Metabolic Engineering of the purine metabolic pathway in brewers yeast to reduce the Purine components in a Beer System

Beer is one of the most popular beverages in the world. However, beer contains excessive amounts of purines, which can increase the risk of hyperuricaemia and gout. During beer fermentation, a key reason is that the purines are not completely absorbed by yeast, which is due to the insufficient ability of purine salvage pathway in beer yeast. In order to improve the absorption capacity of yeast for purines, this study overexpressed four key genes in the purine metabolism pathway (HPT1, APT1, FCY2, and PRM15) in the commercial beer yeast strain SC4, and obtained three yeast engineering strains, namely M1 (SC4 HPT1:: APT1), M2 (M1:: FCY2), and M3 (M2:: PRM15). The expression of purine metabolism-related genes was examined at the transcriptional level, and the expression levels of HPT1, APT1, FCY2 and PRM15 genes were increased by 3.50-fold, 2.37-fold, 2.07-fold and 4.37-fold, respectively, and the overexpression of FCY2 and PRM15 increased the expression levels of HPT1 and APT1 by 3.50-fold and 2.37-fold, respectively. The expression of FCY2 and PRM15 made HPT1 and APT1 more active, indicating that the ability to absorb purines was further enhanced. Applying engineering yeast M3 to 12-degree wort fermentation, the results shown that the free purine base content is reduced by 53.35%, which provides a theoretical basis for reducing the purine content in beer.