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Gonzalez R, Guindal AM, Tronchoni J, Morales P. Biotechnological Approaches to Lowering the Ethanol Yield during Wine Fermentation. Biomolecules 2021; 11:1569. [PMID: 34827567 PMCID: PMC8615690 DOI: 10.3390/biom11111569] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 10/16/2021] [Accepted: 10/20/2021] [Indexed: 11/17/2022] Open
Abstract
One of the most prominent consequences of global climate warming for the wine industry is a clear increase of the sugar content in grapes, and thus the alcohol level in wines. Among the several approaches to address this important issue, this review focuses on biotechnological solutions, mostly relying on the selection and improvement of wine yeast strains for reduced ethanol yields. Other possibilities are also presented. Researchers are resorting to both S. cerevisiae and alternative wine yeast species for the lowering of alcohol yields. In addition to the use of selected strains under more or less standard fermentation conditions, aerobic fermentation is increasingly being explored for this purpose. Genetic improvement is also playing a role in the development of biotechnological tools to counter the increase in the wine alcohol levels. The use of recombinant wine yeasts is restricted to research, but its contribution to the advancement of the field is still relevant. Furthermore, genetic improvement by non-GMO approaches is providing some interesting results, and will probably result in the development of commercial yeast strains with a lower alcohol yield in the near future. The optimization of fermentation processes using natural isolates is, anyway, the most probable source of advancement in the short term for the production of wines with lower alcohol contents.
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Affiliation(s)
- Ramon Gonzalez
- Instituto de Ciencias de la Vid y del Vino (CSIC, Gobierno de la Rioja, Universidad de La Rioja), 26007 La Rioja, Spain; (R.G.); (A.M.G.)
| | - Andrea M. Guindal
- Instituto de Ciencias de la Vid y del Vino (CSIC, Gobierno de la Rioja, Universidad de La Rioja), 26007 La Rioja, Spain; (R.G.); (A.M.G.)
| | - Jordi Tronchoni
- Faculty of Health Sciences, Valencian International University (VIU), 46002 Valencia, Spain;
| | - Pilar Morales
- Instituto de Ciencias de la Vid y del Vino (CSIC, Gobierno de la Rioja, Universidad de La Rioja), 26007 La Rioja, Spain; (R.G.); (A.M.G.)
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2
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Du Q, Liu Y, Song Y, Qin Y. Creation of a Low-Alcohol-Production Yeast by a Mutated SPT15 Transcription Regulator Triggers Transcriptional and Metabolic Changes During Wine Fermentation. Front Microbiol 2021; 11:597828. [PMID: 33381093 PMCID: PMC7768003 DOI: 10.3389/fmicb.2020.597828] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Accepted: 11/23/2020] [Indexed: 11/23/2022] Open
Abstract
There is significant interest in the wine industry to develop methods to reduce the ethanol content of wine. Here the global transcription machinery engineering (gTME) technology was used to engineer a yeast strain with decreased ethanol yield, based on the mutation of the SPT15 gene. We created a strain of Saccharomyces cerevisiae (YS59-409), which possessed ethanol yield reduced by 34.9%; this was accompanied by the increase in CO2, biomass, and glycerol formation. Five mutation sites were identified in the mutated SPT15 gene of YS59-409. RNA-Seq and metabolome analysis of YS59-409 were conducted compared with control strain, suggesting that ribosome biogenesis, nucleotide metabolism, glycolysis flux, Crabtree effect, NAD+/NADH homeostasis and energy metabolism might be regulated by the mutagenesis of SPT15 gene. Furthermore, two genes related to energy metabolism, RGI1 and RGI2, were found to be associated with the weakened ethanol production capacity, although the precise mechanisms involved need to be further elucidated. This study highlighted the importance of applying gTME technology when attempting to reduce ethanol production by yeast, possibly reprogramming yeast’s metabolism at the global level.
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Affiliation(s)
- Qing Du
- College of Enology, Northwest A&F University, Yangling, China.,Shaanxi Engineering Research Center for Viti-Viniculture, Yangling, China.,National Forestry and Grassland Administration Engineering Research Center for Viti-Viniculture, Yangling, China
| | - Yanlin Liu
- College of Enology, Northwest A&F University, Yangling, China.,Shaanxi Engineering Research Center for Viti-Viniculture, Yangling, China.,National Forestry and Grassland Administration Engineering Research Center for Viti-Viniculture, Yangling, China
| | - Yuyang Song
- College of Enology, Northwest A&F University, Yangling, China.,Shaanxi Engineering Research Center for Viti-Viniculture, Yangling, China.,National Forestry and Grassland Administration Engineering Research Center for Viti-Viniculture, Yangling, China
| | - Yi Qin
- College of Enology, Northwest A&F University, Yangling, China.,Shaanxi Engineering Research Center for Viti-Viniculture, Yangling, China.,National Forestry and Grassland Administration Engineering Research Center for Viti-Viniculture, Yangling, China
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3
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Eldarov MA, Mardanov AV. Metabolic Engineering of Wine Strains of Saccharomyces cerevisiae. Genes (Basel) 2020; 11:E964. [PMID: 32825346 PMCID: PMC7565949 DOI: 10.3390/genes11090964] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 08/16/2020] [Accepted: 08/18/2020] [Indexed: 01/26/2023] Open
Abstract
Modern industrial winemaking is based on the use of starter cultures of specialized wine strains of Saccharomyces cerevisiae yeast. Commercial wine strains have a number of advantages over natural isolates, and it is their use that guarantees the stability and reproducibility of industrial winemaking technologies. For the highly competitive wine market with new demands for improved wine quality, it has become increasingly critical to develop new wine strains and winemaking technologies. Novel opportunities for precise wine strain engineering based on detailed knowledge of the molecular nature of a particular trait or phenotype have recently emerged due to the rapid progress in genomic and "postgenomic" studies with wine yeast strains. The review summarizes the current achievements of the metabolic engineering of wine yeast, the results of recent studies and the prospects for the application of genomic editing technologies for improving wine S. cerevisiae strains.
