Screening of caproic acid-producing microorganisms and their application in the pit mud maintenance of strong-flavor Baijiu

In this study, caproic acid-producing bacteria with high yield caproic acid were isolated and screened from the pit mud of a strong-flavor (Nongxiangxing) Baijiu distillery by enrichment culture and qualitative and quantitative analysis of caproic acid, identified by morphological observation and molecular biology techniques, and applied in pit mud maintenance to test the physicochemical indexes and volatile flavor components of pit mud before and after maintenance. The results showed that a strain DFN-1 was screened and identified as Rummeliibacillus suwonensis, which was stable for high production of caproic acid. The caproic acid yield was 8.15 g/L after three passages. The quality of the pit mud was significantly improved after maintenance pit mud by the strain DFN-1, with the moisture contents increased by 10.62%, the humus contents increased by 47.6%, the total nitrogen contents increased by 30.55%, the thermophilic Bacillus count increased by 9.98%, the ammonium nitrogen content increased by 35.94%, and the relative contents of characteristic flavor substance caproic acid and ethyl caproate were increased to 31.73% and 0.43%, respectively.