsorption continues to occur. Once the mediator adsorption stops, the power densities increase. Rotating disk chronoamperometry was used to extract reaction rate information, and a simple kinetic expression was developed for the current observed in the anodic half-cell. Since the rate expression showed that the current was directly related to microbe concentration close to the electrode, methods to increase cell mass attached to the anode was investigated. Electrically biased electrodes were demonstrated to develop biofilm-like layers of the Baker's yeast with a high concentration of cells directly connected to the electrode. The increased cell mass did increase the power density 2 times compared to a non biofilm fuel cell, but the power density

  2. β-Galactomannan and Saccharomyces cerevisiae var. boulardii modulate the immune response against Salmonella enterica serovar Typhimurium in porcine intestinal epithelial and dendritic cells.

    PubMed

    Badia, Roger; Brufau, M Teresa; Guerrero-Zamora, Ana Maria; Lizardo, Rosil; Dobrescu, Irina; Martin-Venegas, Raquel; Ferrer, Ruth; Salmon, Henri; Martínez, Paz; Brufau, Joaquim

    2012-03-01

    Salmonella enterica serovar Typhimurium is a facultative intracellular pathogen that causes inflammation, necrosis, and diarrhea in pigs, as well as being an important source of food-borne diseases in humans. Probiotics and prebiotics are promising alternatives to antibiotics to control and prevent intestinal infections. The present work investigated a recently developed β-galactomannan (βGM) prebiotic compared to the proven probiotic Saccharomyces cerevisiae var. boulardii on porcine ileum intestinal epithelial cells (IECs) of the IPI-2I line and monocyte-derived dendritic cells (DCs) cocultured in vitro with Salmonella. We observed that both S. cerevisiae var. boulardii and βGM inhibited the association of Salmonella with IECs in vitro. Our data indicated that βGM has a higher ability than S. cerevisiae var. boulardii to inhibit Salmonella-induced proinflammatory mRNA (cytokines tumor necrosis factor alpha [TNF-α], interleukin-1α [IL-1α], IL-6, and granulocyte-macrophage colony-stimulating factor [GM-CSF] and chemokines CCL2, CCL20, and CXCL8) and at protein levels (IL-6 and CXCL8). Additionally, βGM and S. cerevisiae var. boulardii induced some effects on DCs that were not observed on IECs: βGM and S. cerevisiae var. boulardii showed slight upregulation of mRNA for TNF-α, GM-CSF, and CCR7 receptor on porcine monocyte-derived dendritic cells (DCs). Indeed, the addition of βGM or S. cerevisiae var. boulardii on DCs cocultured with Salmonella showed higher gene expression (mRNA) for TNF-α, GM-CSF, and CXCL8 compared to that of the control with Salmonella. In conclusion, the addition of βGM inhibits Salmonella-induced proinflammatory profiles in IECs but may promote DC activation, although associated molecular mechanisms remain to be elucidated.

  3. β-Galactomannan and Saccharomyces cerevisiae var. boulardii Modulate the Immune Response against Salmonella enterica Serovar Typhimurium in Porcine Intestinal Epithelial and Dendritic Cells

    PubMed Central

    Brufau, M. Teresa; Guerrero-Zamora, Ana Maria; Lizardo, Rosil; Dobrescu, Irina; Martin-Venegas, Raquel; Ferrer, Ruth; Salmon, Henri; Martínez, Paz

    2012-01-01

    Salmonella enterica serovar Typhimurium is a facultative intracellular pathogen that causes inflammation, necrosis, and diarrhea in pigs, as well as being an important source of food-borne diseases in humans. Probiotics and prebiotics are promising alternatives to antibiotics to control and prevent intestinal infections. The present work investigated a recently developed β-galactomannan (βGM) prebiotic compared to the proven probiotic Saccharomyces cerevisiae var. boulardii on porcine ileum intestinal epithelial cells (IECs) of the IPI-2I line and monocyte-derived dendritic cells (DCs) cocultured in vitro with Salmonella. We observed that both S. cerevisiae var. boulardii and βGM inhibited the association of Salmonella with IECs in vitro. Our data indicated that βGM has a higher ability than S. cerevisiae var. boulardii to inhibit Salmonella-induced proinflammatory mRNA (cytokines tumor necrosis factor alpha [TNF-α], interleukin-1α [IL-1α], IL-6, and granulocyte-macrophage colony-stimulating factor [GM-CSF] and chemokines CCL2, CCL20, and CXCL8) and at protein levels (IL-6 and CXCL8). Additionally, βGM and S. cerevisiae var. boulardii induced some effects on DCs that were not observed on IECs: βGM and S. cerevisiae var. boulardii showed slight upregulation of mRNA for TNF-α, GM-CSF, and CCR7 receptor on porcine monocyte-derived dendritic cells (DCs). Indeed, the addition of βGM or S. cerevisiae var. boulardii on DCs cocultured with Salmonella showed higher gene expression (mRNA) for TNF-α, GM-CSF, and CXCL8 compared to that of the control with Salmonella. In conclusion, the addition of βGM inhibits Salmonella-induced proinflammatory profiles in IECs but may promote DC activation, although associated molecular mechanisms remain to be elucidated. PMID:22301691

  4. Deletion of AIF1 but not of YCA1/MCA1 protects Saccharomyces cerevisiae and Candida albicans cells from caspofungin-induced programmed cell death

    PubMed Central

    Chin, Christopher; Donaghey, Faith; Helming, Katherine; McCarthy, Morgan; Rogers, Stephen; Austriaco, Nicanor

    2014-01-01

    Caspofungin was the first member of a new class of antifungals called echinocandins to be approved by a drug regulatory authority. Like the other echinocandins, caspofungin blocks the synthesis of β(1,3)-D-glucan of the fungal cell wall by inhibiting the enzyme, β(1,3)-D-glucan synthase. Loss of β(1,3)-D-glucan leads to osmotic instability and cell death. However, the precise mechanism of cell death associated with the cytotoxicity of caspofungin was unclear. We now provide evidence that Saccharomyces cerevisiae cells cultured in media containing caspofungin manifest the classical hallmarks of programmed cell death (PCD) in yeast, including the generation of reactive oxygen species (ROS), the fragmentation of mitochondria, and the production of DNA strand breaks. Our data also suggests that deleting AIF1 but not YCA1/MCA1 protects S. cerevisiae and Candida albicans from caspofungin-induced cell death. This is not only the first time that AIF1 has been specifically tied to cell death in Candida but also the first time that caspofungin resistance has been linked to the cell death machinery in yeast.

  5. Application of living microbial cells entrapped with synthetic resin prepolymers.

    PubMed

    Fukui, S; Tanaka, A

    1989-12-01

    Living and growing microbial cells were immobilized by entrapping in synthetic resin gels prepared from their prepolymers, and used in the production of various useful substances. The production of the desired metabolites and also both the activity and the stability of the catalytic systems were seriously affected by the physico-chemical properties of the prepolymers, and those of the resin gels subsequently formed, such as gel network, hydrophilicity-hydrophobicity balance and ionic nature, as well as by the type of bioreactors. Hydroxylation of steroids and production of antibiotics, polypeptides and other biologically active substances, and the effects of gel properties on them are discussed as examples.

  6. Microbial solar cells: applying photosynthetic and electrochemically active organisms.

    PubMed

    Strik, David P B T B; Timmers, Ruud A; Helder, Marjolein; Steinbusch, Kirsten J J; Hamelers, Hubertus V M; Buisman, Cees J N

    2011-01-01

    Microbial solar cells (MSCs) are recently developed technologies that utilize solar energy to produce electricity or chemicals. MSCs use photoautotrophic microorganisms or higher plants to harvest solar energy, and use electrochemically active microorganisms in the bioelectrochemical system to generate electrical current. Here, we review the principles and performance of various MSCs in an effort to identify the most promising systems, as well as the bottlenecks and potential solutions, for "real-life" MSC applications. We present an outlook on future applications based on the intrinsic advantages of MSCs, specifically highlighting how these living energy systems can facilitate the development of an electricity-producing green roof.

  7. Multi-population model of a microbial electrolysis cell.

    PubMed

    Pinto, R P; Srinivasan, B; Escapa, A; Tartakovsky, B

    2011-06-01

    This work presents a multi-population dynamic model of a microbial electrolysis cell (MEC). The model describes the growth and metabolic activity of fermentative, electricigenic, methanogenic acetoclastic, and methanogenic hydrogenophilic microorganisms and is capable of simulating hydrogen production in a MEC fed with complex organic matter, such as wastewater. The model parameters were estimated with the experimental results obtained in continuous flow MECs fed with acetate or synthetic wastewater. Following successful model validation with an independent data set, the model was used to analyze and discuss the influence of applied voltage and organic load on hydrogen production and COD removal.

  8. Progress of air-breathing cathode in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Wang, Zejie; Mahadevan, Gurumurthy Dummi; Wu, Yicheng; Zhao, Feng

    2017-07-01

    Microbial fuel cell (MFC) is an emerging technology to produce green energy and vanquish the effects of environmental contaminants. Cathodic reactions are vital for high electrical power density generated from MFCs. Recently tremendous attentions were paid towards developing high performance air-breathing cathodes. A typical air-breathing cathode comprises of electrode substrate, catalyst layer, and air-diffusion layer. Prior researches demonstrated that each component influenced the performance of air-breathing cathode MFCs. This review summarized the progress in development of the individual component and elaborated main factors to the performance of air-breathing cathode.

  9. Microbial fuel cells as pollutant treatment units: Research updates.

    PubMed

    Zhang, Quanguo; Hu, Jianjun; Lee, Duu-Jong

    2016-10-01

    Microbial fuel cells (MFC) are a device that can convert chemical energy in influent substances to electricity via biological pathways. Based on the consent that MFC technology should be applied as a waste/wastewater treatment unit rather than a renewable energy source, this mini-review discussed recent R&D efforts on MFC technologies for pollutant treatments and highlighted the challenges and research and development needs. Owing to the low power density levels achievable by larger-scale MFC, the MFC should be used as a device other than energy source such as being a pollutant treatment unit. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Design of a microbial fuel cell and its transition to microbial electrolytic cell for hydrogen production by electrohydrogenesis.

    PubMed

    Gupta, Pratima; Parkhey, Piyush; Joshi, Komal; Mahilkar, Anjali

    2013-10-01

    Anaerobic bacteria were isolated from industrial wastewater and soil samples and tested for exoelectrogenic activity by current production in double chambered microbial fuel cell (MFC), which was further transitioned into a single chambered microbial electrolytic cell to test hydrogen production by electrohydrogenesis. Of all the cultures, the isolate from industrial water sample showed the maximum values for current = 0.161 mA, current density = 108.57 mA/m2 and power density = 48.85 mW/m2 with graphite electrode. Maximum voltage across the cell, however, was reported by the isolate from sewage water sample (506 mv) with copper as electrode. Tap water with KMnO4 was the best cathodic electrolyte as the highest values for all the measured MFC parameters were reported with it. Once the exoelectrogenic activity of the isolates was confirmed by current production, these were tested for hydrogen production in a single chambered microbial electrolytic cell (MEC) modified from the MFC. Hydrogen production was reported positive from co-culture of isolates of both the water samples and co-culture of one soil and one water sample. The maximum rate and yield of hydrogen production was 0.18 m3H2/m3/d and 3.2 mol H2/mol glucose respectively with total hydrogen production of 42.4 mL and energy recovery of 57.4%. Cumulative hydrogen production for a five day cycle of MEC operation was 0.16 m3H2/m3/d.

  11. An essential gene, ESR1, is required for mitotic cell growth, DNA repair and meiotic recombination in Saccharomyces cerevisiae.

    PubMed Central

    Kato, R; Ogawa, H

    1994-01-01

    A new mutant, which was sensitive to both methyl-methanesulfonate (MMS) and ultra-violet light (UV) and defective in meiotic recombination, was isolated from Saccharomyces cerevisiae. The gene, ESR1, was cloned by complementation of the MMS sensitivity of the mutant and found to be essential for cell growth, as the deleted haploid strain was lethal. The ESR1 gene was adjacent to the CKS1 gene on chromosome II and encoded a putative 2368-amino acid protein with a molecular weight of 273 k. The ESR1 transcript was 8.0 kb long and was induced during meiosis. The predicted Esr1 protein had a mosaic structure composed of homologous regions and showed amino acid sequence similarities to Schizosaccharomyces pombe rad3+ protein, which monitors completion of DNA repair synthesis, and cut1+ protein, which is required for spindle pole body (SPB) duplication. The Esr1 protein was also similar to phosphatidylinositol (PI) 3-kinases, including Saccharomyces cerevisiae TOR2 (and DRR1), which are involved in G1 progression. These results suggest that ESR1 is multi-functional throughout mitosis and meiosis. Images PMID:8065923

  12. Saccharomyces cerevisiae decreases inflammatory responses induced by F4+ enterotoxigenic Escherichia coli in porcine intestinal epithelial cells.

    PubMed

    Zanello, Galliano; Meurens, François; Berri, Mustapha; Chevaleyre, Claire; Melo, Sandrine; Auclair, Eric; Salmon, Henri

    2011-05-15

    Probiotic yeasts may provide protection against intestinal inflammation induced by enteric pathogens. In piglets, infection with F4+ enterotoxigenic Escherichia coli (ETEC) leads to inflammation, diarrhea and intestinal damage. In this study, we investigated whether the yeast strains Saccharomyces cerevisiae (Sc, strain CNCM I-3856) and S. cerevisiae variety boulardii (Sb, strain CNCM I-3799) decreased the expression of pro-inflammatory cytokines and chemokines in intestinal epithelial IPI-2I cells cultured with F4+ ETEC. Results showed that viable Sc inhibited the ETEC-induced TNF-α gene expression whereas Sb did not. In contrast, killed Sc failed to inhibit the expression of pro-inflammatory genes. This inhibition was dependent on secreted soluble factors. Sc culture supernatant decreased the TNF-α, IL-1α, IL-6, IL-8, CXCL2 and CCL20 ETEC-induced mRNA. Furthermore, Sc culture supernatant filtrated fraction < 10 kDa displayed the same effects excepted for TNF-α. Thus, our results extended to Sc (strain CNCM I-3856) the inhibitory effects of some probiotic yeast strains onto inflammation.