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Affiliation(s)
| | - Andrey V. Mardanov
- Institute of Bioengineering, Research Center of Biotechnology of the Russian Academy of Sciences, 119071 Moscow, Russia;
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4
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Cuello RA, Flores Montero KJ, Mercado LA, Combina M, Ciklic IF. Construction of low-ethanol-wine yeasts through partial deletion of the Saccharomyces cerevisiae PDC2 gene. AMB Express 2017; 7:67. [PMID: 28324615 PMCID: PMC5360750 DOI: 10.1186/s13568-017-0369-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2017] [Accepted: 03/13/2017] [Indexed: 11/10/2022] Open
Abstract
We propose an alternative GMO based strategy to obtain Saccharomyces cerevisiae mutant strains with a slight reduction in their ability to produce ethanol, but with a moderate impact on the yeast metabolism. Through homologous recombination, two truncated Pdc2p proteins Pdc2pΔ344 and Pdc2pΔ519 were obtained and transformed into haploid and diploid lab yeast strains. In the pdc2Δ344 mutants the DNA-binding and transactivation site of the protein remain intact, whereas in pdc2Δ519 only the DNA-binding site is conserved. Compared to the control, the diploid BY4743pdc2Δ519 mutant strain reduced up to 7.4% the total ethanol content in lab scale-vinifications. The residual sugar and volatile acidity was not significantly affected by this ethanol reduction. Remarkably, we got a much higher ethanol reduction of 10 and 15% when the pdc2Δ519 mutation was tested in a native and a commercial wine yeast strain against their respective controls. Our results demonstrate that the insertion of the pdc2Δ519 mutation in wine yeast strains can reduce the ethanol concentration up to 1.89% (v/v) without affecting the fermentation performance. In contrast to non-GMO based strategies, our approach permits the insertion of the pdc2Δ519 mutation in any locally selected wine strain, making possible to produce quality wines with regional characteristics and lower alcohol content. Thus, we consider our work a valuable contribution to the problem of high ethanol concentration in wine.
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Dzialo MC, Park R, Steensels J, Lievens B, Verstrepen KJ. Physiology, ecology and industrial applications of aroma formation in yeast. FEMS Microbiol Rev 2017; 41:S95-S128. [PMID: 28830094 PMCID: PMC5916228 DOI: 10.1093/femsre/fux031] [Citation(s) in RCA: 206] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 06/06/2017] [Indexed: 01/05/2023] Open
Abstract
Yeast cells are often employed in industrial fermentation processes for their ability to efficiently convert relatively high concentrations of sugars into ethanol and carbon dioxide. Additionally, fermenting yeast cells produce a wide range of other compounds, including various higher alcohols, carbonyl compounds, phenolic compounds, fatty acid derivatives and sulfur compounds. Interestingly, many of these secondary metabolites are volatile and have pungent aromas that are often vital for product quality. In this review, we summarize the different biochemical pathways underlying aroma production in yeast as well as the relevance of these compounds for industrial applications and the factors that influence their production during fermentation. Additionally, we discuss the different physiological and ecological roles of aroma-active metabolites, including recent findings that point at their role as signaling molecules and attractants for insect vectors.
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Affiliation(s)
- Maria C Dzialo
- Laboratory for Genetics and Genomics, Centre of Microbial and Plant Genetics (CMPG), KU Leuven, Gaston Geenslaan 1, B-3001 Leuven, Belgium
- Laboratory for Systems Biology, VIB Center for Microbiology, Bio-Incubator, Gaston Geenslaan 1, 3001 Leuven, Belgium
| | - Rahel Park
- Laboratory for Genetics and Genomics, Centre of Microbial and Plant Genetics (CMPG), KU Leuven, Gaston Geenslaan 1, B-3001 Leuven, Belgium
- Laboratory for Systems Biology, VIB Center for Microbiology, Bio-Incubator, Gaston Geenslaan 1, 3001 Leuven, Belgium
| | - Jan Steensels
- Laboratory for Genetics and Genomics, Centre of Microbial and Plant Genetics (CMPG), KU Leuven, Gaston Geenslaan 1, B-3001 Leuven, Belgium
- Laboratory for Systems Biology, VIB Center for Microbiology, Bio-Incubator, Gaston Geenslaan 1, 3001 Leuven, Belgium
| | - Bart Lievens
- Laboratory for Process Microbial Ecology and Bioinspirational Management (PME&BIM), Department of Microbial and Molecular Systems, KU Leuven, Campus De Nayer, Fortsesteenweg 30A B-2860 Sint-Katelijne Waver, Belgium
| | - Kevin J Verstrepen
- Laboratory for Genetics and Genomics, Centre of Microbial and Plant Genetics (CMPG), KU Leuven, Gaston Geenslaan 1, B-3001 Leuven, Belgium
- Laboratory for Systems Biology, VIB Center for Microbiology, Bio-Incubator, Gaston Geenslaan 1, 3001 Leuven, Belgium
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6
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Goold HD, Kroukamp H, Williams TC, Paulsen IT, Varela C, Pretorius IS. Yeast's balancing act between ethanol and glycerol production in low-alcohol wines. Microb Biotechnol 2017; 10:264-278. [PMID: 28083938 PMCID: PMC5328816 DOI: 10.1111/1751-7915.12488] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Revised: 11/17/2016] [Accepted: 11/23/2016] [Indexed: 01/06/2023] Open
Abstract
Alcohol is fundamental to the character of wine, yet too much can put a wine off‐balance. A wine is regarded to be well balanced if its alcoholic strength, acidity, sweetness, fruitiness and tannin structure complement each other so that no single component dominates on the palate. Balancing a wine's positive fruit flavours with the optimal absolute and relative concentration of alcohol can be surprisingly difficult. Over the past three decades, consumers have increasingly demanded wine with richer and riper fruit flavour profiles. In response, grape and wine producers have extended harvest times to increase grape maturity and enhance the degree of fruit flavours and colour intensity. However, a higher degree of grape maturity results in increased grape sugar concentration, which in turn results in wines with elevated alcohol concentration. On average, the alcohol strength of red wines from many warm wine‐producing regions globally rose by about 2% (v/v) during this period. Notwithstanding that many of these ‘full‐bodied, fruit‐forward’ wines are well balanced and sought after, there is also a significant consumer market segment that seeks lighter styles with less ethanol‐derived ‘hotness’ on the palate. Consumer‐focussed wine producers are developing and implementing several strategies in the vineyard and winery to reduce the alcohol concentration in wines produced from well‐ripened grapes. In this context, Saccharomyces cerevisiae wine yeasts have proven to be a pivotal strategy to reduce ethanol formation during the fermentation of grape musts with high sugar content (> 240 g l−1). One of the approaches has been to develop ‘low‐alcohol’ yeast strains which work by redirecting their carbon metabolism away from ethanol production to other metabolites, such as glycerol. This article reviews the current challenges of producing glycerol at the expense of ethanol. It also casts new light on yeast strain development programmes which, bolstered by synthetic genomics, could potentially overcome these challenges.
