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Sample records for killer yeast strains

  1. Killer toxin from several food-derived Debaryomyces hansenii strains effective against pathogenic Candida yeasts.

    PubMed

    Banjara, Nabaraj; Nickerson, Kenneth W; Suhr, Mallory J; Hallen-Adams, Heather E

    2016-04-01

    Candida yeasts are the dominant fungi in the healthy human microbiome, but are well-known for causing disease following a variety of perturbations. Evaluation of fungal populations from the healthy human gut revealed a significant negative correlation between the foodborne yeast, Debaryomyces hansenii, and Candida species. D. hansenii is reported to produce killer toxins (mycocins) effective against other yeast species. In order to better understand this phenomenon, a collection of 42 D. hansenii isolates was obtained from 22 cheeses and evaluated for killer activity against Candida albicans and Candida tropicalis over a range of temperatures and pH values. Twenty three strains demonstrated killer activity against both C. albicans and C. tropicalis, which was pH- and temperature-dependent, with no killer activity observed for any strain at pH6.5 or higher, or at ≥35°C (physiological conditions in the human gastrointestinal tract). A cell-free mycocin preparation showed transient killer activity against C. albicans at 35°C and a cheese sample containing a killer D. hansenii strain demonstrated sustained killer activity against both C. albicans and C. tropicalis. Together, these observations raise the possibility that D. hansenii could influence Candida populations in the gut. PMID:26828815

  2. Isolation of a Wickerhamomyces anomalus yeast strain from the sandfly Phlebotomus perniciosus, displaying the killer phenotype.

    PubMed

    Martin, E; Bongiorno, G; Giovati, L; Montagna, M; Crotti, E; Damiani, C; Gradoni, L; Polonelli, L; Ricci, I; Favia, G; Epis, S

    2016-03-01

    The yeast Wickerhamomyces anomalus has been studied for its wide biotechnological potential, mainly for applications in the food industry. Different strains of W. anomalus have been isolated from diverse habitats and recently from insects, including mosquitoes of medical importance. This paper reports the isolation and phylogenetic characterization of W. anomalus from laboratory-reared adults and larvae of Phlebotomus perniciosus (Diptera: Psychodidae), a main phlebotomine vector of human and canine leishmaniasis. Of 65 yeast strains isolated from P. perniciosus, 15 strains were identified as W. anomalus; one of these was tested for the killer phenotype and demonstrated inhibitory activity against four yeast sensitive strains, as reported for mosquito-isolated strains. The association between P. perniciosus and W. anomalus deserves further investigation in order to explore the possibility that this yeast may exert inhibitory/killing activity against Leishmania spp. PMID:26542209

  3. Rapid multiple-level coevolution in experimental populations of yeast killer and nonkiller strains.

    PubMed

    Pieczynska, Magdalena D; Wloch-Salamon, Dominika; Korona, Ryszard; de Visser, J Arjan G M

    2016-06-01

    Coevolution between different biological entities is considered an important evolutionary mechanism at all levels of biological organization. Here, we provide evidence for coevolution of a yeast killer strain (K) carrying cytoplasmic dsRNA viruses coding for anti-competitor toxins and an isogenic toxin-sensitive strain (S) during 500 generations of laboratory propagation. Signatures of coevolution developed at two levels. One of them was coadaptation of K and S. Killing ability of K first increased quickly and was followed by the rapid invasion of toxin-resistant mutants derived from S, after which killing ability declined. High killing ability was shown to be advantageous when sensitive cells were present but costly when they were absent. Toxin resistance evolved via a two-step process, presumably involving the fitness-enhancing loss of one chromosome followed by selection of a recessive resistant mutation on the haploid chromosome. The other level of coevolution occurred between cell and killer virus. By swapping the killer viruses between ancestral and evolved strains, we could demonstrate that changes observed in both host and virus were beneficial only when combined, suggesting that they involved reciprocal changes. Together, our results show that the yeast killer system shows a remarkable potential for rapid multiple-level coevolution. PMID:27168531

  4. Yeast killer systems.

    PubMed Central

    Magliani, W; Conti, S; Gerloni, M; Bertolotti, D; Polonelli, L

    1997-01-01

    The killer phenomenon in yeasts has been revealed to be a multicentric model for molecular biologists, virologists, phytopathologists, epidemiologists, industrial and medical microbiologists, mycologists, and pharmacologists. The surprisingly widespread occurrence of the killer phenomenon among taxonomically unrelated microorganisms, including prokaryotic and eukaryotic pathogens, has engendered a new interest in its biological significance as well as its theoretical and practical applications. The search for therapeutic opportunities by using yeast killer systems has conceptually opened new avenues for the prevention and control of life-threatening fungal diseases through the idiotypic network that is apparently exploited by the immune system in the course of natural infections. In this review, the biology, ecology, epidemiology, therapeutics, serology, and idiotypy of yeast killer systems are discussed. PMID:9227858

  5. Nitrogen availability of grape juice limits killer yeast growth and fermentation activity during mixed-culture fermentation with sensitive commercial yeast strains.

    PubMed Central

    Medina, K; Carrau, F M; Gioia, O; Bracesco, N

    1997-01-01

    The competition between selected or commercial killer strains of type K2 and sensitive commercial strains of Saccharomyces cerevisiae was studied under various conditions in sterile grape juice fermentations. The focus of this study was the effect of yeast inoculation levels and the role of assimilable nitrogen nutrition on killer activity. A study of the consumption of free amino nitrogen (FAN) by pure and mixed cultures of killer and sensitive cells showed no differences between the profiles of nitrogen assimilation in all cases, and FAN was practically depleted in the first 2 days of fermentation. The effect of the addition of assimilable nitrogen and the size of inoculum was examined in mixed killer and sensitive strain competitions. Stuck and sluggish wine fermentations were observed to depend on nitrogen availability when the ratio of killer to sensitive cells was low (1:10 to 1:100). A relationship between the initial assimilable nitrogen content of must and the proportion of killer cells during fermentation was shown. An indirect relationship was found between inoculum size and the percentage of killer cells: a smaller inoculum resulted in a higher proportion of killer cells in grape juice fermentations. In all cases, wines obtained with pure-culture fermentations were preferred to mixed-culture fermentations by sensory analysis. The reasons why killer cells do not finish fermentation under competitive conditions with sensitive cells are discussed. PMID:9212430

  6. A Novel Saccharomyces cerevisiae Killer Strain Secreting the X Factor Related to Killer Activity and Inhibition of S. cerevisiae K1, K2 and K28 Killer Toxins.

    PubMed

    Melvydas, Vytautas; Bružauskaitė, Ieva; Gedminienė, Genovaitė; Šiekštelė, Rimantas

    2016-09-01

    It was determined that Kx strains secrete an X factor which can inhibit all known Saccharomyces cerevisiae killer toxins (K1, K2, K28) and some toxins of other yeast species-the phenomenon not yet described in the scientific literature. It was shown that Kx type yeast strains posess a killer phenotype producing small but clear lysis zones not only on the sensitive strain α'1 but also on the lawn of S. cerevisiae K1, K2 and K28 type killer strains at temperatures between 20 and 30 °C. The pH at which killer/antikiller effect of Kx strain reaches its maximum is about 5.0-5.2. The Kx yeast were identified as to belong to S. cerevisiae species. Another newly identified S. cerevisiae killer strain N1 has killer activity but shows no antikilller properties against standard K1, K2 and K28 killer toxins. The genetic basis for Kx killer/antikiller phenotype was associated with the presence of M-dsRNA which is bigger than M-dsRNA of standard S. cerevisiae K1, K2, K28 type killer strains. Killer and antikiller features should be encoded by dsRNA. The phenomenon of antikiller (inhibition) properties was observed against some killer toxins of other yeast species. The molecular weight of newly identified killer toxins which produces Kx type strains might be about 45 kDa. PMID:27407298

  7. Killer systems of the yeast Saccharomyces cerevisiae

    SciTech Connect

    Nesterova, G.F.

    1989-01-01

    The killer systems of Saccharomyces cerevisiae are an unusual class of cytoplasmic symbionts of primitive eukaryotes. The genetic material of these symbionts is double-stranded RNA. They are characterized by the linearity of the genome, its fragmentation into a major and a minor fraction, which replicate separately, and their ability to control the synthesis of secretory mycocin proteins possessing a toxic action on closely related strains. The secretion of mycocins at the same time ensures acquiring of resistance to them. Strains containing killer symbionts are toxigenic and resistant to the action of their own toxin, but strains that are free of killer double-stranded RNAs are sensitive to the action of mycocins. The killer systems of S. cerevisiae have retained features relating them to viruses and are apparently the result of evolution of infectious viruses. The occurrences of such systems among monocellular eukaryotic organisms is an example of complication of the genome by means of its assembly from virus-like components. We discuss the unusual features of replication and the expression of killer systems and their utilization in the construction of vector molecules.

  8. Biotyping of Malassezia pachydermatis strains using the killer system.

    PubMed

    Coutinho, S D; Paula, C R

    1998-06-01

    The killer phenomenon has been used as epidemiological marker for Candida albicans, where hundreds of biotypes can be obtained. The objective of this study is to observe the behaviour of 30 strains of Malassezia pachydermatis isolated from dogs with otitis (15) or dermatitis (15) against 9 killer yeasts, which, when grouped in triplets produced a 3 digit code (biotype). The growth inhibition of the 30 strains of M. pachydermatis due to the effect of the killer yeasts used permitted the determination of the following biotypes: 888 (33.3%), 212 (26.7%), 111 (16.7%), 312 (6.7%), 512 (6.7%), 242 (3.3%), 311 (3.3%) and 411 (3.3%). Biotypes 888, 212 and 111 occurred most frequently in both ear canal and skin samples. PMID:17655416

  9. K2 killer toxin-induced physiological changes in the yeast Saccharomyces cerevisiae.

    PubMed

    Orentaite, Irma; Poranen, Minna M; Oksanen, Hanna M; Daugelavicius, Rimantas; Bamford, Dennis H

    2016-03-01

    Saccharomyces cerevisiae cells produce killer toxins, such as K1, K2 and K28, that can modulate the growth of other yeasts giving advantage for the killer strains. Here we focused on the physiological changes induced by K2 toxin on a non-toxin-producing yeast strain as well as K1, K2 and K28 killer strains. Potentiometric measurements were adjusted to observe that K2 toxin immediately acts on the sensitive cells leading to membrane permeability. This correlated with reduced respiration activity, lowered intracellular ATP content and decrease in cell viability. However, we did not detect any significant ATP leakage from the cells treated by killer toxin K2. Strains producing heterologous toxins K1 and K28 were less sensitive to K2 than the non-toxin producing one suggesting partial cross-protection between the different killer systems. This phenomenon may be connected to the observed differences in respiratory activities of the killer strains and the non-toxin-producing strain at low pH. This might also have practical consequences in wine industry; both as beneficial ones in controlling contaminating yeasts and non-beneficial ones causing sluggish fermentation. PMID:26818855

  10. Two chromosomal genes required for killing expression in killer strains of Saccharomyces cerevisiae.

    PubMed

    Wickner, R B; Leibowitz, M J

    1976-03-25

    The killer character of yeast is determined by a 1.4 X 10(6) molecular weight double-stranded RNA plasmid and at least 12 chromosomal genes. Wild-type strains of yeast that carry this plasmid (killers) secret a toxin which is lethal only to strains not carrying this plasmid (sensitives).--We have isolated 28 independent recessive chromosomal mutants of a killer strain that have lost the ability to secrete an active toxin but remain resistant to the effects of the toxin and continue to carry the complete cytoplasmic killer genome. These mutants define two complementation groups, kex1 and kex2. Kex1 is located on chromosome VII between ade5 and lys5. Kex2 is located on chromosome XIV, but it does not show meiotic linkage to any gene previously located on this chromosome.--When the killer plasmid of kex1 or kex2 strains is eliminated by curing with heat or cycloheximide, the strains become sensitive to killing. The mutant phenotype reappears among the meiotic segregants in a cross with a normal killer. Thus, the kex phenotype does not require an alteration of the killer plasmid.--Kex1 and kex2 strains each contain near-normal levels of the 1.4 x 10(6) molecular weight double-stranded RNA, whose presence is correlated with the presence of the killer genome. PMID:773743

  11. Isolation, identification, and activity in vitro of killer yeasts against Colletotrichum gloeosporioides isolated from tropical fruits.

    PubMed

    de Lima, Jaqueline Rabelo; Gonçalves, Luciana Rocha Barros; Brandão, Luciana Rocha; Rosa, Carlos Augusto; Viana, Francisco Marto Pinto

    2013-07-01

    A total of 580 yeasts strains, isolated from Ceara State of Brasil, were evaluated for their ability to produce killer toxin. Of these strains, 29 tested positive for the killer phenotype and were further evaluated for their ability to control Colletotrichum gloeosporioides germination in vitro. All yeast strains that expressed the killer phenotype were characterized by sequencing the D1/D2 regions of the large subunit of the rRNA gene. Five yeast strains provided a significant reduction in mycelial growth and conidial germination of C. gloeosporioides in vitro, especially Meyerozyma guilliermondii, which was able to reduce the fungal mycelial growth on solid medium (potato dextrose agar (PDA)) by 60% and block 100% of conidia germination in liquid media (potato dextrose broth (PDB)). Filtering and autoclaving the liquid cultures had no effect on the growth of the pathogen. These results indicate the potential use of antagonist yeasts isolated from tropical fruits in the control of anthracnose caused by C. gloeosporioides in papaya. Further elucidation of main mechanisms involved on anthracnose control by these yeasts could be helpful for the development of biocontrol techniques related to the management of this disease in tropical fruits. PMID:22915228

  12. TdKT, a new killer toxin produced by Torulaspora delbrueckii effective against wine spoilage yeasts.

    PubMed

    Villalba, María Leticia; Susana Sáez, Julieta; Del Monaco, Silvana; Lopes, Christian Ariel; Sangorrín, Marcela Paula

    2016-01-18

    Microbiological spoilage is a major concern throughout the wine industry, and control tools are limited. This paper addresses the identification and partial characterization of a new killer toxin from Torulaspora delbrueckii with potential biocontrol activity of Brettanomyces bruxellensis, Pichia guilliermondii, Pichia manshurica and Pichia membranifaciens wine spoilage. A panel of 18 different wine strains of T. delbrueckii killer yeasts was analysed, and the strain T. delbrueckii NPCC 1033 (TdKT producer) showed a significant inhibitory effect on the growth of all different spoilage yeasts evaluated. The TdKT toxin was then subjected to a partial biochemical characterization. Its estimated molecular weight was N30 kDa and it showed glucanase and chitinase enzymatic activities. The killer activity was stable between pH 4.2 and 4.8 and inactivated at temperature above 40 °C. Pustulan and chitin — but not other cell wall polysaccharides — prevented sensitive yeast cells from being killed by TdKT, suggesting that those may be the first toxin targets in the cell wall. TdKT provoked an increase in necrosis cell death after 3 h treatment and apoptotic cell death after 24 h showing time dependence in its mechanisms of action. Killer toxin extracts were active at oenological conditions, confirming their potential use as a biocontrol tool in winemaking. PMID:26513248

  13. Killer toxin from a novel killer yeast Pichia kudriavzevii RY55 with idiosyncratic antibacterial activity.

    PubMed

    Bajaj, Bijender Kumar; Raina, Sandeepu; Singh, Satbir

    2013-08-01

    The killer phenomenon of yeast may have technological implications in many areas like beverage fermentation, food technology, biological control in agriculture, and in medicine. In the present study the killer phenomenon in Pichia kudriavzevii (P. kudriavzevii RY55) is being reported for the first time. The P. kudriavzevii RY55 toxin exhibited excellent antibacterial activity against several pathogens of human health significance such as Escherichia coli, Enterococcus faecalis, Klebsiella sp., Staphylococcus aureus, Pseudomonas aeruginosa and Pseudomonas alcaligenes. Killer toxin was purified to homogeneity by using ammonium sulphate precipitation and ion exchange chromatography and characterized for few properties. P. kudriavzevii RY55 killer toxin may be of vast significance in the development of novel antimicrobial chemotherapeutic agents, new bio-based safer candidates for food preservation and biocontrol, and starter cultures for fermentation industries. PMID:22961241

  14. Characterization, Ecological Distribution, and Population Dynamics of Saccharomyces Sensu Stricto Killer Yeasts in the Spontaneous Grape Must Fermentations of Southwestern Spain

    PubMed Central

    Maqueda, Matilde; Zamora, Emiliano; Álvarez, María L.

    2012-01-01

    Killer yeasts secrete protein toxins that are lethal to sensitive strains of the same or related yeast species. Among the four types of Saccharomyces killer yeasts already described (K1, K2, K28, and Klus), we found K2 and Klus killer yeasts in spontaneous wine fermentations from southwestern Spain. Both phenotypes were encoded by medium-size double-stranded RNA (dsRNA) viruses, Saccharomyces cerevisiae virus (ScV)-M2 and ScV-Mlus, whose genome sizes ranged from 1.3 to 1.75 kb and from 2.1 to 2.3 kb, respectively. The K2 yeasts were found in all the wine-producing subareas for all the vintages analyzed, while the Klus yeasts were found in the warmer subareas and mostly in the warmer ripening/harvest seasons. The middle-size isotypes of the M2 dsRNA were the most frequent among K2 yeasts, probably because they encoded the most intense K2 killer phenotype. However, the smallest isotype of the Mlus dsRNA was the most frequent for Klus yeasts, although it encoded the least intense Klus killer phenotype. The killer yeasts were present in most (59.5%) spontaneous fermentations. Most were K2, with Klus being the minority. The proportion of killer yeasts increased during fermentation, while the proportion of sensitive yeasts decreased. The fermentation speed, malic acid, and wine organoleptic quality decreased in those fermentations where the killer yeasts replaced at least 15% of a dominant population of sensitive yeasts, while volatile acidity and lactic acid increased, and the amount of bacteria in the tumultuous and the end fermentation stages also increased in an unusual way. PMID:22101056

  15. Using mixed inocula of Saccharomyces cerevisiae killer strains to improve the quality of traditional sparkling-wine.

    PubMed

    Velázquez, Rocío; Zamora, Emiliano; Álvarez, Manuel; Álvarez, María L; Ramírez, Manuel

    2016-10-01

    The quality of traditional sparkling-wine depends on the aging process in the presence of dead yeast cells. These cells undergo a slow autolysis process thereby releasing some compounds, mostly colloidal polymers such as polysaccharides and mannoproteins, which influence the wine's foam properties and mouthfeel. Saccharomyces cerevisiae killer yeasts were tested to increase cell death and autolysis during mixed-yeast-inoculated second fermentation and aging. These yeasts killed sensitive strains in killer plate assays done under conditions of low pH and temperature similar to those used in sparkling-wine making, although some strains showed a different killer behaviour during the second fermentation. The fast killer effect improved the foam quality and mouthfeel of the mixed-inoculated wines, while the slow killer effect gave small improvements over single-inoculated wines. The effect was faster under high-pressure than under low-pressure conditions. Wine quality improvement did not correlate with the polysaccharide, protein, mannan, or aromatic compound concentrations, suggesting that the mouthfeel and foaming quality of sparkling wine are very complex properties influenced by other wine compounds and their interactions, as well as probably by the specific chemical composition of a given wine. PMID:27375256

  16. Yeast K1 killer toxin forms ion channels in sensitive yeast spheroplasts and in artificial liposomes.

    PubMed Central

    Martinac, B; Zhu, H; Kubalski, A; Zhou, X L; Culbertson, M; Bussey, H; Kung, C

    1990-01-01

    The patch-clamp technique was used to examine the plasma membranes of sensitive yeast spheroplasts exposed to partially purified killer toxin preparations. Asolectin liposomes in which the toxin was incorporated were also examined. Excised inside-out patches from these preparations often revealed at 118 pS conductance appearing in pairs. The current through this conductance flickered rapidly among three states: dwelling mostly at the unit-open state, less frequently at the two-unit-open state, and more rarely at the closed state. Membrane voltages from -80 to 80 mV had little influence on the opening probability. The current reversed near the equilibrium potential of K+ in asymmetric KCl solutions and also reversed near O mV at symmetric NaCl vs. KCl solutions. The two levels of the conductance were likely due to the toxin protein, as treatment of spheroplasts or liposomes with extracellular protein preparations from isogenic yeasts deleted for the toxin gene gave no such conductance levels. These results show that in vivo the killer-toxin fraction can form a cation channel that seldom closes regardless of membrane voltage. We suggest that this channel causes the death of sensitive yeast cells. Images PMID:1696721

  17. rRNA fragmentation induced by a yeast killer toxin.

    PubMed

    Kast, Alene; Klassen, Roland; Meinhardt, Friedhelm

    2014-02-01

    Virus like dsDNA elements (VLE) in yeast were previously shown to encode the killer toxins PaT and zymocin, which target distinct tRNA species via specific anticodon nuclease (ACNase) activities. Here, we characterize a third member of the VLE-encoded toxins, PiT from Pichia inositovora, and identify PiOrf4 as the cytotoxic subunit by conditional expression in Saccharomyces cerevisiae. In contrast to the tRNA targeting toxins, however, neither a change of the wobble uridine modification status by introduction of elp3 or trm9 mutations nor tRNA overexpression rescued from PiOrf4 toxicity. Consistent with a distinct RNA target, expression of PiOrf4 causes specific fragmentation of the 25S and 18S rRNA. A stable cleavage product comprising the first ∼ 130 nucleotides of the 18S rRNA was purified and characterized by linker ligation and subsequent reverse transcription; 3'-termini were mapped to nucleotide 131 and 132 of the 18S rRNA sequence, a region showing some similarity to the anticodon loop of tRNA(Glu)(UUC), the zymocin target. PiOrf4 residues Glu9 and His214, corresponding to catalytic sites Glu9 and His209 in the ACNase subunit of zymocin are essential for in vivo toxicity and rRNA fragmentation, raising the possibility of functionally conserved RNase modules in both proteins. PMID:24308908

  18. Hsp12p and PAU genes are involved in ecological interactions between natural yeast strains.

    PubMed

    Rivero, Damaríz; Berná, Luisa; Stefanini, Irene; Baruffini, Enrico; Bergerat, Agnes; Csikász-Nagy, Attila; De Filippo, Carlotta; Cavalieri, Duccio

    2015-08-01

    The coexistence of different yeasts in a single vineyard raises the question on how they communicate and why slow growers are not competed out. Genetically modified laboratory strains of Saccharomyces cerevisiae are extensively used to investigate ecological interactions, but little is known about the genes regulating cooperation and competition in ecologically relevant settings. Here, we present evidences of Hsp12p-dependent altruistic and contact-dependent competitive interactions between two natural yeast isolates. Hsp12p is released during cell death for public benefit by a fast-growing strain that also produces a killer toxin to inhibit growth of a slow grower that can enjoy the benefits of released Hsp12p. We also show that the protein Pau5p is essential in the defense against the killer effect. Our results demonstrate that the combined action of Hsp12p, Pau5p and a killer toxin is sufficient to steer a yeast community. PMID:26079802

  19. Characterization of novel killer toxins secreted by wine-related non-Saccharomyces yeasts and their action on Brettanomyces spp.

    PubMed

    Mehlomakulu, Ngwekazi N; Setati, Mathabatha E; Divol, Benoit

    2014-10-01

    Wine spoilage associated with Brettanomyces bruxellensis is a major concern for winemakers. An effective and reliable method to control the proliferation of this yeast is therefore of utmost importance. To achieve this purpose, sulphur dioxide (SO2) is commonly employed but the efficiency of this chemical compound is subject to wine composition and it can elicit allergic reactions in some consumers. Biological alternatives are therefore actively sought. The current study focused on identifying and characterizing killer toxins which are antimicrobial compounds that show potential in inhibiting B. bruxellensis in wine. Two killer toxins, CpKT1 and CpKT2, from the wine isolated yeast Candida pyralidae were identified and partially characterized. The two proteins had a molecular mass above 50kDa and exhibited killer activity against several B. bruxellensis strains especially in grape juice. They were active and stable at pH3.5-4.5, and temperatures between 15 and 25°C which are compatible with winemaking conditions. Furthermore, the activity of these killer toxins was not affected by the ethanol and sugar concentrations typically found in grape juice and wine. In addition, these killer toxins inhibited neither the Saccharomyces cerevisiae nor the lactic acid bacteria strains tested. These preliminary results indicated that the application of these toxins will have no effect on the main microbial agents that drive alcoholic and malolactic fermentations and further highlight the potential of using these toxins as agents to control the development of B. bruxellensis in grape juice or wine. PMID:25087208

  20. Effects of new Torulaspora delbrueckii killer yeasts on the must fermentation kinetics and aroma compounds of white table wine

    PubMed Central

    Velázquez, Rocío; Zamora, Emiliano; Álvarez, María L.; Hernández, Luis M.; Ramírez, Manuel

    2015-01-01

    Torulaspora delbrueckii is becoming widely recommended for improving some specific characteristics of wines. However, its impact on wine quality is still far from satisfactory at the winery level, mostly because it is easily replaced by Saccharomyces cerevisiae-like yeasts during must fermentation. New T. delbrueckii killer strains were here isolated and selected for winemaking. They killed S. cerevisiae yeasts and were able to dominate and complete the fermentation of sterile grape must. Sequential yeast inoculation of non-sterile white must with T. delbrueckii followed by S. cerevisiae did not ensure T. delbrueckii dominance or wine quality improvement. Only a single initial must inoculation at high cell concentrations allowed the T. delbrueckii killer strains to dominate and complete the must fermentation to reach above 11% ethanol, but not the non-killer strains. None of the wines underwent malolactic fermentation as long as the must had low turbidity and pH. Although no statistically significant differences were found in the wine quality score, the S. cerevisiae-dominated wines were preferred over the T. delbrueckii-dominated ones because the former had high-intensity fresh fruit aromas while the latter had lower intensity, but nevertheless nice and unusual dried fruit/pastry aromas. Except for ethyl propanoate and 3-ethoxy-1-propanol, which were more abundant in the T. delbrueckii–dominated wines, most of the compounds with fresh fruit odor descriptors, including those with the greatest odor activity values (isoamyl acetate, ethyl hexanoate, and ethyl octanoate), were more abundant in the S. cerevisiae–dominated wines. The low relative concentrations of these fruity compounds made it possible to detect in the T. delbrueckii–dominated wines the low-relative-concentration compounds with dried fruit and pastry odors. An example was γ-ethoxy-butyrolactone which was significantly more abundant in these wines than in those dominated by S. cerevisiae. PMID

  1. Modeling competition between yeast strains

    NASA Astrophysics Data System (ADS)

    de Gee, Maarten; van Mourik, Hilda; de Visser, Arjan; Molenaar, Jaap

    2016-04-01

    We investigate toxin interference competition between S. cerevisiae colonies grown on a solid medium. In vivo experiments show that the outcome of this competition depends strongly on nutrient availability and cell densities. Here we present a new model for S. cerevisiae colonies, calculating the local height and composition of the colonies. The model simulates yeast colonies that show a good fit to experimental data. Simulations of colonies that start out with a homogeneous mixture of toxin producing and toxin sensitive cells can display remarkable pattern formation, depending on the initial ratio of the strains. Simulations in which the toxin producing and toxin sensitive species start at nearby positions clearly show that toxin production is advantageous.

  2. Fermentation studies using Saccharomyces diastaticus yeast strains

    SciTech Connect

    Erratt, J.A.; Stewart, G.G.

    1981-01-01

    The yeast species, Saccharomyces diastaticus, has the ability to ferment starch and dextrin, because of the extracellular enzyme, glucoamylase, which hydrolyzes the starch/dextrin to glucose. A number of nonallelic genes--DEX 1, DEX 2, and dextrinase B which is allelic to STA 3--have been isolated, which impart to the yeast the ability to ferment dextrin. Various diploid yeast strains were constructed, each being either heterozygous or homozygous for the individual dextrinase genes. Using 12 (sup 0) plato hopped wort (30% corn adjunct) under agitated conditions, the fermentation rates of the various diploid yeast strains were monitored. A gene-dosage effect was exhibited by yeast strains containing DEX 1 or DEX 2, however, not with yeast strains containing dextrinase B (STA 3). The fermentation and growth rates and extents were determined under static conditions at 14.4 C and 21 C. With all yeast strains containing the dextrinase genes, both fermentation and growth were increased at the higher incubation temperature. Using 30-liter fermentors, beer was produced with the various yeast strains containing the dextrinase genes and the physical and organoleptic characteristics of the products were determined. The concentration of glucose in the beer was found to increase during a 3-mo storage period at 21 C, indicating that the glucoamylase from Saccharomyces diastaticus is not inactivated by pasteurization. (Refs. 36).

  3. Technological properties of indigenous wine yeast strains isolated from wine production regions of Turkey.

    PubMed

    Bağder Elmacı, Simel; Özçelik, Filiz; Tokatlı, Mehmet; Çakır, İbrahim

    2014-05-01

    The purpose of this study was to evaluate the important technological and fermentative properties of wine yeast strains previously isolated from different wine producing regions of Turkey. The determination of the following important properties was made: growth at high temperatures; fermentative capability in the presence of high sugar concentration; fermentation rate; hydrogen sulfide production; killer activity; resistance to high ethanol and sulfur dioxide; foam production; and enzymatic profiles. Ten local wine yeast strains belonging to Saccharomyces, and one commercial active dry yeast as a reference strain were evaluated. Fermentation characteristics were evaluated in terms of kinetic parameters, including ethanol yield (YP/S), biomass yield (YX/S), theoretical ethanol yield (%), specific ethanol production rate (qp; g/gh), specific glucose uptake rate (qs; g/gh), and the substrate conversion (%). All tested strains were able to grow at 37 °C and to start fermentation at 30° Brix, and were resistant to high concentrations of sulfur dioxide. 60 % of the strains were weak H2S producers, while the others produced high levels. Foam production was high, and no strains had killer activity. Six of the tested strains had the ability to grow and ferment at concentrations of 14 % ethanol. Except for one strain, all fermented most of the media sugars at a high rate, producing 11.0-12.4 % (v/v) ethanol. Although all but one strain had suitable characteristics for wine production, they possessed poor activities of glycosidase, esterase and proteinase enzymes of oenological interest. Nine of the ten local yeast strains were selected for their good oenological properties and their suitability as a wine starter culture. PMID:24549515

  4. A new wine Torulaspora delbrueckii killer strain with broad antifungal activity and its toxin-encoding double-stranded RNA virus.

    PubMed

    Ramírez, Manuel; Velázquez, Rocío; Maqueda, Matilde; López-Piñeiro, Antonio; Ribas, Juan C

    2015-01-01

    Wine Torulaspora delbrueckii strains producing a new killer toxin (Kbarr-1) were isolated and selected for wine making. They killed all the previously known Saccharomyces cerevisiae killer strains, in addition to other non-Saccharomyces yeasts. The Kbarr-1 phenotype is encoded by a medium-size 1.7 kb dsRNA, TdV-Mbarr-1, which seems to depend on a large-size 4.6 kb dsRNA virus (TdV-LAbarr) for stable maintenance and replication. The TdV-Mbarr-1 dsRNA was sequenced by new generation sequencing techniques. Its genome structure is similar to those of S. cerevisiae killer M dsRNAs, with a 5'-end coding region followed by an internal A-rich sequence and a 3'-end non-coding region. Mbarr-1 RNA positive strand carries cis acting signals at its 5' and 3' termini for transcription and replication respectively, similar to those RNAs of yeast killer viruses. The ORF at the 5' region codes for a putative preprotoxin with an N-terminal secretion signal, potential Kex2p/Kexlp processing sites, and N-glycosylation sites. No relevant sequence identity was found either between the full sequence of Mbarr-1 dsRNA and other yeast M dsRNAs, or between their respective toxin-encoded proteins. However, a relevant identity of TdV-Mbarr-1 RNA regions to the putative replication and packaging signals of most of the M-virus RNAs suggests that they are all evolutionarily related. PMID:26441913

  5. A new wine Torulaspora delbrueckii killer strain with broad antifungal activity and its toxin-encoding double-stranded RNA virus

    PubMed Central

    Ramírez, Manuel; Velázquez, Rocío; Maqueda, Matilde; López-Piñeiro, Antonio; Ribas, Juan C.

    2015-01-01

    Wine Torulaspora delbrueckii strains producing a new killer toxin (Kbarr-1) were isolated and selected for wine making. They killed all the previously known Saccharomyces cerevisiae killer strains, in addition to other non-Saccharomyces yeasts. The Kbarr-1 phenotype is encoded by a medium-size 1.7 kb dsRNA, TdV-Mbarr-1, which seems to depend on a large-size 4.6 kb dsRNA virus (TdV-LAbarr) for stable maintenance and replication. The TdV-Mbarr-1 dsRNA was sequenced by new generation sequencing techniques. Its genome structure is similar to those of S. cerevisiae killer M dsRNAs, with a 5′-end coding region followed by an internal A-rich sequence and a 3′-end non-coding region. Mbarr-1 RNA positive strand carries cis acting signals at its 5′ and 3′ termini for transcription and replication respectively, similar to those RNAs of yeast killer viruses. The ORF at the 5′ region codes for a putative preprotoxin with an N-terminal secretion signal, potential Kex2p/Kexlp processing sites, and N-glycosylation sites. No relevant sequence identity was found either between the full sequence of Mbarr-1 dsRNA and other yeast M dsRNAs, or between their respective toxin-encoded proteins. However, a relevant identity of TdV-Mbarr-1 RNA regions to the putative replication and packaging signals of most of the M-virus RNAs suggests that they are all evolutionarily related. PMID:26441913

  6. Delimination of brewing yeast strains using different molecular techniques.

    PubMed

    Tornai-Lehoczki, J; Dlauchy, D

    2000-12-01

    In general, the genetic characteristics, the phenotype and the microbial purity of the production brewing yeast strains are among the most important factors in maintaining a consistently good quality of products. Analysis of restriction fragment length polymorphism (RFLP) patterns of 18S rRNA-coding DNA was investigated to group ale and lager strains. All production brewing yeast strains showed the same RFLP pattern as the type strain and synonym type strains of S. cerevisiae, and were quite different from the type and synonym type strains of S. pastorianus. Based on these data, all production brewing yeast strains investigated in this study appeared to belong to S. cerevisiae. Electrophoretic karyotyping and random amplified polymorphic DNA (RAPD) analysis appeared to be suitable methods for distinguishing not only the type and synonym type strain of S. cerevisiae and S. pastorianus, but also the ale and the lager strains. PMID:11139020

  7. Flocculation gene variability in industrial brewer's yeast strains.

    PubMed

    Van Mulders, Sebastiaan E; Ghequire, Maarten; Daenen, Luk; Verbelen, Pieter J; Verstrepen, Kevin J; Delvaux, Freddy R

    2010-12-01

    The brewer's yeast genome encodes a 'Flo' flocculin family responsible for flocculation. Controlled floc formation or flocculation at the end of fermentation is of great importance in the brewing industry since it is a cost-effective and environmental-friendly technique to separate yeast cells from the final beer. FLO genes have the notable capacity to evolve and diverge many times faster than other genes. In actual practice, this genetic variability may directly alter the flocculin structure, which in turn may affect the flocculation onset and/or strength in an uncontrolled manner. Here, 16 ale and lager yeast strains from different breweries, one laboratory Saccharomyces cerevisiae and one reference Saccharomyces pastorianus strain, with divergent flocculation strengths, were selected and screened for characteristic FLO gene sequences. Most of the strains could be distinguished by a typical pattern of these FLO gene markers. The FLO1 and FLO10 markers were only present in five out of the 18 yeast strains, while the FLO9 marker was ubiquitous in all the tested strains. Surprisingly, three strongly flocculating ale yeast strains in this screening also share a typical 'lager' yeast FLO gene marker. Further analysis revealed that a complete Lg-FLO1 allele was present in these ale yeasts. Taken together, this explicit genetic variation between flocculation genes hampers attempts to understand and control the flocculation behavior in industrial brewer's yeasts. PMID:20809075

  8. Whole Genome Analysis of a Wine Yeast Strain

    PubMed Central

    Hauser, Nicole C.; Fellenberg, Kurt; Gil, Rosario; Bastuck, Sonja; Hoheisel, Jörg D.

    2001-01-01

    Saccharomyces cerevisiae strains frequently exhibit rather specific phenotypic features needed for adaptation to a special environment. Wine yeast strains are able to ferment musts, for example, while other industrial or laboratory strains fail to do so. The genetic differences that characterize wine yeast strains are poorly understood, however. As a first search of genetic differences between wine and laboratory strains, we performed DNA-array analyses on the typical wine yeast strain T73 and the standard laboratory background in S288c. Our analysis shows that even under normal conditions, logarithmic growth in YPD medium, the two strains have expression patterns that differ significantly in more than 40 genes. Subsequent studies indicated that these differences correlate with small changes in promoter regions or variations in gene copy number. Blotting copy numbers vs. transcript levels produced patterns, which were specific for the individual strains and could be used for a characterization of unknown samples. PMID:18628902

  9. Biodiversity of brewery yeast strains and their fermentative activities.

    PubMed

    Berlowska, Joanna; Kregiel, Dorota; Rajkowska, Katarzyna

    2015-01-01

    We investigated the genetic, biochemical, fermentative and physiological characteristics of brewery yeast strains and performed a hierarchical cluster analysis to evaluate their similarity. We used five different ale and lager yeast strains, originating from different European breweries and deposited at the National Collection of Yeast Cultures (UK). Ale and lager strains exhibited different genomic properties, but their assimilation profiles and pyruvate decarboxylase activities corresponded to their species classifications. The activity of another enzyme, succinate dehydrogenase, varied between different brewing strains. Our results confirmed that ATP and glycogen content, and the activity of the key metabolic enzymes succinate dehydrogenase and pyruvate decarboxylase, may be good general indicators of cell viability. However, the genetic properties, physiology and fermentation capacity of different brewery yeasts are unique to individual strains. PMID:25267007

  10. A Simple and Reliable Method for Hybridization of Homothallic Wine Strains of Saccharomyces cerevisiae

    PubMed Central

    Ramírez, Manuel; Peréz, Francisco; Regodón, José A.