  13. Stacked microbial desalination cells to enhance water desalination efficiency.

    PubMed

    Chen, Xi; Xia, Xue; Liang, Peng; Cao, Xiaoxin; Sun, Haotian; Huang, Xia

    2011-03-15

    Microbial desalination cell (MDC) is a new method to obtain clean water from brackish water using electricity generated from organic matters by exoelectrogenic bacteria. Anions and cations, derived from salt solution filled in the desalination chamber between the anode and cathode, move to the anode and cathode chambers under the force of electrical field, respectively. On the basis of the primitive single-desalination-chambered MDC, stacked microbial desalination cells (SMDCs) were developed in order to promote the desalination rate in the present study. The effects of desalination chamber number and external resistance were investigated. Results showed that a remarkable increase in the total desalination rate (TDR) could be obtained by means of increasing the desalination cell number and reducing the external resistance, which caused the charge transfer efficiency increased since the SMDCs enabled more pairs of ions separated while one electron passed through the external circuit. The maximum TDR of 0.0252 g/h was obtained using a two-desalination-chambered SMDC with an external resistance of 10 Ω, which was 1.4 times that of single-desalination-chambered MDC. SMDCs proved to be an effective approach to increase the total water desalination rate if provided a proper desalination chamber number and external resistance.

  14. Photosynthetic microbial fuel cells with positive light response.

    PubMed

    Zou, Yongjin; Pisciotta, John; Billmyre, R Blake; Baskakov, Ilia V

    2009-12-01

    The current study introduces an aerobic single-chamber photosynthetic microbial fuel cell (PMFC). Evaluation of PMFC performance using naturally growing fresh-water photosynthetic biofilm revealed a weak positive light response, that is, an increase in cell voltage upon illumination. When the PMFC anodes were coated with electrically conductive polymers, the rate of voltage increased and the amplitude of the light response improved significantly. The rapid immediate positive response to light was consistent with a mechanism postulating that the photosynthetic electron-transfer chain is the source of the electrons harvested on the anode surface. This mechanism is fundamentally different from the one exploited in previously designed anaerobic microbial fuel cells (MFCs), sediment MFCs, or anaerobic PMFCs, where the electrons are derived from the respiratory electron-transfer chain. The power densities produced in PMFCs were substantially lower than those that are currently reported for conventional MFC (0.95 mW/m(2) for polyaniline-coated and 1.3 mW/m(2) for polypyrrole-coated anodes). However, the PMFC did not depend on an organic substrate as an energy source and was powered only by light energy. Its operation was CO(2)-neutral and did not require buffers or exogenous electron transfer shuttles.

  15. Environmental sensing of heavy metals through whole cell microbial biosensors: a synthetic biology approach.

    PubMed

    Bereza-Malcolm, Lara Tess; Mann, Gülay; Franks, Ashley Edwin

    2015-05-15

    Whole cell microbial biosensors are offering an alternative means for rapid, on-site heavy metal detection. Based in microorganisms, biosensing constructs are designed and constructed to produce both qualitative and quantitative outputs in response to heavy metal ions. Previous microbial biosensors designs are focused on single-input constructs; however, development of multiplexed systems is resulting in more flexible designs. The movement of microbial biosensors from laboratory based designs toward on-site, functioning heavy metal detectors has been hindered by the toxic nature of heavy metals, along with the lack of specificity of heavy metals promoter elements. Applying a synthetic biology approach with alternative microbial chassis may increase the robustness of microbial biosensors and mitigate these issues. Before full applications are achieved, further consideration has to be made regarding the risk and regulations of whole cell microbial biosensor use in the environment. To this end, a standard framework for future whole cell microbial biosensor design and use is proposed.

  16. Recent Advances in Microbial Single Cell Genomics Technology and Applications

    NASA Astrophysics Data System (ADS)

    Stepanauskas, R.

    2016-02-01

    Single cell genomics is increasingly utilized as a powerful tool to decipher the metabolic potential, evolutionary histories and in situ interactions of environmental microorganisms. This transformative technology recovers extensive information from cultivation-unbiased samples of individual, unicellular organisms. Thus, it does not require data binning into arbitrary phylogenetic or functional groups and therefore is highly compatible with agent-based modeling approaches. I will present several technological advances in this field, which significantly improve genomic data recovery from individual cells and provide direct linkages between cell's genomic and phenotypic properties. I will also demonstrate how these new technical capabilities help understanding the metabolic potential and viral infections of the "microbial dark matter" inhabiting aquatic and subsurface environments.

  17. Characterization of the Cell Surface Properties of Drinking Water Pathogens by Microbial Adhesion to Hydrocarbon and Electrophoretic Mobility Measurements

    EPA Science Inventory

    The surface characteristics of microbial cells directly influence their mobility and behavior within aqueous environments. The cell surface hydrophobicity (CSH) and electrophoretic mobility (EPM) of microbial cells impact a number of interactions and processes including aggregati...

  18. Characterization of the Cell Surface Properties of Drinking Water Pathogens by Microbial Adhesion to Hydrocarbon and Electrophoretic Mobility Measurements

    EPA Science Inventory

    The surface characteristics of microbial cells directly influence their mobility and behavior within aqueous environments. The cell surface hydrophobicity (CSH) and electrophoretic mobility (EPM) of microbial cells impact a number of interactions and processes including aggregati...

  19. Glucose-dependent cell size is regulated by a G protein-coupled receptor system in yeast Saccharomyces cerevisiae.

    PubMed

    Tamaki, Hisanori; Yun, Cheol-Won; Mizutani, Tomohiro; Tsuzuki, Takahiro; Takagi, Yukinobu; Shinozaki, Makiko; Kodama, Yukiko; Shirahige, Katsuhiko; Kumagai, Hidehiko

    2005-03-01

    In the yeast, Saccharomyces cerevisiae, cell size is affected by the kind of carbon source in the medium. Here, we present evidence that the Gpr1 receptor and Gpa2 Galpha subunit are required for both maintenance and modulation of cell size in response to glucose. In the presence of glucose, mutants lacking GPR1 or GPA2 gene showed smaller cells than the wild-type strain. Physiological studies revealed that protein synthesis rate was reduced in the mutant strains indicating that reduced growth rate, while the level of mRNAs for CLN1, 2 and 3 was not affected in all strains. Gene chip analysis also revealed a down-regulation in the expression of genes related to biosynthesis of not only protein but also other cellular component in the mutant strains. We also show that GPR1 and GPA2 are required for a rapid increase in cell size in response to glucose. Wild-type cells grown in ethanol quickly increased in size by addition of glucose, while little change was observed in the mutant strains, in which glucose-dependent cell cycle arrest caused by CLN1 repression was somewhat alleviated. Our study indicates that the yeast G-protein coupled receptor system consisting of Gpr1 and Gpa2 regulates cell size by affecting both growth rate and cell division.

  20. Using S. cerevisiae as a Model System to Investigate V. cholerae VopX-Host Cell Protein Interactions and Phenotypes

    PubMed Central

    Seward, Christopher H.; Manzella, Alexander; Alam, Ashfaqul; Butler, J. Scott; Dziejman, Michelle

    2015-01-01

    Most pathogenic, non-O1/non-O139 serogroup Vibrio cholerae strains cause diarrheal disease in the absence of cholera toxin. Instead, many use Type 3 Secretion System (T3SS) mediated mechanisms to disrupt host cell homeostasis. We identified a T3SS effector protein, VopX, which is translocated into mammalian cells during in vitro co-culture. In a S. cerevisiae model system, we found that expression of VopX resulted in a severe growth defect that was partially suppressed by a deletion of RLM1, encoding the terminal transcriptional regulator of the Cell Wall Integrity MAP kinase (CWI) regulated pathway. Growth of yeast cells in the presence of sorbitol also suppressed the defect, supporting a role for VopX in destabilizing the cell wall. Expression of VopX activated expression of β-galactosidase from an RLM1-reponsive element reporter fusion, but failed to do so in cells lacking MAP kinases upstream of Rlm1. The results suggest that VopX inhibits cell growth by stimulating the CWI pathway through Rlm1. Rlm1 is an ortholog of mammalian MEF2 transcription factors that are proposed to regulate cell differentiation, proliferation, and apoptosis. The collective findings suggest that VopX contributes to disease by activating MAP kinase cascades that elicit changes in cellular transcriptional programs. PMID:26473925

  1. Using S. cerevisiae as a Model System to Investigate V. cholerae VopX-Host Cell Protein Interactions and Phenotypes.

    PubMed

    Seward, Christopher H; Manzella, Alexander; Alam, Ashfaqul; Butler, J Scott; Dziejman, Michelle

    2015-10-14

    Most pathogenic, non-O1/non-O139 serogroup Vibrio cholerae strains cause diarrheal disease in the absence of cholera toxin. Instead, many use Type 3 Secretion System (T3SS) mediated mechanisms to disrupt host cell homeostasis. We identified a T3SS effector protein, VopX, which is translocated into mammalian cells during in vitro co-culture. In a S. cerevisiae model system, we found that expression of VopX resulted in a severe growth defect that was partially suppressed by a deletion of RLM1, encoding the terminal transcriptional regulator of the Cell Wall Integrity MAP kinase (CWI) regulated pathway. Growth of yeast cells in the presence of sorbitol also suppressed the defect, supporting a role for VopX in destabilizing the cell wall. Expression of VopX activated expression of β-galactosidase from an RLM1-reponsive element reporter fusion, but failed to do so in cells lacking MAP kinases upstream of Rlm1. The results suggest that VopX inhibits cell growth by stimulating the CWI pathway through Rlm1. Rlm1 is an ortholog of mammalian MEF2 transcription factors that are proposed to regulate cell differentiation, proliferation, and apoptosis. The collective findings suggest that VopX contributes to disease by activating MAP kinase cascades that elicit changes in cellular transcriptional programs.

  2. The Role of Soil Organic Matter, Nutrients, and Microbial Community Structure on the Performance of Microbial Fuel Cells

    NASA Astrophysics Data System (ADS)

    Rooney-Varga, J. N.; Dunaj, S. J.; Vallino, J. J.; Hines, M. E.; Gay, M.; Kobyljanec, C.

    2011-12-01

    Microbial fuel cells (MFCs) offer the potential for generating electricity, mitigating greenhouse gas emissions, and bioremediating pollutants through utilization of a plentiful, natural, and renewable resource: soil organic carbon. In the current study, we analyzed microbial community structure, MFC performance, and soil characteristics in different microhabitats (bulk soil, anode, and cathode) within MFCs constructed from agricultural or forest soils in order to determine how soil type and microbial dynamics influence MFC performance. MFCs were constructed with soils from agricultural and hardwood forest sites at Harvard Forest (Petersham, MA). The bulk soil characteristics were analyzed, including polyphenols, short chain fatty acids, total organic C and N, abiotic macronutrients, N and P mineralization rates, CO2 respiration rates, and MFC power output. Microbial community structure of the anodes, cathodes, and bulk soils was determined with molecular fingerprinting methods, which included terminal restriction length polymorphism (T-RFLP) analysis and 16S rRNA gene sequencing analysis. Our results indicated that MFCs constructed from agricultural soil had power output about 17 times that of forest soil-based MFCs and respiration rates about 10 times higher than forest soil MFCs. Agricultural soil MFCs had lower C:N ratios, polyphenol content, and acetate concentrations than forest soil MFCs, suggesting that active agricultural MFC microbial communities were supported by higher quality organic carbon. Microbial community profile data indicate that the microbial communities at the anode of the high power MFCs were less diverse than in low power MFCs and were dominated by Deltaproteobacteria, Geobacter, and, to a lesser extent, Clostridia, while low-power MFC anode communities were dominated by Clostridia. These data suggest that the presence of organic carbon substrate (acetate) was not the major limiting factor in selecting for highly electrogenic microbial

  3. Nanoparticle facilitated extracellular electron transfer in microbial fuel cells.

    PubMed

    Jiang, Xiaocheng; Hu, Jinsong; Lieber, Alexander M; Jackan, Charles S; Biffinger, Justin C; Fitzgerald, Lisa A; Ringeisen, Bradley R; Lieber, Charles M

    2014-11-12

    Microbial fuel cells (MFCs) have been the focus of substantial research interest due to their potential for long-term, renewable electrical power generation via the metabolism of a broad spectrum of organic substrates, although the low power densities have limited their applications to date. Here, we demonstrate the potential to improve the power extraction by exploiting biogenic inorganic nanoparticles to facilitate extracellular electron transfer in MFCs. Simultaneous short-circuit current recording and optical imaging on a nanotechnology-enabled platform showed substantial current increase from Shewanella PV-4 after the formation of cell/iron sulfide nanoparticle aggregates. Detailed characterization of the structure and composition of the cell/nanoparticle interface revealed crystalline iron sulfide nanoparticles in intimate contact with and uniformly coating the cell membrane. In addition, studies designed to address the fundamental mechanisms of charge transport in this hybrid system showed that charge transport only occurred in the presence of live Shewanella, and moreover demonstrated that the enhanced current output can be attributed to improved electron transfer at cell/electrode interface and through the cellular-networks. Our approach of interconnecting and electrically contacting bacterial cells through biogenic nanoparticles represents a unique and promising direction in MFC research and has the potential to not only advance our fundamental knowledge about electron transfer processes in these biological systems but also overcome a key limitation in MFCs by constructing an electrically connected, three-dimensional cell network from the bottom-up.

