Mechanisms of acid generation and reduction during Jiangxiangxing Baijiu fermentation: insights from practices of raw materials saccharification regulation

Acetic acid is the main contributor to total acidity in base liquor. • The acetate kinase pathway dominates acetic acid production by lactic acid bacteria. • Core acetic acid-producing microbes decline with enhanced saccharification. • Acetate kinase transcription decreases with enhanced saccharification. Elevated total acidity in the first round base liquor is a major challenge in Jiangxiangxing Baijiu production. Production practice has shown that enhanced raw material saccharification effectively reduces total acidity. This study investigated the underlying regulatory mechanism. Enhanced saccharification reduced total acidity, predominantly attributable to acetic acid, to 0.059 mol/L, representing a 14.47% reduction, without altering overall microbial succession. Multi-omics and culture-dependent analyses identified Limosilactobacillus panis , Lactobacillus acetotolerans , and Limosilactobacillus avium as core acetic acid-producing microorganisms, with their relative abundances reduced by 48.43%, 43.01%, and 32.67%, respectively. The acetate kinase-mediated pathway was the dominant route of acetic acid biosynthesis, and enhanced saccharification reduced transcription of the acetate kinase-encoding gene. Fermentation validation showed that elevated reducing sugar promoted yeast growth and ethanol production, thereby suppressing acetic acid formation. Overall, enhanced saccharification reduces total acidity in base liquor by modulating reducing sugar-driven microbial dynamics and suppressing acetic acid biosynthesis. Download: Download high-res image (219KB) Download: Download full-size image