Abstract: The relationships between total hydrogen content, dominant microbial genera and lactic acid content in bottom pit muds (BPMs) from old and young mud pits used for the production of strong-flavor Baijiu were analyzed in this study. It was found that the total hydrogen content decreased with the increase in pit depth and pH and lactic acid content in various layers of young and old BPM, this decrease being greater in old BPM. The copy numbers of dominant genera in old BPM were generally higher than those in young BPM. The correlation coefficients between lactic acid content and total copy numbers of dominant genera were significantly different between young and old BPMs (?0.665 2 vs 0.025 6), and a strong negative correlation existed in young BPM. Fifteen dominant genera showed a strong negative correlation with lactic acid content in young BPM (< ?0.5); while in old BPM, small correlation coefficients (half positive and half negative) were observed between most dominant genera and lactic acid content and only two dominant genera (Caproiciproducens and Hydrogenispora) showed strong correlation with lactic acid content. It was indicated that the metabolic profile of dominant genera was different between young and old BPMs. The dominant genera in young BPM were mainly involved in the degradation of lactic acid. In conclusion, the reduction of lactic acid content in BPM was related to microbial total hydrogen metabolism, which was beneficial to increase the pH of BPM thereby improving its quality.

Key words: Chinese strong-flavor Baijiu; layered bottom pit mud; total hydrogen; lactic acid; dominant genera