An original method for producing acetaldehyde and diacetyl by yeast fermentation.

PubMed

Rosca, Irina; Petrovici, Anca Roxana; Brebu, Mihai; Stoica, Irina; Minea, Bogdan; Marangoci, Narcisa

In this study a natural culture medium that mimics the synthetic yeast peptone glucose medium used for yeast fermentations was designed to screen and select yeasts capable of producing high levels of diacetyl and acetaldehyde. The presence of whey powder and sodium citrate in the medium along with manganese and magnesium sulfate enhanced both biomass and aroma development. A total of 52 yeasts strains were cultivated in two different culture media, namely, yeast peptone glucose medium and yeast acetaldehyde-diacetyl medium. The initial screening of the strains was based on the qualitative reaction of the acetaldehyde with Schiff's reagent (violet color) and diacetyl with Brady's reagent (yellow precipitate). The fermented culture media of 10 yeast strains were subsequently analyzed by gas chromatography to quantify the concentration of acetaldehyde and diacetyl synthesized. Total titratable acidity values indicated that a total titratable acidity of 5.5°SH, implying culture medium at basic pH, was more favorable for the acetaldehyde biosynthesis using strain D15 (Candida lipolytica; 96.05mgL -1 acetaldehyde) while a total titratable acidity value of 7°SH facilitated diacetyl flavor synthesis by strain D38 (Candida globosa; 3.58mgL -1 diacetyl). Importantly, the results presented here suggest that this can be potentially used in the baking industry. Copyright © 2016 Sociedade Brasileira de Microbiologia. Published by Elsevier Editora Ltda. All rights reserved.

Genetic Analysis of Haploids from Industrial Strains of Baker's Yeast

PubMed Central

Oda, Yuji; Ouchi, Kozo

1989-01-01

Strains of baker's yeast conventionally used by the baking industry in Japan were tested for the ability to sporulate and produce viable haploid spores. Three isolates which possessed the properties of baker's yeasts were obtained from single spores. Each strain was a haploid, and one of these strains, YOY34, was characterized. YOY34 fermented maltose and sucrose, but did not utilize galactose, unlike its parental strain. Genetic analysis showed that YOY34 carried two MAL genes, one functional and one cryptic; two SUC genes; and one defective gal gene. The genotype of YOY34 was identified as MATα MAL1 MAL3g SUC2 SUC4 gall. The MAL1 gene from this haploid was constitutively expressed, was dominant over other wild-type MAL tester genes, and gave a weak sucrose fermentation. YOY34 was suitable for both bakery products, like conventional baker's yeasts, and for genetic analysis, like laboratory strains. PMID:16347967

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

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.

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.

Isolation and characterization of ethanol tolerant yeast strains

PubMed Central

Tikka, Chiranjeevi; Osuru, Hari Prasad; Atluri, Navya; Raghavulu, Praveen Chakravarthi Veera; yellapu, Nanda Kumar; Mannur, Ismail Shaik; Prasad, Uppu Venkateswara; Aluru, Sudheer; K, Narasimha Varma; Bhaskar, Matcha

2013-01-01

Yeast strains are commonly associated with sugar rich environments. Various fruit samples were selected as source for isolating yeast cells. The isolated cultures were identified at Genus level by colony morphology, biochemical characteristics and cell morphological characters. An attempt has been made to check the viability of yeast cells under different concentrations of ethanol. Ethanol tolerance of each strain was studied by allowing the yeast to grow in liquid YEPD (Yeast Extract Peptone Dextrose) medium having different concentrations of ethanol. A total of fifteen yeast strains isolated from different samples were used for the study. Seven strains of Saccharomyces cerevisiae obtained from different fruit sources were screened for ethanol tolerance. The results obtained in this study show a range of tolerance levels between 7%-12% in all the stains. Further, the cluster analysis based on 22 RAPD (Random Amplified polymorphic DNA) bands revealed polymorphisms in these seven Saccharomyces strains. PMID:23750092

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.

A new methodology to obtain wine yeast strains overproducing mannoproteins.

PubMed

Quirós, Manuel; Gonzalez-Ramos, Daniel; Tabera, Laura; Gonzalez, Ramon

2010-04-30

Yeast mannoproteins are highly glycosylated proteins that are covalently bound to the beta-1,3-glucan present in the yeast cell wall. Among their outstanding enological properties, yeast mannoproteins contribute to several aspects of wine quality by protecting against protein haze, reducing astringency, retaining aroma compounds and stimulating growth of lactic-acid bacteria. The development of a non-recombinant method to obtain enological yeast strains overproducing mannoproteins would therefore be very useful. Our previous experience on the genetic determinants of the release of these molecules by Saccharomyces cerevisiae has allowed us to propose a new methodology to isolate and characterize wine yeast that overproduce mannoproteins. The described methodology is based on the resistance of the killer 9 toxin produced by Williopsis saturnus, a feature linked to an altered biogenesis of the yeast cell wall. Copyright 2010 Elsevier B.V. All rights reserved.

Novel wine yeast with mutations in YAP1 that produce less acetic acid during fermentation.

PubMed

Cordente, Antonio G; Cordero-Bueso, Gustavo; Pretorius, Isak S; Curtin, Christopher D

2013-02-01

Acetic acid, a byproduct formed during yeast alcoholic fermentation, is the main component of volatile acidity (VA). When present in high concentrations in wine, acetic acid imparts an undesirable 'vinegary' character that results in a significant reduction in quality and sales. Previously, it has been shown that saké yeast strains resistant to the antifungal cerulenin produce significantly lower levels of VA. In this study, we used a classical mutagenesis method to isolate a series of cerulenin-resistant strains, derived from a commercial diploid wine yeast. Four of the selected strains showed a consistent low-VA production phenotype after small-scale fermentation of different white and red grape musts. Specific mutations in YAP1, a gene encoding a transcription factor required for oxidative stress tolerance, were found in three of the four low-VA strains. When integrated into the genome of a haploid wine strain, the mutated YAP1 alleles partially reproduced the low-VA production phenotype of the diploid cerulenin-resistant strains, suggesting that YAP1 might play a role in (regulating) acetic acid production during fermentation. This study offers prospects for the development of low-VA wine yeast starter strains that could assist winemakers in their effort to consistently produce wine to definable quality specifications. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

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

Indole-3-Acetic Acid-Producing Yeasts in the Phyllosphere of the Carnivorous Plant Drosera indica L

PubMed Central

Shin, Li-Ying; Wei, Jyuan-Yu; Fu, Shih-Feng; Chou, Jui-Yu

2014-01-01

Yeasts are widely distributed in nature and exist in association with other microorganisms as normal inhabitants of soil, vegetation, and aqueous environments. In this study, 12 yeast strains were enriched and isolated from leaf samples of the carnivorous plant Drosera indica L., which is currently threatened because of restricted habitats and use in herbal industries. According to similarities in large subunit and small subunit ribosomal RNA gene sequences, we identified 2 yeast species in 2 genera of the phylum Ascomycota, and 5 yeast species in 5 genera of the phylum Basidiomycota. All of the isolated yeasts produced indole-3-acetic acid (IAA) when cultivated in YPD broth supplemented with 0.1% L-tryptophan. Growth conditions, such as the pH and temperature of the medium, influenced yeast IAA production. Our results also suggested the existence of a tryptophan-independent IAA biosynthetic pathway. We evaluated the effects of various concentrations of exogenous IAA on yeast growth and observed that IAA produced by wild yeasts modifies auxin-inducible gene expression in Arabidopsis. Our data suggest that yeasts can promote plant growth and support ongoing prospecting of yeast strains for inclusion into biofertilizer for sustainable agriculture. PMID:25464336

Engineered CRISPR/Cas9 system for multiplex genome engineering of polyploid industrial yeast strains

DOE PAGES

Lian, Jiazhang; Bao, Zehua; Hu, Sumeng; ...

2018-02-20

The CRISPR/Cas9 system has been widely used for multiplex genome engineering of Saccharomyces cerevisiae. Furthermore, its application in manipulating industrial yeast strains is less successful, probably due to the genome complexity and low copy numbers of gRNA expression plasmids. Here we developed an efficient CRISPR/Cas9 system for industrial yeast strain engineering by using our previously engineered plasmids with increased copy numbers. Four genes in both a diploid strain (Ethanol Red, 8 alleles in total) and a triploid strain (ATCC 4124, 12 alleles in total) were knocked out in a single step with 100% efficiency. This system was used to constructmore » xylose-fermenting, lactate-producing industrial yeast strains, in which ALD6, PHO13, LEU2, and URA3 were disrupted in a single step followed by the introduction of a xylose utilization pathway and a lactate biosynthetic pathway on auxotrophic marker plasmids. The optimized CRISPR/Cas9 system provides a powerful tool for the development of industrial yeast based microbial cell factories.« less

Engineered CRISPR/Cas9 system for multiplex genome engineering of polyploid industrial yeast strains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lian, Jiazhang; Bao, Zehua; Hu, Sumeng

The CRISPR/Cas9 system has been widely used for multiplex genome engineering of Saccharomyces cerevisiae. Furthermore, its application in manipulating industrial yeast strains is less successful, probably due to the genome complexity and low copy numbers of gRNA expression plasmids. Here we developed an efficient CRISPR/Cas9 system for industrial yeast strain engineering by using our previously engineered plasmids with increased copy numbers. Four genes in both a diploid strain (Ethanol Red, 8 alleles in total) and a triploid strain (ATCC 4124, 12 alleles in total) were knocked out in a single step with 100% efficiency. This system was used to constructmore » xylose-fermenting, lactate-producing industrial yeast strains, in which ALD6, PHO13, LEU2, and URA3 were disrupted in a single step followed by the introduction of a xylose utilization pathway and a lactate biosynthetic pathway on auxotrophic marker plasmids. The optimized CRISPR/Cas9 system provides a powerful tool for the development of industrial yeast based microbial cell factories.« less

Engineered CRISPR/Cas9 system for multiplex genome engineering of polyploid industrial yeast strains.

PubMed

Lian, Jiazhang; Bao, Zehua; Hu, Sumeng; Zhao, Huimin

2018-06-01

The CRISPR/Cas9 system has been widely used for multiplex genome engineering of Saccharomyces cerevisiae. However, its application in manipulating industrial yeast strains is less successful, probably due to the genome complexity and low copy numbers of gRNA expression plasmids. Here we developed an efficient CRISPR/Cas9 system for industrial yeast strain engineering by using our previously engineered plasmids with increased copy numbers. Four genes in both a diploid strain (Ethanol Red, 8 alleles in total) and a triploid strain (ATCC 4124, 12 alleles in total) were knocked out in a single step with 100% efficiency. This system was used to construct xylose-fermenting, lactate-producing industrial yeast strains, in which ALD6, PHO13, LEU2, and URA3 were disrupted in a single step followed by the introduction of a xylose utilization pathway and a lactate biosynthetic pathway on auxotrophic marker plasmids. The optimized CRISPR/Cas9 system provides a powerful tool for the development of industrial yeast based microbial cell factories. © 2018 Wiley Periodicals, Inc.

Metabolism of the Fusarium mycotoxins zearalenone and deoxynivalenol by yeast strains of technological relevance.

PubMed

Böswald, C; Engelhardt, G; Vogel, H; Wallnöfer, P R

1995-01-01

The Fusarium mycotoxin zearalenone (ZEA), added at a level of 2 micrograms/ml, was reduced stereoselectively by cultures of Candida tropicalis, Torulaspora delbrückii, Zygosaccharomyces rouxii, and 7 Saccharomyces strains to both alpha- and beta-zearalenol. In contrast, only alpha-zearalenol was produced from ZEA by Pichia fermentans and several yeast strains of the genera Candida, Hansenula, Brettanomyces, Schizosaccharomyces, and Saccharomycopsis. No glucose conjugates of ZEA (zearalenone-4-beta-D-glucopyranoside) were detected. The trichothecene mycotoxin deoxynivalenol (DON) was not metabolized by any of the yeast strains that were used for analysis.

Cellobiose fermenting yeast produces varied forms of native ß-glucosidase

USDA-ARS?s Scientific Manuscript database

The rapid growing yeast strain NRRL Y-50464 is robust to environmental stress and resistant to 2-furaldehyde (furfural) and 5-[hydroxymethyl]-2-furaldehyde (HMF). It is able to utilize cellobiose as its sole source of carbon and produces ethanol from lignocellulosic biomass by simultaneous saccharif...

L-arabinose fermenting yeast

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Min; Singh, Arjun; Suominen, Pirkko

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.

L-arabinose fermenting yeast

DOEpatents

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.

A new pullulan-producing yeast and medium optimization for its exopolysaccharide production

NASA Astrophysics Data System (ADS)

Zhao, Shuangzhi; Chi, Zhenming

2003-04-01

Yeast strain Y68 producing high level of pullulan was isolated from the phyton collected in Toulouse, France. This strain was identified to be Rhodotorula bacarum by BIOLOG analysis. This is the first report that pullulan was produced by Rhodotorula bacarum. The optimal medium (g L-1) for pullulan production by this strain was 80 glucose, 20 soybean cake hydrolysate, 5 K2HPO4, 1 NaCl, 0.2 MgSO4·7H2O, 0.6 (NH4)2SO4, pH 7.0. Under this condition, 54 gL-1 pullulan was produced within 60 h at 30°C. Pullulan is a better starting material for producing marine prodrugs.

Genome sequence of the oleaginous yeast Rhodotorula toruloides strain CGMCC 2.1609.

PubMed

Sambles, Christine; Middelhaufe, Sabine; Soanes, Darren; Kolak, Dagmara; Lux, Thomas; Moore, Karen; Matoušková, Petra; Parker, David; Lee, Rob; Love, John; Aves, Stephen J

2017-09-01

Most eukaryotic oleaginous species are yeasts and among them the basidiomycete red yeast, Rhodotorula ( Rhodosporidium ) toruloides (Pucciniomycotina) is known to produce high quantities of lipids when grown in nitrogen-limiting media, and has potential for biodiesel production. The genome of the CGMCC 2.1609 strain of this oleaginous red yeast was sequenced using a hybrid of Roche 454 and Illumina technology generating 13 × coverage. The de novo assembly was carried out using MIRA and scaffolded using MAQ and BAMBUS. The sequencing and assembly resulted in 365 scaffolds with total genome size of 33.4 Mb. The complete genome sequence of this strain was deposited in GenBank and the accession number is LKER00000000. The annotation is available on Figshare (doi:10.6084/m9.figshare.4754251).

New Lager Brewery Strains Obtained by Crossing Techniques Using Cachaça (Brazilian Spirit) Yeasts

PubMed Central

Figueiredo, Bruna Inez Carvalho; Saraiva, Margarete Alice Fontes; de Souza Pimenta, Paloma Patrick; de Souza Testasicca, Miriam Conceição; Sampaio, Geraldo Magela Santos; da Cunha, Aureliano Claret; Afonso, Luis Carlos Crocco; Vieira de Queiroz, Marisa; de Miranda Castro, Ieso

2017-01-01

the use of breeding/hybridization techniques to generate yeast strains that would be appropriate for producing new lager beers by exploring the capacity of cachaça yeast strains to flocculate and to ferment maltose at low temperature, with the concomitant production of flavoring compounds. PMID:28778887

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

Producing aglycons of ginsenosides in bakers' yeast

PubMed Central

Dai, Zhubo; Wang, Beibei; Liu, Yi; Shi, Mingyu; Wang, Dong; Zhang, Xianan; Liu, Tao; Huang, Luqi; Zhang, Xueli

2014-01-01

Ginsenosides are the primary bioactive components of ginseng, which is a popular medicinal plant that exhibits diverse pharmacological activities. Protopanaxadiol, protopanaxatriol and oleanolic acid are three basic aglycons of ginsenosides. Producing aglycons of ginsenosides in Saccharomyces cerevisiae was realized in this work and provides an alternative route compared to traditional extraction methods. Synthetic pathways of these three aglycons were constructed in S. cerevisiae by introducing β-amyrin synthase, oleanolic acid synthase, dammarenediol-II synthase, protopanaxadiol synthase, protopanaxatriol synthase and NADPH-cytochrome P450 reductase from different plants. In addition, a truncated 3-hydroxy-3-methylglutaryl-CoA reductase, squalene synthase and 2,3-oxidosqualene synthase genes were overexpressed to increase the precursor supply for improving aglycon production. Strain GY-1 was obtained, which produced 17.2 mg/L protopanaxadiol, 15.9 mg/L protopanaxatriol and 21.4 mg/L oleanolic acid. The yeast strains engineered in this work can serve as the basis for creating an alternative way for producing ginsenosides in place of extractions from plant sources. PMID:24424342

Construction of a recombinant wine yeast strain expressing beta-(1,4)-endoglucanase and its use in microvinification processes.

PubMed Central

Pérez-González, J A; González, R; Querol, A; Sendra, J; Ramón, D

1993-01-01

A genetic transformation system for an industrial wine yeast strain is presented here. The system is based on the acquisition of cycloheximide resistance and is a direct adaptation of a previously published procedure for brewing yeasts (L. Del Pozo, D. Abarca, M. G. Claros, and A. Jiménez, Curr. Genet. 19:353-358, 1991). Transformants arose at an optimal frequency of 0.5 transformant per microgram of DNA, are stable in the absence of selective pressure, and produce wine in the same way as the untransformed industrial strain. By using this transformation protocol, a filamentous fungal beta-(1,4)-endoglucanase gene has been expressed in an industrial wine yeast under the control of the yeast actin gene promoter. Endoglucanolytic wine yeast secretes the fungal enzyme to the must, producing a wine with an increased fruity aroma. Images PMID:8215355

Construction of a lactose-assimilating strain of baker's yeast.

PubMed

Adam, A C; Prieto, J A; Rubio-Texeira, M; Polaina, J

1999-09-30

A recombinant strain of baker's yeast has been constructed which can assimilate lactose efficiently. This strain has been designed to allow its propagation in whey, the byproduct resulting from cheese-making. The ability to metabolize lactose is conferred by the functional expression of two genes from Kluyveromyces lactis, LAC12 and LAC4, which encode a lactose permease and a beta-galactosidase, respectively. To make the recombinant strain more acceptable for its use in bread-making, the genetic transformation of the host baker's yeast was carried out with linear fragments of DNA of defined sequence, carrying as the only heterologous material the coding regions of the two K. lactis genes. Growth of the new strain on cheese whey affected neither the quality of bread nor the yeast gassing power. The significance of the newly developed strain is two-fold: it affords a cheap alternative to the procedure generally used for the propagation of baker's yeast, and it offers a profitable use for cheese whey. Copyright 1999 John Wiley & Sons, Ltd.

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. © 2014 The Authors. FEMS Microbiology Reviews published by John Wiley & Sons Ltd on behalf of Federation of European Microbiological Societies.

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##

Yeast strains as potential aroma enhancers in dry fermented sausages.

PubMed

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

2015-11-06

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. Copyright © 2015 Elsevier B.V. All rights reserved.

Producing human ceramide-NS by metabolic engineering using yeast Saccharomyces cerevisiae.

PubMed

Murakami, Suguru; Shimamoto, Toshi; Nagano, Hideaki; Tsuruno, Masahiro; Okuhara, Hiroaki; Hatanaka, Haruyo; Tojo, Hiromasa; Kodama, Yukiko; Funato, Kouichi

2015-11-17

Ceramide is one of the most important intercellular components responsible for the barrier and moisture retention functions of the skin. Because of the risks involved with using products of animal origin and the low productivity of plants, the availability of ceramides is currently limited. In this study, we successfully developed a system that produces sphingosine-containing human ceramide-NS in the yeast Saccharomyces cerevisiae by eliminating the genes for yeast sphingolipid hydroxylases (encoded by SUR2 and SCS7) and introducing the gene for a human sphingolipid desaturase (encoded by DES1). The inactivation of the ceramidase gene YDC1, overexpression of the inositol phosphosphingolipid phospholipase C gene ISC1, and endoplasmic reticulum localization of the DES1 gene product resulted in enhanced production of ceramide-NS. The engineered yeast strains can serve as hosts not only for providing a sustainable source of ceramide-NS but also for developing further systems to produce sphingosine-containing sphingolipids.

Laboratory evolution of copper tolerant yeast strains

PubMed Central

2012-01-01

Background Yeast strains endowed with robustness towards copper and/or enriched in intracellular Cu might find application in biotechnology processes, among others in the production of functional foods. Moreover, they can contribute to the study of human diseases related to impairments of copper metabolism. In this study, we investigated the molecular and physiological factors that confer copper tolerance to strains of baker's yeasts. Results We characterized the effects elicited in natural strains of Candida humilis and Saccharomyces cerevisiae by the exposure to copper in the culture broth. We observed that, whereas the growth of Saccharomyces cells was inhibited already at low Cu concentration, C. humilis was naturally robust and tolerated up to 1 g · L-1 CuSO4 in the medium. This resistant strain accumulated over 7 mg of Cu per gram of biomass and escaped severe oxidative stress thanks to high constitutive levels of superoxide dismutase and catalase. Both yeasts were then "evolved" to obtain hyper-resistant cells able to proliferate in high copper medium. While in S. cerevisiae the evolution of robustness towards Cu was paralleled by the increase of antioxidative enzymes, these same activities decreased in evolved hyper-resistant Candida cells. We also characterized in some detail changes in the profile of copper binding proteins, that appeared to be modified by evolution but, again, in a different way in the two yeasts. Conclusions Following evolution, both Candida and Saccharomyces cells were able to proliferate up to 2.5 g · L-1 CuSO4 and to accumulate high amounts of intracellular copper. The comparison of yeasts differing in their robustness, allowed highlighting physiological and molecular determinants of natural and acquired copper tolerance. We observed that different mechanisms contribute to confer metal tolerance: the control of copper uptake, changes in the levels of enzymes involved in oxidative stress response and changes in the copper

Identification of yeast strains isolated from marcha in Sikkim, a microbial starter for amylolytic fermentation.

PubMed

Tsuyoshi, Naoko; Fudou, Ryosuke; Yamanaka, Shigeru; Kozaki, Michio; Tamang, Namrata; Thapa, Saroj; Tamang, Jyoti P

2005-03-15

Marcha or murcha is a traditional amylolytic starter used to produce sweet-sour alcoholic drinks, commonly called jaanr in the Himalayan regions of India, Nepal, Bhutan, and Tibet (China). The aim of this study was to examine the microflora of marcha collected from Sikkim in India, focusing on yeast flora and their roles. Twenty yeast strains were isolated from six samples of marcha and identified by genetic and phenotypic methods. They were first classified into four groups (Group I, II, III, and IV) based on physiological features using an API test. Phylogenetic, morphological, and physiological characterization identified the isolates as Saccharomyces bayanus (Group I); Candida glabrata (Group II); Pichia anomala (Group III); and Saccharomycopsis fibuligera, Saccharomycopsis capsularis, and Pichia burtonii (Group IV). Among them, the Group I, II, and III strains produced ethanol. The isolates of Group IV had high amylolytic activity. Because all marcha samples tested contained both starch degraders and ethanol producers, it was hypothesized that all four groups of yeast (Group I, II, III, and IV) contribute to starch-based alcohol fermentation.

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.

Quality parameters and RAPD-PCR differentiation of commercial baker's yeast and hybrid strains.

PubMed

El-Fiky, Zaki A; Hassan, Gamal M; Emam, Ahmed M

2012-06-01

Baker's yeast, Saccharomyces cerevisiae, is a key component in bread baking. Total of 12 commercial baker's yeast and 2 hybrid strains were compared using traditional quality parameters. Total of 5 strains with high leavening power and the 2 hybrid strains were selected and evaluated for their alpha-amylase, maltase, glucoamylase enzymes, and compared using random amplified polymorphic DNA (RAPD). The results revealed that all selected yeast strains have a low level of alpha-amylase and a high level of maltase and glucoamylase enzymes. Meanwhile, the Egyptian yeast strain (EY) had the highest content of alpha-amylase and maltase enzymes followed by the hybrid YH strain. The EY and YH strains have the highest content of glucoamylase enzyme almost with the same level. The RAPD banding patterns showed a wide variation among commercial yeast and hybrid strains. The closely related Egyptian yeast strains (EY and AL) demonstrated close similarity of their genotypes. The 2 hybrid strains were clustered to Turkish and European strains in 1 group. The authors conclude that the identification of strains and hybrids using RAPD technique was useful in determining their genetic relationship. These results can be useful not only for the basic research, but also for the quality control in baking factories. © 2012 Institute of Food Technologists®

Brewing characteristics of haploid strains isolated from sake yeast Kyokai No. 7.

PubMed

Katou, Taku; Kitagaki, Hiroshi; Akao, Takeshi; Shimoi, Hitoshi

2008-11-01

Sake yeast exhibit various characteristics that make them more suitable for sake brewing compared to other yeast strains. Since sake yeast strains are Saccharomyces cerevisiae heterothallic diploid strains, it is likely that they have heterozygous alleles on homologous chromosomes (heterozygosity) due to spontaneous mutations. If this is the case, segregation of phenotypic traits in haploid strains after sporulation and concomitant meiosis of sake yeast strains would be expected to occur. To examine this hypothesis, we isolated 100 haploid strains from Kyokai No. 7 (K7), a typical sake yeast strain in Japan, and compared their brewing characteristics in small-scale sake-brewing tests. Analyses of the resultant sake samples showed a smooth and continuous distribution of analytical values for brewing characteristics, suggesting that K7 has multiple heterozygosities that affect brewing characteristics and that these heterozygous alleles do segregate after sporulation. Correlation and principal component analyses suggested that the analytical parameters could be classified into two groups, indicating fermentation ability and sake flavour. (c) 2008 John Wiley & Sons, Ltd.

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.

Melatonin and derived l-tryptophan metabolites produced during alcoholic fermentation by different wine yeast strains.

PubMed

Fernández-Cruz, E; Álvarez-Fernández, M A; Valero, E; Troncoso, A M; García-Parrilla, M C

2017-02-15

Melatonin is a neurohormone involved in the regulation of circadian rhythms in humans. Evidence has recently been found of its occurrence in wines and its role in the winemaking process. The yeast Saccharomyces cerevisiae is consequently thought to be important in Melatonin synthesis, but limited data and reference texts are available on this synthetic pathway. This paper aims to elucidate whether the synthetic pathway of Melatonin in Saccharomyces and non-Saccharomyces strains involves these intermediates. To this end, seven commercial strains comprising Saccharomyces cerevisiae (Red Fruit, ES488, Lalvin QA23, Uvaferm BC, and Lalvin ICV GRE) and non-Saccharomyces (Torulaspora delbrueckii and Metschnikowia pulcherrima) were monitored, under controlled fermentation conditions, in synthetic must, for seven days. Samples were analysed using a UHPLC-HRMS system (Qexactive). Five out of the seven strains formed Melatonin during the fermentation process: three S. cerevisiae strains and the two non-Saccharomyces. Additionally, other compounds derived from l-tryptophan occurred during fermentation. Copyright © 2016 Elsevier Ltd. All rights reserved.

Brettanomyces acidodurans sp. nov., a new acetic acid producing yeast species from olive oil.

PubMed

Péter, Gábor; Dlauchy, Dénes; Tóbiás, Andrea; Fülöp, László; Podgoršek, Martina; Čadež, Neža

2017-05-01

Two yeast strains representing a hitherto undescribed yeast species were isolated from olive oil and spoiled olive oil originating from Spain and Israel, respectively. Both strains are strong acetic acid producers, equipped with considerable tolerance to acetic acid. The cultures are not short-lived. Cellobiose is fermented as well as several other sugars. The sequences of their large subunit (LSU) rRNA gene D1/D2 domain are very divergent from the sequences available in the GenBank. They differ from the closest hit, Brettanomyces naardenensis by about 27%, mainly substitutions. Sequence analyses of the concatenated dataset from genes of the small subunit (SSU) rRNA, LSU rRNA and translation elongation factor-1α (EF-1α) placed the two strains as an early diverging member of the Brettanomyces/Dekkera clade with high bootstrap support. Sexual reproduction was not observed. The name Brettanomyces acidodurans sp. nov. (holotype: NCAIM Y.02178 T ; isotypes: CBS 14519 T  = NRRL Y-63865 T  = ZIM 2626 T , MycoBank no.: MB 819608) is proposed for this highly divergent new yeast species.

Inaccurate DNA Synthesis in Cell Extracts of Yeast Producing Active Human DNA Polymerase Iota

PubMed Central

Makarova, Alena V.; Grabow, Corinn; Gening, Leonid V.; Tarantul, Vyacheslav Z.; Tahirov, Tahir H.; Bessho, Tadayoshi; Pavlov, Youri I.

2011-01-01

Mammalian Pol ι has an unusual combination of properties: it is stimulated by Mn2+ ions, can bypass some DNA lesions and misincorporates “G” opposite template “T” more frequently than incorporates the correct “A.” We recently proposed a method of detection of Pol ι activity in animal cell extracts, based on primer extension opposite the template T with a high concentration of only two nucleotides, dGTP and dATP (incorporation of “G” versus “A” method of Gening, abbreviated as “misGvA”). We provide unambiguous proof of the “misGvA” approach concept and extend the applicability of the method for the studies of variants of Pol ι in the yeast model system with different cation cofactors. We produced human Pol ι in baker's yeast, which do not have a POLI ortholog. The “misGvA” activity is absent in cell extracts containing an empty vector, or producing catalytically dead Pol ι, or Pol ι lacking exon 2, but is robust in the strain producing wild-type Pol ι or its catalytic core, or protein with the active center L62I mutant. The signature pattern of primer extension products resulting from inaccurate DNA synthesis by extracts of cells producing either Pol ι or human Pol η is different. The DNA sequence of the template is critical for the detection of the infidelity of DNA synthesis attributed to DNA Pol ι. The primer/template and composition of the exogenous DNA precursor pool can be adapted to monitor replication fidelity in cell extracts expressing various error-prone Pols or mutator variants of accurate Pols. Finally, we demonstrate that the mutation rates in yeast strains producing human DNA Pols ι and η are not elevated over the control strain, despite highly inaccurate DNA synthesis by their extracts. PMID:21304950

Inaccurate DNA synthesis in cell extracts of yeast producing active human DNA polymerase iota.

PubMed

Makarova, Alena V; Grabow, Corinn; Gening, Leonid V; Tarantul, Vyacheslav Z; Tahirov, Tahir H; Bessho, Tadayoshi; Pavlov, Youri I

2011-01-31

Mammalian Pol ι has an unusual combination of properties: it is stimulated by Mn(2+) ions, can bypass some DNA lesions and misincorporates "G" opposite template "T" more frequently than incorporates the correct "A." We recently proposed a method of detection of Pol ι activity in animal cell extracts, based on primer extension opposite the template T with a high concentration of only two nucleotides, dGTP and dATP (incorporation of "G" versus "A" method of Gening, abbreviated as "misGvA"). We provide unambiguous proof of the "misGvA" approach concept and extend the applicability of the method for the studies of variants of Pol ι in the yeast model system with different cation cofactors. We produced human Pol ι in baker's yeast, which do not have a POLI ortholog. The "misGvA" activity is absent in cell extracts containing an empty vector, or producing catalytically dead Pol ι, or Pol ι lacking exon 2, but is robust in the strain producing wild-type Pol ι or its catalytic core, or protein with the active center L62I mutant. The signature pattern of primer extension products resulting from inaccurate DNA synthesis by extracts of cells producing either Pol ι or human Pol η is different. The DNA sequence of the template is critical for the detection of the infidelity of DNA synthesis attributed to DNA Pol ι. The primer/template and composition of the exogenous DNA precursor pool can be adapted to monitor replication fidelity in cell extracts expressing various error-prone Pols or mutator variants of accurate Pols. Finally, we demonstrate that the mutation rates in yeast strains producing human DNA Pols ι and η are not elevated over the control strain, despite highly inaccurate DNA synthesis by their extracts.

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

Whole-Genome Analysis of Three Yeast Strains Used for Production of Sherry-Like Wines Revealed Genetic Traits Specific to Flor Yeasts

PubMed Central

Eldarov, Mikhail A.; Beletsky, Alexey V.; Tanashchuk, Tatiana N.; Kishkovskaya, Svetlana A.; Ravin, Nikolai V.; Mardanov, Andrey V.

2018-01-01

Flor yeast strains represent a specialized group of Saccharomyces cerevisiae yeasts used for biological wine aging. We have sequenced the genomes of three flor strains originated from different geographic regions and used for production of sherry-like wines in Russia. According to the obtained phylogeny of 118 yeast strains, flor strains form very tight cluster adjacent to the main wine clade. SNP analysis versus available genomes of wine and flor strains revealed 2,270 genetic variants in 1,337 loci specific to flor strains. Gene ontology analysis in combination with gene content evaluation revealed a complex landscape of possibly adaptive genetic changes in flor yeast, related to genes associated with cell morphology, mitotic cell cycle, ion homeostasis, DNA repair, carbohydrate metabolism, lipid metabolism, and cell wall biogenesis. Pangenomic analysis discovered the presence of several well-known “non-reference” loci of potential industrial importance. Events of gene loss included deletions of asparaginase genes, maltose utilization locus, and FRE-FIT locus involved in iron transport. The latter in combination with a flor-yeast-specific mutation in the Aft1 transcription factor gene is likely to be responsible for the discovered phenotype of increased iron sensitivity and improved iron uptake of analyzed strains. Expansion of the coding region of the FLO11 flocullin gene and alteration of the balance between members of the FLO gene family are likely to positively affect the well-known propensity of flor strains for velum formation. Our study provides new insights in the nature of genetic variation in flor yeast strains and demonstrates that different adaptive properties of flor yeast strains could have evolved through different mechanisms of genetic variation. PMID:29867869

Induction of multiple pleiotropic drug resistance genes in yeast engineered to produce an increased level of anti-malarial drug precursor, artemisinic acid.

PubMed

Ro, Dae-Kyun; Ouellet, Mario; Paradise, Eric M; Burd, Helcio; Eng, Diana; Paddon, Chris J; Newman, Jack D; Keasling, Jay D

2008-11-04

Due to the global occurrence of multi-drug-resistant malarial parasites (Plasmodium falciparum), the anti-malarial drug most effective against malaria is artemisinin, a natural product (sesquiterpene lactone endoperoxide) extracted from sweet wormwood (Artemisia annua). However, artemisinin is in short supply and unaffordable to most malaria patients. Artemisinin can be semi-synthesized from its precursor artemisinic acid, which can be synthesized from simple sugars using microorganisms genetically engineered with genes from A. annua. In order to develop an industrially competent yeast strain, detailed analyses of microbial physiology and development of gene expression strategies are required. Three plant genes coding for amorphadiene synthase, amorphadiene oxidase (AMO or CYP71AV1), and cytochrome P450 reductase, which in concert divert carbon flux from farnesyl diphosphate to artemisinic acid, were expressed from a single plasmid. The artemisinic acid production in the engineered yeast reached 250 microg mL(-1) in shake-flask cultures and 1 g L(-1) in bio-reactors with the use of Leu2d selection marker and appropriate medium formulation. When plasmid stability was measured, the yeast strain synthesizing amorphadiene alone maintained the plasmid in 84% of the cells, whereas the yeast strain synthesizing artemisinic acid showed poor plasmid stability. Inactivation of AMO by a point-mutation restored the high plasmid stability, indicating that the low plasmid stability is not caused by production of the AMO protein but by artemisinic acid synthesis or accumulation. Semi-quantitative reverse-transcriptase (RT)-PCR and quantitative real time-PCR consistently showed that pleiotropic drug resistance (PDR) genes, belonging to the family of ATP-Binding Cassette (ABC) transporter, were massively induced in the yeast strain producing artemisinic acid, relative to the yeast strain producing the hydrocarbon amorphadiene alone. Global transcriptional analysis by yeast

Live Yeast and Yeast Cell Wall Supplements Enhance Immune Function and Performance in Food-Producing Livestock: A Review †,‡

PubMed Central

Broadway, Paul R.; Carroll, Jeffery A.; Burdick Sanchez, Nicole C.

2015-01-01

More livestock producers are seeking natural alternatives to antibiotics and antimicrobials, and searching for supplements to enhance growth performance, and general animal health and well-being. Some of the compounds currently being utilized and studied are live yeast and yeast-based products derived from the strain Saccharomyces cerevisiae. These products have been reported to have positive effects both directly and indirectly on the immune system and its subsequent biomarkers, thereby mitigating negative effects associated with stress and disease. These yeast-based products have also been reported to simultaneously enhance growth and performance by enhancing dry matter intake (DMI) and average daily gain (ADG) perhaps through the establishment of a healthy gastrointestinal tract. These products may be especially useful in times of potential stress such as during birth, weaning, early lactation, and during the receiving period at the feedlot. Overall, yeast supplements appear to possess the ability to improve animal health and metabolism while decreasing morbidity, thereby enhancing profitability of these animals. PMID:27682097

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.

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.

Association of Constitutive Hyperphosphorylation of Hsf1p with a Defective Ethanol Stress Response in Saccharomyces cerevisiae Sake Yeast Strains

PubMed Central

Noguchi, Chiemi; Watanabe, Daisuke; Zhou, Yan; Akao, Takeshi

2012-01-01

Modern sake yeast strains, which produce high concentrations of ethanol, are unexpectedly sensitive to environmental stress during sake brewing. To reveal the underlying mechanism, we investigated a well-characterized yeast stress response mediated by a heat shock element (HSE) and heat shock transcription factor Hsf1p in Saccharomyces cerevisiae sake yeast. The HSE-lacZ activity of sake yeast during sake fermentation and under acute ethanol stress was severely impaired compared to that of laboratory yeast. Moreover, the Hsf1p of modern sake yeast was highly and constitutively hyperphosphorylated, irrespective of the extracellular stress. Since HSF1 allele replacement did not significantly affect the HSE-mediated ethanol stress response or Hsf1p phosphorylation patterns in either sake or laboratory yeast, the regulatory machinery of Hsf1p is presumed to function differently between these types of yeast. To identify phosphatases whose loss affected the control of Hsf1p, we screened a series of phosphatase gene deletion mutants in a laboratory strain background. Among the 29 mutants, a Δppt1 mutant exhibited constitutive hyperphosphorylation of Hsf1p, similarly to the modern sake yeast strains, which lack the entire PPT1 gene locus. We confirmed that the expression of laboratory yeast-derived functional PPT1 recovered the HSE-mediated stress response of sake yeast. In addition, deletion of PPT1 in laboratory yeast resulted in enhanced fermentation ability. Taken together, these data demonstrate that hyperphosphorylation of Hsf1p caused by loss of the PPT1 gene at least partly accounts for the defective stress response and high ethanol productivity of modern sake yeast strains. PMID:22057870

Association of constitutive hyperphosphorylation of Hsf1p with a defective ethanol stress response in Saccharomyces cerevisiae sake yeast strains.

PubMed

Noguchi, Chiemi; Watanabe, Daisuke; Zhou, Yan; Akao, Takeshi; Shimoi, Hitoshi

2012-01-01

Modern sake yeast strains, which produce high concentrations of ethanol, are unexpectedly sensitive to environmental stress during sake brewing. To reveal the underlying mechanism, we investigated a well-characterized yeast stress response mediated by a heat shock element (HSE) and heat shock transcription factor Hsf1p in Saccharomyces cerevisiae sake yeast. The HSE-lacZ activity of sake yeast during sake fermentation and under acute ethanol stress was severely impaired compared to that of laboratory yeast. Moreover, the Hsf1p of modern sake yeast was highly and constitutively hyperphosphorylated, irrespective of the extracellular stress. Since HSF1 allele replacement did not significantly affect the HSE-mediated ethanol stress response or Hsf1p phosphorylation patterns in either sake or laboratory yeast, the regulatory machinery of Hsf1p is presumed to function differently between these types of yeast. To identify phosphatases whose loss affected the control of Hsf1p, we screened a series of phosphatase gene deletion mutants in a laboratory strain background. Among the 29 mutants, a Δppt1 mutant exhibited constitutive hyperphosphorylation of Hsf1p, similarly to the modern sake yeast strains, which lack the entire PPT1 gene locus. We confirmed that the expression of laboratory yeast-derived functional PPT1 recovered the HSE-mediated stress response of sake yeast. In addition, deletion of PPT1 in laboratory yeast resulted in enhanced fermentation ability. Taken together, these data demonstrate that hyperphosphorylation of Hsf1p caused by loss of the PPT1 gene at least partly accounts for the defective stress response and high ethanol productivity of modern sake yeast strains.

The hydrolytic activity of esterases in the yeast Saccharomyces cerevisiae is strain dependent.

PubMed

Kwolek-Mirek, Magdalena; Bednarska, Sabina; Zadrąg-Tęcza, Renata; Bartosz, Grzegorz

2011-11-01

Ester precursors of fluorogenic or chromogenic probes are often employed in studies of yeast cell biology. This study was aimed at a comparison of the ability of several commonly used laboratory wild-type Saccharomyces cerevisiae strains to hydrolyse the following model esters: fluorescein diacetate, 2-naphthyl acetate, PNPA (p-nitrophenyl acetate) and AMQI (7-acetoxy-1-methylquinolinum iodide). In all the strains, the esterase activity was localized mainly to the cytosol. Considerable differences in esterase activity were observed between various wild-type laboratory yeast strains. The phase of growth also contributed to the variation in esterase activity of the yeast. This diversity implies the need for caution in using intracellularly hydrolysed probes for a comparison of yeast strains with various genetic backgrounds.

Biocontrol activity of four non- and low-fermenting yeast strains against Aspergillus carbonarius and their ability to remove ochratoxin A from grape juice.

PubMed

Fiori, Stefano; Urgeghe, Pietro Paolo; Hammami, Walid; Razzu, Salvatorico; Jaoua, Samir; Migheli, Quirico

2014-10-17

Aspergillus spp. infection of grape may lead to ochratoxin A (OTA) contamination in processed beverages such as wine and grape juice. The aim of the current study was to evaluate the biocontrol potential of two non-fermenting (Cyberlindnera jadinii 273 and Candida friedrichii 778) and two low-fermenting (Candida intermedia 235 and Lachancea thermotolerans 751) yeast strains against the pathogenic fungus and OTA-producer Aspergillus carbonarius, and their ability to remove OTA from grape juice. Two strains, 235 and 751, showed a significant ability to inhibit A. carbonarius both on grape berries and in in vitro experiments. Neither their filtrate nor their autoclaved filtrate culture broth was able to prevent consistently pathogen growth. Volatile organic compounds (VOCs) produced by all four selected yeasts were likely able to consistently prevent pathogen sporulation in vitro. VOCs produced by the non-fermenting strain 778 also significantly reduced A. carbonarius vegetative growth. Three yeast strains (235, 751, and 778) efficiently adsorbed artificially spiked OTA from grape juice, while autoclaving treatment improved OTA adsorption capacity by all the four tested strains. Biological control of A. carbonarius and OTA-decontamination using yeast is proposed as an approach to meet the Islamic dietary laws concerning the absence of alcohol in halal beverages. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Divergence in wine characteristics produced by wild and domesticated strains of Saccharomyces cerevisiae

PubMed Central

Hyma, Katie E; Saerens, Sofie M; Verstrepen, Kevin J; Fay, Justin C

2011-01-01

The budding yeast Saccharomyces cerevisiae is the primary species used by wine makers to convert sugar into alcohol during wine fermentation. Saccharomyces cerevisiae is found in vineyards, but is also found in association with oak trees and other natural sources. Although wild strains of S. cerevisiae as well as other Saccharomyces species are also capable of wine fermentation, a genetically distinct group of S. cerevisiae strains is primarily used to produce wine, consistent with the idea that wine making strains have been domesticated for wine production. In this study, we demonstrate that humans can distinguish between wines produced using wine strains and wild strains of S. cerevisiae as well as its sibling species, Saccharomyces paradoxus. Wine strains produced wine with fruity and floral characteristics, whereas wild strains produced wine with earthy and sulfurous characteristics. The differences that we observe between wine and wild strains provides further evidence that wine strains have evolved phenotypes that are distinct from their wild ancestors and relevant to their use in wine production. PMID:22093681

Comparative behaviour of yeast strains for ethanolic fermentation of culled apple juice.

PubMed

Modi, D R; Garg, S K; Johri, B N

1998-07-01

The culled apple juice contained (% w/v): nitrogen, 0.036; total sugars, 11.6 and was of pH 3.9. Saccharomyces cerevisiae NCIM 3284, Pichia kluyeri and Candida krusei produced more ethanol from culled apple juice at its optimum initial pH 4.5, whereas S. cerevisiae NCIM 3316 did so at pH 5.0. An increase in sugar concentration of apple juice from natural 11.6% to 20% exhibited enhanced ethanol production and improved fermentation efficiency of both the S. cerevisiae strains, whereas P. kluyveri and C. krusei produced high ethanol at 11.6% and 16.0% sugar levels, respectively. Urea was stimulatory for ethanol production as well as fermentation efficiency of the yeast strains under study.

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

Probiotic yeasts: Anti-inflammatory potential of various non-pathogenic strains in experimental colitis in mice

PubMed Central

Foligné, Benoît; Dewulf, Joëlle; Vandekerckove, Pascal; Pignède, Georges; Pot, Bruno

2010-01-01

AIM: To evaluate the in vitro immunomodulation capacity of various non-pathogenic yeast strains and to investigate the ability of some of these food grade yeasts to prevent experimental colitis in mice. METHODS: In vitro immunomodulation was assessed by measuring cytokines [interleukin (IL)-12p70, IL-10, tumor necrosis factor and interferon γ] released by human peripheral blood mononuclear cells after 24 h stimulation with 6 live yeast strains (Saccharomyces ssp.) and with bacterial reference strains. A murine model of acute 2-4-6-trinitrobenzene sulfonic acid (TNBS)-colitis was next used to evaluate the distinct prophylactic protective capacities of three yeast strains compared with the performance of prednisolone treatment. RESULTS: The six yeast strains all showed similar non-discriminating anti-inflammatory potential when tested on immunocompetent cells in vitro. However, although they exhibited similar colonization patterns in vivo, some yeast strains showed significant anti-inflammatory activities in the TNBS-induced colitis model, whereas others had weaker or no preventive effect at all, as evidenced by colitis markers (body-weight loss, macroscopic and histological scores, myeloperoxidase activities and blood inflammatory markers). CONCLUSION: A careful selection of strains is required among the biodiversity of yeasts for specific clinical studies, including applications in inflammatory bowel disease and other therapeutic uses. PMID:20440854

Virgin olive oil yeasts: A review.

PubMed

Ciafardini, Gino; Zullo, Biagi Angelo

2018-04-01

This review summarizes current knowledge on virgin olive oil yeasts. Newly produced olive oil contains solid particles and micro drops of vegetation water in which yeasts reproduce to become the typical microbiota of olive oil. To date, about seventeen yeast species have been isolated from different types of olive oils and their by-products, of which six species have been identified as new species. Certain yeast species contribute greatly to improving the sensorial characteristics of the newly produced olive oil, whereas other species are considered harmful as they can damage the oil quality through the production of unpleasant flavors and triacylglycerol hydrolysis. Studies carried out in certain yeast strains have demonstrated the presence of defects in olive oil treated with Candida adriatica, Nakazawaea wickerhamii and Candida diddensiae specific strains, while other olive oil samples treated with other Candida diddensiae strains were defect-free after four months of storage and categorized as extra virgin. A new acetic acid producing yeast species, namely, Brettanomyces acidodurans sp. nov., which was recently isolated from olive oil, could be implicated in the wine-vinegary defect of the product. Other aspects related to the activity of the lipase-producing yeasts and the survival of the yeast species in the flavored olive oils are also discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Comparison of DNA-based techniques for differentiation of production strains of ale and lager brewing yeast.