    1998-01-01

    A procedure was developed for the hybridization and improvement of homothallic industrial wine yeasts. Killer cycloheximide-sensitive strains were crossed with killer-sensitive cycloheximide-resistant strains to get killer cycloheximide-resistant hybrids, thereby enabling hybrid selection and identification. This procedure also allows backcrossing of spore colonies from the hybrids with parental strains. PMID:9835605

  11. Improving industrial yeast strains: exploiting natural and artificial diversity

    PubMed Central

    Steensels, Jan; Snoek, Tim; Meersman, Esther; Nicolino, Martina Picca; Voordeckers, Karin; Verstrepen, Kevin J

    2014-01-01

    Yeasts have been used for thousands of years to make fermented foods and beverages, such as beer, wine, sake, and bread. However, the choice for a particular yeast strain or species for a specific industrial application is often based on historical, rather than scientific grounds. Moreover, new biotechnological yeast applications, such as the production of second-generation biofuels, confront yeast with environments and challenges that differ from those encountered in traditional food fermentations. Together, this implies that there are interesting opportunities to isolate or generate yeast variants that perform better than the currently used strains. Here, we discuss the different strategies of strain selection and improvement available for both conventional and nonconventional yeasts. Exploiting the existing natural diversity and using techniques such as mutagenesis, protoplast fusion, breeding, genome shuffling and directed evolution to generate artificial diversity, or the use of genetic modification strategies to alter traits in a more targeted way, have led to the selection of superior industrial yeasts. Furthermore, recent technological advances allowed the development of high-throughput techniques, such as ‘global transcription machinery engineering’ (gTME), to induce genetic variation, providing a new source of yeast genetic diversity. PMID:24724938

  12. Improving industrial yeast strains: exploiting natural and artificial diversity.

    PubMed

    Steensels, Jan; Snoek, Tim; Meersman, Esther; Picca Nicolino, Martina; Voordeckers, Karin; Verstrepen, Kevin J

    2014-09-01

    Yeasts have been used for thousands of years to make fermented foods and beverages, such as beer, wine, sake, and bread. However, the choice for a particular yeast strain or species for a specific industrial application is often based on historical, rather than scientific grounds. Moreover, new biotechnological yeast applications, such as the production of second-generation biofuels, confront yeast with environments and challenges that differ from those encountered in traditional food fermentations. Together, this implies that there are interesting opportunities to isolate or generate yeast variants that perform better than the currently used strains. Here, we discuss the different strategies of strain selection and improvement available for both conventional and nonconventional yeasts. Exploiting the existing natural diversity and using techniques such as mutagenesis, protoplast fusion, breeding, genome shuffling and directed evolution to generate artificial diversity, or the use of genetic modification strategies to alter traits in a more targeted way, have led to the selection of superior industrial yeasts. Furthermore, recent technological advances allowed the development of high-throughput techniques, such as 'global transcription machinery engineering' (gTME), to induce genetic variation, providing a new source of yeast genetic diversity. PMID:24724938

  13. Quality assessment of lager brewery yeast samples and strains using barley malt extracts with anti-yeast activity.

    PubMed

    van Nierop, Sandra N E; Axcell, Barry C; Cantrell, Ian C; Rautenbach, Marina

    2009-04-01

    Membrane active anti-yeast compounds, such as antimicrobial peptides and proteins, cause yeast membrane damage which is likely to affect yeast vitality and fermentation performance, parameters which are notoriously difficult to analyse. In this work the sensitivity of lager brewery yeast strains towards barley malt extracts with anti-yeast activity was assessed with an optimised assay. It was found that yeast, obtained directly from a brewery, was much more sensitive towards the malt extracts than the same yeast strain propagated in the laboratory. Sensitivity to the malt extracts increased during the course of a laboratory scale fermentation when inoculated with brewery yeast. As the assay was able to differentiate yeast samples with different histories, it shows promise as a yeast quality assay measuring the yeast's ability to withstand stress which can be equated to vitality. The assay was also able to differentiate between different lager yeast strains of Saccharomyces cerevisiae propagated in the laboratory when challenged with a number of malt extracts of varying anti-yeast activity. The assessment of yeast strains in the presence of malt extracts will lead to the identification of yeast strains with improved quality/vitality that can withstand malt-associated anti-yeast activity during brewery fermentations. PMID:19171262

  14. New lager yeast strains generated by interspecific hybridization.

    PubMed

    Krogerus, Kristoffer; Magalhães, Frederico; Vidgren, Virve; Gibson, Brian

    2015-05-01

    The interspecific hybrid Saccharomyces pastorianus is the most commonly used yeast in brewery fermentations worldwide. Here, we generated de novo lager yeast hybrids by mating a domesticated and strongly flocculent Saccharomyces cerevisiae ale strain with the Saccharomyces eubayanus type strain. The hybrids were characterized with respect to the parent strains in a wort fermentation performed at temperatures typical for lager brewing (12 °C). The resulting beers were analysed for sugar and aroma compounds, while the yeasts were tested for their flocculation ability and α-glucoside transport capability. These hybrids inherited beneficial properties from both parent strains (cryotolerance, maltotriose utilization and strong flocculation) and showed apparent hybrid vigour, fermenting faster and producing beer with higher alcohol content (5.6 vs 4.5 % ABV) than the parents. Results suggest that interspecific hybridization is suitable for production of novel non-GM lager yeast strains with unique properties and will help in elucidating the evolutionary history of industrial lager yeast. PMID:25682107

  15. A novel killer protein from Pichia kluyveri isolated from an Algerian soil: purification and characterization of its in vitro activity against food and beverage spoilage yeasts.

    PubMed

    Labbani, Fatima-Zohra Kenza; Turchetti, Benedetta; Bennamoun, Leila; Dakhmouche, Scheherazad; Roberti, Rita; Corazzi, Lanfranco; Meraihi, Zahia; Buzzini, Pietro

    2015-04-01

    A novel killer protein (Pkkp) secreted by a Pichia kluyveri strain isolated from an Algerian soil was active against food and beverage spoilage yeasts of the genera Dekkera, Kluyveromyces, Pichia, Saccharomyces, Torulaspora, Wickerhamomyces and Zygosaccharomyces. After purification by gel filtration chromatography Pkkp revealed an apparent molecular mass of 54 kDa with SDS-PAGE. Minimum inhibitory concentrations (MICs) of purified Pkkp exhibited a high in vitro activity against Dekkera bruxellensis (MICs from 64,000- to 256,000-fold lower than that exhibited by potassium metabisulphite) and Saccharomyces cerevisiae (MICs from 32,000- to 64,000- fold lower than potassium sorbate). No in vitro synergistic interactions (calculated by FIC index - Σ FIC) were observed when Pkkp was used in combination with potassium metabisulphite, potassium sorbate, or ethanol. Pkkp exhibited a dose-response effect against D. bruxellensis and S. cerevisiae in a low-alcoholic drink and fruit juice, respectively. The results of the present study suggest that Pkkp could be proposed as a novel food-grade compound useful for the control of food and beverage spoilage yeasts. PMID:25618417

  16. Persistence in the shadow of killers

    PubMed Central

    Sinclair, Robert M.

    2014-01-01

    Killing is perhaps the most definite form of communication possible. Microbes such as yeasts and gut bacteria have been shown to exhibit killer phenotypes. The killer strains are able to kill other microbes occupying the same ecological niche, and do so with impunity. It would therefore be expected that, wherever a killer phenotype has arisen, all members of the population would soon be killers or dead. Surprisingly, (1) one can find both killer and sensitive strains in coexistence, both in the wild and in in vitro experiments, and (2) the absolute fitness cost of the killer phenotype often seems to be very small. We present an explicit model of such coexistence in a fragmented or discrete environment. A killer strain may kill all sensitive cells in one patch (one piece of rotting fruit, one cave or one human gut, for example), allowing sensitives to exist only in the absence of killer strains on the same patch. In our model, populations spread easily between patches, but in a stochastic manner: one can imagine spores borne by the wind over a field of untended apple trees, or enteric disease transmission in a region in which travel is effectively unrestricted. What we show is that coexistence is not only possible, but that it is possible even if the absolute fitness advantage of the sensitive strain over the killer strain is arbitrarily small. We do this by performing a specifically targeted mathematical analysis on our model, rather than via simulations. Our model does not assume large population densities, and may thus be useful in the context of understanding the ecology of extreme environments. PMID:25071753

  17. Persistence in the shadow of killers.

    PubMed

    Sinclair, Robert M

    2014-01-01

    Killing is perhaps the most definite form of communication possible. Microbes such as yeasts and gut bacteria have been shown to exhibit killer phenotypes. The killer strains are able to kill other microbes occupying the same ecological niche, and do so with impunity. It would therefore be expected that, wherever a killer phenotype has arisen, all members of the population would soon be killers or dead. Surprisingly, (1) one can find both killer and sensitive strains in coexistence, both in the wild and in in vitro experiments, and (2) the absolute fitness cost of the killer phenotype often seems to be very small. We present an explicit model of such coexistence in a fragmented or discrete environment. A killer strain may kill all sensitive cells in one patch (one piece of rotting fruit, one cave or one human gut, for example), allowing sensitives to exist only in the absence of killer strains on the same patch. In our model, populations spread easily between patches, but in a stochastic manner: one can imagine spores borne by the wind over a field of untended apple trees, or enteric disease transmission in a region in which travel is effectively unrestricted. What we show is that coexistence is not only possible, but that it is possible even if the absolute fitness advantage of the sensitive strain over the killer strain is arbitrarily small. We do this by performing a specifically targeted mathematical analysis on our model, rather than via simulations. Our model does not assume large population densities, and may thus be useful in the context of understanding the ecology of extreme environments. PMID:25071753

  18. Applications of mutant yeast strains with low glycogen storage capability

    NASA Technical Reports Server (NTRS)

    Petersen, G. R.; Schubert, W. W.; Stokes, B. O.

    1981-01-01

    Several strains of Hansenula polymorpha were selected for possible low glycogen storage characteristics based on a selective I2 staining procedure. The levels of storage carbohydrates in the mutant strains were found to be 44-70% of the levels in the parent strain for cultures harvested in stationary phase. Similar differences generally were not found for cells harvested in exponential phase. Yeast strains deficient in glycogen storage capability are valuable in increasing the relative protein value of microbial biomass and also may provide significant cost savings in substrate utilization in fermentative processes.

  19. Solving ethanol production problems with genetically modified yeast strains.

    PubMed

    Abreu-Cavalheiro, A; Monteiro, G

    2013-01-01

    The current world demand for bioethanol is increasing as a consequence of low fossil fuel availability and a growing number of ethanol/gasoline flex-fuel cars. In addition, countries in several parts of the world have agreed to reduce carbon dioxide emissions, and the use of ethanol as a fuel (which produces fewer pollutants than petroleum products) has been considered to be a good alternative to petroleum products. The ethanol that is produced in Brazil from the first-generation process is optimized and can be accomplished at low cost. However, because of the large volume of ethanol that is produced and traded each year, any small improvement in the process could represent a savings of billions dollars. Several Brazilian research programs are investing in sugarcane improvement, but little attention has been given to the improvement of yeast strains that participate in the first-generation process at present. The Brazilian ethanol production process uses sugarcane as a carbon source for the yeast Saccharomyces cerevisiae. Yeast is then grown at a high cellular density and high temperatures in large-capacity open tanks with cells recycle. All of these culture conditions compel the yeast to cope with several types of stress. Among the main stressors are high temperatures and high ethanol concentrations inside the fermentation tanks during alcohol production. Moreover, the competition between the desired yeast strains, which are inoculated at the beginning of the process, with contaminants such as wild type yeasts and bacteria, requires acid treatment to successfully recycle the cells. This review is focused on describing the problems and stressors within the Brazilian ethanol production system. It also highlights some genetic modifications that can help to circumvent these difficulties in yeast. PMID:24516432

  20. Solving ethanol production problems with genetically modified yeast strains

    PubMed Central

    Abreu-Cavalheiro, A.; Monteiro, G.

    2013-01-01

    The current world demand for bioethanol is increasing as a consequence of low fossil fuel availability and a growing number of ethanol/gasoline flex-fuel cars. In addition, countries in several parts of the world have agreed to reduce carbon dioxide emissions, and the use of ethanol as a fuel (which produces fewer pollutants than petroleum products) has been considered to be a good alternative to petroleum products. The ethanol that is produced in Brazil from the first-generation process is optimized and can be accomplished at low cost. However, because of the large volume of ethanol that is produced and traded each year, any small improvement in the process could represent a savings of billions dollars. Several Brazilian research programs are investing in sugarcane improvement, but little attention has been given to the improvement of yeast strains that participate in the first-generation process at present. The Brazilian ethanol production process uses sugarcane as a carbon source for the yeast Saccharomyces cerevisiae. Yeast is then grown at a high cellular density and high temperatures in large-capacity open tanks with cells recycle. All of these culture conditions compel the yeast to cope with several types of stress. Among the main stressors are high temperatures and high ethanol concentrations inside the fermentation tanks during alcohol production. Moreover, the competition between the desired yeast strains, which are inoculated at the beginning of the process, with contaminants such as wild type yeasts and bacteria, requires acid treatment to successfully recycle the cells. This review is focused on describing the problems and stressors within the Brazilian ethanol production system. It also highlights some genetic modifications that can help to circumvent these difficulties in yeast. PMID:24516432

  1. Anti-Candida activity and biofilm inhibitory effects of secreted products of tropical environmental yeasts.

    PubMed

    Tan, H W; Tay, S T

    2011-04-01

    This study describes the killer phenotypes of tropical environmental yeasts and the inhibition effects of the culture filtrates on the biofilm of Candida albicans. A total of 26 (10.5%) of 258 yeast isolates obtained from an environmental sampling study demonstrated killer activity to Candida species. The killer yeasts were identified as species belonging to the genus Aureobasidium, Pseudozyma, Ustilago and Candida based on sequence analysis of the ITS1-5.8S-ITS2 region of the yeasts. Pseudozyma showed the broadest killing effects against sensitive strains of Candida. New species of Ustilago and Pseudozyma demonstrating killer phenotypes were identified in this study. Interestingly, more than 50% reduction in the metabolic activity of Candida albicans biofilm was noted after exposure to the culture filtrates of the nine killer yeasts. Purification and characterization of toxin and metabolites are essential for understanding the yeast killing effects. PMID:21602784

  2. Selection of a yeast strain for sweet sorghum fermentation

    SciTech Connect

    Bowling, M. C.

    1982-01-01

    Seven natural and eight commercial yeast strains were tested for fermenting the high sugar content of sweet sorghum juice with a high yield of alcohol and a high pecentage utilization of the sugar within a ten day period. The sorghum juice pH was adjusted to range between 4 and 5. A comparison was made with and without an added nitrogen source. Fermentation temperatures were maintained at 27/sup 0/C. The American Type Culture Collection number 918, a Saccharomyces species fermented the sorghum juice at the 26 and 18 to 20 balling (brix). No yeast strain was found to ferment the 30 balling juice within a ten day period at 90% utilization.

  3. Sake yeast strains have difficulty in entering a quiescent state after cell growth cessation.

    PubMed

    Urbanczyk, Henryk; Noguchi, Chiemi; Wu, Hong; Watanabe, Daisuke; Akao, Takeshi; Takagi, Hiroshi; Shimoi, Hitoshi

    2011-07-01

    Sake yeast strains produce a high concentration of ethanol during sake brewing compared to laboratory yeast strains. As ethanol fermentation by yeast cells continues even after cell growth stops, analysis of the physiological state of the stationary phase cells is very important for understanding the mechanism of producing higher concentrations of ethanol. We compared the physiological characteristics of stationary phase cells of both sake and laboratory yeast strains in an aerobic batch culture and under sake brewing conditions. We unexpectedly found that sake yeast cells in the stationary phase had a lower buoyant density and stress tolerance than did the laboratory yeast cells under both experimental conditions. These results suggest that it is difficult for sake yeast cells to enter a quiescent state after cell growth has stopped, which may be one reason for the higher fermentation rate of sake yeast compared to laboratory yeast strains. PMID:21459038

  4. An indirect assay for volatile compound production in yeast strains

    PubMed Central

    Ravasio, Davide; Walther, Andrea; Trost, Kajetan; Vrhovsek, Urska; Wendland, Jürgen

    2014-01-01

    Traditional flavor analysis relies on gas chromatography coupled to mass spectrometry (GC-MS) methods. Here we describe an indirect method coupling volatile compound formation to an ARO9-promoter-LacZ reporter gene. The resulting β-galactosidase activity correlated well with headspace solid phase micro extraction (HS/SPME) GC-MS data, particularly with respect to the formation of rose flavor. This tool enables large-scale screening of yeast strains and their progeny to identify the most flavor active strains. PMID:24424137

  5. Yeast killer plasmid mutations affecting toxin secretion and activity and toxin immunity function

    SciTech Connect

    Bussey, H.; Sacks, W.; Galley, D.; Saville, D.

    1982-04-01

    M double-stranded RNA (MdsRNA) plasmid mutants were obtained by mutagenesis and screening of a diploid killer culture partially heat cured of the plasmid, so that a high proportion of the cells could be expected to have only one M plasmid. Mutants with neutral (K/sup -/), immune (R/sup +/) or suicide (killer (K/sup +/), sensitive (R/sup -/)) phenotypes were examined. All mutants became K/sup -/ R/sup -/ sensitives on heat curing of the MdsRNA plasmid, and showed cytoplasmic inheritance by random spore analysis. In some cases, M plasmid mutations were indicated by altered mobility of the MdsRNA by agarose gel electrophoresis or by altered size of in vitro translation products from denatured dsRNA. Neutral mutants were of two types: nonsecretors of the toxin protein or secretors of an inactive toxin. Of three neutral nonsecretors examined, one (NLP-1), probably a nonsense mutation, made a smaller protoxin precursor in vitro and in vivo, and two made full-size protoxin molecules. The in vivo protoxin of 43,000 molecular weight was unstable in the wild type and kinetically showed a precursor product relationship to the processed, secreted 11,000-molecular-weight toxin. In one nonsecretor (N1), the protoxin appeared more stable in a pulse-chase experiment, and could be altered in a recognition site required for protein processing.

  6. Yeast strains as potential aroma enhancers in dry fermented sausages.

    PubMed

    Flores, Mónica; Corral, Sara; Cano-García, Liliana; Salvador, Ana; Belloch, Carmela

    2015-11-01

    Actual healthy trends produce changes in the sensory characteristics of dry fermented sausages therefore, new strategies are needed to enhance their aroma. In particular, a reduction in the aroma characteristics was observed in reduced fat and salt dry sausages. In terms of aroma enhancing, generally coagulase-negative cocci were selected as the most important group from the endogenous microbiota in the production of flavour compounds. Among the volatile compounds analysed in dry sausages, ester compounds contribute to fruity aroma notes associated with high acceptance of traditional dry sausages. However, the origin of ester compounds in traditional dry sausages can be due to other microorganisms as lactic acid bacteria, yeast and moulds. Yeast contribution in dry fermented sausages was investigated with opposite results attributed to low yeast survival or low activity during processing. Generally, they affect sausage colour and flavour by their oxygen-scavenging and lipolytic activities in addition to, their ability to catabolize fermentation products such as lactate increasing the pH and contributing to less tangy and more aromatic sausages. Recently, the isolation and characterization of yeast from traditional dry fermented sausages made possible the selection of those with ability to produce aroma active compounds. Molecular methods were used for genetic typing of the isolated yeasts whereas their ability to produce aroma compounds was tested in different systems such as in culture media, in model systems and finally on dry fermented sausages. The results revealed that the appropriate selection of yeast strains with aroma potential may be used to improve the sensory characteristics of reformulated fermented sausages. PMID:25765533

  7. Evaluation of yeast strains for production of fuel ethanol from biomass hydrolysates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Robust industrial yeast strains are needed for profitable production of fuel ethanol from mixed biomass waste. USDA, ARS, NCAUR, RPT has been evaluating ethanol-producing yeasts, including Saccharomyces cerevisiae, engineered GMAX Saccharomyces cerevisiae, irradiated Kluyveromyces marxianus, and Pi...

  8. DNA repair defects sensitize cells to anticodon nuclease yeast killer toxins.

    PubMed

    Klassen, Roland; Wemhoff, Sabrina; Krause, Jens; Meinhardt, Friedhelm

    2011-03-01

    Killer toxins from Kluyveromyces lactis (zymocin) and Pichia acaciae (PaT) were found to disable translation in target cells by virtue of anticodon nuclease (ACNase) activities on tRNA(Glu) and tRNA(Gln), respectively. Surprisingly, however, ACNase exposure does not only impair translation, but also affects genome integrity and concomitantly DNA damage occurs. Previously, it was shown that homologous recombination protects cells from ACNase toxicity. Here, we have analyzed whether other DNA repair pathways are functional in conferring ACNase resistance as well. In addition to HR, base excision repair (BER) and postreplication repair (PRR) promote clear resistance to either, PaT and zymocin. Comparative toxin sensitivity analysis of BER mutants revealed that its ACNase protective function is due to the endonucleases acting on apurinic (AP) sites, whereas none of the known DNA glycosylases is involved. Because PaT and zymocin require the presence of the ELP3/TRM9-dependent wobble uridine modification 5-methoxy-carbonyl-methyl (mcm(5)) for tRNA cleavage, we analyzed toxin response in DNA repair mutants additionally lacking such tRNA modifications. ACNase resistance caused by elp3 or trm9 mutations was found to rescue hypersensitivity of DNA repair defects, consistent with DNA damage to occur as a consequence of tRNA cleavage. The obtained genetic evidence promises to reveal new aspects into the mechanism linking translational fidelity and genome surveillance. PMID:21188417

  9. Alkaline protease production by a strain of marine yeasts

    NASA Astrophysics Data System (ADS)

    Ping, Wang; Zhenming, Chi; Chunling, Ma

    2006-07-01

    Yeast strain 10 with high yield of protease was isolated from sediments of saltern near Qingdao, China. The protease had the highest activity at pH 9.0 and 45°C. The optimal medium for the maximum alkaline protease production of strain 10 was 2.5g soluble starch and 2.0g NaNO3 in 100mL seawater with initial pH 6.0. The optimal cultivation conditions for the maximum protease production were temperature 24.5°C, aeration rate 8.0L min-1 and agitation speed 150r min-1 Under the optimal conditions, 623.1 U mg-1 protein of alkaline protease was reached in the culture within 30h of fermentation.

  10. Separation of similar yeast strains by IEF techniques.

    PubMed

    Horká, Marie; Růzicka, Filip; Holá, Veronika; Slais, Karel

    2009-06-01

    Rapid and reliable identification of the etiological agents of infectious diseases, especially species that are hardly distinguishable by routinely used laboratory methods, e.g. Candida albicans from C. dubliniensis, is necessary for early administration of an appropriate therapy. Similarly, the differentiation between biofilm-positive and biofilm-negative yeast strains is necessary for the choice of a therapeutic strategy due to higher resistance of the biofilm-positive strains to antifungals. In this study rapid separation and identification of similar strains of Candida, cells and/or their lysates, based on IEF are outlined. The isoelectric points of the monitored "similar pairs" of Candidas, C. albicans and C. dubliniensis and the biofilm-positive C. parapsilosis, C. tropicalis and their biofilm-negative strains were determined by CIEF with UV detection in the acidic pH gradient. The differences between their isoelectric points were up to 0.3 units of pI. Simultaneously, a fast and a simple technique was developed for the lysis of the outer membrane cell and characteristic fingerprints were found in lysate electrophoreograms and in gels from the capillary or the gel IEF, respectively. PMID:19526536

  11. Yeast killer toxin-like candidacidal Ab6 antibodies elicited through the manipulation of the idiotypic cascade.

    PubMed

    Polonelli, Luciano; Beninati, Concetta; Teti, Giuseppe; Felici, Franco; Ciociola, Tecla; Giovati, Laura; Sperindè, Martina; Lo Passo, Carla; Pernice, Ida; Domina, Maria; Arigò, Milena; Papasergi, Salvatore; Mancuso, Giuseppe; Conti, Stefania; Magliani, Walter

    2014-01-01

    A mouse anti-anti-anti-idiotypic (Id) IgM monoclonal antibody (mAb K20, Ab4), functionally mimicking a Wyckerhamomyces anomalus (Pichia anomala) killer toxin (KT) characterized by fungicidal activity against yeasts presenting specific cell wall receptors (KTR) mainly constituted by β-1,3-glucan, was produced from animals presenting anti-KT Abs (Ab3) following immunization with a rat IgM anti-Id KT-like mAb (mAb K10, Ab2). MAb K10 was produced by immunization with a KT-neutralizing mAb (mAb KT4, Ab1) bearing the internal image of KTR. MAb K20, likewise mAb K10, proved to be fungicidal in vitro against KT-sensitive Candida albicans cells, an activity neutralized by mAb KT4, and was capable of binding to β-1,3-glucan. MAb K20 and mAb K10 competed with each other and with KT for binding to C. albicans KTR. MAb K20 was used to identify peptide mimics of KTR by the selection of phage clones from random peptide phage display libraries. Using this strategy, four peptides (TK 1-4) were selected and used as immunogen in mice in the form of either keyhole limpet hemocyanin (KLH) conjugates or peptide-encoding minigenes. Peptide and DNA immunization could induce serum Abs characterized by candidacidal activity, which was inhibited by laminarin, a soluble β-1,3-glucan, but not by pustulan, a β-1,6-glucan. These findings show that the idiotypic cascade can not only overcome the barrier of animal species but also the nature of immunogens and the type of technology adopted. PMID:25162681

  12. Increasing alcohol yield by selected yeast fermentation of sweet sorghum. I. Evaluation of yeast strains for ethanol production

    SciTech Connect

    de Mancilha, I.M.; Pearson, A.M.; Waller, J.; Hogaboam, G.J.

    1984-01-01

    A study was conducted for the purpose of evaluating and selecting yeast strains for their ability to produce ethanol using sweet sorghum juice as the substrate. Stalks of sweet sorghum were obtained by cutting off the tops and stripping away the leaves. Fermentation media were prepared by diluting or adding dextrose to the sorghum juice to give a sugar concentration of either 10% (w/v) or 20% (w/v). All yeast strains were first tested in 10% (w/v) total sugar medium. Those strains showing more than 90% sugar conversion efficiency were further tested in 20% (w/v) total sugar medium. Active cultures for inoculation were prepared by growing the yeast strains on the fermentation medium (10% (w/v) total sugar) for 24 h. Then the cultures were added to the fermentation media at a rate of 2%.

  13. Improved microarray methods for profiling the yeast knockout strain collection

    PubMed Central

    Yuan, Daniel S.; Pan, Xuewen; Ooi, Siew Loon; Peyser, Brian D.; Spencer, Forrest A.; Irizarry, Rafael A.; Boeke, Jef D.

    2005-01-01

    A remarkable feature of the Yeast Knockout strain collection is the presence of two unique 20mer TAG sequences in almost every strain. In principle, the relative abundances of strains in a complex mixture can be profiled swiftly and quantitatively by amplifying these sequences and hybridizing them to microarrays, but TAG microarrays have not been widely used. Here, we introduce a TAG microarray design with sophisticated controls and describe a robust method for hybridizing high concentrations of dye-labeled TAGs in single-stranded form. We also highlight the importance of avoiding PCR contamination and provide procedures for detection and eradication. Validation experiments using these methods yielded false positive (FP) and false negative (FN) rates for individual TAG detection of 3–6% and 15–18%, respectively. Analysis demonstrated that cross-hybridization was the chief source of FPs, while TAG amplification defects were the main cause of FNs. The materials, protocols, data and associated software described here comprise a suite of experimental resources that should facilitate the use of TAG microarrays for a wide variety of genetic screens. PMID:15994458

  14. Genetic profiling of yeast industrial strains using in situ comparative genomic hybridization (CGH).

    PubMed

    Wnuk, Maciej; Panek, Anita; Golec, Ewelina; Magda, Michal; Deregowska, Anna; Adamczyk, Jagoda; Lewinska, Anna

    2015-09-20

    The genetic differences and changes in genomic stability may affect fermentation processes involving baker's, brewer's and wine yeast strains. Thus, it seems worthwhile to monitor the changes in genomic DNA copy number of industrial strains. In the present study, we developed an in situ comparative genomic hybridization (CGH) to investigate the ploidy and genetic differences between selected industrial yeast strains. The CGH-based system was validated using the laboratory Saccharomyces cerevisiae yeast strains (haploid BY4741 and diploid BY4743). DNA isolated from BY4743 cells was considered a reference DNA. The ploidy and DNA gains and losses of baker's, brewer's and wine strains were revealed. Taken together, the in situ CGH was shown a helpful molecular tool to identify genomic differences between yeast industrial strains. Moreover, the in situ CGH-based system may be used at the single-cell level of analysis to supplement array-based techniques and high-throughput analyses at the population scale. PMID:26116136

  15. Improvement of Saccharomyces yeast strains used in brewing, wine making and baking.

    PubMed

    Donalies, Ute E B; Nguyen, Huyen T T; Stahl, Ulf; Nevoigt, Elke

    2008-01-01

    Yeast was the first microorganism domesticated by mankind. Indeed, the production of bread and alcoholic beverages such as beer and wine dates from antiquity, even though the fact that the origin of alcoholic fermentation is a microorganism was not known until the nineteenth century. The use of starter cultures in yeast industries became a common practice after methods for the isolation of pure yeast strains were developed. Moreover, effort has been undertaken to improve these strains, first by classical genetic methods and later by genetic engineering. In general, yeast strain development has aimed at improving the velocity and efficiency of the respective production process and the quality of the final products. This review highlights the achievements in genetic engineering of Saccharomyces yeast strains applied in food and beverage industry. PMID:18463806

  16. Molecular polymorphism distribution in phenotypically distinct populations of wine yeast strains.

    PubMed Central

    Nadal, D; Colomer, B; Piña, B

    1996-01-01

    Electrophoretic karyotyping and mitochondrial DNA restriction analysis were used to analyze natural yeast populations from fermenting musts in El Penedès, Spain. Both analyses revealed a considerable degree of polymorphism, indicating heterogeneous natural populations. By specifically designed genetic selection protocols, strains showing potentially interesting phenotypes, such as high tolerance to ethanol and temperature or the ability to grow and to ferment in wine-water-sugar mixtures, were isolated from these natural populations. Genetic analysis showed a strong correlation between the selected phenotypes and mitochondrial DNA polymorphisms. Karyotype analysis revealed several genetically similar yeast lineages in the natural yeast microflora, which we interpret as genetically isolated subpopulations of yeast strains with distinct genetic traits, which may correspond to specific microenvironments. Thus, molecular polymorphism analysis may be useful not only to study the geographical distribution of natural yeast strains but also to identify strains with specific phenotypic properties. PMID:8787392

  17. A NOVEL OLEAGINOUS YEAST STRAIN WITH HIGH LIPID PRODUCTIVITY AND ITS APPLICATION TO ALTERNATIVE BIODIESEL PRODUCTION.

    PubMed

    Areesirisuk, A; Chiu, C H; Yen, T B; Liu, C H; Guo, J H

    2015-01-01

    Five lipid-producing yeast strains, CHC08, CHC11, CHC28, CHC34, and CHC35, were revealed by Sudan Black B staining to contain lipid droplets within cells. Molecular analysis demonstrated that they were 2 strains of Candida parapsilosis, Pseudozyma parantarctica, Pichia manshurica, and Pichia occidentalis. Following batch fermentation, P. parantarctica CHC28 was found to have the highest biomass concentration, total lipids and lipid content levels. The major fatty acids in the lipids of this yeast strain were C16 and C18. Predictions of the properties of yeast biodiesel using linear equations resulted in values similar to biodiesel made from plant oils. Preliminary production of yeast biodiesel from P. parantarctica CHC28 was accomplished through esterification and transesterification reactions. It was found that yeast lipids with high acid value are easily converted to biodiesel at an approximately 90% yield. Therefore, it is possible to use crude lipids as alternative raw materials for biodiesel production. PMID:26353403

  18. Phylogeny-guided screening of yeast strains for lipid production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Oleaginous yeast accumulates greater than 20% of their biomass as triacylglycerol in response to nutritional starvation in the presence of excess carbon source. As such, these yeasts have been suggested as a biocatalyst for converting sugars derived from cellulosic feedstocks into biodiesel. Sever...

  19. Isolation and Characterization of Hydrocarbon-Degrading Yeast Strains from Petroleum Contaminated Industrial Wastewater

    PubMed Central

    Gargouri, Boutheina; Mhiri, Najla; Karray, Fatma; Aloui, Fathi; Sayadi, Sami

    2015-01-01

    Two yeast strains are enriched and isolated from industrial refinery wastewater. These strains were observed for their ability to utilize several classes of petroleum hydrocarbons substrates, such as n-alkanes and aromatic hydrocarbons as a sole carbon source. Phylogenetic analysis based on the D1/D2 variable domain and the ITS-region sequences indicated that strains HC1 and HC4 were members of the genera Candida and Trichosporon, respectively. The mechanism of hydrocarbon uptaking by yeast, Candida, and Trichosporon has been studied by means of the kinetic analysis of hydrocarbons-degrading yeasts growth and substrate assimilation. Biodegradation capacity and biomass quantity were daily measured during twelve days by gravimetric analysis and gas chromatography coupled with mass spectrometry techniques. Removal of n-alkanes indicated a strong ability of hydrocarbon biodegradation by the isolated yeast strains. These two strains grew on long-chain n-alkane, diesel oil, and crude oil but failed to grow on short-chain n-alkane and aromatic hydrocarbons. Growth measurement attributes of the isolates, using n-hexadecane, diesel oil, and crude oil as substrates, showed that strain HC1 had better degradation for hydrocarbon substrates than strain HC4. In conclusion, these yeast strains can be useful for the bioremediation process and decreasing petroleum pollution in wastewater contaminated with petroleum hydrocarbons. PMID:26339653

  20. Isolation and Characterization of Hydrocarbon-Degrading Yeast Strains from Petroleum Contaminated Industrial Wastewater.

    PubMed

    Gargouri, Boutheina; Mhiri, Najla; Karray, Fatma; Aloui, Fathi; Sayadi, Sami

    2015-01-01

    Two yeast strains are enriched and isolated from industrial refinery wastewater. These strains were observed for their ability to utilize several classes of petroleum hydrocarbons substrates, such as n-alkanes and aromatic hydrocarbons as a sole carbon source. Phylogenetic analysis based on the D1/D2 variable domain and the ITS-region sequences indicated that strains HC1 and HC4 were members of the genera Candida and Trichosporon, respectively. The mechanism of hydrocarbon uptaking by yeast, Candida, and Trichosporon has been studied by means of the kinetic analysis of hydrocarbons-degrading yeasts growth and substrate assimilation. Biodegradation capacity and biomass quantity were daily measured during twelve days by gravimetric analysis and gas chromatography coupled with mass spectrometry techniques. Removal of n-alkanes indicated a strong ability of hydrocarbon biodegradation by the isolated yeast strains. These two strains grew on long-chain n-alkane, diesel oil, and crude oil but failed to grow on short-chain n-alkane and aromatic hydrocarbons. Growth measurement attributes of the isolates, using n-hexadecane, diesel oil, and crude oil as substrates, showed that strain HC1 had better degradation for hydrocarbon substrates than strain HC4. In conclusion, these yeast strains can be useful for the bioremediation process and decreasing petroleum pollution in wastewater contaminated with petroleum hydrocarbons. PMID:26339653

  1. Microsatellite marker-based assessment of the biodiversity of native bioethanol yeast strains.

    PubMed

    Antonangelo, Ana Teresa B F; Alonso, Diego P; Ribolla, Paulo E M; Colombi, Débora

    2013-08-01

    Although many Brazilian sugar mills initiate the fermentation process by inoculating selected commercial Saccharomyces cerevisiae strains, the unsterile conditions of the industrial sugar cane ethanol fermentation process permit the constant entry of native yeast strains. Certain of those native strains are better adapted and tend to predominate over the initial strain, which may cause problems during fermentation. In the industrial fermentation process, yeast cells are often exposed to stressful environmental conditions, including prolonged cell recycling, ethanol toxicity and osmotic, oxidative or temperature stress. Little is known about these S. cerevisiae strains, although recent studies have demonstrated that heterogeneous genome architecture is exhibited by some selected well-adapted Brazilian indigenous yeast strains that display high performance in bioethanol fermentation. In this study, 11 microsatellite markers were used to assess the genetic diversity and population structure of the native autochthonous S. cerevisiae strains in various Brazilian sugar mills. The resulting multilocus data were used to build a similarity-based phenetic tree and to perform a Bayesian population structure analysis. The tree revealed the presence of great genetic diversity among the strains, which were arranged according to the place of origin and the collection year. The population structure analysis revealed genotypic differences among populations; in certain populations, these genotypic differences are combined to yield notably genotypically diverse individuals. The high yeast diversity observed among native S. cerevisiae strains provides new insights on the use of autochthonous high-fitness strains with industrial characteristics as starter cultures at bioethanol plants. PMID:23765797

  2. Occurrence and diversity of marine yeasts in Antarctica environments

    NASA Astrophysics Data System (ADS)

    Zhang, Xue; Hua, Mingxia; Song, Chunli; Chi, Zhenming

    2012-03-01

    A total of 28 yeast strains were obtained from the sea sediment of Antarctica. According to the results of routine identification and molecular characterization, the strains belonged to species of Yarrowia lipolytica, Debaryomyces hansenii, Rhodotorula slooffiae, Rhodotorula mucilaginosa, Sporidiobolus salmonicolor, Aureobasidium pullulans, Mrakia frigida and Guehomyces pullulans, respectively. The Antarctica yeasts have wide potential applications in biotechnology, for some of them can produce β-galactosidase and killer toxins.

  3. Yeasts Associated with Culex pipiens and Culex theileri Mosquito Larvae and the Effect of Selected Yeast Strains on the Ontogeny of Culex pipiens.

