Suchergebnisse

Grape must is a sugar‐rich habitat for a complex microbiota which is replaced by Saccharomyces cerevisiae strains during the first fermentation stages. Interest on yeast competitive interactions has recently been propelled due to the use of alternative yeasts in the wine industry to respond to new market demands. The main issue resides in the persistence of these yeasts due to the specific competitive activity of S. cerevisiae. To gather deeper knowledge of the molecular mechanisms involved, we performed a comparative transcriptomic analysis during fermentation carried out by a wine S. cerevisiae strain and a strain representative of the cryophilic S. kudriavzevii, which exhibits high genetic and physiological similarities to S. cerevisiae, but also differences of biotechnological interest. In this study, we report that transcriptomic response to the presence of a competitor is stronger in S. cerevisiae than in S. kudriavzevii. Our results demonstrate that a wine S. cerevisiae industrial strain accelerates nutrient uptake and utilization to outcompete the co‐inoculated yeast, and that this process requires cell‐to‐cell contact to occur. Finally, we propose that this competitive phenotype evolved recently, during the adaptation of S. cerevisiae to man‐manipulated fermentative environments, since a non‐wine S. cerevisiae strain, isolated from a North American oak, showed a remarkable low response to competition. ; JAR was supported by a FPI grant from the Ministerio de Economia y Competitividad, Spain (ref. BES‐2013‐066434). This work was funded by grants AGL2015‐67504‐C3‐1‐R and AGL2015‐67504‐C3‐3‐R from the Spanish Government and European Regional Development Fund (ERDF) to AQ and EB respectively. RPT is supported by the aforementioned grant associated to AQ. ; Peer reviewed

Wineries face unprecedented challenges due to new market demands and climate change effects on wine quality. New yeast starters including non-conventional Saccharomyces species, such as S. kudriavzevii, may contribute to deal with some of these challenges. The design of new fermentations using non-conventional yeasts requires an improved understanding of the physiology and metabolism of these cells. Dynamic modeling brings the potential of exploring the most relevant mechanisms and designing optimal processes more systematically. In this work we explore mechanisms by means of a model selection, reduction and cross-validation pipeline which enables to dissect the most relevant fermentation features for the species under consideration, Saccharomyces cerevisiae T73 and Saccharomyces kudriavzevii CR85. The pipeline involved the comparison of a collection of models which incorporate several alternative mechanisms with emphasis on the inhibitory effects due to temperature and ethanol. We focused on defining a minimal model with the minimum number of parameters, to maximize the identifiability and the quality of cross-validation. The selected model was then used to highlight differences in behavior between species. The analysis of model parameters would indicate that the specific growth rate and the transport of hexoses at initial times are higher for S. cervisiae T73 while S. kudriavzevii CR85 diverts more flux for glycerol production and cellular maintenance. As a result, the fermentations with S. kudriavzevii CR85 are typically slower; produce less ethanol but higher glycerol. Finally, we also explored optimal initial inoculation and process temperature to find the best compromise between final product characteristics and fermentation duration. Results reveal that the production of glycerol is distinctive in S. kudriavzevii CR85, it was not possible to achieve the same production of glycerol with S. cervisiae T73 in any of the conditions tested. This result brings the idea that the optimal design of mixed cultures may have an enormous potential for the improvement of final wine quality. ; This project has received funding from the Spanish government (MINECO) and the European Regional Development Fund (ERDF) through the projects IMPROWINE (grant numbers AGL2015-67504-C3-1-R; AGL2015-67504-C3-2-R) to AQ and EB-C and the PROMETEO grant (ref. PROMETEOII/2014/042) from Generalitat Valenciana, Spain, to AQ. JA-d-R was supported by a FPI grant from the Ministerio de Economa y Competitividad, Spain (ref. BES-2013-066434). ; Peer Reviewed

