Assembly of a lignocellulose-degrading synthetic community from the strong-flavor Daqu by a stepwise method

The lignocellulose in Daqu plays an important role during the Baijiu fermentation, such as providing energy for microbial metabolism and precursors for flavor compounds. However, due to the complexity of the Daqu microbial community and the fermentation environment, the regulation of lignocellulose degradation efficiency is limited. In such cases, artificial intervention can be achieved through the application of synthetic communities. Here, we studied the structure of the lignocellulose-degrading microbial communities in Daqu. Based on the characteristics of lignocellulose composition, we developed three high-throughput screening methods and used a stepwise assembly approach to construct a synthetic community composed of Bacillus stercori, Bacillus paramycoides, Klebsiella pneumoniae, and Cyberlindnera fabianii. After fermentation, 54.71 % of the bran was degraded and 11 substances were uniquely produced. 4-vinylguaiacol and 2-ethyl-3,5(6)-dimethylpyrazine were considered to be the key aroma compounds of the synthetic community. This synthetic community offers a new approach to control Daqu fermentation.