    PubMed

    Steyn, A; Roets, F; Botha, A

    2016-04-01

    The success of mosquitoes in nature has been linked to their microbiota and bacteria in particular. Yet, knowledge on their symbioses with yeasts is lacking. To explore possible associations, culturable yeasts were isolated from wild larvae of Culex pipiens and Culex theileri. These yeasts were classified using restriction fragment length polymorphism (RFLP) analyses and identified by sequencing the D1/D2 region of the 26S rRNA gene. Representative strains of Candida, Cryptococcus, Galactomyces, Hannaella, Meyerozyma, Pichia, Rhodosporidium, Rhodotorula, Trichosporon and Wickerhamomyces were isolated. Our results provide, to our knowledge, the first records of the yeast microbiota from wild mosquito larvae and show that they may harbour potential clinically relevant yeast species, including the well-known opportunistic human pathogen Candida albicans. Also, diminished numbers of yeast isolates originating from adults, compared to larvae, support the hypothesis of microbial reduction/elimination during adult emergence and extend it to include yeasts. In addition, strains of Candida albicans, Candida glabrata, Candida pseudolambica, Cryptococcus gattii, Metschnikowia bicuspidata, Saccharomyces cerevisiae and Wickerhamomyces anomalus were tested as sole feed during a 21-day feeding experiment wherein cumulative larval growth, survival and pupation of Cx. pipiens were recorded. Although most yeasts supported larval growth in a similar manner to the positive control S. cerevisiae strain, the different yeast strains impacted differently on Culex pipiens ontogeny. Notably, survival and pupation of larvae were negatively impacted by a representative strain of the primary pathogen C. gattii - signifying some yeasts to be natural antagonists of mosquitoes. PMID:26573833

  4. New amylolytic yeast strains for starch and dextrin fermentation. [Schwanniomyces alluvius, Saccharomyces cerevisiae var. diastaticus

    SciTech Connect

    Laluce, C.; Bertolini, M.C.; Ernandes, J.R. ); Martini, A.V.; Martini, A. )

    1988-10-01

    Yeast strains capable of fermenting starch and dextrin to ethanol were isolated from samples collected from Brazilian factories in which cassava flour is produced. Considerable alcohol production was observed for all the strains selected. One strain (DI-10) fermented starch rapidly and secreted 5 times as much amylolytic enzyme than that observed for Schwanniomyces alluvius UCD 54-83. This strain and three other similar isolates were classified as Saccharomyces cerevisiae var. diastaticus by morphological and physiological characteristics and molecular taxonomy.

  5. Mitochondrial-morphology-targeted breeding of industrial yeast strains for alcohol fermentation.

    PubMed

    Kitagaki, Hiroshi

    2009-07-01

    Since mitochondrial genes are repressed under high glucose and low O2, and these conditions correspond to the conditions in which yeast cells are exposed during alcohol fermentation, the existence and structure of yeast mitochondria during alcohol fermentation have not been elucidated. Yeast mitochondria can be observed throughout brewing of sake (Japanese rice wine) and fragment during brewing. Furthermore, it has been revealed that Fis1 [fission 1 (mitochondrial outer membrane) homologue (Saccharomyces cerevisiae)], which is a transmembrane protein with its C-terminal anchor embedded in the outer membrane of mitochondria, is required for fragmentation of yeast mitochondria during sake brewing. By utilizing this knowledge, a fis1 disruptant of a sake yeast strain has been generated that has a networked mitochondrial structure throughout sake brewing. It transpired that this strain produces a high content of malate, which imparts a crisp acidic taste, during sake brewing. This strategy is a useful and a completely novel strategy towards developing a new yeast strain which produces a high content of malate in sake, and mitochondrial morphology has now emerged as a promising target for the breeding of practical industrial strains. PMID:19476438

  6. Comparative genomics of wild type yeast strains unveils important genome diversity

    PubMed Central

    Carreto, Laura; Eiriz, Maria F; Gomes, Ana C; Pereira, Patrícia M; Schuller, Dorit; Santos, Manuel AS

    2008-01-01

    Background Genome variability generates phenotypic heterogeneity and is of relevance for adaptation to environmental change, but the extent of such variability in natural populations is still poorly understood. For example, selected Saccharomyces cerevisiae strains are variable at the ploidy level, have gene amplifications, changes in chromosome copy number, and gross chromosomal rearrangements. This suggests that genome plasticity provides important genetic diversity upon which natural selection mechanisms can operate. Results In this study, we have used wild-type S. cerevisiae (yeast) strains to investigate genome variation in natural and artificial environments. We have used comparative genome hybridization on array (aCGH) to characterize the genome variability of 16 yeast strains, of laboratory and commercial origin, isolated from vineyards and wine cellars, and from opportunistic human infections. Interestingly, sub-telomeric instability was associated with the clinical phenotype, while Ty element insertion regions determined genomic differences of natural wine fermentation strains. Copy number depletion of ASP3 and YRF1 genes was found in all wild-type strains. Other gene families involved in transmembrane transport, sugar and alcohol metabolism or drug resistance had copy number changes, which also distinguished wine from clinical isolates. Conclusion We have isolated and genotyped more than 1000 yeast strains from natural environments and carried out an aCGH analysis of 16 strains representative of distinct genotype clusters. Important genomic variability was identified between these strains, in particular in sub-telomeric regions and in Ty-element insertion sites, suggesting that this type of genome variability is the main source of genetic diversity in natural populations of yeast. The data highlights the usefulness of yeast as a model system to unravel intraspecific natural genome diversity and to elucidate how natural selection shapes the yeast genome

  7. Microarray karyotyping of commercial wine yeast strains reveals shared, as well as unique, genomic signatures

    PubMed Central

    Dunn, Barbara; Levine, R Paul; Sherlock, Gavin

    2005-01-01

    Background Genetic differences between yeast strains used in wine-making may account for some of the variation seen in their fermentation properties and may also produce differing sensory characteristics in the final wine product itself. To investigate this, we have determined genomic differences among several Saccharomyces cerevisiae wine strains by using a "microarray karyotyping" (also known as "array-CGH" or "aCGH") technique. Results We have studied four commonly used commercial wine yeast strains, assaying three independent isolates from each strain. All four wine strains showed common differences with respect to the laboratory S. cerevisiae strain S288C, some of which may be specific to commercial wine yeasts. We observed very little intra-strain variation; i.e., the genomic karyotypes of different commercial isolates of the same strain looked very similar, although an exception to this was seen among the Montrachet isolates. A moderate amount of inter-strain genomic variation between the four wine strains was observed, mostly in the form of depletions or amplifications of single genes; these differences allowed unique identification of each strain. Many of the inter-strain differences appear to be in transporter genes, especially hexose transporters (HXT genes), metal ion sensors/transporters (CUP1, ZRT1, ENA genes), members of the major facilitator superfamily, and in genes involved in drug response (PDR3, SNQ1, QDR1, RDS1, AYT1, YAR068W). We therefore used halo assays to investigate the response of these strains to three different fungicidal drugs (cycloheximide, clotrimazole, sulfomethuron methyl). Strains with fewer copies of the CUP1 loci showed hypersensitivity to sulfomethuron methyl. Conclusion Microarray karyotyping is a useful tool for analyzing the genome structures of wine yeasts. Despite only small to moderate variations in gene copy numbers between different wine yeast strains and within different isolates of a given strain, there was enough

  8. Two-dimensional protein map of an "ale"-brewing yeast strain: proteome dynamics during fermentation.

    PubMed

    Kobi, Dominique; Zugmeyer, Sandra; Potier, Serge; Jaquet-Gutfreund, Laurence

    2004-12-01

    The first protein map of an ale-fermenting yeast is presented in this paper: 205 spots corresponding to 133 different proteins were identified. Comparison of the proteome of this ale strain with a lager brewing yeast and the Saccharomyces cerevisiae strain S288c confirmed that this ale strain is much closer to S288c than the lager strain at the proteome level. The dynamics of the ale-brewing yeast proteome during production-scale fermentation was analysed at the beginning and end of the first and the third usage of the yeast (called generation in the brewing industry). During the first generation, most changes were related to the switch from aerobic propagation to anaerobic fermentation. Fewer changes were observed during the third generation but certain stress-response proteins such as Hsp26p, Ssa4p and Pnc1p exhibited constitutive expression in subsequent generations. The ale brewing yeast strain appears to be quite well adapted to fermentation conditions and stresses. PMID:15556083

  9. The effect of linoleic acid on the Sauvignon blanc fermentation by different wine yeast strains.

    PubMed

    Casu, Francesca; Pinu, Farhana R; Fedrizzi, Bruno; Greenwood, David R; Villas-Boas, Silas G

    2016-08-01

    The level of linoleic acid in the Sauvignon blanc (SB) grape juice affects the development of different aroma compounds during fermentation by Saccharomyces cerevisiae EC1118, including key varietal thiols such as 3-mercaptohexanol (3MH) and 3-mercaptohexyl acetate (3MHA). However, it is still unknown if linoleic acid would affect in a similar way other commonly used S. cerevisiae wine strains. Here we investigated the effect of grape juice linoleic acid on the development of aroma compounds and other metabolites of SB wines using different wine yeast strains: EC1118, AWRI796 and VIN13. Linoleic acid clearly affected the levels of acetylated aroma compounds, several amino acids, and antioxidant molecules, independent of yeast strain, but the production of 3MH was affected by linoleic acid in a strain-specific manner. Moreover, the supplementation of deuterium-labelled 3MH also affected the production of varietal thiols in a strain-specific way. Linoleic acid reduced the acetylation process probably by inhibiting an acetyltransferase, an effect that was independent of the yeast strain. However, regulation of the 3MH biosynthesis is strain-specific, which suggests a mindful consideration not only towards the wine yeast but also to the linoleic acid concentration in the grape juice in order to obtain the desired wine aroma characteristics. PMID:27364827

  10. Draft genome sequence of the dimorphic yeast Yarrowia lipolytica, strain W29

    SciTech Connect

    Pomraning, Kyle R.; Baker, Scott E.

    2015-11-25

    Here we present the draft genome sequence of the dimorphic ascomycete yeast Yarrowia lipolytica strain W29 (ATCC20460TM). Y. lipolytica is a commonly employed model for industrial production of lipases, small molecules, and more recently for its ability to accumulate lipids. It has also been used to study genome evolution in yeast and filamentous fungi due to its position as an early diverging branch of the subphylum Sacchromycotina.

  11. Selection of Yarrowia lipolytica strains with high protein content from yeasts isolated from different marine environments

    NASA Astrophysics Data System (ADS)

    Chi, Zhenming; Wang, Fang; Wang, Lin; Li, Jing; Wang, Xianghong

    2007-10-01

    A total of 78 Yarrowia lipolytica yeast strains from seawater, sediments, mud of salterns, the guts of marine fish, and marine algae were obtained. After the crude protein of the yeasts was estimated by the method of Kjehldahl, we found that seven strains of the marine yeasts grown in soy bean cake hydrolysate with 20 g L-1 of glucose for 48 h at 28°C contained more than 41.0 g protein per 100 g of cell dry weight and the cell dry weight was more than 4.4 g per L of the culture. Among them, strain SWJ-1b contained the highest crude protein. The results of Biolog identification and molecular methods further confirmed that they indeed belonged to Y. lipolytica.

  12. PCR differentiation of commercial yeast strains using intron splice site primers.

    PubMed Central

    de Barros Lopes, M; Soden, A; Henschke, P A; Langridge, P

    1996-01-01

    The increased use of pure starter cultures in the wine industry has made it necessary to develop a rapid and simple identification system for yeast strains. A method based upon the PCR using oligonucleotide primers that are complementary to intron splice sites has been developed. Since most introns are not essential for gene function, introns have evolved with minimal constraint. By targeting these highly variable sequences, the PCR has proved to be very effective in uncovering polymorphisms in commercial yeast strains. The speed of the method and the ability to analyze many samples in a single day permit the monitoring of specific yeast strains during fermentations. Furthermore, the simplicity of the technique, which does not require the isolation of DNA, makes it accessible to industrial laboratories that have limited molecular expertise and resources. PMID:8953723

  13. Rapid and marker-free refactoring of xylose-fermenting yeast strains with Cas9/CRISPR.

    PubMed

    Tsai, Ching-Sung; Kong, In Iok; Lesmana, Anastashia; Million, Gyver; Zhang, Guo-Chang; Kim, Soo Rin; Jin, Yong-Su

    2015-11-01

    Genomic integration of expression cassettes containing heterologous genes into yeast with traditional methods inevitably deposits undesirable genetic elements into yeast chromosomes, such as plasmid-borne multiple cloning sites, antibiotic resistance genes, Escherichia coli origins, and yeast auxotrophic markers. Specifically, drug resistance genes for selecting transformants could hamper further industrial usage of the resulting strains because of public health concerns. While we constructed an efficient and rapid xylose-fermenting Saccharomyces cerevisiae, the engineered strain (SR8) might not be readily used for a large-scale fermentation because the SR8 strain contained multiple copies of drug resistance genes. We utilized the Cas9/CRISPR-based technique to refactor an efficient xylose-fermenting yeast strain without depositing any undesirable genetic elements in resulting strains. In order to integrate genes (XYL1, XYL2, and XYL3) coding for xylose reductase, xylitol dehydrogenase, and xylulokinase from Scheffersomyces stipitis, and delete both PHO13 and ALD6, a double-strand break formation by Cas9 and its repair by homologous recombination were exploited. Specifically, plasmids containing guide RNAs targeting PHO13 and ALD6 were sequentially co-transformed with linearized DNA fragments containing XYL1, XYL2, and XYL3 into S. cerevisiae expressing Cas9. As a result, two copies of XYL1, XYL2, and XYL3 were integrated into the loci of PHO13 and ALD6 for achieving overexpression of heterologous genes and knockout of endogenous genes simultaneously. With further prototrophic complementation, we were able to construct an engineered strain exhibiting comparable xylose fermentation capabilities with SR8 within 3 weeks. We report a detailed procedure for refactoring xylose-fermenting yeast using any host strains. The refactored strains using our procedure could be readily used for large-scale fermentations since they have no antibiotic resistant markers. PMID

  14. A yeast killer toxin screen provides insights into A/B toxin entry, trafficking and killing mechanisms

    PubMed Central

    Carroll, Susheela Y.; Stirling, Peter C.; Stimpson, Helen E. M.; Gießelmann, Esther; Schmitt, Manfred J.; Drubin, David G.

    2009-01-01

    Summary Like Ricin, Shiga, and Cholera toxins, yeast K28 is an A/B toxin that depends on endocytosis and retrograde trafficking for toxicity. Knowledge of the specific proteins, lipids, and mechanisms required for trafficking and killing by these toxins remains incomplete. Since K28 is a model for clinically relevant toxins, we screened over 5000 yeast mutants, identifying 365 that affect K28 sensitivity. Hypersensitive mutants revealed cytoprotective pathways, including stress-activated signaling and protein degradation. Resistant mutants clustered to endocytic, lipid organization and cell wall biogenesis pathways. Furthermore, GPI anchors and transcriptional regulation are important for K28-cell binding. Strikingly, the AP2 complex, which in metazoans links endocytic cargo to the clathrin coat, but had no assigned function in yeast, was critical for K28 toxicity. Yeast AP2 localizes to endocytic sites and has a cargo-specific function in K28 uptake. This comprehensive genetic analysis identified conserved processes important for A/B toxin trafficking and killing. PMID:19853568

  15. Monitoring S phase progression globally and locally using BrdU incorporation in TK+ yeast strains

    PubMed Central

    Lengronne, Armelle; Pasero, Philippe; Bensimon, Aaron; Schwob, Etienne

    2001-01-01

    Eukaryotic chromosome replication is initiated from numerous origins and its activation is temporally controlled by cell cycle and checkpoint mechanisms. Yeast has been very useful in defining the genetic elements required for initiation of DNA replication, but simple and precise tools to monitor S phase progression are lacking in this model organism. Here we describe a TK+ yeast strain and conditions that allow incorporation of exogenous BrdU into genomic DNA, along with protocols to detect the sites of DNA synthesis in yeast nuclei or on combed DNA molecules. S phase progression is monitored by quantification of BrdU in total yeast DNA or on individual chromosomes. Using these tools we show that yeast chromosomes replicate synchronously and that DNA synthesis occurs at discrete subnuclear foci. Analysis of BrdU signals along single DNA molecules from hydroxyurea-arrested cells reveals that replication forks stall 8–9 kb from origins that are placed 46 kb apart on average. Quantification of total BrdU incorporation suggests that 190 ‘early’ origins have fired in these cells and that late replicating territories might represent up to 40% of the yeast genome. More generally, the methods outlined here will help understand the kinetics of DNA replication in wild-type yeast and refine the phenotypes of several mutants. PMID:11266543

  16. Ethanol production characteristics for a respiratory deficient mutant yeast strain

    SciTech Connect

    Garcia, A. III; Grilione, P.

    1982-01-01

    Barley was fermented with a defined strain of Saccharomyces cerevisiae and a chemical induced respiratory deficient mutant RD, specific gravity, pH, CO/sub 2/ production and ethanol production rates and yield were compared. RD fermentation were slower but yielded slightly more ethanol after a considerable time. Partial reversion to a respiratory capable strain occurred.

  17. Relationship between ethanol and oxidative stress in laboratory and brewing yeast strains.

    PubMed

    Bleoanca, Iulia; Silva, Ana Rita Courelas; Pimentel, Catarina; Rodrigues-Pousada, Claudina; Menezes, Regina de Andrade

    2013-12-01

    Ethanol is a chemical stress factor that inhibits cellular growth and determines metabolic changes leading to reduction of cell viability during fermentation and yeast storage. To determine the effect of time, temperature and ethanol during storage of brewing yeasts we have monitored viability of cells stored for 72 h, at 6 °C or 12 °C, in the presence of various ethanol concentrations. Under the conditions tested, 6 °C is the most favourable temperature to store brewing yeast creams emphasizing the importance of a tight temperature control in the storage vessels. Because W210 is less resistant to storage in the presence of ethanol than W34/70, the optimal storage parameters obtained under our laboratory conditions vary significantly. The ale strain is sensitive to storage under ethanol concentrations higher than 5% (v/v) for more than 48 h at 6 °C whereas at the same temperature the lager strain tolerates ethanol up to 7.5% (v/v) for 72 h. Also, the viability assays indicate that the antioxidant protein Yap1 is an important factor to storage resistance of BY4741 laboratory strain. To investigate the molecular mechanisms underlying tolerance of brewing yeast strains to ethanol, we have performed phenotypic analysis, localization studies and have monitored the activation of antioxidant and protection genes as well as the intracellular contents of glycogen and trehalose. Overall, our data suggest that the ale strain W210 has a defective antioxidant defence system and that ethanol may induce the antioxidant defences as well as glycogen and trehalose protection mechanisms in laboratory and brewing yeast strains. PMID:23838012

  18. Draft Genome Sequence of the Probiotic Yeast Saccharomyces cerevisiae var. boulardii Strain ATCC MYA-796

    PubMed Central

    Marques, E. T. A.; Franco, G. R.

    2014-01-01

    Saccharomyces boulardii is the only yeast approved as a probiotic for human consumption. Here, we report the draft genome sequence of the strain ATCC MYA-796, derived from the French Ultra Levure probiotic drug. The genome has a size of 11.6 Mb with 5,305 putative open reading frames predicted. PMID:25523784

  19. Characterization of yeast strains for wine production: effect of fermentation variables on quality of wine produced.

    PubMed

    Ndip, R N; Akoachere, J F; Dopgima, L L; Ndip, L M

    2001-09-01

    Sixteen yeast strains isolated from grapefruit (Citrus paradis), orange (Citrus sinensis) and pineapple (Ananas comosus) were characterized using standard microbiological procedures. The species were identified as Saccharomyces uvarum, S. cerevisiae, S. carlbergensis, and S. ellipsoideus. Their abilities for wine production were tested by using sugar and ethanol tolerance tests. The best biochemically active strain, S. ellipsoideus, was used along with commercially available baker's yeast (S. cerevisiae) to produce wine from grapefruit, orange, and pineapple juices. After fermentation for 14 d with S. cerevisiae and 21 d with S. ellipsoideus, wines produced were compared with Baron de Valls (standard). The highest (10.47% [v/v]) and lowest (7.68% [v/v]) alcohol concentrations with corresponding residual sugar concentrations of 1.88% (w/v) and 7.7% (w/v) were produced from orange after fermentation with S. cerevisiae and S. ellipsoideus, respectively. S. ellipsoideus was found to be the best yeast strain producing wine with the highest acceptable score of 7.41 from orange. The study revealed the possibility of producing wine from our locally available fruits using simple, cheap, and adaptable technology with biochemically characterized yeast strains. PMID:11732717

  20. Draft Genome Sequence of the Dimorphic Yeast Yarrowia lipolytica Strain W29

    PubMed Central

    Pomraning, Kyle R.

    2015-01-01

    Here, we present the draft genome sequence of the dimorphic ascomycete yeast Yarrowia lipolytica strain W29 (ATCC 20460). Y. lipolytica is a commonly employed model for the industrial production of lipases, small molecules, and more recently for its ability to accumulate lipids. PMID:26607882

  1. Draft Genome Sequence of the Dimorphic Yeast Yarrowia lipolytica Strain W29.

    PubMed

    Pomraning, Kyle R; Baker, Scott E

    2015-01-01

    Here, we present the draft genome sequence of the dimorphic ascomycete yeast Yarrowia lipolytica strain W29 (ATCC 20460). Y. lipolytica is a commonly employed model for the industrial production of lipases, small molecules, and more recently for its ability to accumulate lipids. PMID:26607882

  2. Identification of Chemical-Genetic Interactions via Parallel Analysis of Barcoded Yeast Strains.

    PubMed

    Suresh, Sundari; Schlecht, Ulrich; Xu, Weihong; Miranda, Molly; Davis, Ronald W; Nislow, Corey; Giaever, Guri; St Onge, Robert P

    2016-01-01

    The Yeast Knockout Collection is a complete set of gene deletion strains for the budding yeast, Saccharomyces cerevisiae In each strain, one of approximately 6000 open-reading frames is replaced with a dominant selectable marker flanked by two DNA barcodes. These barcodes, which are unique to each gene, allow the growth of thousands of strains to be individually measured from a single pooled culture. The collection, and other resources that followed, has ushered in a new era in chemical biology, enabling unbiased and systematic identification of chemical-genetic interactions (CGIs) with remarkable ease. CGIs link bioactive compounds to biological processes, and hence can reveal the mechanism of action of growth-inhibitory compounds in vivo, including those of antifungal, antibiotic, and anticancer drugs. The chemogenomic profiling method described here measures the sensitivity induced in yeast heterozygous and homozygous deletion strains in the presence of a chemical inhibitor of growth (termed haploinsufficiency profiling and homozygous profiling, respectively, or HIPHOP). The protocol is both scalable and amenable to automation. After competitive growth of yeast knockout collection cultures, with and without chemical inhibitors, CGIs can be identified and quantified using either array- or sequencing-based approaches as described here. PMID:27587778

  3. Effect of yeast assimilable nitrogen on the synthesis of phenolic aroma compounds by Hanseniaspora vineae strains.

    PubMed

    Martin, Valentina; Boido, Eduardo; Giorello, Facundo; Mas, Albert; Dellacassa, Eduardo; Carrau, Francisco

    2016-07-01

    In several grape varieties, the dominating aryl alkyl alcohols found are the volatile group of phenylpropanoid-related compounds, such as glycosylated benzyl and 2-phenylethyl alcohol, which contribute to wine with floral and fruity aromas after being hydrolysed during fermentation. Saccharomyces cerevisiae is largely recognized as the main agent in grape must fermentation, but yeast strains belonging to other genera, including Hanseniaspora, are known to predominate during the first stages of alcoholic fermentation. Although non-Saccharomyces yeast strains have a well-recognized genetic diversity, understanding of their impact on wine flavour richness is still emerging. In this study, 11 Hansenisapora vineae strains were used to ferment a chemically defined simil-grape fermentation medium, resembling the nutrient composition of grape juice but devoid of grape-derived secondary metabolites. GC-MS analysis was performed to determine volatile compounds in the produced wines. Our results showed that benzyl alcohol, benzyl acetate and 2-phenylethyl acetate are significantly synthesized by H. vineae strains. Levels of these compounds found in fermentations with 11 H. vineae different strains were one or two orders of magnitude higher than those measured in fermentations with a known S. cerevisiae wine strain. The implications for winemaking in response to the negative correlation of benzyl alcohol, benzyl acetate and 2-phenylethyl acetate production with yeast assimilable nitrogen concentrations are discussed. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26945700

  4. Evaluation and characterization of new α-L-rhamnosidase-producing yeast strains.

    PubMed

    Singh, Pratiksha; Sahota, Param Pal; Singh, Rajesh Kumar

    2015-01-01

    A total of thirty yeast strains were isolated from a whey beverage and screened for α-L-rhamnosidase enzyme production. Of these, only four isolates were capable of producing the α-L-rhamnosidase enzyme by hydrolyzing naringin. Scanning electron microscopy images showed that the morphology of the yeast isolate (isolate No. 84) producing the greatest enzyme, changed from oval to filamentous in the presence of naringin. On the basis of morphological and molecular characterization (ITS sequencing), these four isolates were identified as Clavispora lusitaniae-84, Clavispora lusitaniae-B82, Candida sp.-86 and Candida hyderabadensis-S82). Fermentation parameters and the biochemical characterization of the α-L-rhamnosidase-producing yeast isolates were studied based on carbon substrate utilization profiles using BIOLOG phenotype microarray plates. Intra-species genetic diversity among the isolates was evaluated by whole genome analysis with repetitive DNA sequences (ERIC, REP and BOX) based DNA fingerprinting. On the basis of these results, it was found that these isolates of yeast producing L-rhamnosidase have a great potential application for beverage quality enhancement, and can build a strong foundation of α-L-rhamnosidase-producing yeast strains in the debittering of citrus juice. PMID:26582283

  5. Near-freezing effects on the proteome of industrial yeast strains of Saccharomyces cerevisiae.

    PubMed

    Ballester-Tomás, Lidia; Pérez-Torrado, Roberto; Rodríguez-Vargas, Sonia; Prieto, Jose A; Randez-Gil, Francisca

    2016-03-10

    At near-freezing temperatures (0-4°C), the growth of the yeast Saccharomyces cerevisiae stops or is severely limited, and viability decreases. Under these conditions, yeast cells trigger a biochemical response, in which trehalose and glycerol accumulate and protect them against severe cold and freeze injury. However, the mechanisms that allow yeast cells to sustain this response have been not clarified. The effects of severe cold on the proteome of S. cerevisiae have been not investigated and its importance in providing cell survival at near-freezing temperatures and upon freezing remains unknown. Here, we have compared the protein profile of two industrial baker's yeast strains at 30°C and 4°C. Overall, a total of 16 proteins involved in energy-metabolism, translation and redox homeostasis were identified as showing increased abundance at 4°C. The predominant presence of glycolytic proteins among those upregulated at 4°C, likely represents a mechanism to maintain a constant supply of ATP for the synthesis of glycerol and other protective molecules. Accumulation of these molecules is by far the most important component in enhancing viability of baker's yeast strains upon freezing. Overexpression of genes encoding certain proteins associated with translation or redox homeostasis provided specifically protection against extreme cold damage, underlying the importance of these functions in the near-freezing response. PMID:26812658

  6. Transcriptional Regulation and the Diversification of Metabolism in Wine Yeast Strains

    PubMed Central

    Rossouw, Debra; Jacobson, Dan; Bauer, Florian F.

    2012-01-01

    Transcription factors and their binding sites have been proposed as primary targets of evolutionary adaptation because changes to single transcription factors can lead to far-reaching changes in gene expression patterns. Nevertheless, there is very little concrete evidence for such evolutionary changes. Industrial wine yeast strains, of the species Saccharomyces cerevisiae, are a geno- and phenotypically diverse group of organisms that have adapted to the ecological niches of industrial winemaking environments and have been selected to produce specific styles of wine. Variation in transcriptional regulation among wine yeast strains may be responsible for many of the observed differences and specific adaptations to different fermentative conditions in the context of commercial winemaking. We analyzed gene expression profiles of wine yeast strains to assess the impact of transcription factor expression on metabolic networks. The data provide new insights into the molecular basis of variations in gene expression in industrial strains and their consequent effects on metabolic networks important to wine fermentation. We show that the metabolic phenotype of a strain can be shifted in a relatively predictable manner by changing expression levels of individual transcription factors, opening opportunities to modify transcription networks to achieve desirable outcomes. PMID:22042577

  7. Use of an acidophilic yeast strain to enable the growth of leaching bacteria on solid media.

    PubMed

    Ngom, Baba; Liang, Yili; Liu, Yi; Yin, Huaqun; Liu, Xueduan

    2015-03-01

    In this study, a Candida digboiensis strain was isolated from a heap leaching plant in Zambia and used in double-layer agar plate to efficiently isolate and purify leaching bacteria. Unlike Acidiphilium sp., the yeast strain was tetrathionate tolerant and could metabolize a great range of organic compounds including organic acids. These properties allowed the yeast strain to enable and fasten the growth of iron and sulfur oxidizers on double-layer agar plate. The isolates were identified as Acidithiobacillus ferrooxidans FOX1, Leptospirillun ferriphilum BN, and Acidithiobacillus thiooxidans ZMB. These three leaching bacteria were inhibited by organic acids such as acetic and propionic acids; however, their activities were enhanced by Candida digboiensis NB under dissolved organic matter stress. PMID:25347960

  8. Antifungal activity of chalcones: a mechanistic study using various yeast strains.

    PubMed

    Lahtchev, K L; Batovska, D I; Parushev, St P; Ubiyvovk, V M; Sibirny, A A

    2008-10-01

    We reported the synthesis, antifungal evaluation and study on substituent effects of 21 chalcones. A lot of genetically defined strains belonging to different yeast genera and species, namely Saccharomyces cerevisiae, Hansenula polymorpha and Kluyveromyces lactis, were used as test organisms. Concerning the mode of the antifungal action of chalcones it was shown that DNA was probably not the main target for the chalcones. It was revealed that the yeast's intracellular glutathione and cysteine molecules play significant role as defence barrier against the chalcone action. It was also shown that chalcones may react with some proteins involved in cell separation. PMID:18280009

  9. Characterization of genome-reduced fission yeast strains

    PubMed Central

    Sasaki, Mayumi; Kumagai, Hiromichi; Takegawa, Kaoru; Tohda, Hideki

    2013-01-01

    The Schizosaccharomyces pombe genome is one of the smallest among the free-living eukaryotes. We further reduced the S. pombe gene number by large-scale gene deletion to identify a minimal gene set required for growth under laboratory conditions. The genome-reduced strain has four deletion regions: 168.4 kb in the left arm of chromosome I, 155.4 kb in the right arm of chromosome I, 211.7 kb in the left arm of chromosome II and 121.6 kb in the right arm of chromosome II. The deletions corresponded to a loss of 223 genes of the original ∼5100. The quadruple-deletion strain, with a total deletion size of 657.3 kb, showed a decreased ability to uptake glucose and some amino acids in comparison with the parental strain. The strain also showed increased gene expression of the mating pheromone M-factor precursor and the nicotinamide adenine dinucleotide phosphate -specific glutamate dehydrogenase. There was also a 2.7-fold increase in the concentration of cellular adenosine triphosphate, and levels of the heterologous proteins, enhanced green fluorescent protein and secreted human growth hormone were increased by 1.7- and 1.8-fold, respectively. The transcriptome data from this study have been submitted to the Gene Expression Omnibus (GEO: http://www.ncbi.nlm.nih.gov/geo/) under the accession number GSE38620 (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?token=vjkxjewuywgcovc&acc=GSE38620). PMID:23563150

  10. [Construction of the flavinogenic yeast Candida famata strains with high riboflavin kinase activity using gene engineering].

    PubMed

    Ishchuk, O P; Iatsyshyn, V Iu; Dmytruk, K V; Voronovs'kyĭ, A Ia; Fedorovych, D V; Sybirnyĭ, A A

    2006-01-01

    The recombinant strains of the flavinogenic yeast Candida famata, which contain the DNA fragment consisting of the FMN1 gene (encoding the riboflavin kinase, enzyme that converts riboflavin to flavinmononucleotide) driven by the strong promoters (the regulated RIB1 or constitutive TEF1 promoter) were isolated. Riboflavin kinase activity in the isolated transformants was tested. The 6-8-fold increase of the riboflavin kinase activity was shown in the recombinant strains containing the integrated Debaryomyces hansenii FMN1 gene under the strong constitutive TEF1 promoter. The recombinant strains can be used for the following construction of flavinmononucleotide overproducers. PMID:17290783

  11. Construction of a URA3 deletion strain from the allotetraploid bottom-fermenting yeast Saccharomyces pastorianus.

    PubMed

    Murakami, Nobutada; Miyoshi, Sae; Yokoyama, Ryo; Hoshida, Hisashi; Akada, Rinji; Ogata, Tomoo

    2012-05-01

    The bottom-fermenting lager yeast Saccharomyces pastorianus has been proposed to be allotetraploid, containing two S. cerevisiae (Sc)-type and two S. bayanus (Sb)-type chromosomes. This chromosomal constitution likely explains why recessive mutants of S. pastorianus have not previously been reported. Here we describe the construction of a ura3 deletion strain derived from the lager strain Weihenstephan34/70 by targeted transformation and subsequent loss of heterozygosity (LOH). Initially, deletion constructs of the Sc and Sb types of URA3 were constructed in laboratory yeast strains in which a TDH3p-hygro allele conferring hygromycin B resistance replaced ScURA3 and a KanMX cassette conferring G-418 resistance replaced SbURA3. The lager strain was then transformed with these constructs to yield a heterozygous URA3 disruptant (ScURA3⁺/Scura3Δ::TDH3p-hygro, SbURA3⁺/Sbura3Δ::KanMX), which was plated on 5-fluoroorotic acid (5-FOA) plates to generate the desired Ura⁻ homozygous disruptant (Scura3Δ::TDH3p-hygro/Scura3Δ::TDH3p-hygro Sbura3Δ::KanMX/Sbura3Δ::KanMX) through LOH. This ura3 deletion strain was then used to construct a bottom-fermenting yeast transformant overexpressing ATF1 that encodes an enzyme that produces acetate esters. The ATF1-overexpressing transformant produced significantly more acetate esters than the parent strain. The constructed ura3∆ lager strain will be a useful host for constructing strains of relevance to brewing. PMID:22576669

  12. Biocontrol ability and action mechanism of food-isolated yeast strains against Botrytis cinerea causing post-harvest bunch rot of table grape.

    PubMed

    Parafati, Lucia; Vitale, Alessandro; Restuccia, Cristina; Cirvilleri, Gabriella

    2015-05-01

    Strains belonging to the species Saccharomyces cerevisiae, Wickerhamomyces anomalus, Metschnikowia pulcherrima and Aureobasidium pullulans, isolated from different food sources, were tested in vitro as biocontrol agents (BCAs) against the post-harvest pathogenic mold Botrytis cinerea. All yeast strains demonstrated antifungal activity at different levels depending on species and medium. Killer strains of W. anomalus and S. cerevisiae showed the highest biocontrol in vitro activity, as demonstrated by largest inhibition halos. The competition for iron and the ability to form biofilm and to colonize fruit wounds were hypothesized as the main action mechanisms for M. pulcherrima. The production of hydrolytic enzymes and the ability to colonize the wounds were the most important mechanisms for biocontrol activity in A. pullulans and W. anomalus, which also showed high ability to form biofilm. The production of volatile organic compounds (VOCs) with in vitro and in vivo inhibitory effect on pathogen growth was observed for the species W. anomalus, S. cerevisiae and M. pulcherrima. Our study clearly indicates that multiple modes of action may explain as M. pulcherrima provide excellent control of postharvest botrytis bunch rot of grape. PMID:25583341

  13. Microbiological Characteristics of Wild Yeast Strain Pichia anomala Y197-13 for Brewing Makgeolli

    PubMed Central

    Kim, Hye Ryun; Kim, Jae-Ho; Bai, Dong-Hoon

    2013-01-01

    Makgeolli is a traditional cloudy-white Korean rice wine with an alcohol content of 6~7%. The present study investigated the morphological characteristics, carbon-utilizing ability, fatty acid composition, alcohol resistance, glucose tolerance, and flocculence of Saccharomyces cerevisiae Y98-5 and Pichia anomala Y197-13, non-S. cerevisiae isolated from Nuruk, which is used in brewing Makgeolli. Similar morphological characteristics were observed for both isolated wild yeast strains; and the carbon source assimilation of Y197-13 differed from that of other P. anomala strains. Strain Y197-13 was negative for D-trehalose, mannitol, arbutin, I-erythritol, and succinic acid. The major cellular fatty acids of strain Y197-13 included C18:2n6c (33.94%), C18:1n9c (26.97%) and C16:0 (20.57%). Strain Y197-13 was Crabtree-negative, with 60% cell viability at 12% (v/v) ethanol. The flocculation level of strain Y197-13 was 8.38%, resulting in its classification as a non-flocculent yeast. PMID:24198668

  14. Computational models for prediction of yeast strain potential for winemaking from phenotypic profiles.

    PubMed

    Mendes, Inês; Franco-Duarte, Ricardo; Umek, Lan; Fonseca, Elza; Drumonde-Neves, João; Dequin, Sylvie; Zupan, Blaz; Schuller, Dorit

    2013-01-01

    Saccharomyces cerevisiae strains from diverse natural habitats harbour a vast amount of phenotypic diversity, driven by interactions between yeast and the respective environment. In grape juice fermentations, strains are exposed to a wide array of biotic and abiotic stressors, which may lead to strain selection and generate naturally arising strain diversity. Certain phenotypes are of particular interest for the winemaking industry and could be identified by screening of large number of different strains. The objective of the present work was to use data mining approaches to identify those phenotypic tests that are most useful to predict a strain's potential for winemaking. We have constituted a S. cerevisiae collection comprising 172 strains of worldwide geographical origins or technological applications. Their phenotype was screened by considering 30 physiological traits that are important from an oenological point of view. Growth in the presence of potassium bisulphite, growth at 40 °C, and resistance to ethanol were mostly contributing to strain variability, as shown by the principal component analysis. In the hierarchical clustering of phenotypic profiles the strains isolated from the same wines and vineyards were scattered throughout all clusters, whereas commercial winemaking strains tended to co-cluster. Mann-Whitney test revealed significant associations between phenotypic results and strain's technological application or origin. Naïve Bayesian classifier identified 3 of the 30 phenotypic tests of growth in iprodion (0.05 mg/mL), cycloheximide (0.1 µg/mL) and potassium bisulphite (150 mg/mL) that provided most information for the assignment of a strain to the group of commercial strains. The probability of a strain to be assigned to this group was 27% using the entire phenotypic profile and increased to 95%, when only results from the three tests were considered. Results show the usefulness of computational approaches to simplify strain selection

  15. Industrial Saccharomyces cerevisiae Yeast Strain Engineered to Convert Glucose, Mannose, Arabinose, and Xylose (GMAX) to Ethanol Anaerobically

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Technology for engineering an industrial yeast strain for production of ethanol from glucose, mannose, arabinose, and xylose (GMAX-yeast) using both corn starch and cellulosic feedstocks with simultaneous production of valuable coproducts, including biodiesel, will be discussed. A stable industrial...

