The Metabolic Reprogramming Mechanism by Pueraria Lobata Fermentation Enhances Saccharomyces cerevisiae Reducing-Sugar-Releasing Activity and Polypeptide Synthesis.

Pueraria lobata is a widely distributed traditional Chinese medicinal herb, and its active constituents have potential value in food, pharmaceutical, cosmetic, and industrial fermentation applications. In this study, P. lobata was used as the substrate and Saccharomyces cerevisiae as the fermenting organism. Response surface methodology was employed to optimize fermentation conditions using peptide concentration in the broth as the target response. The effects of P. lobata on S. cerevisiae were evaluated by measuring yeast colony counts, protease activity, and sodium alginate-based reducing-sugar-releasing activity. Transcriptomic profiling combined with GO/KEGG enrichment analyses and qRT-PCR validation was further used to analyze gene expression differences in S. cerevisiae at 5, 24, and 48 h. The optimal fermentation conditions were 71 h, 22.41 °C, and a solid-to-liquid ratio of 1:20, under which the peptide concentration reached 32.37 mg/mL. Relative to conventional yeast medium, protease activity and reducing-sugar-releasing activity in the P. lobata fermentation broth increased by 2.37-fold and 10.1-fold, respectively. Supplementation with 10% P. lobata most effectively promoted S. cerevisiae proliferation, resulting in the highest colony count of 6.8 × 104 CFU/mL. Transcriptomic analysis showed that the number of differentially expressed genes increased over time and was enriched in pathways including carbohydrate and ethanol metabolism. Time-series analysis indicated a dynamic metabolic shift in S. cerevisiae, including early activation of glycolysis and energy production (5 h), transition toward ethanol metabolism in the mid phase (24 h), and later emphasis on cell growth and maintenance (48 h). Upregulation of ADH2, PCK1, CDA1, and CDA2, together with downregulation of HXK1, aligned with the observed metabolic reprogramming and enhanced enzyme-activity phenotypes. These findings support the use of P. lobata as a promising plant substrate for value-added yeast fermentation.