  4. Microbial reverse electrodialysis cells for synergistically enhanced power production.

    PubMed

    Kim, Younggy; Logan, Bruce E

    2011-07-01

    A new type of bioelectrochemical system for producing electrical power, called a microbial reverse-electrodialysis cell (MRC), was developed to increase voltages and power densities compared to those generated individually by microbial fuel cells (MFCs) or reverse electrodialysis (RED) systems. In RED systems, electrode overpotentials create significant energy losses due to thermodynamically unfavorable electrode reactions, and therefore a large number of stacked cells must be used to have significant energy recovery. This results in high capital costs for the large number of membranes, and increases energy losses from pumping water through a large number of cells. In an MRC, high overpotentials are avoided through oxidation of organic matter by exoelectrogenic bacteria on the anode and oxygen reduction on the cathode. An MRC containing only five pairs of RED cells, fed solutions typical of seawater (600 mM NaCl) and river water (12 mM NaCl) at 0.85 mL/min, produced up to 3.6 W/m(2) (cathode surface area) and 1.2-1.3 V with acetate as a substrate. Pumping accounted for <2% of the produced power. A higher flow rate (1.55 mL/min) increased power densities up to 4.3 W/m(2). COD removal was 98% with a Coulombic efficiency of 64%. Power production by the individual components was substantially lower with 0.7 W/m(2) without salinity driven energy, and <0.015 W/m(2) with reduced exoelectrogenic activity due to substrate depletion. These results show that the combination of an MFC and a RED stack synergistically increases performance relative to the individual systems, producing a new type of system that can be used to more efficiently capture salinity driven energy from seawater and river water.

  5. Single-cell analysis of S. cerevisiae growth recovery after a sublethal heat-stress applied during an alcoholic fermentation.

    PubMed

    Tibayrenc, Pierre; Preziosi-Belloy, Laurence; Ghommidh, Charles

    2011-06-01

    Interest in bioethanol production has experienced a resurgence in the last few years. Poor temperature control in industrial fermentation tanks exposes the yeast cells used for this production to intermittent heat stress which impairs fermentation efficiency. Therefore, there is a need for yeast strains with improved tolerance, able to recover from such temperature variations. Accordingly, this paper reports the development of methods for the characterization of Saccharomyces cerevisiae growth recovery after a sublethal heat stress. Single-cell measurements were carried out in order to detect cell-to-cell variability. Alcoholic batch fermentations were performed on a defined medium in a 2 l instrumented bioreactor. A rapid temperature shift from 33 to 43 °C was applied when ethanol concentration reached 50 g l⁻¹. Samples were collected at different times after the temperature shift. Single cell growth capability, lag-time and initial growth rate were determined by monitoring the growth of a statistically significant number of cells after agar medium plating. The rapid temperature shift resulted in an immediate arrest of growth and triggered a progressive loss of cultivability from 100 to 0.0001% within 8 h. Heat-injured cells were able to recover their growth capability on agar medium after a lag phase. Lag-time was longer and more widely distributed as the time of heat exposure increased. Thus, lag-time distribution gives an insight into strain sensitivity to heat-stress, and could be helpful for the selection of yeast strains of technological interest.

  6. Effects of ice-seeding temperature and intracellular trehalose contents on survival of frozen Saccharomyces cerevisiae cells.

    PubMed

    Nakamura, Toshihide; Takagi, Hiroshi; Shima, Jun

    2009-04-01

    Freezing tolerance is an important characteristic for baker's yeast, Saccharomyces cerevisiae, as it is used to make frozen dough. The ability of yeast cells to survive freezing is thought to depend on various factors. The purpose of this work was to study the viability of yeast cells during the freezing process. We examined factors potentially affecting their survival, including the growth phase, ice-seeding temperature, intracellular trehalose content, freezing period, and duration of supercooling. The results showed that the ice-seeding temperature significantly affected cell viability. In the stationary phase, trehalose accumulation did not affect the viability of yeast cells after brief freezing, although it did significantly affect the viability after prolonged freezing. In the log phase, the ice-seeding temperature was more important for cell survival than the presence of trehalose during prolonged freezing. The importance of increasing the extracellular ice-seeding temperature was verified by comparing frozen yeast survival rates in a freezing test with ice-seeding temperatures of -5 degrees C and -15 degrees C. We also found that the cell survival rates began to increase at 3h of supercooling. The yeast cells may adapt to subzero temperatures and/or acquire tolerance to freezing stress during the supercooling.

  7. Cell cycle execution point analysis of ORC function and characterization of the checkpoint response to ORC inactivation in Saccharomyces cerevisiae.

    PubMed

    Gibson, Daniel G; Bell, Stephen P; Aparicio, Oscar M

    2006-06-01

    Chromosomal replication initiates through the assembly of a prereplicative complex (pre-RC) at individual replication origins in the G1-phase, followed by activation of these complexes in the S-phase. In Saccharomyces cerevisiae, the origin recognition complex (ORC) binds replication origins throughout the cell cycle and participates in pre-RC assembly. Whether the ORC plays an additional role subsequent to pre-RC assembly in replication initiation or any other essential cell cycle process is not clear. To study the function of the ORC during defined cell cycle periods, we performed cell cycle execution point analyses with strains containing a conditional mutation in the ORC1, ORC2 or ORC5 subunit of ORC. We found that the ORC is essential for replication initiation, but is dispensable for replication elongation or later cell cycle events. Defective initiation in ORC mutant cells results in incomplete replication and mitotic arrest enforced by the DNA damage and spindle assembly checkpoint pathways. The involvement of the spindle assembly checkpoint implies a defect in kinetochore-spindle attachment or sister chromatid cohesion due to incomplete replication and/or DNA damage. Remarkably, under semipermissive conditions for ORC1 function, the spindle checkpoint alone suffices to block proliferation, suggesting this checkpoint is highly sensitive to replication initiation defects. We discuss the potential significance of these overlapping checkpoints and the impact of our findings on previously postulated role(s) of ORCs in other cell cycle functions.

  8. Construction of a xylan-fermenting yeast strain through codisplay of xylanolytic enzymes on the surface of xylose-utilizing Saccharomyces cerevisiae cells.

    PubMed

    Katahira, Satoshi; Fujita, Yasuya; Mizuike, Atsuko; Fukuda, Hideki; Kondo, Akihiko

    2004-09-01

    Hemicellulose is one of the major forms of biomass in lignocellulose, and its essential component is xylan. We used a cell surface engineering system based on alpha-agglutinin to construct a Saccharomyces cerevisiae yeast strain codisplaying two types of xylan-degrading enzymes, namely, xylanase II (XYNII) from Trichoderma reesei QM9414 and beta-xylosidase (XylA) from Aspergillus oryzae NiaD300, on the cell surface. In a high-performance liquid chromatography analysis, xylose was detected as the main product of the yeast strain codisplaying XYNII and XylA, while xylobiose and xylotriose were detected as the main products of a yeast strain displaying XYNII on the cell surface. These results indicate that xylan is sequentially hydrolyzed to xylose by the codisplayed XYNII and XylA. In a further step toward achieving the simultaneous saccharification and fermentation of xylan, a xylan-utilizing S. cerevisiae strain was constructed by codisplaying XYNII and XylA and introducing genes for xylose utilization, namely, those encoding xylose reductase and xylitol dehydrogenase from Pichia stipitis and xylulokinase from S. cerevisiae. After 62 h of fermentation, 7.1 g of ethanol per liter was directly produced from birchwood xylan, and the yield in terms of grams of ethanol per gram of carbohydrate consumed was 0.30 g/g. These results demonstrate that the direct conversion of xylan to ethanol is accomplished by the xylan-utilizing S. cerevisiae strain.

  9. A mathematical model of Saccharomyces cerevisiae growth in response to cadmium toxicity.

    PubMed

    Hietala, Katie A; Lynch, Miranda L; Allshouse, John C; Johns, Craig J; Roane, Timberley M

    2006-01-01

    Microbial growth can be described using models derived by differential equations, but available mathematical models have yet to adequately describe lag phase related cell growth or cell mortality in response to chemical toxicity. Lag phase cell behavior, however, dictates the onset of exponential growth and the number of actively growing cells available to initiate exponential growth, important factors in the success of remediation efforts. In this study, a five-parameter polynomial ratio (PR) model was used to characterize the growth, from lag through stationary phase, of the yeast Saccharomyces cerevisiae in response to cadmium toxicity. The PR model used in this study has the advantages over standard mathematical models in the ability to represent the initial cell mortality observed when S. cerevisiae is exposed to increasing cadmium levels, up to 12 mg/l Cd, as well as following cell recovery and growth to stationary levels.

  10. Analysis of the microbial community of the biocathode of a hydrogen-producing microbial electrolysis cell.

    PubMed

    Croese, Elsemiek; Pereira, Maria Alcina; Euverink, Gert-Jan W; Stams, Alfons J M; Geelhoed, Jeanine S

    2011-12-01

    The microbial electrolysis cell (MEC) is a promising system for hydrogen production. Still, expensive catalysts such as platinum are needed for efficient hydrogen evolution at the cathode. Recently, the possibility to use a biocathode as an alternative for platinum was shown. The microorganisms involved in hydrogen evolution in such systems are not yet identified. We analyzed the microbial community of a mixed culture biocathode that was enriched in an MEC bioanode. This biocathode produced 1.1 A m(-2) and 0.63 m3 H2 m(-3) cathode liquid volume per day. The bacterial population consisted of 46% Proteobacteria, 25% Firmicutes, 17% Bacteroidetes, and 12% related to other phyla. The dominant ribotype belonged to the species Desulfovibrio vulgaris. The second major ribotype cluster constituted a novel taxonomic group at the genus level, clustering within uncultured Firmicutes. The third cluster belonged to uncultured Bacteroidetes and grouped in a taxonomic group from which only clones were described before; most of these clones originated from soil samples. The identified novel taxonomic groups developed under environmentally unusual conditions, and this may point to properties that have not been considered before. A pure culture of Desulfovibrio strain G11 inoculated in a cathode of an MEC led to a current development from 0.17 to 0.76 A m(-2) in 9 days, and hydrogen gas formation was observed. On the basis of the known characteristics of Desulfovibrio spp., including its ability to produce hydrogen, we propose a mechanism for hydrogen evolution through Desulfovibrio spp. in a biocathode system.

  11. Flow dependent performance of microfluidic microbial fuel cells.

    PubMed

    Vigolo, Daniele; Al-Housseiny, Talal T; Shen, Yi; Akinlawon, Fiyinfoluwa O; Al-Housseiny, Saif T; Hobson, Ronald K; Sahu, Amaresh; Bedkowski, Katherine I; DiChristina, Thomas J; Stone, Howard A

    2014-06-28

    The integration of Microbial Fuel Cells (MFCs) in a microfluidic geometry can significantly enhance the power density of these cells, which would have more active bacteria per unit volume. Moreover, microfluidic MFCs can be operated in a continuous mode as opposed to the traditional batch-fed mode. Here we investigate the effect of fluid flow on the performance of microfluidic MFCs. The growth and the structure of the bacterial biofilm depend to a large extent on the shear stress of the flow. We report the existence of a range of flow rates for which MFCs can achieve maximum voltage output. When operated under these optimal conditions, the power density of our microfluidic MFC is about 15 times that of a similar-size batch MFC. Furthermore, this optimum suggests a correlation between the behaviour of bacteria and fluid flow.

  12. Nitrite as a candidate substrate in microbial fuel cells.

    PubMed

    Faraghi, Neda; Ebrahimi, Sirous

    2012-08-01

    Current generation using nitrite as substrate (pH 6.9, 40 mgN l(-1)) in a nitrite-fed microbial fuel cell was investigated under anaerobic and aerobic anodic conditions as an alternative to the biological nitrite oxidation process. Cell current, coulombic efficiency (CE) and power generation of 0.04 mA, 30 ± 2 % and 19.3 ± 3.3 μW m(-2), respectively, were observed under anaerobic conditions while complete nitrite degradation (no current) was obtained under aerobic conditions. Switching from aerobic to anaerobic anode enhanced the CE and power generation (39 ± 1 % and 29 ± 4.3 μW m(-2)).

  13. Monitoring microbial population dynamics at low densities

    NASA Astrophysics Data System (ADS)

    Julou, Thomas; Desprat, Nicolas; Bensimon, David; Croquette, Vincent

    2012-07-01

    We propose a new and simple method for the measurement of microbial concentrations in highly diluted cultures. This method is based on an analysis of the intensity fluctuations of light scattered by microbial cells under laser illumination. Two possible measurement strategies are identified and compared using simulations and measurements of the concentration of gold nanoparticles. Based on this comparison, we show that the concentration of Escherichia coli and Saccharomyces cerevisiae cultures can be easily measured in situ across a concentration range that spans five orders of magnitude. The lowest measurable concentration is three orders of magnitude (1000×) smaller than in current optical density measurements. We show further that this method can also be used to measure the concentration of fluorescent microbial cells. In practice, this new method is well suited to monitor the dynamics of population growth at early colonization of a liquid culture medium. The dynamic data thus obtained are particularly relevant for microbial ecology studies.