  16. Characterization of yakju brewed from glutinous rice and wild-type yeast strains isolated from nuruks.

    PubMed

    Kim, Hye Ryun; Kim, Jae-Ho; Bae, Dong-Hoon; Ahn, Byung-Hak

    2010-12-01

    Korean traditional rice wines yakju and takju are generally brewed with nuruk as the source of the saccharogenic enzymes by natural fermentation. To improve the quality of Korean rice wine, the microorganisms in the nuruk need to be studied. The objective of this research was to improve the quality of Korean wine with the wild-type yeast strains isolated from the fermentation starter, nuruk. Only strain YA-6 showed high activity in 20% ethanol. Precipitation of Y89-5-3 was similar to that of very flocculent yeast (〉80%) at 75.95%. Using 18S rRNA sequencing, all 10 strains were identified as Saccharomyces cerevisiae. Volatile compounds present in yakju were analyzed by gas chromatography-mass selective detector. The principal component analysis (PCA) of the volatile compounds grouped long-chain esters on the right side of the first principal component, PC1; these compounds were found in yakju that was made with strains YA-6, Y89-5-3, Y89-5- 2, Y90-9, and Y89-1-1. On the other side of PC1 were short-chain esters; these compounds were found in wines that were brewed with strains Y183-2, Y268-3, Y54-3, Y98-4, and Y88-4. Overall, the results indicated that using different wild-type yeast strains in the fermentation process significantly affects the chemical characteristics of the glutinous rice wine. PMID:21193827

  17. Melanin production by a yeast strain XJ5-1 of Aureobasidium melanogenum isolated from the Taklimakan desert and its role in the yeast survival in stress environments.

    PubMed

    Jiang, Hong; Liu, Nan-Nan; Liu, Guang-Lei; Chi, Zhe; Wang, Jian-Ming; Zhang, Ly-Ly; Chi, Zhen-Ming

    2016-07-01

    The yeast strain XJ5-1 isolated from the Taklimakan desert soil was identified to be a strain of Aureobasdium melanogenum and could produce a large amount of melanin when it was grown in the PDA medium, but its melanin biosynthesis and expression of the PKS gene responsible for the melanin biosynthesis was significantly repressed in the presence of (NH4)2SO4. However, A. melanogenum P5 strain isolated from a mangrove ecosystem grown in both the presence and the absence of (NH4)2SO4 did not produce any melanin. The cell size of A. melanogenum XJ5-1 strain was much higher than that of A. melanogenum P5 strain. The melanized cells of the yeast strain XJ5-1 had higher tolerance to UV radiation, oxidation (200.0 mM H2O2), heat treatment (40 °C), salt shock (200.0 g/L NaCl), desiccation and strong acid hydrolysis (6.0 M HCl) at high temperature (80 °C) than the non-melanized cells of the same yeast strain XJ5-1. At the same time, the melanized cells of the yeast strain XJ5-1 also had higher tolerance to UV radiation, oxidation (200.0 mM H2O2), desiccation and strong acid hydrolysis (6.0 M HCl) at high temperature (80 °C) than A. melanogenum P5 strain, but had similar resistance to heat treatment (40 °C) and salt shock (200.0 g/L NaCl) compared to those of A. melanogenum P5 strain. All the results revealed that many characteristics of A. melanogenum XJ5-1 isolated from the Taklimakan desert soil was different from those of A. melanogenum P5 strain isolated from the mangrove ecosystem. PMID:27290725

  18. Enhancing adhesion of yeast brewery strains to chamotte carriers through aminosilane surface modification.

    PubMed

    Berlowska, Joanna; Kregiel, Dorota; Ambroziak, Wojciech

    2013-07-01

    The adhesion of cells to solid supports is described as surface-dependent, being largely determined by the properties of the surface. In this study, ceramic surfaces modified using different organosilanes were tested for proadhesive properties using industrial brewery yeast strains in different physiological states. Eight brewing strains were tested: bottom-fermenting Saccharomyces pastorianus and top-fermenting Saccharomyces cerevisiae. To determine adhesion efficiency light microscopy, scanning electron microscopy and the fluorymetric method were used. Modification of chamotte carriers by 3-(3-anino-2-hydroxy-1-propoxy) propyldimethoxysilane and 3-(N, N-dimethyl-N-2-hydroxyethyl) ammonium propyldimethoxysilane groups increased their biomass load significantly. PMID:23420113

  19. Yeast strains for ethanol production from lignocellulosic hydrolysates during in situ detoxification.

    PubMed

    Tian, Shen; Zhou, Guixiong; Yan, Fei; Yu, Yong; Yang, Xiushan

    2009-01-01

    Yeast strains Y1, Y4 and Y7 demonstrated high conversion efficiencies for sugars and high abilities to tolerate or metabolize inhibitors in dilute-acid lignocellulosic hydrolysates. Strains Y1 and Y4 completely consumed the glucose within 24 h in dilute-acid lignocellulosic hydrolysate during in situ detoxification, and the maximum ethanol yields reached 0.49 g and 0.45 g ethanol/g glucose, equivalent to maximum theoretical values of 96% and 88.2%, respectively. Strain Y1 could metabolize xylose to xylitol with a yield of 0.64 g/g xylose, whereas Y4 was unable to utilize xylose as a substrate. Strain Y7 was able to consume sugars (glucose and xylose) within 72 h during hydrolysate in situ detoxification, producing a high ethanol yield (equivalent to 93.6% of the maximum theoretical value). Y1 and Y7 are the most efficient yeast strains yet reported for producing ethanol from non-detoxified dilute-acid lignocellulosic hydrolysates. These findings offer huge potential for improving the economics of bio-ethanol production from lignocellulosic hydrolysates. PMID:19393310

  20. Strain conformation controls the specificity of cross-species prion transmission in the yeast model.

    PubMed

    Grizel, Anastasia V; Rubel, Aleksandr A; Chernoff, Yury O

    2016-07-01

    Transmissible self-assembled fibrous cross-β polymer infectious proteins (prions) cause neurodegenerative diseases in mammals and control non-Mendelian heritable traits in yeast. Cross-species prion transmission is frequently impaired, due to sequence differences in prion-forming proteins. Recent studies of prion species barrier on the model of closely related yeast species show that colocalization of divergent proteins is not sufficient for the cross-species prion transmission, and that an identity of specific amino acid sequences and a type of prion conformational variant (strain) play a major role in the control of transmission specificity. In contrast, chemical compounds primarily influence transmission specificity via favoring certain strain conformations, while the species origin of the host cell has only a relatively minor input. Strain alterations may occur during cross-species prion conversion in some combinations. The model is discussed which suggests that different recipient proteins can acquire different spectra of prion strain conformations, which could be either compatible or incompatible with a particular donor strain. PMID:27565563

  1. The green monster process for the generation of yeast strains carrying multiple gene deletions.

    PubMed

    Suzuki, Yo; Stam, Jason; Novotny, Mark; Yachie, Nozomu; Lasken, Roger S; Roth, Frederick P

    2012-01-01

    Phenotypes for a gene deletion are often revealed only when the mutation is tested in a particular genetic background or environmental condition(1,2). There are examples where many genes need to be deleted to unmask hidden gene functions(3,4). Despite the potential for important discoveries, genetic interactions involving three or more genes are largely unexplored. Exhaustive searches of multi-mutant interactions would be impractical due to the sheer number of possible combinations of deletions. However, studies of selected sets of genes, such as sets of paralogs with a greater a priori chance of sharing a common function, would be informative. In the yeast Saccharomyces cerevisiae, gene knockout is accomplished by replacing a gene with a selectable marker via homologous recombination. Because the number of markers is limited, methods have been developed for removing and reusing the same marker(5,6,7,8,9,10). However, sequentially engineering multiple mutations using these methods is time-consuming because the time required scales linearly with the number of deletions to be generated. Here we describe the Green Monster method for routinely engineering multiple deletions in yeast(11). In this method, a green fluorescent protein (GFP) reporter integrated into deletions is used to quantitatively label strains according to the number of deletions contained in each strain (Figure 1). Repeated rounds of assortment of GFP-marked deletions via yeast mating and meiosis coupled with flow-cytometric enrichment of strains carrying more of these deletions lead to the accumulation of deletions in strains (Figure 2). Performing multiple processes in parallel, with each process incorporating one or more deletions per round, reduces the time required for strain construction. The first step is to prepare haploid single-mutants termed 'ProMonsters,' each of which carries a GFP reporter in a deleted locus and one of the 'toolkit' loci-either Green Monster GMToolkit-a or GMToolkit

  2. The Green Monster Process for the Generation of Yeast Strains Carrying Multiple Gene Deletions

    PubMed Central

    Suzuki, Yo; Stam, Jason; Novotny, Mark; Yachie, Nozomu; Lasken, Roger S.; Roth, Frederick P.

    2012-01-01

    Phenotypes for a gene deletion are often revealed only when the mutation is tested in a particular genetic background or environmental condition1,2. There are examples where many genes need to be deleted to unmask hidden gene functions3,4. Despite the potential for important discoveries, genetic interactions involving three or more genes are largely unexplored. Exhaustive searches of multi-mutant interactions would be impractical due to the sheer number of possible combinations of deletions. However, studies of selected sets of genes, such as sets of paralogs with a greater a priori chance of sharing a common function, would be informative. In the yeast Saccharomyces cerevisiae, gene knockout is accomplished by replacing a gene with a selectable marker via homologous recombination. Because the number of markers is limited, methods have been developed for removing and reusing the same marker5,6,7,8,9,10. However, sequentially engineering multiple mutations using these methods is time-consuming because the time required scales linearly with the number of deletions to be generated. Here we describe the Green Monster method for routinely engineering multiple deletions in yeast11. In this method, a green fluorescent protein (GFP) reporter integrated into deletions is used to quantitatively label strains according to the number of deletions contained in each strain (Figure 1). Repeated rounds of assortment of GFP-marked deletions via yeast mating and meiosis coupled with flow-cytometric enrichment of strains carrying more of these deletions lead to the accumulation of deletions in strains (Figure 2). Performing multiple processes in parallel, with each process incorporating one or more deletions per round, reduces the time required for strain construction. The first step is to prepare haploid single-mutants termed 'ProMonsters,' each of which carries a GFP reporter in a deleted locus and one of the 'toolkit' loci—either Green Monster GMToolkit-a or GMToolkit-α at the

  3. The oxidative stress response of a lager brewing yeast strain during industrial propagation and fermentation.

    PubMed

    Gibson, Brian R; Lawrence, Stephen J; Boulton, Chris A; Box, Wendy G; Graham, Neil S; Linforth, Robert S T; Smart, Katherine A

    2008-06-01

    Commercial brewing yeast strains are exposed to a number of potential stresses including oxidative stress. The aim of this investigation was to measure the physiological and transcriptional changes of yeast cells during full-scale industrial brewing processes with a view to determining the environmental factors influencing the cell's oxidative stress response. Cellular antioxidant levels and genome-wide transcriptional changes were monitored throughout an industrial propagation and fermentation. The greatest increase in cellular antioxidants and transcription of antioxidant-encoding genes occurred as the rapidly fermentable sugars glucose and fructose were depleted from the growth medium (wort) and the cell population entered the stationary phase. The data suggest that, contrary to expectation, the oxidative stress response is not influenced by changes in the dissolved oxygen concentration of wort but is initiated as part of a general stress response to growth-limiting conditions, even in the absence of oxygen. A mechanism is proposed to explain the changes in antioxidant response observed in yeast during anaerobic fermentation. The available data suggest that the yeast cell does not experience oxidative stress during industrial brewery handling. This information may be taken into consideration when setting parameters for industrial brewery fermentation. PMID:18373683

  4. Analysis and Dynamics of the Chromosomal Complements of Wild Sparkling-Wine Yeast Strains

    PubMed Central

    Nadal, Dolors; Carro, David; Fernández-Larrea, Juan; Piña, Benjamin

    1999-01-01

    We isolated Saccharomyces cerevisiae yeast strains that are able to carry out the second fermentation of sparkling wine from spontaneously fermenting musts in El Penedès (Spain) by specifically designed selection protocols. All of them (26 strains) showed one of two very similar mitochondrial DNA (mtDNA) restriction patterns, whereas their karyotypes differed. These strains showed high rates of karyotype instability, which were dependent on both the medium and the strain, during vegetative growth. In all cases, the mtDNA restriction pattern was conserved in strains kept under the same conditions. Analysis of different repetitive sequences in their genomes suggested that ribosomal DNA repeats play an important role in the changes in size observed in chromosome XII, whereas SUC genes or Ty elements did not show amplification or transposition processes that could be related to rearrangements of the chromosomes showing these sequences. Karyotype changes also occurred in monosporidic diploid derivatives. We propose that these changes originated mainly from ectopic recombination between repeated sequences interspersed in the genome. None of the rearranged karyotypes provided a selective advantage strong enough to allow the strains to displace the parental strains. The nature and frequency of these changes suggest that they may play an important role in the establishment and maintenance of the genetic diversity observed in S. cerevisiae wild populations. PMID:10103269

  5. Glucocorticoid cell reception in mice of different strains with natural killer cell activity depressed during immobilization stress

    SciTech Connect

    Lyashko, V.N.; Sukhikh, G.T.

    1987-08-01

    The authors study differences in stress-induced depression of natural killer cell activity in mice of different inbred lines, depending on parameters of glucocorticoid binding with glucorticoid receptors of spleen cells and on the hormonal status of the animals. In determining the parameters of glucocorticoid binding on intact splenocytes, aliquots of a suspension of washed splenocytes were incubated with tritium-labeled dexamethasone.

  6. Effects of dietary yeast strains on immunoglobulin in colostrum and milk of sows.

    PubMed

    Zanello, Galliano; Meurens, François; Serreau, Delphine; Chevaleyre, Claire; Melo, Sandrine; Berri, Mustapha; D'Inca, Romain; Auclair, Eric; Salmon, Henri

    2013-03-15

    The ban of antibiotic growth promoters in pig diet required the development of alternative strategies and reinforced the importance of maternal immunity to protect neonates from intestinal disorders. Milk from sows fed active dry yeasts during gestation and lactation exhibited higher immunoglobulin (Ig) and protein content in milk at day 21 of lactation. In this study, we investigated whether the administration of Saccharomyces cerevisiae strains of various origins (Sc01, Sc02, Sb03) to sows during late gestation and lactation could induce higher Ig content in colostrum and milk. Results show that yeast supplementation did not increase significantly sow body weight at days 112 of gestation and 18 of lactation as well as piglet body weight gain from birth to weaning. In contrast, the IgG level in colostrum was increased in comparison with the control group when sows were supplemented with Sc01 at both 0.05 and 0.5% (p<0.05) and Sb03 at 0.5% (p<0.01). During the lactation, the level of milk IgG remained significantly higher in comparison with the control group when sows were supplemented with Sc02 at 0.05% and 0.5% and with Sb03 at 0.5%. Furthermore, in comparison with the control sows, the level of milk IgA was significantly maintained in sows supplemented with the 3 yeast strains at 0.05%. The incidence of piglet diarrhoea was decreased in groups Sc01 at both 0.05% and 0.5% and Sc02 at 0.05%. Thus, these results show that the 3 yeast strains display immunostimulatory effects on maternal immunity, but only Sc01 supplementation at 0.05% allowed jointly the increase of IgG level in colostrum, the maintenance of IgA level in milk and the decrease of piglet diarrhoea incidence. This stimulation of maternal immunity could be associated with a better systemic (colostrum IgG) and local (milk IgA) protection of neonates and suggests that dietary yeasts may have stimulated the local gut immune system of sows. PMID:23092748

  7. [The Engineering of a Yarrowia lipolytica Yeast Strain Capable of Homologous Recombination of the Mitochondrial Genome].

    PubMed

    Isakova, E P; Epova, E Yu; Sekova, V Yu; Trubnikova, E V; Kudykina, Yu K; Zylkova, M V; Guseva, M A; Deryabina, Yu I

    2015-01-01

    None of the studied eukaryotic species has a natural system for homologous recombination of the mitochondrial genome. We propose an integrated genetic construct pQ-SRUS, which allows introduction of the recA gene from Bacillus subtilis into the nuclear genome of an extremophilic yeast, Yarrowia lipolytica. The targeting of recombinant RecA to the yeast mitochondria is provided by leader sequences (5'-UTR and 3'-UTR) derived from the SOD2 gene mRNA, which exhibits affinity to the outer mitochondrial membrane and thus provides cotranslational transport of RecA to the inner space of the mitochondria. The Y. lipolytica strain bearing the pQ-SRUS construct has the unique ability to integrate DNA constructs into the mitochondrial genome. This fact was confirmed using a tester construct, pQ-NIHN, intended for the introduction of the EYFP gene into the translation initiation region of the Y. lipolytica ND1 mitochondrial gene. The Y. lipolytica strain bearing pQ-SRUS makes it possible to engineer recombinant producers based on Y. lipolytica bearing transgenes in the mitochondrial genome. They are promising for the construction of a genetic system for in vivo replication and modification of the human mitochondrial genome. These strains may be used as a tool for the treatment of human mitochondrial diseases (including genetically inherited ones). PMID:26204776

  8. Antifungal susceptibility profiles of 1698 yeast reference strains revealing potential emerging human pathogens.

    PubMed

    Desnos-Ollivier, Marie; Robert, Vincent; Raoux-Barbot, Dorothée; Groenewald, Marizeth; Dromer, Françoise

    2012-01-01

    New molecular identification techniques and the increased number of patients with various immune defects or underlying conditions lead to the emergence and/or the description of novel species of human and animal fungal opportunistic pathogens. Antifungal susceptibility provides important information for ecological, epidemiological and therapeutic issues. The aim of this study was to assess the potential risk of the various species based on their antifungal drug resistance, keeping in mind the methodological limitations. Antifungal susceptibility profiles to the five classes of antifungal drugs (polyens, azoles, echinocandins, allylamines and antimetabolites) were determined for 1698 yeast reference strains belonging to 992 species (634 Ascomycetes and 358 Basidiomycetes). Interestingly, geometric mean minimum inhibitory concentrations (MICs) of all antifungal drugs tested were significantly higher for Basidiomycetes compared to Ascomycetes (p<0.001). Twenty four strains belonging to 23 species of which 19 were Basidiomycetes seem to be intrinsically "resistant" to all drugs. Comparison of the antifungal susceptibility profiles of the 4240 clinical isolates and the 315 reference strains belonging to 53 shared species showed similar results. Even in the absence of demonstrated in vitro/in vivo correlation, knowing the in vitro susceptibility to systemic antifungal agents and the putative intrinsic resistance of yeast species present in the environment is important because they could become opportunistic pathogens. PMID:22396754

  9. Glycerol production by Oenococcus oeni during sequential and simultaneous cultures with wine yeast strains.

    PubMed

    Ale, Cesar E; Farías, Marta E; Strasser de Saad, Ana M; Pasteris, Sergio E

    2014-07-01

    Growth and fermentation patterns of Saccharomyces cerevisiae, Kloeckera apiculata, and Oenococcus oeni strains cultured in grape juice medium were studied. In pure, sequential and simultaneous cultures, the strains reached the stationary growth phase between 2 and 3 days. Pure and mixed K. apiculata and S. cerevisiae cultures used mainly glucose, producing ethanol, organic acids, and 4.0 and 0.1 mM glycerol, respectively. In sequential cultures, O. oeni achieved about 1 log unit at 3 days using mainly fructose and L-malic acid. Highest sugars consumption was detected in K. apiculata supernatants, lactic acid being the major end-product. 8.0 mM glycerol was found in 6-day culture supernatants. In simultaneous cultures, total sugars and L-malic acid were used at 3 days and 98% of ethanol and glycerol were detected. This study represents the first report of the population dynamics and metabolic behavior of yeasts and O. oeni in sequential and simultaneous cultures and contributes to the selection of indigenous strains to design starter cultures for winemaking, also considering the inclusion of K. apiculata. The sequential inoculation of yeasts and O. oeni would enhance glycerol production, which confers desirable organoleptic characteristics to wines, while organic acids levels would not affect their sensory profile. PMID:24752716

  10. High Production of Squalene Using a Newly Isolated Yeast-like Strain Pseudozyma sp. SD301.

    PubMed

    Song, Xiaojin; Wang, Xiaolong; Tan, Yanzhen; Feng, Yingang; Li, Wenli; Cui, Qiu

    2015-09-30

    A yeast-like fungus, termed strain SD301, with the ability to produce a high concentration of squalene, was isolated from Shuidong Bay, China. The nucleotide sequence analysis of the internal transcribed spacer (ITS) region of SD301 indicated the strain belonged to Pseudozyma species. The highest biomass and squalene production of SD301 were obtained when glucose and yeast extracts were used as the carbon and nitrogen sources, respectively, with a C/N ratio of 3. The optimal pH and temperature were 6 and 25 °C, with 15 g L(-1) of supplemented sea salt. The maximum squalene productivity reached 0.039 g L(-1) h(-1) in batch fermentation, while the maximum squalene yield of 2.445 g L(-1) was obtained in fed-batch fermentation. According to our knowledge, this is the highest squalene yield produced thus far using fermentation technology, and the newly isolated strain Pseudozyma sp. SD301 is a promising candidate for commercial squalene production. PMID:26350291

  11. Draft Genome Sequence of the Deep-Sea Basidiomycetous Yeast Cryptococcus sp. Strain Mo29 Reveals Its Biotechnological Potential.

    PubMed

    Rédou, Vanessa; Kumar, Abhishek; Hainaut, Matthieu; Henrissat, Bernard; Record, Eric; Barbier, Georges; Burgaud, Gaëtan

    2016-01-01

    Cryptococcus sp. strain Mo29 was isolated from the Rainbow hydrothermal site on the Mid-Atlantic Ridge. Here, we present the draft genome sequence of this basidiomycetous yeast strain, which has highlighted its biotechnological potential as revealed by the presence of genes involved in the synthesis of secondary metabolites and biotechnologically important enzymes. PMID:27389259

  12. Draft Genome Sequence of the Deep-Sea Basidiomycetous Yeast Cryptococcus sp. Strain Mo29 Reveals Its Biotechnological Potential

    PubMed Central

    Rédou, Vanessa; Kumar, Abhishek; Hainaut, Matthieu; Henrissat, Bernard; Record, Eric; Barbier, Georges

    2016-01-01

    Cryptococcus sp. strain Mo29 was isolated from the Rainbow hydrothermal site on the Mid-Atlantic Ridge. Here, we present the draft genome sequence of this basidiomycetous yeast strain, which has highlighted its biotechnological potential as revealed by the presence of genes involved in the synthesis of secondary metabolites and biotechnologically important enzymes. PMID:27389259

  13. Biotransformation of ethanol to acetaldehyde by wild and mutant strains of methylotrophic yeast

    SciTech Connect

    Moroz, O.M.; Sibirnyi, A.A.; Ksheminskaya, G.P. |

    1995-05-01

    The conversion of ethanol to acetaldehyde by intact cells of wild and mutant strains of methylotrophic yeast Hansenula polymorpha was studied. It was established that mutations that lower the activity of aldehyde reductase and acetaldehyde dehydrogenase stimulate acetaldehyde accumulation. The highest accumulation of acetaldehyde was found in a mutant that possessed increased alcohol oxidase activity in growth on a medium with glucose. A decrease in formaldehyde dehydrogenase did not stimulate acetaldehyde accumulation. Bioconversion of ethanol to acetaldehyde was most effective at lowered temperatures due to marked suppression of catabolic alcohol oxidase inactivation, but not to the activity of this enzyme under indicated conditions. 27 refs., 4 figs., 3 tabs.

  14. Regioselective hydrolysis of acetates in the presence of different yeast strains.

    PubMed

    Krzyczkowska, J; Majewska, E; Białecka-Florjańczyk, E

    2014-01-01

    The model compound, hexane-1,2-diol diacetate, was hydrolyzed in the presence of supernatant obtained after cultivation of 4 yeast strains: Pichia jadinii, Rhodotorula glutinis and Yarrowia lipolytica KKP 379 and Saccharomyces cerevisiae 102 to evaluate the type of catalysis. The regioselectivity of extracellular enzymes as a function of hydrolysis towards primary and secondary acetic acid ester groups was monitored. The enzymes secreted by P. jadinii, R. glutinis and Y. lipolytica KKP 379 exhibited high regioselectivity towards primary position, while those from S. cerevisiae showed practically no discrimination between the ester groups. PMID:25272729

  15. Multiplexed, Proteome-Wide Protein Expression Profiling: Yeast Deubiquitylating Enzyme Knockout Strains

    PubMed Central

    Isasa, Marta; Rose, Christopher M.; Elsasser, Suzanne; Navarrete-Perea, José; Paulo, Joao A.; Finley, Daniel J.; Gygi, Steven P.

    2016-01-01

    Characterizing a protein’s function often requires a description of the cellular state in its absence. Multiplexing in mass spectrometry-based proteomics has now achieved the ability to globally measure protein expression levels in yeast from 10 cell states simultaneously. We applied this approach to quantify expression differences in wild type and nine deubiquitylating enzyme (DUB) knockout strains with the goal of creating “information networks” that might provide deeper, mechanistic insights into a protein’s biological role. In total, more than 3700 proteins were quantified with high reproducibility across three biological replicates (30 samples in all). DUB mutants demonstrated different proteomics profiles, consistent with distinct roles for each family member. These included differences in total ubiquitin levels and specific chain linkages. Moreover, specific expression changes suggested novel functions for several DUB family members. For instance, the ubp3Δ mutant showed large expression changes for members of the cytochrome C oxidase complex, consistent with a role for Ubp3 in mitochondrial regulation. Several DUBs also showed broad expression changes for phosphate transporters as well as other components of the inorganic phosphate signaling pathway, suggesting a role for these DUBs in regulating phosphate metabolism. These data highlight the potential of multiplexed proteome-wide analyses for biological investigation and provide a framework for further study of the DUB family. Our methods are readily applicable to the entire collection of yeast deletion mutants and may help facilitate systematic analysis of yeast and other organisms. PMID:26503604

  16. Metabolomics-based prediction models of yeast strains for screening of metabolites contributing to ethanol stress tolerance

    NASA Astrophysics Data System (ADS)

    Hashim, Z.; Fukusaki, E.

    2016-06-01

    The increased demand for clean, sustainable and renewable energy resources has driven the development of various microbial systems to produce biofuels. One of such systems is the ethanol-producing yeast. Although yeast produces ethanol naturally using its native pathways, production yield is low and requires improvement for commercial biofuel production. Moreover, ethanol is toxic to yeast and thus ethanol tolerance should be improved to further enhance ethanol production. In this study, we employed metabolomics-based strategy using 30 single-gene deleted yeast strains to construct multivariate models for ethanol tolerance and screen metabolites that relate to ethanol sensitivity/tolerance. The information obtained from this study can be used as an input for strain improvement via metabolic engineering.

  17. Thermotolerant Yeast Strains Adapted by Laboratory Evolution Show Trade-Off at Ancestral Temperatures and Preadaptation to Other Stresses

    PubMed Central

    Nielsen, Jens

    2015-01-01

    ABSTRACT A major challenge for the production of ethanol from biomass-derived feedstocks is to develop yeasts that can sustain growth under the variety of inhibitory conditions present in the production process, e.g., high osmolality, high ethanol titers, and/or elevated temperatures (≥40°C). Using adaptive laboratory evolution, we previously isolated seven Saccharomyces cerevisiae strains with improved growth at 40°C. Here, we show that genetic adaptations to high temperature caused a growth trade-off at ancestral temperatures, reduced cellular functions, and improved tolerance of other stresses. Thermotolerant yeast strains showed horizontal displacement of their thermal reaction norms to higher temperatures. Hence, their optimal and maximum growth temperatures increased by about 3°C, whereas they showed a growth trade-off at temperatures below 34°C. Computational analysis of the physical properties of proteins showed that the lethal temperature for yeast is around 49°C, as a large fraction of the yeast proteins denature above this temperature. Our analysis also indicated that the number of functions involved in controlling the growth rate decreased in the thermotolerant strains compared with the number in the ancestral strain. The latter is an advantageous attribute for acquiring thermotolerance and correlates with the reduction of yeast functions associated with loss of respiration capacity. This trait caused glycerol overproduction that was associated with the growth trade-off at ancestral temperatures. In combination with altered sterol composition of cellular membranes, glycerol overproduction was also associated with yeast osmotolerance and improved tolerance of high concentrations of glucose and ethanol. Our study shows that thermal adaptation of yeast is suitable for improving yeast resistance to inhibitory conditions found in industrial ethanol production processes. PMID:26199325

  18. Coordinated Evolution of Transcriptional and Post-Transcriptional Regulation for Mitochondrial Functions in Yeast Strains

    PubMed Central

    Guo, Xiaoxian; Li, Hongye; Gu, Zhenglong

    2016-01-01

    Evolution of gene regulation has been proposed to play an important role in environmental adaptation. Exploring mechanisms underlying coordinated evolutionary changes at various levels of gene regulation could shed new light on how organism adapt in nature. In this study, we focused on regulatory differences between a laboratory Saccharomyces cerevisiae strain BY4742 and a pathogenic S. cerevisiae strain, YJM789. The two strains diverge in many features, including growth rate, morphology, high temperature tolerance, and pathogenicity. Our RNA-Seq and ribosomal footprint profiling data showed that gene expression differences are pervasive, and genes functioning in mitochondria are mostly divergent between the two strains at both transcriptional and translational levels. Combining functional genomics data from other yeast strains, we further demonstrated that significant divergence of expression for genes functioning in the electron transport chain (ETC) was likely caused by differential expression of a transcriptional factor, HAP4, and that post-transcriptional regulation mediated by an RNA-binding protein, PUF3, likely led to expression divergence for genes involved in mitochondrial translation. We also explored mito-nuclear interactions via mitochondrial DNA replacement between strains. Although the two mitochondrial genomes harbor substantial sequence divergence, neither growth nor gene expression were affected by mitochondrial DNA replacement in both fermentative and respiratory growth media, indicating compatible mitochondrial and nuclear genomes between these two strains in the tested conditions. Collectively, we used mitochondrial functions as an example to demonstrate for the first time that evolution at both transcriptional and post-transcriptional levels could lead to coordinated regulatory changes underlying strain specific functional variations. PMID:27077367

  19. Coordinated Evolution of Transcriptional and Post-Transcriptional Regulation for Mitochondrial Functions in Yeast Strains.

    PubMed

    Sun, Xuepeng; Wang, Zhe; Guo, Xiaoxian; Li, Hongye; Gu, Zhenglong

    2016-01-01

    Evolution of gene regulation has been proposed to play an important role in environmental adaptation. Exploring mechanisms underlying coordinated evolutionary changes at various levels of gene regulation could shed new light on how organism adapt in nature. In this study, we focused on regulatory differences between a laboratory Saccharomyces cerevisiae strain BY4742 and a pathogenic S. cerevisiae strain, YJM789. The two strains diverge in many features, including growth rate, morphology, high temperature tolerance, and pathogenicity. Our RNA-Seq and ribosomal footprint profiling data showed that gene expression differences are pervasive, and genes functioning in mitochondria are mostly divergent between the two strains at both transcriptional and translational levels. Combining functional genomics data from other yeast strains, we further demonstrated that significant divergence of expression for genes functioning in the electron transport chain (ETC) was likely caused by differential expression of a transcriptional factor, HAP4, and that post-transcriptional regulation mediated by an RNA-binding protein, PUF3, likely led to expression divergence for genes involved in mitochondrial translation. We also explored mito-nuclear interactions via mitochondrial DNA replacement between strains. Although the two mitochondrial genomes harbor substantial sequence divergence, neither growth nor gene expression were affected by mitochondrial DNA replacement in both fermentative and respiratory growth media, indicating compatible mitochondrial and nuclear genomes between these two strains in the tested conditions. Collectively, we used mitochondrial functions as an example to demonstrate for the first time that evolution at both transcriptional and post-transcriptional levels could lead to coordinated regulatory changes underlying strain specific functional variations. PMID:27077367

  20. Fluorescence and fluorescence-lifetime imaging microscopy (FLIM) to characterize yeast strains by autofluorescence

    NASA Astrophysics Data System (ADS)

    Bhatta, H.; Goldys, E. M.; Ma, J.

    2006-02-01

    We characterised populations of wild type baking and brewing yeast cells using intrinsic fluorescence and fluorescence lifetime microscopy, in order to obtain quantitative identifiers of different strains. The cell autofluorescence was excited at 405 nm and observed within 440-540 nm range where strong cell to cell variability was observed. The images were analyzed using customised public domain software, which provided information on cell size, intensity and texture-related features. In light of significant diversity of the data, statistical methods were utilized to assess the validity of the proposed quantitative identifiers for strain differentiation. The Kolmogorov-Smirnov test was applied to confirm that empirical distribution functions for size, intensity and entropy for different strains were statistically different. These characteristics were followed with culture age of 24, 48 and 72 h, (the latter corresponding to a stationary growth phase) and size, and to some extent entropy, were found to be independent of age. The fluorescence intensity presented a distinctive evolution with age, different for each of the examined strains. The lifetime analysis revealed a short decay time component of 1.4 ns and a second, longer one with the average value of 3.5 ns and a broad distribution. High variability of lifetime values within cells was observed however a lifetime texture feature in the studied strains was statistically different.

  1. Mutagenesis by Cytostatic Alkylating Agents in Yeast Strains of Differing Repair Capacities

    PubMed Central

    Ruhland, Axel; Brendel, Martin

    1979-01-01

    Reversion of two nuclear ochre nonsense alleles and cell inactivation induced by mono-, bi-, and tri-functional alkylating agents and by UV has been investigated in stationary-phase haploid cells of yeast strains with differing capacities for DNA repair. The ability to survive alkylation damage is correlated with UV repair capacity, a UV-resistant and UV-mutable strain (RAD REV) being least and a UV-sensitive and UV-nonmutable strain (rad1 rev3) most sensitive. Mutagenicity of alkylating agents is highest in the former and is abolished in the latter strain. Deficiency in excision repair (rad1 rad2) or in the RAD18 function does not lead to enhanced mutability. Mutagenesis by the various agents is characterized by a common pattern of induction of locus-specific revertants and suppressor mutants. Induction kinetics are mostly linear, but UV-induced reversion in the RAD REV strain follows higher-than-linear (probably "quadratic") kinetics. The alkylating agent cyclophosphamide, usually considered inactive without metabolic conversion, reduces colony-forming ability and induces revertants in a manner similar but not identical to the other chemicals tested. These findings are taken to support the concept of mutagenesis by misrepair after alkylation, which albeit sharing common features with the mechanism of UV-induced reversion, can be distinguished therefrom. PMID:387518

  2. Construction, Verification and Experimental Use of Two Epitope-Tagged Collections of Budding Yeast Strains

    PubMed Central

    Howson, Russell; Huh, Won-Ki; Ghaemmaghami, Sina; Falvo, James V.; Bower, Kiowa; Belle, Archana; Dephoure, Noah; Wykoff, Dennis D.; Weissman, Jonathan S.

    2005-01-01

    A major challenge in the post-genomic era is the development of experimental approaches to monitor the properties of proteins on a proteome-wide level. It would be particularly useful to systematically assay protein subcellular localization, post-translational modifications and protein–protein interactions, both at steady state and in response to environmental stimuli. Development of new reagents and methods will enhance our ability to do so efficiently and systematically. Here we describe the construction of two collections of budding yeast strains that facilitate proteome-wide measurements of protein properties. These collections consist of strains with an epitope tag integrated at the C-terminus of essentially every open reading frame (ORF), one with the tandem affinity purification (TAP) tag, and one with the green fluorescent protein (GFP) tag. We show that in both of these collections we have accurately tagged a high proportion of all ORFs (approximately 75% of the proteome) by confirming expression of the fusion proteins. Furthermore, we demonstrate the use of the TAP collection in performing high-throughput immunoprecipitation experiments. Building on these collections and the methods described in this paper, we hope that the yeast community will expand both the quantity and type of proteome level data available. PMID:18629296

  3. GMAX Yeast Background Strain Made from Industrial Tolerant Saccharomyces cerevisiae Engineered to Convert Sucrose, Starch and Cellulosic Sugars Universally to Ethanol Anaerobically with Concurrent Coproduct Expression

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tailored GMAX yeast background strain technology for universal ethanol production industrially. Production of the stable baseline glucose, mannose, arabinose, xylose-utilizing (GMAX) yeast will be evaluated by taking the genes identified in high-throughput screening for a plasmid-based yeast to uti...