PubMed

Kopecká, J; Němec, M; Matoulková, D

2016-06-01

Brewing yeasts are classified into two species-Saccharomyces pastorianus and Saccharomyces cerevisiae. Most of the brewing yeast strains are natural interspecies hybrids typically polyploids and their identification is thus often difficult giving heterogenous results according to the method used. We performed genetic characterization of a set of the brewing yeast strains coming from several yeast culture collections by combination of various DNA-based techniques. The aim of this study was to select a method for species-specific identification of yeast and discrimination of yeast strains according to their technological classification. A group of 40 yeast strains were characterized using PCR-RFLP analysis of ITS-5·8S, NTS, HIS4 and COX2 genes, multiplex PCR, RAPD-PCR of genomic DNA, mtDNA-RFLP and electrophoretic karyotyping. Reliable differentiation of yeast to the species level was achieved by PCR-RFLP of HIS4 gene. Numerical analysis of the obtained RAPD-fingerprints and karyotype revealed species-specific clustering corresponding with the technological classification of the strains. Taxonomic position and partial hybrid nature of strains were verified by multiplex PCR. Differentiation among species using the PCR-RFLP of ITS-5·8S and NTS region was shown to be unreliable. Karyotyping and RFLP of mitochondrial DNA evinced small inaccuracies in strain categorization. PCR-RFLP of HIS4 gene and RAPD-PCR of genomic DNA are reliable and suitable methods for fast identification of yeast strains. RAPD-PCR with primer 21 is a fast and reliable method applicable for differentiation of brewing yeasts with only 35% similarity of fingerprint profile between the two main technological groups (ale and lager) of brewing strains. It was proved that PCR-RFLP method of HIS4 gene enables precise discrimination among three technologically important Saccharomyces species. Differentiation of brewing yeast to the strain level can be achieved using the RAPD-PCR technique. © 2016 The

Co-fermentation using Recombinant Saccharomyces cerevisiae Yeast Strains Hyper-secreting Different Cellulases for the Production of Cellulosic Bioethanol.

PubMed

Lee, Cho-Ryong; Sung, Bong Hyun; Lim, Kwang-Mook; Kim, Mi-Jin; Sohn, Min Jeong; Bae, Jung-Hoon; Sohn, Jung-Hoon

2017-06-30

To realize the economical production of ethanol and other bio-based chemicals from lignocellulosic biomass by consolidated bioprocessing (CBP), various cellulases from different sources were tested to improve the level of cellulase secretion in the yeast Saccharomyces cerevisiae by screening an optimal translational fusion partner (TFP) as both a secretion signal and fusion partner. Among them, four indispensable cellulases for cellulose hydrolysis, including Chaetomium thermophilum cellobiohydrolase (CtCBH1), Chrysosporium lucknowense cellobiohydrolase (ClCBH2), Trichoderma reesei endoglucanase (TrEGL2), and Saccharomycopsis fibuligera β-glucosidase (SfBGL1), were identified to be highly secreted in active form in yeast. Despite variability in the enzyme levels produced, each recombinant yeast could secrete approximately 0.6-2.0 g/L of cellulases into the fermentation broth. The synergistic effect of the mixed culture of the four strains expressing the essential cellulases with the insoluble substrate Avicel and several types of cellulosic biomass was demonstrated to be effective. Co-fermentation of these yeast strains produced approximately 14 g/L ethanol from the pre-treated rice straw containing 35 g/L glucan with 3-fold higher productivity than that of wild type yeast using a reduced amount of commercial cellulases. This process will contribute to the cost-effective production of bioenergy such as bioethanol and biochemicals from cellulosic biomass.

Genetic Basis of Variations in Nitrogen Source Utilization in Four Wine Commercial Yeast Strains

PubMed Central

Gutiérrez, Alicia; Beltran, Gemma; Warringer, Jonas; Guillamón, Jose M.

2013-01-01

The capacity of wine yeast to utilize the nitrogen available in grape must directly correlates with the fermentation and growth rates of all wine yeast fermentation stages and is, thus, of critical importance for wine production. Here we precisely quantified the ability of low complexity nitrogen compounds to support fast, efficient and rapidly initiated growth of four commercially important wine strains. Nitrogen substrate abundance in grape must failed to correlate with the rate or the efficiency of nitrogen source utilization, but well predicted lag phase length. Thus, human domestication of yeast for grape must growth has had, at the most, a marginal impact on wine yeast growth rates and efficiencies, but may have left a surprising imprint on the time required to adjust metabolism from non growth to growth. Wine yeast nitrogen source utilization deviated from that of the lab strain experimentation, but also varied between wine strains. Each wine yeast lineage harbored nitrogen source utilization defects that were private to that strain. By a massive hemizygote analysis, we traced the genetic basis of the most glaring of these defects, near inability of the PDM wine strain to utilize methionine, as consequence of mutations in its ARO8, ADE5,7 and VBA3 alleles. We also identified candidate causative mutations in these genes. The methionine defect of PDM is potentially very interesting as the strain can, in some circumstances, overproduce foul tasting H2S, a trait which likely stems from insufficient methionine catabolization. The poor adaptation of wine yeast to the grape must nitrogen environment, and the presence of defects in each lineage, open up wine strain optimization through biotechnological endeavors. PMID:23826223

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. Copyright © 2016 John Wiley & Sons, Ltd.

Quality improvement and geographical indication of cachaça (Brazilian spirit) by using locally selected yeast strains.

PubMed

Barbosa, E A; Souza, M T; Diniz, R H S; Godoy-Santos, F; Faria-Oliveira, F; Correa, L F M; Alvarez, F; Coutrim, M X; Afonso, R J C F; Castro, I M; Brandão, R L

2016-10-01

In order to improve the quality and to create a biological basis for obtainment of the protected denomination of origin (PDO), indigenous yeast were isolated and characterized for use in Salinas city (the Brazilian region of quality cachaça production). Seven thousand and two hundred yeast colonies from 15 Salinas city distilleries were screened based on their fermentative behaviour and the physicochemical composition of cachaça. Molecular polymorphic analyses were performed to characterize these isolates. Two Saccharomyces cerevisiae strains (nos. 678 and 680) showed appropriate characteristics to use in the cachaça production: low levels of acetaldehyde and methanol, and high ethyl lactate/ethyl acetate ratio respectively. They also presented polymorphic characteristics more closely related between themselves even when compared to other strains from Salinas. The application of selected yeast to cachaça production can contribute for the improvement of the quality product as well as be used as a natural marker for PDO. This study suggests that the use of selected yeast strains could contribute to obtain a cachaça similar to those produced traditionally, while getting wide acceptation in the market, yet presenting more homogeneous organoleptic characteristics, and thus contributing to the PDO implementation. © 2016 The Society for Applied Microbiology.

South Brazilian wines: culturable yeasts associated to bottled wines produced in Rio Grande do Sul and Santa Catarina.

PubMed

Ramírez-Castrillón, Mauricio; Mendes, Sandra Denise Camargo; Valente, Patricia

2017-04-01

A comprehensive understanding of the presence and role of yeasts in bottled wines helps to know and control the organoleptic quality of the final product. The South Region of Brazil is an important wine producer, and the state of "Rio Grande do Sul" (RS) accounts for 90% of Brazilian wines. The state of "Santa Catarina" (SC) started the production in 1975, and is currently the fifth Brazilian producer. As there is little information about yeasts present in Brazilian wines, our main objective was to assess the composition of culturable yeasts associated to bottled wines produced in RS and SC, South of Brazil. We sampled 20 RS and 29 SC bottled wines produced between 2003 and 2011, and we isolated culturable yeasts in non-selective agar plates. We identified all isolates by sequencing of the D1/D2 domain of LSU rDNA or ITS1-5.8 S-ITS2 region, and comparison with type strain sequences deposited in GenBank database. Six yeast species were shared in the final product in both regions. We obtained two spoilage yeast profiles: RS with Zygosaccharomyces bailii and Pichia membranifaciens (Dekkera bruxellensis was found only in specific table wines); and SC with Dekkera bruxellensis and Pichia manshurica. Knowledge concerning the different spoilage profiles is important for winemaking practices in both regions.

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. Copyright © 2015 Elsevier Ltd. All rights reserved.

Largely enhanced bioethanol production through the combined use of lignin-modified sugarcane and xylose fermenting yeast strain.

PubMed

Ko, Ja Kyong; Jung, Je Hyeong; Altpeter, Fredy; Kannan, Baskaran; Kim, Ha Eun; Kim, Kyoung Heon; Alper, Hal S; Um, Youngsoon; Lee, Sun-Mi

2018-05-01

The recalcitrant structure of lignocellulosic biomass is a major barrier in efficient biomass-to-ethanol bioconversion processes. The combination of feedstock engineering via modification in the lignin synthesis pathway of sugarcane and co-fermentation of xylose and glucose with a recombinant xylose utilizing yeast strain produced 148% more ethanol compared to that of the wild type biomass and control strain. The lignin reduced biomass led to a substantially increased release of fermentable sugars (glucose and xylose). The engineered yeast strain efficiently co-utilized glucose and xylose for fermentation, elevating ethanol yields. In this study, it was experimentally demonstrated that the combined efforts of engineering both feedstock and microorganisms largely enhances the bioconversion of lignocellulosic feedstock to bioethanol. This strategy will significantly improve the economic feasibility of lignocellulosic biofuels production. Copyright © 2018 Elsevier Ltd. All rights reserved.

Distinct Domestication Trajectories in Top-Fermenting Beer Yeasts and Wine Yeasts.

PubMed

Gonçalves, Margarida; Pontes, Ana; Almeida, Pedro; Barbosa, Raquel; Serra, Marta; Libkind, Diego; Hutzler, Mathias; Gonçalves, Paula; Sampaio, José Paulo

2016-10-24

Beer is one of the oldest alcoholic beverages and is produced by the fermentation of sugars derived from starches present in cereal grains. Contrary to lager beers, made by bottom-fermenting strains of Saccharomyces pastorianus, a hybrid yeast, ale beers are closer to the ancient beer type and are fermented by S. cerevisiae, a top-fermenting yeast. Here, we use population genomics to investigate (1) the closest relatives of top-fermenting beer yeasts; (2) whether top-fermenting yeasts represent an independent domestication event separate from those already described; (3) whether single or multiple beer yeast domestication events can be inferred; and (4) whether top-fermenting yeasts represent non-recombinant or recombinant lineages. Our results revealed that top-fermenting beer yeasts are polyphyletic, with a main clade composed of at least three subgroups, dominantly represented by the German, British, and wheat beer strains. Other beer strains were phylogenetically close to sake, wine, or bread yeasts. We detected genetic signatures of beer yeast domestication by investigating genes previously linked to brewing and using genome-wide scans. We propose that the emergence of the main clade of beer yeasts is related with a domestication event distinct from the previously known cases of wine and sake yeast domestication. The nucleotide diversity of the main beer clade more than doubled that of wine yeasts, which might be a consequence of fundamental differences in the modes of beer and wine yeast domestication. The higher diversity of beer strains could be due to the more intense and different selection regimes associated to brewing. Copyright © 2016 Elsevier Ltd. All rights reserved.

Fermentation Characteristics and Aromatic Profile of Plum Wines Produced with Indigenous Microbiota and Pure Cultures of Selected Yeast.

PubMed

Miljić, Uroš; Puškaš, Vladimir; Vučurović, Vesna; Muzalevski, Ana

2017-06-01

The aim of this study was to assess and compare fermentation characteristics and aromatic profile of plum wines produced with indigenous microbiota and pure cultures of different selected yeast. Experiments were carried out with plum (Prunus domestica L.) varieties of different fruit ripening times (Čačanska rana, Čačanska lepotica, and Požegača). Wine fermentations were conducted by the activity of indigenous microbiota, commercially available Saccharomyces cerevisiae and Saccharomyces bayanus yeast strains and joint activity of Schizosaccharomyces pombe and S. cerevisiae (sequential inoculation). Statistically significant differences in fermentative characteristics and the content of certain volatile compounds were observed as a result of metabolic activity of various indigenous and/or selected yeasts during fermentation of plum pomace. Minimal duration of fermentation (4 to 5 d) and fastest ethanol production rate (from 12.3 to 15.5 g/L/d) were the characteristics of the studied S. cerevisiae strains. Isobutanol, 3-methyl-1-butanol, 1-heptanol, and 1-octanol were the most prevalent higher alcohols in the tested plum wine samples. The predominant ester in plum wines was ethyl acetate, ethyl lactate, amyl acetate, isoamyl acetate, and ethyl palmitate, esters responsible for the floral and fruity olfactory tones, were also present in large amounts. Also, the use of S. cerevisiae strains resulted in the production of plum wines with better sensory characteristics than ones produced with other investigated yeasts. Obtained results are significant since there is limited data on the compounds responsible for the unique flavor of plum wine, as well as on the impact of different yeast starter cultures application on the overall quality of fruit wines. © 2017 Institute of Food Technologists®.

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. Copyright © 2013 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Impact of apple cultivar, ripening stage, fermentation type and yeast strain on phenolic composition of apple ciders.

PubMed

Laaksonen, Oskar; Kuldjärv, Rain; Paalme, Toomas; Virkki, Mira; Yang, Baoru

2017-10-15

Hydroxycinnamic acids and flavonoids in apple juices and ciders were studied using liquid chromatography. Samples were produced from four different Estonian apple cultivars using unripe, ripe and overripe apples, and six different commercial yeasts including Saccharomyces cerevisiae, Saccharomyces bayanus, and Torulaspora delbrueckii strains. Part of the samples was additionally inoculated with malolactic bacteria, Oenococcus oeni. The most notable difference among the samples was the appearance of phloretin in malolactic ciders in comparison to conventional ciders and the juices. Furthermore, the apple cultivars were significantly different in their phenolic contents and compositions. Additionally, ciders and juices made from unripe apples contained more phenolic compounds than the ripe or overripe, but the effect was dependent on cultivar. The commercial yeast strains differed in the release of free HCAs, especially p-coumaric acid, during the yeast fermentation. In ciders inoculated with S. bayanus, the content was higher than in ciders fermented with S. cerevisiae. Copyright © 2017 Elsevier Ltd. All rights reserved.

Direct ethanol production from cassava pulp using a surface-engineered yeast strain co-displaying two amylases, two cellulases, and β-glucosidase.

PubMed

Apiwatanapiwat, Waraporn; Murata, Yoshinori; Kosugi, Akihiko; Yamada, Ryosuke; Kondo, Akihiko; Arai, Takamitsu; Rugthaworn, Prapassorn; Mori, Yutaka

2011-04-01

In order to develop a method for producing fuel ethanol from cassava pulp using cell surface engineering (arming) technology, an arming yeast co-displaying α-amylase (α-AM), glucoamylase, endoglucanase, cellobiohydrase, and β-glucosidase on the surface of the yeast cells was constructed. The novel yeast strain, possessing the activities of all enzymes, was able to produce ethanol directly from soluble starch, barley β-glucan, and acid-treated Avicel. Cassava is a major crop in Southeast Asia and used mainly for starch production. In the starch manufacturing process, large amounts of solid wastes, called cassava pulp, are produced. The major components of cassava pulp are starch (approximately 60%) and cellulose fiber (approximately 30%). We attempted simultaneous saccharification and ethanol fermentation of cassava pulp with this arming yeast. During fermentation, ethanol concentration increased as the starch and cellulose fiber substrates contained in the cassava pulp decreased. The results clearly showed that the arming yeast was able to produce ethanol directly from cassava pulp without addition of any hydrolytic enzymes.

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

2016-09-01

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. © 2016 Cold Spring Harbor Laboratory Press.

Degradation of spent craft brewer's yeast by caprine rumen hyper ammonia-producing bacteria.

PubMed

Harlow, B E; Bryant, R W; Cohen, S D; O'Connell, S P; Flythe, M D

2016-10-01

Spent yeast from craft beers often includes more hops (Humulus lupulus L.) secondary metabolites than traditional recipes. These compounds include α- and β- acids, which are antimicrobial to the rumen hyper ammonia-producing bacteria (HAB) that are major contributors to amino acid degradation. The objective was to determine if the hops acids in spent craft brewer's yeast (CY; ~ 3·5 mg g(-1) hops acids) would protect it from degradation by caprine rumen bacteria and HAB when compared to a baker's yeast (BY; no hops acids). Cell suspensions were prepared by harvesting rumen fluid from fistulated goats, straining and differential centrifugation. The cells were re-suspended in media with BY or CY. After 24 h (39°C), HAB were enumerated and ammonia was measured. Fewer HAB and less ammonia was produced from CY than from BY. Pure culture experiments were conducted with Peptostreptococcus anaerobiusBG1 (caprine HAB). Ammonia production by BG1 from BY was greater than from CY. Ammonia production was greater when exogenous amino acids were included, but similar inhibition was observed in CY treatments. These results indicate that rumen micro-organisms deaminated the amino acids in CY to a lesser degree than BY. Spent brewer's yeast has long been included in ruminant diets as a protein supplement. However, modern craft beers often include more hops (Humulus lupulus L.) than traditional recipes. These compounds include α- and β- acids, which are antimicrobial to the rumen hyper ammonia-producing bacteria (HAB) that are major contributors to amino acid degradation. This study demonstrated that hops acids in spent craft brewer's yeast protected protein from destruction by HABin vitro. These results suggest that the spent yeast from craft breweries, a source of beneficial hops secondary metabolites, could have value as rumen-protected protein. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Biocavity laser spectroscopy of genetically altered yeast cells and isolated yeast mitochondria

NASA Astrophysics Data System (ADS)

Gourley, Paul L.; Hendricks, Judy K.; McDonald, Anthony E.; Copeland, R. Guild; Naviaux, Robert K.; Yaffe, Michael P.

2006-02-01

We report an analysis of 2 yeast cell mutants using biocavity laser spectroscopy. The two yeast strains differed only by the presence or absence of mitochondrial DNA. Strain 104 is a wild-type (ρ +) strain of the baker's yeast, Saccharomyces cerevisiae. Strain 110 was derived from strain 104 by removal of its mitochondrial DNA (mtDNA). Removal of mtDNA causes strain 110 to grow as a "petite" (ρ -), named because it forms small colonies (of fewer cells because it grows more slowly) on agar plates supplemented with a variety of different carbon sources. The absence of mitochondrial DNA results in the complete loss of all the mtDNA-encoded proteins and RNAs, and loss of the pigmented, heme-containing cytochromes a and b. These cells have mitochondria, but the mitochondria lack the normal respiratory chain complexes I, III, IV, and V. Complex II is preserved because its subunits are encoded by genes located in nuclear DNA. The frequency distributions of the peak shifts produced by wild-type and petite cells and mitochondria show striking differences in the symmetry and patterns of the distributions. Wild-type ρ + cells (104) and mitochondria produced nearly symmetric, Gaussian distributions. The ρ - cells (110) and mitochondria showed striking asymmetry and skew that appeared to follow a Poisson distribution.

The development of bactericidal yeast strains by expressing the Pediococcus acidilactici pediocin gene (pedA) in Saccharomyces cerevisiae.

PubMed

Schoeman, H; Vivier, M A; Du Toit, M; Dicks, L M; Pretorius, I S

1999-06-15

The excessive use of sulphur dioxide and other chemical preservatives in wine, beer and other fermented food and beverage products to prevent the growth of unwanted microbes holds various disadvantages for the quality of the end-products and is confronted by mounting consumer resistance. The objective of this study was to investigate the feasibility of controlling spoilage bacteria during yeast-based fermentations by engineering bactericidal strains of Saccharomyces cerevisiae. To test this novel concept, we have successfully expressed a bacteriocin gene in yeast. The pediocin operon of Pediococcus acidilactici PAC1.0 consists of four clustered genes, namely pedA (encoding a 62 amino acid precursor of the PA-1 pediocin), pedB (encoding an immunity factor), pedC (encoding a PA-1 transport protein) and pedD (encoding a protein involved in the transport and processing of PA-1). The pedA gene was inserted into a yeast expression/secretion cassette and introduced as a multicopy episomal plasmid into a laboratory strain (Y294) of S. cerevisiae. Northern blot analysis confirmed that the pedA structural gene in this construct (ADH1P-MFa1S-pedA-ADH1T, designated PED1), was efficiently expressed under the control of the yeast alcohol dehydrogenase I gene promoter (ADH1P) and terminator (ADH1T). Secretion of the PED1-encoded pediocin PA-1 was directed by the yeast mating pheromone alpha-factor's secretion signal (MFa1S). The presence of biologically active antimicrobial peptides produced by the yeast transformants was indicated by agar diffusion assays against sensitive indicator bacteria (e.g. Listeria monocytogenes B73). Protein analysis indicated the secreted heterologous peptide to be approximately 4.6 kDa, which conforms to the expected size. The heterologous peptide was present at relatively low levels in the yeast supernatant but pediocin activity was readily detected when intact yeast colonies were used in sensitive strain overlays. This study could lead to the

Evolutionary engineering of a wine yeast strain revealed a key role of inositol and mannoprotein metabolism during low-temperature fermentation.

PubMed

López-Malo, María; García-Rios, Estéfani; Melgar, Bruno; Sanchez, Monica R; Dunham, Maitreya J; Guillamón, José Manuel

2015-07-22

Wine produced at low temperature is often considered to improve sensory qualities. However, there are certain drawbacks to low temperature fermentations: e.g. low growth rate, long lag phase, and sluggish or stuck fermentations. Selection and development of new Saccharomyces cerevisiae strains well adapted at low temperature is interesting for future biotechnological applications. This study aimed to select and develop wine yeast strains that well adapt to ferment at low temperature through evolutionary engineering, and to decipher the process underlying the obtained phenotypes. We used a pool of 27 commercial yeast strains and set up batch serial dilution experiments to mimic wine fermentation conditions at 12 °C. Evolutionary engineering was accomplished by using the natural yeast mutation rate and mutagenesis procedures. One strain (P5) outcompeted the others under both experimental conditions and was able to impose after 200 generations. The evolved strains showed improved growth and low-temperature fermentation performance compared to the ancestral strain. This improvement was acquired only under inositol limitation. The transcriptomic comparison between the evolved and parental strains showed the greatest up-regulation in four mannoprotein coding genes, which belong to the DAN/TIR family (DAN1, TIR1, TIR4 and TIR3). Genome sequencing of the evolved strain revealed the presence of a SNP in the GAA1 gene and the construction of a site-directed mutant (GAA1 (Thr108)) in a derivative haploid of the ancestral strain resulted in improved fermentation performance. GAA1 encodes a GPI transamidase complex subunit that adds GPI, which is required for inositol synthesis, to newly synthesized proteins, including mannoproteins. In this study we demonstrate the importance of inositol and mannoproteins in yeast adaptation at low temperature and the central role of the GAA1 gene by linking both metabolisms.

The effect of Maillard reaction products and yeast strain on the synthesis of key higher alcohols and esters in beer fermentations.

PubMed

Dack, Rachael E; Black, Gary W; Koutsidis, Georgios; Usher, St John

2017-10-01

The effect of Maillard reaction products (MRPs), formed during the production of dark malts, on the synthesis of higher alcohols and esters in beer fermentations was investigated by headspace solid-phase microextraction GC-MS. Higher alcohol levels were significantly (p<0.05) higher in dark malt fermentations, while the synthesis of esters was inhibited, due to possible suppression of enzyme activity and/or gene expression linked to ester synthesis. Yeast strain also affected flavour synthesis with Saccharomyces cerevisiae strain A01 producing considerably lower levels of higher alcohols and esters than S288c and L04. S288c produced approximately double the higher alcohol levels and around twenty times more esters compared to L04. Further investigations into malt type-yeast strain interactions in relation to flavour development are required to gain better understanding of flavour synthesis that could assist in the development of new products and reduce R&D costs for the industry. Copyright © 2017 Elsevier Ltd. All rights reserved.

Isolation of a high malic and low acetic acid-producing sake yeast Saccharomyces cerevisiae strain screened from respiratory inhibitor 2,4-dinitrophenol (DNP)-resistant strains.

PubMed

Kosugi, Shingo; Kiyoshi, Keiji; Oba, Takahiro; Kusumoto, Kenichi; Kadokura, Toshimori; Nakazato, Atsumi; Nakayama, Shunichi

2014-01-01

We isolated 2,4-dinitrophenol (DNP)-resistant sake yeast strains by UV mutagenesis. Among the DNP-resistant mutants, we focused on strains exhibiting high malic acid and low acetic acid production. The improved organic acid composition is unlikely to be under the control of enzyme activities related to malic and acetic acid synthesis pathways. Instead, low mitochondrial activity was observed in DNP-resistant mutants, indicating that the excess pyruvic acid generated during glycolysis is not metabolized in the mitochondria but converted to malic acid in the cytosol. In addition, the NADH/NAD(+) ratio of the DNP-resistant strains was higher than that of the parental strain K901. These results suggest that the increased NADH/NAD(+) ratio together with the low mitochondrial activity alter the organic acid composition because malic acid synthesis requires NADH, while acetic acid uses NAD(+). Copyright © 2013 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Effect of Agave tequilana age, cultivation field location and yeast strain on tequila fermentation process.

PubMed

Pinal, L; Cornejo, E; Arellano, M; Herrera, E; Nuñez, L; Arrizon, J; Gschaedler, A

2009-05-01

The effect of yeast strain, the agave age and the cultivation field location of agave were evaluated using kinetic parameters and volatile compound production in the tequila fermentation process. Fermentations were carried out with Agave juice obtained from two cultivation fields (CF1 and CF2), as well as two ages (4 and 8 years) and two Saccharomyces cerevisiae yeast strains (GU3 and AR5) isolated from tequila fermentation must. Sugar consumption and ethanol production varied as a function of cultivation field and agave age. The production of ethyl acetate, 1-propanol, isobutanol and amyl alcohols were influenced in varying degrees by yeast strain, agave age and cultivation field. Methanol production was only affected by the agave age and 2-phenylethanol was influenced only by yeast strain. This work showed that the use of younger Agave tequilana for tequila fermentation resulted in differences in sugar consumption, ethanol and volatile compounds production at the end of fermentation, which could affect the sensory quality of the final product.

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.

Relationship of trehalose accumulation with ethanol fermentation in industrial Saccharomyces cerevisiae yeast strains.

PubMed

Wang, Pin-Mei; Zheng, Dao-Qiong; Chi, Xiao-Qin; Li, Ou; Qian, Chao-Dong; Liu, Tian-Zhe; Zhang, Xiao-Yang; Du, Feng-Guang; Sun, Pei-Yong; Qu, Ai-Min; Wu, Xue-Chang

2014-01-01

The protective effect and the mechanisms of trehalose accumulation in industrial Saccharomyces cerevisiae strains were investigated during ethanol fermentation. The engineered strains with more intercellular trehalose achieved significantly higher fermentation rates and ethanol yields than their wild strain ZS during very high gravity (VHG) fermentation, while their performances were not different during regular fermentation. The VHG fermentation performances of these strains were consistent with their growth capacity under osmotic stress and ethanol stress, the key stress factors during VHG fermentation. These results suggest that trehalose accumulation is more important for VHG fermentation of industrial yeast strains than regular one. The differences in membrane integrity and antioxidative capacity of these strains indicated the possible mechanisms of trehalose as a protectant under VHG condition. Therefore, trehalose metabolic engineering may be a useful strategy for improving the VHG fermentation performance of industrial yeast strains. Copyright © 2013 Elsevier Ltd. All rights reserved.

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.

Selection of Yeast Strains for Tequila Fermentation Based on Growth Dynamics in Combined Fructose and Ethanol Media.

PubMed

Aldrete-Tapia, J A; Miranda-Castilleja, D E; Arvizu-Medrano, S M; Hernández-Iturriaga, M

2018-02-01

The high concentration of fructose in agave juice has been associated with reduced ethanol tolerance of commercial yeasts used for tequila production and low fermentation yields. The selection of autochthonous strains, which are better adapted to agave juice, could improve the process. In this study, a 2-step selection process of yeasts isolated from spontaneous fermentations for tequila production was carried out based on analysis of the growth dynamics in combined conditions of high fructose and ethanol. First, yeast isolates (605) were screened to identify strains tolerant to high fructose (20%) and to ethanol (10%), yielding 89 isolates able to grow in both conditions. From the 89 isolates, the growth curves under 8 treatments of combined fructose (from 20% to 5%) and ethanol (from 0% to 10%) were obtained, and the kinetic parameters were analyzed with principal component analysis and k-means clustering. The resulting yeast strain groups corresponded to the fast, medium and slow growers. A second clustering of only the fast growers led to the selection of 3 Saccharomyces strains (199, 230, 231) that were able to grow rapidly in 4 out of the 8 conditions evaluated. This methodology differentiated strains phenotypically and could be further used for strain selection in other processes. A method to select yeast strains for fermentation taking into account the natural differences of yeast isolates. This methodology is based on the cell exposition to combinations of sugar and ethanol, which are the most important stress factors in fermentation. This strategy will help to identify the most tolerant strain that could improve ethanol yield and reduce fermentation time. © 2018 Institute of Food Technologists®.

Genome Sequence of the Yeast Clavispora lusitaniae Type Strain CBS 6936

PubMed Central

Klopp, Christophe; Biteau, Nicolas; Fitton-Ouhabi, Valérie; Dementhon, Karine; Accoceberry, Isabelle; Sherman, David J.; Noël, Thierry

2017-01-01

ABSTRACT Clavispora lusitaniae, an environmental saprophytic yeast belonging to the CTG clade of Candida, can behave occasionally as an opportunistic pathogen in humans. We report here the genome sequence of the type strain CBS 6936. Comparison with sequences of strain ATCC 42720 indicates conservation of chromosomal structure but significant nucleotide divergence. PMID:28774979

Selection of non-Saccharomyces yeast strains for reducing alcohol levels in wine by sugar respiration.

PubMed

Quirós, Manuel; Rojas, Virginia; Gonzalez, Ramon; Morales, Pilar

2014-07-02

Respiration of sugars by non-Saccharomyces yeasts has been recently proposed for lowering alcohol levels in wine. Development of industrial fermentation processes based on such an approach requires, amongst other steps, the identification of yeast strains which are able to grow and respire under the relatively harsh conditions found in grape must. This work describes the characterization of a collection of non-Saccharomyces yeast strains in order to identify candidate yeast strains for this specific application. It involved the estimation of respiratory quotient (RQ) values under aerated conditions, at low pH and high sugar concentrations, calculation of yields of ethanol and other relevant metabolites, and characterization of growth responses to the main stress factors found during the first stages of alcoholic fermentation. Physiological features of some strains of Metschnikowia pulcherrima or two species of Kluyveromyces, suggest they are suitable for lowering ethanol yields by respiration. The unsuitability of Saccharomyces cerevisiae strains for this purpose was not due to ethanol yields (under aerated conditions they are low enough for a significant reduction in final ethanol content), but to the high acetic acid yields under these growth conditions. According to results from controlled aeration fermentations with one strain of M. pulcherrima, design of an aeration regime allowing for lowering ethanol yields though preserving grape must components from excessive oxidation, would be conceivable. Copyright © 2014. Published by Elsevier B.V.

Treatment of diesel- and kerosene-contaminated water by B. subtilis SPB1 biosurfactant-producing strain.

PubMed

Mnif, Ines; Ellouze-Chaabouni, Semia; Ayedi, Younes; Ghribi, Dhouha

2014-08-01

This study investigated the efficiency of hydrocarbon utilization by B. subtilis SPB1, a biosurfactant-producing strain. Microbial growth, biosurfactant production, and hydrocarbon biodegradation were studied in a liquid mineral medium, supplemented with 2% hydrocarbons in both the absence and in the presence of 0.1% yeast extract. Preliminary studies showed that maximum growth was registered with a 2% hydrocarbon solution. Results showed that the addition of yeast extract greatly stimulated microbial growth and thus induced biosurfactant production. Furthermore, biodegradation efficiencies were higher in the presence of yeast extract. Kerosene fuel was more recalcitrant to biodegradation than diesel oil. This study's findings suggest that the addition of an organic nitrogen source stimulates tension-active agents' production, which emulsifies hydrophobic compounds and enhances their biodegradation and microbial growth.

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. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Differential Proteome Analysis of a Flor Yeast Strain under Biofilm Formation

PubMed Central

Moreno-García, Jaime; Mauricio, Juan Carlos; Moreno, Juan; García-Martínez, Teresa

2017-01-01

Several Saccharomyces cerevisiae strains (flor yeasts) form a biofilm (flor velum) on the surface of Sherry wines after fermentation, when glucose is depleted. This flor velum is fundamental to biological aging of these particular wines. In this study, we identify abundant proteins in the formation of the biofilm of an industrial flor yeast strain. A database search to enrich flor yeast “biological process” and “cellular component” according to Gene Ontology Terminology (GO Terms) and, “pathways” was carried out. The most abundant proteins detected were largely involved in respiration, translation, stress damage prevention and repair, amino acid metabolism (glycine, isoleucine, leucine and arginine), glycolysis/gluconeogenesis and biosynthesis of vitamin B9 (folate). These proteins were located in cellular components as in the peroxisome, mitochondria, vacuole, cell wall and extracellular region; being these two last directly related with the flor formation. Proteins like Bgl2p, Gcv3p, Hyp2p, Mdh1p, Suc2p and Ygp1p were quantified in very high levels. This study reveals some expected processes and provides new and important information for the design of conditions and genetic constructions of flor yeasts for improving the cellular survival and, thus, to optimize biological aging of Sherry wine production. PMID:28350350

Differential Proteome Analysis of a Flor Yeast Strain under Biofilm Formation.

PubMed

Moreno-García, Jaime; Mauricio, Juan Carlos; Moreno, Juan; García-Martínez, Teresa

2017-03-28

Several Saccharomyces cerevisiae strains (flor yeasts) form a biofilm (flor velum) on the surface of Sherry wines after fermentation, when glucose is depleted. This flor velum is fundamental to biological aging of these particular wines. In this study, we identify abundant proteins in the formation of the biofilm of an industrial flor yeast strain. A database search to enrich flor yeast "biological process" and "cellular component" according to Gene Ontology Terminology (GO Terms) and, "pathways" was carried out. The most abundant proteins detected were largely involved in respiration, translation, stress damage prevention and repair, amino acid metabolism (glycine, isoleucine, leucine and arginine), glycolysis/gluconeogenesis and biosynthesis of vitamin B9 (folate). These proteins were located in cellular components as in the peroxisome, mitochondria, vacuole, cell wall and extracellular region; being these two last directly related with the flor formation. Proteins like Bgl2p, Gcv3p, Hyp2p, Mdh1p, Suc2p and Ygp1p were quantified in very high levels. This study reveals some expected processes and provides new and important information for the design of conditions and genetic constructions of flor yeasts for improving the cellular survival and, thus, to optimize biological aging of Sherry wine production.

Molecular and physiological characteristics of a grape yeast strain containing atypical genetic material.

PubMed

Cappello, M S; Poltronieri, P; Blaiotta, G; Zacheo, G

2010-11-15

The knowledge about wine yeasts remains largely dominated by the extensive studies on Saccharomyces (S.) cerevisiae. Molecular methods, allowing discrimination of both species and strains in winemaking, can profitably be applied for characterization of the microflora occurring in winemaking and for monitoring the fermentation process. Recently, some novel yeast isolates have been described as hybrid between S. cerevisiae and Saccharomyces species, leaving the Saccharomyces strains containing non-Saccharomyces hybrids essentially unexplored. In this study, we have analyzed a yeast strain isolated from "Primitivo" grape (http://www.ispa.cnr.it/index.php?page=collezioni&lang=en accession number 12998) and we found that, in addition to the S. cerevisiae genome, it has acquired genetic material from a non-Saccharomyces species. The study was focused on the analysis of chromosomal and mitochondrial gene sequences (ITS and 26S rRNA, SSU and COXII, ACTIN-1 and TEF), 2D-PAGE mitochondrial proteins, and spore viability. The results allowed us to formulate the hypothesis that in the MSH199 isolate a DNA containing an rDNA sequence from Hanseniaspora vineae, a non-Saccharomyces yeast, was incorporated through homologous recombination in the grape environment where yeast species are propagated. Moreover, physiological characterization showed that the MSH199 isolate possesses high technological quality traits (fermentation performance) and glycerol production, resistance to ethanol, SO₂ and temperature) useful for industrial application. Copyright © 2010 Elsevier B.V. All rights reserved.

Genome Sequence of the Yeast Clavispora lusitaniae Type Strain CBS 6936.

PubMed

Durrens, Pascal; Klopp, Christophe; Biteau, Nicolas; Fitton-Ouhabi, Valérie; Dementhon, Karine; Accoceberry, Isabelle; Sherman, David J; Noël, Thierry

2017-08-03

Clavispora lusitaniae , an environmental saprophytic yeast belonging to the CTG clade of Candida , can behave occasionally as an opportunistic pathogen in humans. We report here the genome sequence of the type strain CBS 6936. Comparison with sequences of strain ATCC 42720 indicates conservation of chromosomal structure but significant nucleotide divergence. Copyright © 2017 Durrens et al.

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. Copyright © 2011 Elsevier B.V. All rights reserved.

Raman spectroscopy and chemometrics for identification and strain discrimination of the wine spoilage yeasts Saccharomyces cerevisiae, Zygosaccharomyces bailii, and Brettanomyces bruxellensis.

PubMed

Rodriguez, Susan B; Thornton, Mark A; Thornton, Roy J

2013-10-01

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%.

Genetic characterization and construction of an auxotrophic strain of Saccharomyces cerevisiae JP1, a Brazilian industrial yeast strain for bioethanol production.

PubMed

Reis, Viviane Castelo Branco; Nicola, André Moraes; de Souza Oliveira Neto, Osmar; Batista, Vinícius Daniel Ferreira; de Moraes, Lidia Maria Pepe; Torres, Fernando Araripe Gonçalves

2012-11-01

Used for millennia to produce beverages and food, Saccharomyces cerevisiae also became a workhorse in the production of biofuels, most notably bioethanol. Yeast strains have acquired distinct characteristics that are the result of evolutionary adaptation to the stresses of industrial ethanol production. JP1 is a dominant industrial S. cerevisiae strain isolated from a sugarcane mill and is becoming increasingly popular for bioethanol production in Brazil. In this work, we carried out the genetic characterization of this strain and developed a set of tools to permit its genetic manipulation. Using flow cytometry, mating type, and sporulation analysis, we verified that JP1 is diploid and homothallic. Vectors with dominant selective markers for G418, hygromycin B, zeocin, and ρ-fluoro-DL-phenylalanine were used to successfully transform JP1 cells. Also, an auxotrophic ura3 mutant strain of JP1 was created by gene disruption using integration cassettes with dominant markers flanked by loxP sites. Marker excision was accomplished by the Cre/loxP system. The resulting auxotrophic strain was successfully transformed with an episomal vector that allowed green fluorescent protein expression.

Influence of yeast strain, priming solution and temperature on beer bottle conditioning.

PubMed

Marconi, Ombretta; Rossi, Serena; Galgano, Fernanda; Sileoni, Valeria; Perretti, Giuseppe

2016-09-01

Recently, there has been a significant increase in the number of microbreweries. Usually, craft beers are bottle conditioned; however, few studies have investigated beer refermentation. One of the objectives of this study was to evaluate the impacts of different experimental conditions, specifically yeast strain, priming solution and temperature, on the standard quality attributes, the volatile compounds and the sensory profile of the bottle-conditioned beer. The other aim was to monitor the evolution of volatile compounds and amino acids consumption throughout the refermentation process to check if it is possible to reduce the time necessary for bottle conditioning. The results indicate that the volatile profile was mainly influenced by the strain of yeast, and this may have obscured the possible impacts of the other parameters. Our results also confirm that the two yeast strains showed different metabolic activity, particularly with respect to esters production. Moreover, we found the Safbrew S-33® strain when primed with Siromix® and refermented at 30 °C yielded the fastest formation of higher alcohols while maintaining low production of off-flavours. These results suggest a formulation that may reduce the time needed for bottle conditioning without affecting the quality of the final beer which may simultaneously improve efficiency and economic profits. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Freeze-drying of yeast cultures.

PubMed

Bond, Chris

2007-01-01

A method is described that allows yeast species to be stored using a variation on the standard freeze-drying method, which employs evaporative cooling in a two-stage process. Yeast cultures are placed in glass ampoules after having been mixed with a lyoprotectant. Primary drying is carried out using a centrifuge head connected to a standard freeze-dryer. Once the centrifuge head is running, air is removed and evaporated liquid is captured in the freeze-dryer. Centrifugation continues for 15 min and primary drying for a further 3 h. The ampoules are constricted using a glass blowing torch. They are then placed on the freeze-dryer manifold for secondary drying under vacuum overnight, using phosphorus pentoxide as a desiccant. The ampoules are sealed and removed from the manifold by melting the constricted section. Although the process causes an initial large drop in viability, further losses after storage are minimal. Yeast strains have remained viable for more than 30 yr when stored using this method and sufficient cells are recovered to produce new working stocks. Although survival rates are strain specific, nearly all National Collection of Yeast Cultures strains covering most yeast genera, have been successfully stored with little or no detectable change in strain characteristics.

Alcoholic Fermentation of d-Xylose by Yeasts

PubMed Central

Toivola, Ansa; Yarrow, David; van den Bosch, Eduard; van Dijken, Johannes P.; Scheffers, W. Alexander

1984-01-01

Type strains of 200 species of yeasts able to ferment glucose and grow on xylose were screened for fermentation of d-xylose. In most of the strains tested, ethanol production was negligible. Nineteen were found to produce between 0.1 and 1.0 g of ethanol per liter. Strains of the following species produce more than 1 g of ethanol per liter in the fermentation test with 2% xylose: Brettanomyces naardenensis, Candida shehatae, Candida tenuis, Pachysolen tannophilus, Pichia segobiensis, and Pichia stipitis. Subsequent screening of these yeasts for their capacity to ferment d-cellobiose revealed that only Candida tenuis CBS 4435 was a good fermenter of both xylose and cellobiose under the test conditions used. PMID:16346558

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

The impact of different ale brewer's yeast strains on the proteome of immature beer.

PubMed

Berner, Torben Sune; Jacobsen, Susanne; Arneborg, Nils

2013-09-30

It is well known that brewer's yeast affects the taste and aroma of beer. However, the influence of brewer's yeast on the protein composition of beer is currently unknown. In this study, changes of the proteome of immature beer, i.e. beer that has not been matured after fermentation, by ale brewer's yeast strains with different abilities to degrade fermentable sugars were investigated. Beers were fermented from standard hopped wort (13° Plato) using two ale brewer's yeast (Saccharomyces cerevisiae) strains with different attenuation degrees. Both immature beers had the same alcohol and protein concentrations. Immature beer and unfermented wort proteins were analysed by 2-DE and compared in order to determine protein changes arising from fermentation. Distinct protein spots in the beer and wort proteomes were identified using Matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and MS/MS and revealed common beer proteins, such as lipid transfer proteins (LTP1 and LTP2), protein Z and amylase-protease inhibitors. During fermentation, two protein spots, corresponding to LTP2, disappeared, while three protein spots were exclusively found in beer. These three proteins, all derived from yeast, were identified as cell wall associated proteins, that is Exg1 (an exo-β-1,3-glucanase), Bgl2 (an endo-β-1,2-glucanase), and Uth1 (a cell wall biogenesis protein). Yeast strain dependent changes in the immature beer proteome were identified, i.e. Bgl2 was present in beer brewed with KVL011, while lacking in WLP001 beer.

Introducing a new breed of wine yeast: interspecific hybridisation between a commercial Saccharomyces cerevisiae wine yeast and Saccharomyces mikatae.

PubMed

Bellon, Jennifer R; Schmid, Frank; Capone, Dimitra L; Dunn, Barbara L; Chambers, Paul J

2013-01-01

Interspecific hybrids are commonplace in agriculture and horticulture; bread wheat and grapefruit are but two examples. The benefits derived from interspecific hybridisation include the potential of generating advantageous transgressive phenotypes. This paper describes the generation of a new breed of wine yeast by interspecific hybridisation between a commercial Saccharomyces cerevisiae wine yeast strain and Saccharomyces mikatae, a species hitherto not associated with industrial fermentation environs. While commercially available wine yeast strains provide consistent and reliable fermentations, wines produced using single inocula are thought to lack the sensory complexity and rounded palate structure obtained from spontaneous fermentations. In contrast, interspecific yeast hybrids have the potential to deliver increased complexity to wine sensory properties and alternative wine styles through the formation of novel, and wider ranging, yeast volatile fermentation metabolite profiles, whilst maintaining the robustness of the wine yeast parent. Screening of newly generated hybrids from a cross between a S. cerevisiae wine yeast and S. mikatae (closely-related but ecologically distant members of the Saccharomyces sensu stricto clade), has identified progeny with robust fermentation properties and winemaking potential. Chemical analysis showed that, relative to the S. cerevisiae wine yeast parent, hybrids produced wines with different concentrations of volatile metabolites that are known to contribute to wine flavour and aroma, including flavour compounds associated with non-Saccharomyces species. The new S. cerevisiae x S. mikatae hybrids have the potential to produce complex wines akin to products of spontaneous fermentation while giving winemakers the safeguard of an inoculated ferment.

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.

Newly generated interspecific wine yeast hybrids introduce flavour and aroma diversity to wines.

PubMed

Bellon, Jennifer R; Eglinton, Jeffery M; Siebert, Tracey E; Pollnitz, Alan P; Rose, Louisa; de Barros Lopes, Miguel; Chambers, Paul J

2011-08-01

Increasingly, winemakers are looking for ways to introduce aroma and flavour diversity to their wines as a means of improving style and increasing product differentiation. While currently available commercial yeast strains produce consistently sound fermentations, there are indications that sensory complexity and improved palate structure are obtained when other species of yeast are active during fermentation. In this study, we explore a strategy to increase the impact of non-Saccharomyces cerevisiae inputs without the risks associated with spontaneous fermentations, through generating interspecific hybrids between a S. cerevisiae wine strain and a second species. For our experiments, we used rare mating to produce hybrids between S. cerevisiae and other closely related yeast of the Saccharomyces sensu stricto complex. These hybrid yeast strains display desirable properties of both parents and produce wines with concentrations of aromatic fermentation products that are different to what is found in wine made using the commercial wine yeast parent. Our results demonstrate, for the first time, that the introduction of genetic material from a non-S. cerevisiae parent into a wine yeast background can impact favourably on the wine flavour and aroma profile of a commercial S. cerevisiae wine yeast.

Biodegradation and detoxification of aliphatic and aromatic hydrocarbons by new yeast strains.

PubMed

Hashem, Mohamed; Alamri, Saad A; Al-Zomyh, Sharefah S A A; Alrumman, Sulaiman A

2018-04-30

Seeking new efficient hydrocarbon-degrading yeast stains was the main goal of this study. Because microorganisms are greatly affected by the environmental factors, the biodegradation potentiality of the microorganisms varies from climatic area to another. This induces research to develop and optimize the endemic organisms in bioremediation technology. In this study, 67 yeast strains were tested for their growth potentiality on both aliphatic and aromatic hydrocarbons. The most efficient six strains were identified using sequence analysis of the variable D1/D2 domain of the large subunit 26S ribosomal DNA. The identity of these strains was confirmed as Yamadazyma mexicana KKUY-0160, Rhodotorula taiwanensis KKUY-0162, Pichia kluyveri KKUY-0163, Rhodotorula ingeniosa KKUY-0170, Candida pseudointermedia KKUY-0192 and Meyerozyma guilliermondii KKUY-0214. These species are approved for their ability to degrade both aliphatic and aromatic hydrocarbons for the first time in this study. Although, all of them were able to utilize and grow on both hydrocarbons, Rhodotorula taiwanensis KKUY-0162 emerged as the best degrader of octane, and Rhodotorula ingeniosa KKUY-170 was the best degrader of pyrene. GC-MS analysis approved the presence of many chemical compounds that could be transitional or secondary metabolites during the utilization of the hydrocarbons. Our results recommend the application of these yeast species on large scale to approve their efficiency in bioremediation of oil-contamination of the environment. Using these yeasts, either individually or in consortia, could offer a practical solution for aquatic or soil contamination with the crude oil and its derivatives in situ. Copyright © 2017 Elsevier Inc. All rights reserved.