  14. Probabilistic Model of Microbial Cell Growth, Division, and Mortality ▿

    PubMed Central

    Horowitz, Joseph; Normand, Mark D.; Corradini, Maria G.; Peleg, Micha

    2010-01-01

    After a short time interval of length δt during microbial growth, an individual cell can be found to be divided with probability Pd(t)δt, dead with probability Pm(t)δt, or alive but undivided with the probability 1 − [Pd(t) + Pm(t)]δt, where t is time, Pd(t) expresses the probability of division for an individual cell per unit of time, and Pm(t) expresses the probability of mortality per unit of time. These probabilities may change with the state of the population and the habitat's properties and are therefore functions of time. This scenario translates into a model that is presented in stochastic and deterministic versions. The first, a stochastic process model, monitors the fates of individual cells and determines cell numbers. It is particularly suitable for small populations such as those that may exist in the case of casual contamination of a food by a pathogen. The second, which can be regarded as a large-population limit of the stochastic model, is a continuous mathematical expression that describes the population's size as a function of time. It is suitable for large microbial populations such as those present in unprocessed foods. Exponential or logistic growth with or without lag, inactivation with or without a “shoulder,” and transitions between growth and inactivation are all manifestations of the underlying probability structure of the model. With temperature-dependent parameters, the model can be used to simulate nonisothermal growth and inactivation patterns. The same concept applies to other factors that promote or inhibit microorganisms, such as pH and the presence of antimicrobials, etc. With Pd(t) and Pm(t) in the form of logistic functions, the model can simulate all commonly observed growth/mortality patterns. Estimates of the changing probability parameters can be obtained with both the stochastic and deterministic versions of the model, as demonstrated with simulated data. PMID:19915038

  15. Enhancement of electricity production by graphene oxide in soil microbial fuel cells and plant microbial fuel cells.

    PubMed

    Goto, Yuko; Yoshida, Naoko; Umeyama, Yuto; Yamada, Takeshi; Tero, Ryugo; Hiraishi, Akira

    2015-01-01

    The effects of graphene oxide (GO) on electricity generation in soil microbial fuel cells (SMFCs) and plant microbial fuel cell (PMFCs) were investigated. GO at concentrations ranging from 0 to 1.9 g⋅kg(-1) was added to soil and reduced for 10 days under anaerobic incubation. All SMFCs (GO-SMFCs) utilizing the soils incubated with GO produced electricity at a greater rate and in higher quantities than the SMFCs which did not contain GO. In fed-batch operations, the overall average electricity generation in GO-SMFCs containing 1.0 g⋅kg(-1) of GO was 40 ± 19 mW⋅m(-2), which was significantly higher than the value of 6.6 ± 8.9 mW⋅m(-2) generated from GO-free SMFCs (p < 0.05). The increase in catalytic current at the oxidative potential was observed by cyclic voltammetry (CV) for GO-SMFC, with the CV curve suggesting the enhancement of electron transfer from oxidation of organic substances in the soil by the reduced form of GO. The GO-containing PMFC also displayed a greater generation of electricity compared to the PMFC with no added GO, with GO-PMFC producing 49 mW⋅m(-2) of electricity after 27 days of operation. Collectively, this study demonstrates that GO added to soil can be microbially reduced in soil, and facilitates electron transfer to the anode in both SMFCs and PMFCs.

  16. Enhancement of Electricity Production by Graphene Oxide in Soil Microbial Fuel Cells and Plant Microbial Fuel Cells

    PubMed Central

    Goto, Yuko; Yoshida, Naoko; Umeyama, Yuto; Yamada, Takeshi; Tero, Ryugo; Hiraishi, Akira

    2015-01-01

    The effects of graphene oxide (GO) on electricity generation in soil microbial fuel cells (SMFCs) and plant microbial fuel cell (PMFCs) were investigated. GO at concentrations ranging from 0 to 1.9 g⋅kg−1 was added to soil and reduced for 10 days under anaerobic incubation. All SMFCs (GO-SMFCs) utilizing the soils incubated with GO produced electricity at a greater rate and in higher quantities than the SMFCs which did not contain GO. In fed-batch operations, the overall average electricity generation in GO-SMFCs containing 1.0 g⋅kg−1 of GO was 40 ± 19 mW⋅m−2, which was significantly higher than the value of 6.6 ± 8.9 mW⋅m−2 generated from GO-free SMFCs (p < 0.05). The increase in catalytic current at the oxidative potential was observed by cyclic voltammetry (CV) for GO-SMFC, with the CV curve suggesting the enhancement of electron transfer from oxidation of organic substances in the soil by the reduced form of GO. The GO-containing PMFC also displayed a greater generation of electricity compared to the PMFC with no added GO, with GO-PMFC producing 49 mW⋅m−2 of electricity after 27 days of operation. Collectively, this study demonstrates that GO added to soil can be microbially reduced in soil, and facilitates electron transfer to the anode in both SMFCs and PMFCs. PMID:25883931

  17. Towards an engineering-oriented strategy for building microbial anodes for microbial fuel cells.

    PubMed

    Pocaznoi, Diana; Erable, Benjamin; Etcheverry, Luc; Delia, Marie-Line; Bergel, Alain

    2012-10-14

    The objective of the work was to give some first insight into an engineering-oriented approach to MFC design by focusing on anode optimisation. The effect of various parameters was firstly investigated in half cell set-ups under well-controlled conditions. Microbial anodes were formed from soil leachate under polarisation at -0.2 V vs. SCE with different concentrations of substrate, salt and buffer. It was shown that non-turnover CV could be used to assess the electroactive maturity of the anodes during polarisation. This first phase resulted in the definition of a set of optimal parameter values. In the second phase, an optimal anode was formed in a half-cell under the defined optimal conditions. A numerical approach was then developed to calculate the theoretical maximum power that the anode could provide in an ideal MFC. The concept of "ideal MFC" introduced here allowed the theoretical maximum power to be calculated on the sole basis of the kinetic characteristics of the anode. Finally, a MFC designed in the aim of approaching such ideal conditions generated stable power densities of 6.0 W m(-2), which were among the highest values reported so far. The discrepancy between the theoretical maximum (8.9 W m(-2)) and the experimental results pointed out some limit due to the source of inoculum and suggested possible paths to improvement.

  18. Chemical modulation of the ultra-weak photon emission from Saccharomyces cerevisiae and differentiated HL-60 cells

    NASA Astrophysics Data System (ADS)

    Červinková, Kateřina; Nerudová, Michaela; Hašek, Jiří; Cifra, Michal

    2015-01-01

    The ultra-weak photon emission (UPE) is a universal phenomenon common to all cells with active oxidative metabolism. Generally accepted mechanism of the origin of the ultra-weak photon emission considers reactions of radical or nonradical reactive oxygen species (ROS) with biomolecules such as lipids and proteins which lead to the formation of electron excited species. During the transition to the ground state the excess energy is released as a photon with a wavelength in the visible range of the electromagnetic spectrum. Since the intensity of the light is very low it is possible to be measured only by highly sensitive devices. We used Hamamatsu Photonics PMT module H7360-01 mounted into a light-tight chamber for the purposes of this work. The goal of our research is to delineate an origin of UPE from two model organisms; differentiated HL-60 cells (human promyelocytic leukemia) and yeast cells Saccharomyces cerevisiae. While the UPE from the yeast cells arises spontaneously during the growth without any external stimuli, UPE from HL-60 is induced by phorbol 12-myristate, 13-acetate (PMA). It is possible to modulate the UPE production by certain antioxidants which scavenge ROS formed during the metabolism (yeast cells) or respiratory burst (HL-60 cells). The experiments are focused on the description of effects caused by antioxidants. Several kinds of antioxidants (ascorbic acid, mannitol, glutathione) with different concentration were used and we studied the changes in the UPE intensities of and the temporal developments of the optical signal.

  19. Scanning electrochemical microscopy based evaluation of influence of pH on bioelectrochemical activity of yeast cells - Saccharomyces cerevisiae.

    PubMed

    Ramanavicius, A; Morkvenaite-Vilkonciene, I; Kisieliute, A; Petroniene, J; Ramanaviciene, A

    2017-01-01

    In this research scanning electrochemical microscopy was applied for the investigation of immobilized yeast Saccharomyces cerevisiae cells. Two redox mediators based system was applied in order to increase the efficiency of charge transfer from yeast cells. 9,10-phenanthrenequinone (PQ) was applied as a lipophilic redox mediator, which has the ability to cross the cell's membrane; another redox mediator was ferricyanide, which acted as a hydrophylic electron acceptor able to transfer electrons from the PQ to the working electrode of SECM. Hill's function was applied to determine the optimal pH for this described SECM-based system. The influence of pH on cell viability could be well described by Hill's function. It was determined that at pH 6.5 the PQ has a minimal toxic influence on yeast cells, and the kinetics of metabolic processes in cells as well as electron transfer rate achieved in consecutive action of both redox mediators were appropriate to achieve optimal current signals. Copyright © 2016 Elsevier B.V. All rights reserved.

  20. Effects of low-shear modeled microgravity on cell function, gene expression, and phenotype in Saccharomyces cerevisiae.

    PubMed

    Purevdorj-Gage, B; Sheehan, K B; Hyman, L E

    2006-07-01

    Only limited information is available concerning the effects of low-shear modeled microgravity (LSMMG) on cell function and morphology. We examined the behavior of Saccharomyces cerevisiae grown in a high-aspect-ratio vessel, which simulates the low-shear and microgravity conditions encountered in spaceflight. With the exception of a shortened lag phase (90 min less than controls; P < 0.05), yeast cells grown under LSMMG conditions did not differ in growth rate, size, shape, or viability from the controls but did differ in the establishment of polarity as exhibited by aberrant (random) budding compared to the usual bipolar pattern of controls. The aberrant budding was accompanied by an increased tendency of cells to clump, as indicated by aggregates containing five or more cells. We also found significant changes (greater than or equal to twofold) in the expression of genes associated with the establishment of polarity (BUD5), bipolar budding (RAX1, RAX2, and BUD25), and cell separation (DSE1, DSE2, and EGT2). Thus, low-shear environments may significantly alter yeast gene expression and phenotype as well as evolutionary conserved cellular functions such as polarization. The results provide a paradigm for understanding polarity-dependent cell responses to microgravity ranging from pathogenesis in fungi to the immune response in mammals.

  1. Strengths and weaknesses in the determination of Saccharomyces cerevisiae cell viability by ATP-based bioluminescence assay.

    PubMed

    Paciello, Lucia; Falco, Francesco Cristino; Landi, Carmine; Parascandola, Palma

    2013-03-05

    Due to its sensitivity and speed of execution, detection of ATP by luciferin-luciferase reaction is a widely spread system to highlight cell viability. The paper describes the methodology followed to successfully run the assay in the presence of yeast cells of two strains of the yeast Saccharomyces cerevisiae, BY4741 and CEN.PK2-1C and emphasizes the importance of correctly determining the contact time between the lysing agent and the yeast cells. Once this was established, luciferin-luciferase reaction was exploited to determine the maximum specific rate of growth, as well as cell viability in a series of routine tests. The results obtained in this preliminary study highlighted that using luciferin-luciferase can imply an over-estimation of maximum specific growth rate with respect to that determined by optical density and/or viable count. On the contrary, the bioluminescence assay gave the possibility to highlight, if employed together with viable count, physiological changes occurring in yeast cells as response to stressful environmental conditions such as those deriving from exposure of yeast cells to high temperature or those depending on the operative conditions applied during fed-batch operations.

  2. The Cytosolic pH of Individual Saccharomyces cerevisiae Cells Is a Key Factor in Acetic Acid Tolerance

    PubMed Central

    Fernández-Niño, Miguel; Marquina, Maribel; Swinnen, Steve; Rodríguez-Porrata, Boris

    2015-01-01

    It was shown recently that individual cells of an isogenic Saccharomyces cerevisiae population show variability in acetic acid tolerance, and this variability affects the quantitative manifestation of the trait at the population level. In the current study, we investigated whether cell-to-cell variability in acetic acid tolerance could be explained by the observed differences in the cytosolic pHs of individual cells immediately before exposure to the acid. Results obtained with cells of the strain CEN.PK113-7D in synthetic medium containing 96 mM acetic acid (pH 4.5) showed a direct correlation between the initial cytosolic pH and the cytosolic pH drop after exposure to the acid. Moreover, only cells with a low initial cytosolic pH, which experienced a less severe drop in cytosolic pH, were able to proliferate. A similar correlation between initial cytosolic pH and cytosolic pH drop was also observed in the more acid-tolerant strain MUCL 11987-9. Interestingly, a fraction of cells in the MUCL 11987-9 population showed initial cytosolic pH values below the minimal cytosolic pH detected in cells of the strain CEN.PK113-7D; consequently, these cells experienced less severe drops in cytosolic pH. Although this might explain in part the difference between the two strains with regard to the number of cells that resumed proliferation, it was observed that all cells from strain MUCL 11987-9 were able to proliferate, independently of their initial cytosolic pH. Therefore, other factors must also be involved in the greater ability of MUCL 11987-9 cells to endure strong drops in cytosolic pH. PMID:26341199

  3. The Cytosolic pH of Individual Saccharomyces cerevisiae Cells Is a Key Factor in Acetic Acid Tolerance.

    PubMed

    Fernández-Niño, Miguel; Marquina, Maribel; Swinnen, Steve; Rodríguez-Porrata, Boris; Nevoigt, Elke; Ariño, Joaquín

    2015-11-01

    It was shown recently that individual cells of an isogenic Saccharomyces cerevisiae population show variability in acetic acid tolerance, and this variability affects the quantitative manifestation of the trait at the population level. In the current study, we investigated whether cell-to-cell variability in acetic acid tolerance could be explained by the observed differences in the cytosolic pHs of individual cells immediately before exposure to the acid. Results obtained with cells of the strain CEN.PK113-7D in synthetic medium containing 96 mM acetic acid (pH 4.5) showed a direct correlation between the initial cytosolic pH and the cytosolic pH drop after exposure to the acid. Moreover, only cells with a low initial cytosolic pH, which experienced a less severe drop in cytosolic pH, were able to proliferate. A similar correlation between initial cytosolic pH and cytosolic pH drop was also observed in the more acid-tolerant strain MUCL 11987-9. Interestingly, a fraction of cells in the MUCL 11987-9 population showed initial cytosolic pH values below the minimal cytosolic pH detected in cells of the strain CEN.PK113-7D; consequently, these cells experienced less severe drops in cytosolic pH. Although this might explain in part the difference between the two strains with regard to the number of cells that resumed proliferation, it was observed that all cells from strain MUCL 11987-9 were able to proliferate, independently of their initial cytosolic pH. Therefore, other factors must also be involved in the greater ability of MUCL 11987-9 cells to endure strong drops in cytosolic pH.