  4. GMAX Yeast Background Strain Made from Industrial Tolerant Saccharomyces Cerevisiae Engineered to Convert Pretreated Lignocellulosic Starch and Cellulosic Sugars Universally to Ethanol Anaerobically

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tailored GMAX yeast background strain technology for universal ethanol production industrially: Production of the stable baseline glucose, mannose, arabinose, xylose-utilizing (GMAX) yeast will be evaluated by taking the genes identified in high-throughput screening for a plasmid-based yeast to util...

  5. Physical properties and antifungal activity of bioactive films containing Wickerhamomyces anomalus killer yeast and their application for preservation of oranges and control of postharvest green mold caused by Penicillium digitatum.

    PubMed

    Aloui, Hajer; Licciardello, Fabio; Khwaldia, Khaoula; Hamdi, Moktar; Restuccia, Cristina

    2015-05-01

    This study assessed the ability of two bio-based films, obtained from sodium alginate (NaAlg) and locust bean gum (LBG), to protect the viability of Wickerhamomyces anomalus cells and control the growth of Penicillium digitatum. The effect of microbial cell incorporation on physical properties of the developed films was evaluated in terms of barrier, mechanical and optical properties. Furthermore, the application of these two matrices as bioactive coatings was investigated in order to evaluate their efficacy in preserving the postharvest quality of 'Valencia' oranges and inhibiting the growth of P. digitatum on artificially inoculated fruits. Results showed that NaAlg and LBG films were able to maintain more than 85% of the initial W. anomalus yeast population and that the developed films incorporating the killer yeast completely inhibited the growth of P. digitatum in synthetic medium. Likewise, NaAlg and LBG coatings enriched with W. anomalus yeast were effective at reducing weight loss and maintaining firmness of 'Valencia' oranges during storage, and reduced green mold in inoculated fruits by more than 73% after 13 days. PMID:25666444

  6. Genomic Libraries and a Host Strain Designed for Highly Efficient Two-Hybrid Selection in Yeast

    PubMed Central

    James, P.; Halladay, J.; Craig, E. A.

    1996-01-01

    The two-hybrid system is a powerful technique for detecting protein-protein interactions that utilizes the well-developed molecular genetics of the yeast Saccharomyces cerevisiae. However, the full potential of this technique has not been realized due to limitations imposed by the components available for use in the system. These limitations include unwieldy plasmid vectors, incomplete or poorly designed two-hybrid libraries, and host strains that result in the selection of large numbers of false positives. We have used a novel multienzyme approach to generate a set of highly representative genomic libraries from S. cerevisiae. In addition, a unique host strain was created that contains three easily assayed reporter genes, each under the control of a different inducible promoter. This host strain is extremely sensitive to weak interactions and eliminates nearly all false positives using simple plate assays. Improved vectors were also constructed that simplify the construction of the gene fusions necessary for the two-hybrid system. Our analysis indicates that the libraries and host strain provide significant improvements in both the number of interacting clones identified and the efficiency of two-hybrid selections. PMID:8978031

  7. Isolation and properties of genetically defined strains of the methylotrophic yeast Hansenula polymorpha CBS4732.

    PubMed

    Lahtchev, Kantcho L; Semenova, Vika D; Tolstorukov, Ilia I; van der Klei, Ida; Veenhuis, Marten

    2002-02-01

    Genetically defined strains of the yeast Hansenula polymorpha were constructed from a clone of H. polymorpha CBS4732 with very low mating and sporulation abilities. Mating, spore viability, and the percentage of four-spore-containing asci were increased to a level at which tetrad analysis was possible. Auxotrophic mutations in 30 genes were isolated and used to construct strains with multiple markers for mapping studies, transformation with plasmid DNA, and mutant screening. Various other types of mutants were isolated and characterized, among them mutants that displayed an altered morphology, methanol-utilization deficient mutants and strains impaired in the biosynthesis of alcohol oxidase and catalase. Also, the mutability of H. polymorpha CBS4732 vs H. polymorpha NCYC495 was compared. The data revealed clear differences in frequencies of appearance and mutational spectra of some mutants isolated. Many of the mutants isolated had good mating abilities, and diploids resulting from their crossing displayed high sporulation frequencies and high spore viability. Most of the markers used revealed normal Mendelian segregation during meiosis. The frequency of tetratype spore formation was lower than in Saccharomyces cerevisiae suggesting a lower frequency of recombination during the second meiotic division. The properties of genetically defined strains of H. polymorpha CBS4732 as well as their advantages for genetics and molecular studies are discussed. PMID:11807564

  8. Automated Yeast Mating Protocol Using Open Reading Frames from Saccharomyces cerevisiae Genome to Improve Yeast Strains for Cellulosic Ethanol Production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Engineering the industrial ethanologen Saccharomyces cerevisiae to utilize pentose sugars from lignocellulosic biomass is critical for commercializing cellulosic fuel ethanol production. Approaches to engineer pentose-fermenting yeasts have required expression of additional genes. We implemented a...

  9. Potential Role of Yeast Strains Isolated from Grapes in the Production of Taurasi DOCG.

    PubMed

    Aponte, Maria; Blaiotta, Giuseppe

    2016-01-01

    Twelve samples of Aglianico grapes, collected in different locations of the Taurasi DOCG (Appellation of Controlled and Guaranteed Origin) production area were naturally fermented in sterile containers at room temperature. A total of 70 yeast cultures were isolated from countable WL agar plates: 52 in the middle of the fermentation and 18 at the end. On the basis of ITS-RFLP analysis and ITS sequencing, all cultures collected at the end of fermentations were identified as Saccharomyces (S.) cerevisiae; while, the 52 isolates, collected after 1 week, could be referred to the following species: Metschnikowia (M.) pulcherrima; Starmerella (Star.) bacillaris; Pichia (P.) kudriavzevii; Lachancea (L.) thermotolerans; Hanseniaspora (H.) uvarum; Pseudozyma (Pseud.) aphidis; S. cerevisiae. By means of Interdelta analysis, 18 different biotypes of S. cerevisiae were retrieved. All strains were characterized for ethanol production, SO2 resistance, H2S development, β-glucosidasic, esterasic and antagonistic activities. Fermentation abilities of selected strains were evaluated in micro-fermentations on Aglianico must. Within non-Saccharomyces species, some cultures showed features of technological interest. Antagonistic activity was expressed by some strains of M. pulcherrima, L. thermotolerans, P. kudriavzevii, and S. cerevisiae. Strains of M. pulcherrima showed the highest β-glucosidase activity and proved to be able to produce high concentrations of succinic acid. L. thermotolerans produced both succinic and lactic acids. The lowest amount of acetic acid was produced by M. pulcherrima and L. thermotolerans; while the highest content was recorded for H. uvarum. The strain of Star. bacillaris produced the highest amount of glycerol and was able to metabolize all fructose and malic acid. Strains of M. pulcherrima and H. uvarum showed a low fermentation power (about 4%), while, L. thermotolerans, Star. Bacillaris, and P. kudriavzevii of about 10%. Significant differences were

  10. Potential Role of Yeast Strains Isolated from Grapes in the Production of Taurasi DOCG

    PubMed Central

    Aponte, Maria; Blaiotta, Giuseppe

    2016-01-01

    Twelve samples of Aglianico grapes, collected in different locations of the Taurasi DOCG (Appellation of Controlled and Guaranteed Origin) production area were naturally fermented in sterile containers at room temperature. A total of 70 yeast cultures were isolated from countable WL agar plates: 52 in the middle of the fermentation and 18 at the end. On the basis of ITS-RFLP analysis and ITS sequencing, all cultures collected at the end of fermentations were identified as Saccharomyces (S.) cerevisiae; while, the 52 isolates, collected after 1 week, could be referred to the following species: Metschnikowia (M.) pulcherrima; Starmerella (Star.) bacillaris; Pichia (P.) kudriavzevii; Lachancea (L.) thermotolerans; Hanseniaspora (H.) uvarum; Pseudozyma (Pseud.) aphidis; S. cerevisiae. By means of Interdelta analysis, 18 different biotypes of S. cerevisiae were retrieved. All strains were characterized for ethanol production, SO2 resistance, H2S development, β-glucosidasic, esterasic and antagonistic activities. Fermentation abilities of selected strains were evaluated in micro-fermentations on Aglianico must. Within non-Saccharomyces species, some cultures showed features of technological interest. Antagonistic activity was expressed by some strains of M. pulcherrima, L. thermotolerans, P. kudriavzevii, and S. cerevisiae. Strains of M. pulcherrima showed the highest β-glucosidase activity and proved to be able to produce high concentrations of succinic acid. L. thermotolerans produced both succinic and lactic acids. The lowest amount of acetic acid was produced by M. pulcherrima and L. thermotolerans; while the highest content was recorded for H. uvarum. The strain of Star. bacillaris produced the highest amount of glycerol and was able to metabolize all fructose and malic acid. Strains of M. pulcherrima and H. uvarum showed a low fermentation power (about 4%), while, L. thermotolerans, Star. Bacillaris, and P. kudriavzevii of about 10%. Significant differences were

  11. Raman Spectroscopy and Chemometrics for Identification and Strain Discrimination of the Wine Spoilage Yeasts Saccharomyces cerevisiae, Zygosaccharomyces bailii, and Brettanomyces bruxellensis

    PubMed Central

    Thornton, Mark A.; Thornton, Roy J.

    2013-01-01

    The yeasts Zygosaccharomyces bailii, Dekkera bruxellensis (anamorph, Brettanomyces bruxellensis), and Saccharomyces cerevisiae are the major spoilage agents of finished wine. A novel method using Raman spectroscopy in combination with a chemometric classification tool has been developed for the identification of these yeast species and for strain discrimination of these yeasts. Raman spectra were collected for six strains of each of the yeasts Z. bailii, B. bruxellensis, and S. cerevisiae. The yeasts were classified with high sensitivity at the species level: 93.8% for Z. bailii, 92.3% for B. bruxellensis, and 98.6% for S. cerevisiae. Furthermore, we have demonstrated that it is possible to discriminate between strains of these species. These yeasts were classified at the strain level with an overall accuracy of 81.8%. PMID:23913433

  12. Genome Sequences of Industrially Relevant Saccharomyces cerevisiae Strain M3707, Isolated from a Sample of Distillers Yeast and Four Haploid Derivatives

    SciTech Connect

    Brown, Steven D.; Klingeman, Dawn M.; Johnson, Courtney M.; Clum, Alicia; Aerts, Andrea; Salamov, Asaf; Sharma, Aditi; Zane, Matthew; Barry, Kerrie; Grigoriev, Igor V.; Davison, Brian H.; Lynd, Lee R.; Gilna, Paul; Hau, Heidi; Hogsett, David A.; Froehlich, Allan C.

    2013-04-19

    Saccharomyces cerevisiae strain M3707 was isolated from a sample of commercial distillers yeast, and its genome sequence together with the genome sequences for the four derived haploid strains M3836, M3837, M3838, and M3839 has been determined. Yeasts have potential for consolidated bioprocessing (CBP) for biofuel production, and access to these genome sequences will facilitate their development.

  13. Physicochemical characterization of pomegranate wines fermented with three different Saccharomyces cerevisiae yeast strains.

    PubMed

    Berenguer, María; Vegara, Salud; Barrajón, Enrique; Saura, Domingo; Valero, Manuel; Martí, Nuria

    2016-01-01

    Three commercial Saccharomyces cerevisiae yeast strains: Viniferm Revelación, Viniferm SV and Viniferm PDM were evaluated for the production of pomegranate wine from a juice coupage of the two well-known varieties Mollar and Wonderfull. Further malolactic fermentation was carried out spontaneously. The same fermentation patterns were observed for pH, titratable acidity, density, sugar consumption, and ethanol and glycerol production. Glucose was exhausted while fructose residues remained at the end of alcoholic fermentation. A high ethanol concentration (10.91 ± 0.27% v/v) in combination with 1.49 g/L glycerol was achieved. Citric acid concentration increased rapidly a 31.7%, malic acid disappeared as result of malolactic fermentation and the lactic acid levels reached values between 0.40 and 0.96 g/L. The analysis of CIEa parameter and total anthocyanin content highlights a lower degradation of monomeric anthocyanins during winemaking with Viniferm PDM yeast. The resulting wine retains a 34.5% of total anthocyanin content of pomegranate juice blend. PMID:26213048

  14. Lipid accumulation by oleaginous and non-oleaginous yeast strains in nitrogen and phosphate limitation.

    PubMed

    Kolouchová, Irena; Maťátková, Olga; Sigler, Karel; Masák, Jan; Řezanka, Tomáš

    2016-09-01

    We investigated the possibility of utilizing both oleaginous yeast species accumulating large amounts of lipids (Yarrowia lipolytica, Rhodotorula glutinis, Trichosporon cutaneum, Candida sp.) and traditional biotechnological non-oleaginous ones characterized by high biomass yield (Kluyveromyces polysporus, Torulaspora delbrueckii, Saccharomyces cerevisiae) as potential producers of biofuel-utilizable and nutritionally valuable lipids. The main objective was to increase lipid accumulation by increasing C/P ratio together with higher C/N ratio, while maintaining high biomass yield. The C/N ratio of 30 was found to lead to higher biomass content and the total lipid content increased significantly with higher C/P ratio. With higher ratios of both C/N and C/P, the content of monounsaturated fatty acids (FAs) in cell lipids increased while polyunsaturated FAs decreased. Oleaginous yeast species had a lower proportion of unsaturated FAs (approx. 80 %) than non-oleaginous strains (approx. 90 %). At a C/N ratio of 30 and C/P ratio 1043, T. cutaneum produced a high amount of ω-6 unsaturated linoleic acid, the precursor of some prostaglandins, leukotrienes, and thromboxanes, while Candida sp. and K. polysporus accumulated a high content of palmitoleic acid. PMID:26931336

  15. Draft Genome Sequence of the Yeast Pseudozyma antarctica Type Strain JCM10317, a Producer of the Glycolipid Biosurfactants, Mannosylerythritol Lipids

    PubMed Central

    Saika, Azusa; Koike, Hideaki; Hori, Tomoyuki; Fukuoka, Tokuma; Sato, Shun; Habe, Hiroshi; Kitamoto, Dai

    2014-01-01

    The basidiomycetous yeast Pseudozyma antarctica is known as a producer of industrial enzymes and the extracellular glycolipids, mannosylerythritol lipids. Here, we report the draft genome sequence of the type strain JCM10317. The draft genome assembly has a size of 18.1 Mb and a G+C content of 60.9%, and it consists of 197 scaffolds. PMID:25291760

  16. Draft Genome Sequence of the Yeast Pseudozyma antarctica Type Strain JCM10317, a Producer of the Glycolipid Biosurfactants, Mannosylerythritol Lipids.

    PubMed

    Saika, Azusa; Koike, Hideaki; Hori, Tomoyuki; Fukuoka, Tokuma; Sato, Shun; Habe, Hiroshi; Kitamoto, Dai; Morita, Tomotake

    2014-01-01

    The basidiomycetous yeast Pseudozyma antarctica is known as a producer of industrial enzymes and the extracellular glycolipids, mannosylerythritol lipids. Here, we report the draft genome sequence of the type strain JCM10317. The draft genome assembly has a size of 18.1 Mb and a G+C content of 60.9%, and it consists of 197 scaffolds. PMID:25291760

  17. Creating libraries for commercial yeast strains through miniaturization of cloning and transformations using the BioRAPTR FRD Microfluidic workstation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ability to miniaturize molecular reactions can lead to significant cost savings when creating libraries of thousands of clones. For this application Beckman Coulter partnered with the USDA to provide a low-volume automated solution for library cloning for use in the development of yeast strains...

  18. Pilot-scale evaluation the enological traits of a novel, aromatic wine yeast strain obtained by adaptive evolution.

    PubMed

    Cadière, Axelle; Aguera, Evelyne; Caillé, Soline; Ortiz-Julien, Anne; Dequin, Sylvie

    2012-12-01

    In the competitive context of the wine market, there is a growing interest for novel wine yeast strains that have an overall good fermentation capacity and that contribute favorably to the organoleptic quality of wine. Using an adaptive evolution strategy based on growth on gluconate as sole carbon source, we recently obtained wine yeasts with improved characteristics in laboratory-scale fermentations. The characteristics included enhanced fermentation rate, decreased formation of acetate and greater production of fermentative aroma. We report an evaluation of the potential value of the evolved strain ECA5™ for winemaking, by comparing its fermentation performance and metabolite production to those of the parental strain in pilot-scale fermentation trials, with various grape cultivars and winemaking conditions. We show that the evolved strain has outstanding attributes relative to the parental wine yeast strain, and in particular the production of less volatile acidity and greater production of desirable volatile esters, important for the fruity/flowery character of wines. This study highlights the potential of evolutionary engineering for the generation of strains with a broad range of novel properties, appropriate for rapid application in the wine industry. PMID:22986198

  19. Comparing the transcriptomes of wine yeast strains: toward understanding the interaction between environment and transcriptome during fermentation.

    PubMed

    Rossouw, Debra; Bauer, Florian F

    2009-10-01

    System-wide "omics" approaches have been widely applied to study a limited number of laboratory strains of Saccharomyces cerevisiae. More recently, industrial S. cerevisiae strains have become the target of such analyses, mainly to improve our understanding of biotechnologically relevant phenotypes that cannot be adequately studied in laboratory strains. Most of these studies have investigated single strains in a single medium. This experimental layout cannot differentiate between generally relevant molecular responses and strain- or media-specific features. Here we analyzed the transcriptomes of two phenotypically diverging wine yeast strains in two different fermentation media at three stages of wine fermentation. The data show that the intersection of transcriptome datasets from fermentations using either synthetic MS300 (simulated wine must) or real grape must (Colombard) can help to delineate relevant from "noisy" changes in gene expression in response to experimental factors such as fermentation stage and strain identity. The differences in the expression profiles of strains in the different environments also provide relevant insights into the transcriptional responses toward specific compositional features of the media. The data also suggest that MS300 is a representative environment for conducting research on wine fermentation and industrially relevant properties of wine yeast strains. PMID:19711068

  20. Characterization and Functional Analysis of the MAL and MPH Loci for Maltose Utilization in Some Ale and Lager Yeast Strains

    PubMed Central

    Vidgren, Virve; Ruohonen, Laura; Londesborough, John

    2005-01-01

    Maltose and maltotriose are the major sugars in brewer's wort. Brewer's yeasts contain multiple genes for maltose transporters. It is not known which of these express functional transporters. We correlated maltose transport kinetics with the genotypes of some ale and lager yeasts. Maltose transport by two ale strains was strongly inhibited by other α-glucosides, suggesting the use of broad substrate specificity transporters, such as Agt1p. Maltose transport by three lager strains was weakly inhibited by other α-glucosides, suggesting the use of narrow substrate specificity transporters. Hybridization studies showed that all five strains contained complete MAL1, MAL2, MAL3, and MAL4 loci, except for one ale strain, which lacked a MAL2 locus. All five strains also contained both AGT1 (coding a broad specificity α-glucoside transporter) and MAL11 alleles. MPH genes (maltose permease homologues) were present in the lager but not in the ale strains. During growth on maltose, the lager strains expressed AGT1 at low levels and MALx1 genes at high levels, whereas the ale strains expressed AGT1 at high levels and MALx1 genes at low levels. MPHx expression was negligible in all strains. The AGT1 sequences from the ale strains encoded full-length (616 amino acid) polypeptides, but those from both sequenced lager strains encoded truncated (394 amino acid) polypeptides that are unlikely to be functional transporters. Thus, despite the apparently similar genotypes of these ale and lager strains revealed by hybridization, maltose is predominantly carried by AGT1-encoded transporters in the ale strains and by MALx1-encoded transporters in the lager strains. PMID:16332759

  1. Identification of oleaginous yeast strains able to accumulate high intracellular lipids when cultivated in alkaline pretreated corn stover

    PubMed Central

    Sitepu, Irnayuli R.; Jin, Mingjie; Fernandez, J. Enrique; da Costa Sousa, Leonardo; Balan, Venkatesh; Boundy-Mills, Kyria L.

    2015-01-01

    Microbial oil is a potential alternative to food/plant-derived biodiesel fuel. Our previous screening studies identified a wide range of oleaginous yeast species, using a defined laboratory medium known to stimulate lipid accumulation. In this study, the ability of these yeasts to grow and accumulate lipids was further investigated in synthetic hydrolysate (SynH) and authentic ammonia fiber expansion (AFEX™)-pretreated corn stover hydrolysate (ACSH). Most yeast strains tested were able to accumulate lipids in SynH, but only a few were able to grow and accumulate lipids in ACSH medium. Cryptococcus humicola UCDFST 10-1004 was able to accumulate as high as 15.5 g/L lipids, out of a total of 36 g/L cellular biomass when grown in ACSH, with a cellular lipid content of 40% of cell dry weight. This lipid production is among the highest reported values for oleaginous yeasts grown in authentic hydrolysate. Pre-culturing in SynH media with xylose as sole carbon source enabled yeasts to assimilate both glucose and xylose more efficiently in the subsequent hydrolysate medium. This study demonstrates that ACSH is a suitable medium for certain oleaginous yeasts to convert lignocellullosic sugars to triacylglycerols for production of biodiesel and other valuable oleochemicals. PMID:25052467

  2. Construction of Novel Saccharomyces cerevisiae Strains for Bioethanol Active Dry Yeast (ADY) Production

    PubMed Central

    Gao, Kehui; Liu, Zewei; Zhang, Xing; Li, Ou; Sun, Jianguo; Zhang, Xiaoyang; Du, Fengguang; Sun, Peiyong; Qu, Aimin; Wu, Xuechang

    2013-01-01

    The application of active dry yeast (ADY) in bioethanol production simplifies operation processes and reduces the risk of bacterial contamination. In the present study, we constructed a novel ADY strain with improved stress tolerance and ethanol fermentation performances under stressful conditions. The industrial Saccharomyces cerevisiae strain ZTW1 showed excellent properties and thus subjected to a modified whole-genome shuffling (WGS) process to improve its ethanol titer, proliferation capability, and multiple stress tolerance for ADY production. The best-performing mutant, Z3-86, was obtained after three rounds of WGS, producing 4.4% more ethanol and retaining 2.15-fold higher viability than ZTW1 after drying. Proteomics and physiological analyses indicated that the altered expression patterns of genes involved in protein metabolism, plasma membrane composition, trehalose metabolism, and oxidative responses contribute to the trait improvement of Z3-86. This work not only successfully developed a novel S. cerevisiae mutant for application in commercial bioethanol production, but also enriched the current understanding of how WGS improves the complex traits of microbes. PMID:24376860

  3. Evaluation of baker's yeast strains exhibiting significant growth on Japanese beet molasses and compound analysis of the molasses types.

    PubMed

    Nakata, Hiroaki; Tamura, Masahiko; Shintani, Takahiro; Gomi, Katsuya

    2014-06-01

    Cane molasses, most of which is imported, is used as a raw material for production of baker's yeast (Saccharomyces cerevisiae) in Japan. On the other hand, beet molasses is scarcely used for this purpose, but it can be of great advantage to cane molasses because it is domestically produced in relatively high amounts as a by-product of beet sugar processing. However, the yield of baker's yeast is sometimes low with Japanese beet molasses compared to imported cane molasses. For the production of baker's yeast with Japanese beet molasses, we evaluated S. cerevisiae strains, including industrial and laboratory strains, to group them according to the growth profile on beet and cane molasses. To discuss the factors affecting growth, we further analyzed the major compounds in both types of molasses. Beet molasses seems to contain compounds that promote the growth of beet molasses-favoring strains rather than inhibit the growth of cane molasses-favoring strains. It was assumed that α-amino acid was one of the growth promotion factors for beet molasses-favoring strains. PMID:24333188

  4. Maltose and maltotriose utilisation by group I strains of the hybrid lager yeast Saccharomyces pastorianus.

    PubMed

    Magalhães, Frederico; Vidgren, Virve; Ruohonen, Laura; Gibson, Brian

    2016-08-01

    Brewer's wort is a challenging environment for yeast as it contains predominantly α-glucoside sugars. There exist two subgroups of the lager yeast Saccharomyces pastorianus which differ in sugar utilisation. We performed wort fermentations and compared representative strains from both groups with respect to their ability to transport and ferment maltose and maltotriose. Additionally, we mapped the transporters MALx1, AGT1, MPHx and MTT1 by Southern blotting. Contrary to previous observations, group I comprises a diverse set of strains, with varying ability to transport and ferment maltotriose. Of the eight group I strains, three efficiently utilised maltotriose, a property enabled by the presence of transmembrane transporters SeAGT1 and MTT1 A58, a variant of the group I type strain (CBS1513) performed particularly well, taking up maltotriose at a higher rate than maltose and retaining significant transport activity at temperatures as low as 0°C. Analysis of transporter distribution in this strain revealed an increased copy number of the MTT1 gene, which encodes the only permease known with higher affinity for maltotriose than maltose and low temperature dependence for transport. We propose that much of the variation in lager yeast fermentation behaviour is determined by the presence or absence of specific transmembrane transporters. PMID:27364826

  5. Comparative physiology and fermentation performance of Saaz and Frohberg lager yeast strains and the parental species Saccharomyces eubayanus.

    PubMed

    Gibson, Brian R; Storgårds, Erna; Krogerus, Kristoffer; Vidgren, Virve

    2013-07-01

    Two distinct genetic groups (Saaz and Frohberg) exist within the hybrid Saccharomyces pastorianus (S. cerevisiae × S. eubayanus) taxon. However, physiological/technological differences that exist between the two groups are not known. Fermentative capability of the parental S. eubayanus has likewise never been studied. Here, 58 lager strains were screened to determine which hybrid group they belonged to, and selected strains were characterized to determine salient characteristics. In 15 °P all-malt wort fermentations at 22 °C, Frohberg strains showed greater growth and superior fermentation (80% apparent attenuation, 6.5% alcohol by volume in 3-4 days) compared to all other strains and maintained highest viability values (>93%). Fermentation with S. eubayanus was poor at the same temperature (33% apparent attenuation, 2.7% alcohol by volume at 6 days and viability reduced to 75%). Saaz strains and S. eubayanus were the least sensitive to cold (10 °C), though this did not translate to greater fermentation performance. Fermentation with S. eubayanus was poor at 10 °C but equal to or greater than that of the Saaz strains. Performance of Saaz yeast/S. eubayanus was limited by an inability to use wort maltotriose. [(14)C]-Maltotriose transport assays also showed negligible activity in these strains (≤0.5 µmol min(-1) g(-1) dry yeast). Beers from Saaz fermentations were characterized by two- to sixfold lower production of the flavour compounds methyl butanol, ethyl acetate and 3-methylbutyl acetate compared to Frohberg strains. Higher alcohol and ester production by S. eubayanus was similar to that of Frohberg strains. PMID:23695993

  6. Enhanced cofermentation of glucose and xylose by recombinant Saccharomyces yeast strains in batch and continuous operating modes

    SciTech Connect

    Toon, S.T.; Riley, C.J.; Ho, N.W.Y.; Chen, ZhengDao

    1997-12-31

    Agricultural residues, such as grain by-products, are rich in the hydrolyzable carbohydrate polymers hemicellulose and cellulose; hence, they represent a readily available source of the fermentable sugars xylose and glucose. The biomass-to-ethanol technology is now a step closer to commercialization because a stable recombinant yeast strain has been developed that can efficiently ferment glucose and xylose simultaneously (coferment) to ethanol. This strain, LNH-ST, is a derivative of Saccharomyces yeast strain 1400 that carries the xylose-catabolism encoding genes of Pichia stipitis in its chromosome. Continuous pure sugar cofermentation studies with this organism resulted in promising steady-state ethanol yields (70.4% of theoretical based on available sugars) at a residence time of 48 h. 17 refs., 4 figs., 3 tabs.

  7. Genome-wide polysomal analysis of a yeast strain with mutated ribosomal protein S9

    PubMed Central

    Pnueli, Lilach; Arava, Yoav

    2007-01-01

    Background The yeast ribosomal protein S9 (S9) is located at the entrance tunnel of the mRNA into the ribosome. It is known to play a role in accurate decoding and its bacterial homolog (S4) has recently been shown to be involved in opening RNA duplexes. Here we examined the effects of changing the C terminus of S9, which is rich in acidic amino acids and extends out of the ribosome surface. Results We performed a genome-wide analysis to reveal effects at the transcription and translation levels of all yeast genes. While negligible relative changes were observed in steady-state mRNA levels, a significant number of mRNAs appeared to have altered ribosomal density. Notably, 40% of the genes having reliable signals changed their ribosomal association by more than one ribosome. Yet, no general correlations with physical or functional features of the mRNA were observed. Ribosome Density Mapping (RDM) along four of the mRNAs with increased association revealed an increase in ribosomal density towards the end of the coding region for at least two of them. Read-through analysis did not reveal any increase in read-through of a premature stop codon by the mutant strain. Conclusion The ribosomal protein rpS9 appears to be involved in the translation of many mRNAs, since altering its C terminus led to a significant change in ribosomal association of many mRNAs. We did not find strong correlations between these changes and several physical features of the mRNA, yet future studies with advanced tools may allow such correlations to be determined. Importantly, our results indicate an accumulation of ribosomes towards the end of the coding regions of some mRNAs. This suggests an involvement of S9 in ribosomal dissociation during translation termination. PMID:17711575

  8. An impaired ubiquitin ligase complex favors initial growth of auxotrophic yeast strains in synthetic grape must.

    PubMed

    Mangado, Ana; Tronchoni, Jordi; Morales, Pilar; Novo, Maite; Quirós, Manuel; Gonzalez, Ramon

    2015-02-01

    We used experimental evolution in order to identify genes involved in the adaptation of Saccharomyces cerevisiae to the early stages of alcoholic fermentation. Evolution experiments were run for about 200 generations, in continuous culture conditions emulating the initial stages of wine fermentation. We performed whole-genome sequencing of four adapted strains from three independent evolution experiments. Mutations identified in these strains pointed to the Rsp5p-Bul1/2p ubiquitin ligase complex as the preferred evolutionary target under these experimental conditions. Rsp5p is a multifunctional enzyme able to ubiquitinate target proteins participating in different cellular processes, while Bul1p is an Rsp5p substrate adaptor specifically involved in the ubiquitin-dependent internalization of Gap1p and other plasma membrane permeases. While a loss-of-function mutation in BUL1 seems to be enough to confer a selective advantage under these assay conditions, this did not seem to be the case for RSP5 mutated strains, which required additional mutations, probably compensating for the detrimental effect of altered Rsp5p activity on essential cellular functions. The power of this experimental approach is illustrated by the identification of four independent mutants, each with a limited number of SNPs, affected within the same pathway. However, in order to obtain information relevant for a specific biotechnological process, caution must be taken in the choice of the background yeast genotype (as shown in this case for auxotrophies). In addition, the use of very stable continuous fermentation conditions might lead to the selection of a rather limited number of adaptive responses that would mask other possible targets for genetic improvement. PMID:25620600

  9. DNA damage induced by the anticodon nuclease from a Pichia acaciae killer strain is linked to ribonucleotide reductase depletion.

    PubMed

    Wemhoff, Sabrina; Klassen, Roland; Meinhardt, Friedhelm

    2016-02-01

    Virus like element (VLE) encoded killer toxins of Pichia acaciae and Kluyveromyces lactis kill target cells through anticodon nuclease (ACNase) activity directed against tRNA(Gln) and tRNA(Glu) respectively. Not only does tRNA cleavage disable translation, it also affects DNA integrity as well. Consistent with DNA damage, which is involved in toxicity, target cells' mutation frequencies are elevated upon ACNase exposure, suggesting a link between translational integrity and genome surveillance. Here, we analysed whether ACNase action impedes the periodically and highly expressed S-phase specific ribonucleotide reductase (RNR) and proved that RNR expression is severely affected by PaT. Because RNR catalyses the rate-limiting step in dNTP synthesis, mutants affected in dNTP synthesis were scrutinized with respect to ACNase action. Mutations elevating cellular dNTPs antagonized the action of both the above ACNases, whereas mutations lowering dNTPs aggravated toxicity. Consistently, prevention of tRNA cleavage in elp3 or trm9 mutants, which both affect the wobble uridine modification of the target tRNA, suppressed the toxin hypersensitivity of a dNTP synthesis mutant. Moreover, dNTP synthesis defects exacerbated the PaT ACNase sensitivity of cells defective in homologous recombination, proving that dNTP depletion is responsible for subsequent DNA damage. PMID:26247322

  10. Occurrence of 20S RNA and 23S RNA replicons in industrial yeast strains and their variation under nutritional stress conditions.

    PubMed

    López, Victoria; Gil, Rosario; Vicente Carbonell, José; Navarro, Alfonso

    2002-04-01

    We have characterized industrial yeast strains used in the brewing, baking, and winemaking industries for the presence or absence of cytoplasmic single-stranded 20S and 23S RNAs. Furthermore, the variation of intracellular concentrations of these replicons in brewing and laboratory strains under nutritional stress conditions was determined. Our results show a correlation between the relative abundance of these replicons and exposure of yeast to nutritionally stressful conditions, indicating that these RNAs could be employed as molecular probes to evaluate the exposure of 20S(+) and/or 23S(+) yeast strains to stress situations during industrial manipulation. During this study, several 20S(-)23S(+) Saccharomyces cerevisiae strains were isolated and identified. This is the first time that a yeast strain containing only 23S RNA has been reported, demonstrating that 20S RNA is not required for 23S RNA replication. PMID:11921103

  11. Biodegradation of lindane using a novel yeast strain, Rhodotorula sp. VITJzN03 isolated from agricultural soil.

    PubMed

    Abdul Salam, Jaseetha; Lakshmi, V; Das, Devlina; Das, Nilanjana

    2013-03-01

    Lindane is a notorious organochlorine pesticide due to its high toxicity, persistence in the environment and its tendency to bioaccumulate. A yeast strain isolated from sorghum cultivation field was able to use lindane as carbon and energy source under aerobic conditions. With molecular techniques, it was identified and named as Rhodotorula strain VITJzN03. The effects of nutritional and environmental factors on yeast growth and the biodegradation of lindane was investigated. The maximum production of yeast biomass along with 100 % lindane mineralization was noted at an initial lindane concentration of 600 mg l(-1) within a period of 10 days. Lindane concentration above 600 mg l(-1) inhibited the growth of yeast in liquid medium. A positive relationship was noted between the release of chloride ions and the increase of yeast biomass as well as degradation of lindane. The calculated degradation rate and half life of lindane were found to be 0.416 day(-1) and 1.66 days, respectively. The analysis of the metabolites using GC-MS identified the formation of seven intermediates including γ-pentachlorocyclohexane(γ-PCCH), 1,3,4,6-tetrachloro-1,4-cyclohexadiene(1,4-TCCHdiene), 1,2,4-trichlorobenzene (1,2,4 TCB), 1,4-dichlorobenzene (1,4 DCB), chloro-cis-1,2-dihydroxycyclohexadiene (CDCHdiene), 3-chlorocatechol (3-CC) and maleylacetate (MA) derivatives indicating that lindane degradation follows successive dechlorination and oxido-reduction. Based on the results of the present study, the possible pathway for lindane degradation by Rhodotorula sp. VITJzN03 has been proposed. To the best of our knowledge, this is the first report on lindane degradation by yeast which can serve as a potential agent for in situ bioremediation of medium to high level lindane-contaminated sites. PMID:23108665

  12. Identification of regulatory elements in the AGT1 promoter of ale and lager strains of brewer's yeast.

    PubMed

    Vidgren, Virve; Kankainen, Matti; Londesborough, John; Ruohonen, Laura

    2011-08-01

    Agt1 is an interesting α-glucoside transporter for the brewing industry, as it efficiently transports maltotriose, a sugar often remaining partly unused during beer fermentation. It has been shown that on maltose the expression level of AGT1 is much higher in ale strains than in lager strains, and that glucose represses the expression, particularly in the ale strains. In the present study the regulatory elements of the AGT1 promoter of one ale and two lager strains were identified by computational methods. Promoter regions up to 1.9 kbp upstream of the AGT1 gene were sequenced from the three brewer's yeast strains and the laboratory yeast strain CEN.PK-1D. The promoter sequence of the laboratory strain was identical to the AGT1 promoter of strain S288c of the Saccharomyces Genome Database, whereas the promoter sequences of the industrial strains diverged markedly from the S288c strain. The AGT1 promoter regions of the ale and lager strains were for the most part identical to each other, except for one 22 bp deletion and two 94 and 95 bp insertions in the ale strain. Computational analyses of promoter elements revealed that the promoter sequences contained several Mig1- and MAL-activator binding sites, as was expected. However, some of the Mig1 and MAL-activator binding sites were located on the two insertions of the ale strain, and thus offered a plausible explanation for the different expression pattern of the AGT1 gene in the ale strains. Accordingly, functional analysis of A60 ale and A15 lager strain AGT1 promoters fused to GFP (encoding the green fluorescent protein) showed a significant difference in the ability of these two promoters to drive GFP expression. Under the control of the AGT1 promoter of the ale strain the emergence of GFP was strongly induced by maltose, whereas only a low level of GFP was detected with the construct carrying the AGT1 promoter of the lager strain. Thus, the extra MAL-activator binding element, present in the AGT1 promoter of

  13. Apple Aminoacid Profile and Yeast Strains in the Formation of Fusel Alcohols and Esters in Cider Production.

    PubMed

    Eleutério Dos Santos, Caroline Mongruel; Pietrowski, Giovana de Arruda Moura; Braga, Cíntia Maia; Rossi, Márcio José; Ninow, Jorge; Machado Dos Santos, Tâmisa Pires; Wosiacki, Gilvan; Jorge, Regina Maria Matos; Nogueira, Alessandro

    2015-06-01

    The amino acid profile in dessert apple must and its effect on the synthesis of fusel alcohols and esters in cider were established by instrumental analysis. The amino acid profile was performed in nine apple musts. Two apple musts with high (>150 mg/L) and low (<75 mg/L) nitrogen content, and four enological yeast strains, were used in cider fermentation. The aspartic acid, asparagine and glutamic acid amino acids were the majority in all the apple juices, representing 57.10% to 81.95%. These three amino acids provided a high consumption (>90%) during fermentation in all the ciders. Principal component analysis (PCA) explained 81.42% of data variability and the separation of three groups for the analyzed samples was verified. The ciders manufactured with low nitrogen content showed sluggish fermentation and around 50% less content of volatile compounds (independent of the yeast strain used), which were mainly 3-methyl-1-butanol (isoamyl alcohol) and esters. However, in the presence of amino acids (asparagine, aspartic acid, glutamic acid and alanine) there was a greater differentiation between the yeasts in the production of fusel alcohols and ethyl esters. High contents of these aminoacids in dessert apple musts are essential for the production of fusel alcohols and most of esters by aromatic yeasts during cider fermentation. PMID:25920613

  14. Stuck at work? Quantitative proteomics of environmental wine yeast strains reveals the natural mechanism of overcoming stuck fermentation.

