Evolving the core microbial community in pit mud based on bioturbation of fortified Daqu.

Directional stress is an effective measure to evolve community structure and improve bioactivity of pit mud (PM). In this study, adding fortified Daqu in artificial PM (APM) was to disturb the microbial community and affect the metabolites furthermore. To evaluate the effect of fortified Daqu on culturing APM, microbial communities of APMs with/without adding fortified Daqu were investigated by fluorescence in situ hybridization and Illumina Miseq. These results indicated that microbes (Clostridium sp., Clostridium kluyveri, hydrogenotrophic methanogens, and acetotrophic methanogens) related to the production of key aroma compounds increased notably when fortified Daqu was added. Especially the hydrogenotrophic and acetotrophic methanogens increased by 5.19- and 4.63-fold after 30-days' culture. Then metabolites (organic acids, volatile compounds) were also analyzed by HPLC and HS-SPME-GC-MS. Results showed that the content of butyric acid and hexanoic acid was significantly higher when adding fortified Daqu. What's more, the proportion of esters and phenols were higher compared with the APM without adding fortified Daqu as well. The microbial compositions of APMs with/without adding fortified Daqu were observed in this study, which indicated the microbial community evolving in functional community in favor of liquor-brewing and suggested a novelty process was developed by disturbing the community diversity.