  4. Integrated hydrogen production process from cellulose by combining dark fermentation, microbial fuel cells, and a microbial electrolysis cell.

    PubMed

    Wang, Aijie; Sun, Dan; Cao, Guangli; Wang, Haoyu; Ren, Nanqi; Wu, Wei-Min; Logan, Bruce E

    2011-03-01

    Hydrogen gas production from cellulose was investigated using an integrated hydrogen production process consisting of a dark fermentation reactor and microbial fuel cells (MFCs) as power sources for a microbial electrolysis cell (MEC). Two MFCs (each 25 mL) connected in series to an MEC (72 mL) produced a maximum of 0.43 V using fermentation effluent as a feed, achieving a hydrogen production rate from the MEC of 0.48 m(3) H(2)/m(3)/d (based on the MEC volume), and a yield of 33.2 mmol H(2)/g COD removed in the MEC. The overall hydrogen production for the integrated system (fermentation, MFC and MEC) was increased by 41% compared with fermentation alone to 14.3 mmol H(2)/g cellulose, with a total hydrogen production rate of 0.24 m(3) H(2)/m(3)/d and an overall energy recovery efficiency of 23% (based on cellulose removed) without the need for any external electrical energy input.

  5. Complete cobalt recovery from lithium cobalt oxide in self-driven microbial fuel cell - Microbial electrolysis cell systems

    NASA Astrophysics Data System (ADS)

    Huang, Liping; Yao, Binglin; Wu, Dan; Quan, Xie

    2014-08-01

    Complete cobalt recovery from lithium cobalt oxide requires to firstly leach cobalt from particles LiCoO2 and then recover cobalt from aqueous Co(II). A self-driven microbial fuel cell (MFC)-microbial electrolysis cell (MEC) system can completely carry out these two processes, in which Co(II) is firstly released from particles LiCoO2 on the cathodes of MFCs and then reduced on the cathodes of MECs which are powered by the cobalt leaching MFCs. A cobalt leaching rate of 46 ± 2 mg L-1 h-1 with yield of 1.5 ± 0.1 g Co g-1 COD (MFCs) and a Co(II) reduction rate of 7 ± 0 mg L-1 h-1 with yield of 0.8 ± 0.0 g Co g-1 COD (MECs), as well as a overall system cobalt yield of 0.15 ± 0.01 g Co g-1 Co can be achieved in this self-driven MFC-MEC system. Coulombic efficiencies reach 41 ± 1% (anodic MFCs), 75 ± 0% (anodic MECs), 100 ± 2% (cathodic MFCs), and 29 ± 1% (cathodic MECs) whereas overall system efficiency averages 34 ± 1%. These results provide a new process of linking MFCs to MECs for complete recovery of cobalt and recycle of spent lithium ion batteries with no external energy consumption.

  6. Energy-positive wastewater treatment and desalination in an integrated microbial desalination cell (MDC)-microbial electrolysis cell (MEC)

    NASA Astrophysics Data System (ADS)

    Li, Yan; Styczynski, Jordyn; Huang, Yuankai; Xu, Zhiheng; McCutcheon, Jeffrey; Li, Baikun

    2017-07-01

    Simultaneous removal of nitrogen in municipal wastewater, metal in industrial wastewater and saline in seawater was achieved in an integrated microbial desalination cell-microbial electrolysis cell (MDC-MEC) system. Batch tests showed that more than 95.1% of nitrogen was oxidized by nitrification in the cathode of MDC and reduced by heterotrophic denitrification in the anode of MDC within 48 h, leading to the total nitrogen removal rate of 4.07 mg L-1 h-1. Combining of nitrogen removal and desalination in MDC effectively solved the problem of pH fluctuation in anode and cathode, and led to 63.7% of desalination. Power generation of MDC (293.7 mW m-2) was 2.9 times higher than the one without salt solution. The electric power of MDC was harvested by a capacitor circuit to supply metal reduction in a MEC, and 99.5% of lead (II) was removed within 48 h. A kinetic MDC model was developed to elucidate the correlation of voltage output and desalination efficiency. Ratio of wastewater and sea water was calculated for MDC optimal operation. Energy balance of nutrient removal, metal removal and desalination in the MDC-MEC system was positive (0.0267 kW h m-3), demonstrating the promise of utilizing low power output of MDCs.

  7. Self-sustained reduction of multiple metals in a microbial fuel cell-microbial electrolysis cell hybrid system.

    PubMed

    Li, Yan; Wu, Yining; Liu, Bingchuan; Luan, Hongwei; Vadas, Timothy; Guo, Wanqian; Ding, Jie; Li, Baikun

    2015-09-01

    A self-sustained hybrid bioelectrochemical system consisting of microbial fuel cell (MFC) and microbial electrolysis cell (MEC) was developed to reduce multiple metals simultaneously by utilizing different reaction potentials. Three heavy metals representing spontaneous reaction (chromium, Cr) and unspontaneous reaction (lead, Pb and nickel, Ni) were selected in this batch-mode study. The maximum power density of the MFC achieved 189.4 mW m(-2), and the energy recovery relative to the energy storage circuit (ESC) was ∼ 450%. At the initial concentration of 100 mg L(-1), the average reduction rate of Cr(VI) was 30.0 mg L(-1) d(-1), Pb(II) 32.7 mg L(-1) d(-1), and Ni(II) 8.9 mg L(-1) d(-1). An electrochemical model was developed to predict the change of metal concentration over time. The power output of the MFC was sufficient to meet the requirement of the ESC and MEC, and the "self-sustained metal reduction" was achieved in this hybrid system.

  8. A comparison of simultaneous organic carbon and nitrogen removal in microbial fuel cells and microbial electrolysis cells.

    PubMed

    Hussain, Abid; Manuel, Michelle; Tartakovsky, Boris

    2016-05-15

    This study demonstrates simultaneous carbon and nitrogen removal in laboratory-scale continuous flow microbial fuel cell (MFC) and microbial electrolysis cell (MEC) and provides side-by side comparison of these bioelectrochemical systems. The maximum organic carbon removal rates in MFC and MEC tests were similar at 5.1 g L(-1) d(-1) and 4.16 g L(-1) d(-1), respectively, with a near 100% carbon removal efficiency at an organic load of 3.3 g L(-1) d(-1). An ammonium removal efficiency of 30-55% with near-zero nitrite and nitrate concentrations was observed in the MFC operated at an optimal external resistance, while open-circuit MFC operation resulted in a reduced carbon and ammonium removal of 53% and 21%, respectively. In the MEC ammonium removal was limited to 7-12% under anaerobic conditions, while micro-aerobic conditions increased the removal efficiency to 31%. Also, at zero applied voltage both carbon and ammonium removal efficiencies were reduced to 42% and 4%, respectively. Based on the observed performance under different operating conditions, it was concluded that simultaneous carbon and nitrogen removal was facilitated by concurrent anaerobic and aerobic biotransformation pathways at the anode and cathode, which balanced bioelectrochemical nitrification and denitrification reactions.

  9. Development of microbial genome-probing microarrays using digital multiple displacement amplification of uncultivated microbial single cells.

    PubMed

    Chang, Ho-Won; Sung, Youlboong; Kim, Kyoung-Ho; Nam, Young-Do; Roh, Seong Woon; Kim, Min-Soo; Jeon, Che Ok; Bae, Jin-Woo

    2008-08-15

    A crucial problem in the use of previously developed genome-probing microarrays (GPM) has been the inability to use uncultivated bacterial genomes to take advantage of the high sensitivity and specificity of GPM in microbial detection and monitoring. We show here a method, digital multiple displacement amplification (MDA), to amplify and analyze various genomes obtained from single uncultivated bacterial cells. We used 15 genomes from key microbes involved in dichloromethane (DCM)-dechlorinating enrichment as microarray probes to uncover the bacterial population dynamics of samples without PCR amplification. Genomic DNA amplified from single cells originating from uncultured bacteria with 80.3-99.4% similarity to 16S rRNA genes of cultivated bacteria. The digital MDA-GPM method successfully monitored the dynamics of DCM-dechlorinating communities from different phases of enrichment status. Without a priori knowledge of microbial diversity, the digital MDA-GPM method could be designed to monitor most microbial populations in a given environmental sample.

  10. Genomic Sequencing of Single Microbial Cells from Environmental Samples

    SciTech Connect

    Ishoey, Thomas; Woyke, Tanja; Stepanauskas, Ramunas; Novotny, Mark; Lasken, Roger S.

    2008-02-01

    Recently developed techniques allow genomic DNA sequencing from single microbial cells [Lasken RS: Single-cell genomic sequencing using multiple displacement amplification, Curr Opin Microbiol 2007, 10:510-516]. Here, we focus on research strategies for putting these methods into practice in the laboratory setting. An immediate consequence of single-cell sequencing is that it provides an alternative to culturing organisms as a prerequisite for genomic sequencing. The microgram amounts of DNA required as template are amplified from a single bacterium by a method called multiple displacement amplification (MDA) avoiding the need to grow cells. The ability to sequence DNA from individual cells will likely have an immense impact on microbiology considering the vast numbers of novel organisms, which have been inaccessible unless culture-independent methods could be used. However, special approaches have been necessary to work with amplified DNA. MDA may not recover the entire genome from the single copy present in most bacteria. Also, some sequence rearrangements can occur during the DNA amplification reaction. Over the past two years many research groups have begun to use MDA, and some practical approaches to single-cell sequencing have been developed. We review the consensus that is emerging on optimum methods, reliability of amplified template, and the proper interpretation of 'composite' genomes which result from the necessity of combining data from several single-cell MDA reactions in order to complete the assembly. Preferred laboratory methods are considered on the basis of experience at several large sequencing centers where >70% of genomes are now often recovered from single cells. Methods are reviewed for preparation of bacterial fractions from environmental samples, single-cell isolation, DNA amplification by MDA, and DNA sequencing.

  11. Sorption of trivalent cerium by a mixture of microbial cells and manganese oxides: Effect of microbial cells on the oxidation of trivalent cerium

    NASA Astrophysics Data System (ADS)

    Ohnuki, Toshihiko; Jiang, Mingyu; Sakamoto, Fuminori; Kozai, Naofumi; Yamasaki, Shinya; Yu, Qianqian; Tanaka, Kazuya; Utsunomiya, Satoshi; Xia, Xiaobin; Yang, Ke; He, Jianhua

    2015-08-01

    Sorption of Ce by mixtures of synthetic Mn oxides and microbial cells of Pseudomonas fluorescens was investigated to elucidate the role of microorganisms on Ce(III) oxidative migration in the environment. The mixtures, upon which Ce was sorbed following exposure to solutions containing 1.0 × 10-4 or 1.0 × 10-5 mol L-1 Ce(III), were analyzed by scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS) and micro-X-ray fluorescence (micro-XRF) at synchrotron facilities. A Ce LIII-edge micro XANES spectra analysis was also performed to determine the oxidation states of Ce adsorbed to the Mn oxides and microbial cells in the mixtures. The distribution ratios (Kd) of Ce between the individual solids and solution increased with increasing pH of the solution, and was nearly the same in mixtures containing varying amounts of microbial cells. SEM-EDS and micro-XRF analyses showed that Ce was sorbed by both MnO2 and microbial cells (1.7 × 10-1 or 3.3 × 10-1 g L-1). In addition, nano-particles containing Ce and P developed on the surface of the microbial cells. XANES analysis showed that lower fractions of Ce(III) were oxidized to Ce(IV) in the mixtures containing greater amounts of microbial cells. Micro-XANES analysis revealed that Ce was present as Ce(III) on the microbial cells and as Ce(IV) on Mn oxides. These results strongly suggest that the association of Ce(III) with the microbial cell surface and the formation of Ce phosphate nano-particles are responsible for suppressing the oxidation of Ce(III) to Ce(IV) in the mixtures.

  12. Atomic Force Microscopy in Microbiology: New Structural and Functional Insights into the Microbial Cell Surface

    PubMed Central

    2014-01-01

    ABSTRACT Microbial cells sense and respond to their environment using their surface constituents. Therefore, understanding the assembly and biophysical properties of cell surface molecules is an important research topic. With its ability to observe living microbial cells at nanometer resolution and to manipulate single-cell surface molecules, atomic force microscopy (AFM) has emerged as a powerful tool in microbiology. Here, we survey major breakthroughs made in cell surface microbiology using AFM techniques, emphasizing the most recent structural and functional insights. PMID:25053785

  13. Expression of a mutated SPT15 gene in Saccharomyces cerevisiae enhances both cell growth and ethanol production in microaerobic batch, fed-batch, and simultaneous saccharification and fermentations.

