Geosmin is a volatile metabolite of Streptomyces spp., which causes earthy off-flavor at trace level content (the threshold is at ng/L level), seriously and extensively deteriorating the flavor and quality of Chinese Baijiu. The water content in Daqu (Chinese Baijiu fermentation starter)-making process decreased with time. When the water content was about 10% in the late stage, about 6 μg/kg of geosmin could be detected, which seriously affected the quality of Daqu. Screening of functional microorganisms from Daqu that inhibit the production of geosmin under low water content conditions for biocontrol is a necessary mean to improve the quality of Daqu. In this study, the microbial community structure and the geosmin content in Daqu were analyzed, and obtained the in situ functional microorganisms of Daqu according to the inhibition of Streptomyces. The results showed that in the late stage of Daqu-making, the water content decreased to 10%-20%, and the geosmin content was still increasing, reaching the highest content of (9.75±0.50) μg/kg. The main fungi in Daqu were Pichia, Thermoascus. Based on Spearman’s correlation analysis, it was found that Aspergillus sp. LBM32010, Aspergillus sp. LBM32013, Rhizopus sp. LBM32021, Trichosporon sp. LBM32022, Lichtheimia sp. LBM32026 and Trichosporon sp. LBM32030 have good inhibitory effects on Streptomyces and geosmin, among which Aspergillus sp. LBM32010 had the best inhibitory effect on geosmin, and geosmin content decreased from (34.79±2.34) μg/kg to (3.11±1.22) μg/kg, and the inhibition rate was 91.06% (P<0.001). This study highlights the biocontrol feasibility potential of the chemicals at trace level by precise regulation of microbial communities, and shows the possibility of achieving precise regulation of microbial communities.
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