Population analysis of biofilm yeasts during fino sherry wine aging in the Montilla-Moriles D.O. region.

PubMed

Marin-Menguiano, Miriam; Romero-Sanchez, Sandra; Barrales, Ramón R; Ibeas, Jose I

2017-03-06

Fino is the most popular sherry wine produced in southern Spain. Fino is matured by biological aging under a yeast biofilm constituted of Saccharomyces cerevisiae yeasts. Although different S. cerevisiae strains can be identified in such biofilms, their diversity and contribution to wine character have been poorly studied. In this work, we analyse the flor yeast population in five different wineries from the Montilla-Moriles D.O. (Denominación de Origen) in southern Spain. Yeasts present in wines of different ages were identified using two different culture-dependent molecular techniques. From 2000 individual yeast isolates, five different strains were identified with one of them dominating in four out of the five wineries analysed, and representing 76% of all the yeast isolates collected. Surprisingly, this strain is similar to the predominant strain isolated twenty years ago in Jerez D.O. wines, suggesting that this yeast is particularly able to adapt to such a stressful environment. Fino wine produced with pure cultures of three of the isolated strains resulted in different levels of acetaldehyde. Because acetaldehyde levels are a distinctive characteristic of fino wines and an indicator of fino aging, the use of molecular techniques for yeast identification and management of yeast populations may be of interest for fino wine producers looking to control one of the main features of this wine. Copyright © 2016 Elsevier B.V. All rights reserved.

Influence of the yeast strain on the changes of the amino acids, peptides and proteins during sparkling wine production by the traditional method.

PubMed

Martínez-Rodríguez, A J; Carrascosa, A V; Martín-Alvarez, P J; Moreno-Arribas, V; Polo, M C

2002-12-01

The influence of five yeast strains on the nitrogen fractions, amino acids, peptides and proteins, during 12 months of aging of sparkling wines produced by the traditional or Champenoise method, was studied. High-performance liquid chromatography (HPLC) techniques were used for analysis of the amino acid and peptide fractions. Proteins plus polypeptides were determined by the colorimetric Bradford method. Four main stages were detected in the aging of wines with yeast. In the first stage, a second fermentation took place; amino acids and proteins plus polypeptides diminished, and peptides were liberated. In the second stage, there was a release of amino acids and proteins, and peptides were degraded. In the third stage, the release of proteins and peptides predominated. In the fourth stage, the amino acid concentration diminished. The yeast strain used influenced the content of free amino acids and peptides and the aging time in all the nitrogen fractions.

Differing effects of 2 active dried yeast (Saccharomyces cerevisiae) strains on ruminal acidosis and methane production in nonlactating dairy cows.

PubMed

Chung, Y-H; Walker, N D; McGinn, S M; Beauchemin, K A

2011-05-01

Fifteen ruminally cannulated, nonlactating Holstein cows were used to measure the effects of 2 strains of Saccharomyces cerevisiae, fed as active dried yeasts, on ruminal pH and fermentation and enteric methane (CH(4)) emissions. Nonlactating cows were blocked by total duration (h) that their ruminal pH was below 5.8 during a 6-d pre-experimental period. Within each block, cows were randomly assigned to control (no yeast), yeast strain 1 (Levucell SC), or yeast strain 2 (a novel strain selected for enhanced in vitro fiber degradation), with both strains (Lallemand Animal Nutrition, Montréal, QC, Canada) providing 1 × 10(10) cfu/head per day. Cows were fed once daily a total mixed ration consisting of a 50:50 forage to concentrate ratio (dry matter basis). The yeast strains were dosed via the rumen cannula daily at the time of feeding. During the 35-d experiment, ruminal pH was measured continuously for 7 d (d 22 to 28) by using an indwelling system, and CH(4) gas was measured for 4 d (d 32 to 35) using the sulfur hexafluoride tracer gas technique (with halters and yokes). Rumen contents were sampled on 2 d (d 22 and 26) at 0, 3, and 6h after feeding. Dry matter intake, body weight, and apparent total-tract digestibility of nutrients were not affected by yeast feeding. Strain 2 decreased the average daily minimum (5.35 vs. 5.65 or 5.66), mean (5.98 vs. 6.24 or 6.34), and maximum ruminal pH (6.71 vs. 6.86 or 6.86), and prolonged the time that ruminal pH was below 5.8 (7.5 vs. 3.3 or 1.0 h/d) compared with the control or strain 1, respectively. The molar percentage of acetate was lower and that of propionate was greater in the ruminal fluid of cows receiving strain 2 compared with cows receiving no yeast or strain 1. Enteric CH(4) production adjusted for intake of dry matter or gross energy, however, did not differ between either yeast strain compared with the control but it tended to be reduced by 10% when strain 2 was compared with strain 1. The study shows that

Large-Scale Selection and Breeding To Generate Industrial Yeasts with Superior Aroma Production

PubMed Central

Steensels, Jan; Meersman, Esther; Snoek, Tim; Saels, Veerle

2014-01-01

The concentrations and relative ratios of various aroma compounds produced by fermenting yeast cells are essential for the sensory quality of many fermented foods, including beer, bread, wine, and sake. Since the production of these aroma-active compounds varies highly among different yeast strains, careful selection of variants with optimal aromatic profiles is of crucial importance for a high-quality end product. This study evaluates the production of different aroma-active compounds in 301 different Saccharomyces cerevisiae, Saccharomyces paradoxus, and Saccharomyces pastorianus yeast strains. Our results show that the production of key aroma compounds like isoamyl acetate and ethyl acetate varies by an order of magnitude between natural yeasts, with the concentrations of some compounds showing significant positive correlation, whereas others vary independently. Targeted hybridization of some of the best aroma-producing strains yielded 46 intraspecific hybrids, of which some show a distinct heterosis (hybrid vigor) effect and produce up to 45% more isoamyl acetate than the best parental strains while retaining their overall fermentation performance. Together, our results demonstrate the potential of large-scale outbreeding to obtain superior industrial yeasts that are directly applicable for commercial use. PMID:25192996

The hydrolytic enzymes produced by fungi strains isolated from the sand and soil of recreational areas

PubMed

Kurnatowski, Piotr; Wójcik, Anna; Błaszkowska, Joanna; Góralska, Katarzyna

2016-10-01

The pathogenicity of fungi depends on, inter alia, the secretion of hydrolytic enzymes. The aim of this study was to determine the enzymatic activity of yeasts and yeast-like fungi isolated from children’s recreation areas, and compare the results with literature data of strains obtained from patients with mycoses. The enzymatic activity of 96 strains was assessed using an API ZYM kit (bioMerieux, France) and their biotypes were established. The fungal species were found to produce from 16 to 19 hydrolases: the most active were: leucine arylamidase (e5), acid phosphatase (e10), alkaline phosphatase (e1), naphthol-AS-BI-phosphohydrolase (e11), esterase – C4 (e2), β-galac - tosidase (e13) and β-glucosidase (e16). In addition, 13 biotypes characteristic of particular species of fungi were defined. Most strains could be categorized as biotypes C2 – 39.5% and A – 26%. The examined fungal strains isolated from recreational areas have selected biochemical characteristics i.e. production of hydrolases, which demonstrate their pathogenicity. They produce a number of enzymes which are also present in strains isolated from patients with mycoses, including: leucine arylamidase (e5), acid phosphatase (e10), naphthol-AS-BI-phosphohydrolase (e11) and alkaline phosphatase (e1). The biotypes identified in the course of this study (A, B3, B4, C1, C6 and D3) have been also reported in cases of fungal infection. Therefore, the fungi present in the sand and soil of recreational have pathogenic properties and are possible factors of fungal infection among children.

Isolation and characterization of a novel electricity-producing yeast, Candida sp. IR11.

PubMed

Lee, Yun-Yeong; Kim, Tae Gwan; Cho, Kyung-Suk

2015-09-01

A novel iron-reducing yeast, Candida sp. IR11, was isolated from an anodic biofilm in a MFC reactor fed glucose as a feedstock. 200-250 mV of voltage was produced in the air-cathode MFC inoculated with a pure culture of the strain IR11 where glucose was supplied as a feedstock. When the strain IR11 was inoculated into a conventional MFC treating rejected wastewater from an upflow anaerobic sludge blanket, maximum power density and coulombic efficiency were enhanced from 15.2 ± 0.36 to 20.6 ± 1.52 mW m(-2) and from 14.4 ± 0.45% to 21.9 ± 0.71%, respectively. In addition, the inoculation with IR11 improved COD removal from 79.1 ± 1.53% to 91.3 ± 5.29%. The quantitative PCR results showed that the strain IR11 successfully attached the anodic biofilm of the MFC reactors. These results indicate that Candida sp. IR11 is a promising biocatalyst for the enhancement of MFC performance. Copyright © 2015 Elsevier Ltd. All rights reserved.

Yeast population dynamics of industrial fuel-ethanol fermentation process assessed by PCR-fingerprinting.

PubMed

da Silva-Filho, Eurípedes Alves; Brito dos Santos, Scheila Karina; Resende, Alecsandra do Monte; de Morais, José Otamar Falcão; de Morais, Marcos Antonio; Ardaillon Simões, Diogo

2005-07-01

Yeast population used in industrial production of fuel-ethanol may vary according to the plant process condition and to the environmental stresses imposed to yeast cells. Therefore, yeast strains isolated from a particular industrial process may be adapted to such conditions and should be used as starter strain instead of less adapted commercial strains. This work reports the use of PCR-fingerprinting method based on microsatellite primer (GTG)5 to characterize the yeast population dynamics along the fermentation period in six distilleries. The results show that indigenous fermenting strains present in the crude substrate can be more adapted to the industrial process than commercial strains. We also identified new strains that dominate the yeast population and were more present either in molasses or sugar cane fermenting distilleries. Those strains were proposed to be used as starters in those industrial processes. This is the first report on the use of molecular markers to discriminate Saccharomyces cerevisiae strains from fuel-ethanol producing process.

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. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

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

PubMed

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

2016-07-03

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.

Introducing a New Breed of Wine Yeast: Interspecific Hybridisation between a Commercial Saccharomyces cerevisiae Wine Yeast and Saccharomyces mikatae

PubMed Central

Bellon, Jennifer R.; Schmid, Frank; Capone, Dimitra L.; Dunn, Barbara L.; Chambers, Paul J.

2013-01-01

Interspecific hybrids are commonplace in agriculture and horticulture; bread wheat and grapefruit are but two examples. The benefits derived from interspecific hybridisation include the potential of generating advantageous transgressive phenotypes. This paper describes the generation of a new breed of wine yeast by interspecific hybridisation between a commercial Saccharomyces cerevisiae wine yeast strain and Saccharomyces mikatae, a species hitherto not associated with industrial fermentation environs. While commercially available wine yeast strains provide consistent and reliable fermentations, wines produced using single inocula are thought to lack the sensory complexity and rounded palate structure obtained from spontaneous fermentations. In contrast, interspecific yeast hybrids have the potential to deliver increased complexity to wine sensory properties and alternative wine styles through the formation of novel, and wider ranging, yeast volatile fermentation metabolite profiles, whilst maintaining the robustness of the wine yeast parent. Screening of newly generated hybrids from a cross between a S. cerevisiae wine yeast and S. mikatae (closely-related but ecologically distant members of the Saccharomyces sensu stricto clade), has identified progeny with robust fermentation properties and winemaking potential. Chemical analysis showed that, relative to the S. cerevisiae wine yeast parent, hybrids produced wines with different concentrations of volatile metabolites that are known to contribute to wine flavour and aroma, including flavour compounds associated with non-Saccharomyces species. The new S. cerevisiae x S. mikatae hybrids have the potential to produce complex wines akin to products of spontaneous fermentation while giving winemakers the safeguard of an inoculated ferment. PMID:23614011

The impact of different ale brewer’s yeast strains on the proteome of immature beer

PubMed Central

2013-01-01

Background It is well known that brewer’s yeast affects the taste and aroma of beer. However, the influence of brewer’s yeast on the protein composition of beer is currently unknown. In this study, changes of the proteome of immature beer, i.e. beer that has not been matured after fermentation, by ale brewer’s yeast strains with different abilities to degrade fermentable sugars were investigated. Results Beers were fermented from standard hopped wort (13° Plato) using two ale brewer’s yeast (Saccharomyces cerevisiae) strains with different attenuation degrees. Both immature beers had the same alcohol and protein concentrations. Immature beer and unfermented wort proteins were analysed by 2-DE and compared in order to determine protein changes arising from fermentation. Distinct protein spots in the beer and wort proteomes were identified using Matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and MS/MS and revealed common beer proteins, such as lipid transfer proteins (LTP1 and LTP2), protein Z and amylase-protease inhibitors. During fermentation, two protein spots, corresponding to LTP2, disappeared, while three protein spots were exclusively found in beer. These three proteins, all derived from yeast, were identified as cell wall associated proteins, that is Exg1 (an exo-β-1,3-glucanase), Bgl2 (an endo-β-1,2-glucanase), and Uth1 (a cell wall biogenesis protein). Conclusion Yeast strain dependent changes in the immature beer proteome were identified, i.e. Bgl2 was present in beer brewed with KVL011, while lacking in WLP001 beer. PMID:24079909

From mannan to bioethanol: cell surface co-display of β-mannanase and β-mannosidase on yeast Saccharomyces cerevisiae.

PubMed

Ishii, Jun; Okazaki, Fumiyoshi; Djohan, Apridah Cameliawati; Hara, Kiyotaka Y; Asai-Nakashima, Nanami; Teramura, Hiroshi; Andriani, Ade; Tominaga, Masahiro; Wakai, Satoshi; Kahar, Prihardi; Yopi; Prasetya, Bambang; Ogino, Chiaki; Kondo, Akihiko

2016-01-01

Mannans represent the largest hemicellulosic fraction in softwoods and also serve as carbohydrate stores in various plants. However, the utilization of mannans as sustainable resources has been less advanced in sustainable biofuel development. Based on a yeast cell surface-display technology that enables the immobilization of multiple enzymes on the yeast cell walls, we constructed a recombinant Saccharomyces cerevisiae strain that co-displays β-mannanase and β-mannosidase; this strain is expected to facilitate ethanol fermentation using mannan as a biomass source. Parental yeast S. cerevisiae assimilated mannose and glucose as monomeric sugars, producing ethanol from mannose. We constructed yeast strains that express tethered β-mannanase and β-mannosidase; co-display of the two enzymes on the cell surface was confirmed by immunofluorescence staining and enzyme activity assays. The constructed yeast cells successfully hydrolyzed 1,4-β-d-mannan and produced ethanol by assimilating the resulting mannose without external addition of enzymes. Furthermore, the constructed strain produced ethanol from 1,4-β-d-mannan continually during the third batch of repeated fermentation. Additionally, the constructed strain produced ethanol from ivory nut mannan; ethanol yield was improved by NaOH pretreatment of the substrate. We successfully displayed β-mannanase and β-mannosidase on the yeast cell surface. Our results clearly demonstrate the utility of the strain co-displaying β-mannanase and β-mannosidase for ethanol fermentation from mannan biomass. Thus, co-tethering β-mannanase and β-mannosidase on the yeast cell surface provides a powerful platform technology for yeast fermentation toward the production of bioethanol and other biochemicals from lignocellulosic materials containing mannan components.

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. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

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

Filtration, haze and foam characteristics of fermented wort mediated by yeast strain.

PubMed

Douglas, P; Meneses, F J; Jiranek, V

2006-01-01

To investigate the influence of the choice of yeast strain on the haze, shelf life, filterability and foam quality characteristics of fermented products. Twelve strains were used to ferment a chemically defined wort and hopped ale or stout wort. Fermented products were assessed for foam using the Rudin apparatus, and filterability and haze characteristics using the European Brewing Convention methods, to reveal differences in these parameters as a consequence of the choice of yeast strain and growth medium. Under the conditions used, the choice of strain of Saccharomyces cerevisiae effecting the primary fermentation has an impact on all of the parameters investigated, most notably when the fermentation medium is devoid of macromolecular material. The filtration of fermented products has a large cost implication for many brewers and wine makers, and the haze of the resulting filtrate is a key quality criterion. Also of importance to the quality of beer and some wines is the foaming and head retention of these beverages. The foam characteristics, filterability and potential for haze formation in a fermented product have long been known to be dependant on the raw materials used, as well as other production parameters. The choice of Saccharomyces cerevisiae strain used to ferment has itself been shown here to influence these parameters.

Genomic diversity of Saccharomyces cerevisiae yeasts associated with alcoholic fermentation of bacanora produced by artisanal methods.

PubMed

Álvarez-Ainza, M L; Zamora-Quiñonez, K A; Moreno-Ibarra, G M; Acedo-Félix, E

2015-03-01

Bacanora is a spirituous beverage elaborated with Agave angustifolia Haw in an artisanal process. Natural fermentation is mostly performed with native yeasts and bacteria. In this study, 228 strains of yeast like Saccharomyces were isolated from the natural alcoholic fermentation on the production of bacanora. Restriction analysis of the amplified region ITS1-5.8S-ITS2 of the ribosomal DNA genes (RFLPr) were used to confirm the genus, and 182 strains were identified as Saccharomyces cerevisiae. These strains displayed high genomic variability in their chromosomes profiles by karyotyping. Electrophoretic profiles of the strains evaluated showed a large number of chromosomes the size of which ranged between 225 and 2200 kpb approximately.

[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).

Chromosomal Aneuploidy Improves the Brewing Characteristics of Sake Yeast.

PubMed

Kadowaki, Masafumi; Fujimaru, Yuki; Taguchi, Seiga; Ferdouse, Jannatul; Sawada, Kazutaka; Kimura, Yuta; Terasawa, Yohei; Agrimi, Gennaro; Anai, Toyoaki; Noguchi, Hideki; Toyoda, Atsushi; Fujiyama, Asao; Akao, Takeshi; Kitagaki, Hiroshi

2017-12-15

The effect of chromosomal aneuploidy on the brewing characteristics of brewery yeasts has not been studied. Here we report that chromosomal aneuploidy in sake brewery yeast ( Saccharomyces cerevisiae ) leads to the development of favorable brewing characteristics. We found that pyruvate-underproducing sake yeast, which produces less off-flavor diacetyl, is aneuploid and trisomic for chromosomes XI and XIV. To confirm that this phenotype is due to aneuploidy, we obtained 45 haploids with various chromosomal additions and investigated their brewing profiles. A greater number of chromosomes correlated with a decrease in pyruvate production. Especially, sake yeast haploids with extra chromosomes in addition to chromosome XI produced less pyruvate than euploids. Mitochondrion-related metabolites and intracellular oxygen species in chromosome XI aneuploids were higher than those in euploids, and this effect was canceled in their "petite" strains, suggesting that an increase in chromosomes upregulated mitochondrial activity and decreased pyruvate levels. These findings suggested that an increase in chromosome number, including chromosome XI, in sake yeast haploids leads to pyruvate underproduction through the augmentation of mitochondrial activity. This is the first report proposing that aneuploidy in brewery yeasts improves their brewing profile. IMPORTANCE Chromosomal aneuploidy has not been evaluated in development of sake brewing yeast strains. This study shows the relationship between chromosomal aneuploidy and brewing characteristics of brewery yeast strains. High concentrations of pyruvate during sake storage give rise to α-acetolactate and, in turn, to high concentrations of diacetyl, which is considered an off-flavor. It was demonstrated that pyruvate-underproducing sake yeast is trisomic for chromosome XI and XIV. Furthermore, sake yeast haploids with extra chromosomes produced reduced levels of pyruvate and showed metabolic processes characteristic of

Chromosomal Aneuploidy Improves the Brewing Characteristics of Sake Yeast

PubMed Central

Kadowaki, Masafumi; Fujimaru, Yuki; Taguchi, Seiga; Ferdouse, Jannatul; Sawada, Kazutaka; Kimura, Yuta; Terasawa, Yohei; Agrimi, Gennaro; Anai, Toyoaki; Noguchi, Hideki; Toyoda, Atsushi; Fujiyama, Asao; Akao, Takeshi

2017-01-01

ABSTRACT The effect of chromosomal aneuploidy on the brewing characteristics of brewery yeasts has not been studied. Here we report that chromosomal aneuploidy in sake brewery yeast (Saccharomyces cerevisiae) leads to the development of favorable brewing characteristics. We found that pyruvate-underproducing sake yeast, which produces less off-flavor diacetyl, is aneuploid and trisomic for chromosomes XI and XIV. To confirm that this phenotype is due to aneuploidy, we obtained 45 haploids with various chromosomal additions and investigated their brewing profiles. A greater number of chromosomes correlated with a decrease in pyruvate production. Especially, sake yeast haploids with extra chromosomes in addition to chromosome XI produced less pyruvate than euploids. Mitochondrion-related metabolites and intracellular oxygen species in chromosome XI aneuploids were higher than those in euploids, and this effect was canceled in their “petite” strains, suggesting that an increase in chromosomes upregulated mitochondrial activity and decreased pyruvate levels. These findings suggested that an increase in chromosome number, including chromosome XI, in sake yeast haploids leads to pyruvate underproduction through the augmentation of mitochondrial activity. This is the first report proposing that aneuploidy in brewery yeasts improves their brewing profile. IMPORTANCE Chromosomal aneuploidy has not been evaluated in development of sake brewing yeast strains. This study shows the relationship between chromosomal aneuploidy and brewing characteristics of brewery yeast strains. High concentrations of pyruvate during sake storage give rise to α-acetolactate and, in turn, to high concentrations of diacetyl, which is considered an off-flavor. It was demonstrated that pyruvate-underproducing sake yeast is trisomic for chromosome XI and XIV. Furthermore, sake yeast haploids with extra chromosomes produced reduced levels of pyruvate and showed metabolic processes characteristic

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.

Immobilisation increases yeast cells' resistance to dehydration-rehydration treatment.

PubMed

Borovikova, Diana; Rozenfelde, Linda; Pavlovska, Ilona; Rapoport, Alexander

2014-08-20

This study was performed with the goal of revealing if the dehydration procedure used in our new immobilisation method noticeably decreases the viability of yeast cells in immobilised preparations. Various yeasts were used in this research: Saccharomyces cerevisiae cells that were rather sensitive to dehydration and had been aerobically grown in an ethanol-containing medium, a recombinant strain of S. cerevisiae grown in aerobic conditions which were completely non-resistant to dehydration and an anaerobically grown bakers' yeast strain S. cerevisiae, as well as a fairly resistant Pichia pastoris strain. Experiments performed showed that immobilisation of all these strains essentially increased their resistance to a dehydration-rehydration treatment. The increase of cells' viability (compared with control cells dehydrated in similar conditions) was from 30 to 60%. It is concluded that a new immobilisation method, which includes a dehydration stage, does not lead to an essential loss of yeast cell viability. Correspondingly, there is no risk of losing the biotechnological activities of immobilised preparations. The possibility of producing dry, active yeast preparations is shown, for those strains that are very sensitive to dehydration and which can be used in biotechnology in an immobilised form. Finally, the immobilisation approach can be used for the development of efficient methods for the storage of recombinant yeast strains. Copyright © 2014 Elsevier B.V. All rights reserved.

Technological properties of bakers' yeasts in durum wheat semolina dough.

PubMed

Giannone, Virgilio; Longo, Chiara; Damigella, Arcangelo; Raspagliesi, Domenico; Spina, Alfio; Palumbo, Massimo

2010-04-01

Properties of 13 Saccharomyces cerevisiae strains isolated from different sources (traditional sourdoughs, industrial baking yeasts etc.) were studied in dough produced with durum wheat (Sicilian semolina, variety Mongibello). Durum wheat semolina and durum wheat flour are products prepared from grain of durum wheat (Triticum durum Desf.) by grinding or milling processes in which the bran and germ are essentially removed and the remainder is comminuted to a suitable degree of fineness. Acidification and leavening properties of the dough were evaluated. Strains isolated from traditional sourdoughs (DSM PST18864, DSM PST18865 and DSM PST18866) showed higher leavening power, valuable after the first and second hours of fermentation, than commercial baking yeasts. In particular the strain DSM PST 18865 has also been successfully tested in bakery companies for the improvement of production processes. Baking and staling tests were carried out on five yeast strains to evaluate their fermentation ability directly and their resistance to the staling process. Amplified fragment length polymorphism (fAFLP) was used to investigate genetic variations in the yeast strains. This study showed an appreciable biodiversity in the microbial populations of both wild and commercial yeast strains.

Improvement of Brazilian bioethanol production - Challenges and perspectives on the identification and genetic modification of new strains of Saccharomyces cerevisiae yeasts isolated during ethanol process.

PubMed

Paulino de Souza, Jonas; Dias do Prado, Cleiton; Eleutherio, Elis C A; Bonatto, Diego; Malavazi, Iran; Ferreira da Cunha, Anderson

2018-06-01

In Brazil, bioethanol is produced by sucrose fermentation from sugarcane by Saccharomyces cerevisiae in a fed-batch process that uses high density of yeast cells (15-25 % of wet weight/v) and high sugar concentration (18-22 % of total sugars). Several research efforts have been employed to improve the efficiency of this process through the isolation of yeasts better adapted to the Brazilian fermentation conditions. Two important wild strains named CAT-1 and PE-2 were isolated during the fermentation process and were responsible for almost 60 % of the total ethanol production in Brazil. However, in the last decade the fermentative substrate composition was much modified, since new sugar cane crops were developed, the use of molasses instead of sugar cane juice increase and with the prohibition of burning of sugarcane prior harvest. As consequence, these previously isolated strains are being replaced by new wild yeasts in most of ethanol plants. In this new scenario the isolation of novel better adapted yeasts with improved fermentative characteristics is still a big challenge. Here, we discuss the main aspects of Brazilian ethanol production and the efforts for the selection, characterization and genetic modifications of new strains with important phenotypic traits such as thermotolerance. Copyright © 2017 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Expression of LIP1 and LIP2 genes from Geotrichum species in Baker's yeast strains and their application to the bread-making process.

PubMed

Monfort, A; Blasco, A; Sanz, P; Prieto, J A

1999-02-01

Lipolytic baker's yeast strains able to produce extracellular active lipase have been constructed by transformation with plasmids containing the LIP1 and LIP2 genes from Geotrichum sp. under the control of the Saccharomyces cerevisiae actin promoter (pACT1). Lipase productivity differed between both constructs, YEpACT-LIP1-t and YEpACT-LIP2-t, being higher for the strain bearing the LIP2 gene in all culture media tested. This result appeared not to be the consequence of a defect in the transcription of the LIP1 gene as revealed by Northern blot analysis. Replacing the signal sequence of LIP1 by that of LIP2 in the YEpACT-LIP1-t plasmid enhanced significantly the secretion of lipase 1, but the levels of lipase activity were still lower than those found for the YEpACT-LIP2-t transformant. Recombinant lipase 2 protein produced by baker's yeast exhibited biochemical properties similar to those of the natural enzyme. Fermented dough prepared with YEpACT-LIP2-t-carrying cells rendered a bread with a higher loaf volume and a more uniform crumb structure than that prepared with control yeast. These effects were stronger by the addition in the bread dough formulas of a preferment enriched in recombinant lipase 2.

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

PubMed

Caspeta, Luis; Nielsen, Jens

2015-07-21

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. Yeast thermotolerance can significantly reduce the production costs of biomass

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.

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. Copyright 2002 John Wiley & Sons, Ltd.

Immobilised Sarawak Malaysia yeast cells for production of bioethanol.

PubMed

Zain, Masniroszaime Mohd; Kofli, Noorhisham Tan; Rozaimah, Siti; Abdullah, Sheikh

2011-05-01

Bioethanol production using yeast has become a popular topic due to worrying depleting worldwide fuel reserve. The aim of the study was to investigate the capability of Malaysia yeast strains isolated from starter culture used in traditional fermented food and alcoholic beverages in producing Bioethanol using alginate beads entrapment method. The starter yeast consists of groups of microbes, thus the yeasts were grown in Sabouraud agar to obtain single colony called ST1 (tuak) and ST3 (tapai). The growth in Yeast Potatoes Dextrose (YPD) resulted in specific growth of ST1 at micro = 0.396 h-1 and ST3 at micro = 0.38 h-1, with maximum ethanol production of 7.36 g L-1 observed using ST1 strain. The two strains were then immobilized using calcium alginate entrapment method producing average alginate beads size of 0.51 cm and were grown in different substrates; YPD medium and Local Brown Sugar (LBS) for 8 h in flask. The maximum ethanol concentration measured after 7 h were at 6.63 and 6.59 g L-1 in YPD media and 1.54 and 1.39 g L-1in LBS media for ST1 and ST3, respectively. The use of LBS as carbon source showed higher yield of product (Yp/s), 0.59 g g-1 compared to YPD, 0.25 g g-1 in ST1 and (Yp/s), 0.54 g g-1 compared to YPD, 0.24 g g-1 in ST3 . This study indicated the possibility of using local strains (STI and ST3) to produce bioethanol via immobilization technique with local materials as substrate.

Single-cell Protein and Xylitol Production by a Novel Yeast Strain Candida intermedia FL023 from Lignocellulosic Hydrolysates and Xylose.

PubMed

Wu, Jiaqiang; Hu, Jinlong; Zhao, Shumiao; He, Mingxiong; Hu, Guoquan; Ge, Xiangyang; Peng, Nan

2018-05-01

Yeasts are good candidates to utilize the hydrolysates of lignocellulose, the most abundant bioresource, for bioproducts. This study aimed to evaluate the efficiencies of single-cell protein (SCP) and xylitol production by a novel yeast strain, Candida intermedia FL023, from lignocellulosic hydrolysates and xylose. This strain efficiently assimilated hexose, pentose, and cellubiose for cell mass production with the crude protein content of 484.2 g kg -1 dry cell mass. SCP was produced by strain FL023 using corncob hydrolysate and urea as the carbon and nitrogen sources with the dry cell mass productivity 0.86 g L -1  h -1 and the yield of 0.40 g g -1 sugar. SCP was also produced using NaOH-pretreated Miscanthus sinensis straw and corn steep liquor as the carbon and nitrogen sources through simultaneous saccharification and fermentation with the dry cell productivity of 0.23 g L -1  h -1 and yield of 0.17 g g -1 straw. C. intermedia FL023 was tolerant to 0.5 g L -1 furfural, acetic acid, and syringaldehyde in xylitol fermentation and produced 45.7 g L -1 xylitol from xylose with the productivity of 0.38 g L -1  h -1 and the yield of 0.57 g g -1 xylose. This study provides feasible methods for feed and food additive production from the abundant lignocellulosic bioresources.

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

PubMed

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

2015-01-01

The objectives of this study were to assess the differences in fermentative behaviour of two different strains of Saccharomyces cerevisiae (EC1118 and RC212) and to determine the differences in composition and sensory properties of raspberry wines fermented with immobilized and suspended yeast cells of both strains at 15 °C. Analyses of aroma compounds, glycerol, acetic acid and ethanol, as well as the kinetics of fermentation and a sensory evaluation of the wines, were performed. All fermentations with immobilized yeast cells had a shorter lag phase and faster utilization of sugars and ethanol production than those fermented with suspended cells. Slower fermentation kinetics were observed in all the samples that were fermented with strain RC212 (suspended and immobilized) than in samples fermented with strain EC1118. Significantly higher amounts of acetic acid were detected in all samples fermented with strain RC212 than in those fermented with strain EC1118 (0.282 and 0.602 g/l, respectively). Slightly higher amounts of glycerol were observed in samples fermented with strain EC1118 than in those fermented with strain RC212. Copyright © 2014 John Wiley & Sons, Ltd.

Production and Its Anti-hyperglycemic Effects of γ-Aminobutyric Acid from the Wild Yeast Strain Pichia silvicola UL6-1 and Sporobolomyces carnicolor 402-JB-1.

PubMed

Han, Sang-Min; Lee, Jong-Soo

2017-09-01

This study was done to produce γ-aminobutyric acid (GABA) from wild yeast as well as investigate its anti-hyperglycemic effects. Among ten GABA-producing yeast strains, Pichia silvicola UL6-1 and Sporobolomyces carnicolor 402-JB-1 produced high GABA concentration of 134.4 µg/mL and 179.2 µg/mL, respectively. P. silvicola UL6-1 showed a maximum GABA yield of 136.5 µg/mL and 200.8 µg/mL from S. carnicolor 402-JB-1 when they were cultured for 30 hr at 30℃ in yeast extract-peptone-dextrose medium. The cell-free extract from P. silvicola UL6-1 and S. carnicolor 402-JB-1 showed very high anti-hyperglycemic α-glucosidase inhibitory activity of 72.3% and 69.9%, respectively. Additionally, their cell-free extract-containing GABA showed the anti-hyperglycemic effect in streptozotocin-induced diabetic Sprague-Dawley rats.

Brewing characteristics of piezosensitive sake yeasts

NASA Astrophysics Data System (ADS)

Nomura, Kazuki; Hoshino, Hirofumi; Igoshi, Kazuaki; Onozuka, Haruka; Tanaka, Erika; Hayashi, Mayumi; Yamazaki, Harutake; Takaku, Hiroaki; Iguchi, Akinori; Shigematsu, Toru

2018-04-01

Application of high hydrostatic pressure (HHP) treatment to food processing is expected as a non-thermal fermentation regulation technology that supresses over fermentation. However, the yeast Saccharomyces cerevisiae used for Japanese rice wine (sake) brewing shows high tolerance to HHP. Therefore, we aimed to generate pressure-sensitive (piezosensitive) sake yeast strains by mating sake with piezosensitive yeast strains to establish an HHP fermentation regulation technology and extend the shelf life of fermented foods. The results of phenotypic analyses showed that the generated yeast strains were piezosensitive and exhibited similar fermentation ability compared with the original sake yeast strain. In addition, primary properties of sake brewed using these strains, such as ethanol concentration, sake meter value and sake flavor compounds, were almost equivalent to those obtained using the sake yeast strain. These results suggest that the piezosensitive strains exhibit brewing characteristics essentially equivalent to those of the sake yeast strain.

Phenotypic and metabolic traits of commercial Saccharomyces cerevisiae yeasts

PubMed Central

2014-01-01

Currently, pursuing yeast strains that display both a high potential fitness for alcoholic fermentation and a favorable impact on quality is a major goal in the alcoholic beverage industry. This considerable industrial interest has led to many studies characterizing the phenotypic and metabolic traits of commercial yeast populations. In this study, 20 Saccharomyces cerevisiae strains from different geographical origins exhibited high phenotypic diversity when their response to nine biotechnologically relevant conditions was examined. Next, the fermentation fitness and metabolic traits of eight selected strains with a unique phenotypic profile were evaluated in a high-sugar synthetic medium under two nitrogen regimes. Although the strains exhibited significant differences in nitrogen requirements and utilization rates, a direct relationship between nitrogen consumption, specific growth rate, cell biomass, cell viability, acetic acid and glycerol formation was only observed under high-nitrogen conditions. In contrast, the strains produced more succinic acid under the low-nitrogen regime, and a direct relationship with the final cell biomass was established. Glucose and fructose utilization patterns depended on both yeast strain and nitrogen availability. For low-nitrogen fermentation, three strains did not fully degrade the fructose. This study validates phenotypic and metabolic diversity among commercial wine yeasts and contributes new findings on the relationship between nitrogen availability, yeast cell growth and sugar utilization. We suggest that measuring nitrogen during the stationary growth phase is important because yeast cells fermentative activity is not exclusively related to population size, as previously assumed, but it is also related to the quantity of nitrogen consumed during this growth phase. PMID:24949272

Phenotypic and metabolic traits of commercial Saccharomyces cerevisiae yeasts.

PubMed

Barbosa, Catarina; Lage, Patrícia; Vilela, Alice; Mendes-Faia, Arlete; Mendes-Ferreira, Ana

2014-01-01

Currently, pursuing yeast strains that display both a high potential fitness for alcoholic fermentation and a favorable impact on quality is a major goal in the alcoholic beverage industry. This considerable industrial interest has led to many studies characterizing the phenotypic and metabolic traits of commercial yeast populations. In this study, 20 Saccharomyces cerevisiae strains from different geographical origins exhibited high phenotypic diversity when their response to nine biotechnologically relevant conditions was examined. Next, the fermentation fitness and metabolic traits of eight selected strains with a unique phenotypic profile were evaluated in a high-sugar synthetic medium under two nitrogen regimes. Although the strains exhibited significant differences in nitrogen requirements and utilization rates, a direct relationship between nitrogen consumption, specific growth rate, cell biomass, cell viability, acetic acid and glycerol formation was only observed under high-nitrogen conditions. In contrast, the strains produced more succinic acid under the low-nitrogen regime, and a direct relationship with the final cell biomass was established. Glucose and fructose utilization patterns depended on both yeast strain and nitrogen availability. For low-nitrogen fermentation, three strains did not fully degrade the fructose. This study validates phenotypic and metabolic diversity among commercial wine yeasts and contributes new findings on the relationship between nitrogen availability, yeast cell growth and sugar utilization. We suggest that measuring nitrogen during the stationary growth phase is important because yeast cells fermentative activity is not exclusively related to population size, as previously assumed, but it is also related to the quantity of nitrogen consumed during this growth phase.

Mutagenizing brewing yeast strain for improving fermentation property of beer.

PubMed

Liu, Zengran; Zhang, Guangyi; Sun, Yunping

2008-07-01

A brewing yeast mutant with perfect sugar fermentation capacity was isolated by mutagenizing the Saccharomyces pastorianus transformant, which carries an integrated glucoamylase gene and has one copy of non-functional alpha-acetolactate synthase gene. The mutant was able to utilize maltotriose efficiently, and the maltotriose fermentability in YNB-2% maltotriose medium increased from 32.4% to 72.0% after 5 d in shaking culture. The wort fermentation test confirmed that the sugar fermentation property of the mutant was greatly improved, while its brewing performances were analogous to that of the wild-type strain and the characteristic trait of shortened beer maturation period was retained. Therefore, we believe that the brewing yeast mutant would benefit the beer industry and would be useful for low caloric beer production.

Past and Future of Non-Saccharomyces Yeasts: From Spoilage Microorganisms to Biotechnological Tools for Improving Wine Aroma Complexity

PubMed Central

Padilla, Beatriz; Gil, José V.; Manzanares, Paloma

2016-01-01

It is well established that non-Saccharomyces wine yeasts, considered in the past as undesired or spoilage yeasts, can enhance the analytical composition, and aroma profile of the wine. The contribution of non-Saccharomyces yeasts, including the ability to secret enzymes and produce secondary metabolites, glycerol and ethanol, release of mannoproteins or contributions to color stability, is species- and strain-specific, pointing out the key importance of a clever strain selection. The use of mixed starters of selected non-Saccharomyces yeasts with strains of Saccharomyces cerevisiae represents an alternative to both spontaneous and inoculated wine fermentations, taking advantage of the potential positive role that non-Saccharomyces wine yeast species play in the organoleptic characteristics of wine. In this context mixed starters can meet the growing demand for new and improved wine yeast strains adapted to different types and styles of wine. With the aim of presenting old and new evidences on the potential of non-Saccharomyces yeasts to address this market trend, we mainly review the studies focused on non-Saccharomyces strain selection and design of mixed starters directed to improve primary and secondary aroma of wines. The ability of non-Saccharomyces wine yeasts to produce enzymes and metabolites of oenological relevance is also discussed. PMID:27065975

Past and Future of Non-Saccharomyces Yeasts: From Spoilage Microorganisms to Biotechnological Tools for Improving Wine Aroma Complexity.

PubMed

Padilla, Beatriz; Gil, José V; Manzanares, Paloma

2016-01-01

It is well established that non-Saccharomyces wine yeasts, considered in the past as undesired or spoilage yeasts, can enhance the analytical composition, and aroma profile of the wine. The contribution of non-Saccharomyces yeasts, including the ability to secret enzymes and produce secondary metabolites, glycerol and ethanol, release of mannoproteins or contributions to color stability, is species- and strain-specific, pointing out the key importance of a clever strain selection. The use of mixed starters of selected non-Saccharomyces yeasts with strains of Saccharomyces cerevisiae represents an alternative to both spontaneous and inoculated wine fermentations, taking advantage of the potential positive role that non-Saccharomyces wine yeast species play in the organoleptic characteristics of wine. In this context mixed starters can meet the growing demand for new and improved wine yeast strains adapted to different types and styles of wine. With the aim of presenting old and new evidences on the potential of non-Saccharomyces yeasts to address this market trend, we mainly review the studies focused on non-Saccharomyces strain selection and design of mixed starters directed to improve primary and secondary aroma of wines. The ability of non-Saccharomyces wine yeasts to produce enzymes and metabolites of oenological relevance is also discussed.

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.

A rapid method for differentiating Saccharomyces sensu stricto strains from other yeast species in an enological environment.

PubMed

Nardi, Tiziana; Carlot, Milena; De Bortoli, Elena; Corich, Viviana; Giacomini, Alessio

2006-11-01

During programs for the selection of enological yeasts, several hundred natural isolates are usually screened. The scope of these operations is to isolate strains possessing good fermentative properties without necessarily arriving at a precise species designation: in other words, to detect strains belonging to the Saccharomyces sensu stricto complex. In the present study, a pair of primers, designed within the variable D1/D2 region of the 26S subunit of ribosomal yeast RNA, have been constructed. These generate an amplification fragment of 471 bp that is specific for the seven Saccharomyces sensu stricto species, while no signal was obtained for Saccharomyces sensu lato strains (17 species) or for another 18 selected species commonly found in enological environments. A second pair of primers was also constructed, within the 18S rRNA gene, composed of perfectly conserved sequences common for all 42 yeast species examined, which generate a 900 bp (c.) band for all strains. This was used as a positive experimental control in multiplex PCR analysis using all four primers.

Yeast selection for fuel ethanol production in Brazil.

PubMed

Basso, Luiz C; de Amorim, Henrique V; de Oliveira, Antonio J; Lopes, Mario L

2008-11-01

Brazil is one of the largest ethanol biofuel producers and exporters in the world and its production has increased steadily during the last three decades. The increasing efficiency of Brazilian ethanol plants has been evident due to the many technological contributions. As far as yeast is concerned, few publications are available regarding the industrial fermentation processes in Brazil. The present paper reports on a yeast selection program performed during the last 12 years aimed at selecting Saccharomyces cerevisiae strains suitable for fermentation of sugar cane substrates (cane juice and molasses) with cell recycle, as it is conducted in Brazilian bioethanol plants. As a result, some evidence is presented showing the positive impact of selected yeast strains in increasing ethanol yield and reducing production costs, due to their higher fermentation performance (high ethanol yield, reduced glycerol and foam formation, maintenance of high viability during recycling and very high implantation capability into industrial fermenters). Results also suggest that the great yeast biodiversity found in distillery environments could be an important source of strains. This is because during yeast cell recycling, selective pressure (an adaptive evolution) is imposed on cells, leading to strains with higher tolerance to the stressful conditions of the industrial fermentation.

Glycobiology in yeast: production of bio-ative biopolymers and small molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scheller, Henrik

The accomplished goals of the CRADA were the establishment of a yeast strain capable of producing levels of vanillin suitable for commercial production and the identification of novel glycosyltransferases to construct the biosynthetic pathway of a gum Arabic-variant in yeast.

Effects of feedstock and co-culture of Lactobacillus fermentum and wild Saccharomyces cerevisiae strain during fuel ethanol fermentation by the industrial yeast strain PE-2.

PubMed

Reis, Vanda R; Bassi, Ana Paula G; Cerri, Bianca C; Almeida, Amanda R; Carvalho, Isis G B; Bastos, Reinaldo G; Ceccato-Antonini, Sandra R

2018-02-16

Even though contamination by bacteria and wild yeasts are frequently observed during fuel ethanol fermentation, our knowledge regarding the effects of both contaminants together is very limited, especially considering that the must composition can vary from exclusively sugarcane juice to a mixture of molasses and juice, affecting the microbial development. Here we studied the effects of the feedstock (sugarcane juice and molasses) and the co-culture of Lactobacillus fermentum and a wild Saccharomyces cerevisiae strain (rough colony and pseudohyphae) in single and multiple-batch fermentation trials with an industrial strain of S. cerevisiae (PE-2) as starter yeast. The results indicate that in multiple-cycle batch system, the feedstock had a minor impact on the fermentation than in single-cycle batch system, however the rough yeast contamination was more harmful than the bacterial contamination in multiple-cycle batch fermentation. The inoculation of both contaminants did not potentiate the detrimental effect in any substrate. The residual sugar concentration in the fermented broth had a higher concentration of fructose than glucose for all fermentations, but in the presence of the rough yeast, the discrepancy between fructose and glucose concentrations were markedly higher, especially in molasses. The biggest problem associated with incomplete fermentation seemed to be the lower consumption rate of sugar and the reduced fructose preference of the rough yeast rather than the lower invertase activity. Lower ethanol production, acetate production and higher residual sugar concentration are characteristics strongly associated with the rough yeast strain and they were not potentiated with the inoculation of L. fermentum.

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.

Genealogy of principal strains of the yeast genetic stock center.

PubMed

Mortimer, R K; Johnston, J R

1986-05-01

We have constructed a genealogy of strain S288C, from which many of the mutant and segregant strains currently used in studies on the genetics and molecular biology of Saccharomyces cerevisiae have been derived. We have determined that its six progenitor strains were EM93, EM126, NRRL YB-210 and the three baking strains Yeast Foam, FLD and LK. We have estimated that approximately 88% of the gene pool of S288C is contributed by strain EM93. The principal ancestral genotypes were those of segregant strains EM93-1C and EM93-3B, initially distributed by C. C. Lindegren to several laboratories. We have analyzed an isolate of lyophilized culture of strain EM93 and determined its genotype as MATa/MAT alpha SUC2/SUC2 GAL2/gal2 MAL/MAL mel/mel CUP1/cup1 FLO1/flo1. Strain EM93 is therefore the probable origin of genes SUC2, gal2, CUP1 and flo1 of S288C. We give details of the current availability of several of the progenitor strains and propose that this genealogy should be of assistance in elucidating the origins of several types of genetic and molecular heterogeneities in Saccharomyces.

Chemical genomic guided engineering of gamma-valerolactone tolerant yeast.

PubMed

Bottoms, Scott; Dickinson, Quinn; McGee, Mick; Hinchman, Li; Higbee, Alan; Hebert, Alex; Serate, Jose; Xie, Dan; Zhang, Yaoping; Coon, Joshua J; Myers, Chad L; Landick, Robert; Piotrowski, Jeff S

2018-01-12

. This strain represents a xylose fermenting yeast specifically tailored to GVL produced hydrolysates.

Effects of distillation system and yeast strain on the aroma profile of Albariño (Vitis vinifera L.) grape pomace spirits.

PubMed

Arrieta-Garay, Y; Blanco, P; López-Vázquez, C; Rodríguez-Bencomo, J J; Pérez-Correa, J R; López, F; Orriols, I

2014-10-29

Orujo is a traditional alcoholic beverage produced in Galicia (northwest Spain) from distillation of grape pomace, a byproduct of the winemaking industry. In this study, the effect of the distillation system (copper charentais alembic versus packed column) and the yeast strain (native yeast L1 versus commercial yeast L2) on the chemical and sensory characteristics of orujo obtained from Albariño (Vitis vinifera L.) grape pomace has been analyzed. Principal component analysis, with two components explaining 74% of the variance, is able to clearly differentiate the distillates according to distillation system and yeast strain. Principal component 1, mainly defined by C6-C12 esters, isoamyl octanoate, and methanol, differentiates L1 from L2 distillates. In turn, principal component 2, mainly defined by linear alcohols, linalool, and 1-hexenol, differentiates alembic from packed column distillates. In addition, an aroma descriptive test reveals that the distillate obtained with a packed column from a pomace fermented with L1 presented the highest positive general impression, which is associated with the highest fruity and smallest solvent aroma scores. Moreover, chemical analysis shows that use of a packed column increases average ethanol recovery by 12%, increases the concentration of C6-C12 esters by 25%, and reduces the concentration of higher alcohols by 21%. In turn, L2 yeast obtained lower scores in the alembic distillates aroma profile. In addition, with L1, 9% higher ethanol yields were achieved, and L2 distillates contained 34%-40% more methanol than L1 distillates.