    PubMed

    Szopinska, Aleksandra; Christ, Eva; Planchon, Sebastien; König, Helmut; Evers, Daniele; Renaut, Jenny

    2016-02-01

    During fermentation oenological yeast cells are subjected to a number of different stress conditions and must respond rapidly to the continuously changing environment of this harsh ecological niche. In this study we gained more insights into the cell adaptation mechanisms by linking proteome monitoring with knowledge on physiological behaviour of different strains during fermentation under model winemaking conditions. We used 2D-DIGE technology to monitor the proteome evolution of two newly discovered environmental yeast strains Saccharomyces bayanus and triple hybrid Saccharomyces cerevisiae × Saccharomyces kudriavzevii × S. bayanus and compared them to data obtained for the commercially available S. cerevisiae strain. All strains examined showed (i) different fermentative behaviour, (ii) stress resistance as well as (iii) susceptibility to stuck fermentation which was reflected in significant differences in protein expression levels. During our research we identified differentially expressed proteins in 155 gel spots which correspond to 70 different protein functions. Differences of expression between strains were observed mainly among proteins involved in stress response, proteins degradation pathways, cell redox homeostasis and amino acids biosynthesis. Interestingly, the newly discovered triple hybrid S. cerevisiae × S. kudriavzevii × S. bayanus strain which has the ability to naturally restart stuck fermentation showed a very strong induction of expression of two proteolytic enzymes: Pep4 and Prc1 that appear as numerous isoforms on the gel image and which may be the key to its unique properties. This study is an important step towards the better understanding of wine fermentations at a molecular level. PMID:26763469

  15. Construction of a Genetically Modified Wine Yeast Strain Expressing the Aspergillus aculeatus rhaA Gene, Encoding an α-l-Rhamnosidase of Enological Interest

    PubMed Central

    Manzanares, Paloma; Orejas, Margarita; Gil, José Vicente; de Graaff, Leo H.; Visser, Jaap; Ramón, Daniel

    2003-01-01

    The Aspergillus aculeatus rhaA gene encoding an α-l-rhamnosidase has been expressed in both laboratory and industrial wine yeast strains. Wines produced in microvinifications, conducted using a combination of the genetically modified industrial strain expressing rhaA and another strain expressing a β-glucosidase, show increased content mainly of the aromatic compound linalool. PMID:14660415

  16. Characterization of a novel tyrosine permease of lager brewing yeast shared by Saccharomyces cerevisiae strain RM11-1a.

    PubMed

    Omura, Fumihiko; Hatanaka, Haruyo; Nakao, Yoshihiro

    2007-12-01

    In Saccharomyces cerevisiae yeast, the uptake of aromatic amino acids is mediated by the relatively specific permeases Tat1p, Tat2p, Bap2p, and Bap3p, as well as by two other permeases with broader specificities: Gap1p and Agp1p. Here, a novel permease gene TAT3 (Tyrosine Amino acid Transporter) identified in the S. cerevisiae-type subset genome of the lager brewing yeast strain Weihenstephan Nr.34 (34/70) is reported. The TAT3 sequence was also found in the genome of S. cerevisiae strain RM11-1a, but not in S. cerevisiae strain S288C. Tat3p showed a significant similarity to Penicillium chrysogenum ArlP permease, which has transport activity for aromatic amino acids and leucine. When overexpressed in ssy1Delta gap1Delta mutant cells, Tat3p exhibited a tyrosine transport activity with an apparent K(m) of 160 microM. TAT3 transcription in lager brewing yeast was subjected to nitrogen catabolite repression in a manner similar to that of GAP1. Furthermore, the subcellular localization of Tat3p-green fluorescent protein (GFP) fusion protein was dependent on the quality of the nitrogen source, indicating a post-translational control of Tat3p function. PMID:17825063

  17. Construction of a yeast strain devoid of mitochondrial introns and its use to screen nuclear genes involved in mitochondrial splicing.

    PubMed Central

    Séraphin, B; Boulet, A; Simon, M; Faye, G

    1987-01-01

    We have constructed a respiring yeast strain devoid of mitochondrial introns to screen nuclear pet- mutants for those that play a direct role in mitochondrial intron excision. Intron-less mitochondria are introduced by cytoduction into pet- strains that have been made rho0; cytoductants therefrom recover respiratory competency if the original pet- mutation is required only for mitochondrial splicing. By this means, we have identified 11 complementation groups of such genes. Their total number may be estimated as about 18. Images PMID:3309947

  18. Identification of furfural as a key toxin in lignocellulosic hydrolysates and evolution of a tolerant yeast strain.

    PubMed

    Heer, Dominik; Sauer, Uwe

    2008-11-01

    The production of fuel ethanol from low-cost lignocellulosic biomass currently suffers from several limitations. One of them is the presence of inhibitors in lignocellulosic hydrolysates that are released during pre-treatment. These compounds inhibit growth and hamper the production of ethanol, thereby affecting process economics. To delineate the effects of such complex mixtures, we conducted a chemical analysis of four different real-world lignocellulosic hydrolysates and determined their toxicological effect on yeast. By correlating the potential inhibitor abundance to the growth-inhibiting properties of the corresponding hydrolysates, we identified furfural as an important contributor to hydrolysate toxicity for yeast. Subsequently, we conducted a targeted evolution experiment to improve growth behaviour of the half industrial Saccharomyces cerevisiae strain TMB3400 in the hydrolysates. After about 300 generations, representative clones from these evolved populations exhibited significantly reduced lag phases in medium containing the single inhibitor furfural, but also in hydrolysate-supplemented medium. Furthermore, these strains were able to grow at concentrations of hydrolysates that effectively killed the parental strain and exhibited significantly improved bioconversion characteristics under industrially relevant conditions. The improved resistance of our evolved strains was based on their capacity to remain viable in a toxic environment during the prolonged, furfural induced lag phase. PMID:21261870

  19. Cell cycle Start is coupled to entry into the yeast metabolic cycle across diverse strains and growth rates.

    PubMed

    Burnetti, Anthony J; Aydin, Mert; Buchler, Nicolas E

    2016-01-01

    Cells have evolved oscillators with different frequencies to coordinate periodic processes. Here we studied the interaction of two oscillators, the cell division cycle (CDC) and the yeast metabolic cycle (YMC), in budding yeast. Previous work suggested that the CDC and YMC interact to separate high oxygen consumption (HOC) from DNA replication to prevent genetic damage. To test this hypothesis, we grew diverse strains in chemostat and measured DNA replication and oxygen consumption with high temporal resolution at different growth rates. Our data showed that HOC is not strictly separated from DNA replication; rather, cell cycle Start is coupled with the initiation of HOC and catabolism of storage carbohydrates. The logic of this YMC-CDC coupling may be to ensure that DNA replication and cell division occur only when sufficient cellular energy reserves have accumulated. Our results also uncovered a quantitative relationship between CDC period and YMC period across different strains. More generally, our approach shows how studies in genetically diverse strains efficiently identify robust phenotypes and steer the experimentalist away from strain-specific idiosyncrasies. PMID:26538026

  20. Cell cycle Start is coupled to entry into the yeast metabolic cycle across diverse strains and growth rates

    PubMed Central

    Burnetti, Anthony J.; Aydin, Mert; Buchler, Nicolas E.

    2016-01-01

    Cells have evolved oscillators with different frequencies to coordinate periodic processes. Here we studied the interaction of two oscillators, the cell division cycle (CDC) and the yeast metabolic cycle (YMC), in budding yeast. Previous work suggested that the CDC and YMC interact to separate high oxygen consumption (HOC) from DNA replication to prevent genetic damage. To test this hypothesis, we grew diverse strains in chemostat and measured DNA replication and oxygen consumption with high temporal resolution at different growth rates. Our data showed that HOC is not strictly separated from DNA replication; rather, cell cycle Start is coupled with the initiation of HOC and catabolism of storage carbohydrates. The logic of this YMC–CDC coupling may be to ensure that DNA replication and cell division occur only when sufficient cellular energy reserves have accumulated. Our results also uncovered a quantitative relationship between CDC period and YMC period across different strains. More generally, our approach shows how studies in genetically diverse strains efficiently identify robust phenotypes and steer the experimentalist away from strain-specific idiosyncrasies. PMID:26538026

  1. Production of different types of mannosylerythritol lipids as biosurfactants by the newly isolated yeast strains belonging to the genus Pseudozyma.

    PubMed

    Konishi, Masaaki; Morita, Tomotake; Fukuoka, Tokuma; Imura, Tomohiro; Kakugawa, Koji; Kitamoto, Dai

    2007-06-01

    Mannosylerythritol lipids (MEL), which are abundantly secreted by yeasts, are one of the most promising biosurfactants known. To obtain various types of MEL and to attain a broad range of applications for them, screening of novel producers was undertaken. Thirteen strains of yeasts were successfully isolated as potential MEL producers; they showed high production yields of MEL of around 20 g l(-1) from 40 g l(-1) of soybean oil. Based on the taxonomical study, all the strains were classified to be the genus Pseudozyma. It is interesting to note that they were categorized into three groups according to their production patterns of MEL. The first group, which included 11 strains taxonomically closely related to high-level MEL producers such as Pseudozyma antarctica and Pseudozyma aphidis, mainly produced 4-O-[(4',6'-di-O-acetyl-2',3'-di-O-alkanoyl)-beta-D-mannopyranosyl]-meso-erythritol (MEL-A) together with 4-O-[(6'-mono-O-acetyl-2',3'-di-O-alkanoyl)-beta-D-mannopyranosyl]-meso-erythritol (MEL-B) and 4-O-[(4'-mono-O-acetyl-2',3'-di-O-alkanoyl)-beta-D-mannopyranosyl]-meso-erythritol (MEL-C) as the minor components. The second group of one strain, which was related to Pseudozyma tsukubaensis, predominantly produced MEL-B. The third group of one strain, which was closely related to Pseudozyma hubeiensis, mainly produced MEL-C; this is the first observation of the efficient production of MEL-C from soybean oil. Moreover, the major fatty acids of the obtained MEL-C were C(6), C(12), and C(16) acids, and were considerably different from those of the other MEL hitherto reported. The biosynthetic manner for MEL is thus likely to significantly vary among the Pseudozyma strains; the newly isolated strains would enable us to attain a large-scale production of MEL and to obtain various types of MEL with different hydrophobic structures. PMID:17505770

  2. Selection of 80 newly isolated autochthonous yeast strains from the Tikveš region of Macedonia and their impact on the quality of red wines produced from Vranec and Cabernet Sauvignon grape varieties.

    PubMed

    Ilieva, Fidanka; Kostadinović Veličkovska, Sanja; Dimovska, Violeta; Mirhosseini, Hamed; Spasov, Hristo

    2017-02-01

    The main objectives of this study were to (i) isolate newly autochthonous yeast strains from the Tikveš region of Macedonia and (ii) test their impact on the quality of red wines from Vranec and Cabernet Sauvignon grape varieties. The newly isolated yeast strains were obtained by spontaneous fermentation of grape must from Vranec and Cabernet Sauvignon varieties collected from ten different micro-regions in Macedonia. The grapevines from both varieties grown in "Barovo" micro-region were the richest sources of yeast strains. In addition, the molecular identification and typing of strains were also carried out. The monomeric anthocyanins, polyphenolic content and other oenochemical characteristics of the wines were also compared with the wines from commercial yeast strain "SiHa". The Vranec wine from yeast strain F-8 and Cabernet Sauvignon wine from yeast strain F-20 had significantly (p<0.05) higher concentrations of monomeric anthocyanins and total phenolic compounds than other wines. PMID:27596425

  3. Utilization of xylan by yeasts and its conversion to ethanol by Pichia stipitis strains. [Cryptococcus; Pichia stipitis; Candida shehatae

    SciTech Connect

    Lee, H.; Biely, P.; Latta, R.K.; Barbosa, M.F.S.; Schneider, H.

    1986-08-01

    Yeasts able to grow on D-xylose were screened for the ability to hydrolyze xylan. Xylanase activity was found to be rare; a total of only 19 of more than 250 strains yielded a positive test result. The activity was localized largely in the genus Cryptococcus and in Pichia stipitis and its anamorph Candida shehatae. The ability to hydrolyze xylan was generally uncoupled from that to hydrolyze cellulose; only three of the xylan-positive strains also yielded a positive test for cellulolytic activity. Of the 19 xylanolytic strains. 2. P. stipitis CBS 5773 and CBS 5775, converted xylan into ethanol, with about 60% of a theoretical yield computed on the basis of the amount of D-xylose present originally that could be released by acid hydrolysis.

  4. Glycerol Overproduction by Engineered Saccharomyces cerevisiae Wine Yeast Strains Leads to Substantial Changes in By-Product Formation and to a Stimulation of Fermentation Rate in Stationary Phase

    PubMed Central

    Remize, F.; Roustan, J. L.; Sablayrolles, J. M.; Barre, P.; Dequin, S.

    1999-01-01

    Six commercial wine yeast strains and three nonindustrial strains (two laboratory strains and one haploid strain derived from a wine yeast strain) were engineered to produce large amounts of glycerol with a lower ethanol yield. Overexpression of the GPD1 gene, encoding a glycerol-3-phosphate dehydrogenase, resulted in a 1.5- to 2.5-fold increase in glycerol production and a slight decrease in ethanol formation under conditions simulating wine fermentation. All the strains overexpressing GPD1 produced a larger amount of succinate and acetate, with marked differences in the level of these compounds between industrial and nonindustrial engineered strains. Acetoin and 2,3-butanediol formation was enhanced with significant variation between strains and in relation to the level of glycerol produced. Wine strains overproducing glycerol at moderate levels (12 to 18 g/liter) reduced acetoin almost completely to 2,3-butanediol. A lower biomass concentration was attained by GPD1-overexpressing strains, probably due to high acetaldehyde production during the growth phase. Despite the reduction in cell numbers, complete sugar exhaustion was achieved during fermentation in a sugar-rich medium. Surprisingly, the engineered wine yeast strains exhibited a significant increase in the fermentation rate in the stationary phase, which reduced the time of fermentation. PMID:9872772

  5. Next-generation sequencing analysis of lager brewing yeast strains reveals the evolutionary history of interspecies hybridization.

    PubMed

    Okuno, Miki; Kajitani, Rei; Ryusui, Rie; Morimoto, Hiroya; Kodama, Yukiko; Itoh, Takehiko

    2016-02-01

    The lager beer yeast Saccharomyces pastorianus is considered an allopolyploid hybrid species between S. cerevisiae and S. eubayanus. Many S. pastorianus strains have been isolated and classified into two groups according to geographical origin, but this classification remains controversial. Hybridization analyses and partial PCR-based sequence data have indicated a separate origin of these two groups, whereas a recent intertranslocation analysis suggested a single origin. To clarify the evolutionary history of this species, we analysed 10 S. pastorianus strains and the S. eubayanus type strain as a likely parent by Illumina next-generation sequencing. In addition to assembling the genomes of five of the strains, we obtained information on interchromosomal translocation, ploidy, and single-nucleotide variants (SNVs). Collectively, these results indicated that the two groups of strains share S. cerevisiae haploid chromosomes. We therefore conclude that both groups of S. pastorianus strains share at least one interspecific hybridization event and originated from a common parental species and that differences in ploidy and SNVs between the groups can be explained by chromosomal deletion or loss of heterozygosity. PMID:26732986

  6. Next-generation sequencing analysis of lager brewing yeast strains reveals the evolutionary history of interspecies hybridization

    PubMed Central

    Okuno, Miki; Kajitani, Rei; Ryusui, Rie; Morimoto, Hiroya; Kodama, Yukiko; Itoh, Takehiko

    2016-01-01

    The lager beer yeast Saccharomyces pastorianus is considered an allopolyploid hybrid species between S. cerevisiae and S. eubayanus. Many S. pastorianus strains have been isolated and classified into two groups according to geographical origin, but this classification remains controversial. Hybridization analyses and partial PCR-based sequence data have indicated a separate origin of these two groups, whereas a recent intertranslocation analysis suggested a single origin. To clarify the evolutionary history of this species, we analysed 10 S. pastorianus strains and the S. eubayanus type strain as a likely parent by Illumina next-generation sequencing. In addition to assembling the genomes of five of the strains, we obtained information on interchromosomal translocation, ploidy, and single-nucleotide variants (SNVs). Collectively, these results indicated that the two groups of strains share S. cerevisiae haploid chromosomes. We therefore conclude that both groups of S. pastorianus strains share at least one interspecific hybridization event and originated from a common parental species and that differences in ploidy and SNVs between the groups can be explained by chromosomal deletion or loss of heterozygosity. PMID:26732986

  7. Marine yeasts as biocontrol agents and producers of bio-products.

    PubMed

    Chi, Zhen-Ming; Liu, Guanglei; Zhao, Shoufeng; Li, Jing; Peng, Ying

    2010-05-01

    As some species of marine yeasts can colonize intestine of marine animals, they can be used as probiotics. It has been reported that beta-glucans from marine yeast cells can be utilized as immuno-stimulants in marine animals. Some siderophores or killer toxins produced by marine yeasts have ability to inhibit growth of pathogenic bacteria or kill pathogenic yeasts in marine animals. The virulent factors from marine pathogens can be genetically displayed on marine yeast cells, and the yeast cells displaying the virulent factors can stimulate marine animals to produce specific antibody against the pathogens. Some marine yeast cells are rich in proteins and essential amino acids and can be used in nutrition for marine animals. The marine yeast cells rich in lipid can be used for biodiesel production. Recently, it has been reported that some strains of Yarrowia lipolytica isolated from marine environments can produce nanoparticles. Because many marine yeasts can remove organic pollutants and heavy metals, they can be applied to remediation of marine environments. It has been shown that the enzymes produced by some marine yeasts have many unique properties and many potential applications. PMID:20195858

  8. Production of a yeast artificial chromosome for stable expression of a synthetic xylose isomerase-xylulokinase polyprotein in a fuel ethanol yeast strain

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Commercialization of fuel ethanol production from lignocellulosic biomass has focused on engineering the glucose-fermenting industrial yeast Saccharomyces cerevisiae to utilize pentose sugars. A yeast artificial chromosome (YAC) was engineered to contain a polyprotein gene construct expressing xylos...

  9. Development of strains of the thermotolerant yeast Hansenula polymorpha capable of alcoholic fermentation of starch and xylan.

    PubMed

    Voronovsky, Andriy Y; Rohulya, Olha V; Abbas, Charles A; Sibirny, Andriy A

    2009-01-01

    The thermotolerant yeast Hansenula polymorpha ferments glucose and xylose to ethanol at high temperatures. However, H. polymorpha cannot utilize starchy materials or xylans. Heterologous amylolytic and xylanolytic enzymes have to be expressed in this yeast to provide for utilization and growth on starch and xylan. Genes SWA2 and GAM1 from the yeast Schwanniomyces occidentalis, encoding alpha-amylase and glucoamylase, respectively, were expressed in H. polymorpha. The expression was achieved by integration of the SWA2 and GAM1 genes under the strong constitutive promoter of the H. polymorpha glyceraldehyde-3-phosphate dehydrogenase gene (HpGAP) into H. polymorpha genome. Resulting transformants acquired the ability to grow on a minimal medium containing soluble starch as a sole carbon source. Ethanol production at high-temperature fermentation from starch by the recombinant strains was up to 10 g/L. The XYN2 gene encoding endoxylanase of the fungus Trichoderma reseei was expressed in H. polymorpha. Co-expression of xlnD gene coding for beta-xylosidase of the fungus Aspergillus niger and the XYN2 gene in H. polymorpha was achieved by integration of these genes under control of the HpGAP promoter. Resulting transformants were capable of growth and alcoholic fermentation on a minimal medium supplemented with birchwood xylan as a sole carbon source at 48 degrees C. PMID:19379821

  10. Genetic Instability of Heterozygous, Hybrid, Natural Wine Yeasts

    PubMed Central

    Ramírez, Manuel; Vinagre, Antonia; Ambrona, Jesús; Molina, Felipe; Maqueda, Matilde; Rebollo, JoséE.

    2004-01-01

    We describe a genetic instability found in natural wine yeasts but not in the common laboratory strains of Saccharomyces cerevisiae. Spontaneous cyh2R/cyh2R mutants resistant to high levels of cycloheximide can be directly isolated from cyh2S/cyh2S wine yeasts. Heterozygous cyh2R/cyh2S hybrid clones vary in genetic instability as measured by loss of heterozygosity at cyh2. There were two main classes of hybrids. The lawn hybrids have high genetic instability and generally become cyh2R/cyh2R homozygotes and lose the killer phenotype under nonselective conditions. The papilla hybrids have a much lower rate of loss of heterozygosity and maintain the killer phenotype. The genetic instability in lawn hybrids is 3 to 5 orders of magnitude greater than the highest loss-of-heterozygosity rates previously reported. Molecular mechanisms such as DNA repair by break-induced replication might account for the asymmetrical loss of heterozygosity. This loss-of-heterozygosity phenomenon could be economically important if it causes sudden phenotype changes in industrial or pathogenic yeasts and of more basic importance to the degree that it influences the evolution of naturally occurring yeast populations. PMID:15294803

  11. Construction from a single parent of baker's yeast strains with high freeze tolerance and fermentative activity in both lean and sweet doughs.

    PubMed

    Nakagawa, S; Ouchi, K

    1994-10-01

    From a freeze-tolerant baker's yeast (Saccharomyces cerevisiae), 2,333 spore clones were obtained. To improve the leavening ability in lean dough of the parent strain, we selected 555 of the high-maltose-fermentative spore clones by using a method in which a soft agar solution containing maltose and bromocresol purple was overlaid on yeast colonies. By measuring the gassing power in the dough, we selected 66 spore clones with a good leavening ability in lean dough and a total of 694 hybrids were constructed by crossing them. Among these hybrids, we obtained 50 novel freeze-tolerant strains with good leavening ability in all lean, regular, and sweet doughs comparable to that of commercial baker's yeast. Hybrids with improved leavening ability or freeze tolerance compared with the parent yeast and commercial baker's yeasts were also obtained. These results suggest that hybridization between spore clones derived from a single parent strain is effective for improving the properties of baker's yeasts. PMID:7986027

  12. Effect of different aging techniques on the polysaccharide and phenolic composition and sensory characteristics of Syrah red wines fermented using different yeast strains.

    PubMed

    del Barrio-Galán, Rubén; Medel-Marabolí, Marcela; Peña-Neira, Álvaro

    2015-07-15

    The effect of high levels of the polysaccharide Saccharomyces cerevisiae yeast strain (HPS) and another conventional yeast strain (FERM) on the polysaccharide and phenolic composition of Syrah red wines during alcoholic fermentation and subsequent aging on lees, with or without oak wood chips, and on inactive dry yeast was investigated. The HPS yeast released higher amounts of polysaccharides during alcoholic fermentation than FERM yeast (485 g L(-1) and 403 g L(-1), respectively) and after the aging period (516 g L(-1) and 500 g L(-1), respectively). The different aging techniques increased the polysaccharide concentration; the concentration was dependent on the aging technique applied. The interaction of the polysaccharides with the phenolic compounds depended on the yeast strain, aging technique, aging period and compound analysed. The HPS wines exhibited better sensory characteristics than the FERM wines after alcoholic fermentation; however, during the aging period, it was difficult to determine which technique produced the best wine due to the interactions of aging technique, aging period and sensory attribute evaluated. PMID:25722146

  13. Induction of ploidy level increments in an asporogenous industrial strain of the yeast Saccharomyces cerevisiae by UV irradiation.

    PubMed Central

    Sasaki, T

    1992-01-01

    Cells of an asporogenous industrial strain of the yeast Saccharomyces cerevisiae were irradiated with UV light by using a method that was developed previously (T. Sasaki and Y. Ohshima, Appl. Environ. Microbiol. 53:1504-1511, 1987). This treatment gave rise to large-cell clones among the surviving cells, from which colonies consisting of cells with a normal morphology and a prototrophic property were obtained. The large-cell trait of these was stably inheritable, with the cell volumes being about twice that of the parent for 7 years on a slant agar medium at 4 degrees C with repeated transfers. The cellular DNA content of these clones, in comparison to those of two authentic haploid strains, was determined by chemical analysis. The ratio of the DNA contents showed that the parent and its large-cell derivatives were a diploid and tetraploids, respectively. No abnormality was found in the chromosomal DNA patterns of the large-cell clones, at least as determined by agarose gel electrophoresis with a CHEF-DR II pulsed-field electrophoresis system. These findings led to the conclusion that our UV light method is applicable for inducing ploidy level increments in the widely used yeast species S. cerevisiae. Images PMID:1575498

  14. Optimised quantification of the antiyeast activity of different barley malts towards a lager brewing yeast strain.

    PubMed

    van Nierop, Sandra N E; Axcell, Barry C; Cantrell, Ian C; Rautenbach, Marina

    2008-10-01

    The brewing of beer involves two major biological systems, namely malted barley (malt) and yeast. Both malt and yeast show natural variation and assessing the impact of differing malts on yeast performance is important in the optimisation of the brewing process. Currently, the brewing industry uses well-established tests to assess malt quality, but these frequently fail to predict malt-associated problem fermentations, such as incomplete fermentations, premature yeast flocculation (PYF) and gushing of the final beer product. Antimicrobial compounds, and in particular antiyeast compounds in malt, may be one of the unknown and unmeasured malt factors leading to problem fermentations. In this study, the adaptation of antimicrobial assays for the determination of antiyeast activity in malt is described. Our adapted assay was able to detect differing antiyeast activities in nine malt samples. For this sample set, malts associated with PYF during fermentation and gushing activity in beer showed high antiyeast activity. Both PYF and gushing are malt quality issues associated with fungal infection of barley in the field which may result in elevated antimicrobial activity in the barley grain. Also, two more malts that passed the normal quality control tests were also observed to have high antiyeast activity and such malts must be considered as suspect. Based on our results, this assay is a useful measure of malt quality as it quantifies the antiyeast activity in malt which may adversely impact on brewery fermentation. PMID:18721679

  15. Reconstruction of thermotolerant yeast by one-point mutation identified through whole-genome analyses of adaptively-evolved strains

    PubMed Central

    Satomura, Atsushi; Miura, Natsuko; Kuroda, Kouichi; Ueda, Mitsuyoshi

    2016-01-01

    Saccharomyces cerevisiae is used as a host strain in bioproduction, because of its rapid growth, ease of genetic manipulation, and high reducing capacity. However, the heat produced during the fermentation processes inhibits the biological activities and growth of the yeast cells. We performed whole-genome sequencing of 19 intermediate strains previously obtained during adaptation experiments under heat stress; 49 mutations were found in the adaptation steps. Phylogenetic tree revealed at least five events in which these strains had acquired mutations in the CDC25 gene. Reconstructed CDC25 point mutants based on a parental strain had acquired thermotolerance without any growth defects. These mutations led to the downregulation of the cAMP-dependent protein kinase (PKA) signaling pathway, which controls a variety of processes such as cell-cycle progression and stress tolerance. The one-point mutations in CDC25 were involved in the global transcriptional regulation through the cAMP/PKA pathway. Additionally, the mutations enabled efficient ethanol fermentation at 39 °C, suggesting that the one-point mutations in CDC25 may contribute to bioproduction. PMID:26984760

  16. The Interaction between Saccharomyces cerevisiae and Non-Saccharomyces Yeast during Alcoholic Fermentation Is Species and Strain Specific

    PubMed Central

    Wang, Chunxiao; Mas, Albert; Esteve-Zarzoso, Braulio

    2016-01-01

    The present study analyzes the lack of culturability of different non-Saccharomyces strains due to interaction with Saccharomyces cerevisiae during alcoholic fermentation. Interaction was followed in mixed fermentations with 1:1 inoculation of S. cerevisiae and ten non-Saccharomyces strains. Starmerella bacillaris, and Torulaspora delbrueckii indicated longer coexistence in mixed fermentations compared with Hanseniaspora uvarum and Metschnikowia pulcherrima. Strain differences in culturability and nutrient consumption (glucose, alanine, ammonium, arginine, or glutamine) were found within each species in mixed fermentation with S. cerevisiae. The interaction was further analyzed using cell-free supernatant from S. cerevisiae and synthetic media mimicking both single fermentations with S. cerevisiae and using mixed fermentations with the corresponding non-Saccharomyces species. Cell-free S. cerevisiae supernatants induced faster culturability loss than synthetic media corresponding to the same fermentation stage. This demonstrated that some metabolites produced by S. cerevisiae played the main role in the decreased culturability of the other non-Saccharomyces yeasts. However, changes in the concentrations of main metabolites had also an effect. Culturability differences were observed among species and strains in culture assays and thus showed distinct tolerance to S. cerevisiae metabolites and fermentation environment. Viability kit and recovery analyses on non-culturable cells verified the existence of viable but not-culturable status. These findings are discussed in the context of interaction between non-Saccharomyces and S. cerevisiae. PMID:27148191

  17. The Interaction between Saccharomyces cerevisiae and Non-Saccharomyces Yeast during Alcoholic Fermentation Is Species and Strain Specific.

    PubMed

    Wang, Chunxiao; Mas, Albert; Esteve-Zarzoso, Braulio

    2016-01-01

    The present study analyzes the lack of culturability of different non-Saccharomyces strains due to interaction with Saccharomyces cerevisiae during alcoholic fermentation. Interaction was followed in mixed fermentations with 1:1 inoculation of S. cerevisiae and ten non-Saccharomyces strains. Starmerella bacillaris, and Torulaspora delbrueckii indicated longer coexistence in mixed fermentations compared with Hanseniaspora uvarum and Metschnikowia pulcherrima. Strain differences in culturability and nutrient consumption (glucose, alanine, ammonium, arginine, or glutamine) were found within each species in mixed fermentation with S. cerevisiae. The interaction was further analyzed using cell-free supernatant from S. cerevisiae and synthetic media mimicking both single fermentations with S. cerevisiae and using mixed fermentations with the corresponding non-Saccharomyces species. Cell-free S. cerevisiae supernatants induced faster culturability loss than synthetic media corresponding to the same fermentation stage. This demonstrated that some metabolites produced by S. cerevisiae played the main role in the decreased culturability of the other non-Saccharomyces yeasts. However, changes in the concentrations of main metabolites had also an effect. Culturability differences were observed among species and strains in culture assays and thus showed distinct tolerance to S. cerevisiae metabolites and fermentation environment. Viability kit and recovery analyses on non-culturable cells verified the existence of viable but not-culturable status. These findings are discussed in the context of interaction between non-Saccharomyces and S. cerevisiae. PMID:27148191

  18. Yeast extract promotes decolorization of azo dyes by stimulating azoreductase activity in Shewanella sp. strain IFN4.

    PubMed

    Imran, Muhammad; Arshad, Muhammad; Negm, Fayek; Khalid, Azeem; Shaharoona, Baby; Hussain, Sabir; Mahmood Nadeem, Sajid; Crowley, David E

    2016-02-01

    Biological treatment of azo dyes commonly requires a combined anaerobic-aerobic process in which initial decolorization is achieved by reductive cleavage of azo bonds on the parent molecule. The present study was conducted to examine the relative importance of co-substrates for driving reductive decolorization of azo dyes by Shewanella sp. strain IFN4 using whole cells and enzyme assays. Results showed that the dye decolorization by strain IFN4 was faster in medium containing 1gL(-1) yeast extract (YE) as compared to nine other co-substrates. Moreover, only YE stimulated azoreductase activity (increased from 1.32 to 4.19U/mg protein). Increasing the level of YE up to 8gL(-)(1) resulted into 81% decolorization of the dye in 1h along with an increase in azoreductase activity up to 6.16U/mg protein. Among the components of YE, only riboflavin stimulated the decolorization process as well as enzyme activity. Moreover, strain IFN4 demonstrated flavin reductase activity, and a significant correlation (r(2)=0.98) between flavin reduction and dye reduction by this strain emphasized the involvement of flavin compounds in the decolorization process. The results of this study show that YE serves both as a source of reducing equivalents and an electron shuttle for catalyzing dye reduction. PMID:26454074

  19. The virally encoded killer proteins from Ustilago maydis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Several strains of Ustilago maydis, a causal agent of corn smut disease, exhibit a 'killer' phenotype that is due to persistent infection by double-stranded RNA Totiviruses. These viruses produce potent killer proteins that are secreted by the host. This is a rare example of virus/host symbiosis in ...

  20. Construction of an industrial brewing yeast strain to manufacture beer with low caloric content and improved flavor.

    PubMed

    Wang, Jin-Jing; Wang, Zhao-Yue; Liu, Xi-Feng; Guo, Xue-Na; He, Xiu-Ping; Wensel, Pierre Christian; Zhang, Bo-Run

    2010-04-01

    In this study, the problems of high caloric content, increased maturation time and off-flavors in commercial beer manufacture arising from residual sugar, diacetyl, and acetaldehyde levels were addressed. A recombinant industrial brewing yeast strain (TQ1) was generated from T1 [Lipomyces starkeyi dextranase gene (LSD1) introduced, alpha-acetohydroxyacid synthase gene (ILV2) disrupted] by introducing Saccharomyces cerevisiae glucoamylase (SGA1) and a strong promoter PGK1 while disrupting the genes coding alcohol dehydrogenase (ADH2). The highest glucoamylase activity for TQ1 was 93.26 U/ml compared with host strain T1 (12.36 U/ml) and wild-type industrial yeast strain YSF5 (10.39 U/ml), respectively. European Brewery Convention (EBC) tube fermentation tests comparing the fermentation broths of TQ1 with T1 and YSF5 showed that the real extract were reduced by 15.79% and 22.47%; the main residual maltotriose concentration were reduced by 13.75% and 18.82%; the caloric content were reduced by 27.18 and 35.39 calories per 12 oz. Due to the disruption of ADH2 gene in TQ1, the off-flavor acetaldehyde concentration in the fermentation broth were 9.43% and 13.28% respectively lower than that of T1 and YSF5. No heterologous DNA sequences or drug-resistance genes were introduced into TQ1. So, the gene manipulations in this work properly solved the addressed problems in commercial beer manufacture. PMID:20467251

  1. Outlining a future for non-Saccharomyces yeasts: selection of putative spoilage wine strains to be used in association with Saccharomyces cerevisiae for grape juice fermentation.

    PubMed

    Domizio, Paola; Romani, Cristina; Lencioni, Livio; Comitini, Francesca; Gobbi, Mirko; Mannazzu, Ilaria; Ciani, Maurizio

    2011-06-30

    The use of non-Saccharomyces yeasts that are generally considered as spoilage yeasts, in association with Saccharomyces cerevisiae for grape must fermentation was here evaluated. Analysis of the main oenological characteristics of pure cultures of 55 yeasts belonging to the genera Hanseniaspora, Pichia, Saccharomycodes and Zygosaccharomyces revealed wide biodiversity within each genus. Moreover, many of these non-Saccharomyces strains had interesting oenological properties in terms of fermentation purity, and ethanol and secondary metabolite production. The use of four non-Saccharomyces yeasts (one per genus) in mixed cultures with a commercial S. cerevisiae strain at different S. cerevisiae/non-Saccharomyces inoculum ratios was investigated. This revealed that most of the compounds normally produced at high concentrations by pure cultures of non-Saccharomyces, and which are considered detrimental to wine quality, do not reach threshold taste levels in these mixed fermentations. On the other hand, the analytical profiles of the wines produced by these mixed cultures indicated that depending on the yeast species and the S. cerevisiae/non-Saccharomyces inoculum ratio, these non-Saccharomyces yeasts can be used to increase production of polysaccharides and to modulate the final concentrations of acetic acid and volatile compounds, such as ethyl acetate, phenyl-ethyl acetate, 2-phenyl ethanol, and 2-methyl 1-butanol. PMID:21531033

  2. Development and use of a quantum dot probe to track multiple yeast strains in mixed culture

    PubMed Central

    Gustafsson, Frida S.; Whiteside, Matthew D.; Jiranek, Vladimir; Durall, Daniel M.

    2014-01-01

    Saccharomyces cerevisiae strains vary in their ability to develop and enhance sensory attributes of alcoholic beverages and are often found growing in mixed strain fermentations; however, quantifying individual strains is challenging due to quantification inaccuracies, low marker longevity, and compromised kinetics. We developed a fluorescent probe, consisting of glutathione molecules conjugated to a quantum dot (QD). Two S. cerevisiae strains were incubated with different coloured probes (QD attached to glutathione molecules, QD-GSH), fermented at multiple ratios, and quantified using confocal microscopy. The QD method was compared with a culture method using microsatellite DNA analysis (MS method). Probes were taken up by an ADP1 encoded transporter, transferred from mother cell to daughter cell, detectable in strains throughout fermentation, and were non-toxic. This resulted in a new quantification method that was more accurate and efficient than the MS method. PMID:25382600

  3. Conversion of the mycotoxin patulin to the less toxic desoxypatulinic acid by the biocontrol yeast Rhodosporidium kratochvilovae strain LS11.