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Affiliation(s)
- Hugh D Goold
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW, 2109, Australia.,New South Wales Department of Primary Industries, Locked Bag 21, Orange, NSW, 2800, Australia
| | - Heinrich Kroukamp
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW, 2109, Australia
| | - Thomas C Williams
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW, 2109, Australia
| | - Ian T Paulsen
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW, 2109, Australia
| | - Cristian Varela
- The Australian Wine Research Institute, PO Box 197, Adelaide, SA, 5064, Australia
| | - Isak S Pretorius
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW, 2109, Australia
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7
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Nidelet T, Brial P, Camarasa C, Dequin S. Diversity of flux distribution in central carbon metabolism of S. cerevisiae strains from diverse environments. Microb Cell Fact 2016; 15:58. [PMID: 27044358 PMCID: PMC4820951 DOI: 10.1186/s12934-016-0456-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 03/23/2016] [Indexed: 11/10/2022] Open
Abstract
Background S. cerevisiae has attracted considerable interest in recent years as a model for ecology and evolutionary biology, revealing a substantial genetic and phenotypic diversity. However, there is a lack of knowledge on the diversity of metabolic networks within this species. Results To identify the metabolic and evolutionary constraints that shape metabolic fluxes in S. cerevisiae, we used a dedicated constraint-based model to predict the central carbon metabolism flux distribution of 43 strains from different ecological origins, grown in wine fermentation conditions. In analyzing these distributions, we observed a highly contrasted situation in flux variability, with quasi-constancy of the glycolysis and ethanol synthesis yield yet high flexibility of other fluxes, such as the pentose phosphate pathway and acetaldehyde production. Furthermore, these fluxes with large variability showed multimodal distributions that could be linked to strain origin, indicating a convergence between genetic origin and flux phenotype. Conclusions Flux variability is pathway-dependent and, for some flux, a strain origin effect can be found. These data highlight the constraints shaping the yeast operative central carbon network and provide clues for the design of strategies for strain improvement. Electronic supplementary material The online version of this article (doi:10.1186/s12934-016-0456-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Thibault Nidelet
- SPO, INRA, SupAgro, Université de Montpellier, 34060, Montpellier, France.
| | - Pascale Brial
- SPO, INRA, SupAgro, Université de Montpellier, 34060, Montpellier, France
| | - Carole Camarasa
- SPO, INRA, SupAgro, Université de Montpellier, 34060, Montpellier, France
| | - Sylvie Dequin
- SPO, INRA, SupAgro, Université de Montpellier, 34060, Montpellier, France
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8
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Flavor impacts of glycerol in the processing of yeast fermented beverages: a review. Journal of Food Science and Technology 2015; 52:7588-98. [PMID: 26604336 DOI: 10.1007/s13197-015-1977-y] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Revised: 07/05/2015] [Accepted: 07/21/2015] [Indexed: 10/23/2022]
Abstract
Glycerol contributes to the beverage body and fullness. Moreover, it also influences the flavor intensity. As a major byproduct, glycerol not only serves critical roles in yeast osmoregulation and redox balancing, but also acts as the carbon competitor against ethanol in alcoholic fermentation. Therefore, increasing glycerol yield benefits both the flavor and ethanol reduction for the fermented beverages. Glycerol yield has been elevated either by fermentation optimization or by yeast genetic modification. The fermentation optimizations reached maximum 14 g/L glycerol through screening yeast strains and optimizing fermentation parameters. Meanwhile the yeast overexpressing GPD1 (encoding glycerol-3-phosphate dehydrogenase) produced up to 6 folds more glycerol for beer and wine. Except for glycerol improvement, the genetically modified yeasts accumulated dramatically undesirable compounds such as acetaldehyde, acetate and acetoin which are detrimental for beverage flavor. In comparison, the natural high glycerol producers showed strain-specific manner on the yeast-derived aroma compounds like volatile acids, fusel alcohols, esters, and aldehydes. Temperature, sugar concentration, nitrogen composition, oxygen and pH-value, which influence glycerol biosynthesis, also obtained various effects on the production of aromatic compounds. In the current review, we firstly deliberate the organoleptic contributions of glycerol for fermented beverages. Furthermore, glycerol optimization strategies are discussed regarding to the yield improvement, the genes expressions, the overall flavor impacts and the feasibilities in beverage applications. Lastly, for improving beverage flavor by glycerol optimization, a high-throughput platform is proposed to increase the screening capacity of yeast strains and parameters in the processing of fermented beverages.
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9
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Reduction of ethanol yield and improvement of glycerol formation by adaptive evolution of the wine yeast Saccharomyces cerevisiae under hyperosmotic conditions. Appl Environ Microbiol 2014; 80:2623-32. [PMID: 24532067 DOI: 10.1128/aem.03710-13] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
There is a strong demand from the wine industry for methodologies to reduce the alcohol content of wine without compromising wine's sensory characteristics. We assessed the potential of adaptive laboratory evolution strategies under hyperosmotic stress for generation of Saccharomyces cerevisiae wine yeast strains with enhanced glycerol and reduced ethanol yields. Experimental evolution on KCl resulted, after 200 generations, in strains that had higher glycerol and lower ethanol production than the ancestral strain. This major metabolic shift was accompanied by reduced fermentative capacities, suggesting a trade-off between high glycerol production and fermentation rate. Several evolved strains retaining good fermentation performance were selected. These strains produced more succinate and 2,3-butanediol than the ancestral strain and did not accumulate undesirable organoleptic compounds, such as acetate, acetaldehyde, or acetoin. They survived better under osmotic stress and glucose starvation conditions than the ancestral strain, suggesting that the forces that drove the redirection of carbon fluxes involved a combination of osmotic and salt stresses and carbon limitation. To further decrease the ethanol yield, a breeding strategy was used, generating intrastrain hybrids that produced more glycerol than the evolved strain. Pilot-scale fermentation on Syrah using evolved and hybrid strains produced wine with 0.6% (vol/vol) and 1.3% (vol/vol) less ethanol, more glycerol and 2,3-butanediol, and less acetate than the ancestral strain. This work demonstrates that the combination of adaptive evolution and breeding is a valuable alternative to rational design for remodeling the yeast metabolic network.