Production and Its Anti-hyperglycemic Effects of γ-Aminobutyric Acid from the Wild Yeast Strain Pichia silvicola UL6-1 and Sporobolomyces carnicolor 402-JB-1

PubMed Central

Han, Sang-Min

2017-01-01

This study was done to produce γ-aminobutyric acid (GABA) from wild yeast as well as investigate its anti-hyperglycemic effects. Among ten GABA-producing yeast strains, Pichia silvicola UL6-1 and Sporobolomyces carnicolor 402-JB-1 produced high GABA concentration of 134.4 µg/mL and 179.2 µg/mL, respectively. P. silvicola UL6-1 showed a maximum GABA yield of 136.5 µg/mL and 200.8 µg/mL from S. carnicolor 402-JB-1 when they were cultured for 30 hr at 30℃ in yeast extract-peptone-dextrose medium. The cell-free extract from P. silvicola UL6-1 and S. carnicolor 402-JB-1 showed very high anti-hyperglycemic α-glucosidase inhibitory activity of 72.3% and 69.9%, respectively. Additionally, their cell-free extract-containing GABA showed the anti-hyperglycemic effect in streptozotocin-induced diabetic Sprague-Dawley rats. PMID:29138625

Functional inclusion bodies produced in the yeast Pichia pastoris.

PubMed

Rueda, Fabián; Gasser, Brigitte; Sánchez-Chardi, Alejandro; Roldán, Mònica; Villegas, Sandra; Puxbaum, Verena; Ferrer-Miralles, Neus; Unzueta, Ugutz; Vázquez, Esther; Garcia-Fruitós, Elena; Mattanovich, Diethard; Villaverde, Antonio

2016-10-01

Bacterial inclusion bodies (IBs) are non-toxic protein aggregates commonly produced in recombinant bacteria. They are formed by a mixture of highly stable amyloid-like fibrils and releasable protein species with a significant extent of secondary structure, and are often functional. As nano structured materials, they are gaining biomedical interest because of the combination of submicron size, mechanical stability and biological activity, together with their ability to interact with mammalian cell membranes for subsequent cell penetration in absence of toxicity. Since essentially any protein species can be obtained as IBs, these entities, as well as related protein clusters (e.g., aggresomes), are being explored in biocatalysis and in biomedicine as mechanically stable sources of functional protein. One of the major bottlenecks for uses of IBs in biological interfaces is their potential contamination with endotoxins from producing bacteria. To overcome this hurdle, we have explored here the controlled production of functional IBs in the yeast Pichia pastoris (Komagataella spp.), an endotoxin-free host system for recombinant protein production, and determined the main physicochemical and biological traits of these materials. Quantitative and qualitative approaches clearly indicate the formation of IBs inside yeast, similar in morphology, size and biological activity to those produced in E. coli, that once purified, interact with mammalian cell membranes and penetrate cultured mammalian cells in absence of toxicity. Structurally and functionally similar from those produced in E. coli, the controlled production of IBs in P. pastoris demonstrates that yeasts can be used as convenient platforms for the biological fabrication of self-organizing protein materials in absence of potential endotoxin contamination and with additional advantages regarding, among others, post-translational modifications often required for protein functionality.

Breeding of Freeze-tolerant Yeast and the Mechanisms of Stress-tolerance

NASA Astrophysics Data System (ADS)

Hino, Akihiro

Frozen dough method have been adopted in the baking industry to reduce labor and to produce fresh breads in stores. New freeze-tolerant yeasts for frozen dough preparations were isolated from banana peel and identified. To obtain strains that have fermentative ability even after several months of frozen storage in fermented dough, we attempted to breed new freeze-tolerantstrain. The hybrid between S.cerevisiae, which is a isolated freeze-tolerant strain, and a strain isolated from bakers' yeast with sexual conjugation gave a good quality bread made from frozen dough method. Freeze-tolerant strains showed higher surviving and trehalose accumulating abilities than freeze-sensitive strains. The freeze tolerance of the yeasts was associated with the basal amount of intracellular trehalose after rapid degradation at the onset of the prefermentation period. The complicated metabolic pathway and the regulation system of trehalose in yeast cells are introduced. The trehalose synthesis may act as a metabolic buffer system which contribute to maintain the intracellular inorganic phosphate and as a feedback regulation system in the glycolysis. However, it is not known enough how the trehalose protects yeast cells from stress.

Nitrogen requirements of commercial wine yeast strains during fermentation of a synthetic grape must.

PubMed

Gutiérrez, Alicia; Chiva, Rosana; Sancho, Marta; Beltran, Gemma; Arroyo-López, Francisco Noé; Guillamon, José Manuel

2012-08-01

Nitrogen deficiencies in grape musts are one of the main causes of stuck or sluggish wine fermentations. Currently, the most common method for dealing with nitrogen-deficient fermentations is adding supplementary nitrogen (usually ammonium phosphate). However, it is important to know the specific nitrogen requirement of each strain, to avoid excessive addition that can lead to microbial instability and ethyl carbamate accumulation. In this study, we aimed to determine the effect of increasing nitrogen concentrations of three different nitrogen sources on growth and fermentation performance in four industrial wine yeast strains. This task was carried out using statistical modeling techniques. The strains PDM and RVA showed higher growth-rate and maximum population size and consumed nitrogen much more quickly than strains ARM and TTA. Likewise, the strains PDM and RVA were also the greatest nitrogen demanders. Thus, we can conclude that these differences in nitrogen demand positively correlated with higher growth rate and higher nitrogen uptake rate. The most direct effect of employing an adequate nitrogen concentration is the increase in biomass, which involves a higher fermentation rate. However, the impact of nitrogen on fermentation rate is not exclusively due to the increase in biomass because the strain TTA, which showed the worst growth behavior, had the best fermentation activity. Some strains may adapt a strategy whereby fewer cells with higher metabolic activity are produced. Regarding the nitrogen source used, all the strains showed the better and worse fermentation performance with arginine and ammonium, respectively. Copyright © 2012 Elsevier Ltd. All rights reserved.

The Antarctic yeast Candida sake: Understanding cold metabolism impact on wine.

PubMed

Ballester-Tomás, Lidia; Prieto, Jose A; Gil, Jose V; Baeza, Marcelo; Randez-Gil, Francisca

2017-03-20

Current winemaking trends include low-temperature fermentations and using non-Saccharomyces yeasts as the most promising tools to produce lower alcohol and increased aromatic complexity wines. Here we explored the oenological attributes of a C. sake strain, H14Cs, isolated in the sub-Antarctic region. As expected, the cold sea water yeast strain showed greater cold growth, Na + -toxicity resistance and freeze tolerance than the S. cerevisiae QA23 strain, which we used as a commercial wine yeast control. C. sake H14Cs was found to be more sensitive to ethanol. The fermentation trials of low-sugar content must demonstrated that C. sake H14Cs allowed the cold-induced lag phase of growth to be eliminated and also notably reduced the ethanol (-30%) and glycerol (-50%) content in wine. Instead C. sake produced sorbitol as a compatible osmolyte. Finally, the inspection of the main wine volatile compounds revealed that C. sake produced more higher alcohols than S. cerevisiae. In conclusion, our work evidences that using the Antarctic C. sake H14Cs yeast improves low-temperature must fermentations and has the potential to provide a wine with less ethanol and also particular attributes. Copyright © 2017 Elsevier B.V. All rights reserved.

Construction of novel Saccharomyces cerevisiae strains for bioethanol active dry yeast (ADY) production.

PubMed

Zheng, Daoqiong; Zhang, Ke; 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.

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

Novel endophytic yeast Rhodotorula mucilaginosa strain PTD3 II: production of xylitol and ethanol in the presence of inhibitors.

PubMed

Vajzovic, Azra; Bura, Renata; Kohlmeier, Kevin; Doty, Sharon L

2012-10-01

A systematic study was conducted characterizing the effect of furfural, 5-hydroxymethylfurfural (5-HMF), and acetic acid concentration on the production of xylitol and ethanol by a novel endophytic yeast, Rhodotorula mucilaginosa strain PTD3. The influence of different inhibitor concentrations on the growth and fermentation abilities of PTD3 cultivated in synthetic nutrient media containing 30 g/l xylose or glucose were measured during liquid batch cultures. Concentrations of up to 5 g/l of furfural stimulated production of xylitol to 77 % of theoretical yield (10 % higher compared to the control) by PTD3. Xylitol yields produced by this yeast were not affected in the presence of 5-HMF at concentrations of up to 3 g/l. At higher concentrations of furfural and 5-HMF, xylitol and ethanol yields were negatively affected. The higher the concentration of acetic acid present in a media, the higher the ethanol yield approaching 99 % of theoretical yield (15 % higher compared to the control) was produced by the yeast. At all concentrations of acetic acid tested, xylitol yield was lowered. PTD3 was capable of metabolizing concentrations of 5, 15, and 5 g/l of furfural, 5-HMF, and acetic acid, respectively. This yeast would be a potent candidate for the bioconversion of lignocellulosic sugars to biochemicals given that in the presence of low concentrations of inhibitors, its xylitol and ethanol yields are stimulated, and it is capable of metabolizing pretreatment degradation products.

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.

A Novel Strategy to Construct Yeast Saccharomyces cerevisiae Strains for Very High Gravity Fermentation

PubMed Central

Liu, Tianzhe; Wang, Pinmei; Zhao, Wenpeng; Zhu, Muyuan; Jiang, Xinhang; Zhao, Yuhua; Wu, Xuechang

2012-01-01

Very high gravity (VHG) fermentation is aimed to considerably increase both the fermentation rate and the ethanol concentration, thereby reducing capital costs and the risk of bacterial contamination. This process results in critical issues, such as adverse stress factors (ie., osmotic pressure and ethanol inhibition) and high concentrations of metabolic byproducts which are difficult to overcome by a single breeding method. In the present paper, a novel strategy that combines metabolic engineering and genome shuffling to circumvent these limitations and improve the bioethanol production performance of Saccharomyces cerevisiae strains under VHG conditions was developed. First, in strain Z5, which performed better than other widely used industrial strains, the gene GPD2 encoding glycerol 3-phosphate dehydrogenase was deleted, resulting in a mutant (Z5ΔGPD2) with a lower glycerol yield and poor ethanol productivity. Second, strain Z5ΔGPD2 was subjected to three rounds of genome shuffling to improve its VHG fermentation performance, and the best performing strain SZ3-1 was obtained. Results showed that strain SZ3-1 not only produced less glycerol, but also increased the ethanol yield by up to 8% compared with the parent strain Z5. Further analysis suggested that the improved ethanol yield in strain SZ3-1 was mainly contributed by the enhanced ethanol tolerance of the strain. The differences in ethanol tolerance between strains Z5 and SZ3-1 were closely associated with the cell membrane fatty acid compositions and intracellular trehalose concentrations. Finally, genome rearrangements in the optimized strain were confirmed by karyotype analysis. Hence, a combination of genome shuffling and metabolic engineering is an efficient approach for the rapid improvement of yeast strains for desirable industrial phenotypes. PMID:22363590

A comparative study on the potential of epiphytic yeasts isolated from tropical fruits to produce flavoring compounds.

PubMed

Grondin, Eric; Shum Cheong Sing, Alain; Caro, Yanis; Raherimandimby, Marson; Randrianierenana, Ando Lalaniaina; James, Steve; Nueno-Palop, Carmen; François, Jean Marie; Petit, Thomas

2015-06-16

In recent years, there has been an increasing interest in identifying and characterizing the yeast flora associated with diverse types of habitat because of the many potential desirable technological properties of these microorganisms, especially in food applications. In this study, a total of 101 yeast strains were isolated from the skins of tropical fruits collected in several locations in the South West Indian Ocean. Sequence analysis of the D1/D2 domains of the large subunit (LSU) ribosomal RNA gene identified 26 different species. Among them, two species isolated from the skins of Cape gooseberry and cocoa beans appeared to represent putative new yeast species, as their LSU D1/D2 sequence was only 97.1% and 97.4% identical to that of the yeasts Rhodotorula mucilaginosa and Candida pararugosa, respectively. A total of 52 Volatile Organic Compounds (VOCs) were detected by Head Space Solid Phase Micro Extraction coupled to Gas Chromatography and Mass Spectroscopy (HS-SPME-GC/MS) from the 26 yeast species cultivated on a glucose rich medium. Among these VOCs, 6 uncommon compounds were identified, namely ethyl but-2-enoate, ethyl 2-methylbut-2-enoate (ethyl tiglate), ethyl 3-methylbut-2-enoate, 2-methylpropyl 2-methylbut-2-enoate, butyl 2-methylbut-2-enoate and 3-methylbutyl 2-methylbut-2-enoate, making them possible yeast species-specific markers. In addition, statistical methods such as Principal Component Analysis allowed to associate each yeast species with a specific flavor profile. Among them, Saprochaete suaveolens (syn: Geotrichum fragrans) turned to be the best producer of flavor compounds, with a total of 32 out of the 52 identified VOCs in its flavor profile. Copyright © 2015 Elsevier B.V. All rights reserved.

Novel endophytic yeast Rhodotorula mucilaginosa strain PTD3 I: production of xylitol and ethanol.

PubMed

Bura, Renata; Vajzovic, Azra; Doty, Sharon L

2012-07-01

An endophytic yeast, Rhodotorula mucilaginosa strain PTD3, that was isolated from stems of hybrid poplar was found to be capable of production of xylitol from xylose, of ethanol from glucose, galactose, and mannose, and of arabitol from arabinose. The utilization of 30 g/L of each of the five sugars during fermentation by PTD3 was studied in liquid batch cultures. Glucose-acclimated PTD3 produced enhanced yields of xylitol (67% of theoretical yield) from xylose and of ethanol (84, 86, and 94% of theoretical yield, respectively) from glucose, galactose, and mannose. Additionally, this yeast was capable of metabolizing high concentrations of mixed sugars (150 g/L), with high yields of xylitol (61% of theoretical yield) and ethanol (83% of theoretical yield). A 1:1 glucose:xylose ratio with 30 g/L of each during double sugar fermentation did not affect PTD3's ability to produce high yields of xylitol (65% of theoretical yield) and ethanol (92% of theoretical yield). Surprisingly, the highest yields of xylitol (76% of theoretical yield) and ethanol (100% of theoretical yield) were observed during fermentation of sugars present in the lignocellulosic hydrolysate obtained after steam pretreatment of a mixture of hybrid poplar and Douglas fir. PTD3 demonstrated an exceptional ability to ferment the hydrolysate, overcome hexose repression of xylose utilization with a short lag period of 10 h, and tolerate sugar degradation products. In direct comparison, PTD3 had higher xylitol yields from the mixed sugar hydrolysate compared with the widely studied and used xylitol producer Candida guilliermondii.

Flor Yeast: New Perspectives Beyond Wine Aging

PubMed Central

Legras, Jean-Luc; Moreno-Garcia, Jaime; Zara, Severino; Zara, Giacomo; Garcia-Martinez, Teresa; Mauricio, Juan C.; Mannazzu, Ilaria; Coi, Anna L.; Bou Zeidan, Marc; Dequin, Sylvie; Moreno, Juan; Budroni, Marilena

2016-01-01

The most important dogma in white-wine production is the preservation of the wine aroma and the limitation of the oxidative action of oxygen. In contrast, the aging of Sherry and Sherry-like wines is an aerobic process that depends on the oxidative activity of flor strains of Saccharomyces cerevisiae. Under depletion of nitrogen and fermentable carbon sources, these yeast produce aggregates of floating cells and form an air–liquid biofilm on the wine surface, which is also known as velum or flor. This behavior is due to genetic and metabolic peculiarities that differentiate flor yeast from other wine yeast. This review will focus first on the most updated data obtained through the analysis of flor yeast with -omic tools. Comparative genomics, proteomics, and metabolomics of flor and wine yeast strains are shedding new light on several features of these special yeast, and in particular, they have revealed the extent of proteome remodeling imposed by the biofilm life-style. Finally, new insights in terms of promotion and inhibition of biofilm formation through small molecules, amino acids, and di/tri-peptides, and novel possibilities for the exploitation of biofilm immobilization within a fungal hyphae framework, will be discussed. PMID:27148192

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

PubMed

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

2016-03-17

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.

Reducing patulin contamination in apple juice by using inactive yeast.

PubMed

Yue, Tianli; Dong, Qinfang; Guo, Caixia; Worobo, Randy W

2011-01-01

The mycotoxin, patulin (4-hydroxy-4H-furo[3,2c]pyran-2[6H]-one), is a secondary metabolite produced mainly in rotten parts of fruits and vegetables, most notably apples and apple products, by a wide range of fungal species in the genera Penicillium, Aspergillus, and Byssochlamys. Due to its mutagenic and teratogenic nature and possible health risks to consumers, many countries have regulations to reduce levels of patulin in apple products. In the present study, reduction of patulin contamination in apple juice by using 10 different inactivated yeast strains was assessed. Our results indicated that nearly twofold differences in biomass existed among the 10 yeast strains. Eight of the 10 inactivated yeast strains could provide >50% patulin reduction in apple juice within 24 h, with the highest reduction rate being >72%. Furthermore, juice quality parameters, i.e., degrees Brix, total sugar, titratable acidity, color value, and clarity, of the treated apple juice were very similar to those of the untreated patulin-free juice. Potential applications of using inactivated yeast strain for patulin control are also discussed.

Yeast supplements enhance immune function and performance in food-producing livestock: A review

USDA-ARS?s Scientific Manuscript database

More livestock producers are seeking natural alternatives to antibiotics and antimicrobials, and searching for supplements to enhance growth performance, and overall animal health and well-being. Some of the compounds currently being utilized and studied are live yeast and yeast-based products deriv...

The role of lager beer yeast in oxidative stability of model beer.

PubMed

Berner, T S; Arneborg, N

2012-03-01

In this study, we investigated the relationship between the ability of lager brewing yeast strains to tolerate oxidative stress and their ability to produce oxidative stable model beer. Screening of 21 lager brewing yeast strains against diamide and paraquat showed that the oxidative stress resistance was strain dependent. Fermentation of model wort in European Brewing Convention tubes using three yeast strains with varying oxidative stress resistances resulted in three model beers with different rates of radical formation as measured by electron spin resonance in forced ageing experiments. Interestingly, the strain with the lowest oxidative stress resistance and lowest secretion of thioredoxin, as measured by Western blotting, resulted in the highest uptake of iron, as measured by inductively coupled plasma-mass spectrometry, and the slowest formation of radicals in the model beers. A more oxidative stable beer is not obtained by a more-oxidative-stress-tolerant lager brewing yeast strain, exhibiting a higher secretion of thioredoxin, but rather by a less-oxidative-stress-tolerant strain, exhibiting a higher iron uptake. To obtain lager beers with enhanced oxidative stability, yeast strains should be screened for their low oxidative stress tolerance and/or high ability to take up iron rather than for their high oxidative stress tolerance and/or high ability to secrete thioredoxin. © 2011 The Authors. Letters in Applied Microbiology © 2011 The Society for Applied Microbiology.

Functionality of selected strains of moulds and yeasts from Vietnamese rice wine starters.

PubMed

Dung, N T P; Rombouts, F M; Nout, M J R

2006-06-01

The role of starch-degrading mycelial fungi, and the alcohol production and ethanol tolerance of the yeasts isolated from selected Vietnamese traditional rice wine starters were examined, and optimum conditions for these essential steps in rice wine fermentation were determined. Of pure isolates from Vietnamese rice wine starters, mould strains identified as Amylomyces rouxii, Amylomyces aff. rouxii, Rhizopus oligosporus and Rhizopus oryzae, were superior in starch degradation, glucose production and amyloglucosidase activity during the saccharification of purple glutinous rice. A. rouxii was able to produce up to 25%w/w glucose with an amyloglucosidase activity up to 0.6 Ug(-1) of fermented moulded mass. Five yeast isolates identified as Saccharomyces cerevisiae were selected for their superior alcohol productivity. They were able to deplete a relatively high initial percentage of glucose (20% w/v), forming 8.8% w/v ethanol. The ethanol tolerance of S. cerevisiae in challenge tests was 9-10% w/v, and 13.4% w/v as measured in fed-batch fermentations. Optimum conditions for the saccharification were: incubation for 2 d at 34 degrees C, of steamed rice inoculated with 5 log cfu g(-1); for the alcoholic fermentation 4 d at 28.3 degrees C, of saccharified rice liquid inoculated with 5.5 log cfu mL(-1).

Extracellular enzymatic activities and physiological profiles of yeasts colonizing fruit trees.

PubMed

Molnárová, Jana; Vadkertiová, Renáta; Stratilová, Eva

2014-07-01

Yeasts form a significant and diverse part of the phyllosphere microbiota. Some yeasts that inhabit plants have been found to exhibit extracellular enzymatic activities. The aim of the present study was to investigate the ability of yeasts isolated from leaves, fruits, and blossoms of fruit trees cultivated in Southwest Slovakia to produce extracellular enzymes, and to discover whether the yeasts originating from these plant organs differ from each other in their physiological properties. In total, 92 strains belonging to 29 different species were tested for: extracellular protease, β-glucosidase, lipase, and polygalacturonase activities; fermentation abilities; the assimilation of xylose, saccharose and alcohols (methanol, ethanol, glycerol); and for growth in a medium with 33% glucose. The black yeast Aureobasidium pullulans showed the largest spectrum of activities of all the species tested. Almost 70% of the strains tested demonstrated some enzymatic activity, and more than 90% utilized one of the carbon compounds tested. Intraspecies variations were found for the species of the genera Cryptococcus and Pseudozyma. Interspecies differences of strains exhibiting some enzymatic activities and utilizing alcohols were also noted. The largest proportion of the yeasts exhibited β-glucosidase activity and assimilated alcohols independently of their origin. The highest number of strains positive for all activities tested was found among the yeasts associated with leaves. Yeasts isolated from blossoms assimilated saccharose and D-xylose the most frequently of all the yeasts tested. The majority of the fruit-inhabiting yeasts grew in the medium with higher osmotic pressure. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Simple and Rapid Protocol for Producing Yeast Extract from Saccharomyces cerevisiae Suitable for Preparing Bacterial Culture Media

PubMed Central

Zarei, Omid; Dastmalchi, Siavoush; Hamzeh-Mivehroud, Maryam

2016-01-01

Yeasts, especially Saccharomyces cerevisiae, are one of the oldest organisms with broad spectrum of applications, owing to their unique genetics and physiology. Yeast extract, i.e. the product of yeast cells, is extensively used as nutritional resource in bacterial culture media. The aim of this study was to develop a simple, rapid and cost benefit process to produce the yeast extract. In this procedure mechanical methods such as high temperature and pressure were utilized to produce the yeast extract. The growth of the bacteria feed with the produced yeast extract was monitored in order to assess the quality of the product. The results showed that the quality of the produced yeast extract was very promising concluded from the growth pattern of bacterial cells in media prepared from this product and was comparable with that of the three commercial yeast extracts in terms of bacterial growth properties. One of the main advantages of the current method was that no chemicals and enzymes were used, leading to the reduced production cost. The method is very simple and cost effective, and can be performed in a reasonable time making it suitable for being adopted by research laboratories. Furthermore, it can be scaled up to produce large quantities for industrial applications. PMID:28243289

Yeasts in sustainable bioethanol production: A review.

PubMed

Mohd Azhar, Siti Hajar; Abdulla, Rahmath; Jambo, Siti Azmah; Marbawi, Hartinie; Gansau, Jualang Azlan; Mohd Faik, Ainol Azifa; Rodrigues, Kenneth Francis

2017-07-01

Bioethanol has been identified as the mostly used biofuel worldwide since it significantly contributes to the reduction of crude oil consumption and environmental pollution. It can be produced from various types of feedstocks such as sucrose, starch, lignocellulosic and algal biomass through fermentation process by microorganisms. Compared to other types of microoganisms, yeasts especially Saccharomyces cerevisiae is the common microbes employed in ethanol production due to its high ethanol productivity, high ethanol tolerance and ability of fermenting wide range of sugars. However, there are some challenges in yeast fermentation which inhibit ethanol production such as high temperature, high ethanol concentration and the ability to ferment pentose sugars. Various types of yeast strains have been used in fermentation for ethanol production including hybrid, recombinant and wild-type yeasts. Yeasts can directly ferment simple sugars into ethanol while other type of feedstocks must be converted to fermentable sugars before it can be fermented to ethanol. The common processes involves in ethanol production are pretreatment, hydrolysis and fermentation. Production of bioethanol during fermentation depends on several factors such as temperature, sugar concentration, pH, fermentation time, agitation rate, and inoculum size. The efficiency and productivity of ethanol can be enhanced by immobilizing the yeast cells. This review highlights the different types of yeast strains, fermentation process, factors affecting bioethanol production and immobilization of yeasts for better bioethanol production.

A new β-glucosidase producing yeast for lower-cost cellulosic ethanol production from xylose-extracted corncob residues by simultaneous saccharification and fermentation.

PubMed

Liu, Z Lewis; Weber, Scott A; Cotta, Michael A; Li, Shi-Zhong

2012-01-01

This study reports a new yeast strain of Clavispora NRRL Y-50464 that is able to utilize cellobiose as sole source of carbon and produce sufficient native β-glucosidase enzyme activity for cellulosic ethanol production using SSF. In addition, this yeast is tolerant to the major inhibitors derived from lignocellulosic biomass pre-treatment such as 2-furaldehyde (furfural) and 5-(hydroxymethyl)-2-furaldehyde (HMF), and converted furfural into furan methanol in less than 12h and HMF into furan-2,5-dimethanol within 24h in the presence of 15 mM each of furfural and HMF. Using xylose-extracted corncob residue as cellulosic feedstock, an ethanol production of 23 g/l was obtained using 25% solids loading at 37 °C by SSF without addition of exogenous β-glucosidase. Development of this yeast aids renewable biofuels development efforts for economic consolidated SSF bio-processing. Published by Elsevier Ltd.

Bioflavoring by non-conventional yeasts in sequential beer fermentations.

PubMed

Holt, Sylvester; Mukherjee, Vaskar; Lievens, Bart; Verstrepen, Kevin J; Thevelein, Johan M

2018-06-01

Non-conventional yeast species have great capacity for producing diverse flavor profiles in production of alcoholic beverages, but their potential for beer brewing, in particular in consecutive fermentations with Saccharomyces cerevisiae, has only poorly been explored. We have screened 17 non-conventional yeast species for production of an appealing profile of flavor esters and phenolics in the first phase of alcoholic fermentation, followed by inoculation with S. cerevisiae to complete the fermentation. For measurement of phenolic compounds and their precursors we developed an improved and highly sensitive methodology. The results show that non-conventional yeast species possess promising potential for enhancement of desirable flavors in beer production. Notable examples are increasing isoamyl acetate (fruity, banana flavor) by application of P. kluyverii, augmenting ethyl phenolic compounds (spicy notes) with Brettanomyces species and enhancing 4-vinyl guaiacol (clove-like aroma) with T. delbrueckii. All Pichia strains also produced high levels of ethyl acetate (solvent-like flavor). This might be selectively counteracted by selection of an appropriate S. cerevisiae strain for the second fermentation phase, which lowers total ester profile. Hence, optimization of the process conditions and/or proper strain selection in sequentially inoculated fermentations are required to unlock the full potential for aroma improvement by the non-conventional yeast species. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Yeast lipids from cardoon stalks, stranded driftwood and olive tree pruning residues as possible extra sources of oils for producing biofuels and biochemicals.

PubMed

Tasselli, Giorgia; Filippucci, Sara; Borsella, Elisabetta; D'Antonio, Silvia; Gelosia, Mattia; Cavalaglio, Gianluca; Turchetti, Benedetta; Sannino, Ciro; Onofri, Andrea; Mastrolitti, Silvio; De Bari, Isabella; Cotana, Franco; Buzzini, Pietro

2018-01-01

Some lignocellulosic biomass feedstocks occur in Mediterranean Countries. They are still largely unexploited and cause considerable problems due to the lack of cost-effective harvesting, storage and disposal technologies. Recent studies found that some basidiomycetous yeasts are able to accumulate high amount of intracellular lipids for biorefinery processes (i.e., biofuels and biochemicals). Accordingly, the above biomass feedstocks could be used as carbon sources (after their pre-treatment and hydrolysis) for lipid accumulation by oleaginous yeasts. Cardoon stalks, stranded driftwood and olive tree pruning residues were pre-treated with steam-explosion and enzymatic hydrolysis for releasing free mono- and oligosaccharides. Lipid accumulation tests were performed at two temperatures (20 and 25 °C) using Leucosporidium creatinivorum DBVPG 4794, Naganishia adeliensis DBVPG 5195 and Solicoccozyma terricola DBVPG 5870. S. terricola grown on cardoon stalks at 20 °C exhibited the highest lipid production (13.20 g/l), a lipid yield (28.95%) close to the maximum theoretical value and a lipid composition similar to that found in palm oil. On the contrary, N. adeliensis grown on stranded driftwood and olive tree pruning residues exhibited a lipid composition similar to those of olive and almonds oils. A predictive evaluation of the physical properties of the potential biodiesel obtainable by lipids produced by tested yeast strains has been reported and discussed. Lipids produced by some basidiomycetous yeasts grown on Mediterranean lignocellulosic biomass feedstocks could be used as supplementary sources of oils for producing biofuels and biochemicals.

Detection of maltose fermentation genes in the baking yeast strains of Saccharomyces cerevisiae.

PubMed

Oda, Y; Tonomura, K

1996-10-01

The presence of any one of the five unlinked MAL loci (MAL1, MAL2, MAL3, MAL4 and MAL6) confers the ability to ferment maltose on the yeast Saccharomyces cerevisiae. Each locus is composed of three genes encoding maltose permease, alpha-glucosidase and MAL activator. Chromosomal DNA of seven representative baking strains has been separated by pulse-field gel electrophoresis and probed with three genes in MAL6 locus. The DNA bands to which all of the three MAL-derived probes simultaneously hybridized were chromosome VII carrying MAL1 in all of the strains tested, chromosome XI carrying MAL4 in six strains, chromosome III carrying MAL2 in three strains and chromosomes II and VIII carrying MAL3 and MAL6, respectively, in the one strain. The number of MAL loci in baking strains was comparable to those of brewing strains.

Diversity of yeast strains of the genus Hanseniaspora in the winery environment: What is their involvement in grape must fermentation?

PubMed

Grangeteau, Cédric; Gerhards, Daniel; Rousseaux, Sandrine; von Wallbrunn, Christian; Alexandre, Hervé; Guilloux-Benatier, Michèle

2015-09-01

Isolated yeast populations of Chardonnay grape must during spontaneous fermentation were compared to those isolated on grape berries and in a winery environment before the arrival of the harvest (air, floor, winery equipment) and in the air through time. Two genera of yeast, Hanseniaspora and Saccharomyces, were isolated in grape must and in the winery environment before the arrival of the harvest but not on grape berries. The genus Hanseniaspora represented 27% of isolates in the must and 35% of isolates in the winery environment. The isolates of these two species were discriminated at the strain level by Fourier transform infrared spectroscopy. The diversity of these strains observed in the winery environment (26 strains) and in must (12 strains) was considerable. 58% of the yeasts of the genus Hanseniaspora isolated in the must corresponded to strains present in the winery before the arrival of the harvest. Although the proportion and number of strains of the genus Hanseniaspora decreased during fermentation, some strains, all from the winery environment, subsisted up to 5% ethanol content. This is the first time that the implantation in grape must of populations present in the winery environment has been demonstrated for a non-Saccharomyces genus. Copyright © 2015 Elsevier Ltd. All rights reserved.

Breeding research on sake yeasts in Japan: history, recent technological advances, and future perspectives.

PubMed

Kitagaki, Hiroshi; Kitamoto, Katsuhiko

2013-01-01

Sake is an alcoholic beverage of Japan, with a tradition lasting more than 1,300 years; it is produced from rice and water by fermenting with the koji mold Aspergillus oryzae and sake yeast Saccharomyces cerevisiae. Breeding research on sake yeasts was originally developed in Japan by incorporating microbiological and genetic research methodologies adopted in other scientific areas. Since the advent of a genetic paradigm, isolation of yeast mutants has been a dominant approach for the breeding of favorable sake yeasts. These sake yeasts include (a) those that do not form foams (produced by isolating a mutant that does not stick to foams, thus decreasing the cost of sake production); (b) those that do not produce urea, which leads to the formation of ethyl carbamate, a possible carcinogen (isolated by positive selection in a canavanine-, arginine-, and ornithine-containing medium); (c) those that produce an increased amount of ethyl caproate, an apple-like flavor (produced by isolating a mutant resistant to cerulenin, an inhibitor of fatty-acid synthesis); and (d) those that produce a decreased amount of pyruvate (produced by isolating a mutant resistant to an inhibitor of mitochondrial transport, thus decreasing the amount of diacetyl). Given that sake yeasts perform sexual reproduction, sporulation and mating are potent approaches for their breeding. Recently, the genome sequences of sake yeasts have been determined and made publicly accessible. By utilizing this information, the quantitative trait loci (QTLs) for the brewing characteristics of sake yeasts have been identified, which paves a way to DNA marker-assisted selection of the mated strains. Genetic engineering technologies for experimental yeast strains have recently been established by academic groups, and these technologies have also been applied to the breeding of sake yeasts. Sake yeasts whose genomes have been modified with these technologies correspond to genetically modified organisms (GMOs

Yeast synthetic biology toolbox and applications for biofuel production.

PubMed

Tsai, Ching-Sung; Kwak, Suryang; Turner, Timothy L; Jin, Yong-Su

2015-02-01

Yeasts are efficient biofuel producers with numerous advantages outcompeting bacterial counterparts. While most synthetic biology tools have been developed and customized for bacteria especially for Escherichia coli, yeast synthetic biological tools have been exploited for improving yeast to produce fuels and chemicals from renewable biomass. Here we review the current status of synthetic biological tools and their applications for biofuel production, focusing on the model strain Saccharomyces cerevisiae We describe assembly techniques that have been developed for constructing genes, pathways, and genomes in yeast. Moreover, we discuss synthetic parts for allowing precise control of gene expression at both transcriptional and translational levels. Applications of these synthetic biological approaches have led to identification of effective gene targets that are responsible for desirable traits, such as cellulosic sugar utilization, advanced biofuel production, and enhanced tolerance against toxic products for biofuel production from renewable biomass. Although an array of synthetic biology tools and devices are available, we observed some gaps existing in tool development to achieve industrial utilization. Looking forward, future tool development should focus on industrial cultivation conditions utilizing industrial strains. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permission@oup.com.

Fermentation performances and aroma production of non-conventional wine yeasts are influenced by nitrogen preferences.

PubMed

Rollero, Stéphanie; Bloem, Audrey; Ortiz-Julien, Anne; Camarasa, Carole; Divol, Benoit

2018-05-07

Saccharomyces cerevisiae is currently the most important yeast involved in food fermentations, particularly in oenology. However, several other yeast species occur naturally in grape must that are highly promising for diversifying and improving the aromatic profile of wines. If the nitrogen requirement of S. cerevisiae has been described in detail, those of non-Saccharomyces yeasts remain poorly studied despite their increasingly widespread use in winemaking. With a view to improving the use of non-Saccharomyces yeasts in winemaking, we explored the fermentation performances, the utilization of nitrogen sources and the volatile compound production of ten strains of non-conventional yeasts in pure culture. Two different conditions were tested: one mimicking the grape juice's nitrogen composition and one with all the nitrogen sources at the same level. We highlighted the diversity in terms of nitrogen preference and amount consumed among the yeast strains. Some nitrogen sources (arginine, glutamate, glycine, tryptophan and GABA) displayed the largest variations between strains throughout the fermentation. Several non-Saccharomyces strains produced important aroma compounds such as higher alcohols, acetate and ethyl esters in significantly higher quantities than S. cerevisiae.

Investigating flavour characteristics of British ale yeasts: techniques, resources and opportunities for innovation

PubMed Central

Parker, Neva; James, Steve; Dicks, Jo; Bond, Chris; Nueno-Palop, Carmen; White, Chris; Roberts, Ian N

2015-01-01

Five British ale yeast strains were subjected to flavour profiling under brewery fermentation conditions in which all other brewing parameters were kept constant. Significant variation was observed in the timing and quantity of flavour-related chemicals produced. Genetic tests showed no evidence of hybrid origins in any of the strains, including one strain previously reported as a possible hybrid of Saccharomyces cerevisiae and S. bayanus. Variation maintained in historical S. cerevisiae ale yeast collections is highlighted as a potential source of novelty in innovative strain improvement for bioflavour production. Copyright © 2014 John Wiley & Sons, Ltd. PMID:25361168

Detection and identification of wild yeasts in Champús, a fermented Colombian maize beverage.

PubMed

Osorio-Cadavid, Esteban; Chaves-López, Clemencia; Tofalo, Rosanna; Paparella, Antonello; Suzzi, Giovanna

2008-09-01

The aim of this study was to identify and characterise the predominant yeasts in Champús, a traditional Colombian cereal-based beverage with a low alcoholic content. Samples of Champús from 20 production sites in the Cauca Valley region were analysed. A total of 235 yeast isolates were identified by conventional microbiological analyses and by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) of ITS1-5.8S rDNA-ITS2. The dominant species were: Saccharomyces cerevisiae, Issatchenkia orientalis, Pichia fermentans, Pichia kluyveri var. kluyveri, Zygosaccharomyces fermentati, Torulospora delbruekii, Galactomyces geotrichum and Hanseniaspora spp. Model Champús systems were inoculated with single strains of some isolated sporogenus species and the aromatic profiles were analysed by SPME. Analysis of data showed that Champús strains produced high amounts of esters. The aromatic compounds produced by Saccharomyces and non-Saccharomyces yeasts from Champús can exert a relevant influence on the sensory characteristics of the fermented beverage. The Champús strains could thus represent an important source for new yeast biotypes with potential industrial applications.

Glycerol production by fermenting yeast cells is essential for optimal bread dough fermentation.

PubMed

Aslankoohi, Elham; Rezaei, Mohammad Naser; Vervoort, Yannick; Courtin, Christophe M; Verstrepen, Kevin J

2015-01-01

Glycerol is the main compatible solute in yeast Saccharomyces cerevisiae. When faced with osmotic stress, for example during semi-solid state bread dough fermentation, yeast cells produce and accumulate glycerol in order to prevent dehydration by balancing the intracellular osmolarity with that of the environment. However, increased glycerol production also results in decreased CO2 production, which may reduce dough leavening. We investigated the effect of yeast glycerol production level on bread dough fermentation capacity of a commercial bakery strain and a laboratory strain. We find that Δgpd1 mutants that show decreased glycerol production show impaired dough fermentation. In contrast, overexpression of GPD1 in the laboratory strain results in increased fermentation rates in high-sugar dough and improved gas retention in the fermenting bread dough. Together, our results reveal the crucial role of glycerol production level by fermenting yeast cells in dough fermentation efficiency as well as gas retention in dough, thereby opening up new routes for the selection of improved commercial bakery yeasts.

Different response to acetic acid stress in Saccharomyces cerevisiae wild-type and l-ascorbic acid-producing strains.

PubMed

Martani, Francesca; Fossati, Tiziana; Posteri, Riccardo; Signori, Lorenzo; Porro, Danilo; Branduardi, Paola

2013-09-01

Biotechnological processes are of increasing significance for industrial production of fine and bulk chemicals, including biofuels. Unfortunately, under operative conditions microorganisms meet multiple stresses, such as non-optimal pH, temperature, oxygenation and osmotic stress. Moreover, they have to face inhibitory compounds released during the pretreatment of lignocellulosic biomasses, which constitute the preferential substrate for second-generation processes. Inhibitors include furan derivatives, phenolic compounds and weak organic acids, among which acetic acid is one of the most abundant and detrimental for cells. They impair cellular metabolism and growth, reducing the productivity of the process: therefore, the development of robust cell factories with improved production rates and resistance is of crucial importance. Here we show that a yeast strain engineered to endogenously produce vitamin C exhibits an increased tolerance compared to the parental strain when exposed to acetic acid at moderately toxic concentrations, measured as viability on plates. Starting from this evidence, we investigated more deeply: (a) the nature and levels of reactive oxygen species (ROS); (b) the activation of enzymes that act directly as detoxifiers of reactive oxygen species, such as superoxide dismutase (SOD) and catalase, in parental and engineered strains during acetic acid stress. The data indicate that the engineered strain can better recover from stress by limiting ROS accumulation, independently from SOD activation. The engineered yeast can be proposed as a model for further investigating direct and indirect mechanism(s) by which an antioxidant can rescue cells from organic acid damage; moreover, these studies will possibly provide additional targets for further strain improvements. Copyright © 2013 John Wiley & Sons, Ltd.

A Wickerhamomyces anomalus Killer Strain in the Malaria Vector Anopheles stephensi

PubMed Central

Valzano, Matteo; Damiani, Claudia; Epis, Sara; Gabrielli, Maria Gabriella; Conti, Stefania; Polonelli, Luciano; Bandi, Claudio; Favia, Guido; Ricci, Irene

2014-01-01

The yeast Wickerhamomyces anomalus has been investigated for several years for its wide biotechnological potential, especially for applications in the food industry. Specifically, the antimicrobial activity of this yeast, associated with the production of Killer Toxins (KTs), has attracted a great deal of attention. The strains of W. anomalus able to produce KTs, called “killer” yeasts, have been shown to be highly competitive in the environment. Different W. anomalus strains have been isolated from diverse habitats and recently even from insects. In the malaria mosquito vector Anopheles stephensi these yeasts have been detected in the midgut and gonads. Here we show that the strain of W. anomalus isolated from An. stephensi, namely WaF17.12, is a killer yeast able to produce a KT in a cell-free medium (in vitro) as well as in the mosquito body (in vivo). We showed a constant production of WaF17.12-KT over time, after stimulation of toxin secretion in yeast cultures and reintroduction of the activated cells into the mosquito through the diet. Furthermore, the antimicrobial activity of WaF17.12-KT has been demonstrated in vitro against sensitive microbes, showing that strain WaF17.12 releases a functional toxin. The mosquito-associated yeast WaF17.12 thus possesses an antimicrobial activity, which makes this yeast worthy of further investigations, in view of its potential as an agent for the symbiotic control of malaria. PMID:24788884

Phenotypic characterisation of Saccharomyces spp. yeast for tolerance to stresses encountered during fermentation of lignocellulosic residues to produce bioethanol

PubMed Central

2014-01-01

Background During industrial fermentation of lignocellulose residues to produce bioethanol, microorganisms are exposed to a number of factors that influence productivity. These include inhibitory compounds produced by the pre-treatment processes required to release constituent carbohydrates from biomass feed-stocks and during fermentation, exposure of the organisms to stressful conditions. In addition, for lignocellulosic bioethanol production, conversion of both pentose and hexose sugars is a pre-requisite for fermentative organisms for efficient and complete conversion. All these factors are important to maximise industrial efficiency, productivity and profit margins in order to make second-generation bioethanol an economically viable alternative to fossil fuels for future transport needs. Results The aim of the current study was to assess Saccharomyces yeasts for their capacity to tolerate osmotic, temperature and ethanol stresses and inhibitors that might typically be released during steam explosion of wheat straw. Phenotypic microarray analysis was used to measure tolerance as a function of growth and metabolic activity. Saccharomyces strains analysed in this study displayed natural variation to each stress condition common in bioethanol fermentations. In addition, many strains displayed tolerance to more than one stress, such as inhibitor tolerance combined with fermentation stresses. Conclusions Our results suggest that this study could identify a potential candidate strain or strains for efficient second generation bioethanol production. Knowledge of the Saccharomyces spp. strains grown in these conditions will aid the development of breeding programmes in order to generate more efficient strains for industrial fermentations. PMID:24670111

Biotechnological Applications of Dimorphic Yeasts

NASA Astrophysics Data System (ADS)

Doiphode, N.; Joshi, C.; Ghormade, V.; Deshpande, M. V.

The dimorphic yeasts have the equilibrium between spherical growth (budding) and polarized (hyphal or pseudohyphal tip elongation) which can be triggered by change in the environmental conditions. The reversible growth phenomenon has made dimorphic yeasts as an useful model to understand fungal evolution and fungal differentiation, in general. In nature dimorphism is clearly evident in plant and animal fungal pathogens, which survive and most importantly proliferate in the respective hosts. However, number of organisms with no known pathogenic behaviour also show such a transition, which can be exploited for the technological applications due to their different biochemical make up under different morphologies. For instance, chitin and chitosan production using dimorphic Saccharomyces, Mucor, Rhizopus and Benjaminiella, oil degradation and biotransformation with yeast-form of Yarrowia species, bioremediation of organic pollutants, exopolysac-charide production by yeast-phase of Aureobasidium pullulans, to name a few. Myrothecium verrucaria can be used for seed dressing in its yeast form and it produces a mycolytic enzyme complex in its hyphal-form for the biocontrol of fungal pathogens, while Beauveria bassiana and other entomopathogens kill the insect pest by producing yeast- like cells in the insect body. The form-specific expression of protease, chitinase, lipase, ornithine decarboxylase, glutamate dehydrogenases, etc. make Benjaminiella poitrasii, Basidiobolus sp., and Mucor rouxii strains important in bioremediation, nanobiotechnology, fungal evolution and other areas.

Candida konsanensis sp. nov., a new yeast species isolated from Jasminum adenophyllum in Thailand with potentially carboxymethyl cellulase-producing capability.

PubMed

Sarawan, Somporn; Mahakhan, Polson; Jindamorakot, Sasitorn; Vichitphan, Kanit; Vichitphan, Sukanda; Sawaengkaew, Jutaporn

2013-08-01

A new yeast species (KKU-FW10) belonging to the Candida genus was isolated from Jasminum adenophyllum in the Plant Genetic Conservation Project under The Royal Initiative of Her Royal Highness Princess Maha Chakri Sirindhorn area, Chulabhorn Dam, Konsan district within Chaiyaphum province in Thailand. The strain was identified via analysis of nucleotide sequences from the D1/D2 domain of 26S ribosomal DNA and based on its morphological, physiological and biochemical characteristics. The sequence obtained from yeast isolate KKU-FW10 was 97 percent identical to that of Candida chanthaburiensis (GenBank accession number AB500861.1), with 506/517 (nucleotides identity/total nucleotides) matching nucleotides, nine substitutions and two gaps being detected. This species belonged to the Candida clade. Regarding morphological characteristics, isolate KKU-FW10 presents cream-colored butyrous colonies, vegetative reproduction through budding and, round cells without filaments or ascospores. The major ubiquinone detected was Q-9. The above results suggest that isolate KKU-FW10 is a new member of the genus Candida, and the name Candida konsanensis is proposed for this yeast. The type strain of the new species is KKU-FW10(T) (= BCC 52588(T), = NBRC 109082(T), = CBS 12666(T)). In addition, this KKU-FW10 could potentially produce 58.24 Units/ml of carboxymethyl cellulase when it was cultured in YP broth containing 1.0 % carboxymethyl cellulose for 24 h.

