Heap fermentation modes of sauce-flavored Baijiu: Microbial metabolic differences and optimization strategies for mechanized fermentation

The mechanized production of Baijiu is a significant trend, yet the shift from traditional brewing to controlled and efficient modern fermentation methods has not been fully accomplished. This study aimed to identify the disparities in the microbial structure and metabolism of fermented grains among different heap fermentation modes and enhance mechanized box heap fermentation through the inoculation of microorganisms. Metagenomics was used to ascertain the differences between microbial communities and metabolic functions. In mechanized box heap fermentation, the dominant microorganisms included Saccharomyces cerevisiae (43.61 %), Nakaseomyces glabrata (25.89 %), Kroppenstedtia eburnean (9.22 %). In traditional manual heap fermentation, the dominant microorganisms included Bacillus amyloliquefaciens (14.8 %), Bacillus licheniformis (14.02 %), and Bacillus sonorensis (9.77 %). The dominant functional genes in box heap fermentation were K13953 (for alcohol dehydrogenase; ADH) and K00844 (for hexokinase; glk), while those in traditional manual heap fermentation were K00016 (for lactate dehydrogenase; LDH) and K00158 (for pyruvate oxidase; pox). Owing to their differential functions in box-fermented grains, inoculating brewing microorganisms can augment the saccharification reaction rate and content of flavor substances. This research offers support to effectively ameliorate the box heap fermentation and augment the heap fermentation efficiency of sauce-flavored liquor.