Physiological Features of Saccharomyces cerevisiae and Alternative Wine Yeast Species in Relation to Alcohol Level Reduction in Wine
One of the major problems of the wine industry in warm climate countries is the increasing alcohol content in wines, experienced during the last decades; which is the result of increasing sugar content in grapes at harvest time. This problem is mainly related with global climate change, but it is al...
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Universidad de La Rioja (España)
2019
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One of the major problems of the wine industry in warm climate countries is the increasing alcohol content in wines, experienced during the last decades; which is the result of increasing sugar content in grapes at harvest time. This problem is mainly related with global climate change, but it is also connected to the changing preferences of consumers for full-bodied wines and strong aroma. However, due to health and road safety considerations, as well as to tax policies in some importing countries, the market is also demanding for wines with lower ethanol content.
There are many points in the vine growing and winemaking workflow that can be targeted to reduce the alcohol content of the final wine. In this thesis I focused on the fermentation step, in which sugars are converted into ethanol by the activity of yeasts, mainly Saccharomyces cerevisiae. Previous work in this research group centered on respiration as the most promising yeast metabolic pathway that would have to be increased in order to divert carbon flow from ethanol production. Considering the Crabtree features of this yeast species, the use of non-Saccharomyces species was required.
One major problem found to implement this approach at the industrial level was acetic acid production by S. cerevisiae, which is greatly enhanced in the presence of oxygen. Since this species is usually present in grape must, even in the absence of inoculation, and tend to dominate after some hours of fermentation, providing oxygen to natural grape juice brings about the risk of excess volatile acidity of the final wines, which would preclude commercialization despite any eventual success concerning alcohol reduction.
In order to advance in the development of efficient yeast strains and fermentation procedures aiming to alcohol reduction in wine, while avoiding the drawbacks related with acetic acid production, my PhD work targeted both S. cerevisiae and non-Saccharomyces species. The focus of my work on non-Saccharomyces yeast strains was on understanding the physiology of aerobic growth on grape must for these species, including factors that affect alcohol and acetate yields, and the impact of these growth conditions at the transcriptome level. In the case of S. cerevisiae, I tried to understand by a combination of computational biology and genetic engineering approaches the genetic determinants of excess acetate production when cultures are aerated.
The results obtained indicate that environmental factors that can be easily manipulated during wine fermentation have a huge impact on the yields of acetic acid and alcohol for all yeast species tested. In addition, I was able to identify several genes whose deletion results in reducing the problem of acetic acid production by aerated cultures of S. cerevisiae. These results will serve to guide the development of fermentation procedures using some non-Saccharomyces species, aiming to alcohol level reduction by respiration. On the other side, the information is serving to develop non-GMO S. cerevisiae derivatives that are improved for acetic acid production (reduced yield) and can be combined with non-Saccharomyces yeasts during the aerated step or used as pure cultures for alcohol level reduction. |
| author2 |
González García, Ramón (null) |
| author_facet |
González García, Ramón (null) Rodrigues, Alda Joao Sousa |
| format |
text (thesis) |
| author |
Rodrigues, Alda Joao Sousa |
| spellingShingle |
Rodrigues, Alda Joao Sousa Physiological Features of Saccharomyces cerevisiae and Alternative Wine Yeast Species in Relation to Alcohol Level Reduction in Wine |
| author_sort |
Rodrigues, Alda Joao Sousa |
| title |
Physiological Features of Saccharomyces cerevisiae and Alternative Wine Yeast Species in Relation to Alcohol Level Reduction in Wine |
| title_short |
Physiological Features of Saccharomyces cerevisiae and Alternative Wine Yeast Species in Relation to Alcohol Level Reduction in Wine |
| title_full |
Physiological Features of Saccharomyces cerevisiae and Alternative Wine Yeast Species in Relation to Alcohol Level Reduction in Wine |
| title_fullStr |
Physiological Features of Saccharomyces cerevisiae and Alternative Wine Yeast Species in Relation to Alcohol Level Reduction in Wine |
| title_full_unstemmed |
Physiological Features of Saccharomyces cerevisiae and Alternative Wine Yeast Species in Relation to Alcohol Level Reduction in Wine |
| title_sort |
physiological features of saccharomyces cerevisiae and alternative wine yeast species in relation to alcohol level reduction in wine |
| publisher |
Universidad de La Rioja (España) |
| publishDate |
2019 |
| url |
https://dialnet.unirioja.es/servlet/oaites?codigo=221181 |
| work_keys_str_mv |
AT rodriguesaldajoaosousa physiologicalfeaturesofsaccharomycescerevisiaeandalternativewineyeastspeciesinrelationtoalcohollevelreductioninwine |
| _version_ |
1718346675822526464 |
| spelling |
