Instituto de Ciencias de la Vid y del Vino (Consejo Superior de Investigaciones Científicas, Universidad de la Rioja, Gobierno de La Rioja), Logroño, Spain.
PLoS One. 2013 Aug 13;8(8):e71909. doi: 10.1371/journal.pone.0071909. eCollection 2013.
As a consequence of the increase in global average temperature, grapes with the adequate phenolic and aromatic maturity tend to be overripe by the time of harvest, resulting in increased sugar concentrations and imbalanced C/N ratios in fermenting musts. This fact sets obvious additional hurdles in the challenge of obtaining wines with reduced alcohols levels, a new trend in consumer demands. It would therefore be interesting to understand Saccharomyces cerevisiae physiology during the fermentation of must with these altered characteristics. The present study aims to determine the distribution of metabolic fluxes during the yeast exponential growth phase, when both carbon and nitrogen sources are in excess, using continuous cultures. Two different sugar concentrations were studied under two different winemaking temperature conditions. Although consumption and production rates for key metabolites were severely affected by the different experimental conditions studied, the general distribution of fluxes in central carbon metabolism was basically conserved in all cases. It was also observed that temperature and sugar concentration exerted a higher effect on the pentose phosphate pathway and glycerol formation than on glycolysis and ethanol production. Additionally, nitrogen uptake, both quantitatively and qualitatively, was strongly influenced by environmental conditions. This work provides the most complete stoichiometric model used for Metabolic Flux Analysis of S. cerevisiae in wine fermentations employed so far, including the synthesis and release of relevant aroma compounds and could be used in the design of optimal nitrogen supplementation of wine fermentations.
由于全球平均气温的升高，葡萄在收获时往往已经达到足够的酚类和芳香成熟度，但已经过度成熟，导致发酵葡萄汁中的糖分浓度增加，C/N 比例失衡。这一事实给降低葡萄酒中酒精含量的挑战带来了明显的额外障碍，这是消费者需求的一个新趋势。因此，了解在这些改变了的特性的葡萄汁发酵过程中，酿酒酵母的生理特性是很有趣的。本研究旨在使用连续培养来确定酵母指数生长阶段的代谢通量分布，此时碳源和氮源都过剩。在两种不同的酿酒温度条件下研究了两种不同的糖浓度。尽管关键代谢物的消耗和产生速率受到研究的不同实验条件的严重影响，但在所有情况下，中央碳代谢中的通量分布基本保持不变。还观察到，温度和糖浓度对戊糖磷酸途径和甘油形成的影响比对糖酵解和乙醇生产的影响更大。此外，氮的吸收，无论是在数量上还是在质量上，都受到环境条件的强烈影响。这项工作提供了迄今为止用于葡萄酒发酵中酿酒酵母代谢通量分析的最完整的计量模型，包括相关香气化合物的合成和释放，可用于设计葡萄酒发酵中最佳的氮补充。