    PubMed

    Castoria, Raffaello; Mannina, Luisa; Durán-Patrón, Rosa; Maffei, Francesca; Sobolev, Anatoly P; De Felice, Dario V; Pinedo-Rivilla, Cristina; Ritieni, Alberto; Ferracane, Rosalia; Wright, Sandra A I

    2011-11-01

    The infection of stored apples by the fungus Penicillium expansum causes the contamination of fruits and fruit-derived products with the mycotoxin patulin, which is a major issue in food safety. Fungal attack can be prevented by beneficial microorganisms, so-called biocontrol agents. Previous time-course thin layer chromatography analyses showed that the aerobic incubation of patulin with the biocontrol yeast Rhodosporidium kratochvilovae strain LS11 leads to the disappearance of the mycotoxin spot and the parallel emergence of two new spots, one of which disappears over time. In this work, we analyzed the biodegradation of patulin effected by LS11 through HPLC. The more stable of the two compounds was purified and characterized by nuclear magnetic resonance as desoxypatulinic acid, whose formation was also quantitated in patulin degradation experiments. After R. kratochvilovae LS11 had been incubated in the presence of (13)C-labeled patulin, label was traced to desoxypatulinic acid, thus proving that this compound derives from the metabolization of patulin by the yeast. Desoxypatulinic acid was much less toxic than patulin to human lymphocytes and, in contrast to patulin, did not react in vitro with the thiol-bearing tripeptide glutathione. The lower toxicity of desoxypatulinic acid is proposed to be a consequence of the hydrolysis of the lactone ring and the loss of functional groups that react with thiol groups. The formation of desoxypatulinic acid from patulin represents a novel biodegradation pathway that is also a detoxification process. PMID:21928828

  4. Inactive and mutagenic effects induced by carbon beams of different LET values in a red yeast strain

    NASA Astrophysics Data System (ADS)

    Wang, Jufang; Lu, Dong; Wu, Xin; Sun, Haining; Ma, Shuang; Li, Renmin; Li, Wenjian

    2010-09-01

    To evaluate biological action of microorganism exposed to charged particles during the long distance space exploration, induction of inactivation and mutation in a red yeast strain Rhodotorula glutinis AY 91015 by carbon beams of different LET values (14.9-120.0 keV μm -1) was investigated. It was found that survival curves were exponential, and mutation curves were linear for all LET values. The dependence of inactivation cross section on LET approached saturation near 120.0 keV μm -1. The mutation cross section saturated when LET was higher than 58.2 keV μm -1. Meanwhile, the highest RBE i for inactivation located at 120.0 keV μm -1 and the highest RBE m for mutation was at 58.2 keV μm -1. The experiments imply that the most efficient mutagenic part of the depth dose profile of carbon ion is at the plateau region with intermediate LET value in which energy deposited is high enough to induce mutagenic lesions but too low to induce over kill effect in the yeast cells.

  5. Selection of aroma compounds for the differentiation of wines obtained by fermenting musts with starter cultures of commercial yeast strains.

    PubMed

    Vararu, Florin; Moreno-García, Jaime; Zamfir, Cătălin-Ioan; Cotea, Valeriu V; Moreno, Juan

    2016-04-15

    Nine wines obtained by fermenting Aligoté musts with individual starter cultures of eight Saccharomyces cerevisiae yeast strains and with the indigenous microbiota were compared in terms of their composition in minor volatile aroma compounds. An easy handle methodology Stir-Bar-Sorptive-Adsorption, Gas Chromatography-Mass Spectrometry based, permits the identification of 49 aroma compounds. The rearrangement of these aroma compounds in six chemical families permits the establishment of a finger printing for each wine. Eighteen aroma compounds that exhibit a high differentiation power (p⩽0.05) were selected for chemometric analysis. The Principal Component Analysis carried out with these aroma compounds reveal that the first two principal components explain 53.8% and 17.2% of the total variance, respectively, allowing the establishment of nine different groups, in accordance with the wine types obtained. These results reveal analytical differences among the wines that are not recognized by sensorial analysis. PMID:26616963

  6. Fully automated molecular biology routines on a plasmid-based functional proteomic workcell: Evaluation and Characterization of Yeast Strains Optimized for Growth on Xylose Expressing "Stealth" Insecticidal Peptides.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optimization of genes important to production of fuel ethanol from hemicellulosic biomass for use in developing improved commercial yeast strains is necessary to meet the rapidly expanding need for ethanol. The United States Department of Agriculture has developed a fully automated platform for mol...

  7. Regulatory concerns associated with use of value-added recombinant proteins and peptides screened in hgh-throughput for expression in fuel ethanol yeast strains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recombinant proteins expressed in animals have been a public concern as a risk to the consumer since the animals are genetically modified to obtain desired improvements (GMO animals). Similarly, various commercially valuable proteins or peptides expressed in fuel ethanol yeast strains under develop...

  8. Comparison of the Sensititre YeastOne® dilution method with the Clinical Laboratory Standards Institute (CLSI) M27-A3 microbroth dilution reference method for determining MIC of eight antifungal agents on 102 yeast strains.

    PubMed

    Bertout, S; Dunyach, C; Drakulovski, P; Reynes, J; Mallié, M

    2011-02-01

    The Clinical Laboratory Standards Institute ([CLSI] formerly NCCLS) reference broth microdilution testing method (protocol M27-A3) was compared with a commercially available methods (Sensititre YeastOne(®)) by testing two quality control strains and 102 isolates of Candida sp. and Cryptococcus sp. against fluconazole, itraconazole, ketoconazole, posaconazole, voriconazole, flucytosin, amphotericin B and caspofungin. Minimal inhibitory concentrations (MIC) endpoints were determined after 24h of incubation for Sensititre YeastOne(®) and after 24 and 48 h for CLSI microdilution method. Essential agreements between methods vary from 70.6 to 92.2%. Categorical agreements vary from 94.1% for 5FC to 72.6% for AMB. Sensititre YeastOne(®) reading appears to be useful for avoiding very major errors and this confirms the interest of this method for evaluating new antifungals activity in vitro. PMID:20843616

  9. Preliminary comparison of ethanol production characteristics of a respiratory deficient yeast strain

    SciTech Connect

    Garcia, A. III; Grillione, P.

    1981-01-01

    Barley was fermented with a defined strain of saccharomyces cerevisiae and a chemically induced respiratory deficient mutant (R.D.). Specific gravity, pH, CO/sub 2/ production and ethanol yield were continually monitored. Ethanol production rates and yield are compared. R.D. fermentations were slower buy yielded slightly more ethanol after a considerable time. Some reversion to a respiratory capable strain was identified. 11 refs.

  10. Gentamicin-Containing Peptone-Yeast Extract Medium for Cocultivation of Hartmannella vermiformis ATCC 50256 and Virulent Strains of Legionella pneumophila

    PubMed Central

    Wadowsky, R. M.; Wang, L.; Laus, S.; Dowling, J. N.; Kuchta, J. M.; States, S. J.; Yee, R. B.

    1995-01-01

    We evaluated the use of peptone-yeast extract (PY) medium, different strains of Hartmannella vermiformis, and gentamicin in a coculture system to improve the discrimination of virulent and avirulent strains of Legionella pneumophila. H. vermiformis ATCC 50256 was unique among four strains of H. vermiformis, in that it multiplied equally well in Medium 1034 and PY medium (Medium 1034 without fetal calf serum, folic acid, hemin, and yeast nucleic acid and with a 50% reduction of peptone). However, both a virulent strain of L. pneumophila and its avirulent derivative strain multiplied in cocultures when PY medium was used. The multiplication of this avirulent strain was greatly reduced by incorporating gentamicin (1 (mu)g/ml) into the cocultivation system. Five virulent-avirulent sets of L. pneumophila strains were then tested for multiplication in cocultures with H. vermiformis ATCC 50256 and the gentamicin-containing PY medium. Only the virulent strains multiplied. The modified cocultivation system can discriminate between virulent and avirulent strains of L. pneumophila. PMID:16535197

  11. Characteristics of Saccharomyces cerevisiae yeasts exhibiting rough colonies and pseudohyphal morphology with respect to alcoholic fermentation

    PubMed Central

    Reis, Vanda Renata; Bassi, Ana Paula Guarnieri; da Silva, Jessica Carolina Gomes; Ceccato-Antonini, Sandra Regina

    2013-01-01

    Among the native yeasts found in alcoholic fermentation, rough colonies associated with pseudohyphal morphology belonging to the species Saccharomyces cerevisiae are very common and undesirable during the process. The aim of this work was to perform morphological and physiological characterisations of S. cerevisiae strains that exhibited rough and smooth colonies in an attempt to identify alternatives that could contribute to the management of rough colony yeasts in alcoholic fermentation. Characterisation tests for invasiveness in Agar medium, killer activity, flocculation and fermentative capacity were performed on 22 strains (11 rough and 11 smooth colonies). The effects of acid treatment at different pH values on the growth of two strains (“52” - rough and “PE-02” - smooth) as well as batch fermentation tests with cell recycling and acid treatment of the cells were also evaluated. Invasiveness in YPD Agar medium occurred at low frequency; ten of eleven rough yeasts exhibited flocculation; none of the strains showed killer activity; and the rough strains presented lower and slower fermentative capacities compared to the smooth strains in a 48-h cycle in a batch system with sugar cane juice. The growth of the rough strain was severely affected by the acid treatment at pH values of 1.0 and 1.5; however, the growth of the smooth strain was not affected. The fermentative efficiency in mixed fermentation (smooth and rough strains in the same cell mass proportion) did not differ from the efficiency obtained with the smooth strain alone, most likely because the acid treatment was conducted at pH 1.5 in a batch cell-recycle test. A fermentative efficiency as low as 60% was observed with the rough colony alone. PMID:24688501

  12. The KP4 killer protein gene family

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Killer protein 4 (KP4) is a well studied toxin secreted by the maize smut fungus Ustilago maydis that kills sensitive Ustilago strains as well as inhibits Fusarium and plant root growth. This small, cysteine rich protein is encoded by a virus that depends on host survival for replication. KP4 functi...

  13. Population Structure and Comparative Genome Hybridization of European Flor Yeast Reveal a Unique Group of Saccharomyces cerevisiae Strains with Few Gene Duplications in Their Genome

    PubMed Central

    Legras, Jean-Luc; Erny, Claude; Charpentier, Claudine

    2014-01-01

    Wine biological aging is a wine making process used to produce specific beverages in several countries in Europe, including Spain, Italy, France, and Hungary. This process involves the formation of a velum at the surface of the wine. Here, we present the first large scale comparison of all European flor strains involved in this process. We inferred the population structure of these European flor strains from their microsatellite genotype diversity and analyzed their ploidy. We show that almost all of these flor strains belong to the same cluster and are diploid, except for a few Spanish strains. Comparison of the array hybridization profile of six flor strains originating from these four countries, with that of three wine strains did not reveal any large segmental amplification. Nonetheless, some genes, including YKL221W/MCH2 and YKL222C, were amplified in the genome of four out of six flor strains. Finally, we correlated ICR1 ncRNA and FLO11 polymorphisms with flor yeast population structure, and associate the presence of wild type ICR1 and a long Flo11p with thin velum formation in a cluster of Jura strains. These results provide new insight into the diversity of flor yeast and show that combinations of different adaptive changes can lead to an increase of hydrophobicity and affect velum formation. PMID:25272156

  14. Gene expression analysis using strains constructed by NHEJ-mediated one-step promoter cloning in the yeast Kluyveromyces marxianus.

    PubMed

    Suzuki, Ayako; Fujii, Hiroshi; Hoshida, Hisashi; Akada, Rinji

    2015-09-01

    Gene expression analysis provides valuable information to evaluate cellular state. Unlike quantitative mRNA analysis techniques like reverse-transcription PCR and microarray, expression analysis using a reporter gene has not been commonly used for multiple-gene analysis, probably due to the difficulty in preparing multiple reporter-gene constructs. To circumvent this problem, we developed a novel one-step reporter-gene construction system mediated by non-homologous end joining (NHEJ) in the yeast Kluyveromyces marxianus. As a selectable reporter gene, the ScURA3 selection marker was fused in frame with a red fluorescent gene yEmRFP (ScURA3:yEmRFP). The N-terminally truncated ScURA3:yEmRFP fragment was prepared by PCR. Promoter sequences were also prepared by PCR using primers containing the sequence of the deleted ScURA3 N-terminus to attach at their 3(') ends. The two DNA fragments were used for the transformation of a ura3(-) strain of K. marxianus, in which two DNA fragments are randomly joined and integrated into the chromosome through NHEJ. Only the correctly aligned fragments produced transformants on uracil-deficient medium and expressed red fluorescence under the control of the introduced promoters. A total of 36 gene promoters involved in glycolysis and other pathways were analyzed. Fluorescence measurements of these strains allowed real-time gene expression analysis in different culture conditions. PMID:26136515

  15. Effects of the strain background and autolysis process on the composition and biophysical properties of the cell wall from two different industrial yeasts.

    PubMed

    Schiavone, Marion; Sieczkowski, Nathalie; Castex, Mathieu; Dague, Etienne; Marie François, Jean

    2015-03-01

    The Saccharomyces cerevisiae cell surface is endowed with some relevant technological properties, notably antimicrobial and biosorption activities. For these purposes, yeasts are usually processed and packaged in an 'autolysed/dried' formula, which may have some impacts on cell surface properties. In this report, we showed using a combination of biochemical, biophysical and molecular methods that the composition of the cell wall of two wine yeast strains was not altered by the autolysis process. In contrast, this process altered the nanomechanical properties as shown by a 2- to 4-fold increased surface roughness and to a higher adhesion to the atomic force microscope tips of the autolysed cells as compared to live yeast cells. Besides, we found that the two strains harboured differences in biomechanical properties that could be due in part to higher levels of mannan in one of them, and to the fact that the surface of this mannan-enriched strain is decorated with highly adhesive patches forming nanodomains. The presence of these nanodomains could be correlated with the upregulation of flocculin encoding FLO11 as well as to higher expression of few other genes encoding cell wall mannoproteins in this mannan-enriched strain as compared to the other strain. PMID:25762053

  16. Thailandins A and B, New Polyene Macrolactone Compounds Isolated from Actinokineospora bangkokensis Strain 44EHW(T), Possessing Antifungal Activity against Anthracnose Fungi and Pathogenic Yeasts.

    PubMed

    Intra, Bungonsiri; Greule, Anja; Bechthold, Andreas; Euanorasetr, Jirayut; Paululat, Thomas; Panbangred, Watanalai

    2016-06-29

    Two new polyene macrolactone antibiotics, thailandins A, 1, and B, 2, were isolated from the fermentation broth of rhizosphere soil-associated Actinokineospora bangkokensis strain 44EHW(T). The new compounds from this strain were purified using semipreparative HPLC and Sephadex LH-20 gel filtration while following an antifungal activity guided fractionation. Their structures were elucidated through spectroscopic techniques including UV, HR-ESI-MS, and NMR. These compounds demonstrated broad spectrum antifungal activity against fungi causing anthracnose disease (Colletotrichum gloeosporioides DoA d0762, Colletotrichum gloeosporiodes DoA c1060, and Colletotrichum capsici DoA c1511) as well as pathogenic yeasts (Candida albicans MT 2013/1, Candida parasilopsis DKMU 434, and Cryptococcus neoformans MT 2013/2) with minimum inhibitory concentrations ranging between 16 and 32 μg/mL. This is the first report of polyene antibiotics produced by Actinokineospora species as bioactive compounds against anthracnose fungi and pathogenic yeast strains. PMID:27267862

  17. Yeast ecology of vineyards within Marsala wine area (western Sicily) in two consecutive vintages and selection of autochthonous Saccharomyces cerevisiae strains.

    PubMed

    Settanni, Luca; Sannino, Ciro; Francesca, Nicola; Guarcello, Rosa; Moschetti, Giancarlo

    2012-12-01

    In this work, the yeast ecology associated with the spontaneous fermentation of Grillo cultivar grapes from 10 vineyards was analyzed from grape harvest till complete consumption of must sugars. The microbiological investigation started with the plate count onto two culture media to distinguish total yeasts (TY) and presumptive Saccharomyces (PS). Yeasts were randomly isolated and identified by a combined genotypic approach consisting of restriction fragment length polymorphism (RFLP) of 5.8S rRNA gene and 26S rRNA and sequencing of D1/D2 domain of the 26S rRNA gene, which resulted in the recognition of 14 species belonging to 10 genera. The distribution of the yeasts within the vineyards showed some differences in species composition and concentration levels among 2008 and 2009 vintages. Due to the enological relevance, all Saccharomyces cerevisiae isolates were differentiated applying two genotypic tools (interdelta analysis and microsatellite multiplex PCR of polymorphic microsatellite loci) that recognized 51 strains. Based on the low production of H(2)S, acetic acid and foam, ethanol resistance, growth in presence of high concentrations of potassium metabisulphite (KMBS) and CuSO(4) and at low temperatures, 14 strains were selected and used as starter to ferment grape must at 13 °C and 17 °C in presence of 100 mg/L of KMBS. Three strains (CS160, CS165 and CS182) showed optimal technological aptitudes. PMID:22877686

  18. Fermentation of Apple Juice with a Selected Yeast Strain Isolated from the Fermented Foods of Himalayan Regions and Its Organoleptic Properties

    PubMed Central

    Kanwar, S. S.; Keshani

    2016-01-01

    Twenty-three Saccharomyces cerevisiae strains isolated from different fermented foods of Western Himalayas have been studied for strain level and functional diversity in our department. Among these 23 strains, 10 S. cerevisiae strains on the basis of variation in their brewing traits were selected to study their organoleptic effect at gene level by targeting ATF1 gene, which is responsible for ester synthesis during fermentation. Significant variation was observed in ATF1 gene sequences, suggesting differences in aroma and flavor of their brewing products. Apple is a predominant fruit in Himachal Pradesh and apple cider is one of the most popular drinks all around the world hence, it was chosen for sensory evaluation of six selected yeast strains. Organoleptic studies and sensory analysis suggested Sc21 and Sc01 as best indigenous strains for soft and hard cider, respectively, indicating their potential in enriching the local products with enhanced quality. PMID:27446050

  19. Fermentation of Apple Juice with a Selected Yeast Strain Isolated from the Fermented Foods of Himalayan Regions and Its Organoleptic Properties.

    PubMed

    Kanwar, S S; Keshani

    2016-01-01

    Twenty-three Saccharomyces cerevisiae strains isolated from different fermented foods of Western Himalayas have been studied for strain level and functional diversity in our department. Among these 23 strains, 10 S. cerevisiae strains on the basis of variation in their brewing traits were selected to study their organoleptic effect at gene level by targeting ATF1 gene, which is responsible for ester synthesis during fermentation. Significant variation was observed in ATF1 gene sequences, suggesting differences in aroma and flavor of their brewing products. Apple is a predominant fruit in Himachal Pradesh and apple cider is one of the most popular drinks all around the world hence, it was chosen for sensory evaluation of six selected yeast strains. Organoleptic studies and sensory analysis suggested Sc21 and Sc01 as best indigenous strains for soft and hard cider, respectively, indicating their potential in enriching the local products with enhanced quality. PMID:27446050

  20. Maltotriose utilization in lager yeast strains: MTT1 encodes a maltotriose transporter.

    PubMed

    Dietvorst, J; Londesborough, J; Steensma, H Y

    2005-07-30

    Maltotriose is the second most abundant fermentable sugar in wort and, due to incomplete fermentation, residual maltotriose in beer causes both quality and economic problems in the brewing industry. To identify genes that might improve utilization of maltotriose, we developed a library containing genomic DNA from four lager strains and a laboratory Saccharomyces cerevisiae strain and isolated transformants that could grow on YP/2% maltotriose in the presence of 3 mg/l of the respiratory inhibitor antimycin A. In this way we found a gene which shared 74% similarity with MPH2 and MPH3, 62% similarity with AGT1 and 91% similarity with MAL61 and MAL31, all encoding known maltose transporters. Moreover, the gene shared an even higher similarity (98%) with the uncharacterized Saccharomyces pastorianus mty1 gene (M. Salema-Oom, unpublished; NCBI Accession No. AJ491328). Therefore, we named the gene MTT1 (mty1-like transporter). We showed that the gene was present in four different lager strains but was absent from the laboratory strain CEN.PK113-7D. The ORF in the plasmid isolated from the library lacks 66 base pairs from the 3'-end of MTT1 but instead contains 54 bp of the vector. We named this ORF MTT1alt (NCBI Accession No. DQ010174). 14C-Maltose and repurified 14C-maltotriose were used to show that MTT1 and, especially, MTT1alt, encode maltose transporters for which the ratio between activities to maltotriose and maltose is higher than for most known maltose transporters. Introduction of MTT1 or MTT1alt into lager strain A15 raised maltotriose uptake by about 17% or 105%, respectively. PMID:16088872

  1. Yeasts in table olive processing: desirable or spoilage microorganisms?

    PubMed

    Arroyo-López, F N; Romero-Gil, V; Bautista-Gallego, J; Rodríguez-Gómez, F; Jiménez-Díaz, R; García-García, P; Querol, A; Garrido-Fernández, A

    2012-11-01

    Yeasts are unicellular eukaryotic microorganisms isolated from many foods, and are commonly found in table olive processing where they can play a double role. On one hand, these microorganisms can produce spoilage of fruits due to the production of bad odours and flavours, the accumulation of CO(2) leading to swollen containers, the clouding of brines, the softening of fruits and the degradation of lactic acid, which is especially harmful during table olive storage and packaging. But on the other hand, fortunately, yeasts also possess desirable biochemical activities (lipase, esterase, β-glucosidase, catalase, production of killer factors, etc.) with important technological applications in this fermented vegetable. Recently, the probiotic potential of olive yeasts has begun to be evaluated because many species are able to resist the passage through the gastrointestinal tract and show beneficial effects on the host. In this way, yeasts may improve consumers' health by decreasing cholesterol levels, inhibiting pathogens, degrading non assimilated compounds, producing antioxidants and vitamins, adhering to intestinal cells or by maintaining epithelial barrier integrity. Many yeast species, usually also found in table olive processing, such as Wicherhamomyces anomalus, Saccharomyces cerevisiae, Pichia membranifaciens and Kluyveromyces lactis, have been reported to exhibit some of these properties. Thus, the selection of the most appropriate strains to be used as starters, alone or in combination with lactic acid bacteria, is a promising research line to develop in a near future which might improve the added value of the commercialized product. PMID:23141644

  2. Characterization of maltotriose transporters from the Saccharomyces eubayanus subgenome of the hybrid Saccharomyces pastorianus lager brewing yeast strain Weihenstephan 34/70.

    PubMed

    Cousseau, F E M; Alves, S L; Trichez, D; Stambuk, B U

    2013-01-01

    The genome from the Saccharomyces pastorianus industrial lager brewing strain Weihenstephan 34/70, a natural Saccharomyces cerevisiae/Saccharomyces eubayanus hybrid, indicated the presence of two different maltotriose transporter genes: a new gene in the S. eubayanus subgenome with 81% of homology to the AGT1 permease from S. cerevisiae, and an amplification of the S. eubayanus MTY1 maltotriose permease previously identified in S. pastorianus yeasts. To characterize these S. eubayanus transporter genes, we used a S. cerevisiae strain deleted in the AGT1 permease and introduced the desired permease gene(s) into this locus through homologous recombination. Our results indicate that both the MTY1 and AGT1 genes from the S. eubayanus subgenome encode functional maltotriose transporters that allow fermentation of this sugar by yeast cells, despite their apparent differences in the kinetics of maltotriose-H(+) symport activity. The presence of two maltotriose transporters in the S. eubayanus subgenome not only highlights the importance of sugar transport for efficient maltotriose utilization by industrial yeasts, but these new genes can be used in breeding and/or selection programs aimed at increasing yeast fitness for the efficient fermentation of brewer's wort. PMID:23061413

  3. Metabolic engineering and classic selection of the yeast Candida famata (Candida flareri) for construction of strains with enhanced riboflavin production.

    PubMed

    Dmytruk, Kostyantyn V; Yatsyshyn, Valentyna Y; Sybirna, Natalia O; Fedorovych, Daria V; Sibirny, Andriy A

    2011-01-01

    Currently, the mutant of the flavinogenic yeast Candida famata dep8 isolated by classic mutagenesis and selection is used for industrial riboflavin production. Here we report on construction of a riboflavin overproducing strain of C. famata using a combination of random mutagenesis based on the selection of mutants resistant to different antimetabolites as well as rational approaches of metabolic engineering. The conventional mutagenesis involved consecutive selection for resistance to riboflavin structural analog 7-methyl-8-trifluoromethyl-10-(1'-d-ribityl)isoalloxazine), 8-azaguanine, 6-azauracil, 2-diazo-5-oxo-L-norleucine and guanosine as well as screening for yellow colonies at high pH. The metabolic engineering approaches involved introduction of additional copies of transcription factor SEF1 and IMH3 (coding for IMP dehydrogenase) orthologs from Debaryomyces hansenii, and the homologous genes RIB1 and RIB7, encoding GTP cyclohydrolase II and riboflavin synthetase, the first and the last enzymes of riboflavin biosynthesis pathway, respectively. Overexpression of the aforementioned genes in riboflavin overproducer AF-4 obtained by classical selection resulted in a 4.1-fold increase in riboflavin production in shake-flask experiments. D. hansenii IMH3 and modified ARO4 genes conferring resistance to mycophenolic acid and fluorophenylalanine, respectively, were successfully used as new dominant selection markers for C. famata. PMID:21040798

  4. Reversion from Suppression to Nonsuppression in SUQ5 [psi+] Strains of Yeast: The Classification of Mutations

    PubMed Central

    Cox, B. S.; Tuite, M. F.; Mundy, C. J.

    1980-01-01

    Reversion from the suppressed to nonsuppressed phenotype in strains of genotype SUQ5 [psi+] ade2-1 his5-2 lys1-1 can1-100 ura3-1 has been induced by treatment with ethyl methanesulphonate, nitrosoguanidine or UV (254 nm) light. Spontaneously occurring revertants have also been selected by two different methods. Reversion has been shown to occur through a variety of nuclear mutations and through mutation of [psi+] to [psi-]. Nuclear mutations included back-mutation of SUQ5, antisuppressor mutations that were recessive, semi-dominant or dominant, and dominant or recessive mutations of genes required for the maintenance of the [psi+] factor. Complementation tests by which the various kinds of mutations could be distinguished from one another were designed. The spectra of spontaneously occurring and induced mutations have been described. PMID:7002720

  5. Screening of Yeasts for Selection of Potential Strains and Their Utilization for In Situ Microbial Detoxification (ISMD) of Sugarcane Bagasse Hemicellulosic Hydrolysate.

    PubMed

    Soares, Luma C S R; Chandel, Anuj K; Pagnocca, Fernando C; Gaikwad, Swapnil C; Rai, Mahendra; da Silva, Silvio S

    2016-06-01

    Many toxic compounds are produced and released in the hemicellulosic hydrolyzates during the acid pretreatment step, which are required for the disruption of the lignocelluloses matrix and sugars release. The conventional methods of detoxification i.e. overliming, activated charcoal, ion exchange or even membrane-based separations have the limitations in removal of these toxic inhibitors in fermentation process. Hence, it is imperative to explore biological methods to overcome the inhibitors by minimizing the filtration steps, sugar loss and chemical additions. In the present study we screened sixty-four strains of yeasts to select potential strains for detoxification of furfural, acetic acid, ferulic acid, 5-hydroxymethyl furfural (5-HMF) as carbon and energy source. Among these strains Pichia occidentalis M1, Y1'a, Y1'b and Y3' showed a significant decrease in the toxic compounds but we selected two best yeast strains i.e. P. occidentalis Y1'a and P. occidentalis M1 for the further experiments with an aim to remove the fermentation inhibitors. The yeasts P. occidentalis Y1'a and P. occidentalis M1 were grown aerobically in sugarcane bagasse hemicellulose hydrolysate under submerged cultivation. For each yeast, a 2(2) full factorial design was performed considering the variables-pH (4.0 or 5.0) and agitation rate (100 or 300 rpm), and the percentage removal of HMF, furfural, acetic acid and phenols from hemicellulosic hydrolysates were responsive variables. After 96 h of biological treatment, P. occidentalis M1 and P. occidentalis Y1'a showed 42.89 and 46.04 % cumulative removal of inhibitors, respectively. PMID:27570309

  6. Conversion of pentoses by yeasts

    SciTech Connect

    Gong, C.S.; Claypool, T.A.; Maun, C.M.; Mccracken, L.D.; Tsao, G.T.; Ueng, P.P.

    1983-01-01

    The utilization and conversion of D-xylose, D-xyulose, L-arabinose, and xylitol by yeast strains have been investigated with the following results: 1) The majority of yeasts tested utilize D-xylose and produce polyols, ethanol, and organic acids. The type and amount of products formed varies with the yeast strains used. The most commonly detected product is xylitol. 2) The majority of yeasts tested utilize D-xylulose aerobically and fermentatively to produce ethanol, xylitol D-arabitol, and organic acids. The type and amount of products varies depending upon the yeast strains used. 3) Xylitol is a poor carbon and energy source for most yeasts tested. Some yeast strains produce small amounts of ethanol from xylitol. 4) Most yeast strains utilize L-arabinose, and L-arabitol is the common product. Small amounts of ethanol are also produced by some yeast strains. 5) Of the four substrates examined, D-xylulose was the preferred substrate, followed by D-xylose, L-arabinose, and xylitol. 6) Mutant yeast strains that exhibit different metabolic product patterns can be induced and isolated from Candida sp. Saccharomyces cerevisiae, and other yeasts. These mutant strains can be used for ethanol production from D-xylose as well as for the study of metabolic regulation of pentose utilization in yeasts.

  7. The impact of media composition and petite mutation on the longevity of a polyploid brewing yeast strain.

    PubMed

    Powell, C D; Quain, D E; Smart, K A

    2000-07-01

    Ageing in Saccharomyces cerevisiae is a finite phenomenon, determined by replicative, rather than chronological lifespan. Yeast physiological condition is known to influence industrial fermentation performance, however, until recently cellular senescence has not been considered as a brewing yeast stress factor. A polyploid lager yeast (BB11) and a brewery isolate, exhibiting petite mutation were analysed for longevity. It was observed that mitochondrial deficiency induced a reduction in lifespan. In addition, replicative capacity was perceived to be dependent on environmental conditions. PMID:10886614

  8. Microarray data analyses of yeast RNA Pol I subunit RPA12 deletion strain.

    PubMed

    Yadav, Kamlesh Kumar; Rajasekharan, Ram

    2016-06-01

    The ribosomal RNA (rRNA) biosynthesis is the most energy consuming process in all living cells and the majority of total transcription activity is dedicated for synthesizing rRNA. The cells may adjust the synthesis of rRNA with the availability of resources. rRNA is mainly synthesized by RNA polymerase I that is composed of 14 subunits. Deletion of RPA12, 14, 39 and 49 are viable. RPA12 is a very small protein (13.6 kDa), and the amount of protein in the cells is very high (12,000 molecules per cell), but the role of this protein is unknown in other cellular metabolic processes (Kulak et al., 2014 [1]). RPA12 consists of two zinc-binding domains and it is required for the termination of rRNA synthesis (Mullem et al., 2002 [2]). Deletions of RPA12 in Saccharomyces cerevisiae and Schizosaccharomyces pombe cause a conditional growth defect (Nogi et al., 1993 [3]). In S. pombe, C-terminal deletion behaves like wild-type (Imazawa et al., 2001 [4]). This prompted us to investigate in detail the physiological role of RPA12 in S. cerevisiae, we performed the microarray of rpa12 ∆ strain and deposited into Gene Expression Omnibus under GSE68731. The analysis of microarray data revealed that the expression of major cellular metabolism genes is high. The amino acid biosynthesis, nonpolar lipid biosynthesis and glucose metabolic genes are highly expressed. The analyses also revealed that the rpa12 ∆ cells have an uncontrolled synthesis of cell metabolites, so RPA12 could be a master regulator for whole cellular metabolism. PMID:27222810

  9. Engineered Saccharomyces cerevisiae strain for improved xylose utilization with a three-plasmid SUMO yeast expression system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A three-plasmid yeast expression system utilizing the portable small ubiquitin-like modifier (SUMO) vector set combined with the efficient endogenous yeast protease Ulp1 was developed for production of large amounts of soluble functional protein in Saccharomyces cerevisiae. Each vector has a differ...

  10. Efficacy and putative mode of action of native and commercial antagonistic yeasts against postharvest pathogens of pear.

    PubMed

    Lutz, M Cecilia; Lopes, Christian A; Rodriguez, M Eugenia; Sosa, M Cristina; Sangorrín, Marcela P

    2013-06-17

    Putative mechanisms of action associated with the biocontrol capacity of four yeast strains (Cryptoccocus albidus NPCC 1248, Pichia membranifaciens NPCC 1250, Cryptoccocus victoriae NPCC 1263 and NPCC 1259) against Penicillium expansum and Botrytis cinerea were studied by means of in vitro and in situ assays. C. albidus(YP), a commercial yeast was also evaluated for comparative purposes. The yeast strains exhibited a variety of different mechanisms including: wound colonization, germination inhibition, biofilm formation, secretion of killer toxins, competition for nutrient and secretion of hydrolytic enzymes (protease, chitinase and glucanase). The relationship between strains (and their associated antagonist mechanisms) and in situ antagonist activity was also evaluated. Results indicate that mechanisms such as production of hydrolytic enzymes, the ability for colonization of wounds, production of killer toxin and inhibition of germination are the most important for biocontrol activity. Our study indicate that multiple modes of action may explain why P. membranifaciens NPCC 1250 and C. victoriae NPCC 1263 provided excellent control of postharvest pears disease. PMID:23680800

  11. Biocontrol ability and putative mode of action of yeasts against Geotrichum citri-aurantii in citrus fruit.

    PubMed

    Ferraz, Luriany Pompeo; Cunha, Tatiane da; da Silva, Aline Caroline; Kupper, Katia Cristina

    2016-01-01

    Sour rot is a major postharvest disease of citrus fruit and is caused by the fungal pathogen Geotrichum citri-aurantii. A lack of chemicals certified for the control of this disease has led to the consideration of alternative methods and strategies, such as the use of yeasts as biocontrol agents. The purpose of the present study was to test the ability of yeasts isolated from leaves, flowers, fruit, and soil, and six Saccharomyces cerevisiae isolates to control citrus sour rot, to assess the mechanisms of action of the yeast isolates that were demonstrated to be effective for biocontrol, and to identify the most effective yeast isolates for the biocontrol of G. citri-aurantii. In in vivo assays, three yeast isolates (ACBL-23, ACBL-44, and ACBL-77) showed a potential for controlling sour rot in citrus fruits, both preventatively and curatively. Most of the eight yeast isolates that were assessed for a mechanism of action did not produce antifungal compounds in an amount sufficient to inhibit the growth of the pathogen. Additionally, nutrient competition among the yeast strains was not found to be a biocontrol strategy. Instead, killer activity and hydrolytic enzyme production were identified as the major mechanisms involved in the biocontrol activity of the yeasts. Isolates ACBL-23, ACBL-44, and ACBL-77, which controlled sour rot most effectively, were identified as Rhodotorula minuta, Candida azyma, and Aureobasidium pullulans, respectively. To our knowledge, this is the first report of the potential of C. azyma as a biological control agent against a postharvest pathogen and its ability to produce a killer toxin. PMID:27296964

  12. L-arabinose fermenting yeast

    DOEpatents

    Zhang, Min; Singh, Arjun; Knoshaug, Eric; Franden, Mary Ann; Jarvis, Eric; Suominen, Pirkko

    2010-12-07

    An L-arabinose utilizing yeast strain is provided for the production of ethanol by introducing and expressing bacterial araA, araB and araD genes. L-arabinose transporters are also introduced into the yeast to enhance the uptake of arabinose. The yeast carries additional genomic mutations enabling it to consume L-arabinose, even as the only carbon source, and to produce ethanol. Methods of producing ethanol include utilizing these modified yeast strains. ##STR00001##

  13. The Violence of Collection: "Indian Killer"'s Archives

    ERIC Educational Resources Information Center

    Dean, Janet

    2008-01-01

    At the close of Sherman Alexie's "Indian Killer," in a final chapter titled "Creation Story," a killer carries a backpack containing, among other things, "dozens of owl feathers, a scrapbook, and two bloody scalps in a plastic bag." Readers schooled in the psychopathologies of real and fictional serial killers will be familiar with the detail:…

  14. Grass and weed killer poisoning

    MedlinePlus

    Weedoff poisoning; Roundup poisoning ... Glyphosate is the poisonous ingredient in some weed killers. ... Glyphosate is in weed killers with these brand names: Roundup Bronco Glifonox Kleen-up Rodeo Weedoff Other ...

  15. L-arabinose fermenting yeast

    SciTech Connect

    Zhang, Min; Singh, Arjun; Suominen, Pirkko; Knoshaug, Eric; Franden, Mary Ann; Jarvis, Eric

    2014-09-23

    An L-arabinose utilizing yeast strain is provided for the production of ethanol by introducing and expressing bacterial araA, araB and araD genes. L-arabinose transporters are also introduced into the yeast to enhance the uptake of arabinose. The yeast carries additional genomic mutations enabling it to consume L-arabinose, even as the only carbon source, and to produce ethanol. A yeast strain engineered to metabolize arabinose through a novel pathway is also disclosed. Methods of producing ethanol include utilizing these modified yeast strains.

  16. L-arabinose fermenting yeast

    SciTech Connect

    Zhang, Min; Singh, Arjun; Suominen, Pirkko; Knoshaug, Eric; Franden, Mary Ann; Jarvis, Eric

    2013-02-12

    An L-arabinose utilizing yeast strain is provided for the production of ethanol by introducing and expressing bacterial araA, araB and araD genes. L-arabinose transporters are also introduced into the yeast to enhance the uptake of arabinose. The yeast carries additional genomic mutations enabling it to consume L-arabinose, even as the only carbon source, and to produce ethanol. A yeast strain engineered to metabolize arabinose through a novel pathway is also disclosed. Methods of producing ethanol include utilizing these modified yeast strains.