Saccharomyces cerevisiae is the main microorganism responsible for the fermentation of wine. Nevertheless, in the last years wineries are facing new challenges due to current market demands and climate change effects on the wine quality. New yeast starters formed by non-conventional Saccharomyces species (such as S. uvarum or S. kudriavzevii) or their hybrids (S. cerevisiae x S. uvarum and S. cerevisiae x S. kudriavzevii) can contribute to solve some of these challenges. They exhibit good fermentative capabilities at low temperatures, producing wines with lower alcohol and higher glycerol amounts. However, S. cerevisiae can competitively displace other yeast species from wine fermentations, therefore the use of these new starters requires an analysis of their behavior during competition with S. cerevisiae during wine fermentation. In the present study we analyzed the survival capacity of non-cerevisiae strains in competition with S. cerevisiae during fermentation of synthetic wine must at different temperatures. First, we developed a new method, based on QPCR, to quantify the proportion of different Saccharomyces yeasts in mixed cultures. This method was used to assess the effect of competition on the growth fitness. In addition, fermentation kinetics parameters and final wine compositions were also analyzed. We observed that some cryotolerant Saccharomyces yeasts, particularly S. uvarum, seriously compromised S. cerevisiae fitness during competences at lower temperatures, which explains why S. uvarum can replace S. cerevisiae during wine fermentations in European regions with oceanic and continental climates. From an enological point of view, mixed co-cultures between S. cerevisiae and S. paradoxus or S. eubayanus, deteriorated fermentation parameters and the final product composition compared to single S. cerevisiae inoculation. However, in co-inoculated synthetic must in which S. kudriavzevii or S. uvarum coexisted with S. cerevisiae, there were fermentation performance improvements and the final wines contained less ethanol and higher amounts of glycerol. Finally, it is interesting to note that in co-inoculated fermentations, wine strains of S. cerevisiae and S. uvarum performed better than non-wine strains of the same species. ; JA was supported by a FPI grant from the Ministerio de Economía y Competitividad (ref. BES-2013-066434). This work was supported by grants AGL2012-39937-C02-01 and AGL2015-67504-C3-1-R from the Spanish Government and FEDER to AQ, AGL2012-39937-C02-02 and AGL2015-67504-C3-3-R from the Spanish Government and FEDER to EB, and PROMETEO (project PROMETEOII/2014/042) from Generalitat Valenciana to AQ. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). ; Peer reviewed ; Peer Reviewed

Saccharomyces cerevisiae is the main microorganism responsible for the fermentation of wine. Nevertheless, in the last years wineries are facing new challenges due to current market demands and climate change effects on the wine quality. New yeast starters formed by non-conventional Saccharomyces species (such as S. uvarum or S. kudriavzevii) or their hybrids (S. cerevisiae x S. uvarum and S. cerevisiae x S. kudriavzevii) can contribute to solve some of these challenges. They exhibit good fermentative capabilities at low temperatures, producing wines with lower alcohol and higher glycerol amounts. However, S. cerevisiae can competitively displace other yeast species from wine fermentations, therefore the use of these new starters requires an analysis of their behavior during competition with S. cerevisiae during wine fermentation. In the present study we analyzed the survival capacity of non-cerevisiae strains in competition with S. cerevisiae during fermentation of synthetic wine must at different temperatures. First, we developed a new method, based on QPCR, to quantify the proportion of different Saccharomyces yeasts in mixed cultures. This method was used to assess the effect of competition on the growth fitness. In addition, fermentation kinetics parameters and final wine compositions were also analyzed. We observed that some cryotolerant Saccharomyces yeasts, particularly S. uvarum, seriously compromised S. cerevisiae fitness during competences at lower temperatures, which explains why S. uvarum can replace S. cerevisiae during wine fermentations in European regions with oceanic and continental climates. From an enological point of view, mixed co-cultures between S. cerevisiae and S. paradoxus or S. eubayanus, deteriorated fermentation parameters and the final product composition compared to single S. cerevisiae inoculation. However, in co-inoculated synthetic must in which S. kudriavzevii or S. uvarum coexisted with S. cerevisiae, there were fermentation performance improvements and the final wines contained less ethanol and higher amounts of glycerol. Finally, it is interesting to note that in co-inoculated fermentations, wine strains of S. cerevisiae and S. uvarum performed better than non-wine strains of the same species. ; JA was supported by a FPI grant from the Ministerio de Economía y Competitividad (ref. BES-2013-066434). This work was supported by grants AGL2012-39937-C02-01 and AGL2015-67504-C3-1-R from the Spanish Government and FEDER to AQ, AGL2012-39937-C02-02 and AGL2015-67504-C3-3-R from the Spanish Government and FEDER to EB, and PROMETEO (project PROMETEOII/2014/042) from Generalitat Valenciana to AQ. We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI). ; Peer reviewed

