Bioaugmentation with Zymomonas mobilis modulates microbial succession and enhances volatile profiles in strong-flavor Daqu fermentation

The advancement of novel microbial resources is pivotal for improving traditional Daqu fermentation in Chinese strong-flavor Baijiu. Although Zymomonas mobilis (Z. mobilis) exhibits potential in other alcoholic beverages, its application in Baijiu remains unexplored. This study demonstrates that Z. mobilis fortification significantly enhances Daqu quality by restructuring microbial communities and modulating enzymatic activity. Key findings include: (1) A dominance shift from Bacillus to Kroppenstedtia (53.4 % abundance), enhancing starch liquefaction and Maillard reaction-driven aroma formation; (2) Increased esterification power (+16.7 %, P < 0.05), fermentation power (+34.8 %, P < 0.01), and total volatile compounds (+28.7 %, P < 0.01), including critical esters (e.g., methyl tetradecanoate +64.9 %); (3) PICRUSt2 analysis revealed upregulated enzymes (e.g., ethyl acetate synthase, EC 2.3.1.84, +42 %) promoting ethanol and ester synthesis. Co-occurrence networks further indicated simplified microbial interactions but enriched functional genera. These results establish Z. mobilis as a dual-action modulator, improving Daqu through microbial restructuring and enzymatic activation. This study provides the first evidence for Z. mobilis application in Baijiu, offering a novel strategy for optimizing traditional fermentation processes.