    PubMed

    Seong, Yeong-Je; Park, Haeseong; Yang, Jungwoo; Kim, Soo-Jung; Choi, Wonja; Kim, Kyoung Heon; Park, Yong-Cheol

    2017-05-01

    The SPT15 gene encodes a Saccharomyces cerevisiae TATA-binding protein, which is able to globally control the transcription levels of various metabolic and regulatory genes. In this study, a SPT15 gene mutant (S42N, S78R, S163P, and I212N) was expressed in S. cerevisiae BY4741 (BSPT15-M3), of which effects on fermentative yeast properties were evaluated in a series of culture types. By applying different nitrogen sources and air supply conditions in batch culture, organic nitrogen sources and microaerobic condition were decided to be more favorable for both cell growth and ethanol production of the BSPT15-M3 strain than the control S. cerevisiae BY4741 strain expressing the SPT15 gene (BSPT15wt). Microaerobic fed-batch cultures of BSPT15-M3 with glucose shock in the presence of high ethanol content resulted in a 9.5-13.4% higher glucose consumption rate and ethanol productivity than those for the BSPT15wt strain. In addition, BSPT15-M3 showed 4.5 and 3.9% increases in ethanol productivity from cassava hydrolysates and corn starch in simultaneous saccharification and fermentation processes, respectively. It was concluded that overexpression of the mutated SPT15 gene would be a potent strategy to develop robust S. cerevisiae strains with enhanced cell growth and ethanol production abilities.

  14. Antiapoptotic role of S-adenosyl-l-methionine against hydrochloric acid induced cell death in Saccharomyces cerevisiae.

    PubMed

    Malakar, Dipankar; Dey, Anindya; Basu, Arghya; Ghosh, Anil K

    2008-01-01

    Exposure of stationary phase cells of Saccharomyces cerevisiae to 10 mM HCl (pH approximately 2) resulted in cell death as a function of time (up to 6 h) with most (about 40%-65%) of the cells showing apoptotic features including chromatin condensation along the nuclear envelope, exposure of phosphatidylserine on the outer leaflet of cytoplasmic membrane, and DNA fragmentation. During the first 2 h of acid exposure there was an increase in reactive oxygen species (ROS) level inside cells, with subsequent elevation in the level of lipid peroxidation and decrease in reducing equivalents culminating in loss of mitochondrial membrane potential (DeltaPsi(m)). An initial (1 h) event of mitochondrial hyper-polarization with subsequent elevation of ROS level of the acid treated cells was also observed. S-adenosyl-l-methionine (AdoMet; 1 mM) treatment increased the cell survival of the acid stressed cells. It partially scavenged the increased intracellular ROS level by supplementing glutathione through the transsulfuration pathway. It also inhibited acid mediated lipid peroxidation, partially recovered acid evoked loss of DeltaPsi(m) and protected the cells from apoptotic cell death. S-adenosyl di-aldehyde, an indirect inhibitor of the AdoMet metabolic pathway, increased mortality of the acid treated cells. Incubation of acid stressed cells with the antioxidant, N-acetyl-cysteine (1 mM), decreased the cellular mortality, but the same concentration of AdoMet offered more protection by scavenging the free radicals. The ability of AdoMet to scavenge ROS mediated apoptosis may be an important function of this molecule in responding to cellular stress. The study could open a new avenue for detailed investigation on the curative potential of AdoMet against gastric ulcer.

  15. A role for programmed cell death in the microbial loop.

    PubMed

    Orellana, Mónica V; Pang, Wyming L; Durand, Pierre M; Whitehead, Kenia; Baliga, Nitin S

    2013-01-01

    The microbial loop is the conventional model by which nutrients and minerals are recycled in aquatic eco-systems. Biochemical pathways in different organisms become metabolically inter-connected such that nutrients are utilized, processed, released and re-utilized by others. The result is that unrelated individuals end up impacting each others' fitness directly through their metabolic activities. This study focused on the impact of programmed cell death (PCD) on a population's growth as well as its role in the exchange of carbon between two naturally co-occurring halophilic organisms. Flow cytometric, biochemical, ¹⁴C radioisotope tracing assays, and global transcriptomic analyses show that organic algal photosynthate released by Dunalliela salina cells undergoing PCD complements the nutritional needs of other non-PCD D. salina cells. This occurs in vitro in a carbon limited environment and enhances the growth of the population. In addition, a co-occurring heterotroph Halobacterium salinarum re-mineralizes the carbon providing elemental nutrients for the mixoheterotrophic chlorophyte. The significance of this is uncertain and the archaeon can also subsist entirely on the lysate of apoptotic algae. PCD is now well established in unicellular organisms; however its ecological relevance has been difficult to decipher. In this study we found that PCD in D. salina causes the release of organic nutrients such as glycerol, which can be used by others in the population as well as a co-occurring halophilic archaeon. H. salinarum also re-mineralizes the dissolved material promoting algal growth. PCD in D. salina was the mechanism for the flow of dissolved photosynthate between unrelated organisms. Ironically, programmed death plays a central role in an organism's own population growth and in the exchange of nutrients in the microbial loop.

  16. A Role for Programmed Cell Death in the Microbial Loop

    PubMed Central

    Durand, Pierre M.; Whitehead, Kenia; Baliga, Nitin S.

    2013-01-01

    The microbial loop is the conventional model by which nutrients and minerals are recycled in aquatic eco-systems. Biochemical pathways in different organisms become metabolically inter-connected such that nutrients are utilized, processed, released and re-utilized by others. The result is that unrelated individuals end up impacting each others' fitness directly through their metabolic activities. This study focused on the impact of programmed cell death (PCD) on a population's growth as well as its role in the exchange of carbon between two naturally co-occurring halophilic organisms. Flow cytometric, biochemical, 14C radioisotope tracing assays, and global transcriptomic analyses show that organic algal photosynthate released by Dunalliela salina cells undergoing PCD complements the nutritional needs of other non-PCD D. salina cells. This occurs in vitro in a carbon limited environment and enhances the growth of the population. In addition, a co-occurring heterotroph Halobacterium salinarum re-mineralizes the carbon providing elemental nutrients for the mixoheterotrophic chlorophyte. The significance of this is uncertain and the archaeon can also subsist entirely on the lysate of apoptotic algae. PCD is now well established in unicellular organisms; however its ecological relevance has been difficult to decipher. In this study we found that PCD in D. salina causes the release of organic nutrients such as glycerol, which can be used by others in the population as well as a co-occurring halophilic archaeon. H. salinarum also re-mineralizes the dissolved material promoting algal growth. PCD in D. salina was the mechanism for the flow of dissolved photosynthate between unrelated organisms. Ironically, programmed death plays a central role in an organism's own population growth and in the exchange of nutrients in the microbial loop. PMID:23667496

  17. Integrated Microfluidic Flow-Through Microbial Fuel Cells

    PubMed Central

    Jiang, Huawei; Ali, Md. Azahar; Xu, Zhen; Halverson, Larry J.; Dong, Liang

    2017-01-01

    This paper reports on a miniaturized microbial fuel cell with a microfluidic flow-through configuration: a porous anolyte chamber is formed by filling a microfluidic chamber with three-dimensional graphene foam as anode, allowing nutritional medium to flow through the chamber to intimately interact with the colonized microbes on the scaffolds of the anode. No nutritional media flow over the anode. This allows sustaining high levels of nutrient utilization, minimizing consumption of nutritional substrates, and reducing response time of electricity generation owing to fast mass transport through pressure-driven flow and rapid diffusion of nutrients within the anode. The device provides a volume power density of 745 μW/cm3 and a surface power density of 89.4 μW/cm2 using Shewanella oneidensis as a model biocatalyst without any optimization of bacterial culture. The medium consumption and the response time of the flow-through device are reduced by 16.4 times and 4.2 times, respectively, compared to the non-flow-through counterpart with its freeway space volume six times the volume of graphene foam anode. The graphene foam enabled microfluidic flow-through approach will allow efficient microbial conversion of carbon-containing bioconvertible substrates to electricity with smaller space, less medium consumption, and shorter start-up time. PMID:28120875

  18. Integrated Microfluidic Flow-Through Microbial Fuel Cells

    NASA Astrophysics Data System (ADS)

    Jiang, Huawei; Ali, Md. Azahar; Xu, Zhen; Halverson, Larry J.; Dong, Liang

    2017-01-01

    This paper reports on a miniaturized microbial fuel cell with a microfluidic flow-through configuration: a porous anolyte chamber is formed by filling a microfluidic chamber with three-dimensional graphene foam as anode, allowing nutritional medium to flow through the chamber to intimately interact with the colonized microbes on the scaffolds of the anode. No nutritional media flow over the anode. This allows sustaining high levels of nutrient utilization, minimizing consumption of nutritional substrates, and reducing response time of electricity generation owing to fast mass transport through pressure-driven flow and rapid diffusion of nutrients within the anode. The device provides a volume power density of 745 μW/cm3 and a surface power density of 89.4 μW/cm2 using Shewanella oneidensis as a model biocatalyst without any optimization of bacterial culture. The medium consumption and the response time of the flow-through device are reduced by 16.4 times and 4.2 times, respectively, compared to the non-flow-through counterpart with its freeway space volume six times the volume of graphene foam anode. The graphene foam enabled microfluidic flow-through approach will allow efficient microbial conversion of carbon-containing bioconvertible substrates to electricity with smaller space, less medium consumption, and shorter start-up time.

  19. Control of malodorous hydrogen sulfide compounds using microbial fuel cell.

    PubMed

    Eaktasang, Numfon; Min, Hyeong-Sik; Kang, Christina; Kim, Han S

    2013-10-01

    In this study, a microbial fuel cell (MFC) was used to control malodorous hydrogen sulfide compounds generated from domestic wastewaters. The electricity production demonstrated a distinct pattern of a two-step increase during 170 h of system run: the first maximum current density was 118.6 ± 7.2 mA m⁻² followed by a rebound of current density increase, reaching the second maximum of 176.8 ± 9.4 mA m⁻². The behaviors of the redox potential and the sulfate level in the anode compartment indicated that the microbial production of hydrogen sulfide compounds was suppressed in the first stage, and the hydrogen sulfide compounds generated from the system were removed effectively as a result of their electrochemical oxidation, which contributed to the additional electricity production in the second stage. This was also directly supported by sulfur deposits formed on the anode surface, which was confirmed by analyses on those solids using a scanning electron microscope equipped with energy dispersive X-ray spectroscopy as well as an elemental analyzer. To this end, the overall reduction efficiencies for HS⁻ and H₂S(g) were as high as 67.5 and 96.4 %, respectively. The correlations among current density, redox potential, and sulfate level supported the idea that the electricity signal generated in the MFC can be utilized as a potential indicator of malodor control for the domestic wastewater system.

  20. Stimulating sediment bioremediation with benthic microbial fuel cells.

    PubMed

    Li, Wen-Wei; Yu, Han-Qing

    2015-01-01

    Efficient and sustainable technologies for cleaning up of contaminated sediments are under urgent demand. Bioremediation by utilizing the natural metabolic activities of sediment-inhabited microorganisms has been widely accepted as a viable option, but the relatively low efficiency and poor controllability severely limite its application. Here, we bring out the concept that electrochemical approaches may be used as an efficient means to stimulate sediment bioremediation. Although still at the very beginning, benthic microbial fuel cells (BMFC) as a remediation technology show many potential benefits, such as accelerated decontamination, self-sustained operation, relatively easy deployment and control, and environmental benignity. The unique features of BMFC setup and operation also give rise to substantially different challenges compared to conventional MFCs. In this review, we present a critical overview on the characteristics, possible application niches, and state-of-the-art progress of this technology. Especially, the current limitations in respect of system design, electrode selection, microbial control and selection of deployment environment are discussed in details, and the needed future research endeavors to promote its practical application are highlighted.

  1. An Overview of Electron Acceptors in Microbial Fuel Cells

    PubMed Central

    Ucar, Deniz; Zhang, Yifeng; Angelidaki, Irini

    2017-01-01

    Microbial fuel cells (MFC) have recently received increasing attention due to their promising potential in sustainable wastewater treatment and contaminant removal. In general, contaminants can be removed either as an electron donor via microbial catalyzed oxidization at the anode or removed at the cathode as electron acceptors through reduction. Some contaminants can also function as electron mediators at the anode or cathode. While previous studies have done a thorough assessment of electron donors, cathodic electron acceptors and mediators have not been as well described. Oxygen is widely used as an electron acceptor due to its high oxidation potential and ready availability. Recent studies, however, have begun to assess the use of different electron acceptors because of the (1) diversity of redox potential, (2) needs of alternative and more efficient cathode reaction, and (3) expanding of MFC based technologies in different areas. The aim of this review was to evaluate the performance and applicability of various electron acceptors and mediators used in MFCs. This review also evaluated the corresponding performance, advantages and disadvantages, and future potential applications of select electron acceptors (e.g., nitrate, iron, copper, perchlorate) and mediators. PMID:28469607

  2. Integrated Microfluidic Flow-Through Microbial Fuel Cells.

    PubMed

    Jiang, Huawei; Ali, Md Azahar; Xu, Zhen; Halverson, Larry J; Dong, Liang

    2017-01-25

    This paper reports on a miniaturized microbial fuel cell with a microfluidic flow-through configuration: a porous anolyte chamber is formed by filling a microfluidic chamber with three-dimensional graphene foam as anode, allowing nutritional medium to flow through the chamber to intimately interact with the colonized microbes on the scaffolds of the anode. No nutritional media flow over the anode. This allows sustaining high levels of nutrient utilization, minimizing consumption of nutritional substrates, and reducing response time of electricity generation owing to fast mass transport through pressure-driven flow and rapid diffusion of nutrients within the anode. The device provides a volume power density of 745 μW/cm(3) and a surface power density of 89.4 μW/cm(2) using Shewanella oneidensis as a model biocatalyst without any optimization of bacterial culture. The medium consumption and the response time of the flow-through device are reduced by 16.4 times and 4.2 times, respectively, compared to the non-flow-through counterpart with its freeway space volume six times the volume of graphene foam anode. The graphene foam enabled microfluidic flow-through approach will allow efficient microbial conversion of carbon-containing bioconvertible substrates to electricity with smaller space, less medium consumption, and shorter start-up time.