Complete Genome Sequence of Kluyveromyces lactis Strain GG799, a Common Yeast Host for Heterologous Protein Expression

PubMed Central

Chuzel, Léa; Ganatra, Mehul B.; Schermerhorn, Kelly M.; Gardner, Andrew F.; Anton, Brian P.

2017-01-01

ABSTRACT We report the genome sequence of the dairy yeast Kluyveromyces lactis strain GG799 obtained using the Pacific Biosciences RS II platform. K. lactis strain GG799 is a common host for the expression of proteins at both laboratory and industrial scales. PMID:28751387

Screening for new brewing yeasts in the non-Saccharomyces sector with Torulaspora delbrueckii as model.

PubMed

Michel, Maximilian; Kopecká, Jana; Meier-Dörnberg, Tim; Zarnkow, Martin; Jacob, Fritz; Hutzler, Mathias

2016-04-01

This study describes a screening system for future brewing yeasts focusing on non-Saccharomyces yeasts. The aim was to find new yeast strains that can ferment beer wort into a respectable beer. Ten Torulaspora delbrueckii strains were put through the screening system, which included sugar utilization tests, hop resistance tests, ethanol resistance tests, polymerase chain reaction fingerprinting, propagation tests, amino acid catabolism and anabolism, phenolic off-flavour tests and trial fermentations. Trial fermentations were analysed for extract reduction, pH drop, yeast concentration in bulk fluid and fermentation by-products. All investigated strains were able to partly ferment wort sugars and showed high tolerance to hop compounds and ethanol. One of the investigated yeast strains fermented all the wort sugars and produced a respectable fruity flavour and a beer of average ethanol content with a high volatile flavour compound concentration. Two other strains could possibly be used for pre-fermentation as a bio-flavouring agent for beers that have been post-fermented by Saccharomyces strains as a consequence of their low sugar utilization but good flavour-forming properties. Copyright © 2015 John Wiley & Sons, Ltd.

Comparative study on fermentation performance in the genome shuffled Candida versatilis and wild-type salt tolerant yeast strain.

PubMed

Qi, Wei; Guo, Hong-Lian; Wang, Chun-Ling; Hou, Li-Hua; Cao, Xiao-Hong; Liu, Jin-Fu; Lu, Fu-Ping

2017-01-01

The fermentation performance of a genome-shuffled strain of Candida versatilis S3-5, isolated for improved tolerance to salt, and wild-type (WT) strain were analysed. The fermentation parameters, such as growth, reducing sugar, ethanol, organic acids and volatile compounds, were detected during soy sauce fermentation process. The results showed that ethanol produced by the genome shuffled strain S3-5 was increasing at a faster rate and to a greater extent than WT. At the end of the fermentation, malic acid, citric acid and succinic acid formed in tricarboxylic acid cycle after S3-5 treatment elevated by 39.20%, 6.85% and 17.09% compared to WT, respectively. Moreover, flavour compounds such as phenethyl acetate, ethyl vanillate, ethyl acetate, isoamyl acetate, ethyl myristate, ethyl pentadecanoate, ethyl palmitate and phenylacetaldehyde produced by S3-5 were 2.26, 2.12, 2.87, 34.41, 6.32, 13.64, 2.23 and 78.85 times as compared to WT. S3-5 exhibited enhanced metabolic ability as compared to the wild-type strain, improved conversion of sugars to ethanol, metabolism of organic acid and formation of volatile compounds, especially esters, Moreover, S3-5 might be an ester-flavour type salt-tolerant yeast. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Metabolic Engineering of Oleaginous Yeasts for Fatty Alcohol Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wei; Wei, Hui; Knoshaug, Eric

To develop pathways for advanced biological upgrading of sugars to hydrocarbons, we are seeking biological approaches to produce high carbon efficiency intermediates amenable to separations and catalytic upgrading to hydrocarbon fuels. In this study, we successfully demonstrated fatty alcohol production by oleaginous yeasts Yarrowia lipolytica and Lipomyces starkeyi by expressing a bacteria-derived fatty acyl-CoA reductase (FAR). Moreover, we find higher extracellular distribution of fatty alcohols produced by FAR-expressing L. starkeyi strain as compared to Y. lipolytica strain, which would benefit the downstream product recovery process. In both oleaginous yeasts, long chain length saturated fatty alcohols were predominant, accounting for moremore » than 85% of the total fatty alcohols produced. To the best of our knowledge, this is the first report of fatty alcohol production in L. starkeyi. Taken together, our work demonstrates that in addition to Y. lipolytica, L. starkeyi can also serve as a platform organism for production of fatty acid-derived biofuels and bioproducts via metabolic engineering. We believe strain and process development both will significantly contribute to our goal of producing scalable and cost-effective fatty alcohols from renewable biomass.« less

Genome dynamics and evolution in yeasts: A long-term yeast-bacteria competition experiment

PubMed Central

Katz, Michael; Knecht, Wolfgang; Compagno, Concetta; Piškur, Jure

2018-01-01

There is an enormous genetic diversity evident in modern yeasts, but our understanding of the ecological basis of such diversifications in nature remains at best fragmented so far. Here we report a long-term experiment mimicking a primordial competitive environment, in which yeast and bacteria co-exist and compete against each other. Eighteen yeasts covering a wide phylogenetic background spanning approximately 250 million years of evolutionary history were used to establish independent evolution lines for at most 130 passages. Our collection of hundreds of modified strains generated through such a rare two-species cross-kingdom competition experiment re-created the appearance of large-scale genomic rearrangements and altered phenotypes important in the diversification history of yeasts. At the same time, the methodology employed in this evolutionary study would also be a non-gene-technological method of reprogramming yeast genomes and then selecting yeast strains with desired traits. Cross-kingdom competition may therefore be a method of significant value to generate industrially useful yeast strains with new metabolic traits. PMID:29624585

Influence of gamma radiation on ethanol production from yeast.

PubMed

Del-Mastro, N L; Gimenes, J J; Villavicencio, A L

1988-01-01

The effect of up to 6,000 Gray (Gy; 1 Gy = 1 J/k) 60Co gamma irradiation on the fermentative capacity of two strains of yeast cells is reported. Ethanol production by the irradiated cells was unchanged for both strains at 3,000 Gy and reduced 43% for only one strain at 6,000 Gy in spite of a marked decrease in viability at higher doses (2-8% at 3,000 Gy and 0.01% at 6,000 Gy). These results suggest that the yeast fermentation system for converting sugar to alcohol is a relatively radioresistant process and not inhibited by the stable by-products produced during irradiation. Furthermore, these data indicate that radiation polymerization for immobilizing these cells should not interfere with their fermentation capacity.

Characterization of pectinase activity for enology from yeasts occurring in Argentine Bonarda grape.

PubMed

Merín, María Gabriela; Martín, María Carolina; Rantsiou, Kalliopi; Cocolin, Luca; de Ambrosini, Vilma Inés Morata

2015-01-01

Pectinolytic enzymes are greatly important in winemaking due to their ability to degrade pectic polymers from grape, contributing to enhance process efficiency and wine quality. This study aimed to analyze the occurrence of pectinolytic yeasts during spontaneous fermentation of Argentine Bonarda grape, to select yeasts that produce extracellular pectinases and to characterize their pectinolytic activity under wine-like conditions. Isolated yeasts were grouped using PCR-DGGE and identified by partial sequencing of 26S rRNA gene. Isolates comprised 7 genera, with Aureobasidium pullulans as the most predominant pectinolytic species, followed by Rhodotorula dairenensis and Cryptococcus saitoi. No pectinolytic activity was detected among ascomycetous yeasts isolated on grapes and during fermentation, suggesting a low occurrence of pectinolytic yeast species in wine fermentation ecosystem. This is the first study reporting R. dairenensis and Cr. saitoi species with pectinolytic activity. R. dairenensis GM-15 produced pectinases that proved to be highly active at grape pH, at 12 °C, and under ethanol and SO2 concentrations usually found in vinifications (pectinase activity around 1.1 U/mL). This strain also produced cellulase activity at 12 °C and pH 3.5, but did not produce β-glucosidase activity under these conditions. The strain showed encouraging enological properties for its potential use in low-temperature winemaking.

Characterization of pectinase activity for enology from yeasts occurring in Argentine Bonarda grape

PubMed Central

Merín, María Gabriela; Martín, María Carolina; Rantsiou, Kalliopi; Cocolin, Luca; de Ambrosini, Vilma Inés Morata

2015-01-01

Pectinolytic enzymes are greatly important in winemaking due to their ability to degrade pectic polymers from grape, contributing to enhance process efficiency and wine quality. This study aimed to analyze the occurrence of pectinolytic yeasts during spontaneous fermentation of Argentine Bonarda grape, to select yeasts that produce extracellular pectinases and to characterize their pectinolytic activity under wine-like conditions. Isolated yeasts were grouped using PCR-DGGE and identified by partial sequencing of 26S rRNA gene. Isolates comprised 7 genera, with Aureobasidium pullulans as the most predominant pectinolytic species, followed by Rhodotorula dairenensis and Cryptococcus saitoi. No pectinolytic activity was detected among ascomycetous yeasts isolated on grapes and during fermentation, suggesting a low occurrence of pectinolytic yeast species in wine fermentation ecosystem. This is the first study reporting R. dairenensis and Cr. saitoi species with pectinolytic activity. R. dairenensis GM-15 produced pectinases that proved to be highly active at grape pH, at 12 °C, and under ethanol and SO2 concentrations usually found in vinifications (pectinase activity around 1.1 U/mL). This strain also produced cellulase activity at 12 °C and pH 3.5, but did not produce β-glucosidase activity under these conditions. The strain showed encouraging enological properties for its potential use in low-temperature winemaking. PMID:26413065

Engineering baker's yeast: room for improvement.

PubMed

Randez-Gil, F; Sanz, P; Prieto, J A

1999-06-01

Bread making is one of the oldest food-manufacturing processes. However, it is only in the past few years that recombinant-DNA technology has led to dramatic changes in formulation, ingredients or processing conditions. New strains of baker's yeast that produce CO2 more rapidly, are more resistant to stress or produce proteins or metabolites that can modify bread flavour, dough rheology or shelf-life are now emerging.

Diversity of epothilone producers among Sorangium strains in producer-positive soil habitats.

PubMed

Li, Shu-Guang; Zhao, Lin; Han, Kui; Li, Peng-Fei; Li, Zhi-Feng; Hu, Wei; Liu, Hong; Wu, Zhi-Hong; Li, Yue-Zhong

2014-03-01

Large-scale surveys show that the anti-tumour compounds known as epothilones are produced by only a small proportion of Sorangium strains, thereby greatly hampering the research and development of these valuable compounds. In this study, to investigate the niche diversity of epothilone-producing Sorangium strains, we re-surveyed four soil samples where epothilone producers were previously found. Compared with the < 2.5% positive strains collected from different places, epothilone producers comprised 25.0-75.0% of the Sorangium isolates in these four positive soil samples. These sympatric epothilone producers differed not only in their 16S rRNA gene sequences and morphologies but also in their production of epothilones and biosynthesis genes. A further exploration of 14 soil samples collected from a larger area around a positive site showed a similar high positive ratio of epothilone producers among the Sorangium isolates. The present results suggest that, in an area containing epothilone producers, the long-term genetic variations and refinements resulting from selective pressure form a large reservoir of epothilone-producing Sorangium strains with diverse genetic compositions. © 2013 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

Iterative algorithm-guided design of massive strain libraries, applied to itaconic acid production in yeast.

PubMed

Young, Eric M; Zhao, Zheng; Gielesen, Bianca E M; Wu, Liang; Benjamin Gordon, D; Roubos, Johannes A; Voigt, Christopher A

2018-05-09

Metabolic engineering requires multiple rounds of strain construction to evaluate alternative pathways and enzyme concentrations. Optimizing multigene pathways stepwise or by randomly selecting enzymes and expression levels is inefficient. Here, we apply methods from design of experiments (DOE) to guide the construction of strain libraries from which the maximum information can be extracted without sampling every possible combination. We use Saccharomyces cerevisiae as a host for a novel six-gene pathway to itaconic acid, selected by comparing alternative shunt pathways that bypass the mitochondrial TCA cycle. The pathway is distinctive for the use of acetylating acetaldehyde dehydrogenase to increase cytosolic acetyl-CoA pools, a bacterial enzyme to synthesize citrate in the cytosol, and an itaconic acid exporter. Precise control over the expression of each gene is enabled by a set of promoter-terminator pairs that span a 174-fold range. Two large combinatorial libraries (160 variants, 2.4Mb and 32 variants, 0.6Mb) are designed where the expression levels are selected by statistical methods (I-optimal response surface methodology, full factorial, or Plackett-Burman) with the intent of extracting different types of guiding information after the screen. This is applied to the design of a third library (24 variants, 0.5Mb) intended to alleviate a bottleneck in cis-aconitate decarboxylase (CAD) expression. The top strain produces 815mg/l itaconic acid, a 4-fold improvement over the initial strain achieved by iteratively balancing pathway expression. Including a methylated product in the total, the strain produces 1.3g/l combined itaconic acids. Further, a regression analysis of the libraries reveals the optimal expression level of CAD as well as pairwise interdependencies between genes that result in increased titer and purity of itaconic acid. This work demonstrates adapting algorithmic design strategies to guide automated yeast strain construction and learn

Decreased ethyl carbamate generation during Chinese rice wine fermentation by disruption of CAR1 in an industrial yeast strain.

PubMed

Wu, Dianhui; Li, Xiaomin; Shen, Chao; Lu, Jian; Chen, Jian; Xie, Guangfa

2014-06-16

Saccharomyces cerevisiae metabolizes arginine to ornithine and urea during wine fermentations. In the fermentation of Chinese rice wine, yeast strains of S. cerevisiae do not fully metabolize urea, which will be secreted into the spirits and spontaneously reacts with ethanol to form ethyl carbamate, a potential carcinogenic agent for humans. To block the pathway of urea production, we genetically engineered two haploid strains to reduce the arginase (encoded by CAR1) activity, which were isolated from a diploid industrial Chinese rice wine strain. Finally the engineered haploids with opposite mating type were mated back to diploid strains, obtaining a heterozygous deletion strain (CAR1/car1) and a homozygous defect strain (car1/car1). These strains were compared to the parental industrial yeast strain in Chinese rice wine fermentations and spirit production. The strain with the homozygous CAR1 deletion showed significant reductions of urea and EC in the final spirits in comparison to the parental strain, with the concentration reductions by 86.9% and 50.5% respectively. In addition, EC accumulation was in a much lower tempo during rice wine storage. Moreover, the growth behavior and fermentation characteristics of the engineered diploid strain were similar to the parental strain. Copyright © 2014 Elsevier B.V. All rights reserved.

Exploration of potential baker's yeast from sugarcane juice: optimization and evaluation.

PubMed

Mamun-Or-rashid, A N M; Dash, Biplab Kumar; Chowdhury, Md Nurul Abadin; Waheed, Momtaz Fatima; Pramanik, Md Kamruzzaman

2013-07-01

The present study was carried out to explore baker's yeasts strains from sugarcane juice to assess its potential in laboratory scale production of breads. Collected juice samples were processed for isolation and identification of yeast strains based on standard cultural, morphological and biochemical characteristics. Among the six isolated strains, four (designated as S1, S2, S5 and S6) were identified as Saccharomyces cerevisiae and the rests (designated S3 and S4) were as S. rouxii. When assessing their CO2 production rates as a measure of their baking potential, S6 was found to produce maximum amount of gas (226.67 mm3 mL(-1)) in sucrose broth, whereas gas produced by S2, S1 and S5 were relatively insignificant (170, 136.67 and 86.67 mm3 mL(-1), respectively). No strain was found to produce undesirable H2S gas responsible for off-flavor. Besides, effects of different physicochemical parameters (e.g., pH, temperature, substrate concentration, incubation period, agitation etc.) on the production of yeast cell-mass were studied. Yield of cell mass was indirectly measured by spectrophotometric method at 550 nm. All the test isolates were found to produce maximum cell mass at a pH range of 4.0 to 5.0 in 2 to 4% molasses broth at 30 degrees C after 4 days of incubation. In the laboratory scale production of bread using composite flour, Isolate-S6 formed significant characteristic texture. Considering overall characteristics, Isolate- S6 was found to be satisfactorily potent for baking purpose.

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

Survival of genetically modified and self-cloned strains of commercial baker's yeast in simulated natural environments: environmental risk assessment.

PubMed

Ando, Akira; Suzuki, Chise; Shima, Jun

2005-11-01

Although genetic engineering techniques for baker's yeast might improve the yeast's fermentation characteristics, the lack of scientific data on the survival of such strains in natural environments as well as the effects on human health prevent their commercial use. Disruption of acid trehalase gene (ATH1) improves freeze tolerance, which is a crucial characteristic in frozen-dough baking. In this study, ATH1 disruptants constructed by genetic modification (GM) and self-cloning (SC) techniques were used as models to study such effects because these strains have higher freeze tolerance and are expected to be used commercially. Behavior of the strains in simulated natural environments, namely, in soil and water, was studied by measuring the change in the number of viable cells and in the concentration of DNA that contains ATH1 loci. Measurements were made using a real-time PCR method during 40 days of cultivation. Results showed that the number of viable cells of GM and SC strains decreased in a time-dependent manner and that the decrease rate was nearly equal to or higher than that for wild-type (WT) yeast. For all three strains (SC, GM, and WT) in the two simulated natural environments (water and soil), the DNA remained longer than did viable cells but the decrease patterns of either the DNA or the viable cells of SC and GM strains had tendencies similar to those of the WT strain. In conclusion, disruption of ATH1 by genetic engineering apparently does not promote the survival of viable cells and DNA in natural environments.

Glycerol Production by Fermenting Yeast Cells Is Essential for Optimal Bread Dough Fermentation

PubMed Central

Aslankoohi, Elham; Rezaei, Mohammad Naser; Vervoort, Yannick; Courtin, Christophe M.; Verstrepen, Kevin J.

2015-01-01

Glycerol is the main compatible solute in yeast Saccharomyces cerevisiae. When faced with osmotic stress, for example during semi-solid state bread dough fermentation, yeast cells produce and accumulate glycerol in order to prevent dehydration by balancing the intracellular osmolarity with that of the environment. However, increased glycerol production also results in decreased CO2 production, which may reduce dough leavening. We investigated the effect of yeast glycerol production level on bread dough fermentation capacity of a commercial bakery strain and a laboratory strain. We find that Δgpd1 mutants that show decreased glycerol production show impaired dough fermentation. In contrast, overexpression of GPD1 in the laboratory strain results in increased fermentation rates in high-sugar dough and improved gas retention in the fermenting bread dough. Together, our results reveal the crucial role of glycerol production level by fermenting yeast cells in dough fermentation efficiency as well as gas retention in dough, thereby opening up new routes for the selection of improved commercial bakery yeasts. PMID:25764309

Further Improvement of the Robust Recombinant Saccharomyces Yeast for the Conversion of Lignocellulosic Biomass to Ethanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Nancy W. Y.; Adamec, Jiri; Mosier, Nathan, S.

2011-04-09

Since 1980, the PI’s laboratory at Purdue University has been at the forefront in developing recombinant Saccharomyces yeast for cellulosic ethanol production. Their innovation enabled them to successfully develop the recombinant Saccharomyces yeast strain 424A(LNH-ST) that has been validated by scientists in industry, universities, and National Laboratories. Strain 424A(LNH-ST) has also been used by a company to produce cellulosic ethanol since 2004. Nevertheless, this strain still needs improvement, particularly to achieve high ethanol titer when cellulosic biomass hydrolysates are used for ethanol production. In this project, we were able to carry out a total genetic overhaul of our yeast bymore » carrying out nine different tasks to improve our 424A(LNH-ST) strain. Through these tasks we enabled the yeast to co-ferment arabinose together with other four sugars generally present in all cellulosic biomass. Thus 424A(LNH-ST) can now ferment all five sugars, glucose, xylose, mannose, galactose and arabinose present in any cellulosic biomass. We also successfully used adaptation techniques and direct genetic improvements to develop improved 424A(LNH-ST) strains that are more resistant to acetic acid or ethanol. These are the most significant inhibitors of those commonly present in cellulosic hydrolysates that prevent 424A(LNH-ST) from producing high concentrations of cellulosic ethanol. The acetic acid resistant strain has 89% better xylose utilization in the presence of acetic acid and 25% better overall ethanol yield. The ethanol resistant strain has 250% better ethanol volumetric productivity. The three tasks for improving the main metabolic pathways have all been successfully completed but the impact of these improvements was less dramatic. This demonstrates our yeast already has effective metabolic systems for co-fermenting cellulosic sugars. However, our attempt to improve the yeast to transport xylose and arabinose more efficiently had only limited

Further Improvement of the Robust Recombinant Saccharomyces Yeast for the Conversion of Lignocellulosic Biomass to Ethanol

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ho, Nancy, W. Y.; Adamec, Jiri; Mosier, Nathan, S.

2011-04-07

Since 1980, the PI's laboratory at Purdue University has been at the forefront in developing recombinant Saccharomyces yeast for cellulosic ethanol production. Their innovation enabled them to successfully develop the recombinant Saccharomyces yeast strain 424A(LNH-ST) that has been validated by scientists in industry, universities, and National Laboratories. Strain 424A(LNH-ST) has also been used by a company to produce cellulosic ethanol since 2004. Nevertheless, this strain still needs improvement, particularly to achieve high ethanol titer when cellulosic biomass hydrolysates are used for ethanol production. In this project, we were able to carry out a total genetic overhaul of our yeast bymore » carrying out nine different tasks to improve our 424A(LNH-ST) strain. Through these tasks we enabled the yeast to co-ferment arabinose together with other four sugars generally present in all cellulosic biomass. Thus 424A(LNH-ST) can now ferment all five sugars, glucose, xylose, mannose, galactose and arabinose present in any cellulosic biomass. We also successfully used adaptation techniques and direct genetic improvements to develop improved 424A(LNH-ST) strains that are more resistant to acetic acid or ethanol. These are the most significant inhibitors of those commonly present in cellulosic hydrolysates that prevent 424A(LNH-ST) from producing high concentrations of cellulosic ethanol. The acetic acid resistant strain has 89% better xylose utilization in the presence of acetic acid and 25% better overall ethanol yield. The ethanol resistant strain has 250% better ethanol volumetric productivity. The three tasks for improving the main metabolic pathways have all been successfully completed but the impact of these improvements was less dramatic. This demonstrates our yeast already has effective metabolic systems for co-fermenting cellulosic sugars. However, our attempt to improve the yeast to transport xylose and arabinose more efficiently had only limited success

Technical assessment of cellulosic ethanol production using ß-glucosidase producing yeast Clavispora NRRL Y-50464

USDA-ARS?s Scientific Manuscript database

Reducing the cost of cellulosic ethanol production, especially the use of expensive exogenous cellulose hydrolytic enzymes such as cellulase and ß-glucosidase, is a critical challenge and vital for a sustainable advanced biofuels industry. Here we report a novel ethanologenic yeast strain Clavispora...

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

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 %.

Aroma profiling of an aerated fermentation of natural grape must with selected yeast strains at pilot scale.

PubMed

Tronchoni, Jordi; Curiel, José Antonio; Sáenz-Navajas, María Pilar; Morales, Pilar; de-la-Fuente-Blanco, Arancha; Fernández-Zurbano, Purificación; Ferreira, Vicente; Gonzalez, Ramon

2018-04-01

The use of non-Saccharomyces strains in aerated conditions has proven effective for alcohol content reduction in wine during lab-scale fermentation. The process has been scaled up to 20 L batches, in order to produce lower alcohol wines amenable to sensory analysis. Sequential instead of simultaneous inoculation was chosen to prevent oxygen exposure of Saccharomyces cerevisiae during fermentation, since previous results indicated that this would result in increased acetic acid production. In addition, an adaptation step was included to facilitate non-Saccharomyces implantation in natural must. Wines elaborated with Torulaspora delbrueckii or Metschnikowia pulcherrima in aerated conditions contained less alcohol than control wine (S. cerevisiae, non-aerated). Sensory and aroma analysis revealed that the quality of mixed fermentations was affected by the high levels of some yeast amino acid related byproducts, which suggests that further progress requires a careful selection of non-Saccharomyces strains and the use of specific N-nutrients. Copyright © 2017 Elsevier Ltd. All rights reserved.

Does fingerprinting truly represent the diversity of wine yeasts? A case study with interdelta genotyping of Saccharomyces cerevisiae strains.

PubMed

Pfliegler, W P; Sipiczki, M

2016-12-01

Simple and efficient genotyping methods are widely used to assess the diversity of a large number of microbial strains, e.g. wine yeasts isolated from a specific geographical area or a vintage. Such methods are often also the first to be applied, to decrease the number of strains deemed interesting for a more time-consuming physiological characterization. Here, we aimed to use a physiologically characterized strain collection of 69 Saccharomyces cerevisiae strains from Hungarian wine regions to determine whether geographical origin or physiological similarity can be recovered by clustering the strains with one or two simultaneously used variations of interdelta genotyping. Our results indicate that although a detailed clustering with high resolution can be achieved with this method, the clustering of strains is largely contrasting when different primer sets are used and it does not recover geographical or physiological groups. Genotyping is routinely used for assessing the diversity of a large number of isolates/strains of a single species, e.g. a collection of wine yeasts. We tested the efficiency of interdelta genotyping on a collection of Saccharomyces wine yeasts from four wine regions of Hungary that was previously characterized physiologically. Interdelta fingerprinting recovered neither physiological nor geographical similarities, and in addition, the two different primer pairs widely used for this method showed conflicting and barely comparable results. Thus, this method does not necessarily represent the true diversity of a strain collection, but detailed clustering may be achieved by the combined use of primer sets. © 2016 The Society for Applied Microbiology.

Production, characterization and gene cloning of the extracellular enzymes from the marine-derived yeasts and their potential applications.

PubMed

Chi, Zhenming; Chi, Zhe; Zhang, Tong; Liu, Guanglei; Li, Jing; Wang, Xianghong

2009-01-01

In this review article, the extracellular enzymes production, their properties and cloning of the genes encoding the enzymes from marine yeasts are overviewed. Several yeast strains which could produce different kinds of extracellular enzymes were selected from the culture collection of marine yeasts available in this laboratory. The strains selected belong to different genera such as Yarrowia, Aureobasidium, Pichia, Metschnikowia and Cryptococcus. The extracellular enzymes include cellulase, alkaline protease, aspartic protease, amylase, inulinase, lipase and phytase, as well as killer toxin. The conditions and media for the enzyme production by the marine yeasts have been optimized and the enzymes have been purified and characterized. Some genes encoding the extracellular enzymes from the marine yeast strains have been cloned, sequenced and expressed. It was found that some properties of the enzymes from the marine yeasts are unique compared to those of the homologous enzymes from terrestrial yeasts and the genes encoding the enzymes in marine yeasts are different from those in terrestrial yeasts. Therefore, it is of very importance to further study the enzymes and their genes from the marine yeasts. This is the first review on the extracellular enzymes and their genes from the marine yeasts.

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.

Yeast Monitoring of Wine Mixed or Sequential Fermentations Made by Native Strains from D.O. "Vinos de Madrid" Using Real-Time Quantitative PCR.

PubMed

García, Margarita; Esteve-Zarzoso, Braulio; Crespo, Julia; Cabellos, Juan M; Arroyo, Teresa

2017-01-01

There is an increasing trend toward understanding the impact of non- Saccharomyces yeasts on the winemaking process. Although Saccharomyces cerevisiae is the predominant species at the end of fermentation, it has been recognized that the presence of non- Saccharomyces species during alcoholic fermentation can produce an improvement in the quality and complexity of the final wines. A previous work was developed for selecting the best combinations between S. cerevisiae and five non- Saccharomyces ( Torulaspora delbrueckii, Schizosaccharomyces pombe, Candida stellata, Metschnikowia pulcherrima , and Lachancea thermotolorans ) native yeast strains from D.O. "Vinos de Madrid" at the laboratory scale. The best inoculation strategies between S. cerevisiae and non- Saccharomyces strains were chosen to analyze, by real-time quantitative PCR (qPCR) combined with the use of specific primers, the dynamics of inoculated populations throughout the fermentation process at the pilot scale using the Malvar white grape variety. The efficiency of the qPCR system was verified independently of the samples matrix, founding the inoculated yeast species throughout alcoholic fermentation. Finally, we can validate the positive effect of selected co-cultures in the Malvar wine quality, highlighting the sequential cultures of T. delbrueckii CLI 918/ S. cerevisiae CLI 889 and C. stellata CLI 920/ S. cerevisiae CLI 889 and, mixed and sequential cultures of L. thermotolerans 9-6C combined with S. cerevisiae CLI 889.

Isolation, selection and evaluation of yeasts for use in fermentation of coffee beans by the wet process.

PubMed

de Melo Pereira, Gilberto Vinícius; Soccol, Vanete Thomaz; Pandey, Ashok; Medeiros, Adriane Bianchi Pedroni; Andrade Lara, João Marcos Rodrigues; Gollo, André Luiz; Soccol, Carlos Ricardo

2014-10-01

During wet processing of coffee, the ripe cherries are pulped, then fermented and dried. This study reports an experimental approach for target identification and selection of indigenous coffee yeasts and their potential use as starter cultures during the fermentation step of wet processing. A total of 144 yeast isolates originating from spontaneously fermenting coffee beans were identified by molecular approaches and screened for their capacity to grow under coffee-associated stress conditions. According to ITS-rRNA gene sequencing, Pichia fermentans and Pichia kluyveri were the most frequent isolates, followed by Candida Candida glabrata, quercitrusa, Saccharomyces sp., Pichia guilliermondii, Pichia caribbica and Hanseniaspora opuntiae. Nine stress-tolerant yeast strains were evaluated for their ability to produce aromatic compounds in a coffee pulp simulation medium and for their pectinolytic activity. P. fermentans YC5.2 produced the highest concentrations of flavor-active ester compounds (viz., ethyl acetate and isoamyl acetate), while Saccharomyces sp. YC9.15 was the best pectinase-producing strain. The potential impact of these selected yeast strains to promote flavor development in coffee beverages was investigated for inoculating coffee beans during wet fermentation trials at laboratory scale. Inoculation of a single culture of P. fermentans YC5.2 and co-culture of P. fermentans YC5.2 and Saccharomyces sp. YC9.15 enhanced significantly the formation of volatile aroma compounds during the fermentation process compared to un-inoculated control. The sensory analysis indicated that the flavor of coffee beverages was influenced by the starter cultures, being rated as having the higher sensory scores for fruity, buttery and fermented aroma. This demonstrates a complementary role of yeasts associated with coffee quality through the synthesis of yeast-specific volatile constituents. The yeast strains P. fermentans YC5.2 and Saccharomyces sp. YC9.15 have a great

Survival of commercial yeasts in the winery environment and their prevalence during spontaneous fermentations.

PubMed

Blanco, P; Orriols, I; Losada, A

2011-01-01

Inoculation of active dry yeasts during the wine-making process has become a common practice in most wine-producing regions; this practice may affect the diversity of the indigenous population of Saccharomyces cerevisiae in the winery. The aim of this work was to study the incidence of commercial yeasts in the experimental winery of Estación de Viticultura e Enoloxía de Galicia (EVEGA) and their ability to lead spontaneous fermentations. To do this, 64 spontaneous fermentations were carried out in the experimental cellar of EVEGA over a period of 7 years. Samples were taken from must and at the beginning, vigorous and final stages of fermentation. A representative number of yeast colonies was isolated from each sample. S. cerevisiae strains were characterised by analysis of mitochondrial DNA restriction patterns. The results showed that although more than 40 different strains of S. cerevisiae were identified, only 10 were found as the dominant strain or in codominance with other strains in spontaneous fermentations. The genetic profiles (mtDNA-RFLPs) of eight of these strains were similar to those of different commercial yeasts that had been previously used in the EVEGA cellar. The remaining two strains were autochthonous ones that were able to reach implantation frequencies as high of those of commercial yeasts. These results clearly indicated that commercial wine yeasts were perfectly adapted to survive in EVEGA cellar conditions, and they successfully competed with the indigenous strains of S. cerevisiae, even during spontaneous fermentations. On the other hand, autochthonous dominant strains that presented desirable oenological traits could be of interest to preserve wine typicity.

Enhancement of ethanol fermentation in Saccharomyces cerevisiae sake yeast by disrupting mitophagy function.

PubMed

Shiroma, Shodai; Jayakody, Lahiru Niroshan; Horie, Kenta; Okamoto, Koji; Kitagaki, Hiroshi

2014-02-01

Saccharomyces cerevisiae sake yeast strain Kyokai no. 7 has one of the highest fermentation rates among brewery yeasts used worldwide; therefore, it is assumed that it is not possible to enhance its fermentation rate. However, in this study, we found that fermentation by sake yeast can be enhanced by inhibiting mitophagy. We observed mitophagy in wild-type sake yeast during the brewing of Ginjo sake, but not when the mitophagy gene (ATG32) was disrupted. During sake brewing, the maximum rate of CO2 production and final ethanol concentration generated by the atg32Δ laboratory yeast mutant were 7.50% and 2.12% higher than those of the parent strain, respectively. This mutant exhibited an improved fermentation profile when cultured under limiting nutrient concentrations such as those used during Ginjo sake brewing as well as in minimal synthetic medium. The mutant produced ethanol at a concentration that was 2.76% higher than the parent strain, which has significant implications for industrial bioethanol production. The ethanol yield of the atg32Δ mutant was increased, and its biomass yield was decreased relative to the parent sake yeast strain, indicating that the atg32Δ mutant has acquired a high fermentation capability at the cost of decreasing biomass. Because natural biomass resources often lack sufficient nutrient levels for optimal fermentation, mitophagy may serve as an important target for improving the fermentative capacity of brewery yeasts.

Enhancement of Ethanol Fermentation in Saccharomyces cerevisiae Sake Yeast by Disrupting Mitophagy Function

PubMed Central

Shiroma, Shodai; Jayakody, Lahiru Niroshan; Horie, Kenta; Okamoto, Koji

2014-01-01

Saccharomyces cerevisiae sake yeast strain Kyokai no. 7 has one of the highest fermentation rates among brewery yeasts used worldwide; therefore, it is assumed that it is not possible to enhance its fermentation rate. However, in this study, we found that fermentation by sake yeast can be enhanced by inhibiting mitophagy. We observed mitophagy in wild-type sake yeast during the brewing of Ginjo sake, but not when the mitophagy gene (ATG32) was disrupted. During sake brewing, the maximum rate of CO2 production and final ethanol concentration generated by the atg32Δ laboratory yeast mutant were 7.50% and 2.12% higher than those of the parent strain, respectively. This mutant exhibited an improved fermentation profile when cultured under limiting nutrient concentrations such as those used during Ginjo sake brewing as well as in minimal synthetic medium. The mutant produced ethanol at a concentration that was 2.76% higher than the parent strain, which has significant implications for industrial bioethanol production. The ethanol yield of the atg32Δ mutant was increased, and its biomass yield was decreased relative to the parent sake yeast strain, indicating that the atg32Δ mutant has acquired a high fermentation capability at the cost of decreasing biomass. Because natural biomass resources often lack sufficient nutrient levels for optimal fermentation, mitophagy may serve as an important target for improving the fermentative capacity of brewery yeasts. PMID:24271183

Analysis of Growth Inhibition and Metabolism of Hydroxycinnamic Acids by Brewing and Spoilage Strains of Brettanomyces Yeast.

PubMed

Lentz, Michael; Harris, Chad

2015-10-15

Brettanomyces yeasts are well-known as spoilage organisms in both the wine and beer industries, but also contribute important desirable characters to certain beer styles. These properties are mediated in large part by Brettanomyces ' metabolism of hydroxycinnamic acids (HCAs) present in beverage raw materials. Here we compare growth inhibition by, and metabolism of, HCAs among commercial brewing strains and spoilage strains of B. bruxellensis and B. anomalus . These properties vary widely among the different strains tested and between the HCAs analyzed. Brewing strains showed more efficient metabolism of ferulic acid over p -coumaric acid, a trait not shared among the spoilage strains.

Some Properties of Extracellular Acetylxylan Esterase Produced by the Yeast Rhodotorula mucilaginosa†

PubMed Central

Lee, Hung; To, Rebecca J. B.; Latta, Roger K.; Biely, Peter; Schneider, Henry

1987-01-01

The red yeast Rhodotorula mucilaginosa produced an esterase that accumulated in the culture supernatant on induction with triacetin. The enzyme was specific for substrates bearing an O-acetyl group, but was relatively nonspecific for the rest of the molecule, which could consist of a phenol, a monosaccharide, a polysaccharide, or an aliphatic alcohol. The esterase was more active against acetylxylan and glucose β-d-pentaacetate than were a number of esterases from plant and animal sources, when activities on 4-nitrophenyl acetate were compared. The enzyme exhibited Michaelis-Menten kinetics and was active over a broad pH range (5.5 to 9.2), with an optimum between pH 8 and 10. In addition, the enzyme retained its activity for 2 h at 55°C. The yeast that produced the enzyme did not produce xylanase and, hence, is of interest for the production of acetylxylan esterase that is free of xylanolytic activity. PMID:16347498

Designing industrial yeasts for the consolidated bioprocessing of starchy biomass to ethanol

PubMed Central

Favaro, Lorenzo; Jooste, Tania; Basaglia, Marina; Rose, Shaunita H.; Saayman, Maryna; Görgens, Johann F.; Casella, Sergio; van Zyl, Willem H.

2013-01-01

Consolidated bioprocessing (CBP), which integrates enzyme production, saccharification and fermentation into a one step process, is a promising strategy for the effective ethanol production from cheap lignocellulosic and starchy materials. CBP requires a highly engineered microbial strain able to both hydrolyze biomass with enzymes produced on its own and convert the resulting simple sugars into high-titer ethanol. Recently, heterologous production of cellulose and starch-degrading enzymes has been achieved in yeast hosts, which has realized direct processing of biomass to ethanol. However, essentially all efforts aimed at the efficient heterologous expression of saccharolytic enzymes in yeast have involved laboratory strains and much of this work has to be transferred to industrial yeasts that provide the fermentation capacity and robustness desired for large scale bioethanol production. Specifically, the development of an industrial CBP amylolytic yeast would allow the one-step processing of low-cost starchy substrates into ethanol. This article gives insight in the current knowledge and achievements on bioethanol production from starchy materials with industrial engineered S. cerevisiae strains. PMID:22989992

Whole Genome Comparison Reveals High Levels of Inbreeding and Strain Redundancy Across the Spectrum of Commercial Wine Strains of Saccharomyces cerevisiae

PubMed Central

Borneman, Anthony R.; Forgan, Angus H.; Kolouchova, Radka; Fraser, James A.; Schmidt, Simon A.

2016-01-01

Humans have been consuming wines for more than 7000 yr . For most of this time, fermentations were presumably performed by strains of Saccharomyces cerevisiae that naturally found their way into the fermenting must . In contrast, most commercial wines are now produced by inoculation with pure yeast monocultures, ensuring consistent, reliable and reproducible fermentations, and there are now hundreds of these yeast starter cultures commercially available. In order to thoroughly investigate the genetic diversity that has been captured by over 50 yr of commercial wine yeast development and domestication, whole genome sequencing has been performed on 212 strains of S. cerevisiae, including 119 commercial wine and brewing starter strains, and wine isolates from across seven decades. Comparative genomic analysis indicates that, despite their large numbers, commercial strains, and wine strains in general, are extremely similar genetically, possessing all of the hallmarks of a population bottle-neck, and high levels of inbreeding. In addition, many commercial strains from multiple suppliers are nearly genetically identical, suggesting that the limits of effective genetic variation within this genetically narrow group may be approaching saturation. PMID:26869621

Screening and characterizing of xylanolytic and xylose-fermenting yeasts isolated from the wood-feeding termite, Reticulitermes chinensis

PubMed Central

Xie, Rongrong; Zhou, Feng; Huang, Miao

2017-01-01

The effective fermentation of xylose remains an intractable challenge in bioethanol industry. The relevant xylanase enzyme is also in a high demand from industry for several biotechnological applications that inevitably in recent times led to many efforts for screening some novel microorganisms for better xylanase production and fermentation performance. Recently, it seems that wood-feeding termites can truly be considered as highly efficient natural bioreactors. The highly specialized gut systems of such insects are not yet fully realized, particularly, in xylose fermentation and xylanase production to advance industrial bioethanol technology as well as industrial applications of xylanases. A total of 92 strains from 18 yeast species were successfully isolated and identified from the gut of wood-feeding termite, Reticulitermes chinensis. Of these yeasts and strains, seven were identified for new species: Candida gotoi, Candida pseudorhagii, Hamamotoa lignophila, Meyerozyma guilliermondii, Sugiyamaella sp.1, Sugiyamaella sp. 2, and Sugiyamaella sp.3. Based on the phylogenetic and phenotypic characterization, the type strain of C. pseudorhagii sp. nov., which was originally designated strain SSA-1542T, was the most frequently occurred yeast from termite gut samples, showed the highly xylanolytic activity as well as D-xylose fermentation. The highest xylanase activity was recorded as 1.73 and 0.98 U/mL with xylan or D-xylose substrate, respectively, from SSA-1542T. Among xylanase-producing yeasts, four novel species were identified as D-xylose-fermenting yeasts, where the yeast, C. pseudorhagii SSA-1542T, showed the highest ethanol yield (0.31 g/g), ethanol productivity (0.31 g/L·h), and its fermentation efficiency (60.7%) in 48 h. Clearly, the symbiotic yeasts isolated from termite guts have demonstrated a competitive capability to produce xylanase and ferment xylose, suggesting that the wood-feeding termite gut is a promising reservoir for novel xylanases-producing

Impact of Saccharomyces cerevisiae strains on traditional sparkling wines production.

PubMed

Di Gianvito, Paola; Perpetuini, Giorgia; Tittarelli, Fabrizia; Schirone, Maria; Arfelli, Giuseppe; Piva, Andrea; Patrignani, Francesca; Lanciotti, Rosalba; Olivastri, Lino; Suzzi, Giovanna; Tofalo, Rosanna

2018-07-01

Sparkling wine fermentation is a challenge for yeasts due to the hostile conditions. A phenotype sought in starters is flocculation, because it reduces riddling time. For this reason, six flocculent Saccharomyces cerevisiae wine strains with different flocculation degree and autolytic activity and two commercial strains were tested for traditional sparkling wine production in a winery. Yeast viability, free aminoacids and high molecular weight nitrogen release and physico-chemical composition of sparkling wines were evaluated. Moreover, strains were tested for their aromatic potential. Obtained data revealed that flocculent yeasts presented oenological performances (in terms of fermentation rate, maximum pressure reached, free aminoacids - AAN and high molecular weight nitrogen - HMWN release) similar to the commercial strains. All considered strains were able to complete fermentation and viable cells of all strains were detected in all sparkling wines produced even after 6 months. F6789 and F10471 strains showed slow fermentation kinetics reaching the maximum of pressure at 180 days. Regarding nitrogen compounds release, FI strain was characterized by the highest amount of AAN and HMWN released, followed by F6789. Strains showed a considerable diversification in terms of number and amount of aroma molecules produced and sparkling wines obtained with autochthonous flocculent strains presented a higher amount of alcohols and esters already after 3 months. Further studies are necessary to select starter strains to improve traditional sparkling wines production. Copyright © 2018 Elsevier Ltd. All rights reserved.

Probiotic potentials of yeasts isolated from some cereal-based Nigerian traditional fermented food products.

PubMed

Ogunremi, O R; Sanni, A I; Agrawal, R

2015-09-01

To determine the starter culture and multifunctional potentials of yeast strains from some cereal-based Nigerian traditional fermented food products. Yeast isolates were screened for enzyme production and identified by sequencing the D1/D2 region of 26S rDNA. Pichia kluyveri LKC17, Issatchenkia orientalis OSL11, Pichia kudriavzevii OG32, Pichia kudriavzevii ROM11 and Candida tropicalis BOM21 exhibited the highest protease, lipase and phytase activity. They were selected and further evaluated for gastrointestinal survival and adherence ability. Although strain-specific, they retained viability at 37°C and showed survival at pH 2·0., I. orientalis OSL11 showed the highest survival at 2% bile salts concentration and P. kudriavzevii ROM11 showed the least survival. The yeast strains showed strong autoaggregation ability (81·24-91·85%) and hydrophobicity to n-hexadecane (33·61-42·30%). The highest co-aggregation ability was detected for P. kudriavzevii OG32 and Escherichia coli (71·57%). All the yeast strains removed cholesterol in the range of 49·03-74·05% over 48 h and scavenged for free radicals in methanol reaction system. In this study, we isolated new yeast strains with multifunctional potentials that can be used as functional starter cultures to produce cereal-based probiotic products. The development of probiotic yeast strains as starter culture to improve the quality attributes and confer functional value on cereal-based traditional fermented foods is beneficial. © 2015 The Society for Applied Microbiology.

Expression of a codon-optimized Aspergillus niger pectin methylesterase gene in the methylotrophic yeast Candida boidinii.

PubMed

Kawaguchi, Kosuke; Yurimoto, Hiroya; Sakai, Yasuyoshi

2014-01-01

A codon-optimized Aspergillus niger pectin methylesterase (PME) gene was expressed in the methylotrophic yeast Canidia boidinii. The PME-producing strains showed better growth on pectin than the wild-type strains, suggesting that the PME-producing strains could efficiently utilize methyl ester moieties of pectin. On the other hand, overproduction of PME negatively affected the proliferation of C. boidinii on leaves of Arabidopsis thaliana.

A new beta-glucosidase producing yeast for lower-cost cellulosic ethanol production from xylose-extracted corncob residues by simultaneous saccharification and fermentation

USDA-ARS?s Scientific Manuscript database

Conventional cellulose-to-ethanol conversion by simultaneous saccharification and fermentation (SSF)requires enzymatic saccharification using both cellulase and ß-glucosidase allowing cellulose utilization by common ethanologenic yeast. Here we report a new yeast strain of Clavispora NRRL Y-50464 th...

Biodiversity study of wine yeasts belonging to the "terroir" of Montepulciano d'Abruzzo "Colline Teramane" revealed Saccharomyces cerevisiae strains exhibiting atypical and unique 5.8S-ITS restriction patterns.

PubMed

Tofalo, Rosanna; Perpetuini, Giorgia; Fasoli, Giuseppe; Schirone, Maria; Corsetti, Aldo; Suzzi, Giovanna

2014-05-01

The Montepulciano d'Abruzzo "Colline Teramane" premium wine DOCG is produced in the Teramo province (Abruzzo, Italy). This region has a great tradition in winemaking and the wine is produced by a spontaneous fermentation so it could represent a reservoir of wine natural yeasts with important oenological features. The aim of this study was to characterize the yeast community of this wine grape growing region in order to create a Saccharomyces cerevisiae bank, providing data on oenological properties for potential industrial applications. A total of 430 yeasts were isolated at the end of spontaneous fermentation. PCR-RFLP was applied for the identification at the species level and underlined that 14 strains exhibited unusual and characteristic restriction patterns different from those typical of the species S. cerevisiae. This difference was due to the insertion of base C at a position 138 in the ITS1 region that determined an additional cleavage site for the enzyme HaeIII. This insertion could be associated to the fermentative performance and associated to the relationship existing between yeasts and a viticulture region or 'terroir'. Copyright © 2013 Elsevier Ltd. All rights reserved.