Saccharomyces cerevisiae is the most widespread microorganism responsible for wine alcoholic fermentation. Nevertheless, the wine industry is currently facing new challenges, some of them associate with climate change, which have a negative effect on ethanol content and wine quality. Numerous and varied strategies have been carried out to overcome these concerns. From a biotechnological point of view, the use of alternative non-Saccharomyces yeasts, yielding lower ethanol concentrations and sometimes giving rise to new and interesting aroma, is one of the trendiest approaches. However, S. cerevisiae usually outcompetes other Saccharomyces species due to its better adaptation to the fermentative environment. For this reason, we studied for the first time the use of a Saccharomyces kudriavzevii strain, CR85, for co-inoculations at increasing proportions and sequential inoculations, as well as the effect of aeration, to improve its fermentation performance in order to obtain wines with an ethanol yield reduction. An enhanced competitive performance of S. kudriavzevii CR85 was observed when it represented 90% of the cells present in the inoculum. Furthermore, airflow supply of 20 VVH to the fermentation synergistically improved CR85 endurance and, interestingly, a significant ethanol concentration reduction was achieved. ; JA was supported by a FPI grant from the Ministerio de Economía y Competitividad, Spain (ref. BES-2013-066434) and GC was supported by National Council for Scientific and Technological Development (CNPq), Brazil. This work was funded by grants AGL2015-67504-C3-1-R and AGL2015-67504-C3-3-R from the Spanish Government and FEDER to AQ and EB, respectively, and by a PROMETEO grant (ref. PROMETEOII/2014/042) from Generalitat Valenciana, Spain to AQ. ; Peer reviewed

Understanding of thermal adaptation mechanisms in yeast is crucial to develop better-adapted strains to industrial processes, providing more economical and sustainable products. We have analyzed the transcriptomic responses of three Saccharomyces cerevisiae strains, a commercial wine strain, ADY5, a laboratory strain, CEN.PK113-7D and a commercial bioethanol strain, Ethanol Red, grown at non-optimal temperatures under anaerobic chemostat conditions. Transcriptomic analysis of the three strains revealed a huge complexity of cellular mechanisms and responses. Overall, cold exerted a stronger transcriptional response in the three strains comparing with heat conditions, with a higher number of down-regulating genes than of up-regulating genes regardless the strain analyzed. The comparison of the transcriptome at both sub- and supra-optimal temperatures showed the presence of common genes up- or down-regulated in both conditions, but also the presence of common genes up- or down-regulated in the three studied strains. More specifically, we have identified and validated three up-regulated genes at sub-optimal temperature in the three strains, OPI3, EFM6 and YOL014W. Finally, the comparison of the transcriptomic data with a previous proteomic study with the same strains revealed a good correlation between gene activity and protein abundance, mainly at low temperature. Our work provides a global insight into the specific mechanisms involved in temperature adaptation regarding both transcriptome and proteome, which can be a step forward in the comprehension and improvement of yeast thermotolerance. ; This work was supported by the Spanish Government through "Ministerio de Ciencia e Innovación" (MICINN) and "Fondo Europeo de Desarrollo Regional" (FEDER) funds (grant number PCIN-2015-143, PID2019-108722RB-C31) awarded to JMG and by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit. This study has been carried out in the context of the European ...

"Available online 13 May 2022" ; Understanding of thermal adaptation mechanisms in yeast is crucial to develop better-adapted strains to industrial processes, providing more economical and sustainable products. We have analyzed the transcriptomic responses of three Saccharomyces cerevisiae strains, a commercial wine strain, ADY5, a laboratory strain, CEN.PK113-7D and a commercial bioethanol strain, Ethanol Red, grown at non-optimal temperatures under anaerobic chemostat conditions. Transcriptomic analysis of the three strains revealed a huge complexity of cellular mechanisms and responses. Overall, cold exerted a stronger transcriptional response in the three strains comparing with heat conditions, with a higher number of down-regulating genes than of up-regulating genes regardless the strain analyzed. The comparison of the transcriptome at both sub- and supra-optimal temperatures showed the presence of common genes up- or down-regulated in both conditions, but also the presence of common genes up- or down-regulated in the three studied strains. More specifically, we have identified and validated three up-regulated genes at sub-optimal temperature in the three strains, OPI3, EFM6 and YOL014W. Finally, the comparison of the transcriptomic data with a previous proteomic study with the same strains revealed a good correlation between gene activity and protein abundance, mainly at low temperature. Our work provides a global insight into the specific mechanisms involved in temperature adaptation regarding both transcriptome and proteome, which can be a step forward in the comprehension and improvement of yeast thermotolerance. ; This work was supported by the Spanish Government through "Ministerio de Ciencia e Innovación" (MICINN) and "Fondo Europeo de Desarrollo Regional" (FEDER) funds (grant number PCIN-2015-143, PID2019-108722RB-C31) awarded to JMG and by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit. This study has been carried out in ...