  17. Fighting back against male-killers.

    PubMed

    Jaenike, John

    2007-04-01

    Male-killing endosymbionts create a genetic black hole into which host nuclear genes vanish. In a recent paper, Hornett et al. transferred male-killing Wolbachia between different strains of the butterfly Hypolimnas bolina through hybridization and backcrossing. Their results provide unambiguous evidence of genetic variation for resistance to male-killers. A possible consequence of such variation is that male-killing might appear and disappear quickly on an evolutionary timescale. PMID:17276538

  18. Analysis of the Saccharomyces cerevisiae pan-genome reveals a pool of copy number variants distributed in diverse yeast strains from differing industrial environments

    PubMed Central

    Dunn, Barbara; Richter, Chandra; Kvitek, Daniel J.; Pugh, Tom; Sherlock, Gavin

    2012-01-01

    Although the budding yeast Saccharomyces cerevisiae is arguably one of the most well-studied organisms on earth, the genome-wide variation within this species—i.e., its “pan-genome”—has been less explored. We created a multispecies microarray platform containing probes covering the genomes of several Saccharomyces species: S. cerevisiae, including regions not found in the standard laboratory S288c strain, as well as the mitochondrial and 2-μm circle genomes–plus S. paradoxus, S. mikatae, S. kudriavzevii, S. uvarum, S. kluyveri, and S. castellii. We performed array-Comparative Genomic Hybridization (aCGH) on 83 different S. cerevisiae strains collected across a wide range of habitats; of these, 69 were commercial wine strains, while the remaining 14 were from a diverse set of other industrial and natural environments. We observed interspecific hybridization events, introgression events, and pervasive copy number variation (CNV) in all but a few of the strains. These CNVs were distributed throughout the strains such that they did not produce any clear phylogeny, suggesting extensive mating in both industrial and wild strains. To validate our results and to determine whether apparently similar introgressions and CNVs were identical by descent or recurrent, we also performed whole-genome sequencing on nine of these strains. These data may help pinpoint genomic regions involved in adaptation to different industrial milieus, as well as shed light on the course of domestication of S. cerevisiae. PMID:22369888

  19. The new modern era of yeast genomics: community sequencing and the resulting annotation of multiple Saccharomyces cerevisiae strains at the Saccharomyces Genome Database

    PubMed Central

    Engel, Stacia R.; Cherry, J. Michael

    2013-01-01

    The first completed eukaryotic genome sequence was that of the yeast Saccharomyces cerevisiae, and the Saccharomyces Genome Database (SGD; http://www.yeastgenome.org/) is the original model organism database. SGD remains the authoritative community resource for the S. cerevisiae reference genome sequence and its annotation, and continues to provide comprehensive biological information correlated with S. cerevisiae genes and their products. A diverse set of yeast strains have been sequenced to explore commercial and laboratory applications, and a brief history of those strains is provided. The publication of these new genomes has motivated the creation of new tools, and SGD will annotate and provide comparative analyses of these sequences, correlating changes with variations in strain phenotypes and protein function. We are entering a new era at SGD, as we incorporate these new sequences and make them accessible to the scientific community, all in an effort to continue in our mission of educating researchers and facilitating discovery. Database URL: http://www.yeastgenome.org/ PMID:23487186

  20. Identification of yeasts isolated from raffia wine (Raphia hookeri) produced in Côte d'Ivoire and genotyping of Saccharomyces cerevisiae strains by PCR inter-delta.

    PubMed

    Tra Bi, Charles Y; N'guessan, Florent K; Kouakou, Clémentine A; Jacques, Noemie; Casaregola, Serge; Djè, Marcellin K

    2016-08-01

    Raffia wine is a traditional alcoholic beverage produced in several African countries where it plays a significant role in traditional customs and population diet. Alcoholic fermentation of this beverage is ensured by a complex natural yeast flora which plays a decisive role in the quality of the final product. This present study aims to evaluate the distribution and the diversity of the yeast strains isolated in raffia wine from four sampling areas (Abengourou, Alépé, Grand-Lahou and Adzopé) in Côte d'Ivoire. Based on the D1/D2 domain of the LSU rDNA sequence analysis, nine species belonging to six genera were distinguished. With a percentage of 69.5 % out of 171 yeast isolates, Saccharomyces cerevisiae was the predominant species in the raffia wine, followed by Kodamaea ohmeri (20.4 %). The other species isolated were Candida haemulonii (4.1 %), Candida phangngensis (1.8 %), Pichia kudriavzevii (1.2 %), Hanseniaspora jakobsenii (1.2 %), Candida silvae (0.6 %), Hanseniaspora guilliermondii (0.6 %) and Meyerozyma caribbica (0.6 %). The molecular characterization of S. cerevisiae isolates at the strain level using the PCR-interdelta method revealed the presence of 21 profiles (named I to XXI) within 115 isolates. Only four profiles (I, III, V and XI) were shared by the four areas under study. Phenotypic characterization of K. ohmeri strains showed two subgroups for sugar fermentation and no diversity for the nitrogen compound assimilations and the growth at different temperatures. PMID:27339306

  1. Direct Production of Ethanol from Raw Corn Starch via Fermentation by Use of a Novel Surface-Engineered Yeast Strain Codisplaying Glucoamylase and α-Amylase

    PubMed Central

    Shigechi, Hisayori; Koh, Jun; Fujita, Yasuya; Matsumoto, Takeshi; Bito, Yohei; Ueda, Mitsuyoshi; Satoh, Eiichi; Fukuda, Hideki; Kondo, Akihiko

    2004-01-01

    Direct and efficient production of ethanol by fermentation from raw corn starch was achieved by using the yeast Saccharomyces cerevisiae codisplaying Rhizopus oryzae glucoamylase and Streptococcus bovis α-amylase by using the C-terminal-half region of α-agglutinin and the flocculation functional domain of Flo1p as the respective anchor proteins. In 72-h fermentation, this strain produced 61.8 g of ethanol/liter, with 86.5% of theoretical yield from raw corn starch. PMID:15294847

  2. Direct production of ethanol from raw corn starch via fermentation by use of a novel surface-engineered yeast strain codisplaying glucoamylase and alpha-amylase.

    PubMed

    Shigechi, Hisayori; Koh, Jun; Fujita, Yasuya; Matsumoto, Takeshi; Bito, Yohei; Ueda, Mitsuyoshi; Satoh, Eiichi; Fukuda, Hideki; Kondo, Akihiko

    2004-08-01

    Direct and efficient production of ethanol by fermentation from raw corn starch was achieved by using the yeast Saccharomyces cerevisiae codisplaying Rhizopus oryzae glucoamylase and Streptococcus bovis alpha-amylase by using the C-terminal-half region of alpha-agglutinin and the flocculation functional domain of Flo1p as the respective anchor proteins. In 72-h fermentation, this strain produced 61.8 g of ethanol/liter, with 86.5% of theoretical yield from raw corn starch. PMID:15294847

  3. Clemency Pogue: Fairy Killer

    ERIC Educational Resources Information Center

    Petty, J. T.

    2004-01-01

    This young adult author claims his most enjoyable task as a writer is "intellectual danger, getting into other people's trouble." He asks his readers not to trust him, and then, as evidence, tempts us with a look at a chapter from "Clemency Pogue: Fairy Killer."

  4. Biology Myth-Killers

    ERIC Educational Resources Information Center

    Lampert, Evan

    2014-01-01

    "Biology Myth-Killers" is an activity designed to identify and correct common misconceptions for high school and college introductory biology courses. Students identify common myths, which double as biology misconceptions, and use appropriate sources to share the "truth" about the myths. This learner-centered activity is a fun…

  5. In vivo identification of essential nucleotides in tRNALeu to its functions by using a constructed yeast tRNALeu knockout strain

    PubMed Central

    Huang, Qian; Yao, Peng; Eriani, Gilbert; Wang, En-Duo

    2012-01-01

    The fidelity of protein biosynthesis requires the aminoacylation of tRNA with its cognate amino acid catalyzed by aminoacyl-tRNA synthetase with high levels of accuracy and efficiency. Crucial bases in tRNALeu to aminoacylation or editing functions of leucyl-tRNA synthetase have been extensively studied mainly by in vitro methods. In the present study, we constructed two Saccharomyces cerevisiae tRNALeu knockout strains carrying deletions of the genes for tRNALeu(GAG) and tRNALeu(UAG). Disrupting the single gene encoding tRNALeu(GAG) had no phenotypic consequence when compared to the wild-type strain. While disrupting the three genes for tRNALeu(UAG) had a lethal effect on the yeast strain, indicating that tRNALeu(UAG) decoding capacity could not be compensated by another tRNALeu isoacceptor. Using the triple tRNA knockout strain and a randomly mutated library of tRNALeu(UAG), a selection to identify critical tRNALeu elements was performed. In this way, mutations inducing in vivo decreases of tRNA levels or aminoacylation or editing ability by leucyl-tRNA synthetase were identified. Overall, the data showed that the triple tRNA knockout strain is a suitable tool for in vivo studies and identification of essential nucleotides of the tRNA. PMID:22917587

  6. Optimization of glutathione production in batch and fed-batch cultures by the wild-type and recombinant strains of the methylotrophic yeast Hansenula polymorpha DL-1

    PubMed Central

    2011-01-01

    Background Tripeptide glutathione (gamma-glutamyl-L-cysteinyl-glycine) is the most abundant non-protein thiol that protects cells from metabolic and oxidative stresses and is widely used as medicine, food additives and in cosmetic industry. The methylotrophic yeast Hansenula polymorpha is regarded as a rich source of glutathione due to the role of this thiol in detoxifications of key intermediates of methanol metabolism. Cellular and extracellular glutathione production of H. polymorpha DL-1 in the wild type and recombinant strains which overexpress genes of glutathione biosynthesis (GSH2) and its precursor cysteine (MET4) was studied. Results Glutathione producing capacity of H. polymorpha DL-1 depending on parameters of cultivation (dissolved oxygen tension, pH, stirrer speed), carbon substrate (glucose, methanol) and type of overexpressed genes of glutathione and its precursor biosynthesis during batch and fed-batch fermentations were studied. Under optimized conditions of glucose fed-batch cultivation, the glutathione productivity of the engineered strains was increased from ~900 up to ~ 2300 mg of Total Intracellular Glutathione (TIG) or GSH+GSSGin, per liter of culture medium. Meantime, methanol fed-batch cultivation of one of the recombinant strains allowed achieving the extracellular glutathione productivity up to 250 mg of Total Extracellular Glutathione (TEG) or GSH+GSSGex, per liter of the culture medium. Conclusions H. polymorpha is an competitive glutathione producer as compared to other known yeast and bacteria strains (Saccharomyces cerevisiae, Candida utilis, Escherichia coli, Lactococcus lactis etc.) with good perspectives for further improvement especially for production of extracellular form of glutathione. PMID:21255454

  7. Citric acid production from extract of Jerusalem artichoke tubers by the genetically engineered yeast Yarrowia lipolytica strain 30 and purification of citric acid.

    PubMed

    Wang, Ling-Fei; Wang, Zhi-Peng; Liu, Xiao-Yan; Chi, Zhen-Ming

    2013-11-01

    In this study, citric acid production from extract of Jerusalem artichoke tubers by the genetically engineered yeast Yarrowia lipolytica strain 30 was investigated. After the compositions of the extract of Jerusalem artichoke tubers for citric acid production were optimized, the results showed that natural components of extract of Jerusalem artichoke tubers without addition of any other components were suitable for citric acid production by the yeast strain. During 10 L fermentation using the extract containing 84.3 g L(-1) total sugars, 68.3 g L(-1) citric acid was produced and the yield of citric acid was 0.91 g g(-1) within 336 h. At the end of the fermentation, 9.2 g L(-1) of residual total sugar and 2.1 g L(-1) of reducing sugar were left in the fermented medium. At the same time, citric acid in the supernatant of the culture was purified. It was found that 67.2 % of the citric acid in the supernatant of the culture was recovered and purity of citric acid in the crystal was 96 %. PMID:23584740

  8. Liquid formulations sustaining the viability of a superior yeast strain Pichia anomala WRL-076 for mycotoxin control

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pichia anomala WRL-076 was discovered by a visual screening bioassay for its antagonism against A. flavus. The yeast could effectively inhibit aflatoxin production and growth of A. flavus. An important requirement for the use of biocontrol agents is the production of large quantities of the micro...

  9. Strain typing of Zygosaccharomyces yeast species using a single molecular method based on polymorphism of the intergenic spacer region (IGS).

    PubMed

    Wrent, Petra; Rivas, Eva-María; Peinado, José M; de Silóniz, María-Isabel

    2010-08-15

    Unlike previously reported methods that need a combination of several typing techniques, we have developed a single method for strain typing of the Zygosaccharomyces bailii, Z. mellis and Z. rouxii spoilage species. Strains belonging to other species have also been included for comparison. We have demonstrated that the IGS-PCR RFLP method has a high discriminative power. Considering the three endonucleases used in this work, we have obtained a variability of 100% for Z. mellis and Z. rouxii strains and up to 70% for Z. bailii. We have also detected two misidentified Z. mellis strains (CBS 711 and CBS 7412) which have RFLP patterns with a set of bands characteristic of Z. rouxii strains. Sequencing of 26S rDNA D1/D2 domains and the 5.8-ITS rDNA region confirmed these strains as Z. rouxii. The method also groups three certified hybrid strains of Zygosaccharomyces in a separate cluster. PMID:20619910

  10. The growth, properties and interactions of yeasts and bacteria associated with the maturation of Camembert and blue-veined cheeses.

    PubMed

    Addis, E; Fleet, G H; Cox, J M; Kolak, D; Leung, T

    2001-09-19

    The growth of yeasts and bacteria were monitored during the maturation of Camembert and blue-veined cheese produced in Australia. Yeasts were prominent throughout maturation, growing to 10(5)-10(9)/g, depending on the manufacturer. Debaryomyces hansenii predominated, but there were lesser, inconsistent contributions from Yarrowia lipolytica. Of the non-lactic acid bacteria, Acinetobacter species were significant during the maturation of Camembert but not blue-veined cheeses, and grew to 10(6)-10(8) cfu/g. Staphylococcus and Micrococcus species were consistently isolated from the cheeses with Staphylococcus xylosus growing to 10(5)-10(9) cfu/g, depending on the product. Lactic acid bacteria (10(7)-10(9) cfu/g) were present throughout maturation but were not identified. Interactions between the various yeasts and bacterial isolates were examined. Several strains of D. hansenii exhibited killer activity but not against Y. lipolytica. None of the yeasts were antagonistic towards the bacteria but some strains of D. hansenii enhanced the growth of Y. lipolytica and S. xylosus. The yeast and bacterial isolates exhibited various degrees of extracellular proteolytic and lipolytic activities. PMID:11589557

  11. Osmoresistant yeast Zygosaccharomyces rouxii: the two most studied wild-type strains (ATCC 2623 and ATCC 42981) differ in osmotolerance and glycerol metabolism.

    PubMed

    Pribylova, Lenka; de Montigny, Jacky; Sychrova, Hana

    2007-03-01

    The yeast Zygosaccharomyces rouxii is known for its high tolerance to osmotic stress, which is thought to be caused by sets of specific genes. Relatively few Z. rouxii genes have been identified so far, all of them having homologues in Saccharomyces cerevisiae; none of them was Z. rouxii-specific. Most of the known Z. rouxii genes were isolated from two wild-type strains, ATCC 2623 and ATCC 42981. In this study, we compared these two strains with regard to some of their morphological, physiological and genomic properties. Important differences were found in their salt tolerance and assimilation of glycerol and karyotype; slight differences were also present in their cell morphology. The ATCC 42981 strain showed a higher resistance to salts, higher glycerol production and, unlike ATCC 2623, was able to assimilate glycerol. Under conditions of osmotic stress, the glycerol production in both Z. rouxii strains was much lower than in a S. cerevisiae S288c culture, which suggested the presence of a system that efficiently retains glycerol inside Z. rouxii cells. The karyotype analysis revealed that ATCC 42981 cells contain more chromosomes and have a bigger genome size than those of ATCC 2623. PMID:17351908

  12. Microbiological and Physicochemical Characterization of Small-Scale Cocoa Fermentations and Screening of Yeast and Bacterial Strains To Develop a Defined Starter Culture

    PubMed Central

    Pereira, Gilberto Vinícius de Melo; Miguel, Maria Gabriela da Cruz Pedrozo; Ramos, Cíntia Lacerda

    2012-01-01

    Spontaneous cocoa bean fermentations performed under bench- and pilot-scale conditions were studied using an integrated microbiological approach with culture-dependent and culture-independent techniques, as well as analyses of target metabolites from both cocoa pulp and cotyledons. Both fermentation ecosystems reached equilibrium through a two-phase process, starting with the simultaneous growth of the yeasts (with Saccharomyces cerevisiae as the dominant species) and lactic acid bacteria (LAB) (Lactobacillus fermentum and Lactobacillus plantarum were the dominant species), which were gradually replaced by the acetic acid bacteria (AAB) (Acetobacter tropicalis was the dominant species). In both processes, a sequence of substrate consumption (sucrose, glucose, fructose, and citric acid) and metabolite production kinetics (ethanol, lactic acid, and acetic acid) similar to that of previous, larger-scale fermentation experiments was observed. The technological potential of yeast, LAB, and AAB isolates was evaluated using a polyphasic study that included the measurement of stress-tolerant growth and fermentation kinetic parameters in cocoa pulp media. Overall, strains L. fermentum UFLA CHBE8.12 (citric acid fermenting, lactic acid producing, and tolerant to heat, acid, lactic acid, and ethanol), S. cerevisiae UFLA CHYC7.04 (ethanol producing and tolerant to acid, heat, and ethanol), and Acetobacter tropicalis UFLA CHBE16.01 (ethanol and lactic acid oxidizing, acetic acid producing, and tolerant to acid, heat, acetic acid, and ethanol) were selected to form a cocktail starter culture that should lead to better-controlled and more-reliable cocoa bean fermentation processes. PMID:22636007

  13. Epitope-tagged yeast strains reveal promoter driven changes to 3'-end formation and convergent antisense-transcription from common 3' UTRs.

    PubMed

    Swaminathan, Angavai; Beilharz, Traude H

    2016-01-01

    Epitope-tagging by homologous recombination is ubiquitously used to study gene expression, protein localization and function in yeast. This is generally thought to insulate the regulation of gene expression to that mediated by the promoter and coding regions because native 3' UTR are replaced. Here we show that the 3' UTRs, CYC1 and ADH1, contain cryptic promoters that generate abundant convergent antisense-transcription in Saccharomyces cerevisiae. Moreover we show that aberrant, truncating 3' -end formation is often associated with regulated transcription in TAP-tagged strains. Importantly, the steady-state level of both 3' -truncated and antisense transcription products is locus dependent. Using TAP and GFP-tagged strains we show that the transcriptional state of the gene-of-interest induces changes to 3' -end formation by alternative polyadenylation and antisense transcription from a universal 3' UTR. This means that these 3' UTRs contains plastic features that can be molded to reflect the regulatory architecture of the locus rather than bringing their own regulatory paradigm to the gene-fusions as would be expected. Our work holds a cautionary note for studies utilizing tagged strains for quantitative biology, but also provides a new model for the study of promoter driven rewiring of 3' -end formation and regulatory non-coding transcription. PMID:26481348

  14. Suppressing the killer instinct.

    PubMed

    Campbell, Kerry S

    2016-01-01

    Natural killer (NK) cells are innate lymphoid cells that have adopted activating and inhibitory signaling mechanisms enabling them to be tolerant of normal cells but to distinguish and eliminate tumor cells and virus-infected cells. In this issue of Science Signaling, Matalon et al show how inhibitory receptors disrupt NK cell activation by stimulating dephosphorylation of the adaptor protein LAT (linker of activated T cells) and phospholipase C-γ by the phosphatase SHP-1 [Src homology 2 (SH2) domain-containing protein tyrosine phosphatase 1], as well as ubiquitylation of LAT by Cbl family E3 ubiquitin ligases. PMID:27221707

  15. Intraspecific diversity of Aureobasidium pullulans strains from different marine environments

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Liu, Zhiqiang; Chi, Zhenming; Zhang, Liang; Zhang, Dechao

    2009-09-01

    Totally more than 500 yeast strains were isolated from seawater, sea sediments, mud of sea salterns, marine fish guts and marine algae. The results of routine and molecular biology identification methods show that nine strains among these marine yeasts belong to Aureobasidium pullulans, although the morphologies of their colonies are very different. The marine yeasts isolated from different marine environments indicate that A. pullulans is widely distributed in different environmental conditions. These Aureobasidium pullulans strains include A. pullulans 4#2, A. pullulans N13d, A. pullulans HN3-11, A. pullulans HN2-3, A. pullulans JHSc, A. pullulans HN4.7, A. pullulans HN5.3, A. pullulans HN6.2 and A. pullulans W13a. A. pullulans 4#2 could produce cellulase and single cell protein. A. pullulans N13d could produce protease, lipase, amylase and cellulase. Both A. pullulans HN3-11 and A. pullulans HN2-3 were able to produce protease, lipase and cellulase. A. pullulans JHSc could secrete cellulase and killer toxin. Both A. pullulans HN4.7 and A. pullulans HN5.3 could yield lipase and cellulase. A. pullulans W13a was able to secrete extracellular amylase and cellulase while A. pullulans HN4.7 and A. pullulans N13d could produce siderophores. This means that different A. pullulans strains from different marine environments have different physiological characteristics, which may be applied in many different biotechnological industries.

  16. Fully Automated Molecular Biology Routines on a Plasmid-Based Functional Proteomic Workcell: Evaluation and Characterization of Yeast Strains Optimized for Growth on Xylose and Engineered to Express an Insecticidal Peptide

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optimization of genes important to production of fuel ethanol from hemicellulosic biomass for use in engineering improved commercial yeast strains is necessary to meet the United States' rapidly expanding need for ethanol. United States Department of Agriculture, Agricultural Research Service, Nati...

  17. Production of formaldehyde by detergent-treated cells of a methanol yeast, Candida boidinii S2 mutant strain AOU-1

    SciTech Connect

    Sakai, Y.; Tani, Y.

    1988-02-01

    Treatment of cells of a methanol yeast, Candida boidinii, with the cationic detergent cetyldimethylbenzyl-ammonium chloride (cation M2) improved the production of formaldehyde. Formaldehyde production was improved twofold with respect to the initial amount of formaldehyde and 1.61-fold with respect to the final amount of formaldehyde after a 12-h reaction under optimized detergent treatment conditions. The treatment caused formaldehyde and formate dehydrogenases to leak out of the cells more rapidly than catalase, but there was no leakage of alcohol oxidase. The improvement in formaldehyde production was considered to be due to the increased permeability of yeast cell membranes and to lower activities of formaldehyde and formate dehydrogenases in Cation M2-treated cells than in intact cells. Changes in the ultrastructure of the cells were observed upon Cation M2 treatment. Several developed peroxisomes were observed in intact cells. After Cation M2 treatment, the cells were obviously damaged, and several peroxisomes seemed to have fused with each other.

  18. Arsenic: The Silent Killer

    SciTech Connect

    Foster, Andrea

    2006-02-28

    Andrea Foster uses x-rays to determine the forms of potentially toxic elements in environmentally-important matrices such as water, sediments, plants, and microorganisms. In this free public lecture, Foster will discuss her research on arsenic, which is called the silent killer because dissolved in water, it is colorless, odorless, and tasteless, yet consumption of relatively small doses of this element in its most toxic forms can cause rapid and violent death. Arsenic is a well-known poison, and has been used as such since ancient times. Less well known is the fact that much lower doses of the element, consumed over years, can lead to a variety of skin and internal cancers that can also be fatal. Currently, what has been called the largest mass poisoning in history is occurring in Bangladesh, where most people are by necessity drinking ground water that is contaminated with arsenic far in excess of the maximum amounts determined to be safe by the World Health Organization. This presentation will review the long and complicated history with arsenic, describe how x-rays have helped explain the high yet spatially variable arsenic concentrations in Bangladesh, discuss the ways in which land use in Bangladesh may be exacerbating the problem, and summarize the impact of this silent killer on drinking water systems worldwide.

  19. [Study of animal viruses in yeast].

    PubMed

    Morikawa, Yuko

    2006-06-01

    Yeast is often considered to be a model eukaryotic organism, in a manner analogous to E. coli as a model prokaryotic organism. Yeast has been extensively characterized and the genomes completely sequenced. Despite the small genome size, yeast displays most of features of higher eukaryotes. The facts that most of cellular machinery is conserved among different eukaryotes and that the powerful technologies of genetics and molecular biology are available have made yeast model eukaryotic cells in biological and biomedical sciences including virology. Cumulative data indicate that yeast can be a host for animal viruses. I briefly describe yeast gene expression and review viral replication in yeast. Great discovery include complete replication of animal viruses and production of virus-like particle vaccines in yeast. Current studies on yeast focus on identification of host factors and machinery used for viral replication. The studies are based on traditional yeast genetics and genome-wide identification using a complete set of yeast deletion strains. PMID:17038807

  20. Natural killer cell deficiency

    PubMed Central

    Orange, Jordan S.

    2013-01-01

    Natural killer (NK) cells are part of the innate immune defense against infection and cancer, and are especially useful in combating certain viral pathogens. The utility of NK cells in human health has been underscored by a growing number of individuals who are deficient in NK cells and/or their functions. This can be in the context of a broader genetically-defined congenital immunodeficiency of which there are over forty presently known to impair NK cells. The abnormality of NK cells, however, in certain cases represents the majority immunological defect. In aggregate, these conditions are termed NK cell deficiency. Recent advances have added clarity to this diagnosis and identified defects in three different genes that can cause NK cell deficiency as well as some of the underlying biology. Appropriate consideration of these diagnoses and patients raises the potential for rational therapeutic options and further innovation. PMID:23993353

  1. Yeasts in spa establishments.

    PubMed

    Svorcová, L

    1982-05-01

    It was investigated occurrence of yeasts on bathsurfaces, in sauna rooms, in swimming and therapeutic pool water. The number of yeasts decreased depending on patients age, if the rooms were furnished with bath. The lowest contamination was found after bath of 40-60 years-old women. In the saunas were yeasts not found on the upper benches with temperature above 55 degrees C. Much higher counts on lower benches and wood mats with temperature 35-40 degrees C, on basin walls and bottom-up to 10(4)-10(6)/100 cm2. It was isolated 172 yeast strains. The occurrence of some selected strains is given in Table 7, with the toxic effect of disinfectants. The most strains were resistant to Peracetic acid and Chloramin B. Since most of the isolated and determinated strains were found in contaminated environment or during various diseases, the yeasts of the genus Cryptococcus, Candida, Rhodotorula, Torulopsis and Metschnikowia should not occur in bath establishment, and should be classified among indicators of contamination of environment including water. PMID:7124167

  2. Enhanced biodegradation of lindane using oil-in-water bio-microemulsion stabilized by biosurfactant produced by a new yeast strain, Pseudozyma VITJzN01.

    PubMed

    Abdul Salam, Jaseetha; Das, Nilanjana

    2013-11-28

    Organochlorine pesticide residues continue to remain as a major environmental threat worldwide. Lindane is an organochlorine pesticide widely used as an acaricide in medicine and agriculture. In the present study, a new lindane-degrading yeast strain, Pseudozyma VITJzN01, was identified as a copious producer of glycolipid biosurfactant. The glycolipid structure and type were elucidated by FTIR, NMR spectroscopy, and GC-MS analysis. The surface activity and stability of the glycolipid was analyzed. The glycolipids, characterized as mannosylerythritol lipids (MELs), exhibited excellent surface active properties and the surface tension of water was reduced to 29 mN/m. The glycolipid was stable over a wide range of pH, temperature, and salinity, showing a very low CMC of 25 mg/l. Bio-microemulsion of olive oil-in-water (O/W) was prepared using the purified biosurfactant without addition of any synthetic cosurfactants, for lindane solubilization and enhanced degradation assay in liquid and soil slurry. The O/W bio-microemulsions enhanced the solubility of lindane up to 40-folds. Degradation of lindane (700 mg/l) by VITJzN01 in liquid medium amended with bio-microemulsions was found to be enhanced by 36% in 2 days, compared with degradation in 12 days in the absence of bio-microemulsions. Lindane-spiked soil slurry incubated with bio-microemulsions also showed 20-40% enhanced degradation compared with the treatment with glycolipids or yeast alone. This is the first report on lindane degradation by Pseudozyma sp., and application of bio-microemulsions for enhanced lindane degradation. MEL-stabilized bio-microemulsions can serve as a potential tool for enhanced remediation of diverse lindanecontaminated environments. PMID:23928846

  3. Immunobiology of natural killer cells

    SciTech Connect

    Lotzova, E.; Herberman, R.B.

    1986-01-01

    This book combines research from many disciplines into a review of natural killer (NK) cell-mediated immunity in humans and experimental animal system. Topics for the volumes include: Volume I: Assays for NK Cell Cytotoxicity; Their Values and Pitfalls. Separation and Characterization of Phenotypically Distinct Subsets of NK Cells. Ultrastructure and Cytochemistry of the Human Large Granular Lymphocytes. Phylogeny and Ontogeny of NK Cells. Tissue and Organ distribution of NK Cells. Genetic Control of NK Cell Activity in Rodents. Phenotype, Functional Heterogeneity, and Lineage of Natural Killer Cells. Target Cell Structures, Recognition Sites, and the Mechanism of NK Cytotoxicity. Natural Killer Cytotoxic Factors (NKCF) Role in Cell-Mediated Cytotoxicity. Characteristics of Cultured NK Cells. Lectin-Dependent Killer Cells. MLC-Induced Cytotoxicity as a Model for the Development and Regulation of NK Cytotoxicity. LGL Lymphoproliferative Diseases in Man and Experimental Animals: The Characteristics of These Cells and Their Potential Experimental Uses. Index.

  4. Establishment of a yeast platform strain for production of p-coumaric acid through metabolic engineering of aromatic amino acid biosynthesis.

    PubMed

    Rodriguez, Angelica; Kildegaard, Kanchana R; Li, Mingji; Borodina, Irina; Nielsen, Jens

    2015-09-01

    Aromatic amino acids are precursors of numerous plant secondary metabolites with diverse biological functions. Many of these secondary metabolites are already being used as active pharmaceutical or nutraceutical ingredients, and there are numerous exploratory studies of other compounds with promising applications. p-Coumaric acid is derived from aromatic amino acids and, besides being a valuable chemical building block, it serves as precursor for biosynthesis of many secondary metabolites, such as polyphenols, flavonoids, and some polyketides. Here we developed a p-coumaric acid-overproducing Saccharomyces cerevisiae platform strain. First, we reduced by-product formation by knocking out phenylpyruvate decarboxylase ARO10 and pyruvate decarboxylase PDC5. Second, different versions of feedback-resistant DAHP synthase and chorismate mutase were overexpressed. Finally, we identified shikimate kinase as another important flux-controlling step in the aromatic amino acid pathway by overexpressing enzymes from Escherichia coli, homologous to the pentafunctional enzyme Aro1p and to the bifunctional chorismate synthase-flavin reductase Aro2p. The highest titer of p-coumaric acid of 1.93 ± 0.26 g L(-1) was obtained, when overexpressing tyrosine ammonia-lyase TAL from Flavobacterium johnsoniaeu, DAHP synthase ARO4(K229L), chorismate mutase ARO7(G141S) and E. coli shikimate kinase II (aroL) in Δpdc5Δaro10 strain background. To our knowledge this is the highest reported titer of an aromatic compound produced by yeast. The developed S. cerevisiae strain represents an attractive platform host for production of p-coumaric-acid derived secondary metabolites, such as flavonoids, polyphenols, and polyketides. PMID:26292030

  5. Control of enzymatic degradation of biodegradable polymers by treatment with biosurfactants, mannosylerythritol lipids, derived from Pseudozyma spp. yeast strains.

    PubMed

    Fukuoka, Tokuma; Shinozaki, Yukiko; Tsuchiya, Wataru; Suzuki, Ken; Watanabe, Takashi; Yamazaki, Toshimasa; Kitamoto, Dai; Kitamoto, Hiroko

    2016-02-01

    Cutinase-like esterase from the yeasts Pseudozyma antarctica (PaE) shows strong degradation activity in an agricultural biodegradable plastic (BP) model of mulch films composed of poly(butylene succinate-co-adipate) (PBSA). P. antarctica is known to abundantly produce a glycolipid biosurfactant, mannosylerythritol lipid (MEL). Here, the effects of MEL on PaE-catalyzed degradation of BPs were investigated. Based on PBSA dispersion solution, the degradation of PBSA particles by PaE was inhibited in the presence of MEL. MEL behavior on BP substrates was monitored by surface plasmon resonance (SPR) using a sensor chip coated with polymer films. The positive SPR signal shift indicated that MEL readily adsorbed and spread onto the surface of a BP film. The amount of BP degradation by PaE was monitored based on the negative SPR signal shift and was decreased 1.7-fold by MEL pretreatment. Furthermore, the shape of PBSA mulch films in PaE-containing solution was maintained with MEL pretreatment, whereas untreated films were almost completely degraded and dissolved. These results suggest that MEL covering the surface of BP film inhibits adsorption of PaE and PaE-catalyzed degradation of BPs. We applied the above results to control the microbial degradation of BP mulch films. MEL pretreatment significantly inhibited BP mulch film degradation by both PaE solution and BP-degradable microorganism. Moreover, the degradation of these films was recovered after removal of the coated MEL by ethanol treatment. These results demonstrate that the biodegradation of BP films can be readily and reversibly controlled by a physical approach using MEL. PMID:26512003

  6. Evaluation of Estrogenic Potential of Flavonoids Using a Recombinant Yeast Strain and MCF7/BUS Cell Proliferation Assay

    PubMed Central

    Resende, Flávia A.; de Oliveira, Ana Paula S.; de Camargo, Mariana S.; Vilegas, Wagner; Varanda, Eliana A.

    2013-01-01

    Phytoestrogens are of interest because of their reported beneficial effects on many human maladies including cancer, neurodegeneration, cardiovascular disease and diabetes. Furthermore, there is a search for compounds with estrogenic activity that can replace estrogen in hormone replacement therapy during menopause, without the undesirable effects of estrogen, such as the elevation of breast cancer occurrence. Thus, the principal objective of this study was to assess the estrogenic activity of flavonoids with different hydroxylation patterns: quercetin, kaempferol, luteolin, fisetin, chrysin, galangin, flavone, 3-hydroxyflavone, 5-hydroxyflavone and 7-hydroxyflavone via two different in vitro assays, the recombinant yeast assay (RYA) and the MCF-7 proliferation assay (E-screen), since the most potent phytoestrogens are members of the flavonoid family. In these assays, kaempferol was the only compound that showed ERα-dependent transcriptional activation activity by RYA, showing 6.74±1.7 nM EEQ, besides acting as a full agonist for the stimulation of proliferation of MCF-7/BUS cells. The other compounds did not show detectable levels of interaction with ER under the conditions used in the RYA. However, in the E-screen assay, compounds such as galangin, luteolin and fisetin also stimulated the proliferation of MCF-7/BUS cells, acting as partial agonists. In the evaluation of antiestrogenicity, the compounds quercetin, chrysin and 3-hydroxyflavone significantly inhibited the cell proliferation induced by 17-β-estradiol in the E-screen assay, indicating that these compounds may act as estrogen receptor antagonists. Overall, it became clear in the assay results that the estrogenic activity of flavonoids was affected by small structural differences such as the number of hydroxyl groups, especially those on the B ring of the flavonoid. PMID:24098354

  7. Prevention of Yeast Spoilage in Feed and Food by the Yeast Mycocin HMK

    PubMed Central

    Lowes, K. F.; Shearman, C. A.; Payne, J.; MacKenzie, D.; Archer, D. B.; Merry, R. J.; Gasson, M. J.

    2000-01-01

    The yeast Williopsis mrakii produces a mycocin or yeast killer toxin designated HMK; this toxin exhibits high thermal stability, high pH stability, and a broad spectrum of activity against other yeasts. We describe construction of a synthetic gene for mycocin HMK and heterologous expression of this toxin in Aspergillus niger. Mycocin HMK was fused to a glucoamylase protein carrier, which resulted in secretion of biologically active mycocin into the culture media. A partial purification protocol was developed, and a comparison with native W. mrakii mycocin showed that the heterologously expressed mycocin had similar physiological properties and an almost identical spectrum of biological activity against a number of yeasts isolated from silage and yoghurt. Two food and feed production systems prone to yeast spoilage were used as models to assess the ability of mycocin HMK to act as a biocontrol agent. The onset of aerobic spoilage in mature maize silage was delayed by application of A. niger mycocin HMK on opening because the toxin inhibited growth of the indigenous spoilage yeasts. This helped maintain both higher lactic acid levels and a lower pH. In yoghurt spiked with dairy spoilage yeasts, A. niger mycocin HMK was active at all of the storage temperatures tested at which yeast growth occurred, and there was no resurgence of resistant yeasts. The higher the yeast growth rate, the more effective the killing action of the mycocin. Thus, mycocin HMK has potential applications in controlling both silage spoilage and yoghurt spoilage caused by yeasts. PMID:10698773

  8. Growth and manipulation of yeast.

    PubMed

    Treco, D A; Reynolds, A; Lundblad, V

    2001-05-01

    This unit describes preparation of selected media for growing yeast and also discusses strain storage and revival. Protocols are provided for the assay of beta-galactosidase in liquid culture and for transformation using lithium acetate. PMID:18429086

  9. 21 CFR 73.355 - Phaffia yeast.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 1 2011-04-01 2011-04-01 false Phaffia yeast. 73.355 Section 73.355 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Foods § 73.355 Phaffia yeast. (a) Identity. (1) The color additive phaffia yeast consists of the killed, dried cells of a nonpathogenic and nontoxicogenic strain of...

  10. 21 CFR 73.355 - Phaffia yeast.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 1 2014-04-01 2014-04-01 false Phaffia yeast. 73.355 Section 73.355 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Foods § 73.355 Phaffia yeast. (a) Identity. (1) The color additive phaffia yeast consists of the killed, dried cells of a nonpathogenic and nontoxicogenic strain of...