Carbon source-dependent metabolic states govern redox homeostasis and cofactor biosynthesis in Propionibacterium freudenreichii.

Carbon source determines distinct metabolic states in Propionibacterium freudenreichii, with lactate promoting vitamin B12 synthesis and hexoses inducing redox-constrained pathways.

• Why it matters: Understanding how environmental factors influence microbial metabolism is crucial for optimizing bioproduction processes, especially for valuable compounds like vitamin B12. The role of carbon source in shaping these metabolic states remains poorly understood, limiting targeted improvements.
• What they did: Using label-free quantitative proteomics combined with physiological and metabolite analyses, the study examined how different carbon sources—lactate versus hexoses—reprogram P. freudenreichii’s metabolism, revealing distinct redox and biosynthetic strategies.
• The result: Findings show lactate supports a balanced state with high vitamin B12 yields (~100 μg g−1 wet biomass), while hexoses induce redox constraints via aspartate metabolism, offering insights for enhancing microbial production systems.