Microbiomes associated with fermentations of different styles of Baijiu (Chinese liquor)

Baijiu, or Chinese liquor, is a popular traditional distilled spirit in China and represents one of the oldest alcoholic beverages in the world. Baijiu is made from cereals, mainly sorghum, by a complicated spontaneous fermentation technique characterized by a simultaneous saccharification and fermentation process under solid state. The starter, called Daqu, is also prepared by spontaneous solid-state fermentation of raw cereals for the enrichment of diversified microbes including filamentous fungi, yeasts and bacteria and their enzymes responsible for saccharification and fermentation of sorghum. Baijiu is usually classified as light-, strong- and sauce-aroma styles and other miscellaneous styles, which usually use different types of Daqu prepared from different cereals fermented at different temperatures. Baijiu is traditionally produced through artificially and empirically controlled processes and now is facing the challenges of modernization and standardization for food quality, safety and sustainability, along with the economic development of China. Recently we studied fermentation microbiomes of different types of Daqu and Baijiu. We investigated the composition, dynamics and functionality of the microbial communities in different stages of the fermentation processes using culture-dependent, meta-genomic and meta-transcriptomic methods, together with detecting the dynamics of ethanol and aroma compound production. Based on the results of our microbiome research, we designed synthetic microbial consortia for light-aroma Baijiu fermentation and successfully obtained a Baijiu product with taste and quality being comparable to commercial products. The synthetic microbial consortia consisted of pure cultures of key functional microbes in Baijiu fermentation is apparently more compatible with and amenable to standardized automatic fermentation techniques.