Abstract
The higher alcohols produced by Saccharomyces cerevisiae exert remarkable influence on the taste and flavour of Chinese Baijiu. In order to study the regulation mechanism of amino acid metabolism genes on higher alcohol production, eight recombinant strains with amino acid metabolism gene deletion were constructed. The growth, fermentation performance, higher alcohol production, and expression level of genes in recombinant and original α5 strains were determined. Results displayed that the total higher alcohol concentration in α5ΔGDH1 strain decreased by 27.31% to 348.68 mg/L compared with that of α5. The total content of higher alcohols in α5ΔCAN1 and α5ΔGAT1 strains increased by 211.44% and 28.36% to 1493.96 and 615.73 mg/L, respectively, compared with that of α5. This study is the first to report that the CAN1 and GAT1 genes have great influence on the generation of higher alcohols. The results demonstrated that amino acid metabolism plays a substantial role in the metabolism of higher alcohols by S. cerevisiae. Interestingly, we also found that gene knockout downregulated the expression levels of the knocked out gene and other genes in the recombinant strain and thus affected the formation of higher alcohols by S. cerevisiae. This study provides worthy insights for comprehending the metabolic mechanism of higher alcohols in S. cerevisiae for Baijiu fermentation.
Highlights
Higher alcohol is one of the important flavour substances in Baijiu [1] that are involved in the formation of Baijiu taste and flavour [2]
We consider that the reason for the difference in the alcohol consumption of the recombinant strains is the deletion of the gene related to amino acid transportation, which led to the diversity in the utilisation of amino acids by yeast and reflected in the discrepancy of alcohol yield
We concentrated on the effect of the inactivation of genes related to amino acid metabolism on the growth, fermentation performance, and higher alcohol formation of S. cerevisiae
Summary
Higher alcohol is one of the important flavour substances in Baijiu [1] that are involved in the formation of Baijiu taste and flavour [2]. Each flavour type of Baijiu has its unique style because of its unique content of higher alcohols and other flavour substances. The appropriate content of higher alcohols brings unique aroma and mellow taste to Chinese Baijiu [4]. Higher alcohols are generated by yeast during the fermentation of alcohol [7]. The metabolic pathway for Saccharomyces cerevisiae to generate higher alcohols is divided into the catabolic pathway (Ehrlich pathway) and biosynthetic pathway according to the different sources of α-ketoacids [9, 10]
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