Metagenomics unveils the roles of microbes in the metabolic network of purine formation during Huangjiu fermentation

Purine is a major factor contributing to the development of hyperuricemia and gout, and it is found in large quantities in Huangjiu as free bases. Purine production in Huangjiu is strongly associated with microbial metabolism. However, to the best of our knowledge the microorganisms responsible for and the mechanisms of purine formation during Huangjiu fermentation are yet to be evaluated. Herein, changes in purine levels during Huangjiu fermentation were analyzed. Further, the microbes responsible for purine production were identified and their gene abundance was studied. Results revealed that adenine, guanine, hypoxanthine, and xanthine are produced during Huangjiu fermentation. The total purines content on day 0 (27.99 mg/L) was found to be considerably lower than that produced on day 24 (122.15 mg/L) during Huangjiu fermentation. Metagenomics showed that the composition of the microbial community fluctuates sharply during five fermentation periods of Huangjiu, with the microbial community richness and diversity being the most prominent on day 3. At the genus level, Klebsiella, Lactobacillus, Staphylococcus, Saccharopolyspora, and Saccharomyces were abundant during Huangjiu fermentation and were involved in purine metabolism. Relationships between the dominant microorganisms and key enzyme genes of the purine pathways were also established based on the Kyoto Encyclopedia of Genes and Genomes database. Correlation analysis showed that Lactobacillus and Saccharomyces were the main genera involved in purine formation. Saccharomyces cerevisiae, Lactobacillus paralimentarius, and Lactiplantibacillus plantarum were involved in purine formation during Huangjiu fermentation. Overall, this study improves our understanding of the purine formation mechanism during Huangjiu fermentation and provides valuable insights into the regulation of purine formation by microorganisms.