Study on microbial communities and higher alcohol formations in the fermentation of Chinese Xiaoqu Baijiu produced by traditional and new mechanical technologies

Microorganisms play an important role in the flavor formation of Chinese Baijiu. Mechanization is the way to develop Baijiu. Therefore, it is necessary to study the effects of mechanization on microbial community and flavor in Baijiu production. The microbial communities exhibited differences between two technologies with the fermentation, and the numbers of yeasts and bacteria in new mechanical technology were significantly higher than those in traditional technology at the peak of fermentation. Both metagenomic and metatranscriptomic analyses showed 5 core microorganisms in the fermentation, namely Saccharomyces cerevisiae, Rhizopus delemar, Pichia kudriavzevii, Lactobacillus helveticus, and Rhizopus oryzae. S. cerevisiae was generally regarded to be the most dominant yeast in Baijiu fermentation, but our metatranscriptomic data showed that P. kudriavzevii was more active than S. cerevisiae. These two analyses indicated that higher initiation abundance of S. cerevisiae and P. kudriavzevii and lower initiation abundance of R. delemar and R. oryzae were observed in traditional technology than in new technology, and that Lactobacillus displayed apparent advantages in traditional technology, whereas Lactobacillus and yeast exhibited obvious advantages in new technology at the end of fermentation. In addition to S. cerevisiae, other microorganisms including non-saccharomyces yeasts, molds, and bacteria were involved in higher alcohol formation. This work provides insight into the microbial dynamics and higher alcohol formation, as well as an efficient strategy for process improvement in Baijiu fermentation.