During alcoholic fermentation, Saccharomyces cerevisiae synthesizes more than 400 different compounds with higher alcohols, acetate esters of higher alcohols and ethyl esters of medium-chain fatty acids being the most important products of its metabolism, determining the particular flavour profile of each wine. The concentration of the metabolites produced depends to a large extent on the strain used. The use of indigenous strains as starting cultures can lead to the production of wines with excellent organoleptic characteristics and distinct local character, superior in quality when compared to their commercial counterparts. However, the relationship of these wild-type genotypes, linked to specific terroirs, with the biosynthetic profiles of flavour metabolites is not completely clarified and understood. To this end, qRT-PCR was employed to examine, for the first time on the transcriptional level, the performance of an indigenous Saccharomyces cerevisiae strain (Z622) in its natural environment (Debina grape must). The expression of genes implicated in higher alcohols and esters formation was correlated with the concentrations of these compounds in the produced wine. Furthermore, by applying the same fermentation conditions, we examined the same parameters in a commercial strain (VL1) and compared its performance with the one of strain Z622. Strain Z622, exhibited lower concentrations of 2-methylbutanol, 3-methylbutanol and 2-phenyl ethanol, than VL1 correlating with the elevated expression levels of transaminase and decarboxylase genes. Furthermore, the significantly high induction of ADH3 throughout fermentation of Z622 probably explains the larger population numbers reached by Z622 and reflects the better adaptation of the strain to its natural environment. Regarding acetate ester biosynthesis, Z622 produced higher concentrations of total acetate esters, compared with VL1, a fact that is in full agreement with the elevated expression levels of both ATF1 and ATF2 in strain Z622. This study provides evidence on the transcriptional level that indigenous yeast Z622 is better adapted to its natural environment able to produce wines with desirable characteristics, i.e. lower concentrations of higher alcohol and higher ester, verifying its potential as a valuable starter for the local wine-industry.

中文翻译：

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在自然的自然环境中发酵的天然酿酒酵母菌株的风味生物合成基因的对比转录分析与商业菌株的比较以及该基因活性与产生的风味化合物的相关性

在酒精发酵过程中，酿酒酵母合成了400多种不同的化合物，其中高级醇，高级醇的乙酸酯和中链脂肪酸的乙酯是其代谢的最重要产物，这决定了每种葡萄酒的独特风味。产生的代谢产物的浓度在很大程度上取决于所使用的菌株。使用本地菌株作为起始文化可以生产出具有极佳的感官特性和鲜明的当地特色的葡萄酒，与同类商品相比，其质量更高。但是，这些与特定风土相关的野生型基因型与风味代谢物的生物合成特征之间的关系尚未完全阐明和理解。为此，qRT-PCR首次在转录水平上检测了天然酿酒酵母菌株（Z622）在其自然环境（Debina葡萄汁）中的性能。涉及高级醇和酯形成的基因的表达与所生产葡萄酒中这些化合物的浓度相关。此外，通过应用相同的发酵条件，我们在商业菌株（VL1）中检查了相同的参数，并将其性能与菌株Z622进行了比较。与VL1相比，菌株Z622的2-甲基丁醇，3-甲基丁醇和2-苯基乙醇的浓度较低，这与转氨酶和脱羧酶基因的表达水平升高有关。此外，在Z622的整个发酵过程中，ADH3的诱导率很高，这可能说明Z622达到了更大的种群数量，并反映了该菌株对其自然环境的更好适应性。关于乙酸酯的生物合成，与VL1相比，Z622产生了更高浓度的总乙酸酯，这一事实与Z622菌株中ATF1和ATF2的表达水平升高完全吻合。这项研究在转录水平上提供了证据，表明本地酵母Z622更适合其自然环境，能够生产具有所需特性的葡萄酒，即较低浓度的高级酒精和较高的酯，从而证明了其作为当地酿酒行业有价值的起子的潜力。