Regulating the ratio of higher alcohols to esters by simultaneously overexpressing ATF1 and deleting BAT2 in brewer's yeast Saccharomyces pastorianus

Abstract

The quality and aroma of beer are affected by the content of higher alcohols and esters. An appropriate ratio of higher alcohols to esters is essential to the beer quality. The imbalanced ratio can lead to a poor taste of beer. In beer, the production of higher alcohols and esters is closely related to the brewer's yeast metabolism. In Saccharomyces pastorianus, the alcohol acetyltransferase encoding gene (ATF1) is the key gene for producing esters. In this work, the ATF1 gene was overexpressed by different strength promoters (PGK1p(9), PGK1p(12), PGK1p(16), PGK1p(20)) and was constructed recombinant strains S9-M9, S9-M12, S9-M16, S9-M20 by a seamless gene deletion method, respectively. The ethyl acetate content produced by strain S9-M9, S9-M12, S9-M16, S9-M20 was 2.49-, 8.63-, 15.91-, 24.17-fold higher than parental strain S9, respectively. The results illustrated that strain S9-M9 had a favorable ratio of higher alcohols to esters (3.2: 1). The fermentation scale was subsequently expanded to 100-L, while the fermentation performance of strains S9 and S9-M9 remained the same. In this study, the ATF1 gene expression of S. pastorianus by different strength promoters provided an accurate regulation of higher alcohols-esters production ratio in beer. This is the first description of regulating the ratio of higher alcohols to esters using this new strategy, combining different strength promoters and a seamless gene deletion method. This new strategy provided a new perspective for regulating the flavor profile in beer or other beverages.