  3. Microbial fuel cells operating on mixed fatty acids.

    PubMed

    Freguia, Stefano; Teh, Ee Hoi; Boon, Nico; Leung, Kar Man; Keller, Jurg; Rabaey, Korneel

    2010-02-01

    Strategies are being developed to harvest the energy content of the wasted sludge generated from the treatment of domestic wastewater. Sludge can be hydrolysed and fermented, giving a mixture of volatile fatty acids (VFAs). Based on the composition of such a fermented stream, synthetic media were created and tested for VFA conversion in microbial fuel cells (MFCs). Mainly acetate and propionate were preferred as electron donors in the mixed VFA system, which generated a power density of 49+/-1 mW L(NAC)(-1). The other VFAs (butyrates/valerates/caproic acid) were also removed, albeit at lower rates. In single VFA tests, each VFA could be removed, but particularly i-butyrate did not provide significant current generation. PCR-DGGE indicated that the microbial community structure was highly determined by the fed VFA, rather than by the initial inoculum. The communities were dominated by Proteobacteria such as Geobacter, Comamonas, Pseudomonas and Pelobacter species. This study demonstrated the feasibility of using fatty acids, as present in fermented sludge hydrolysates, for current generation.

  4. New applications of carbon nanostructures in microbial fuel cells (MFC)

    NASA Astrophysics Data System (ADS)

    Kaca, W.; Żarnowiec, P.; Keczkowska, Justyna; Suchańska, M.; Czerwosz, E.; Kozłowski, M.

    2014-11-01

    In the studies presented we proposed a new application for nanocomposite carbon films (C-Pd). These films were evaluated as an anode material for Microbial Fuel Cells (MFCs) used for electrical current generation. The results of characterization of C-Pd films composed of carbon and palladium nanograins were obtained using the Physical Vapor Deposition (PVD) method. The film obtained by this method exhibits a multiphase structure composed of fullerene nanograins, amorphous carbon and palladium nanocrystals. Raman Spectroscopy (RS) and scanning electron microscopy (SEM) are used to characterize the chemical composition, morphology and topography of these films. We observed, for MFC with C-Pd anode, the highest electrochemical activity and maximal voltage density - 458 mV (20,8 mV/cm2) for Proteus mirabilis, 426 mV (19,4 mV/cm2) for Pseudomonas aeruginosa and 652 mV (29,6 mV/cm2) for sewage bacteria as the microbial catalyst.

  5. An Overview of Electron Acceptors in Microbial Fuel Cells.

    PubMed

    Ucar, Deniz; Zhang, Yifeng; Angelidaki, Irini

    2017-01-01

    Microbial fuel cells (MFC) have recently received increasing attention due to their promising potential in sustainable wastewater treatment and contaminant removal. In general, contaminants can be removed either as an electron donor via microbial catalyzed oxidization at the anode or removed at the cathode as electron acceptors through reduction. Some contaminants can also function as electron mediators at the anode or cathode. While previous studies have done a thorough assessment of electron donors, cathodic electron acceptors and mediators have not been as well described. Oxygen is widely used as an electron acceptor due to its high oxidation potential and ready availability. Recent studies, however, have begun to assess the use of different electron acceptors because of the (1) diversity of redox potential, (2) needs of alternative and more efficient cathode reaction, and (3) expanding of MFC based technologies in different areas. The aim of this review was to evaluate the performance and applicability of various electron acceptors and mediators used in MFCs. This review also evaluated the corresponding performance, advantages and disadvantages, and future potential applications of select electron acceptors (e.g., nitrate, iron, copper, perchlorate) and mediators.

  6. Electricity generation from tetrathionate in microbial fuel cells by acidophiles.

    PubMed

    Sulonen, Mira L K; Kokko, Marika E; Lakaniemi, Aino-Maija; Puhakka, Jaakko A

    2015-03-02

    Inorganic sulfur compounds, such as tetrathionate, are often present in mining process and waste waters. The biodegradation of tetrathionate was studied under acidic conditions in aerobic batch cultivations and in anaerobic anodes of two-chamber flow-through microbial fuel cells (MFCs). All four cultures originating from biohydrometallurgical process waters from multimetal ore heap bioleaching oxidized tetrathionate aerobically at pH below 3 with sulfate as the main soluble metabolite. In addition, all cultures generated electricity from tetrathionate in MFCs at pH below 2.5 with ferric iron as the terminal cathodic electron acceptor. The maximum current and power densities during MFC operation and in the performance analysis were 79.6 mA m(-2) and 13.9 mW m(-2) and 433 mA m(-2) and 17.6 mW m(-2), respectively. However, the low coulombic efficiency (below 5%) indicates that most of the electrons were directed to other processes, such as aerobic oxidation of tetrathionate and unmeasured intermediates. The microbial community analysis revealed that the dominant species both in the anolyte and on the anode electrode surface of the MFCs were Acidithiobacillus spp. and Ferroplasma spp. This study provides a proof of concept that tetrathionate serves as electron donor for biological electricity production in the pH range of 1.2-2.5.

  7. Cell-to-cell contact and antimicrobial peptides play a combined role in the death of Lachanchea thermotolerans during mixed-culture alcoholic fermentation with Saccharomyces cerevisiae.

    PubMed

    Kemsawasd, Varongsiri; Branco, Patrícia; Almeida, Maria Gabriela; Caldeira, Jorge; Albergaria, Helena; Arneborg, Nils

    2015-07-01

    The roles of cell-to-cell contact and antimicrobial peptides in the early death of Lachanchea thermotolerans CBS2803 during anaerobic, mixed-culture fermentations with Saccharomyces cerevisiae S101 were investigated using a commercially available, double-compartment fermentation system separated by cellulose membranes with different pore sizes, i.e. 1000 kDa for mixed- and single-culture fermentations, and 1000 and 3.5-5 kDa for compartmentalized-culture fermentations. SDS-PAGE and gel filtration chromatography were used to determine an antimicrobial peptidic fraction in the fermentations. Our results showed comparable amounts of the antimicrobial peptidic fraction in the inner compartments of the mixed-culture and 1000 kDa compartmentalized-culture fermentations containing L. thermotolerans after 4 days of fermentation, but a lower death rate of L. thermotolerans in the 1000 kDa compartmentalized-culture fermentation than in the mixed-culture fermentation. Furthermore, L. thermotolerans died off even more slowly in the 3.5-5 kDa than in the 1000 kDa compartmentalized-culture fermentation, which coincided with the presence of less of the antimicrobial peptidic fraction in the inner compartment of that fermentation than of the 1000 kDa compartmentalized-culture fermentation. Taken together, these results indicate that the death of L. thermotolerans in mixed cultures with S. cerevisiae is caused by a combination of cell-to-cell contact and antimicrobial peptides.

  8. Saccharomyces cerevisiae Shuttle vectors.

    PubMed

    Gnügge, Robert; Rudolf, Fabian

    2017-01-10

    Yeast shuttle vectors are indispensable tools in yeast research. They enable cloning of defined DNA sequences in Escherichia coli and their direct transfer into Saccharomyces cerevisiae cells. There are three types of commonly used yeast shuttle vectors: centromeric plasmids, episomal plasmids and integrating plasmids. In this review, we discuss the different plasmid systems and their characteristic features. We focus on their segregational stability and copy number and indicate how to modify these properties. Copyright © 2017 John Wiley & Sons, Ltd.

  9. [Cell surface display of Yarrowia lipolytica lipase Lip2 in Saccharomyces cerevisiae with a-agglutinin as carrier protein].

    PubMed

    Liu, Wenshan; Xu, Li; Zhao, Heyun; Yang, Jiangke; Yan, Yunjun

    2008-11-01

    In order to display extracellular.lipase Lip2 from Yarrowia lipolytica on the surface of yeast Saccharomyces cerevisiae for whole cell catalysts. The mature Lip2 encoding fragment was amplified from Yarrowia lipolytica total DNA, and was inserted into the 3'terminal of AGA2 to give the plasmid pCTLIP2 for surface display of Lip2. Olive oil, tributyrin and p-nitrophenyl palmitate (pNPP) were used as substrates to measure lipase activity. Moreover, the characterization of displayed lipase and its free form was analyzed. The surface displayed lipase was confirmed to be active towards olive oil, tributyrin and p-nitrophenyl palmitate (pNPP), and reached its highest expression level at 182 U/g dry cell after induced by galactose for 72h. The optimum temperature of cell surface displayed Lip2 was 40 degrees C After incubated at 50 degrees C for 4h, the surface displayed lipase retained 23.2% of its full activity, improved a little compared to free Lip2. The surface displayed lipase showed a preference to medium-chain and long-chain fatty acids p-nitrophenyl esters (C8-C16). The cell surface display system based on a-agglutinin is an effective system for displaying Lip2, and the whole cell EBY100-pCTLIP2 will be probably suited to a different range of applications.

  10. Stress-tolerance of baker's-yeast (Saccharomyces cerevisiae) cells: stress-protective molecules and genes involved in stress tolerance.

    PubMed

    Shima, Jun; Takagi, Hiroshi

    2009-05-29

    During the fermentation of dough and the production of baker's yeast (Saccharomyces cerevisiae), cells are exposed to numerous environmental stresses (baking-associated stresses) such as freeze-thaw, high sugar concentrations, air-drying and oxidative stresses. Cellular macromolecules, including proteins, nucleic acids and membranes, are seriously damaged under stress conditions, leading to the inhibition of cell growth, cell viability and fermentation. To avoid lethal damage, yeast cells need to acquire a variety of stress-tolerant mechanisms, for example the induction of stress proteins, the accumulation of stress protectants, changes in membrane composition and repression of translation, and by regulating the corresponding gene expression via stress-triggered signal-transduction pathways. Trehalose and proline are considered to be critical stress protectants, as is glycerol. It is known that these molecules are effective for providing protection against various types of environmental stresses. Modifications of the metabolic pathways of trehalose and proline by self-cloning methods have significantly increased tolerance to baking-associated stresses. To clarify which genes are required for stress tolerance, both a comprehensive phenomics analysis and a functional genomics analysis were carried out under stress conditions that simulated those occurring during the commercial baking process. These analyses indicated that many genes are involved in stress tolerance in yeast. In particular, it was suggested that vacuolar H+-ATPase plays important roles in yeast cells under stress conditions.

  11. High-cell-density fed-batch culture of Saccharomyces cerevisiae KV-25 using molasses and corn steep liquor.

    PubMed

    Vu, Van Hanh; Kim, Keun

    2009-12-01

    High-cell-density cultivation of yeast was investigated using the agricultural waste products corn steep liquor (CSL) and molasses. The Saccharomyces cerevisiae KV-25 cell mass was significantly dependent on the ratio between C and N sources. The concentrations of molasses and CSL in the culture medium were statistically optimized at 10.25% (v/v) and 16.87% (v/v), respectively, by response surface methodology (RSM). Batch culture in a 5-l stirred tank reactor using the optimized medium resulted in a cell mass production of 36.5 g/l. In the fed-batch culture, the feed phase was preceded by a batch phase using the optimized medium, and a very high dried-cell-mass yield of 187.63 g/l was successfully attained by feeding a mixture of 20% (v/v) molasses and 80% (v/v) CSL at a rate of 22 ml/h. In this system, the production of cell mass depended mainly on the agitation speed, the composition of the feed medium, and the glucose level in the medium, but only slightly on the aeration rate.

  12. Flow cytometry and cell sorting of heterogeneous microbial populations: the importance of single-cell analyses.

    PubMed Central

    Davey, H M; Kell, D B

    1996-01-01

    The most fundamental questions such as whether a cell is alive, in the sense of being able to divide or to form a colony, may sometimes be very hard to answer, since even axenic microbial cultures are extremely heterogeneous. Analyses that seek to correlate such things as viability, which is a property of an individual cell, with macroscopic measurements of culture variables such as ATP content, respiratory activity, and so on, must inevitably fail. It is therefore necessary to make physiological measurements on individual cells. Flow cytometry is such a technique, which allows one to analyze cells rapidly and individually and permits the quantitative analysis of microbial heterogeneity. It therefore offers many advantages over conventional measurements for both routine and more exploratory analyses of microbial properties. While the technique has been widely applied to the study of mammalian cells, is use in microbiology has until recently been much more limited, largely because of the smaller size of microbes and the consequently smaller optical signals obtainable from them. Since these technical barriers no longer hold, flow cytometry with appropriate stains has been used for the rapid discrimination and identification of microbial cells, for the rapid assessment of viability and of the heterogeneous distributions of a wealth of other more detailed physiological properties, for the analysis of antimicrobial drug-cell interactions, and for the isolation of high-yielding strains of biotechnological interest. Flow cytometric analyses provide an abundance of multivariate data, and special methods have been devised to exploit these. Ongoing advances mean that modern flow cytometers may now be used by nonspecialists to effect a renaissance in our understanding of microbial heterogeneity. PMID:8987359

  13. A comparative evaluation of different types of microbial electrolysis desalination cells for malic acid production.

    PubMed

    Liu, Guangli; Zhou, Ying; Luo, Haiping; Cheng, Xing; Zhang, Renduo; Teng, Wenkai

    2015-12-01

    The aim of this study was to investigate different microbial electrolysis desalination cells for malic acid production. The systems included microbial electrolysis desalination and chemical-production cell (MEDCC), microbial electrolysis desalination cell (MEDC) with bipolar membrane and anion exchange membrane (BP-A MEDC), MEDC with bipolar membrane and cation exchange membrane (BP-C MEDC), and modified microbial desalination cell (M-MDC). The microbial electrolysis desalination cells performed differently in terms of malic acid production and energy consumption. The MEDCC performed best with the highest malic acid production rate (18.4 ± 0.6 mmol/Lh) and the lowest energy consumption (0.35 ± 0.14 kWh/kg). The best performance of MEDCC was attributable to the neutral pH condition in the anode chamber, the lowest internal resistance, and the highest Geobacter percentage of the anode biofilm population among all the reactors. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Microbial linguistics: perspectives and applications of microbial cell-to-cell communication.