Yeast Monitoring of Wine Mixed or Sequential Fermentations Made by Native Strains from D.O. “Vinos de Madrid” Using Real-Time Quantitative PCR

PubMed Central

García, Margarita; Esteve-Zarzoso, Braulio; Crespo, Julia; Cabellos, Juan M.; Arroyo, Teresa

2017-01-01

There is an increasing trend toward understanding the impact of non-Saccharomyces yeasts on the winemaking process. Although Saccharomyces cerevisiae is the predominant species at the end of fermentation, it has been recognized that the presence of non-Saccharomyces species during alcoholic fermentation can produce an improvement in the quality and complexity of the final wines. A previous work was developed for selecting the best combinations between S. cerevisiae and five non-Saccharomyces (Torulaspora delbrueckii, Schizosaccharomyces pombe, Candida stellata, Metschnikowia pulcherrima, and Lachancea thermotolorans) native yeast strains from D.O. “Vinos de Madrid” at the laboratory scale. The best inoculation strategies between S. cerevisiae and non-Saccharomyces strains were chosen to analyze, by real-time quantitative PCR (qPCR) combined with the use of specific primers, the dynamics of inoculated populations throughout the fermentation process at the pilot scale using the Malvar white grape variety. The efficiency of the qPCR system was verified independently of the samples matrix, founding the inoculated yeast species throughout alcoholic fermentation. Finally, we can validate the positive effect of selected co-cultures in the Malvar wine quality, highlighting the sequential cultures of T. delbrueckii CLI 918/S. cerevisiae CLI 889 and C. stellata CLI 920/S. cerevisiae CLI 889 and, mixed and sequential cultures of L. thermotolerans 9-6C combined with S. cerevisiae CLI 889. PMID:29326669

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. © 2015 Institute of Food Technologists®

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.

Evaluation of Brewer's spent yeast to produce flavor enhancer nucleotides: influence of serial repitching.

PubMed

Vieira, Elsa; Brandão, Tiago; Ferreira, Isabel M P L V O

2013-09-18

The present work evaluates the influence of serial yeast repitching on nucleotide composition of brewer's spent yeast extracts produced without addition of exogenous enzymes. Two procedures for disrupting cell walls were compared, and the conditions for low-cost and efficient RNA hydrolysis were selected. A HILIC methodology was validated for the quantification of nucleotides and nucleosides in yeast extracts. Thirty-seven samples of brewer's spent yeast ( Saccharomyces pastorianus ) organized according to the number of serial repitchings were analyzed. Nucleotides accounted for 71.1-88.2% of the RNA products; 2'AMP was the most abundant (ranging between 0.08 and 2.89 g/100 g dry yeast). 5'GMP content ranged between 0.082 and 0.907 g/100 g dry yeast. The sum of 5'GMP, 5'IMP, and 5'AMP represented between 25 and 32% of total nucleotides. This works highlights for the first time that although serial repitching influences the content of monophosphate nucleotides and nucleosides, the profiles of these RNA hydrolysis products are not affected.

Phytase-producing capacity of yeasts isolated from traditional African fermented food products and PHYPk gene expression of Pichia kudriavzevii strains.

PubMed

Greppi, Anna; Krych, Łukasz; Costantini, Antonella; Rantsiou, Kalliopi; Hounhouigan, D Joseph; Arneborg, Nils; Cocolin, Luca; Jespersen, Lene

2015-07-16

Phytate is known as a strong chelate of minerals causing their reduced uptake by the human intestine. Ninety-three yeast isolates from traditional African fermented food products, belonging to nine species (Pichia kudriavzevii, Saccharomyces cerevisiae, Clavispora lusitaniae, Kluyveromyces marxianus, Millerozyma farinosa, Candida glabrata, Wickerhamomyces anomalus, Hanseniaspora guilliermondii and Debaryomyces nepalensis) were screened for phytase production on solid and liquid media. 95% were able to grow in the presence of phytate as sole phosphate source, P. kudriavzevii being the best growing species. A phytase coding gene of P. kudriavzevii (PHYPk) was identified and its expression was studied during growth by RT-qPCR. The expression level of PHYPk was significantly higher in phytate-medium, compared to phosphate-medium. In phytate-medium expression was seen in the lag phase. Significant differences in gene expression were detected among the strains as well as between the media. A correlation was found between the PHYPk expression and phytase extracellular activity. Copyright © 2015 Elsevier B.V. All rights reserved.

Enological Qualities and Interactions Between Native Yeast and Lactic Acid Bacteria from Queretaro, Mexico.

PubMed

Miranda-Castilleja, Dalia E; Martínez-Peniche, Ramón Á; Nadal Roquet-Jalmar, Montserrat; Aldrete-Tapia, J Alejandro; Arvizu-Medrano, Sofía M

2018-06-15

Despite the importance of strain compatibility, most of the enological strain selection studies are carried out separately on yeasts and lactic acid bacteria (LAB). In this study, the enological traits and interactions between native yeasts and LAB were studied. The H 2 S and acetic acid production, growth rates at 8 °C, killer phenotypes, flocculation, and tolerance to must and wine inhibitors were determined for 25 Saccharomyces yeasts. The ability to grow under two wine-like conditions was also determined in 37 LAB (Oenococcus oeni and Lactobacillus plantarum). The yeast-LAB compatibility of selected strains was tested in a sequential scheme. Finally, microvinification trials were performed using two strains from each group to determine the efficiencies and quality parameters. The phenotypic characterization by the K-means and hierarchical clusters indicated a correlation between flocculation and optical density increase in simulated must and wine medium (r = -0.415) and grouped the prominent yeasts SR19, SR26, and N05 as moderately flocculent, killer, acid producing, and highly tolerant strains. Among the LAB, L. plantarum FU39 grew 230% more than the rest. With regard to interactions, LAB growth stimulation (14-fold on average) due to the previous action of yeasts, particularly of SR19, was observed. The final quality of all wines was similar, but yeast SR19 performed a faster and more efficient fermentation than did N05, Also L. plantarum FU39 fermented faster than did O. oeni VC32. The use of quantitative data, and multivariate analyses allowed an integrative approach to the selection of a compatible and efficient pair of enological yeast-LAB strains. An alternative scheme is proposed for the joint selection of yeast and lactic acid bacteria strains, which allows us to foresee the interactions that may occur between them during winemaking. The kinetic parameters, turbidimetrically measured and analyzed by multivariate methods, simplify the detection of

Analysis of Growth Inhibition and Metabolism of Hydroxycinnamic Acids by Brewing and Spoilage Strains of Brettanomyces Yeast

PubMed Central

Lentz, Michael; Harris, Chad

2015-01-01

Brettanomyces yeasts are well-known as spoilage organisms in both the wine and beer industries, but also contribute important desirable characters to certain beer styles. These properties are mediated in large part by Brettanomyces’ metabolism of hydroxycinnamic acids (HCAs) present in beverage raw materials. Here we compare growth inhibition by, and metabolism of, HCAs among commercial brewing strains and spoilage strains of B. bruxellensis and B. anomalus. These properties vary widely among the different strains tested and between the HCAs analyzed. Brewing strains showed more efficient metabolism of ferulic acid over p-coumaric acid, a trait not shared among the spoilage strains. PMID:28231223

Development of High Cordycepin-Producing Cordyceps militaris Strains.

PubMed

Kang, Naru; Lee, Hyun-Hee; Park, Inmyoung; Seo, Young-Su

2017-03-01

Cordyceps militaris , known as Dong-Chong-Xia-Cao, produces the most cordycepin among Cordyceps species and can be cultured artificially. For these reasons, C. militaris is widely used as herb or functional food in the East Asia. In this study, we developed a new strain of C. militaris that produces higher cordycepin content than parent strains through mating-based sexual reproduction. Twenty parent strains were collected and identified as C. militaris based on internal trasncrived spacer and rDNA sequences. Seven single spores of MAT 1-1 idiomorph and five single spores of MAT 1-2 idiomorph were isolated from 12 parent strains. When 35 combinations were mated on the brown rice medium with the isolated single spores, eight combinations formed a stroma with a normal perithecia and confirmed mated strains. High pressure liquid chromatography analysis showed that mated strain KSP8 produced the most cordycepin in all the media among all the tested strains. This result showed due to genetic recombination occurring during the sexual reproduction of C. militaris . The development of C. militaris strain with increased cordycepin content by this approach can help not only to generate new C. militaris strains, but also to contribute to the health food or medicine industry.

Development of High Cordycepin-Producing Cordyceps militaris Strains

PubMed Central

Kang, Naru; Lee, Hyun-Hee; Park, Inmyoung

2017-01-01

Cordyceps militaris, known as Dong-Chong-Xia-Cao, produces the most cordycepin among Cordyceps species and can be cultured artificially. For these reasons, C. militaris is widely used as herb or functional food in the East Asia. In this study, we developed a new strain of C. militaris that produces higher cordycepin content than parent strains through mating-based sexual reproduction. Twenty parent strains were collected and identified as C. militaris based on internal trasncrived spacer and rDNA sequences. Seven single spores of MAT 1-1 idiomorph and five single spores of MAT 1-2 idiomorph were isolated from 12 parent strains. When 35 combinations were mated on the brown rice medium with the isolated single spores, eight combinations formed a stroma with a normal perithecia and confirmed mated strains. High pressure liquid chromatography analysis showed that mated strain KSP8 produced the most cordycepin in all the media among all the tested strains. This result showed due to genetic recombination occurring during the sexual reproduction of C. militaris. The development of C. militaris strain with increased cordycepin content by this approach can help not only to generate new C. militaris strains, but also to contribute to the health food or medicine industry. PMID:28435352

L-histidine inhibits biofilm formation and FLO11-associated phenotypes in Saccharomyces cerevisiae flor yeasts.

PubMed

Bou Zeidan, Marc; Zara, Giacomo; Viti, Carlo; Decorosi, Francesca; Mannazzu, Ilaria; Budroni, Marilena; Giovannetti, Luciana; Zara, Severino

2014-01-01

Flor yeasts of Saccharomyces cerevisiae have an innate diversity of Flo11p which codes for a highly hydrophobic and anionic cell-wall glycoprotein with a fundamental role in biofilm formation. In this study, 380 nitrogen compounds were administered to three S. cerevisiae flor strains handling Flo11p alleles with different expression levels. S. cerevisiae strain S288c was used as the reference strain as it cannot produce Flo11p. The flor strains generally metabolized amino acids and dipeptides as the sole nitrogen source, although with some exceptions regarding L-histidine and histidine containing dipeptides. L-histidine completely inhibited growth and its effect on viability was inversely related to Flo11p expression. Accordingly, L-histidine did not affect the viability of the Δflo11 and S288c strains. Also, L-histidine dramatically decreased air-liquid biofilm formation and adhesion to polystyrene of the flor yeasts with no effect on the transcription level of the Flo11p gene. Moreover, L-histidine modified the chitin and glycans content on the cell-wall of flor yeasts. These findings reveal a novel biological activity of L-histidine in controlling the multicellular behavior of yeasts [corrected].

L-Histidine Inhibits Biofilm Formation and FLO11-Associated Phenotypes in Saccharomyces cerevisiae Flor Yeasts

PubMed Central

Bou Zeidan, Marc; Zara, Giacomo; Viti, Carlo; Decorosi, Francesca; Mannazzu, Ilaria; Budroni, Marilena; Giovannetti, Luciana; Zara, Severino

2014-01-01

Flor yeasts of Saccharomyces cerevisiae have an innate diversity of FLO11 which codes for a highly hydrophobic and anionic cell-wall glycoprotein with a fundamental role in biofilm formation. In this study, 380 nitrogen compounds were administered to three S. cerevisiae flor strains handling FLO11 alleles with different expression levels. S. cerevisiae strain S288c was used as the reference strain as it cannot produce FLO11p. The flor strains generally metabolized amino acids and dipeptides as the sole nitrogen source, although with some exceptions regarding L-histidine and histidine containing dipeptides. L-histidine completely inhibited growth and its effect on viability was inversely related to FLO11 expression. Accordingly, L-histidine did not affect the viability of the Δflo11 and S288c strains. Also, L-histidine dramatically decreased air–liquid biofilm formation and adhesion to polystyrene of the flor yeasts with no effect on the transcription level of the FLO11 gene. Moreover, L-histidine modified the chitin and glycans content on the cell-wall of flor yeasts. These findings reveal a novel biological activity of L-histidine in controlling the multicellular behavior of yeasts. PMID:25369456

Improving the performance of industrial ethanol-producing yeast by expressing the aspartyl protease on the cell surface.

PubMed

Guo, Zhong-peng; Zhang, Liang; Ding, Zhong-yang; Wang, Zheng-Xiang; Shi, Gui-Yang

2010-12-01

The yeasts used in fuel ethanol manufacture are unable to metabolize soluble proteins. The PEP4 gene, encoding a vacuolar aspartyl protease in Saccharomyces cerevisiae, was either secretively or cell-surface anchored expressed in industrial ethanol-producing S. cerevisiae. The obtained recombinant strains APA (expressing the protease secretively) and APB (expressing the protease on the cell wall) were studied under ethanol fermentation conditions in feed barley cultures. The effects of expression of the protease on product formation, growth and cell protein content were measured. The biomass yield of the wild-type was clearly lower than that of the recombinant strains (0.578 ± 0.12 g biomass/g glucose for APA and 0.582 ± 0.08 g biomass/g glucose for APB). In addition, nearly 98-99% of the theoretical maximum level of ethanol yield was achieved (relative to the amount of substrate consumed) for the recombinant strains, while limiting the nitrogen source resulted in dissatisfactory fermentation for the wild-type and more than 30 g/l residual sugar was detected at the end of fermentation. In addition, higher growth rate, viability and lower yields of byproducts such as glycerol and pyruvic acid for recombinant strains were observed. Expressing acid protease can be expected to lead to a significant increase in ethanol productivity. Copyright © 2010 John Wiley & Sons, Ltd.

Yeast diversity of sourdoughs and associated metabolic properties and functionalities.

PubMed

De Vuyst, Luc; Harth, Henning; Van Kerrebroeck, Simon; Leroy, Frédéric

2016-12-19

Together with acidifying lactic acid bacteria, yeasts play a key role in the production process of sourdough, where they are either naturally present or added as a starter culture. Worldwide, a diversity of yeast species is encountered, with Saccharomyces cerevisiae, Candida humilis, Kazachstania exigua, Pichia kudriavzevii, Wickerhamomyces anomalus, and Torulaspora delbrueckii among the most common ones. Sourdough-adapted yeasts are able to withstand the stress conditions encountered during their growth, including nutrient starvation as well as the effects of acidic, oxidative, thermal, and osmotic stresses. From a technological point of view, their metabolism primarily contributes to the leavening and flavour of sourdough products. Besides ethanol and carbon dioxide, yeasts can produce metabolites that specifically affect flavour, such as organic acids, diacetyl, higher alcohols from branched-chain amino acids, and esters derived thereof. Additionally, several yeast strains possess functional properties that can potentially lead to nutritional and safety advantages. These properties encompass the production of vitamins, an improvement of the bioavailability of phenolic compounds, the dephosphorylation of phytic acid, the presence of probiotic potential, and the inhibition of fungi and their mycotoxin production. Strains of diverse species are new candidate functional starter cultures, offering opportunities beyond the conventional use of baker's yeast. Copyright © 2016 Elsevier B.V. All rights reserved.

Production of astaxanthin from cellulosic biomass sugars by mutants of the yeast Phaffia rhodozyma

USDA-ARS?s Scientific Manuscript database

Astaxanthin is a carotenoid of high value to the aquaculture, nutraceutical, and pharmaceutical industries. Three mutant strains of the astaxanthin-producing yeast Phaffia rhodozyma, which were derived from the parent strain ATCC 24202 (UCD 67-210) and designated JTM166, JTM185, and SSM19, were test...

Modulation of Intestinal Inflammation by Yeasts and Cell Wall Extracts: Strain Dependence and Unexpected Anti-Inflammatory Role of Glucan Fractions

PubMed Central

Jawhara, Samir; Habib, Khalid; Maggiotto, François; Pignede, Georges; Vandekerckove, Pascal; Maes, Emmanuel; Dubuquoy, Laurent; Fontaine, Thierry; Guerardel, Yann; Poulain, Daniel

2012-01-01

Yeasts and their glycan components can have a beneficial or adverse effect on intestinal inflammation. Previous research has shown that the presence of Saccharomyces cerevisiae var. boulardii (Sb) reduces intestinal inflammation and colonization by Candida albicans. The aim of this study was to identify dietary yeasts, which have comparable effects to the anti-C. albicans and anti-inflammatory properties of Sb and to assess the capabilities of yeast cell wall components to modulate intestinal inflammation. Mice received a single oral challenge of C. albicans and were then given 1.5% dextran-sulphate-sodium (DSS) for 2 weeks followed by a 3-day restitution period. S. cerevisiae strains (Sb, Sc1 to Sc4), as well as mannoprotein (MP) and β-glucan crude fractions prepared from Sc2 and highly purified β-glucans prepared from C. albicans were used in this curative model, starting 3 days after C. albicans challenge. Mice were assessed for the clinical, histological and inflammatory responses related to DSS administration. Strain Sc1-1 gave the same level of protection against C. albicans as Sb when assessed by mortality, clinical scores, colonization levels, reduction of TNFα and increase in IL-10 transcription. When Sc1-1 was compared with the other S. cerevisiae strains, the preparation process had a strong influence on biological activity. Interestingly, some S. cerevisiae strains dramatically increased mortality and clinical scores. Strain Sc4 and MP fraction favoured C. albicans colonization and inflammation, whereas β-glucan fraction was protective against both. Surprisingly, purified β-glucans from C. albicans had the same protective effect. Thus, some yeasts appear to be strong modulators of intestinal inflammation. These effects are dependent on the strain, species, preparation process and cell wall fraction. It was striking that β-glucan fractions or pure β-glucans from C. albicans displayed the most potent anti-inflammatory effect in the DSS model. PMID

Characteristics of the high malic acid production mechanism in Saccharomyces cerevisiae sake yeast strain No. 28.

PubMed

Nakayama, Shunichi; Tabata, Ken; Oba, Takahiro; Kusumoto, Kenichi; Mitsuiki, Shinji; Kadokura, Toshimori; Nakazato, Atsumi

2012-09-01

We characterized a high malic acid production mechanism in sake yeast strain No. 28. No considerable differences in the activity of the enzymes that were involved in malic acid synthesis were observed between strain No. 28 and its parent strain, K1001. However, compared with strain K1001, which actively took up rhodamine 123 during staining, the cells of strain No. 28 were only lightly stained, even when cultured in high glucose concentrations. In addition, malic acid production by the respiratory-deficient strain of K1001 was 2.5-fold higher than that of the wild-type K1001 and wild-type No. 28. The findings of this study demonstrated that the high malic acid production by strain No. 28 is attributed to the suppression of mitochondrial activity. Copyright © 2012. Published by Elsevier B.V.

Under pressure: evolutionary engineering of yeast strains for improved performance in fuels and chemicals production.

PubMed

Mans, Robert; Daran, Jean-Marc G; Pronk, Jack T

2018-04-01

Evolutionary engineering, which uses laboratory evolution to select for industrially relevant traits, is a popular strategy in the development of high-performing yeast strains for industrial production of fuels and chemicals. By integrating whole-genome sequencing, bioinformatics, classical genetics and genome-editing techniques, evolutionary engineering has also become a powerful approach for identification and reverse engineering of molecular mechanisms that underlie industrially relevant traits. New techniques enable acceleration of in vivo mutation rates, both across yeast genomes and at specific loci. Recent studies indicate that phenotypic trade-offs, which are often observed after evolution under constant conditions, can be mitigated by using dynamic cultivation regimes. Advances in research on synthetic regulatory circuits offer exciting possibilities to extend the applicability of evolutionary engineering to products of yeasts whose synthesis requires a net input of cellular energy. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Genomic Sequence of Saccharomyces cerevisiae BAW-6, a Yeast Strain Optimal for Brewing Barley Shochu

PubMed Central

Mori, Kazuki; Tashiro, Kosuke; Higuchi, Yujiro; Takashita, Hideharu

2018-01-01

ABSTRACT Here, we report the draft genome sequence of Saccharomyces cerevisiae strain BAW-6, which is used for the production of barley shochu, a traditional Japanese spirit. This genomic information can be used to elucidate the genetic basis underlying the high alcohol production capacity and citric acid tolerance of shochu yeast. PMID:29622617

Biodiversity of Exopolysaccharides Produced by Streptococcus thermophilus Strains Is Reflected in Their Production and Their Molecular and Functional Characteristics

PubMed Central

Vaningelgem, Frederik; Zamfir, Medana; Mozzi, Fernanda; Adriany, Tom; Vancanneyt, Marc; Swings, Jean; De Vuyst, Luc

2004-01-01

Twenty-six lactic acid bacterium strains isolated from European dairy products were identified as Streptococcus thermophilus and characterized by bacterial growth and exopolysaccharide (EPS)-producing capacity in milk and enriched milk medium. In addition, the acidification rates of the different strains were compared with their milk clotting behaviors. The majority of the strains grew better when yeast extract and peptone were added to the milk medium, although the presence of interfering glucomannans was shown, making this medium unsuitable for EPS screening. EPS production was found to be strain dependent, with the majority of the strains producing between 20 and 100 mg of polymer dry mass per liter of fermented milk medium. Furthermore, no straightforward relationship between the apparent viscosity and EPS production could be detected in fermented milk medium. An analysis of the molecular masses of the isolated EPS by gel permeation chromatography revealed a large variety, ranging from 10 to >2,000 kDa. A distinction could be made between high-molecular-mass EPS (>1,000 kDa) and low-molecular-mass EPS (<1,000 kDa). Based on the molecular size of the EPS, three groups of EPS-producing strains were distinguished. Monomer analysis of the EPS by high-performance anion-exchange chromatography with amperometric detection was demonstrated to be a fast and simple method. All of the EPS from the S. thermophilus strains tested were classified into six groups according to their monomer compositions. Apart from galactose and glucose, other monomers, such as (N-acetyl)galactosamine, (N-acetyl)glucosamine, and rhamnose, were also found as repeating unit constituents. Three strains were found to produce EPS containing (N-acetyl)glucosamine, which to our knowledge was never found before in an EPS from S. thermophilus. Furthermore, within each group, differences in monomer ratios were observed, indicating possible novel EPS structures. Finally, large differences between the

Molecular screening of xerophilic Aspergillus strains producing mycophenolic acid.

PubMed

Mouhamadou, Bello; Sage, Lucile; Périgon, Sophie; Séguin, Virginie; Bouchart, Valérie; Legendre, Patrick; Caillat, Mathilde; Yamouni, Hayet; Garon, David

2017-02-01

Mycophenolic acid (MPA) is the fungal secondary metabolite displaying several biological properties. Up to now, screening of fungal strains producing MPA has mainly been the result of the search of this molecule in their culture medium by chemical methods. Here we developed a molecular approach by targeting the expression level of the MpaC gene encoding the polyketide synthase, one of the key enzymes involved in the MPA synthesis. Thirty xerophilic Aspergillus strains were identified using the RNA polymerase II subunit and the β-tubulin genes. Seven Aspergillus species were evidenced. The expression level of the MpaC gene was quantified and compared to the MPA production rate. Only Aspergillus pseudoglaucus and all the eight strains of this species produced MPA. While the MpaC gene was not expressed or weakly expressed in the MPA non-producing strains, all the A. pseudoglaucus strains presented a high level of expression of this gene. The highest expression level of the MpaC gene among the MPA non-producing strains was significantly lower than the lowest expression level of this gene in the MPA producing strains. To our knowledge, this is the first study that demonstrates the effectiveness of molecular approach for the screening of MPA-producing species. Copyright © 2016 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Simultaneous saccharification and fermentation of Agave tequilana fructans by Kluyveromyces marxianus yeasts for bioethanol and tequila production.

PubMed

Flores, Jose-Axel; Gschaedler, Anne; Amaya-Delgado, Lorena; Herrera-López, Enrique J; Arellano, Melchor; Arrizon, Javier

2013-10-01

Agave tequilana fructans (ATF) constitute a substrate for bioethanol and tequila industries. As Kluyveromyces marxianus produces specific fructanases for ATF hydrolysis, as well as ethanol, it can perform simultaneous saccharification and fermentation. In this work, fifteen K. marxianus yeasts were evaluated to develop inoculums with fructanase activity on ATF. These inoculums were added to an ATF medium for simultaneous saccharification and fermentation. All the yeasts, showed exo-fructanhydrolase activity with different substrate specificities. The yeast with highest fructanase activity in the inoculums showed the lowest ethanol production level (20 g/l). Five K. marxianus strains were the most suitable for the simultaneous saccharification and fermentation of ATF. The volatile compounds composition was evaluated at the end of fermentation, and a high diversity was observed between yeasts, nevertheless all of them produced high levels of isobutyl alcohol. The simultaneous saccharification and fermentation of ATF with K. marxianus strains has potential for industrial application. Copyright © 2013 Elsevier Ltd. All rights reserved.

Growth of non-Saccharomyces yeasts affects nutrient availability for Saccharomyces cerevisiae during wine fermentation.

PubMed

Medina, Karina; Boido, Eduardo; Dellacassa, Eduardo; Carrau, Francisco

2012-07-02

Yeast produces numerous secondary metabolites during fermentation that impact final wine quality. Although it is widely recognized that growth of diverse non-Saccharomyces (NS) yeast can positively affect flavor complexity during Saccharomyces cerevisiae wine fermentation, the inability to control spontaneous or co-fermentation processes by NS yeast has restricted their use in winemaking. We selected two NS yeasts from our Uruguayan native collection to study NS-S. cerevisiae interactions during wine fermentation. The selected strains of Hanseniaspora vineae and Metschnikowia pulcherrima had different yeast assimilable nitrogen consumption profiles and had different effects on S. cerevisiae fermentation and growth kinetics. Studies in which we varied inoculum size and using either simultaneous or sequential inoculation of NS yeast and S. cerevisiae suggested that competition for nutrients had a significant effect on fermentation kinetics. Sluggish fermentations were more pronounced when S. cerevisiae was inoculated 24h after the initial stage of fermentation with a NS strain compared to co-inoculation. Monitoring strain populations using differential WL nutrient agar medium and fermentation kinetics of mixed cultures allowed for a better understanding of strain interactions and nutrient addition effects. Limitation of nutrient availability for S. cerevisiae was shown to result in stuck fermentations as well as to reduce sensory desirability of the resulting wine. Addition of diammonium phosphate (DAP) and a vitamin mix to a defined medium allowed for a comparison of nutrient competition between strains. Addition of DAP and the vitamin mix was most effective in preventing stuck fermentations. Copyright © 2012 Elsevier B.V. All rights reserved.

Malassezia yeasts produce a collection of exceptionally potent activators of the Ah (dioxin) receptor detected in diseased human skin

PubMed Central

Magiatis, Prokopios; Pappas, Periklis; Gaitanis, George; Mexia, Nikitia; Melliou, Eleni; Galanou, Maria; Vlachos, Christophoros; Stathopoulou, Konstantina; Skaltsounis, Alexios Leandros; Marselos, Marios; Velegraki, Aristea; Denison, Michael S.; Bassukas, Ioannis D.

2013-01-01

Malassezia yeasts are commensal microorganisms which under insufficiently understood conditions can become pathogenic. We have previously shown that specific strains isolated from diseased human skin can preferentially produce agonists of the aryl hydrocarbon receptor (AhR), whose activation has been linked to certain skin diseases. Investigation of skin scale extracts from patients with Malassezia associated diseases demonstrated 10–1000 fold higher AhR activating capacity than control skin extracts. LC/MS/MS analysis of the patients’ extracts revealed the presence of indirubin, 6-formylindolo[3,2-b]carbazole (FICZ), indolo[3,2-b]carbazole (ICZ), malassezin, and pityriacitrin. The same compounds were also identified in 9/12 Malassezia species culture extracts tested, connecting their presence in skin scales with this yeast. Studying the activity of the Malassezia culture-extracts and pure metabolites in HaCaT cells by Reverse Transcriptase Real-Time PCR revealed significant alterations in mRNA levels of the endogenous AhR-responsive genes Cyp1A1, Cyp1B1 and AhRR. Indirubin and FICZ activated AhR in HaCaT and human HepG2 cells with significantly higher, yet transient, potency as compared to the prototypical AhR ligand, dioxin. In loco synthesis of these highly potent AhR inducers by Malassezia yeasts could have a significant impact on skin homeostatic mechanisms and disease development. PMID:23448877

Malassezia yeasts produce a collection of exceptionally potent activators of the Ah (dioxin) receptor detected in diseased human skin.

PubMed

Magiatis, Prokopios; Pappas, Periklis; Gaitanis, George; Mexia, Nikitia; Melliou, Eleni; Galanou, Maria; Vlachos, Christophoros; Stathopoulou, Konstantina; Skaltsounis, Alexios Leandros; Marselos, Marios; Velegraki, Aristea; Denison, Michael S; Bassukas, Ioannis D

2013-08-01

Malassezia yeasts are commensal microorganisms, which under insufficiently understood conditions can become pathogenic. We have previously shown that specific strains isolated from diseased human skin can preferentially produce agonists of the aryl hydrocarbon receptor (AhR), whose activation has been linked to certain skin diseases. Investigation of skin scale extracts from patients with Malassezia-associated diseases demonstrated 10- to 1,000-fold higher AhR-activating capacity than control skin extracts. Liquid chromatography-tandem mass spectrometry analysis of the patients' extracts revealed the presence of indirubin, 6-formylindolo[3,2-b]carbazole (FICZ), indolo[3,2-b]carbazole (ICZ), malassezin, and pityriacitrin. The same compounds were also identified in 9 out of 12 Malassezia species culture extracts tested, connecting their presence in skin scales with this yeast. Studying the activity of the Malassezia culture extracts and pure metabolites in HaCaT cells by reverse transcriptase real-time PCR revealed significant alterations in mRNA levels of the endogenous AhR-responsive genes Cyp1A1, Cyp1B1, and AhRR. Indirubin- and FICZ-activated AhR in HaCaT and human HepG2 cells with significantly higher, yet transient, potency as compared with the prototypical AhR ligand, dioxin. In loco synthesis of these highly potent AhR inducers by Malassezia yeasts could have a significant impact on skin homeostatic mechanisms and disease development.

The Awesome Power of Yeast Evolutionary Genetics: New Genome Sequences and Strain Resources for the Saccharomyces sensu stricto Genus

PubMed Central

Scannell, Devin R.; Zill, Oliver A.; Rokas, Antonis; Payen, Celia; Dunham, Maitreya J.; Eisen, Michael B.; Rine, Jasper; Johnston, Mark; Hittinger, Chris Todd

2011-01-01

High-quality, well-annotated genome sequences and standardized laboratory strains fuel experimental and evolutionary research. We present improved genome sequences of three species of Saccharomyces sensu stricto yeasts: S. bayanus var. uvarum (CBS 7001), S. kudriavzevii (IFO 1802T and ZP 591), and S. mikatae (IFO 1815T), and describe their comparison to the genomes of S. cerevisiae and S. paradoxus. The new sequences, derived by assembling millions of short DNA sequence reads together with previously published Sanger shotgun reads, have vastly greater long-range continuity and far fewer gaps than the previously available genome sequences. New gene predictions defined a set of 5261 protein-coding orthologs across the five most commonly studied Saccharomyces yeasts, enabling a re-examination of the tempo and mode of yeast gene evolution and improved inferences of species-specific gains and losses. To facilitate experimental investigations, we generated genetically marked, stable haploid strains for all three of these Saccharomyces species. These nearly complete genome sequences and the collection of genetically marked strains provide a valuable toolset for comparative studies of gene function, metabolism, and evolution, and render Saccharomyces sensu stricto the most experimentally tractable model genus. These resources are freely available and accessible through www.SaccharomycesSensuStricto.org. PMID:22384314

Genome and metabolic engineering in non-conventional yeasts: Current advances and applications.

PubMed

Löbs, Ann-Kathrin; Schwartz, Cory; Wheeldon, Ian

2017-09-01

Microbial production of chemicals and proteins from biomass-derived and waste sugar streams is a rapidly growing area of research and development. While the model yeast Saccharomyces cerevisia e is an excellent host for the conversion of glucose to ethanol, production of other chemicals from alternative substrates often requires extensive strain engineering. To avoid complex and intensive engineering of S. cerevisiae, other yeasts are often selected as hosts for bioprocessing based on their natural capacity to produce a desired product: for example, the efficient production and secretion of proteins, lipids, and primary metabolites that have value as commodity chemicals. Even when using yeasts with beneficial native phenotypes, metabolic engineering to increase yield, titer, and production rate is essential. The non-conventional yeasts Kluyveromyces lactis, K. marxianus, Scheffersomyces stipitis, Yarrowia lipolytica, Hansenula polymorpha and Pichia pastoris have been developed as eukaryotic hosts because of their desirable phenotypes, including thermotolerance, assimilation of diverse carbon sources, and high protein secretion. However, advanced metabolic engineering in these yeasts has been limited. This review outlines the challenges of using non-conventional yeasts for strain and pathway engineering, and discusses the developed solutions to these problems and the resulting applications in industrial biotechnology.

Short communication: Conversion of lactose and whey into lactic acid by engineered yeast.

PubMed

Turner, Timothy L; Kim, Eunbee; Hwang, ChangHoon; Zhang, Guo-Chang; Liu, Jing-Jing; Jin, Yong-Su

2017-01-01

Lactose is often considered an unwanted and wasted byproduct, particularly lactose trapped in acid whey from yogurt production. But using specialized microbial fermentation, the surplus wasted acid whey could be converted into value-added chemicals. The baker's yeast Saccharomyces cerevisiae, which is commonly used for industrial fermentation, cannot natively ferment lactose. The present study describes how an engineered S. cerevisiae yeast was constructed to produce lactic acid from purified lactose, whey, or dairy milk. Lactic acid is an excellent proof-of-concept chemical to produce from lactose, because lactic acid has many food, pharmaceutical, and industrial uses, and over 250,000 t are produced for industrial use annually. To ferment the milk sugar lactose, a cellodextrin transporter (CDT-1, which also transports lactose) and a β-glucosidase (GH1-1, which also acts as a β-galactosidase) from Neurospora crassa were expressed in a S. cerevisiae strain. A heterologous lactate dehydrogenase (encoded by ldhA) from the fungus Rhizopus oryzae was integrated into the CDT-1/GH1-1-expressing strain of S. cerevisiae. As a result, the engineered strain was able to produce lactic acid from purified lactose, whey, and store-bought milk. A lactic acid yield of 0.358g/g of lactose was achieved from whey fermentation, providing an initial proof of concept for the production of value-added chemicals from excess industrial whey using engineered yeast. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

[New antibiotics produced by Bacillus subtilis strains].

PubMed

Malanicheva, I A; Kozlov, D G; Efimenko, T A; Zenkova, V A; Kastrukha, G S; Reznikova, M I; Korolev, A M; Borshchevskaia, L N; Tarasova, O D; Sineokiĭ, S P; Efremenkova, O V

2014-01-01

Two Bacillus subtilis strains isolated from the fruiting body of a basidiomycete fungus Pholiota squarrosa exhibited a broad range of antibacterial activity, including those against methicillin-resistant Staphylococcus aureus INA 00761 (MRSA) and Leuconostoc mes6nteroides VKPM B-4177 resistant to glycopep-> tide antibiotics, as well as antifungal activity. The strains were identified as belonging to the "B. subtilis" com- plex based on their morphological and physiological characteristics, as well as by sequencing of the 16S rRNA gene fragments. Both strains (INA 01085 and INA 01086) produced insignificant amounts of polyene antibiotics (hexaen and pentaen, respectively). Strain INA 01086 produced also a cyclic polypeptide antibiotic containing Asp, Gly, Leu, Pro, Tyr, Thr, Trp, and Phe, while the antibiotic of strain INA 01085 contained, apart from these, two unidentified nonproteinaceous amino acids. Both polypeptide antibiotics were new compounds efficient against gram-positive bacteria and able to override the natural bacterial antibiotic resistance.

Diversity and physiological characterization of D-xylose-fermenting yeasts isolated from the Brazilian Amazonian Forest.

PubMed

Cadete, Raquel M; Melo, Monaliza A; Dussán, Kelly J; Rodrigues, Rita C L B; Silva, Silvio S; Zilli, Jerri E; Vital, Marcos J S; Gomes, Fátima C O; Lachance, Marc-André; Rosa, Carlos A

2012-01-01

This study is the first to investigate the Brazilian Amazonian Forest to identify new D-xylose-fermenting yeasts that might potentially be used in the production of ethanol from sugarcane bagasse hemicellulosic hydrolysates. A total of 224 yeast strains were isolated from rotting wood samples collected in two Amazonian forest reserve sites. These samples were cultured in yeast nitrogen base (YNB)-D-xylose or YNB-xylan media. Candida tropicalis, Asterotremella humicola, Candida boidinii and Debaryomyces hansenii were the most frequently isolated yeasts. Among D-xylose-fermenting yeasts, six strains of Spathaspora passalidarum, two of Scheffersomyces stipitis, and representatives of five new species were identified. The new species included Candida amazonensis of the Scheffersomyces clade and Spathaspora sp. 1, Spathaspora sp. 2, Spathaspora sp. 3, and Candida sp. 1 of the Spathaspora clade. In fermentation assays using D-xylose (50 g/L) culture medium, S. passalidarum strains showed the highest ethanol yields (0.31 g/g to 0.37 g/g) and productivities (0.62 g/L · h to 0.75 g/L · h). Candida amazonensis exhibited a virtually complete D-xylose consumption and the highest xylitol yields (0.55 g/g to 0.59 g/g), with concentrations up to 25.2 g/L. The new Spathaspora species produced ethanol and/or xylitol in different concentrations as the main fermentation products. In sugarcane bagasse hemicellulosic fermentation assays, S. stipitis UFMG-XMD-15.2 generated the highest ethanol yield (0.34 g/g) and productivity (0.2 g/L · h), while the new species Spathaspora sp. 1 UFMG-XMD-16.2 and Spathaspora sp. 2 UFMG-XMD-23.2 were very good xylitol producers. This study demonstrates the promise of using new D-xylose-fermenting yeast strains from the Brazilian Amazonian Forest for ethanol or xylitol production from sugarcane bagasse hemicellulosic hydrolysates.

Comparative Proteome Analysis between High Lipid-Producing Strain Mucor circinelloides WJ11 and Low Lipid-Producing Strain CBS 277.49.

PubMed

Tang, Xin; Chen, Haiqin; Gu, Zhennan; Zhang, Hao; Chen, Yong Q; Song, Yuanda; Chen, Wei

2017-06-21

Mucor circinelloides is one of few oleaginous fungi that produces a useful oil rich in γ-linolenic acid, but it usually only produces <25% total lipid. Nevertheless, we isolated a new strain WJ11 that can produce up to 36% lipid of cell dry weight. In this study, we have systematically analyzed the global changes in protein levels between the high lipid-producing strain WJ11 and the low lipid-producing strain CBS 277.49 (15%, lipid/cell dry weight) at lipid accumulation phase through comparative proteome analysis. Proteome analysis demonstrated that the branched-chain amino acid and lysine metabolism, glycolytic pathway, and pentose phosphate pathway in WJ11 were up-regulated, while the activities of tricarboxylic acid cycle and branch point enzyme for synthesis of isoprenoids were retarded compared with CBS 277.49. The coordinated regulation at proteome level indicate that more acetyl-CoA and NADPH are provided for fatty acid biosynthesis in WJ11 compared with CBS 277.49.

TEM Derivative-Producing Enterobacter aerogenes Strains: Dissemination of a Prevalent Clone

PubMed Central

Dumarche, P.; De Champs, C.; Sirot, D.; Chanal, C.; Bonnet, R.; Sirot, J.

2002-01-01

TEM-24 (CAZ-6) extended-spectrum β-lactamase (ESBL) was detected in 1988 in Clermont-Ferrand, France, in Klebsiella pneumoniae (blaTEM-24) and Enterobacter aerogenes (blaTEM-24b), and since 1994, a TEM-24-producing E. aerogenes clonal strain has been observed elsewhere in the country. To determine if the spread of this clonal strain was restricted to TEM-24-producing E. aerogenes strains, 84 E. aerogenes strains (non-TEM/SHV-producing strains, TEM-1- or -2-producing strains, and different ESBL-producing strains), isolated from 1988 to 1999 in Clermont-Ferrand (n = 59) and in 11 other French hospitals in 1998 (n = 25), were studied. A clonal strain was found for TEM-24- but also for TEM-3- and TEM-1- or 2-producing isolates. This study shows that there is a clonal strain dependent on acquisition of the TEM-type enzyme (TEM-24 and other TEM types). PMID:11897606

Multiple α-Glucoside Transporter Genes in Brewer’s Yeast

PubMed Central

Jespersen, Lene; Cesar, Lene B.; Meaden, Philip G.; Jakobsen, Mogens

1999-01-01

Maltose and maltotriose are the two most abundant fermentable sugars in brewer’s wort, and the rate of uptake of these sugars by brewer’s yeast can have a major impact on fermentation performance. In spite of this, no information is currently available on the genetics of maltose and maltotriose uptake in brewing strains of yeast. In this work, we studied 30 brewing strains of yeast (5 ale strains and 25 lager strains) with the aim of examining the alleles of maltose and maltotriose transporter genes contained by them. To do this, we hybridized gene probes to chromosome blots. Studies performed with laboratory strains have shown that maltose utilization is conferred by any one of five unlinked but highly homologous MAL loci (MAL1 to MAL4 and MAL6). Gene 1 at each locus encodes a maltose transporter. All of the strains of brewer’s yeast examined except two were found to contain MAL11 and MAL31 sequences, and only one of these strains lacked MAL41. MAL21 was not present in the five ale strains and 12 of the lager strains. MAL61 was not found in any of the yeast strains. In three of the lager strains, there was evidence that MAL transporter gene sequences occurred on chromosomes other than those known to carry MAL loci. Sequences corresponding to the AGT1 gene, which encodes a transporter of several α-glucosides, including maltose and maltotriose, were detected in all but one of the yeast strains. Homologues of AGT1 were identified in three of the lager strains, and two of these homologues were mapped, one to chromosome II and the other to chromosome XI. AGT1 appears to be a member of a family of closely related genes, which may have arisen in brewer’s yeast in response to selective pressure. PMID:9925567

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

PubMed Central

Heer, Dominik; Sauer, Uwe

2008-01-01

Summary 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

Synergetic effect of yeast cell-surface expression of cellulase and expansin-like protein on direct ethanol production from cellulose

PubMed Central

2013-01-01

Background Numerous studies have examined the direct fermentation of cellulosic materials by cellulase-expressing yeast; however, ethanol productivity in these systems has not yet reached an industrial level. Certain microorganisms, such as the cellulolytic fungus Trichoderma reesei, produce expansin-like proteins, which have a cellulose-loosening effect that may increase the breakdown of cellulose. Here, to improve the direct conversion of cellulose to ethanol, yeast Saccharomyces cerevisiae co-displaying cellulase and expansin-like protein on the cell surface were constructed and examined for direct ethanol fermentation performance. Results The cellulase and expansin-like protein co-expressing strain showed 246 mU/g-wet cell of phosphoric acid swollen cellulose (PASC) degradation activity, which corresponded to 2.9-fold higher activity than that of a cellulase-expressing strain. This result clearly demonstrated that yeast cell-surface expressed cellulase and expansin-like protein act synergistically to breakdown cellulose. In fermentation experiments examining direct ethanol production from PASC, the cellulase and expansin-like protein co-expressing strain produced 3.4 g/L ethanol after 96 h of fermentation, a concentration that was 1.4-fold higher than that achieved by the cellulase-expressing strain (2.5 g/L). Conclusions The PASC degradation and fermentation ability of an engineered yeast strain was markedly improved by co-expressing cellulase and expansin-like protein on the cell surface. To our knowledge, this is the first report to demonstrate the synergetic effect of co-expressing cellulase and expansin-like protein on a yeast cell surface, which may be a promising strategy for constructing direct ethanol fermenting yeast from cellulose. PMID:23835302

The Geographic Distribution of Saccharomyces cerevisiae Isolates within three Italian Neighboring Winemaking Regions Reveals Strong Differences in Yeast Abundance, Genetic Diversity and Industrial Strain Dissemination

PubMed Central

Viel, Alessia; Legras, Jean-Luc; Nadai, Chiara; Carlot, Milena; Lombardi, Angiolella; Crespan, Manna; Migliaro, Daniele; Giacomini, Alessio; Corich, Viviana

2017-01-01

In recent years the interest for natural fermentations has been re-evaluated in terms of increasing the wine terroir and managing more sustainable winemaking practices. Therefore, the level of yeast genetic variability and the abundance of Saccharomyces cerevisiae native populations in vineyard are becoming more and more crucial at both ecological and technological level. Among the factors that can influence the strain diversity, the commercial starter release that accidentally occur in the environment around the winery, has to be considered. In this study we led a wide scale investigation of S. cerevisiae genetic diversity and population structure in the vineyards of three neighboring winemaking regions of Protected Appellation of Origin, in North-East of Italy. Combining mtDNA RFLP and microsatellite markers analyses we evaluated 634 grape samples collected over 3 years. We could detect major differences in the presence of S. cerevisiae yeasts, according to the winemaking region. The population structures revealed specificities of yeast microbiota at vineyard scale, with a relative Appellation of Origin area homogeneity, and transition zones suggesting a geographic differentiation. Surprisingly, we found a widespread industrial yeast dissemination that was very high in the areas where the native yeast abundance was low. Although geographical distance is a key element involved in strain distribution, the high presence of industrial strains in vineyard reduced the differences between populations. This finding indicates that industrial yeast diffusion it is a real emergency and their presence strongly interferes with the natural yeast microbiota. PMID:28883812

Production, Purification, and Gene Cloning of a β-Fructofuranosidase with a High Inulin-hydrolyzing Activity Produced by a Novel Yeast Aureobasidium sp. P6 Isolated from a Mangrove Ecosystem.

PubMed

Jiang, Hong; Ma, Yan; Chi, Zhe; Liu, Guang-Lei; Chi, Zhen-Ming

2016-08-01

After screening of over 300 yeast strains isolated from the mangrove ecosystems, it was found that Aureobasidium sp. P6 strain had the highest inulin-hydrolyzing activity. Under the optimal conditions, this yeast strain produced an inulin-hydrolyzing activity of 30.98 ± 0.8 U/ml after 108 h of a 10-l fermentation. After the purification, a molecular weight of the enzyme which had the inulin-hydrolyzing activity was estimated to be 47.6 kDa, and the purified enzyme could actively hydrolyze both sucrose and inulin and exhibit a transfructosylating activity at 30.0 % sucrose, converting sucrose into fructooligosaccharides (FOS), indicating that the purified enzyme was a β-D-fructofuranosidase. After the full length of a β-D-fructofuranosidase gene (accession number KU308553) was cloned from Aureobasidium sp. P6 strain, a protein deduced from the cloned gene contained the conserved sequences MNDPNGL, RDP, ECP, FS, and Q of a glycosidehydrolase GH32 family, respectively, but did not contain a conserved sequence SVEVF, and the amino acid sequence of the protein from Aureobasidium sp. P6 strain had a high similarity to that of the β-fructofuranosidase from any other fungal strains. After deletion of the β-D-fructofuranosidase gene, the disruptant still had low inulin hydrolyzing and invertase activities and a trace amount of the transfructosylating activity, indicating that the gene encoding an inulinase may exist in the Aureobasidium sp. P6 strain.

Genomic Sequence of Saccharomyces cerevisiae BAW-6, a Yeast Strain Optimal for Brewing Barley Shochu.

PubMed

Kajiwara, Yasuhiro; Mori, Kazuki; Tashiro, Kosuke; Higuchi, Yujiro; Takegawa, Kaoru; Takashita, Hideharu

2018-04-05

Here, we report the draft genome sequence of Saccharomyces cerevisiae strain BAW-6, which is used for the production of barley shochu, a traditional Japanese spirit. This genomic information can be used to elucidate the genetic basis underlying the high alcohol production capacity and citric acid tolerance of shochu yeast. Copyright © 2018 Kajiwara et al.