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10
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Oliveira BM, Barrio E, Querol A, Pérez-Torrado R. Enhanced enzymatic activity of glycerol-3-phosphate dehydrogenase from the cryophilic Saccharomyces kudriavzevii. PLoS One 2014; 9:e87290. [PMID: 24498063 PMCID: PMC3907487 DOI: 10.1371/journal.pone.0087290] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 12/26/2013] [Indexed: 11/18/2022] Open
Abstract
During the evolution of the different species classified within the Saccharomyces genus, each one has adapted to live in different environments. One of the most important parameters that have influenced the evolution of Saccharomyces species is the temperature. Here we have focused on the study of the ability of certain species as Saccharomyces kudriavzevii to grow at low temperatures, in contrast to Saccharomyces cerevisiae. We observed that S. kudriavzevii strains isolated from several regions are able to synthesize higher amounts of glycerol, a molecule that has been shown to accumulate in response to freeze and cold stress. To explain this observation at the molecular level we studied the expression of glycerol biosynthetic pathway genes and we observed a higher expression of GPD1 gene in S. kudriavzevii compared to S. cerevisiae in micro-vinification conditions. We observed higher enzymatic activity of Gpd1p in S. kudriavzevii in response to osmotic and cold stress. Also, we determined that S. kudriavzevii Gpd1p enzyme presents increased catalytic properties that will contribute to increase glycerol production. Finally, we evaluated the glycerol production with S. cerevisiae, S. kudriavzevii or a recombinant Gpd1p variant in the same background and observed that the S. kudriavzevii enzyme produced increased glycerol levels at 12 or 28°C. This suggests that glycerol is increased in S. kudriavzevii mainly due to increased Vmax of the Gpd1p enzyme. All these differences indicate that S. kudriavzevii has changed the metabolism to promote the branch of the glycolytic pathway involved in glycerol production to adapt to low temperature environments and maintain the NAD+/NADH ratio in alcoholic fermentations. This knowledge is industrially relevant due to the potential use, for example, of S. cerevisiae-S. kudriavzevii hybrids in the wine industry where glycerol content is an important quality parameter.
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Affiliation(s)
- Bruno M. Oliveira
- Instituto de Agroquímica y Tecnología de los Alimentos, IATA-CSIC, E-46980, Paterna (Valencia), Spain
| | - Eladio Barrio
- Instituto de Agroquímica y Tecnología de los Alimentos, IATA-CSIC, E-46980, Paterna (Valencia), Spain
- Institut “Cavanilles” de Biodiversitat i Biologia Evolutiva, Universitat de València, València, Spain
| | - Amparo Querol
- Instituto de Agroquímica y Tecnología de los Alimentos, IATA-CSIC, E-46980, Paterna (Valencia), Spain
| | - Roberto Pérez-Torrado
- Instituto de Agroquímica y Tecnología de los Alimentos, IATA-CSIC, E-46980, Paterna (Valencia), Spain
- * E-mail:
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11
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Adjustment of trehalose metabolism in wine Saccharomyces cerevisiae strains to modify ethanol yields. Appl Environ Microbiol 2013; 79:5197-207. [PMID: 23793638 DOI: 10.1128/aem.00964-13] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The ability of Saccharomyces cerevisiae to efficiently produce high levels of ethanol through glycolysis has been the focus of much scientific and industrial activity. Despite the accumulated knowledge regarding glycolysis, the modification of flux through this pathway to modify ethanol yields has proved difficult. Here, we report on the systematic screening of 66 strains with deletion mutations of genes encoding enzymes involved in central carbohydrate metabolism for altered ethanol yields. Five of these strains showing the most prominent changes in carbon flux were selected for further investigation. The genes were representative of trehalose biosynthesis (TPS1, encoding trehalose-6-phosphate synthase), central glycolysis (TDH3, encoding glyceraldehyde-3-phosphate dehydrogenase), the oxidative pentose phosphate pathway (ZWF1, encoding glucose-6-phosphate dehydrogenase), and the tricarboxylic acid (TCA) cycle (ACO1 and ACO2, encoding aconitase isoforms 1 and 2). Two strains exhibited lower ethanol yields than the wild type (tps1Δ and tdh3Δ), while the remaining three showed higher ethanol yields. To validate these findings in an industrial yeast strain, the TPS1 gene was selected as a good candidate for genetic modification to alter flux to ethanol during alcoholic fermentation in wine. Using low-strength promoters active at different stages of fermentation, the expression of the TPS1 gene was slightly upregulated, resulting in a decrease in ethanol production and an increase in trehalose biosynthesis during fermentation. Thus, the mutant screening approach was successful in terms of identifying target genes for genetic modification in commercial yeast strains with the aim of producing lower-ethanol wines.
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12
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Abstract
Brewing beer involves microbial activity at every stage, from raw material production and malting to stability in the package. Most of these activities are desirable, as beer is the result of a traditional food fermentation, but others represent threats to the quality of the final product and must be controlled actively through careful management, the daily task of maltsters and brewers globally. This review collates current knowledge relevant to the biology of brewing yeast, fermentation management, and the microbial ecology of beer and brewing.
