Decoding butyrate fermentation with glucose as a model substrate: Parameter optimization and metagenomic insights.

Area of Science:

• Biotechnology
• Microbiology
• Biochemical Engineering

Background:

• Selective butyrate production via anaerobic fermentation is crucial for sustainable biochemicals.
• Mechanisms and optimal conditions for butyrate accumulation in anaerobic systems are not well-understood.
• Previous reports on optimal conditions for butyrate production are inconsistent.

Purpose of the Study:

• To investigate the effects of pH, temperature, and inoculum-to-substrate ratio (ISR) on selective butyrate production.
• To identify optimal conditions for maximizing butyrate yield in glucose fermentation.
• To elucidate the microbial and genetic mechanisms underlying butyrate biosynthesis.

Main Methods:

• Batch fermentation experiments using glucose as a substrate.
• Systematic variation of pH (4.5-7.0, 8.5-11.0), temperature (37°C, 55°C), and ISR (3:1 to 1:3).
• Metagenomic and functional gene analyses to assess microbial community and metabolic pathways.

Main Results:

• Optimal butyrate production was achieved at pH 5.5, 37°C, and an ISR of 1:3.
• Temperature and ISR significantly impacted microbial community structure.
• Key butyrate-producing genera identified include Clostridium, Caproicibacter, Caproicibacterium, Sporolactobacillus, and Ethanoligenens.
• Enrichment of reverse β-oxidation genes was observed under optimal conditions, indicating enhanced carbon chain elongation.

Conclusions:

• The study refines previously inconsistent reports by establishing optimal conditions for selective butyrate production.
• Metagenomic and functional analyses provide mechanistic insights into butyrate biosynthesis pathways.
• Findings offer practical strategies for enhancing butyrate yield in industrial anaerobic fermentation processes.