Salt-driven bacteria community and flavor enhancement in Liuyang Douchi: Bacillus regulated flavor volatile biosynthesis.

This study investigated the effects of salinity on the bacterial community and flavor profile of Liuyang Douchi. Increased salinity was found to elevate total acidity, while reducing amino acid nitrogen levels and total microbial counts. Furthermore, High salinity reduced the relative abundance of Bacillus (as low as 2.09%) while increasing that of Staphylococcus (up to 72.7%). Compared to low-salt (0% salinity) fermentation, high-salt (5% salinity) fermentation resulted in higher levels of phenols, esters, and acids, but lower levels of pyrazines and ketones. Among them, 10 compounds with VIP > 1 and ROAV > 1 were considered as the key differential compounds. Notably, 2,3,5,6-tetramethylpyrazine and guaiacol-both positively correlated with Bacillus-were highlighted. Two bacterial isolates with high productivity of these compounds were identified as Bacillus sonorensis and Bacillus velezensis, which were proved to increase the pyrazines and guaiacol content in Douchi through enhanced fermentation. This study provides new understanding for improving the flavor quality of Liuyang Douchi through salinity control.