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Affiliation(s)
- Nicholas A. Bokulich
- Department of Food Science and Technology, University of California, Davis, California, USA
- Department of Viticulture and Enology, University of California, Davis, California, USA
| | - Charles W. Bamforth
- Department of Food Science and Technology, University of California, Davis, California, USA
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13
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Mutants in the Candida glabrata glycerol channels are sensitized to cell wall stress. EUKARYOTIC CELL 2012; 11:1512-9. [PMID: 23087370 DOI: 10.1128/ec.00231-12] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Many fungal species use glycerol as a compatible solute with which to maintain osmotic homeostasis in response to changes in external osmolarity. In Saccharomyces cerevisiae, intracellular glycerol concentrations are regulated largely by the high osmolarity glycerol (HOG) response pathway, both through induction of glycerol biosynthesis and control of its flux through the plasma membrane Fps1 glycerol channel. The channel activity of Fps1 is also controlled by a pair of positive regulators, Rgc1 and Rgc2. In this study, we demonstrate that Candida glabrata, a fungal pathogen that possesses two Fps1 orthologs and two Rgc1/-2 orthologs, accumulates glycerol in response to hyperosmotic stress. We present an initial characterization of mutants with deletions in the C. glabrata FPS1 (CAGL0C03267 [www.candidagenome.org]) and FPS2 (CAGL0E03894) genes and find that a double mutant accumulates glycerol, experiences constitutive cell wall stress, and is hypersensitive to treatment by caspofungin, an antifungal agent that targets the cell wall. This mutant is cleared more efficiently in mouse infections than is wild-type C. glabrata by caspofungin treatment. Finally, we demonstrate that one of the C. glabrata RGC orthologs complements an S. cerevisiae rgc1 rgc2 null mutant, supporting the conclusion that this regulatory assembly is conserved between these species.
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14
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Evaluation of gene modification strategies for the development of low-alcohol-wine yeasts. Appl Environ Microbiol 2012; 78:6068-77. [PMID: 22729542 DOI: 10.1128/aem.01279-12] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
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 CO(2). 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.
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15
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Gpd1 and Gpd2 fine-tuning for sustainable reduction of glycerol formation in Saccharomyces cerevisiae. Appl Environ Microbiol 2011; 77:5857-67. [PMID: 21724879 DOI: 10.1128/aem.05338-11] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Gpd1 and Gpd2 are the two isoforms of glycerol 3-phosphate dehydrogenase (GPDH), which is the rate-controlling enzyme of glycerol formation in Saccharomyces cerevisiae. The two isoenzymes play crucial roles in osmoregulation and redox balancing. Past approaches to increase ethanol yield at the cost of reduced glycerol yield have most often been based on deletion of either one or two isogenes (GPD1 and GPD2). While single deletions of GPD1 or GPD2 reduced glycerol formation only slightly, the gpd1Δ gpd2Δ double deletion strain produced zero glycerol but showed an osmosensitive phenotype and abolished anaerobic growth. Our current approach has sought to generate "intermediate" phenotypes by reducing both isoenzyme activities without abolishing them. To this end, the GPD1 promoter was replaced in a gpd2Δ background by two lower-strength TEF1 promoter mutants. In the same manner, the activity of the GPD2 promoter was reduced in a gpd1Δ background. The resulting strains were crossed to obtain different combinations of residual GPD1 and GPD2 expression levels. Among our engineered strains we identified four candidates showing improved ethanol yields compared to the wild type. In contrast to a gpd1Δ gpd2Δ double-deletion strain, these strains were able to completely ferment the sugars under quasi-anaerobic conditions in both minimal medium and during simultaneous saccharification and fermentation (SSF) of liquefied wheat mash (wheat liquefact). This result implies that our strains can tolerate the ethanol concentration at the end of the wheat liquefact SSF (up to 90 g liter(-1)). Moreover, a few of these strains showed no significant reduction in osmotic stress tolerance compared to the wild type.
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Population size drives industrial Saccharomyces cerevisiae alcoholic fermentation and is under genetic control. Appl Environ Microbiol 2011; 77:2772-84. [PMID: 21357433 DOI: 10.1128/aem.02547-10] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Alcoholic fermentation (AF) conducted by Saccharomyces cerevisiae has been exploited for millennia in three important human food processes: beer and wine production and bread leavening. Most of the efforts to understand and improve AF have been made separately for each process, with strains that are supposedly well adapted. In this work, we propose a first comparison of yeast AFs in three synthetic media mimicking the dough/wort/grape must found in baking, brewing, and wine making. The fermentative behaviors of nine food-processing strains were evaluated in these media, at the cellular, populational, and biotechnological levels. A large variation in the measured traits was observed, with medium effects usually being greater than the strain effects. The results suggest that human selection targeted the ability to complete fermentation for wine strains and trehalose content for beer strains. Apart from these features, the food origin of the strains did not significantly affect AF, suggesting that an improvement program for a specific food processing industry could exploit the variability of strains used in other industries. Glucose utilization was analyzed, revealing plastic but also genetic variation in fermentation products and indicating that artificial selection could be used to modify the production of glycerol, acetate, etc. The major result was that the overall maximum CO(2) production rate (V(max)) was not related to the maximum CO(2) production rate per cell. Instead, a highly significant correlation between V(max) and the maximum population size was observed in all three media, indicating that human selection targeted the efficiency of cellular reproduction rather than metabolic efficiency. This result opens the way to new strategies for yeast improvement.
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Pagliardini J, Hubmann G, Bideaux C, Alfenore S, Nevoigt E, Guillouet SE. Quantitative evaluation of yeast's requirement for glycerol formation in very high ethanol performance fed-batch process. Microb Cell Fact 2010; 9:36. [PMID: 20492645 PMCID: PMC2887396 DOI: 10.1186/1475-2859-9-36] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 05/21/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Glycerol is the major by-product accounting for up to 5% of the carbon in Saccharomyces cerevisiae ethanolic fermentation. Decreasing glycerol formation may redirect part of the carbon toward ethanol production. However, abolishment of glycerol formation strongly affects yeast's robustness towards different types of stress occurring in an industrial process. In order to assess whether glycerol production can be reduced to a certain extent without jeopardizing growth and stress tolerance, the yeast's capacity to synthesize glycerol was adjusted by fine-tuning the activity of the rate-controlling enzyme glycerol 3-phosphate dehydrogenase (GPDH). Two engineered strains whose specific GPDH activity was significantly reduced by two different degrees were comprehensively characterized in a previously developed Very High Ethanol Performance (VHEP) fed-batch process. RESULTS The prototrophic strain CEN.PK113-7D was chosen for decreasing glycerol formation capacity. The fine-tuned reduction of specific GPDH activity was achieved by replacing the native GPD1 promoter in the yeast genome by previously generated well-characterized TEF promoter mutant versions in a gpd2Delta background. Two TEF promoter mutant versions were selected for this study, resulting in a residual GPDH activity of 55 and 6%, respectively. The corresponding strains were referred to here as TEFmut7 and TEFmut2. The genetic modifications were accompanied to a strong reduction in glycerol yield on glucose; the level of reduction compared to the wild-type was 61% in TEFmut7 and 88% in TEFmut2. The overall ethanol production yield on glucose was improved from 0.43 g g(-1) in the wild type to 0.44 g g(-1) measured in TEFmut7 and 0.45 g g(-1) in TEFmut2. Although maximal growth rate in the engineered strains was reduced by 20 and 30%, for TEFmut7 and TEFmut2 respectively, strains' ethanol stress robustness was hardly affected; i.e. values for final ethanol concentration (117 +/- 4 g L(-1)), growth-inhibiting ethanol concentration (87 +/- 3 g L(-1)) and volumetric ethanol productivity (2.1 +/- 0.15 g l(-1) h(-1)) measured in wild-type remained virtually unchanged in the engineered strains. CONCLUSIONS This work demonstrates the power of fine-tuned pathway engineering, particularly when a compromise has to be found between high product yield on one hand and acceptable growth, productivity and stress resistance on the other hand. Under the conditions used in this study (VHEP fed-batch), the two strains with "fine-tuned" GPD1 expression in a gpd2Delta background showed slightly better ethanol yield improvement than previously achieved with the single deletion strains gpd1Delta or gpd2Delta. Although glycerol reduction is known to be even higher in a gpd1Delta gpd2Delta double deletion strain, our strains could much better cope with process stress as reflected by better growth and viability.
