Abstract: A reaction system for converting lactic acid to caproic acid in a self-designed bioreactor was constructed, in this system, microbe in the pit mud of strong aroma Baijiu (Chinese liquor) was selected as the starting bacteria, and yellow water with high lactate acid concentration was used as the carrier. The optimum culture conditions were 40.0 g/L of lactic acid, at 37°C and pH 5.5-6.0, in these conditions, the function of caproic acid-producing and lactic acid-utilizing was strengthened when the bioreactor was filled with activated carbon and modified polyurethane sponge. Results showed that the species diversities in the fermentation broth of the bioreactors were lower than those in pit muds, which was accompanied by the obvious changes in composition of dominant microbe. The dominant prokaryotes in the fermentation broth of the reactors were the Firmicute Clostridium related to caproic acid production and lactic acid reduction. And the Aminobacterium genus involved in the degradation of amino acids increased significantly. The ethyl caproate content in the original liquor were higher than that in conventional liquor fermentation when enhanced yellow water was added in different stages of Baijiu fermentation. When enhanced yellow water was added at the beginning of fermentation, the ethyl caproate content was 561.9 mg/L, which was 330.9% higher than that of the control group. After 7 days of fermentation, the ethyl caproate content increased by 154.6% and the ethyl lactate content decreased by 9.8%. In this study, domestication of pit mud bacteria and applying them to Baijiu fermentation were confirmed useful to increase ethyl caproate content while decreasing ethyl lactate content in production of strong aroma Baijiu, which is of positive significance to improve liquor flavor and quality.
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2020, Vol. 46 
