Bacterial Communities Found in Pit-Wall Mud and Factors Driving Their Evolution

Area of Science:

• Microbiology
• Environmental Science
• Food Science

Background:

• Pit-wall mud (PWM) is crucial for Baijiu fermentation, harboring unique bacterial communities.
• The composition of PWM bacterial communities varies with pit age and height, influencing fermentation outcomes.
• Understanding PWM bacterial evolution is key to optimizing Baijiu production.

Purpose of the Study:

• To investigate the bacterial communities within PWM and identify factors governing their evolution.
• To correlate physicochemical properties of PWM with bacterial community structure and diversity.
• To elucidate the mechanisms behind PWM maturation and its impact on Baijiu fermentation.

Main Methods:

• Bacterial 16S rRNA gene sequencing was used to analyze community composition in new PWM (NPWM) and old PWM (OPWM).
• Physicochemical properties of PWM, including pH, were measured and correlated with microbial data.
• Statistical analyses, including R-squared and path coefficient calculations, were employed to determine the influence of environmental factors on bacterial communities.

Main Results:

• Bacterial abundance and diversity were lower in NPWM compared to OPWM.
• Dominant genera shifted from *Lactobacillus* in NPWM to *Caproiciproducens*, *Aminobacterium*, *Hydrogenispora*, *Lactobacillus*, *Petrimonas*, *Syntrophomonas*, and *Sedimentibacter* in OPWM.
• pH was the primary driver of bacterial community evolution, explaining 96.5% of the variation and significantly impacting diversity and abundance.

Conclusions:

• Bacterial communities in PWM undergo significant evolution, particularly influenced by pH.
• *Caproiciproducens* and *Clostridium sensu stricto 12* contribute to PWM maturation by metabolizing lactic acid, thereby inhibiting *Lactobacillus* growth.
• This study enhances the understanding of bacterial community dynamics and maturation processes in pit-wall mud for improved Baijiu fermentation.