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Affiliation(s)
- Julien Pagliardini
- Université de Toulouse, INSA, UPS, INP, LISBP, 135 Av de Rangueil, F-31077 Toulouse, France
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Jung S, Marelli M, Rachubinski RA, Goodlett DR, Aitchison JD. Dynamic changes in the subcellular distribution of Gpd1p in response to cell stress. J Biol Chem 2009; 285:6739-49. [PMID: 20026609 DOI: 10.1074/jbc.m109.058552] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gpd1p is a cytosolic NAD(+)-dependent glycerol 3-phosphate dehydrogenase that also localizes to peroxisomes and plays an essential role in the cellular response to osmotic stress and a role in redox balance. Here, we show that Gpd1p is directed to peroxisomes by virtue of an N-terminal type 2 peroxisomal targeting signal (PTS2) in a Pex7p-dependent manner. Significantly, localization of Gpd1p to peroxisomes is dependent on the metabolic status of cells and the phosphorylation of aminoacyl residues adjacent to the targeting signal. Exposure of cells to osmotic stress induces changes in the subcellular distribution of Gpd1p to the cytosol and nucleus. This behavior is similar to Pnc1p, which is coordinately expressed with Gpd1p, and under conditions of cell stress changes its subcellular distribution from peroxisomes to the nucleus where it mediates chromatin silencing. Although peroxisomes are necessary for the beta-oxidation of fatty acids in yeast, the localization of Gpd1p to peroxisomes is not. Rather, shifts in the distribution of Gpd1p to different cellular compartments in response to changing cellular status suggests a role for Gpd1p in the spatial regulation of redox potential, a process critical to cell survival, especially under the complex stress conditions expected to occur in the wild.
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Affiliation(s)
- Sunhee Jung
- Institute for Systems Biology, Seattle, Washington 98103, USA
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Stanley D, Fraser S, Chambers PJ, Rogers P, Stanley GA. Generation and characterisation of stable ethanol-tolerant mutants of Saccharomyces cerevisiae. J Ind Microbiol Biotechnol 2009; 37:139-49. [PMID: 19902282 DOI: 10.1007/s10295-009-0655-3] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2009] [Accepted: 10/21/2009] [Indexed: 11/30/2022]
Abstract
Saccharomyces spp. are widely used for ethanologenic fermentations, however yeast metabolic rate and viability decrease as ethanol accumulates during fermentation, compromising ethanol yield. Improving ethanol tolerance in yeast should, therefore, reduce the impact of ethanol toxicity on fermentation performance. The purpose of the current work was to generate and characterise ethanol-tolerant yeast mutants by subjecting mutagenised and non-mutagenised populations of Saccharomyces cerevisiae W303-1A to adaptive evolution using ethanol stress as a selection pressure. Mutants CM1 (chemically mutagenised) and SM1 (spontaneous) had increased acclimation and growth rates when cultivated in sub-lethal ethanol concentrations, and their survivability in lethal ethanol concentrations was considerably improved compared with the parent strain. The mutants utilised glucose at a higher rate than the parent in the presence of ethanol and an initial glucose concentration of 20 g l(-1). At a glucose concentration of 100 g l(-1), SM1 had the highest glucose utilisation rate in the presence or absence of ethanol. The mutants produced substantially more glycerol than the parent and, although acetate was only detectable in ethanol-stressed cultures, both mutants produced more acetate than the parent. It is suggested that the increased ethanol tolerance of the mutants is due to their elevated glycerol production rates and the potential of this to increase the ratio of oxidised and reduced forms of nicotinamide adenine dinucleotide (NAD(+)/NADH) in an ethanol-compromised cell, stimulating glycolytic activity.
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Engineering of 2,3-butanediol dehydrogenase to reduce acetoin formation by glycerol-overproducing, low-alcohol Saccharomyces cerevisiae. Appl Environ Microbiol 2009; 75:3196-205. [PMID: 19329666 DOI: 10.1128/aem.02157-08] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Engineered Saccharomyces cerevisiae strains overexpressing GPD1, which codes for glycerol-3-phosphate dehydrogenase, and lacking the acetaldehyde dehydrogenase Ald6 display large-scale diversion of the carbon flux from ethanol toward glycerol without accumulating acetate. Although GPD1 ald6 strains have great potential for reducing the ethanol contents in wines, one major side effect is the accumulation of acetoin, having a negative sensory impact on wine. Acetoin is reduced to 2,3-butanediol by the NADH-dependent 2,3-butanediol dehydrogenase Bdh1. In order to investigate the influence of potential factors limiting this reaction, we overexpressed BDH1, coding for native NADH-dependent Bdh1, and the engineered gene BDH1(221,222,223), coding for an NADPH-dependent Bdh1 enzyme with the amino acid changes 221 EIA 223 to 221 SRS 223, in a glycerol-overproducing wine yeast. We have shown that both the amount of Bdh1 and the NADH availability limit the 2,3-butanediol dehydrogenase reaction. During wine fermentation, however, the major limiting factor was the level of synthesis of Bdh1. Consistent with this finding, the overproduction of native or engineered Bdh1 made it possible to redirect 85 to 90% of the accumulated acetoin into 2,3-butanediol, a compound with neutral sensory characteristics. In addition, the production of diacetyl, a compound causing off-flavor in alcoholic beverages, whose production is increased in glycerol-overproducing yeast cells, was decreased by half. The production of higher alcohols and esters, which was slightly decreased or unchanged in GPD1 ald6 cells compared to that in the control cells, was not further modified in BDH1 cells. Overall, rerouting carbons toward glycerol and 2,3-butanediol represents a new milestone in the engineering of a low-alcohol yeast with desirable organoleptic features, permitting the decrease of the ethanol contents in wines by up to 3 degrees.