oai-TES00000228842019-05-04Physiological Features of Saccharomyces cerevisiae and Alternative Wine Yeast Species in Relation to Alcohol Level Reduction in WineRodrigues, Alda Joao SousaOne of the major problems of the wine industry in warm climate countries is the increasing alcohol content in wines, experienced during the last decades; which is the result of increasing sugar content in grapes at harvest time. This problem is mainly related with global climate change, but it is also connected to the changing preferences of consumers for full-bodied wines and strong aroma. However, due to health and road safety considerations, as well as to tax policies in some importing countries, the market is also demanding for wines with lower ethanol content. There are many points in the vine growing and winemaking workflow that can be targeted to reduce the alcohol content of the final wine. In this thesis I focused on the fermentation step, in which sugars are converted into ethanol by the activity of yeasts, mainly Saccharomyces cerevisiae. Previous work in this research group centered on respiration as the most promising yeast metabolic pathway that would have to be increased in order to divert carbon flow from ethanol production. Considering the Crabtree features of this yeast species, the use of non-Saccharomyces species was required. One major problem found to implement this approach at the industrial level was acetic acid production by S. cerevisiae, which is greatly enhanced in the presence of oxygen. Since this species is usually present in grape must, even in the absence of inoculation, and tend to dominate after some hours of fermentation, providing oxygen to natural grape juice brings about the risk of excess volatile acidity of the final wines, which would preclude commercialization despite any eventual success concerning alcohol reduction. In order to advance in the development of efficient yeast strains and fermentation procedures aiming to alcohol reduction in wine, while avoiding the drawbacks related with acetic acid production, my PhD work targeted both S. cerevisiae and non-Saccharomyces species. The focus of my work on non-Saccharomyces yeast strains was on understanding the physiology of aerobic growth on grape must for these species, including factors that affect alcohol and acetate yields, and the impact of these growth conditions at the transcriptome level. In the case of S. cerevisiae, I tried to understand by a combination of computational biology and genetic engineering approaches the genetic determinants of excess acetate production when cultures are aerated. The results obtained indicate that environmental factors that can be easily manipulated during wine fermentation have a huge impact on the yields of acetic acid and alcohol for all yeast species tested. In addition, I was able to identify several genes whose deletion results in reducing the problem of acetic acid production by aerated cultures of S. cerevisiae. These results will serve to guide the development of fermentation procedures using some non-Saccharomyces species, aiming to alcohol level reduction by respiration. On the other side, the information is serving to develop non-GMO S. cerevisiae derivatives that are improved for acetic acid production (reduced yield) and can be combined with non-Saccharomyces yeasts during the aerated step or used as pure cultures for alcohol level reduction.Uno de los principales problemas de la industria enológica en países de clima cálido es el incremento que se ha producido en las últimas décadas en el contenido alcohólico de los vinos, que deriva a su vez del mayor contenido en azúcares de las uvas en el momento de la vendimia. Este problema está principalmente relacionado con el cambio climático global, pero también con el cambio en las preferencias de los consumidores hacia vinos con mayor cuerpo y potencial aromático. Sin embargo, teniendo en cuenta consideraciones de salud y seguridad vial, así como las políticas de impuestos sobre bebidas alcohólicas en algunos países importadores, el mercado está demandando a su vez vinos con menor contenido alcohólico. Hay varios puntos de la cadena de valor viña-vino que pueden ser objeto de mejora ara reducir el contenido alcohólico de los vinos. En esta tesis me he concentrado sobre la etapa de fermentación, en la cual los azúcares son transformados en etanol debido a la actividad de las levaduras, especialmente Saccharomyces cerevisiae. El trabajo previo en este grupo de investigación identificó la respiración como la vía metabólica más prometedora que se podría fomentar para desviar el flujo de carbono de la producción de etanol. Teniendo en cuenta las características Crabtree de esta especie de levadura, este objetivo requiere el uso de levaduras no-Saccharomyces. Uno de los principales problemas encontrados para implementar esta estrategia a escala industrial fue la producción de ácido acético por parte de S. cerevisiae, que se incrementa en gran manera en presencia de oxígeno. Dado que esta especie está presente en el mosto en prácticamente todas las ocasiones, incluso aunque no se inocule, y tiende a dominar el proceso al cabo de algunas horas de fermentación, proporcionar oxígeno al mosto natural, para favorecer la respiración de las levaduras non-Saccharomyces, casi siempre acarrea un riesgo de dar lugar a un exceso de acidez volátil que impediría la comercialización del vino, a pesar de la reducción de alcohol. Para avanzar en el desarrollo de levaduras y procesos de fermentación que permitan reducir el grado alcohólico, pero evitando el inconveniente del ácido acético, mi tesis trata tanto sobre S. cerevisiae como sobre otras especies de levaduras. En el caso de levaduras no-Saccharomyces he tratado de comprender su fisiología en mosto, en condiciones aeróbicas, incluyendo los factores que afectan al rendimiento en alcohol y acetato, y el impacto de estas condiciones sobre el transcriptoma. Para S. cerevisiae he utilizado una combinación de biología computacional e ingeniería genética para identificar los factores genéticos que influyen en la producción de acetato en cultivos aireados. Los resultados de la tesis indican que hay factores ambientales, fácilmente controlables en enología, que pueden tener un gran impacto sobre los rendimientos de alcohol y ácido acético para todas las especies de levaduras analizadas. Además, he podido identificar varios genes cuya deleción permite reducir el problema del ácido acético en cultivos aireados de S. cerevisiae. Mis resultados pueden servir de guía para el desarrollo de procesos fermentativos con levaduras no-Saccharomyces que permitan reducir el contenido alcohólico del vino. Por otro lado, esta información está sirviendo para el desarrollo de cepas no recombinantes de S. cerevisiae mejoradas respecto al problema del exceso de acético en aerobiosis que se podrían utilizar solas o en combinación con otras especies de levaduras para reducir el grado alcohólico.Universidad de La Rioja (España)González García, Ramón (null)Morales Calvo, Pilar (null)2019text (thesis)application/pdfhttps://dialnet.unirioja.es/servlet/oaites?codigo=221181engLICENCIA DE USO: Los documentos a texto completo incluidos en Dialnet son de acceso libre y propiedad de sus autores y/o editores. 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