Fermentation and aerobic metabolism of cellodextrins by yeasts. [Candida wickerhamii; C. guiliermondii; C. molischiana; Debaryomyces polymorphus; Pichia guilliermondii; Clavispora lusitaniae; Kluyveromyces lactis; Brettanomyces claussenii; Rhodotorula minuta; Dekkera intermedia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Freer, S.N.

1991-03-01

The fermentation and aerobic metabolism of cellodextrins by 14 yeast species or strains was monitored. When grown aerobically, Candida wickerhamii, C. guilliermondii, and C. molischiana metabolized cellodextrins of degree of polymerization 3 to 6. C. wicherhamii and C. molischiana also fermented these substrates, while C. guilliermondii fermented only cellodextrins of degree of polymerization {<=} 3. Debaryomyces polymorphus, Pichia guilliermondii, Clavispora lusitaniae, and one of two strains of Kluyveromyces lactis metabolized glucose, cellobiose, and cellotriose when grown aerobically. These yeasts also fermented these substrates, except for K. lactis, which fermented only glucose and cellobiose. The remaining species/strains tested, K. lactis, Brettanomycesmore » claussenii, Brettanomyces anomalus, Kluyveromyces dobzhanskii, Rhodotorula minuta, and Dekkera intermedia, both fermented and aerobically metabolized glucose and cellobiose. Crude enzyme preparations from all 14 yeast species or strains were tested for ability to hydrolyze cellotriose and cellotretose. Most of the yeasts produced an enzyme(s) capable of hydrolyzing cellotriose. However, with two exceptions, R. minuta and P. guilliermondii, only the yeasts that metabolized cellodextrins of degree of polymerization >3 produced an enzyme(s) that hydrolyzed cellotretose.« less

Production of fatty acid-derived oleochemicals and biofuels by synthetic yeast cell factories

PubMed Central

Zhou, Yongjin J.; Buijs, Nicolaas A.; Zhu, Zhiwei; Qin, Jiufu; Siewers, Verena; Nielsen, Jens

2016-01-01

Sustainable production of oleochemicals requires establishment of cell factory platform strains. The yeast Saccharomyces cerevisiae is an attractive cell factory as new strains can be rapidly implemented into existing infrastructures such as bioethanol production plants. Here we show high-level production of free fatty acids (FFAs) in a yeast cell factory, and the production of alkanes and fatty alcohols from its descendants. The engineered strain produces up to 10.4 g l−1 of FFAs, which is the highest reported titre to date. Furthermore, through screening of specific pathway enzymes, endogenous alcohol dehydrogenases and aldehyde reductases, we reconstruct efficient pathways for conversion of fatty acids to alkanes (0.8 mg l−1) and fatty alcohols (1.5 g l−1), to our knowledge the highest titres reported in S. cerevisiae. This should facilitate the construction of yeast cell factories for production of fatty acids derived products and even aldehyde-derived chemicals of high value. PMID:27222209

Highly cold-active pectinases under wine-like conditions from non-Saccharomyces yeasts for enzymatic production during winemaking.

PubMed

Merín, M G; Morata de Ambrosini, V I

2015-05-01

The influence of oenological factors on cold-active pectinases from 15 preselected indigenous yeasts belonging to Aureobasidium pullulans, Filobasidium capsuligenum, Rhodotorula dairenensis, Cryptococcus saitoi and Saccharomyces cerevisiae was investigated. Pectinolytic enzymes were constitutive or partially constitutive; and high glucose concentration (200 g l(-1) ) did not affect or increased pectinase production at 12°C and pH 3·5 (up to 113·9 U mg(-1) ) only in A. pullulans strains. SO2 (120 mg l(-1) ) slightly affected the growth of A. pullulans strains but did not affect pectinase production levels. Ethanol (15%) barely affected pectinase activity of A. pullulans strains but diminished relative activity to 12-79% of basidiomycetous yeasts. Moreover, non-Saccharomyces strains showed promising properties of oenological interest. This study demonstrates that cold-active pectinases from some A. pullulans strains were able to remain active at glucose, ethanol and SO2 concentrations usually found in vinification, and suggests their potential use as processing aids for low-temperature winemaking. Nowadays, there is increasing interest in low-temperature winemaking. Nevertheless, commercial oenological pectinases, produced by fungi, are rarely active at low temperatures. Cold-active pectinases that are stable under vinification conditions are needed. This study indicated that cold-active and acid-tolerant pectinases from non-Saccharomcyes yeasts were able to remain active at glucose, ethanol and SO2 concentrations usually found in winemaking. Furthermore, not only are these yeasts a source of cold-active pectinases, but the yeasts themselves are also potential adjunct cultures for oenology to produce these enzymes during cold-winemaking. © 2015 The Society for Applied Microbiology.

Lager Yeast Comes of Age

PubMed Central

2014-01-01

Alcoholic fermentations have accompanied human civilizations throughout our history. Lager yeasts have a several-century-long tradition of providing fresh beer with clean taste. The yeast strains used for lager beer fermentation have long been recognized as hybrids between two Saccharomyces species. We summarize the initial findings on this hybrid nature, the genomics/transcriptomics of lager yeasts, and established targets of strain improvements. Next-generation sequencing has provided fast access to yeast genomes. Its use in population genomics has uncovered many more hybridization events within Saccharomyces species, so that lager yeast hybrids are no longer the exception from the rule. These findings have led us to propose network evolution within Saccharomyces species. This “web of life” recognizes the ability of closely related species to exchange DNA and thus drain from a combined gene pool rather than be limited to a gene pool restricted by speciation. Within the domesticated lager yeasts, two groups, the Saaz and Frohberg groups, can be distinguished based on fermentation characteristics. Recent evidence suggests that these groups share an evolutionary history. We thus propose to refer to the Saaz group as Saccharomyces carlsbergensis and to the Frohberg group as Saccharomyces pastorianus based on their distinct genomes. New insight into the hybrid nature of lager yeast will provide novel directions for future strain improvement. PMID:25084862

Fermentation of biomass sugars to ethanol using native industrial yeast strains.

PubMed

Yuan, Dawei; Rao, Kripa; Relue, Patricia; Varanasi, Sasidhar

2011-02-01

In this paper, the feasibility of a technology for fermenting sugar mixtures representative of cellulosic biomass hydrolyzates with native industrial yeast strains is demonstrated. This paper explores the isomerization of xylose to xylulose using a bi-layered enzyme pellet system capable of sustaining a micro-environmental pH gradient. This ability allows for considerable flexibility in conducting the isomerization and fermentation steps. With this method, the isomerization and fermentation could be conducted sequentially, in fed-batch, or simultaneously to maximize utilization of both C5 and C6 sugars and ethanol yield. This system takes advantage of a pH-dependent complexation of xylulose with a supplemented additive to achieve up to 86% isomerization of xylose at fermentation conditions. Commercially-proven Saccharomyces cerevisiae strains from the corn-ethanol industry were used and shown to be very effective in implementation of the technology for ethanol production. Copyright © 2010 Elsevier Ltd. All rights reserved.

Functional analysis of lipid metabolism genes in wine yeasts during alcoholic fermentation at low temperature

PubMed Central

López-Malo, María; García-Ríos, Estéfani; Chiva, Rosana; Guillamon, José M.

2014-01-01

Wine produced by low-temperature fermentation is mostly considered to have improved sensory qualities. However few commercial wine strains available on the market are well-adapted to ferment at low temperature (10 - 15°C). The lipid metabolism of Saccharomyces cerevisiae plays a central role in low temperature adaptation. One strategy to modify lipid composition is to alter transcriptional activity by deleting or overexpressing the key genes of lipid metabolism. In a previous study, we identified the genes of the phospholipid, sterol and sphingolipid pathways, which impacted on growth capacity at low temperature. In the present study, we aimed to determine the influence of these genes on fermentation performance and growth during low-temperature wine fermentations. We analyzed the phenotype during fermentation at the low and optimal temperature of the lipid mutant and overexpressing strains in the background of a derivative commercial wine strain. The increase in the gene dosage of some of these lipid genes, e.g., PSD1, LCB3, DPL1 and OLE1, improved fermentation activity during low-temperature fermentations, thus confirming their positive role during wine yeast adaptation to cold. Genes whose overexpression improved fermentation activity at 12°C were overexpressed by chromosomal integration into commercial wine yeast QA23. Fermentations in synthetic and natural grape must were carried out by this new set of overexpressing strains. The strains overexpressing OLE1 and DPL1 were able to finish fermentation before commercial wine yeast QA23. Only the OLE1 gene overexpression produced a specific aroma profile in the wines produced with natural grape must. PMID:28357215

Functional analysis of lipid metabolism genes in wine yeasts during alcoholic fermentation at low temperature.

PubMed

López-Malo, María; García-Ríos, Estéfani; Chiva, Rosana; Guillamon, José M

2014-10-29

Wine produced by low-temperature fermentation is mostly considered to have improved sensory qualities. However few commercial wine strains available on the market are well-adapted to ferment at low temperature (10 - 15°C). The lipid metabolism of Saccharomyces cerevisiae plays a central role in low temperature adaptation. One strategy to modify lipid composition is to alter transcriptional activity by deleting or overexpressing the key genes of lipid metabolism. In a previous study, we identified the genes of the phospholipid, sterol and sphingolipid pathways, which impacted on growth capacity at low temperature. In the present study, we aimed to determine the influence of these genes on fermentation performance and growth during low-temperature wine fermentations. We analyzed the phenotype during fermentation at the low and optimal temperature of the lipid mutant and overexpressing strains in the background of a derivative commercial wine strain. The increase in the gene dosage of some of these lipid genes, e.g., PSD1 , LCB3, DPL1 and OLE1, improved fermentation activity during low-temperature fermentations, thus confirming their positive role during wine yeast adaptation to cold. Genes whose overexpression improved fermentation activity at 12°C were overexpressed by chromosomal integration into commercial wine yeast QA23. Fermentations in synthetic and natural grape must were carried out by this new set of overexpressing strains. The strains overexpressing OLE1 and DPL1 were able to finish fermentation before commercial wine yeast QA23. Only the OLE1 gene overexpression produced a specific aroma profile in the wines produced with natural grape must.

A Loss-of-Function Mutation in the PAS Kinase Rim15p Is Related to Defective Quiescence Entry and High Fermentation Rates of Saccharomyces cerevisiae Sake Yeast Strains

PubMed Central

Watanabe, Daisuke; Araki, Yuya; Zhou, Yan; Maeya, Naoki; Akao, Takeshi

2012-01-01

Sake yeast cells have defective entry into the quiescent state, allowing them to sustain high fermentation rates. To reveal the underlying mechanism, we investigated the PAS kinase Rim15p, which orchestrates initiation of the quiescence program in Saccharomyces cerevisiae. We found that Rim15p is truncated at the carboxyl terminus in modern sake yeast strains as a result of a frameshift mutation. Introduction of this mutation or deletion of the full-length RIM15 gene in a laboratory strain led to a defective stress response, decreased synthesis of the storage carbohydrates trehalose and glycogen, and impaired G1 arrest, which together closely resemble the characteristic phenotypes of sake yeast. Notably, expression of a functional RIM15 gene in a modern sake strain suppressed all of these phenotypes, demonstrating that dysfunction of Rim15p prevents sake yeast cells from entering quiescence. Moreover, loss of Rim15p or its downstream targets Igo1p and Igo2p remarkably improved the fermentation rate in a laboratory strain. This finding verified that Rim15p-mediated entry into quiescence plays pivotal roles in the inhibition of ethanol fermentation. Taken together, our results suggest that the loss-of-function mutation in the RIM15 gene may be the key genetic determinant of the increased ethanol production rates in modern sake yeast strains. PMID:22447585

A loss-of-function mutation in the PAS kinase Rim15p is related to defective quiescence entry and high fermentation rates of Saccharomyces cerevisiae sake yeast strains.

PubMed

Watanabe, Daisuke; Araki, Yuya; Zhou, Yan; Maeya, Naoki; Akao, Takeshi; Shimoi, Hitoshi

2012-06-01

Sake yeast cells have defective entry into the quiescent state, allowing them to sustain high fermentation rates. To reveal the underlying mechanism, we investigated the PAS kinase Rim15p, which orchestrates initiation of the quiescence program in Saccharomyces cerevisiae. We found that Rim15p is truncated at the carboxyl terminus in modern sake yeast strains as a result of a frameshift mutation. Introduction of this mutation or deletion of the full-length RIM15 gene in a laboratory strain led to a defective stress response, decreased synthesis of the storage carbohydrates trehalose and glycogen, and impaired G(1) arrest, which together closely resemble the characteristic phenotypes of sake yeast. Notably, expression of a functional RIM15 gene in a modern sake strain suppressed all of these phenotypes, demonstrating that dysfunction of Rim15p prevents sake yeast cells from entering quiescence. Moreover, loss of Rim15p or its downstream targets Igo1p and Igo2p remarkably improved the fermentation rate in a laboratory strain. This finding verified that Rim15p-mediated entry into quiescence plays pivotal roles in the inhibition of ethanol fermentation. Taken together, our results suggest that the loss-of-function mutation in the RIM15 gene may be the key genetic determinant of the increased ethanol production rates in modern sake yeast strains.

Candida queiroziae sp. nov., a cellobiose-fermenting yeast species isolated from rotting wood in Atlantic Rain Forest.

PubMed

Santos, Renata O; Cadete, Raquel M; Badotti, Fernanda; Mouro, Adriane; Wallheim, Daniela O; Gomes, Fátima C O; Stambuk, Boris U; Lachance, Marc-André; Rosa, Carlos A

2011-03-01

Eight strains of a novel yeast species were isolated from rotting wood and wood-boring insects in Atlantic Rain Forest ecosystems in Brazil. Sequences of the D1/D2 domains of the large subunit of the rRNA gene showed that the yeast belongs to the Scheffersomyces clade and that it is related to Candida lignicola and Candida coipomoensis. The new species was isolated from rotting wood of three different localities and a wood-boring insect suggesting that these substrates are its ecological niche. This new yeast species is able to assimilate cellobiose and other compounds related to rotting wood. Strong fermentation of cellobiose in Durham tubes was observed for the strains of this new yeast. The new species produced an intracellular β-glucosidase responsible for cellobiose hydrolysis. The novel species, Candida queiroziae sp. nov., is proposed to accommodate these isolates. The type strain of C. queiroziae is UFMG-CLM 5.1(T) (=CBS 11853(T) = NRRL Y-48722(T)).

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

New Saccharomyces cerevisiae baker's yeast displaying enhanced resistance to freezing.

PubMed

Codón, Antonio C; Rincón, Ana M; Moreno-Mateos, Miguel A; Delgado-Jarana, Jesús; Rey, Manuel; Limón, Carmen; Rosado, Ivan V; Cubero, Beatriz; Peñate, Xenia; Castrejón, Francisco; Benítez, Tahía

2003-01-15

Three procedures were used to obtain new Saccharomyces cerevisiae baker's yeasts with increased storage stability at -20, 4, 22, and 30 degrees C. The first used mitochondria from highly ethanol-tolerant wine yeast, which were transferred to baker's strains. Viability of the heteroplasmons was improved shortly after freezing. However, after prolonged storage, viability dramatically decreased and was accompanied by an increase in the frequency of respiratory-deficient (petite) mutant formation. This indicated that mitochondria were not stable and were incompatible with the nucleus. The strains tested regained their original resistance to freezing after recovering their own mitochondria. The second procedure used hybrid formation after protoplast fusion and isolation on selective media of fusants from baker's yeast meiotic products resistant to parafluorphenylalanine and cycloheximide, respectively. No hybrids were obtained when using the parentals, probably due to the high ploidy of the baker's strains. Hybrids obtained from nonisogenic strains manifested in all cases a resistance to freezing intermediate between those of their parental strains. Hybrids from crosses between meiotic products of the same strain were always more sensitive than their parentals. The third method was used to develop baker's yeast mutants resistant to 2-deoxy-d-glucose (DOG) and deregulated for maltose and sucrose metabolism. Mutant DOG21 displayed a slight increase in trehalose content and viability both in frozen doughs and during storage at 4 and 22 degrees C. This mutant also displayed a capacity to ferment, under laboratory conditions, both lean and sweet fresh and frozen doughs. For industrial uses, fermented lean and sweet bakery products, both from fresh and frozen doughs obtained with mutant DOG21, were of better quality with regard to volume, texture, and organoleptic properties than those produced by the wild type.

Genome Sequence of the Lager-Brewing Yeast Saccharomyces sp. Strain M14, Used in the High-Gravity Brewing Industry in China

PubMed Central

Liu, Chunfeng; Niu, Chengtuo; Zheng, Feiyun; Li, Yongxian; Zhao, Yun; Yin, Xiangsheng

2017-01-01

ABSTRACT Lager-brewing yeasts are mainly used for the production of lager beers. Illumina and PacBio-based sequence analyses revealed an approximate genome size of 22.8 Mb, with a GC content of 38.98%, for the Chinese lager-brewing yeast Saccharomyces sp. strain M14. Based on ab initio prediction, 9,970 coding genes were annotated. PMID:29074666

The genetics of a putative social trait in natural populations of yeast

PubMed Central

Bozdag, G O; Greig, D

2014-01-01

The sharing of secreted invertase by yeast cells is a well-established laboratory model for cooperation, but the only evidence that such cooperation occurs in nature is that the SUC loci, which encode invertase, vary in number and functionality. Genotypes that do not produce invertase can act as ‘cheats’ in laboratory experiments, growing on the glucose that is released when invertase producers, or ‘cooperators’, digest sucrose. However, genetic variation for invertase production might instead be explained by adaptation of different populations to different local availabilities of sucrose, the substrate for invertase. Here we find that 110 wild yeast strains isolated from natural habitats, and all contained a single SUC locus and produced invertase; none were ‘cheats’. The only genetic variants we found were three strains isolated instead from sucrose-rich nectar, which produced higher levels of invertase from three additional SUC loci at their subtelomeres. We argue that the pattern of SUC gene variation is better explained by local adaptation than by social conflict. PMID:25169714

Substrate-Limited Saccharomyces cerevisiae Yeast Strains Allow Control of Fermentation during Bread Making.

PubMed

Struyf, Nore; Laurent, Jitka; Verspreet, Joran; Verstrepen, Kevin J; Courtin, Christophe M

2017-04-26

Identification and use of yeast strains that are unable to consume one or more otherwise fermentable substrate types could allow a more controlled fermentation process with more flexibility regarding fermentation times. In this study, Saccharomyces cerevisiae strains with different capacities to consume substrates present in wheat were selected to investigate the impact of substrate limitation on dough fermentation and final bread volume. Results show that fermentation of dough with maltose-negative strains relies on the presence of fructan and sucrose as fermentable substrates and can be used for regular bread making. Levels of fructan and sucrose, endogenously present or added, hence determine the extent of fermentation and timing at the proofing stage. Whole meal is inherently more suitable for substrate-limited fermentation than white flour due to the presence of higher native levels of these substrates. Bread making protocols with long fermentation times are accommodated by addition of substrates such as sucrose.

Alcoholic fermentation of d-xylose by yeasts. [Brettanomyces naardenensis; Candida shehatae; Candida tenuis; Pachysolen tannaphilus, Pichia segobiensis; Pichia stipitis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Toivola, A.; Yarrow, D.; van den Bosch, E.

1984-06-01

Type strains of 200 species of yeasts able to ferment glucose and grow on xylose were screened for fermentation of D-xylose. In most of the strains tested, ethanol production was negligible. Nineteen were found to produce between 0.1 and 1.0 g of ethanol per liter. Strains of the following species produce more than 1 g of ethanol per liter in the fermentation test with 2% xylose: Brettanomyces naardenensis, Candida shehatae, Candida tenuis, Pachysolen tannophilus, Pichia segobiensis, and Pichia stipitis. Subsequent screening of these yeasts for their capacity to ferment D-cellobiose revealed that only Candida tenuis CBS 4435 was a goodmore » fermenter of both xylose and cellobiose under the test conditions used.« less

Functional Conservation of Coenzyme Q Biosynthetic Genes among Yeasts, Plants, and Humans

PubMed Central

Hayashi, Kazuhiro; Ogiyama, Yuki; Yokomi, Kazumasa; Nakagawa, Tsuyoshi; Kaino, Tomohiro; Kawamukai, Makoto

2014-01-01

Coenzyme Q (CoQ) is an essential factor for aerobic growth and oxidative phosphorylation in the electron transport system. The biosynthetic pathway for CoQ has been proposed mainly from biochemical and genetic analyses of Escherichia coli and Saccharomyces cerevisiae; however, the biosynthetic pathway in higher eukaryotes has been explored in only a limited number of studies. We previously reported the roles of several genes involved in CoQ synthesis in the fission yeast Schizosaccharomyces pombe. Here, we expand these findings by identifying ten genes (dps1, dlp1, ppt1, and coq3–9) that are required for CoQ synthesis. CoQ10-deficient S. pombe coq deletion strains were generated and characterized. All mutant fission yeast strains were sensitive to oxidative stress, produced a large amount of sulfide, required an antioxidant to grow on minimal medium, and did not survive at the stationary phase. To compare the biosynthetic pathway of CoQ in fission yeast with that in higher eukaryotes, the ability of CoQ biosynthetic genes from humans and plants (Arabidopsis thaliana) to functionally complement the S. pombe coq deletion strains was determined. With the exception of COQ9, expression of all other human and plant COQ genes recovered CoQ10 production by the fission yeast coq deletion strains, although the addition of a mitochondrial targeting sequence was required for human COQ3 and COQ7, as well as A. thaliana COQ6. In summary, this study describes the functional conservation of CoQ biosynthetic genes between yeasts, humans, and plants. PMID:24911838

Computational Models for Prediction of Yeast Strain Potential for Winemaking from Phenotypic Profiles

PubMed Central

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

Characterization and functional analysis of the MAL and MPH Loci for maltose utilization in some ale and lager yeast strains.

PubMed

Vidgren, Virve; Ruohonen, Laura; Londesborough, John

2005-12-01

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 alpha-glucosides, suggesting the use of broad substrate specificity transporters, such as Agt1p. Maltose transport by three lager strains was weakly inhibited by other alpha-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 alpha-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.

Genetic analysis of Saccharomyces cerevisiae strains isolated from palm wine in eastern Nigeria. Comparison with other African strains.

PubMed

Ezeronye, O U; Legras, J-L

2009-05-01

To study the yeast diversity of Nigerian palm wines by comparison with other African strains. Twenty-three Saccharomyces cerevisiae strains were obtained from palm wine samples collected at four locations in eastern Nigeria, and characterized using different molecular techniques: internal transcribed spacer restriction fragment length polymorphism and sequence analysis, pulsed field gel electrophoresis, inter delta typing and microsatellite multilocus analysis. These techniques revealed that palm wine yeasts represent a group of closely related strains that includes other West African isolates (CBS400, NCYC110, DVPG6044). Population analysis revealed an excess of homozygote strains and an allelic richness similar to wine suggestive of local domestication. Several other African yeast strains were not connected to this group. Ghana sorghum beer strains and other African strains (DBVPG1853 and MUCL28071) displayed strikingly high relatedness with European bread, beer or wine strains, and the genome of strain MUCL30909 contained African and wine-type alleles, indicating its hybrid origin. Nigerian palm wine yeast represents a local specific yeast flora, whereas a European origin or hybrid was suspected for several other Africa isolates. This study presents the first genetic characterization of an autochthonous African palm wine yeast population and confirms the idea that human intervention has favoured yeast migration.

Novel brewing yeast hybrids: creation and application.

PubMed

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

2017-01-01

The natural interspecies Saccharomyces cerevisiae × Saccharomyces eubayanus hybrid yeast is responsible for global lager beer production and is one of the most important industrial microorganisms. Its success in the lager brewing environment is due to a combination of traits not commonly found in pure yeast species, principally low-temperature tolerance, and maltotriose utilization. Parental transgression is typical of hybrid organisms and has been exploited previously for, e.g., the production of wine yeast with beneficial properties. The parental strain S. eubayanus has only been discovered recently and newly created lager yeast strains have not yet been applied industrially. A number of reports attest to the feasibility of this approach and artificially created hybrids are likely to have a significant impact on the future of lager brewing. De novo S. cerevisiae × S. eubayanus hybrids outperform their parent strains in a number of respects, including, but not restricted to, fermentation rate, sugar utilization, stress tolerance, and aroma formation. Hybrid genome function and stability, as well as different techniques for generating hybrids and their relative merits are discussed. Hybridization not only offers the possibility of generating novel non-GM brewing yeast strains with unique properties, but is expected to aid in unraveling the complex evolutionary history of industrial lager yeast.

Cocoa butter-like lipid production ability of non-oleaginous and oleaginous yeasts under nitrogen-limited culture conditions.

PubMed

Wei, Yongjun; Siewers, Verena; Nielsen, Jens

2017-05-01

Cocoa butter (CB) extracted from cocoa beans is the main raw material for chocolate production. However, growing chocolate demands and limited CB production has resulted in a shortage of CB supply. CB is mainly composed of three different kinds of triacylglycerols (TAGs), POP (C16:0-C18:1-C16:0), POS (C16:0-C18:1-C18:0), and SOS (C18:0-C18:1-C18:0). The storage lipids of yeasts, mainly TAGs, also contain relative high-level of C16 and C18 fatty acids and might be used as CB-like lipids (CBL). In this study, we cultivated six different yeasts, including one non-oleaginous yeast strain, Saccharomyces cerevisiae CEN.PK113-7D, and five oleaginous yeast strains, Trichosporon oleaginosus DSM11815, Rhodotorula graminis DSM 27356, Lipomyces starkeyi DSM 70296, Rhodosporidium toruloides DSM 70398, and Yarrowia lipolytica CBS 6124, in nitrogen-limited medium and compared their CBL production ability. Under the same growth conditions, we found that TAGs were the main lipids in all six yeasts and that T. oleaginosus can produce more TAGs than the other five yeasts. Less than 3% of the total TAGs were identified as potential SOS in the six yeasts. However, T. oleaginosus produced 27.8% potential POP and POS at levels of 378 mg TAGs/g dry cell weight, hinting that this yeast may have potential as a CBL production host after further metabolic engineering in future.

Yeasts from sub-Antarctic region: biodiversity, enzymatic activities and their potential as oleaginous microorganisms.

PubMed

Martinez, A; Cavello, I; Garmendia, G; Rufo, C; Cavalitto, S; Vero, S

2016-09-01

Various microbial groups are well known to produce a range of extracellular enzymes and other secondary metabolites. However, the occurrence and importance of investment in such activities have received relatively limited attention in studies of Antarctic soil microbiota. Sixty-one yeasts strains were isolated from King George Island, Antarctica which were characterized physiologically and identified at the molecular level using the D1/D2 region of rDNA. Fifty-eight yeasts (belonging to the genera Cryptococcus, Leucosporidiella, Rhodotorula, Guehomyces, Candida, Metschnikowia and Debaryomyces) were screened for extracellular amylolytic, proteolytic, esterasic, pectinolytic, inulolytic xylanolytic and cellulolytic activities at low and moderate temperatures. Esterase activity was the most common enzymatic activity expressed by the yeast isolates regardless the assay temperature and inulinase was the second most common enzymatic activity. No cellulolytic activity was detected. One yeast identified as Guehomyces pullulans (8E) showed significant activity across six of seven enzymes types tested. Twenty-eight yeast isolates were classified as oleaginous, being the isolate 8E the strain that accumulated the highest levels of saponifiable lipids (42 %).

Yarrowia lipolytica: a model yeast for citric acid production.

PubMed

Cavallo, Ema; Charreau, Hernán; Cerrutti, Patricia; Foresti, María Laura

2017-12-01

Every year more than 2 million tons of citric acid (CA) are produced around the world for industrial uses. Although initially extracted from citrus, the low profitability of the process and the increasing demand soon stimulated the search for more efficient methods to produce CA. Currently, most world CA demand (99%) is satisfied by fermentations with microorganisms, especially filamentous fungi and yeasts. CA production with yeasts has certain advantages over molds (e.g. higher productivity and easier cultivation), which in the last two decades have triggered a clear increase in publications and patents devoted to the use of yeasts in this field. Yarrowia lipolytica has become a model yeast that proved to be successful in different production systems. Considering the current interest evidenced in the literature, the most significant information on CA production using Y. lipolytica is summarized. The relevance on CA yields of key factors such as strains, media formulation, environmental conditions and production regimes is thoroughly discussed, with particular focus on increasing CA productivity. Besides, the possibility of tuning the mentioned variables to reduce concomitant isocitric acid production-the biggest disadvantage of using yeasts-is analyzed. Available methods for CA purification/quantification are also discussed. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Genome Sequence of the Lager-Brewing Yeast Saccharomyces sp. Strain M14, Used in the High-Gravity Brewing Industry in China.

PubMed

Liu, Chunfeng; Li, Qi; Niu, Chengtuo; Zheng, Feiyun; Li, Yongxian; Zhao, Yun; Yin, Xiangsheng

2017-10-26

Lager-brewing yeasts are mainly used for the production of lager beers. Illumina and PacBio-based sequence analyses revealed an approximate genome size of 22.8 Mb, with a GC content of 38.98%, for the Chinese lager-brewing yeast Saccharomyces sp. strain M14. Based on ab initio prediction, 9,970 coding genes were annotated. Copyright © 2017 Liu et al.

First results of GEN-AU: Cloning of Deoxynivalenol- and Zearalenone-inactivating UDP-glucosyltransferase genes fromArabidopsis thaliana and expression in yeast for production of mycotoxin-glucosides.

PubMed

Poppenberger, B; Berthiller, F; Lucyshyn, D; Schuhmacher, R; Krska, R; Adam, G

2005-06-01

First results of the GEN-AU pilot project "Fusarium virulence and plant resistance mechanisms" are reported. Employing genetically engineered yeast strains we have been able to clone genes from the model plantArabidopsis thaliana encoding UDP-glucosyltransferases which can inactivate deoxynivalenol (DON) and zearalenone (ZON). The structure of the metabolites produced by the transformed yeast strains were determined by LC-MS/MS as DON-3O-glucoside and ZON-4O-glucoside, respectively. ZON and derivatives added to glucosyltransferase expressing yeast cultures are converted into the corresponding glucosides in very high yield, opening an efficient way to produce reference materials for these masked mycotoxins.

Exopolysaccharides from yeast: insight into optimal conditions for biosynthesis, chemical composition and functional properties - review.

PubMed

Gientka, Iwona; Błażejak, Stanisław; Stasiak-Różańska, Lidia; Chlebowska-Śmigiel, Anna

2015-01-01

xopolysaccharides (EPS) are not a well-established group of metabolites. An industrial scale    of this EPS production is limited mainly by low yield biosynthesis. Until now, enzymes and biosynthesis pathways, as well as the role of regulatory genes, have not been described. Some of yeast EPS show antitumor, immunostimulatory and antioxidant activity. Others, absorb heavy metals and can function as bioactive components of food. Also, the potential of yeast EPS as thickeners or stabilizers can be found. Optimal conditions for the biosynthesis of yeast exopolysaccharides require strong oxygenation and low temperature of the culture, due to the physiology of the producer strains. The medium should contain sucrose as a carbon source and ammonium sulfate as inorganic nitrogen source, wherein the C:N ratio in the substrate should be 15:1. The cultures are long and the largest accumulation of polymers is observed after 4 or 5 days of culturing. The structure of yeast EPS is complex which affects the strain and culture condition. The EPS from yeast are linear mannans, pullulan, glucooligosaccharides, galactooligosaccharides and other heteropolysaccharides containing α-1,2; α-1,3; α-1,6; β-1,3; β-1,4 bonds. Mannose and glucose have the largest participation of carbohydrates for. t exopolysaccharides (EPS) are not a well-established group of metabolites. An industrial scale    of this EPS production is limited mainly by low yield biosynthesis. Until now, enzymes and biosynthesis pathways, as well as the role of regulatory genes, have not been described. Some of yeast EPS show antitumor, immunostimulatory and antioxidant activity. Others, absorb heavy metals and can function as bioactive components of food. Also, the potential of yeast EPS as thickeners or stabilizers can be found. Optimal conditions for the biosynthesis of yeast exopolysaccharides require strong oxygenation and low temperature of the culture, due to the physiology of the producer strains. The

Differential Adsorption of Ochratoxin A and Anthocyanins by Inactivated Yeasts and Yeast Cell Walls during Simulation of Wine Aging

PubMed Central

Petruzzi, Leonardo; Baiano, Antonietta; De Gianni, Antonio; Sinigaglia, Milena; Corbo, Maria Rosaria; Bevilacqua, Antonio

2015-01-01

The adsorption of ochratoxin A (OTA) by yeasts is a promising approach for the decontamination of musts and wines, but some potential competitive or interactive phenomena between mycotoxin, yeast cells, and anthocyanins might modify the intensity of the phenomenon. The aim of this study was to examine OTA adsorption by two strains of Saccharomyces cerevisiae (the wild strain W13, and the commercial isolate BM45), previously inactivated by heat, and a yeast cell wall preparation. Experiments were conducted using Nero di Troia red wine contaminated with 2 μg/L OTA and supplemented with yeast biomass (20 g/L). The samples were analyzed periodically to assess mycotoxin concentration, chromatic characteristics, and total anthocyanins over 84 days of aging. Yeast cell walls revealed the highest OTA-adsorption in comparison to thermally-inactivated cells (50% vs. 43% toxin reduction), whilst no significant differences were found for the amount of adsorbed anthocyanins in OTA-contaminated and control wines. OTA and anthocyanins adsorption were not competitive phenomena. Unfortunately, the addition of yeast cells to wine could cause color loss; therefore, yeast selection should also focus on this trait to select the best strain. PMID:26516913

[Yeast colonization of urinary catheters and the significance of biofilm formation].

PubMed

Růžička, Filip; Holá, Veronika; Mahelová, Martina; Procházková, Alena

2012-08-01

Urinary catheters are colonized by a wide range of microorganisms, including numerous yeasts. The catheters are usually colonized by more microbial species forming a community - multispecies biofilm. Catheter colonization usually does not affect the patient's clinical status in any significant way. On the other hand, the biofilm can become a source of endogenous infection and its presence can affect functionality of the catheter and formation of urinary stones. Material a A total of 721 urinary catheters were studied. Microorganisms were released from catheters by sonication and subsequently cultured. Their identification was performed with the use of common phenotypic tests, as well as using MALDI TOF. Yeasts whose identification was ambiguous were recognized by sequencing. Biofilm formation was assessed by growth in a microtiter plate. Yeast colonization was proved in 244 urinary catheters. However, a total of 274 yeast strains were isolated. Most of them occurred together with other yeast species and/or bacteria on the catheters, producing multispecies biofilm there. The most frequent species was Candida albicans (a total of 144 isolated strains), followed by Candida glabrata (41), Candida tropicalis (41) and Candida parapsilosis sensu stricto (14). Other isolated species were as follows: Candida kefyr (10), Candida krusei (9), Candida fabianii (6), Candida lusitaniae (5), Candida dubliniensis (3) and Saccharomyces cerevisiae (one case). Most of the yeasts rather readily formed a firmly adhering biofilm layer on artificial surfaces.

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

Flavour production by Saprochaete and Geotrichum yeasts and their close relatives.

PubMed

Grondin, Eric; Shum Cheong Sing, Alain; James, Steve; Nueno-Palop, Carmen; François, Jean Marie; Petit, Thomas

2017-12-15

In this study, a total of 30 yeast strains belonging to the genera Dipodascus, Galactomyces, Geotrichum, Magnusiomyces and Saprochaete were investigated for volatile organic compound production using HS-SPME-GC/MS analysis. The resulting flavour profiles, including 36 esters and 6 alcohols compounds, were statistically evaluated by cluster and PCA analysis. Two main groups of strains were extracted from this analysis, namely a group with a low ability to produce flavour and a group producing mainly alcohols. Two other minor groups of strains including Saprochaete suaveolens, Geotrichum marinum and Saprochaete gigas were diverging significantly from the main groups precisely because they showed a good ability to produce a large diversity of esters. In particular, we found that the Saprochaete genus (and their closed relatives) was characterized by a high production of unsaturated esters arising from partial catabolism of branched chain amino-acids. These esters were produced by eight phylogenetically related strains of Saprochaete genus. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adaptability of lactic acid bacteria and yeasts to sourdoughs prepared from cereals, pseudocereals and cassava and use of competitive strains as starters.

PubMed

Vogelmann, Stephanie A; Seitter, Michael; Singer, Ulrike; Brandt, Markus J; Hertel, Christian

2009-04-15

The adaptability of lactic acid bacteria (LAB) and yeasts to sourdoughs prepared from cereals, pseudocereals and cassava was investigated using PCR-DGGE and bacteriological culture combined with rRNA gene sequence analysis. Sourdoughs were prepared either from flours of the cereals wheat, rye, oat, barley, rice, maize, and millet, or from the pseudocereals amaranth, quinoa, and buckwheat, or from cassava, using a starter consisting of various species of LAB and yeasts. Doughs were propagated until a stable microbiota was established. The dominant LAB and yeast species were Lactobacillus fermentum, Lactobacillus helveticus, Lactobacillus paralimentarius, Lactobacillus plantarum, Lactobacillus pontis, Lactobacillus spicheri, Issatchenkia orientalis and Saccharomyces cerevisiae. The proportion of the species within the microbiota varied. L. paralimentarius dominated in the pseudocereal sourdoughs, L. fermentum, L. plantarum and L. spicheri in the cassava sourdough, and L. fermentum, L. helveticus and L. pontis in the cereal sourdoughs. S. cerevisiae constituted the dominating yeast, except for quinoa sourdough, where I. orientalis also reached similar counts, and buckwheat and oat sourdoughs, where no yeasts could be detected. To assess the usefulness of competitive LAB and yeasts as starters, the fermentations were repeated using flours from rice, maize, millet and the pseudocereals, and by starting the dough fermentation with selected dominant strains. At the end of fermentation, most of starter strains belonged to the dominating microbiota. For the rice, millet and quinoa sourdoughs the species composition was similar to that of the prior fermentation, whereas in the other sourdoughs, the composition differed.

Strategies to select yeast starters cultures for production of flavor compounds in cachaça fermentations.

PubMed

de Souza, Anderson Proust Gonçalves; Vicente, Maristela de Araújo; Klein, Raphael Contelli; Fietto, Luciano Gomes; Coutrim, Maurício Xavier; de Cássia Franco Afonso, Robson José; Araújo, Leandro Dias; da Silva, Paulo Henrique Alves; Bouillet, Leoneide Erica Maduro; Castro, Ieso Miranda; Brandão, Rogelio Lopes

2012-02-01

In this work, we have used classical genetics techniques to find improved starter strains to produce cachaça with superior sensorial quality. Our strategy included the selection of yeast strains resistant to 5,5',5″-trifluor-D: ,L: -leucine (TLF) and cerulenin, since these strains produce higher levels of higher alcohols and esters than parental strains. However, no clear relationship was observed when levels of flavoring compounds were compared with the levels expression of the genes (BAT1, BAT2, ATF2, EEB1 genes) involved with the biosynthesis of flavoring compounds. Furthermore, we determined the stability of phenotypes considered as the best indicators of the quality of the cachaça for a parental strain and its segregants. By applying the principal component analysis, a cluster of segregants, showing a high number of characteristics similar to the parental strain, was recognized. One segregant, that was resistant to TLF and cerulenin, also showed growth stability after six consecutive replications on plates containing high concentrations of sugar and ethanol. "Cachaça" produced at laboratory scale using a parental strain and this segregant showed a higher level of flavoring compounds. Both strains predominated in an open fermentative process through seven cycles, as was shown by mitochondrial restriction fragment length polymorphisms analysis. Based on the physical chemical composition of the obtained products, the results demonstrate the usefulness of the developed strategies for the selection of yeast strains to be used as starters in "cachaça" production.

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. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Yeast and Mammalian Metallothioneins Functionally Substitute for Yeast Copper-Zinc Superoxide Dismutase

NASA Astrophysics Data System (ADS)

Tamai, Katherine T.; Gralla, Edith B.; Ellerby, Lisa M.; Valentine, Joan S.; Thiele, Dennis J.

1993-09-01

Copper-zinc superoxide dismutase catalyzes the disproportionation of superoxide anion to hydrogen peroxide and dioxygen and is thought to play an important role in protecting cells from oxygen toxicity. Saccharomyces cerevisiae strains lacking copper-zinc superoxide dismutase, which is encoded by the SOD1 gene, are sensitive to oxidative stress and exhibit a variety of growth defects including hypersensitivity to dioxygen and to superoxide-generating drugs such as paraquat. We have found that in addition to these known phenotypes, SOD1-deletion strains fail to grow on agar containing the respiratory carbon source lactate. We demonstrate here that expression of the yeast or monkey metallothionein proteins in the presence of copper suppresses the lactate growth defect and some other phenotypes associated with SOD1-deletion strains, indicating that copper metallothioneins substitute for copper-zinc superoxide dismutase in vivo to protect cells from oxygen toxicity. Consistent with these results, we show that yeast metallothionein mRNA levels are dramatically elevated under conditions of oxidative stress. Furthermore, in vitro assays demonstrate that yeast metallothionein, purified or from whole-cell extracts, exhibits copper-dependent antioxidant activity. Taken together, these data suggest that both yeast and mammalian metallothioneins may play a direct role in the cellular defense against oxidative stress by functioning as antioxidants.

Oxygen availability and strain combination modulate yeast growth dynamics in mixed culture fermentations of grape must with Starmerella bacillaris and Saccharomyces cerevisiae.

PubMed

Englezos, Vasileios; Cravero, Francesco; Torchio, Fabrizio; Rantsiou, Kalliopi; Ortiz-Julien, Anne; Lambri, Milena; Gerbi, Vincenzo; Rolle, Luca; Cocolin, Luca

2018-02-01

Starmerella bacillaris (synonym Candida zemplinina) is a non-Saccharomyces yeast that has been proposed as a co-inoculant of selected Saccharomyces cerevisiae strains in mixed culture fermentations to enhance the analytical composition of the wines. In order to acquire further knowledge on the metabolic interactions between these two species, in this study we investigated the impact of oxygen addition and combination of Starm. bacillaris with S. cerevisiae strains on the microbial growth and metabolite production. Fermentations were carried out under two different conditions of oxygen availability. Oxygen availability and strain combination clearly influenced the population dynamics throughout the fermentation. Oxygen concentration increased the survival time of Starm. bacillaris and decreased the growth rate of S. cerevisiae strains in mixed culture fermentations, whereas it did not affect the growth of the latter in pure culture fermentations. This study reveals new knowledge about the influence of oxygen availability on the successional evolution of yeast species during wine fermentation. Copyright © 2017 Elsevier Ltd. All rights reserved.

What do we know about the yeast strains from the Brazilian fuel ethanol industry?

PubMed

Della-Bianca, Bianca Eli; Basso, Thiago Olitta; Stambuk, Boris Ugarte; Basso, Luiz Carlos; Gombert, Andreas Karoly

2013-02-01

The production of fuel ethanol from sugarcane-based raw materials in Brazil is a successful example of a large-scale bioprocess that delivers an advanced biofuel at competitive prices and low environmental impact. Two to three fed-batch fermentations per day, with acid treatment of the yeast cream between consecutive cycles, during 6-8 months of uninterrupted production in a nonaseptic environment are some of the features that make the Brazilian process quite peculiar. Along the past decades, some wild Saccharomyces cerevisiae strains were isolated, identified, characterized, and eventually, reintroduced into the process, enabling us to build up knowledge on these organisms. This information, combined with physiological studies in the laboratory and, more recently, genome sequencing data, has allowed us to start clarifying why and how these strains behave differently from the better known laboratory, wine, beer, and baker's strains. All these issues are covered in this minireview, which also presents a brief discussion on future directions in the field and on the perspectives of introducing genetically modified strains in this industrial process.

Genetic and phenotypic diversity of autochthonous cider yeasts in a cellar from Asturias.

PubMed

Pando Bedriñana, R; Querol Simón, A; Suárez Valles, B

2010-06-01

This paper analyses yeast diversity and dynamics during the production of Asturian cider. Yeasts were isolated from apple juice and at different stages of fermentation in a cellar in Villaviciosa during two Asturian cider-apple harvests. The species identified by ITS-RFLP corresponded to Hanseniaspora valbyensis, Hanseniaspora uvarum, Metschnikowia pulcherrima, Pichia guilliermondii, Candida parapsilosis, Saccharomyces cerevisiae and Saccharomyces bayanus/Saccharomyces pastorianus/Saccharomyces kudriavzevii/Saccharomyces mikatae. The species C. parapsilosis is reported here for the first time in cider. The analysis of Saccharomyces mtDNA patterns showed great diversity, sequential substitution and the presence of a small number of yeast patterns (up to 8), present in both harvests. Killer (patterns nos. 22' and 47), sensitive (patterns nos. 12, 15, 33 and 61) and neutral phenotypes were found among the S. cerevisiae isolates. The detection of beta-glucosidase activity, with arbutin as the sole carbon source, allowed two S. cerevisiae strains (patterns nos. 3' and 19') to be differentiated by means of this enzymatic activity. Yeast strains producing the killer toxin or with beta-glucosidase activity are reported for the first time in autochthonous cider yeasts. 2009 Elsevier Ltd. All rights reserved.

Construction of a self-cloning sake yeast that overexpresses alcohol acetyltransferase gene by a two-step gene replacement protocol.

PubMed

Hirosawa, I; Aritomi, K; Hoshida, H; Kashiwagi, S; Nishizawa, Y; Akada, R

2004-07-01

The commercial application of genetically modified industrial microorganisms has been problematic due to public concerns. We constructed a "self-cloning" sake yeast strain that overexpresses the ATF1 gene encoding alcohol acetyltransferase, to improve the flavor profile of Japanese sake. A constitutive yeast overexpression promoter, TDH3p, derived from the glyceraldehyde-3-phosphate dehydrogenase gene from sake yeast was fused to ATF1; and the 5' upstream non-coding sequence of ATF1 was further fused to TDH3p-ATF1. The fragment was placed on a binary vector, pGG119, containing a drug-resistance marker for transformation and a counter-selection marker for excision of unwanted DNA. The plasmid was integrated into the ATF1 locus of a sake yeast strain. This integration constructed tandem repeats of ATF1 and TDH3p-ATF1 sequences, between which the plasmid was inserted. Loss of the plasmid, which occurs through homologous recombination between either the TDH3p downstream ATF1 repeats or the TDH3p upstream repeat sequences, was selected by growing transformants on counter-selective medium. Recombination between the downstream repeats led to reversion to a wild type strain, but that between the upstream repeats resulted in a strain that possessed TDH3p-ATF1 without the extraneous DNA sequences. The self-cloning TDH3p-ATF1 yeast strain produced a higher amount of isoamyl acetate. This is the first expression-controlled self-cloning industrial yeast.

Strain improvement of chymosin-producing strains of Aspergillus niger var. awamori using parasexual recombination.

PubMed

Bodie, E A; Armstrong, G L; Dunn-Coleman, N S

1994-05-01

Parasexual recombination was used to obtain improved chymosin-producing strains and to perform genetic analysis on existing strains. Chlorate resistance was used to select for a variety of spontaneous nitrate assimilation pathway mutations in strains previously improved for chymosin production using classical strain improvement methods including mutation and screening, and selection for 2-deoxyglucose resistance (dgr). Diploids of these improved strains were generated via parasexual recombination and were isolated on selective media by complementation of nitrate assimilation mutations. A preliminary genetic analysis of diploid and haploid segregants indicated that the dgr trait, resulting in overexpression of chymosin, was recessive. Also, mutations in two different dgr genes resulted in an increased level of chymosin production. When these mutations were combined via parasexual recombination, the resulting haploid segregants produced about 15% more chymosin than either parental strain. CHEF gel electrophoresis was used to determine the chromosomal location of the integrated chymosin DNA sequences, and to verify diploidy in one case where the chromosome composition of two haploid parents differed.