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Abstract
The traditional use of the yeast Saccharomyces cerevisiae in alcoholic fermentation has, over time, resulted in substantial accumulated knowledge concerning genetics, physiology, and biochemistry as well as genetic engineering and fermentation technologies. S. cerevisiae has become a platform organism for developing metabolic engineering strategies, methods, and tools. The current review discusses the relevance of several engineering strategies, such as rational and inverse metabolic engineering, evolutionary engineering, and global transcription machinery engineering, in yeast strain improvement. It also summarizes existing tools for fine-tuning and regulating enzyme activities and thus metabolic pathways. Recent examples of yeast metabolic engineering for food, beverage, and industrial biotechnology (bioethanol and bulk and fine chemicals) follow. S. cerevisiae currently enjoys increasing popularity as a production organism in industrial ("white") biotechnology due to its inherent tolerance of low pH values and high ethanol and inhibitor concentrations and its ability to grow anaerobically. Attention is paid to utilizing lignocellulosic biomass as a potential substrate.
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Heux S, Sablayrolles JM, Cachon R, Dequin S. Engineering a Saccharomyces cerevisiae wine yeast that exhibits reduced ethanol production during fermentation under controlled microoxygenation conditions. Appl Environ Microbiol 2006; 72:5822-8. [PMID: 16957200 PMCID: PMC1563617 DOI: 10.1128/aem.00750-06] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We recently showed that expressing an H(2)O-NADH oxidase in Saccharomyces cerevisiae drastically reduces the intracellular NADH concentration and substantially alters the distribution of metabolic fluxes in the cell. Although the engineered strain produces a reduced amount of ethanol, a high level of acetaldehyde accumulates early in the process (1 g/liter), impairing growth and fermentation performance. To overcome these undesirable effects, we carried out a comprehensive analysis of the impact of oxygen on the metabolic network of the same NADH oxidase-expressing strain. While reducing the oxygen transfer rate led to a gradual recovery of the growth and fermentation performance, its impact on the ethanol yield was negligible. In contrast, supplying oxygen only during the stationary phase resulted in a 7% reduction in the ethanol yield, but without affecting growth and fermentation. This approach thus represents an effective strategy for producing wine with reduced levels of alcohol. Importantly, our data also point to a significant role for NAD(+) reoxidation in controlling the glycolytic flux, indicating that engineered yeast strains expressing an NADH oxidase can be used as a powerful tool for gaining insight into redox metabolism in yeast.
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Affiliation(s)
- Stéphanie Heux
- UMR Sciences pour l'Oenologie, Microbiologie, INRA, 2 place Viala, F-34060 Montpellier Cedex 1, France
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Nevoigt E, Kohnke J, Fischer CR, Alper H, Stahl U, Stephanopoulos G. Engineering of promoter replacement cassettes for fine-tuning of gene expression in Saccharomyces cerevisiae. Appl Environ Microbiol 2006; 72:5266-73. [PMID: 16885275 PMCID: PMC1538763 DOI: 10.1128/aem.00530-06] [Citation(s) in RCA: 173] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The strong overexpression or complete deletion of a gene gives only limited information about its control over a certain phenotype or pathway. Gene function studies based on these methods are therefore incomplete. To effect facile manipulation of gene expression across a full continuum of possible expression levels, we recently created a library of mutant promoters. Here, we provide the detailed characterization of our yeast promoter collection comprising 11 mutants of the strong constitutive Saccharomyces cerevisiae TEF1 promoter. The activities of the mutant promoters range between about 8% and 120% of the activity of the unmutated TEF1 promoter. The differences in reporter gene expression in the 11 mutants were independent of the carbon source used, and real-time PCR confirmed that these differences were due to varying levels of transcription (i.e., caused by varying promoter strengths). In addition to a CEN/ARS plasmid-based promoter collection, we also created promoter replacement cassettes. They enable genomic integration of our mutant promoter collection upstream of any given yeast gene, allowing detailed genotype-phenotype characterizations. To illustrate the utility of the method, the GPD1 promoter of S. cerevisiae was replaced by five TEF1 promoter mutants of different strengths, which allowed analysis of the impact of glycerol 3-phosphate dehydrogenase activity on the glycerol yield.
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Affiliation(s)
- Elke Nevoigt
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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Cambon B, Monteil V, Remize F, Camarasa C, Dequin S. Effects of GPD1 overexpression in Saccharomyces cerevisiae commercial wine yeast strains lacking ALD6 genes. Appl Environ Microbiol 2006; 72:4688-94. [PMID: 16820460 PMCID: PMC1489326 DOI: 10.1128/aem.02975-05] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The utilization of Saccharomyces cerevisiae strains overproducing glycerol and with a reduced ethanol yield is a potentially valuable strategy for producing wine with decreased ethanol content. However, glycerol overproduction is accompanied by acetate accumulation. In this study, we evaluated the effects of the overexpression of GPD1, coding for glycerol-3-phosphate dehydrogenase, in three commercial wine yeast strains in which the two copies of ALD6 encoding the NADP+-dependent Mg2+-activated cytosolic acetaldehyde dehydrogenase have been deleted. Under wine fermentation conditions, the engineered industrial strains exhibit fermentation performance and growth properties similar to those of the wild type. Acetate was produced at concentrations similar to that of the wild-type strains, whereas sugar was efficiently diverted to glycerol. The ethanol yield of the GPD1 ald6 industrial strains was 15 to 20% lower than that in the controls. However, these strains accumulated acetoin at considerable levels due to inefficient reduction to 2,3-butanediol. Due to the low taste and odor thresholds of acetoin and its negative sensorial impact on wine, novel engineering strategies will be required for a proper adjustment of the metabolites at the acetaldehyde branch point.
