Spatiotemporal heterogeneity drives acetic acid fermentation of traditional Chinese aromatic vinegar: Insights into microbiota dynamics and flavor formation.

To address the ecological implications of spatiotemporal heterogeneity on microbial assembly and flavor formation in Chinese aromatic vinegar, this study systematically revealed these dynamics during the solid-state acetic acid fermentation (AAF). Temporally, Lactobacillus, Acetobacter, and Komagataeibacter synergistically drove acid and aroma formation. In the early stage (day 1), Lactobacillus dominated, creating an acidic niche for Acetobacter. During the main fermentation stage (days 7 to 13), Acetobacter oxidized ethanol to acetic acid, while Lactobacillus accumulated lactic acid, facilitating ester production. In the late stage (day 21), increased Komagataeibacter abundance further enhanced the accumulation of acetic acid and ketones. Spatially, oxygen availability created distinct metabolic zones: the aerobic upper layer favored rapid acetic acid accumulation by the proliferation of Acetobacter and Komagataeibacter. The middle layer served as a metabolic transition zone. The anaerobic lower layer dominated by Lactobacillus accumulated lactic acid, alcohols, and esters. Bacterial community assembly shifted from stochastic to deterministic processes, with high-abundance Acetobacter and Lactobacillus (over 90%) reinforcing metabolic synergy through environmental filtering. The layer-by-layer turning process gradually reduced spatial heterogeneity, converting compartmentalized metabolism into integrated synergy, thereby ensuring balanced accumulation of aromatic compounds and maintaining acid production efficiency.