Increased expression of the yeast multidrug resistance ABC transporter Pdr18 leads to increased ethanol tolerance and ethanol production in high gravity alcoholic fermentation

PubMed Central

2012-01-01

Background The understanding of the molecular basis of yeast tolerance to ethanol may guide the design of rational strategies to increase process performance in industrial alcoholic fermentations. A set of 21 genes encoding multidrug transporters from the ATP-Binding Cassette (ABC) Superfamily and Major Facilitator Superfamily (MFS) in S. cerevisiae were scrutinized for a role in ethanol stress resistance. Results A yeast multidrug resistance ABC transporter encoded by the PDR18 gene, proposed to play a role in the incorporation of ergosterol in the yeast plasma membrane, was found to confer resistance to growth inhibitory concentrations of ethanol. PDR18 expression was seen to contribute to decreased 3 H-ethanol intracellular concentrations and decreased plasma membrane permeabilization of yeast cells challenged with inhibitory ethanol concentrations. Given the increased tolerance to ethanol of cells expressing PDR18, the final concentration of ethanol produced during high gravity alcoholic fermentation by yeast cells devoid of PDR18 was lower than the final ethanol concentration produced by the corresponding parental strain. Moreover, an engineered yeast strain in which the PDR18 promoter was replaced in the genome by the stronger PDR5 promoter, leading to increased PDR18 mRNA levels during alcoholic fermentation, was able to attain a 6 % higher ethanol concentration and a 17 % higher ethanol production yield than the parental strain. The improved fermentative performance of yeast cells over-expressing PDR18 was found to correlate with their increased ethanol tolerance and ability to restrain plasma membrane permeabilization induced throughout high gravity fermentation. Conclusions PDR18 gene over-expression increases yeast ethanol tolerance and fermentation performance leading to the production of highly inhibitory concentrations of ethanol. PDR18 overexpression in industrial yeast strains appears to be a promising approach to improve alcoholic

Yeast population dynamics reveal a potential 'collaboration' between Metschnikowia pulcherrima and Saccharomyces uvarum for the production of reduced alcohol wines during Shiraz fermentation.

PubMed

Contreras, A; Curtin, C; Varela, C

2015-02-01

The wine sector is actively seeking strategies and technologies that facilitate the production of wines with lower alcohol content. One of the simplest approaches to achieve this aim would be the use of wine yeast strains which are less efficient at transforming grape sugars into ethanol; however, commercial wine yeasts have very similar ethanol yields. We recently demonstrated that Metschnikowia pulcherrima AWRI1149 was able to produce wine with reduced alcohol concentration when used in sequential inoculation with a wine strain of Saccharomyces cerevisiae. Here, different inoculation regimes were explored to study the effect of yeast population dynamics and potential yeast interactions on the metabolism of M. pulcherrima AWRI1149 during fermentation of non-sterile Shiraz must. Of all inoculation regimes tested, only ferments inoculated with M. pulcherrima AWRI1149 showed reduced ethanol concentration. Population dynamics revealed the presence of several indigenous yeast species and one of these, Saccharomyces uvarum (AWRI 2846), was able to produce wine with reduced ethanol concentration in sterile conditions. Both strains however, were inhibited when a combination of three non-Saccharomyces strains, Hanseniaspora uvarum AWRI863, Pichia kluyveri AWRI1896 and Torulaspora delbrueckii AWRI2845 were inoculated into must, indicating that the microbial community composition might impact on the growth of M. pulcherrima AWRI1149 and S. uvarum AWRI 2846. Our results indicate that mixed cultures of M. pulcherrima AWRI1149 and S. uvarum AWRI2846 enable an additional reduction of wine ethanol concentration compared to the same must fermented with either strain alone. This work thus provides a foundation to develop inoculation regimes for the successful application of non-cerevisiae yeast to the production of wines with reduced alcohol.

Direct fermentation of raw starch using a Kluyveromyces marxianus strain that expresses glucoamylase and alpha-amylase to produce ethanol.

PubMed

Wang, Rongliang; Wang, Dongmei; Gao, Xiaolian; Hong, Jiong

2014-01-01

Raw starch and raw cassava tuber powder were directly and efficiently fermented at elevated temperatures to produce ethanol using the thermotolerant yeast Kluyveromyces marxianus that expresses α-amylase from Aspergillus oryzae as well as α-amylase and glucoamylase from Debaryomyces occidentalis. Among the constructed K. marxianus strains, YRL 009 had the highest efficiency in direct starch fermentation. Raw starch from corn, potato, cassava, or wheat can be fermented at temperatures higher than 40°C. At the optimal fermentation temperature 42°C, YRL 009 produced 66.52 g/L ethanol from 200 g/L cassava starch, which was the highest production among the selected raw starches. This production increased to 79.75 g/L ethanol with a 78.3% theoretical yield (with all cassava starch were consumed) from raw cassava starch at higher initial cell densities. Fermentation was also carried out at 45 and 48°C. By using 200 g/L raw cassava starch, 137.11 and 87.71 g/L sugar were consumed with 55.36 and 32.16 g/L ethanol produced, respectively. Furthermore, this strain could directly ferment 200 g/L nonsterile raw cassava tuber powder (containing 178.52 g/L cassava starch) without additional nutritional supplements to produce 69.73 g/L ethanol by consuming 166.07 g/L sugar at 42°C. YRL 009, which has consolidated bioprocessing ability, is the best strain for fermenting starches at elevated temperatures that has been reported to date. © 2014 American Institute of Chemical Engineers.

Comparison of volatile sulphur compound production by cheese-ripening yeasts from methionine and methionine-cysteine mixtures.

PubMed

López Del Castillo-Lozano, M; Delile, A; Spinnler, H E; Bonnarme, P; Landaud, S

2007-07-01

Production of volatile sulphur compounds (VSC) was assessed in culture media supplemented with L-methionine or L-methionine/L-cysteine mixtures, using five cheese-ripening yeasts: Debaryomyces hansenii DH47(8), Kluyveromyces lactis KL640, Geotrichum candidum GC77, Yarrowia lipolytica YL200 and Saccharomyces cerevisiae SC45(3). All five yeasts produced VSC with L-methionine or L-methionine/L-cysteine, but different VSC profiles were found. GC77 and YL200 produced dimethyldisulphide and trace levels of dimethyltrisulphide while DH47(8), KL640 and SC45(3) produced mainly methionol and low levels of methional. S-methylthioacetate was produced by all the yeasts but at different concentrations. DH47(8), KL640 and SC45(3) also produced other minor VSC including 3-methylthiopropyl acetate, ethyl-3-methylthiopropanoate, a thiophenone, and an oxathiane. However, VSC production diminished in a strain-dependent behaviour when L-cysteine was supplemented, even at a low concentration (0.2 g l(-1)). This effect was due mainly to a significant decrease in L-methionine consumption in all the yeasts except YL200. Hydrogen sulphide produced by L-cysteine catabolism did not seem to contribute to VSC generation at the acid pH of yeast cultures. The significance of such results in the cheese-ripening context is discussed.

Genetic Evidence for a Silent SUC Gene in Yeast

PubMed Central

Carlson, Marian; Osmond, Barbara C.; Botstein, David

1981-01-01

The SUC genes (SUC1–SUC7) of Saccharomyces are a family of genes that are dispersed in the yeast genome. A SUC+ allele at any locus confers the ability to produce the enzyme invertase and, thus, to ferment sucrose. Most yeast strains do not carry SUC+ alleles at all possible SUC loci. We have investigated the naturally occurring negative (suc0) alleles present at SUC loci with the aim of distinguishing between two possible models for the structure of suc0 alleles: (1) suc0 alleles correspond to a simple absence of SUC genetic information; (2) suc0 alleles are "silent" SUC genes that either produce a defective product or are not expressed. To facilitate these studies, sucrose-nonfermenting strains were constructed that are congenic to S. cerevisiae strain S288C (SUC2+), but carry at the SUC2 locus the naturally occurring negative allele, suc20, of strain FL100 (Lacroute 1968). These strains were used to study the genetic properties of the suc20 allele of FL100 and the suc0 alleles (suc10, suc30, etc.) of S288C. The suc20 allele was shown to revert to an active Suc+ state and to provide functional information at three points in the SUC2 gene in recombination experiments; this suc20 gene thus appears to be a "silent" gene. Similar tests for silent SUC genes in S288C (corresponding to loci other than SUC2) failed to reveal any additional silent genes. PMID:7040164

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. © 2012 The Society for Applied Microbiology.

Yeast synthetic biology for the production of recombinant therapeutic proteins.

PubMed

Kim, Hyunah; Yoo, Su Jin; Kang, Hyun Ah

2015-02-01

The production of recombinant therapeutic proteins is one of the fast-growing areas of molecular medicine and currently plays an important role in treatment of several diseases. Yeasts are unicellular eukaryotic microbial host cells that offer unique advantages in producing biopharmaceutical proteins. Yeasts are capable of robust growth on simple media, readily accommodate genetic modifications, and incorporate typical eukaryotic post-translational modifications. Saccharomyces cerevisiae is a traditional baker's yeast that has been used as a major host for the production of biopharmaceuticals; however, several nonconventional yeast species including Hansenula polymorpha, Pichia pastoris, and Yarrowia lipolytica have gained increasing attention as alternative hosts for the industrial production of recombinant proteins. In this review, we address the established and emerging genetic tools and host strains suitable for recombinant protein production in various yeast expression systems, particularly focusing on current efforts toward synthetic biology approaches in developing yeast cell factories for the production of therapeutic recombinant proteins. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permission@oup.com.

Oxygen-limited cellobiose fermentation and the characterization of the cellobiase of an industrial Dekkera/Brettanomyces bruxellensis strain.

PubMed

Reis, Alexandre Libanio Silva; de Fátima Rodrigues de Souza, Raquel; Baptista Torres, Rochane Regina Neves; Leite, Fernanda Cristina Bezerra; Paiva, Patrícia Maria Guedes; Vidal, Esteban Espinosa; de Morais, Marcos Antonio

2014-01-01

The discovery of a novel yeast with a natural capacity to produce ethanol from lignocellulosic substrates (second-generation ethanol) is of great significance for bioethanol technology. While there are some yeast strains capable of assimilating cellobiose in aerobic laboratory conditions, the predominant sugar in the treatment of lignocellulosic material, little is known about this ability in real industrial conditions. Fermentations designed to simulate industrial conditions were conducted in synthetic medium with glucose, sucrose, cellobiose and hydrolyzed pre-treated cane bagasse as a different carbon source, with the aim of further characterizing the fermentation capacity of a promising Dekkera bruxellensis yeast strain, isolated from the bioethanol process in Brazil. As a result, it was found (for the first time in oxygen-limiting conditions) that the strain Dekkera bruxellensis GDB 248 could produce ethanol from cellobiose. Moreover, it was corroborated that the cellobiase activity characterizes the enzyme candidate in semi-purified extracts (β-glucosidase). In addition, it was demonstrated that GDB 248 strain had the capacity to produce a higher acetic acid concentration than ethanol and glycerol, which confirms the absence of the Custer effect with this strain in oxygen-limiting conditions. Moreover, it is also being suggested that D. bruxellensis could benefit Saccharomyces cerevisiae and outcompete it in the industrial environment. In this way, it was confirmed that D. bruxellensis GDB 248 has the potential to produce ethanol from cellobiose, and is a promising strain for the fermentation of lignocellulosic substrates.

21 CFR 184.1983 - Bakers yeast extract.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Bakers yeast extract. 184.1983 Section 184.1983... GRAS § 184.1983 Bakers yeast extract. (a) Bakers yeast extract is the food ingredient resulting from concentration of the solubles of mechanically ruptured cells of a selected strain of yeast, Saccharomyces...

21 CFR 184.1983 - Bakers yeast extract.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Bakers yeast extract. 184.1983 Section 184.1983... Listing of Specific Substances Affirmed as GRAS § 184.1983 Bakers yeast extract. (a) Bakers yeast extract... a selected strain of yeast, Saccharomyces cerevisiae. It may be concentrated or dried. (b) The...

21 CFR 184.1983 - Bakers yeast extract.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Bakers yeast extract. 184.1983 Section 184.1983... Listing of Specific Substances Affirmed as GRAS § 184.1983 Bakers yeast extract. (a) Bakers yeast extract... a selected strain of yeast, Saccharomyces cerevisiae. It may be concentrated or dried. (b) The...

Oxygen Consumption by Postfermentation Wine Yeast Lees: Factors Affecting Its Rate and Extent under Oenological Conditions

PubMed Central

Müller, Jonas; Schmidt, Dominik

2016-01-01

Summary Postfermentation wine yeast lees show antioxidant properties based on their ability to consume dissolved oxygen. The oxygen consumption capacity of suspended yeast lees obtained after fermentations with six commercial active dry yeast strains was investigated in model, white and red wines using fluorescence-based oxygen sensors operating in a nondestructive way. In model solution, the oxygen consumption rate of yeast lees was shown to depend on their amount, yeast strain, sulfur dioxide and temperature. It is slightly lower in red than in white wines. It is strongly decreased by current levels of free sulfur dioxide, thus excluding the complementary use of both as antioxidants in wine. However, in 25 randomly sampled white wines produced under commercial conditions, the rate and extent of oxygen consumption during the first six months of postfermentation had no significant correlation with any of these interacting factors, making it difficult to predict the actual antioxidant effect of yeast lees. In these wines, yeast lees consumed 0 to 47% of the dissolved oxygen. Although total oxygen consumption capacity of yeast lees is not a limiting factor under commercial winemaking conditions, their oxygen consumption proceeds at a limited rate that reduces but cannot totally prevent concomitant chemical oxidation of the wine. PMID:28115896

Oxygen Consumption by Postfermentation Wine Yeast Lees: Factors Affecting Its Rate and Extent under Oenological Conditions.

PubMed

Schneider, Volker; Müller, Jonas; Schmidt, Dominik

2016-12-01

Postfermentation wine yeast lees show antioxidant properties based on their ability to consume dissolved oxygen. The oxygen consumption capacity of suspended yeast lees obtained after fermentations with six commercial active dry yeast strains was investigated in model, white and red wines using fluorescence-based oxygen sensors operating in a nondestructive way. In model solution, the oxygen consumption rate of yeast lees was shown to depend on their amount, yeast strain, sulfur dioxide and temperature. It is slightly lower in red than in white wines. It is strongly decreased by current levels of free sulfur dioxide, thus excluding the complementary use of both as antioxidants in wine. However, in 25 randomly sampled white wines produced under commercial conditions, the rate and extent of oxygen consumption during the first six months of postfermentation had no significant correlation with any of these interacting factors, making it difficult to predict the actual antioxidant effect of yeast lees. In these wines, yeast lees consumed 0 to 47% of the dissolved oxygen. Although total oxygen consumption capacity of yeast lees is not a limiting factor under commercial winemaking conditions, their oxygen consumption proceeds at a limited rate that reduces but cannot totally prevent concomitant chemical oxidation of the wine.

Distribution of dimorphic yeast species in commercial extra virgin olive oil.

PubMed

Zullo, B A; Cioccia, G; Ciafardini, G

2010-12-01

Recent microbiological research has demonstrated the presence of a rich microflora mainly composed of yeasts in the suspended fraction of freshly produced olive oil. Some of the yeasts are considered useful as they improve the organoleptic characteristics of the oil during preservation, whereas others are considered harmful as they can damage the quality of the oil through the hydrolysis of the triglycerides. However, some dimorphic species can also be found among the unwanted yeasts present in the oil, considered to be opportunistic pathogens to man as they have often been isolated from immunocompromised hospital patients. Present research demonstrates the presence of dimorphic yeast forms in 26% of the commercial extra virgin olive oil originating from different geographical areas, where the dimorphic yeasts are represented by 3-99.5% of the total yeasts. The classified isolates belonged to the opportunistic pathogen species Candida parapsilosis and Candida guilliermondii, while among the dimorphic yeasts considered not pathogenic to man, the Candida diddensiae species was highlighted for the first time in olive oil. The majority of the studied yeast strains resulted lipase positive, and can consequently negatively influence the oil quality through the hydrolysis of the triglycerides. Furthermore, all the strains showed a high level of affinity with some organic solvents and a differing production of biofilm in "vitro" corresponded to a greater or lesser hydrophobia of their cells. Laboratory trials indicated that the dimorphic yeasts studied are sensitive towards some components of the oil among which oleic acid, linoleic acid and triolein, whereas a less inhibiting effect was observed with tricaprilin or when the total polyphenols extracted from the oil were used. The observations carried out on a scanning electron microscope (SEM), demonstrated the production of long un-branched pseudohyphae in all the tested dimorphic yeasts when cultivated on nutrient

Improved bioethanol production using fusants of Saccharomyces cerevisiae and xylose-fermenting yeasts.

PubMed

Kumari, Rajni; Pramanik, K

2012-06-01

The present research deals with the development of a hybrid yeast strain with the aim of converting pentose and hexose sugar components of lignocellulosic substrate to bioethanol by fermentation. Different fusant strains were obtained by fusing protoplasts of Saccharomyces cerevisiae and xylose-fermenting yeasts such as Pachysolen tannophilus, Candida shehatae and Pichia stipitis. The fusants were sorted by fluorescent-activated cell sorter and further confirmed by molecular characterization. The fusants were evaluated by fermentation of glucose-xylose mixture and the highest ethanol producing fusant was used for further study to ferment hydrolysates produced by acid pretreatment and enzymatic hydrolysis of cotton gin waste. Among the various fusant and parental strains used under present study, RPR39 was found to be stable and most efficient strain giving maximum ethanol concentration (76.8 ± 0.31 g L(-1)), ethanol productivity (1.06 g L(-1) h(-1)) and ethanol yield (0.458 g g(-1)) by fermentation of glucose-xylose mixture under test conditions. The fusant has also shown encouraging result in fermenting hydrolysates of cotton gin waste with ethanol concentration of 7.08 ± 0.142 g L(-1), ethanol yield of 0.44 g g(-1), productivity of 0.45 g L(-1) h(-1) and biomass yield of 0.40 g g(-1).

Microbiological and physicochemical characterization of small-scale cocoa fermentations and screening of yeast and bacterial strains to develop a defined starter culture.

PubMed

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

2012-08-01

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.

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

Evaluation of Gene Modification Strategies for the Development of Low-Alcohol-Wine Yeasts

PubMed Central

Kutyna, D. R.; Solomon, M. R.; Black, C. A.; Borneman, A.; Henschke, P. A.; Pretorius, I. S.; Chambers, P. J.

2012-01-01

Saccharomyces cerevisiae has evolved a highly efficient strategy for energy generation which maximizes ATP energy production from sugar. This adaptation enables efficient energy generation under anaerobic conditions and limits competition from other microorganisms by producing toxic metabolites, such as ethanol and CO2. Yeast fermentative and flavor capacity forms the biotechnological basis of a wide range of alcohol-containing beverages. Largely as a result of consumer demand for improved flavor, the alcohol content of some beverages like wine has increased. However, a global trend has recently emerged toward lowering the ethanol content of alcoholic beverages. One option for decreasing ethanol concentration is to use yeast strains able to divert some carbon away from ethanol production. In the case of wine, we have generated and evaluated a large number of gene modifications that were predicted, or known, to impact ethanol formation. Using the same yeast genetic background, 41 modifications were assessed. Enhancing glycerol production by increasing expression of the glyceraldehyde-3-phosphate dehydrogenase gene, GPD1, was the most efficient strategy to lower ethanol concentration. However, additional modifications were needed to avoid negatively affecting wine quality. Two strains carrying several stable, chromosomally integrated modifications showed significantly lower ethanol production in fermenting grape juice. Strain AWRI2531 was able to decrease ethanol concentrations from 15.6% (vol/vol) to 13.2% (vol/vol), whereas AWRI2532 lowered ethanol content from 15.6% (vol/vol) to 12% (vol/vol) in both Chardonnay and Cabernet Sauvignon juices. Both strains, however, produced high concentrations of acetaldehyde and acetoin, which negatively affect wine flavor. Further modifications of these strains allowed reduction of these metabolites. PMID:22729542

Exploring grape marc as trove for new thermotolerant and inhibitor-tolerant Saccharomyces cerevisiae strains for second-generation bioethanol production

PubMed Central

2013-01-01

Background Robust yeasts with high inhibitor, temperature, and osmotic tolerance remain a crucial requirement for the sustainable production of lignocellulosic bioethanol. These stress factors are known to severely hinder culture growth and fermentation performance. Results Grape marc was selected as an extreme environment to search for innately robust yeasts because of its limited nutrients, exposure to solar radiation, temperature fluctuations, weak acid and ethanol content. Forty newly isolated Saccharomyces cerevisiae strains gave high ethanol yields at 40°C when inoculated in minimal media at high sugar concentrations of up to 200 g/l glucose. In addition, the isolates displayed distinct inhibitor tolerance in defined broth supplemented with increasing levels of single inhibitors or with a cocktail containing several inhibitory compounds. Both the fermentation ability and inhibitor resistance of these strains were greater than those of established industrial and commercial S. cerevisiae yeasts used as control strains in this study. Liquor from steam-pretreated sugarcane bagasse was used as a key selective condition during the isolation of robust yeasts for industrial ethanol production, thus simulating the industrial environment. The isolate Fm17 produced the highest ethanol concentration (43.4 g/l) from the hydrolysate, despite relatively high concentrations of weak acids, furans, and phenolics. This strain also exhibited a significantly greater conversion rate of inhibitory furaldehydes compared with the reference strain S. cerevisiae 27P. To our knowledge, this is the first report describing a strain of S. cerevisiae able to produce an ethanol yield equal to 89% of theoretical maximum yield in the presence of high concentrations of inhibitors from sugarcane bagasse. Conclusions This study showed that yeasts with high tolerance to multiple stress factors can be obtained from unconventional ecological niches. Grape marc appeared to be an unexplored and

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.

Bioremediation of acidic oily sludge-contaminated soil by the novel yeast strain Candida digboiensis TERI ASN6.

PubMed

Sood, Nitu; Patle, Sonali; Lal, Banwari

2010-03-01

Primitive wax refining techniques had resulted in almost 50,000 tonnes of acidic oily sludge (pH 1-3) being accumulated inside the Digboi refinery premises in Assam state, northeast India. A novel yeast species Candida digboiensis TERI ASN6 was obtained that could degrade the acidic petroleum hydrocarbons at pH 3 under laboratory conditions. The aim of this study was to evaluate the degradation potential of this strain under laboratory and field conditions. The ability of TERI ASN6 to degrade the hydrocarbons found in the acidic oily sludge was established by gravimetry and gas chromatography-mass spectroscopy. Following this, a feasibility study was done, on site, to study various treatments for the remediation of the acidic sludge. Among the treatments, the application of C. digboiensis TERI ASN6 with nutrients showed the highest degradation of the acidic oily sludge. This treatment was then selected for the full-scale bioremediation study conducted on site, inside the refinery premises. The novel yeast strain TERI ASN6 could degrade 40 mg of eicosane in 50 ml of minimal salts medium in 10 days and 72% of heneicosane in 192 h at pH 3. The degradation of alkanes yielded monocarboxylic acid intermediates while the polycyclic aromatic hydrocarbon pyrene found in the acidic oily sludge yielded the oxygenated intermediate pyrenol. In the feasibility study, the application of TERI ASN6 with nutrients showed a reduction of solvent extractable total petroleum hydrocarbon (TPH) from 160 to 28.81 g kg(-1) soil as compared to a TPH reduction from 183.85 to 151.10 g kg(-1) soil in the untreated control in 135 days. The full-scale bioremediation study in a 3,280-m(2) area in the refinery showed a reduction of TPH from 184.06 to 7.96 g kg(-1) soil in 175 days. Degradation of petroleum hydrocarbons by microbes is a well-known phenomenon, but most microbes are unable to withstand the low pH conditions found in Digboi refinery. The strain C. digboiensis could efficiently degrade

Draft Genome Sequence of the Yeast Starmerella bombicola NBRC10243, a Producer of Sophorolipids, Glycolipid Biosurfactants

PubMed Central

Matsuzawa, Tomohiko; Koike, Hideaki; Saika, Azusa; Fukuoka, Tokuma; Sato, Shun; Habe, Hiroshi; Kitamoto, Dai

2015-01-01

The yeast Starmerella bombicola NBRC10243 is an excellent producer of sophorolipids (SLs) from various feedstocks. Here, we report the draft genome sequence of S. bombicola NBRC10243. Analysis of the sequence may provide insight into the properties of this yeast that make it superior for use in the production of functional glycolipids and biomolecules, leading to the further development of S. bombicola NBRC10243 for industrial applications. PMID:25814600

Biosorption of nickel by yeasts in an osmotically unsuitable environment.

PubMed

Breierová, Emilia; Certík, Milan; Kovárová, Annamaria; Gregor, Tomas

2008-01-01

The tolerance, sorption of nickel(II) ions, and changes in the production and composition of exopolymers of eight yeast strains grown under nickel presence with/without NaCl were studied. Strains of Pichia anomala and Candida maltosa known as the most resistant yeasts against nickel tolerated up to 3 mM Ni2+. NaCl addition decreased both the resistance of the yeast strains toward nickel ions and the sorption of metal ions into cells. All yeasts absorbed nickel predominantly into exopolymers (glycoproteins) and on the surface of cells. However, while the amount of polysaccharide moieties of exoglycoproteins of most of the resistant yeasts was induced by stress conditions, the ratio polysaccharide/protein in the exopolymers remained unchanged in the sensitive species Cystofilobasidium. The exopolymer composition might play a key role in yeast adaptation to stress conditions caused by heavy metal ions.

MALDI-TOF MS as a tool to identify foodborne yeasts and yeast-like fungi.

PubMed

Quintilla, Raquel; Kolecka, Anna; Casaregola, Serge; Daniel, Heide M; Houbraken, Jos; Kostrzewa, Markus; Boekhout, Teun; Groenewald, Marizeth

2018-02-02

Since food spoilage by yeasts causes high economic losses, fast and accurate identifications of yeasts associated with food and food-related products are important for the food industry. In this study the efficiency of the matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) to identify food related yeasts was evaluated. A CBS in-house MALDI-TOF MS database was created and later challenged with a blinded test set of 146 yeast strains obtained from food and food related products. Ninety eight percent of the strains were correctly identified with log score values>1.7. One strain, Mrakia frigida, gained a correct identification with a score value<1.7. Two strains could not be identified at first as they represented a mix of two different species. These mixes were Rhodotorula babjevae with Meyerozyma caribbica and Clavispora lusitaniae with Debaryomyces hansenii. After separation, all four species could be correctly identified with scores>1.7. Ambiguous identifications were observed due to two incorrect reference mass spectra's found in the commercial database BDAL v.4.0, namely Candida sake DSM 70763 which was re-identified as Candida oleophila, and Candida inconspicua DSM 70631 which was re-identified as Pichia membranifaciens. MALDI-TOF MS can distinguish between most of the species, but for some species complexes, such as the Kazachstania telluris and Mrakia frigida complexes, MALDI-TOF MS showed limited resolution and identification of sibling species was sometimes problematic. Despite this, we showed that the MALDI-TOF MS is applicable for routine identification and validation of foodborne yeasts, but a further update of the commercial reference databases is needed. Copyright © 2017 Elsevier B.V. All rights reserved.

BAPJ69-4A: a yeast two-hybrid strain for both positive and negative genetic selection.

PubMed

Shaffer, Hally Anne; Rood, Michael Kenneth; Kashlan, Badar; Chang, Eileen I-ling; Doyle, Donald Francis; Azizi, Bahareh

2012-10-01

Genetic selection systems, such as the yeast two-hybrid system, are efficient methods to detect protein-protein and protein-ligand interactions. These systems have been further developed to assess negative interactions, such as inhibition, using the URA3 genetic selection marker. Previously, chemical complementation was used to assess positive selection in Saccharomyces cerevisiae. In this work, a new S. cerevisiae strain, called BAPJ69-4A, containing three selective markers ADE2, HIS3, and URA3 as well as the lacZ gene controlled by Gal4 response elements, was developed and characterized using the retinoid X receptor (RXR) and its ligand 9-cis retinoic acid (9cRA). Further characterization was performed using RXR variants and the synthetic ligand LG335. To assess the functionality of the strain, RXR was compared to the parent strain PJ69-4A in adenine, histidine, and uracil selective media. In positive selection, associating partners that lead to cell growth were observed in all media in the presence of ligand, whereas partners that did not associate due to the absence of ligand displayed no growth. Conversely, in negative selection, partners that did not associate in 5-FOA medium did not display cell death due to the lack of expression of the URA3 gene. The creation of the BAPJ69-4A yeast strain provides a high-throughput selection system, called negative chemical complementation, which can be used for both positive and negative selection, providing a fast, powerful tool for discovering novel ligand receptor pairs for applications in drug discovery and protein engineering. Copyright © 2012 Elsevier B.V. All rights reserved.

Novel starters for old processes: use of Saccharomyces cerevisiae strains isolated from artisanal sourdough for craft beer production at a brewery scale.

PubMed

Marongiu, Antonella; Zara, Giacomo; Legras, Jean-Luc; Del Caro, Alessandra; Mascia, Ilaria; Fadda, Costantino; Budroni, Marilena

2015-01-01

The deliberate inoculation of yeast strains isolated from food matrices such as wine or bread, could allow the transfer of novel properties to beer. In this work, the feasibility of the use of baker's yeast strains as starters for craft beer production has been evaluated at laboratory and brewery scale. Nine out of 12 Saccharomyces cerevisiae strains isolated from artisanal sourdoughs metabolized 2 % maltose, glucose and trehalose and showed growth rates and cell populations higher than those of the brewer's strain Safbrew-S33. Analysis of allelic variation at 12 microsatellite loci clustered seven baker's strains and Safbrew-S33 in the main group of bread isolates. Chemical analyses of beers produced at a brewery scale showed significant differences among the beers produced with the baker's strain S38 or Safbrew-S33, while no significant differences were observed when S38 or the brewer's strain Safbrew-F2 was used for re-fermentation. The sensory profile of beers obtained with S38 or the brewer's yeasts did not show significant differences, thus suggesting that baker's strains of S. cerevisiae could represent a reservoir of biodiversity for the selection of starter strains for craft beer production.

Improvement of lipid production by the oleaginous yeast Rhodosporidium toruloides through UV mutagenesis.

PubMed

Yamada, Ryosuke; Kashihara, Tomomi; Ogino, Hiroyasu

2017-05-01

Oleaginous yeasts are considered a promising alternative lipid source for biodiesel fuel production. In this study, we attempted to improve the lipid productivity of the oleaginous yeast Rhodosporidium toruloides through UV irradiation mutagenesis and selection based on ethanol and H 2 O 2 tolerance or cerulenin, a fatty acid synthetase inhibitor. Glucose consumption, cell growth, and lipid production of mutants were evaluated. The transcription level of genes involved in lipid production was also evaluated in mutants. The ethanol and H 2 O 2 tolerant strain 8766 2-31M and the cerulenin resistant strain 8766 3-11C were generated by UV mutagenesis. The 8766 2-31M mutant showed a higher lipid production rate, and the 8766 3-11C mutant produced a larger amount of lipid and had a higher lipid production rate than the wild type strain. Transcriptional analysis revealed that, similar to the wild type strain, the ACL1 and GND1 genes were expressed at significantly low levels, whereas IDP1 and ME1 were highly expressed. In conclusion, lipid productivity in the oleaginous yeast R. toruloides was successfully improved via UV mutagenesis and selection. The study also identified target genes for improving lipid productivity through gene recombination.

The impact of yeast fermentation on dough matrix properties.

PubMed

Rezaei, Mohammad N; Jayaram, Vinay B; Verstrepen, Kevin J; Courtin, Christophe M

2016-08-01

Most studies on dough properties are performed on yeastless dough to exclude the complicating, time-dependent effect of yeast. Baker's yeast, however, impacts dough matrix properties during fermentation, probably through the production of primary (CO2 and ethanol) and secondary (glycerol, acetic acid and succinic acid) metabolites. The aim of this study is to obtain a better understanding of the changes in yeasted dough behavior introduced by fermentation, by investigating the impact of yeast fermentation on Farinograph dough consistency, dough spread, Kieffer rig dough extensibility and gluten agglomeration behavior in a fermented dough-batter gluten starch separation system. Results show that fermentation leads to a dough with less flow and lower extensibility that breaks more easily under stress and strain. The dough showed less elastic and more plastic deformation behavior. Gluten agglomerates were smaller for yeasted dough than for the unyeasted control. These changes probably have to be attributed to metabolites generated during fermentation. Indeed, organic acids and also ethanol in concentrations produced by yeast were previously shown to have similar effects in yeastless dough. These findings imply the high importance of yeast fermentation metabolites on dough matrix properties in industrial bread production. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

Biosurfactant-producing strains in enhancing solubilization and biodegradation of petroleum hydrocarbons in groundwater.

PubMed

Liu, Hong; Wang, Hang; Chen, Xuehua; Liu, Na; Bao, Suriguge

2014-07-01

Three biosurfactant-producing strains designated as BS-1, BS-3, and BS-4 were screened out from crude oil-contaminated soil using a combination of surface tension measurement and oil spreading method. Thin layer chromatography and infrared analysis indicated that the biosurfactants produced by the three strains were lipopeptide, glycolipid, and phospholipid. The enhancement of solubilization and biodegradation of petroleum hydrocarbons in groundwater employing biosurfactant-producing strains was investigated. The three strain mixtures led to more solubilization of petroleum hydrocarbons in groundwater, and the solubilization rate was 10.5 mg l−1. The combination of biosurfactant-producing strains and petroleum-degrading strains exhibited a higher biodegradation efficiency of 85.4 % than the petroleum-degrading strains (71.2 %). Biodegradation was enhanced the greatest with biosurfactant-producing strains and petroleum-degrading strains in a ratio of 1:1. Fluorescence microscopy images illustrate that the oil dispersed into smaller droplets and emulsified in the presence of biosurfactant-producing strains, which attached to the oil. Thus, the biodegradation of petroleum hydrocarbons in groundwater was enhanced.

Improved fermentation performance of a lager yeast after repair of its AGT1 maltose and maltotriose transporter genes.

PubMed

Vidgren, Virve; Huuskonen, Anne; Virtanen, Hannele; Ruohonen, Laura; Londesborough, John

2009-04-01

The use of more concentrated, so-called high-gravity and very-high-gravity (VHG) brewer's worts for the manufacture of beer has economic and environmental advantages. However, many current strains of brewer's yeasts ferment VHG worts slowly and incompletely, leaving undesirably large amounts of maltose and especially maltotriose in the final beers. alpha-Glucosides are transported into Saccharomyces yeasts by several transporters, including Agt1, which is a good carrier of both maltose and maltotriose. The AGT1 genes of brewer's ale yeast strains encode functional transporters, but the AGT1 genes of the lager strains studied contain a premature stop codon and do not encode functional transporters. In the present work, one or more copies of the AGT1 gene of a lager strain were repaired with DNA sequence from an ale strain and put under the control of a constitutive promoter. Compared to the untransformed strain, the transformants with repaired AGT1 had higher maltose transport activity, especially after growth on glucose (which represses endogenous alpha-glucoside transporter genes) and higher ratios of maltotriose transport activity to maltose transport activity. They fermented VHG (24 degrees Plato) wort faster and more completely, producing beers containing more ethanol and less residual maltose and maltotriose. The growth and sedimentation behaviors of the transformants were similar to those of the untransformed strain, as were the profiles of yeast-derived volatile aroma compounds in the beers.

A fully decompressed synthetic bacteriophage øX174 genome assembled and archived in yeast.

PubMed

Jaschke, Paul R; Lieberman, Erica K; Rodriguez, Jon; Sierra, Adrian; Endy, Drew

2012-12-20

The 5386 nucleotide bacteriophage øX174 genome has a complicated architecture that encodes 11 gene products via overlapping protein coding sequences spanning multiple reading frames. We designed a 6302 nucleotide synthetic surrogate, øX174.1, that fully separates all primary phage protein coding sequences along with cognate translation control elements. To specify øX174.1f, a decompressed genome the same length as wild type, we truncated the gene F coding sequence. We synthesized DNA encoding fragments of øX174.1f and used a combination of in vitro- and yeast-based assembly to produce yeast vectors encoding natural or designer bacteriophage genomes. We isolated clonal preparations of yeast plasmid DNA and transfected E. coli C strains. We recovered viable øX174 particles containing the øX174.1f genome from E. coli C strains that independently express full-length gene F. We expect that yeast can serve as a genomic 'drydock' within which to maintain and manipulate clonal lineages of other obligate lytic phage. Copyright © 2012 Elsevier Inc. All rights reserved.

Exopolysaccharides produced by clinical strains belonging to the Burkholderia cepacia complex.

PubMed

Herasimenka, Yury; Cescutti, Paola; Impallomeni, Giuseppe; Campana, Silvia; Taccetti, Giovanni; Ravenni, Novella; Zanetti, Flavio; Rizzo, Roberto

2007-04-01

In the frame of a research line dedicated to better clarify the role of exopolysaccharides (EPS) in bacterial virulence, EPS produced by species of the Burkholderia cepacia complex (Bcc), namely Burkholderia multivorans, Burkholderia cenocepacia, and a Bcc member of undetermined genomovar, all isolated at the Cystic Fibrosis Regional Centre of Florence (Italy), were investigated for they structural properties. Three strains of B. multivorans, three of B. cenocepacia and one of a Bcc member of undetermined genomovar were isolated from CF patients. The reference strains C1576 and J2315, for genomovar II and III, respectively, were included in the study. The bacteria were grown on solid media, the exopolysaccharides produced were purified, and their structures were determined. In addition, sugar analysis of sputum samples was accomplished to search for EPS produced in vivo. Six strains out of seven produced the exopolysaccharide cepacian, while one strain of B. multivorans produced a completely different polymer, previously known in the literature as PS1. Two strains synthesised very small amounts of EPS. No definitive evidence for the presence of cepacian in sputum samples was found. Most strains examined produced abundant amounts of polysaccharides. Cepacian was the most common EPS isolated and its production was not associated to a particular genomovar.

QTL mapping of sake brewing characteristics of yeast.

PubMed

Katou, Taku; Namise, Masahiro; Kitagaki, Hiroshi; Akao, Takeshi; Shimoi, Hitoshi

2009-04-01

A haploid sake yeast strain derived from the commercial diploid sake yeast strain Kyokai no. 7 showed better characteristics for sake brewing compared to the haploid laboratory yeast strain X2180-1B, including higher production of ethanol and aromatic components. A hybrid of these two strains showed intermediate characteristics in most cases. After sporulation of the hybrid strain, we obtained 100 haploid segregants of the hybrid. Small-scale sake brewing tests of these segregants showed a smooth continuous distribution of the sake brewing characteristics, suggesting that these traits are determined by multiple quantitative trait loci (QTLs). To examine these sake brewing characteristics at the genomic level, we performed QTL analysis of sake brewing characteristics using 142 DNA markers that showed heterogeneity between the two parental strains. As a result, we identified 25 significant QTLs involved in the specification of sake brewing characteristics such as ethanol fermentation and the production of aromatic components.

Selection and Characterization of Potential Baker's Yeast from Indigenous Resources of Nepal

PubMed Central

Timilsina, Parash Mani; Yadav, Archana; Joshi, Yogesh; Bhujel, Sahansila; Adhikari, Rojina; Neupane, Katyayanee

2017-01-01

The study aims to isolate the yeast strains that could be used effectively as baker's yeast and compare them with the commercial baker's yeast available in the market of Nepal. A total of 10 samples including locally available sources like fruits, Murcha, and a local tree “Dar” were collected from different localities of Bhaktapur, Kavre, and Syangja districts of Nepal, respectively. Following enrichment and fermentation of the samples, 26 yeast strains were isolated using selective medium Wallerstein Laboratory Nutrient Agar. From the differential tests which included morphological and microscopic observation and physiological and biochemical characterization such as nitrate reduction and lactose utilization tests, 8 strains were selected as possible Saccharomyces strain. The selected strains were further assessed for their efficient leavening ability by tests such as ethanol tolerance, osmotolerance, invertase test, and stress exclusion test. The three most potent strains ENG, MUR3B, and SUG1 isolated from grape, Murcha, and sugarcane, respectively, were used in the fermentation and baking of dough. These strains also carried a possibility of being used as industrial baker's yeast. PMID:29387490

Selection and Characterization of Potential Baker's Yeast from Indigenous Resources of Nepal.

PubMed

Karki, Tika B; Timilsina, Parash Mani; Yadav, Archana; Pandey, Gyanu Raj; Joshi, Yogesh; Bhujel, Sahansila; Adhikari, Rojina; Neupane, Katyayanee

2017-01-01

The study aims to isolate the yeast strains that could be used effectively as baker's yeast and compare them with the commercial baker's yeast available in the market of Nepal. A total of 10 samples including locally available sources like fruits, Murcha, and a local tree "Dar" were collected from different localities of Bhaktapur, Kavre, and Syangja districts of Nepal, respectively. Following enrichment and fermentation of the samples, 26 yeast strains were isolated using selective medium Wallerstein Laboratory Nutrient Agar. From the differential tests which included morphological and microscopic observation and physiological and biochemical characterization such as nitrate reduction and lactose utilization tests, 8 strains were selected as possible Saccharomyces strain. The selected strains were further assessed for their efficient leavening ability by tests such as ethanol tolerance, osmotolerance, invertase test, and stress exclusion test. The three most potent strains ENG, MUR3B, and SUG1 isolated from grape, Murcha, and sugarcane, respectively, were used in the fermentation and baking of dough. These strains also carried a possibility of being used as industrial baker's yeast.

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

USDA-ARS?s Scientific Manuscript database

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...

The longevity in the yeast Saccharomyces cerevisiae: A comparison of two approaches for assessment the lifespan.

PubMed

Molon, Mateusz; Zadrag-Tecza, Renata; Bilinski, Tomasz

2015-05-08

Longevity of the selected "longevity mutants" of yeast was studied using two methods. The standard method was based on counting the number of daughter cells produced. Modification of that method allowed for establishing the length of life expressed in units of time. It appeared that all the studied "deletion longevity mutants" showed a statistically meaningful increase in the number of daughters produced (replicative lifespan), whereas only one of the mutants, previously regarded as "short lived", showed a meaningful increase in the time of life. The analysis of the available data shows that the time of life of most yeast strains is similar irrespective of their genetic background and mutations, which suggests a quasi-programmed nature of yeast death. Copyright © 2015 Elsevier Inc. All rights reserved.

Biological Dual-Use Research and Synthetic Biology of Yeast.

PubMed

Cirigliano, Angela; Cenciarelli, Orlando; Malizia, Andrea; Bellecci, Carlo; Gaudio, Pasquale; Lioj, Michele; Rinaldi, Teresa

2017-04-01

In recent years, the publication of the studies on the transmissibility in mammals of the H5N1 influenza virus and synthetic genomes has triggered heated and concerned debate within the community of scientists on biological dual-use research; these papers have raised the awareness that, in some cases, fundamental research could be directed to harmful experiments, with the purpose of developing a weapon that could be used by a bioterrorist. Here is presented an overview regarding the dual-use concept and its related international agreements which underlines the work of the Australia Group (AG) Export Control Regime. It is hoped that the principles and activities of the AG, that focuses on export control of chemical and biological dual-use materials, will spread and become well known to academic researchers in different countries, as they exchange biological materials (i.e. plasmids, strains, antibodies, nucleic acids) and scientific papers. To this extent, and with the aim of drawing the attention of the scientific community that works with yeast to the so called Dual-Use Research of Concern, this article reports case studies on biological dual-use research and discusses a synthetic biology applied to the yeast Saccharomyces cerevisiae, namely the construction of the first eukaryotic synthetic chromosome of yeast and the use of yeast cells as a factory to produce opiates. Since this organism is considered harmless and is not included in any list of biological agents, yeast researchers should take simple actions in the future to avoid the sharing of strains and advanced technology with suspicious individuals.

Interactions between Drosophila and its natural yeast symbionts—Is Saccharomyces cerevisiae a good model for studying the fly-yeast relationship?

PubMed Central

Hoang, Don; Kopp, Artyom

2015-01-01

Yeasts play an important role in the biology of the fruit fly, Drosophila melanogaster. In addition to being a valuable source of nutrition, yeasts affect D. melanogaster behavior and interact with the host immune system. Most experiments investigating the role of yeasts in D. melanogaster biology use the baker’s yeast, Saccharomyces cerevisiae. However, S. cerevisiae is rarely found with natural populations of D. melanogaster or other Drosophila species. Moreover, the strain of S. cerevisiae used most often in D. melanogaster experiments is a commercially and industrially important strain that, to the best of our knowledge, was not isolated from flies. Since disrupting natural host–microbe interactions can have profound effects on host biology, the results from D. melanogaster–S. cerevisiae laboratory experiments may not be fully representative of host–microbe interactions in nature. In this study, we explore the D. melanogaster-yeast relationship using five different strains of yeast that were isolated from wild Drosophila populations. Ingested live yeasts have variable persistence in the D. melanogaster gastrointestinal tract. For example, Hanseniaspora occidentalis persists relative to S. cerevisiae, while Brettanomyces naardenensis is removed. Despite these differences in persistence relative to S. cerevisiae, we find that all yeasts decrease in total abundance over time. Reactive oxygen species (ROS) are an important component of the D. melanogaster anti-microbial response and can inhibit S. cerevisiae growth in the intestine. To determine if sensitivity to ROS explains the differences in yeast persistence, we measured yeast growth in the presence and absence of hydrogen peroxide. We find that B. naardenesis is completely inhibited by hydrogen peroxide, while H. occidentalis is not, which is consistent with yeast sensitivity to ROS affecting persistence within the D. melanogaster gastrointestinal tract. We also compared the feeding preference of D

Interactions between Drosophila and its natural yeast symbionts-Is Saccharomyces cerevisiae a good model for studying the fly-yeast relationship?

PubMed

Hoang, Don; Kopp, Artyom; Chandler, James Angus

2015-01-01

Yeasts play an important role in the biology of the fruit fly, Drosophila melanogaster. In addition to being a valuable source of nutrition, yeasts affect D. melanogaster behavior and interact with the host immune system. Most experiments investigating the role of yeasts in D. melanogaster biology use the baker's yeast, Saccharomyces cerevisiae. However, S. cerevisiae is rarely found with natural populations of D. melanogaster or other Drosophila species. Moreover, the strain of S. cerevisiae used most often in D. melanogaster experiments is a commercially and industrially important strain that, to the best of our knowledge, was not isolated from flies. Since disrupting natural host-microbe interactions can have profound effects on host biology, the results from D. melanogaster-S. cerevisiae laboratory experiments may not be fully representative of host-microbe interactions in nature. In this study, we explore the D. melanogaster-yeast relationship using five different strains of yeast that were isolated from wild Drosophila populations. Ingested live yeasts have variable persistence in the D. melanogaster gastrointestinal tract. For example, Hanseniaspora occidentalis persists relative to S. cerevisiae, while Brettanomyces naardenensis is removed. Despite these differences in persistence relative to S. cerevisiae, we find that all yeasts decrease in total abundance over time. Reactive oxygen species (ROS) are an important component of the D. melanogaster anti-microbial response and can inhibit S. cerevisiae growth in the intestine. To determine if sensitivity to ROS explains the differences in yeast persistence, we measured yeast growth in the presence and absence of hydrogen peroxide. We find that B. naardenesis is completely inhibited by hydrogen peroxide, while H. occidentalis is not, which is consistent with yeast sensitivity to ROS affecting persistence within the D. melanogaster gastrointestinal tract. We also compared the feeding preference of D