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Affiliation(s)
- Brigitte Cambon
- UMR Sciences pour l'Oenologie, Microbiologie, INRA, 2 Place Viala, F-34060 Montpellier Cedex 1, France
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Overkamp KM, Bakker BM, Kötter P, Luttik MAH, Van Dijken JP, Pronk JT. Metabolic engineering of glycerol production in Saccharomyces cerevisiae. Appl Environ Microbiol 2002; 68:2814-21. [PMID: 12039737 PMCID: PMC123913 DOI: 10.1128/aem.68.6.2814-2821.2002] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2002] [Accepted: 04/01/2002] [Indexed: 11/20/2022] Open
Abstract
Inactivation of TPI1, the Saccharomyces cerevisiae structural gene encoding triose phosphate isomerase, completely eliminates growth on glucose as the sole carbon source. In tpi1-null mutants, intracellular accumulation of dihydroxyacetone phosphate might be prevented if the cytosolic NADH generated in glycolysis by glyceraldehyde-3-phosphate dehydrogenase were quantitatively used to reduce dihydroxyacetone phosphate to glycerol. We hypothesize that the growth defect of tpi1-null mutants is caused by mitochondrial reoxidation of cytosolic NADH, thus rendering it unavailable for dihydroxyacetone-phosphate reduction. To test this hypothesis, a tpi1delta nde1delta nde2delta gut2delta quadruple mutant was constructed. NDE1 and NDE2 encode isoenzymes of mitochondrial external NADH dehydrogenase; GUT2 encodes a key enzyme of the glycerol-3-phosphate shuttle. It has recently been demonstrated that these two systems are primarily responsible for mitochondrial oxidation of cytosolic NADH in S. cerevisiae. Consistent with the hypothesis, the quadruple mutant grew on glucose as the sole carbon source. The growth on glucose, which was accompanied by glycerol production, was inhibited at high-glucose concentrations. This inhibition was attributed to glucose repression of respiratory enzymes as, in the quadruple mutant, respiratory pyruvate dissimilation is essential for ATP synthesis and growth. Serial transfer of the quadruple mutant on high-glucose media yielded a spontaneous mutant with much higher specific growth rates in high-glucose media (up to 0.10 h(-1) at 100 g of glucose. liter(-1)). In aerated batch cultures grown on 400 g of glucose. liter(-1), this engineered S. cerevisiae strain produced over 200 g of glycerol. liter(-1), corresponding to a molar yield of glycerol on glucose close to unity.
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Affiliation(s)
- Karin M Overkamp
- Kluyver Laboratory of Biotechnology, Delft University of Technology, NL-2628 BC Delft, Amsterdam
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Remize F, Andrieu E, Dequin S. Engineering of the pyruvate dehydrogenase bypass in Saccharomyces cerevisiae: role of the cytosolic Mg(2+) and mitochondrial K(+) acetaldehyde dehydrogenases Ald6p and Ald4p in acetate formation during alcoholic fermentation. Appl Environ Microbiol 2000; 66:3151-9. [PMID: 10919763 PMCID: PMC92127 DOI: 10.1128/aem.66.8.3151-3159.2000] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Acetic acid plays a crucial role in the organoleptic balance of many fermented products. We have investigated the factors controlling the production of acetate by Saccharomyces cerevisiae during alcoholic fermentation by metabolic engineering of the enzymatic steps involved in its formation and its utilization. The impact of reduced pyruvate decarboxylase (PDC), limited acetaldehyde dehydrogenase (ACDH), or increased acetoacetyl coenzyme A synthetase (ACS) levels in a strain derived from a wine yeast strain was studied during alcoholic fermentation. In the strain with the PDC1 gene deleted exhibiting 25% of the PDC activity of the wild type, no significant differences were observed in the acetate yield or in the amounts of secondary metabolites formed. A strain overexpressing ACS2 and displaying a four- to sevenfold increase in ACS activity did not produce reduced acetate levels. In contrast, strains with one or two disrupted copies of ALD6, encoding the cytosolic Mg(2+)-activated NADP-dependent ACDH and exhibiting 60 and 30% of wild-type ACDH activity, showed a substantial decrease in acetate yield (the acetate production was 75 and 40% of wild-type production, respectively). This decrease was associated with a rerouting of carbon flux towards the formation of glycerol, succinate, and butanediol. The deletion of ALD4, encoding the mitochondrial K(+)-activated NAD(P)-linked ACDH, had no effect on the amount of acetate formed. In contrast, a strain lacking both Ald6p and Ald4p exhibited a long delay in growth and acetate production, suggesting that Ald4p can partially replace the Ald6p isoform. Moreover, the ald6 ald4 double mutant was still able to ferment large amounts of sugar and to produce acetate, suggesting the contribution of another member(s) of the ALD family.
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Affiliation(s)
- F Remize
- Laboratoire de Microbiologie et Technologie des Fermentations, INRA-IPV, F-34060 Montpellier Cedex 2, France
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Abstract
Comprehensive knowledge regarding Saccharomyces cerevisiae has accumulated over time, and today S. cerevisiae serves as a widley used biotechnological production organism as well as a eukaryotic model system. The high transformation efficiency, in addition to the availability of the complete yeast genome sequence, has facilitated genetic manipulation of this microorganism, and new approaches are constantly being taken to metabolicially engineer this organism in order to suit specific needs. In this paper, strategies and concepts for metabolic engineering are discussed and several examples based upon selected studies involving S. cerevisiae are reviewed. The many different studies of metabolic engineering using this organism illustrate all the categories of this multidisciplinary field: extension of substrate range, improvements of producitivity and yield, elimination of byproduct formation, improvement of process performance, improvements of cellular properties, and extension of product range including heterologous protein production.
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Affiliation(s)
- S Ostergaard
- Center for Process Biotechnology, Department of Biotechnology, Technical University of Denmark, DK-2800 Lyngby, Denmark
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