Application of Pichia kudriavzevii in solid-state fermentation of Zhenjiang aromatic vinegar: Microbial community structure and volatile flavor changes.

Non-Saccharomyces yeasts play a significant role in enhancing the aroma profiles of fermented foods. However, their specific contributions to vinegar production remain poorly characterized. This study simulated the solid-state fermentation process of Zhenjiang aromatic vinegar (ZAV) to investigate whether artificial addition of non-Saccharomyces yeasts could improve flavor compounds in vinegar and explore the underlying mechanisms. Three non-Saccharomyces yeast strains were isolated from ZAV vinegar Pei. The results showed that Pichia kudriavzevii YK116 exhibited superior tolerance to ethanol, acetic acid, and high temperature stresses prevalent in acetic acid fermentation (AAF). High-throughput sequencing revealed that the addition of P. kudriavzevii YK116 primarily modulated the fungal community structure while maintaining bacterial community stability. Headspace Solid-Phase Microextraction Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS) analysis showed that, compared to the control group, the experimental group inoculated with P. kudriavzevii YK116 exhibited significantly enhanced production of flavor compounds, particularly ethyl acetate, phenylethyl acetate, and isoamyl acetate. By the end of fermentation, the contents of these compounds increased by 23.17 %, 74.06 %, and 9.62 %, respectively. Correlation analysis indicated stronger associations of fungi, especially Pichia and Hannaella, with ester formation than bacterial communities, while Acetobacter showed the highest correlation with acid production. Overall, inoculation with P. kudriavzevii YK116 modulates flavor compounds primarily through altering fungal community structure during vinegar fermentation. This study provides the first elucidation of the mechanism by which non-Saccharomyces yeasts enhance flavor compounds (particularly esters) through modulating microbial community structure during solid-state vinegar fermentation.