    PubMed

    Mitchell, Robert J; Lee, Sung Kuk; Kim, Taesung; Ghim, Cheol-Min

    2011-01-01

    Inter-cellular communication via diffusible small molecules is a defining character not only of multicellular forms of life but also of single-celled organisms. A large number of bacterial genes are regulated by the change of chemical milieu mediated by the local population density of its own species or others. The cell density-dependent "autoinducer" molecules regulate the expression of those genes involved in genetic competence, biofilm formation and persistence, virulence, sporulation, bioluminescence, antibiotic production, and many others. Recent innovations in recombinant DNA technology and micro-/nano-fluidics systems render the genetic circuitry responsible for cell-to-cell communication feasible to and malleable via synthetic biological approaches. Here we review the current understanding of the molecular biology of bacterial intercellular communication and the novel experimental protocols and platforms used to investigate this phenomenon. A particular emphasis is given to the genetic regulatory circuits that provide the standard building blocks which constitute the syntax of the biochemical communication network. Thus, this review gives focus to the engineering principles necessary for rewiring bacterial chemo-communication for various applications, ranging from population-level gene expression control to the study of host-pathogen interactions.

  15. Microbial fuel cells: novel biotechnology for energy generation.

    PubMed

    Rabaey, Korneel; Verstraete, Willy

    2005-06-01

    Microbial fuel cells (MFCs) provide new opportunities for the sustainable production of energy from biodegradable, reduced compounds. MFCs function on different carbohydrates but also on complex substrates present in wastewaters. As yet there is limited information available about the energy metabolism and nature of the bacteria using the anode as electron acceptor; few electron transfer mechanisms have been established unequivocally. To optimize and develop energy production by MFCs fully this knowledge is essential. Depending on the operational parameters of the MFC, different metabolic pathways are used by the bacteria. This determines the selection and performance of specific organisms. Here we discuss how bacteria use an anode as an electron acceptor and to what extent they generate electrical output. The MFC technology is evaluated relative to current alternatives for energy generation.

  16. Microbial Fuel Cell Possibilities on American Indian Tribal Lands

    SciTech Connect

    Cameron, Kimberlynn

    2016-10-01

    The purpose of this paper is to present a brief background of tribal reservations, the process of how Microbial Fuel Cells (MFCs) work, and the potential benefits of using MFCs on tribal reservations to convert waste water to energy as a means to sustainably generate electricity. There have been no known studies conducted on tribal lands that would be able to add to the estimated percentage of all renewable energy resources identified. Not only does MFC technology provide a compelling, innovative solution, it could also address better management of wastewater, using it as a form of energy generation. Using wastewater for clean energy generation could provide a viable addition to community infrastructure systems improvements.

  17. Fade to Green: A Biodegradable Stack of Microbial Fuel Cells.

    PubMed

    Winfield, Jonathan; Chambers, Lily D; Rossiter, Jonathan; Stinchcombe, Andrew; Walter, X Alexis; Greenman, John; Ieropoulos, Ioannis

    2015-08-24

    The focus of this study is the development of biodegradable microbial fuel cells (MFCs) able to produce useful power. Reactors with an 8 mL chamber volume were designed using all biodegradable products: polylactic acid for the frames, natural rubber as the cation-exchange membrane and egg-based, open-to-air cathodes coated with a lanolin gas diffusion layer. Forty MFCs were operated in various configurations. When fed with urine, the biodegradable stack was able to power appliances and was still operational after six months. One useful application for this truly sustainable MFC technology includes onboard power supplies for biodegradable robotic systems. After operation in remote ecological locations, these could degrade harmlessly into the surroundings to leave no trace when the mission is complete.

  18. Microfluidic microbial fuel cells: from membrane to membrane free

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Ye, Dingding; Li, Jun; Zhu, Xun; Liao, Qiang; Zhang, Biao

    2016-08-01

    Microfluidic microbial fuel cells (MMFCs) are small carbon-neutral devices that use self-organized bacteria to degrade organic substrates and harness energy from the waste water. Conventional MMFCs have made great strides in the past decade and have overcome some limitations, such as high capital costs and low energy output. A co-laminar flow MFC has been first proposed in 2011 with the potential to be an attractively power source to niche applications. Co-laminar MFCs typically operate without any physical membranes separating the reactants, and bacterial ecosystems can be easily manipulated by regulating the inlet conditions. This paper highlights recent accomplishments in the development of co-laminar MFCs, emphasizing basic principles, mass transport and fluid dynamics including boundary layer theory, entrance conditions and mixing zone issues. Furthermore, the development of current techniques, major challenges and the potential research directions are discussed.

  19. Microbial fuel cell treatment of ethanol fermentation process water

    DOEpatents

    Borole, Abhijeet P [Knoxville, TN

    2012-06-05

    The present invention relates to a method for removing inhibitor compounds from a cellulosic biomass-to-ethanol process which includes a pretreatment step of raw cellulosic biomass material and the production of fermentation process water after production and removal of ethanol from a fermentation step, the method comprising contacting said fermentation process water with an anode of a microbial fuel cell, said anode containing microbes thereon which oxidatively degrade one or more of said inhibitor compounds while producing electrical energy or hydrogen from said oxidative degradation, and wherein said anode is in electrical communication with a cathode, and a porous material (such as a porous or cation-permeable membrane) separates said anode and cathode.

  20. Applications of Graphene-Modified Electrodes in Microbial Fuel Cells

    PubMed Central

    Yu, Fei; Wang, Chengxian; Ma, Jie

    2016-01-01

    Graphene-modified materials have captured increasing attention for energy applications due to their superior physical and chemical properties, which can significantly enhance the electricity generation performance of microbial fuel cells (MFC). In this review, several typical synthesis methods of graphene-modified electrodes, such as graphite oxide reduction methods, self-assembly methods, and chemical vapor deposition, are summarized. According to the different functions of the graphene-modified materials in the MFC anode and cathode chambers, a series of design concepts for MFC electrodes are assembled, e.g., enhancing the biocompatibility and improving the extracellular electron transfer efficiency for anode electrodes and increasing the active sites and strengthening the reduction pathway for cathode electrodes. In spite of the challenges of MFC electrodes, graphene-modified electrodes are promising for MFC development to address the reduction in efficiency brought about by organic waste by converting it into electrical energy. PMID:28773929

  1. Bi-directional electrical characterisation of microbial fuel cell.

    PubMed

    Degrenne, N; Ledezma, P; Bevilacqua, P; Buret, F; Allard, B; Greenman, J; Ieropoulos, I A

    2013-01-01

    The electrical performance of microbial fuel cells in steady-state is usually investigated by standard characterisation methods that reveal many important parameters e.g. maximum power. This paper introduces a novel "bi-directional" method to study how the acquisition parameters (i.e. sweep rate and sweep regime) can influence measurements and consequently performance estimations. The investigation exhibited considerable differences (hysteresis) between the forward and backward characterisation regimes, indicating a difficulty to reach steady-state under certain conditions. Moreover, it is found that fast sweep rates (time-step of 2 min) can lead to an overestimation of the short-circuit currents, while prolonged operation with high external loads leads to maximum power overestimation and extended conditioning at high currents can result in its underestimation.

  2. Light energy to bioelectricity: photosynthetic microbial fuel cells.

    PubMed

    Rosenbaum, Miriam; He, Zhen; Angenent, Largus T

    2010-06-01

    Here, we reviewed five different approaches that integrate photosynthesis with microbial fuel cells (MFCs)-photoMFCs. Until now, no conclusive report has been published that identifies direct electron transfer (DET) between a photosynthetic biocatalyst and the anode of a MFC. Therefore, most recent research has been performed to generate sufficient electric current from sunlight with either electrocatalysts or heterotrophic bacteria on the anode to convert photosynthetic products indirectly. The most promising photoMFCs to date are electrocatalytic bioelectrochemical systems (BESs) that convert hydrogen from photosynthesis and sediment-based BESs that can convert excreted organics from cyanobacteria or plants. In addition, illumination on the cathode may provide either oxygen for an electrocatalytic reduction reaction or a promising anoxygenic biocathode.

  3. Performance of Denitrifying Microbial Fuel Cell with Biocathode over Nitrite

    PubMed Central

    Zhao, Huimin; Zhao, Jianqiang; Li, Fenghai; Li, Xiaoling

    2016-01-01

    Microbial fuel cell (MFC) with nitrite as an electron acceptor in cathode provided a new technology for nitrogen removal and electricity production simultaneously. The influences of influent nitrite concentration and external resistance on the performance of denitrifying MFC were investigated. The optimal effectiveness were obtained with the maximum total nitrogen (TN) removal rate of 54.80 ± 0.01 g m−3 d−1. It would be rather desirable for the TN removal than electricity generation at lower external resistance. Denaturing gradient gel electrophoresis suggested that Proteobacteria was the predominant phylum, accounting for 35.72%. Thiobacillus and Afipia might benefit to nitrite removal. The presence of nitrifying Devosia indicated that nitrite was oxidized to nitrate via a biochemical mechanism in the cathode. Ignavibacterium and Anaerolineaceae was found in the cathode as a heterotrophic bacterium with sodium acetate as substrate, which illustrated that sodium acetate in anode was likely permeated through proton exchange membrane to the cathode. PMID:27047462

  4. Scaling up microbial fuel cells and other bioelectrochemical systems.

    PubMed

    Logan, Bruce E

    2010-02-01

    Scientific research has advanced on different microbial fuel cell (MFC) technologies in the laboratory at an amazing pace, with power densities having reached over 1 kW/m(3) (reactor volume) and to 6.9 W/m(2) (anode area) under optimal conditions. The main challenge is to bring these technologies out of the laboratory and engineer practical systems for bioenergy production at larger scales. Recent advances in new types of electrodes, a better understanding of the impact of membranes and separators on performance of these systems, and results from several new pilot-scale tests are all good indicators that commercialization of the technology could be possible within a few years. Some of the newest advances and future challenges are reviewed here with respect to practical applications of these MFCs for renewable energy production and other applications.

  5. Combined bioelectrochemical-electrical model of a microbial fuel cell.

    PubMed

    Recio-Garrido, Dídac; Perrier, Michel; Tartakovsky, Boris

    2016-02-01

    Several recent studies demonstrated significant charge storage in electrochemical biofilms. Aiming to evaluate the impact of charge storage on microbial fuel cell (MFC) performance, this work presents a combined bioelectrochemical-electrical (CBE) model of an MFC. In addition to charge storage, the CBE model is able to describe fast (ms) and slow (days) nonlinear dynamics of MFCs by merging mass and electron balances with equations describing an equivalent electrical circuit. Parameter estimation was performed using results of MFC operation with intermittent (pulse-width modulated) connection of the external resistance. The model was used to compare different methods of selecting external resistance during MFC operation under varying operating conditions. Owing to the relatively simple structure and fast numerical solution of the model, its application for both reactor design and real-time model-based process control applications are envisioned.

  6. Energy harvesting influences electrochemical performance of microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Lobo, Fernanda Leite; Wang, Xin; Ren, Zhiyong Jason

    2017-07-01

    Microbial fuel cells (MFCs) can be effective power sources for remote sensing, wastewater treatment and environmental remediation, but their performance needs significant improvement. This study systematically analyzes how active harvesting using electrical circuits increased MFC system outputs as compared to passive resistors not only in the traditional maximal power point (MPP) but also in other desired operating points such as the maximum current point (MCP) and the maximum voltage point (MVP). Results show that active harvesting in MPP increased power output by 81-375% and active harvesting in MCP increased Coulombic efficiency by 207-805% compared with resisters operated at the same points. The cyclic voltammograms revealed redox potential shifts and supported the performance data. The findings demonstrate that active harvesting is a very effective approach to improve MFC performance across different operating points.

  7. An insight into cathode options for microbial fuel cells.

    PubMed

    Lefebvre, O; Al-Mamun, A; Ooi, W K; Tang, Z; Chua, D H C; Ng, H Y

    2008-01-01

    Microbial fuel cell (MFC) is an emerging and promising technology, particularly in the field of wastewater treatment. The MFC capability of achieving organic removal and generating in situ electricity could make it an attractive alternative wastewater treatment technology over conventional treatment technologies. However, MFC is still far from being economically viable, especially because of the cost of the platinum (Pt) catalyst that makes possible the reaction at the cathode. In this study, we tested alternative cathode catalysts, namely sputter-deposited Cobalt (Co) and denitrifying bacteria (biocathode). The performance of these innovative cathodes was compared with that of classic Pt-cathodes. Co competed well with Pt, but further research is still required for biocathodes. However, biocathodes MFC have showed promise.

  8. Experimenting with microbial fuel cells for powering implanted biomedical devices.

    PubMed

    Roxby, Daniel N; Nham Tran; Pak-Lam Yu; Nguyen, Hung T

    2015-08-01

    Microbial Fuel Cell (MFC) technology has the ability to directly convert sugar into electricity by using bacteria. Such a technology could be useful for powering implanted biomedical devices that require a surgery to replace their batteries every couple of years. In steps towards this, parameters such as electrode configuration, inoculation size, stirring of the MFC and single versus dual chamber reactor configuration were tested for their effect on MFC power output. Results indicate that a Top-Bottom electrode configuration, stirring and larger amounts of bacteria in single chamber MFCs, and smaller amounts of bacteria in dual chamber MFCs give increased power outputs. Finally, overall dual chamber MFCs give s