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

Distinct carbon sources induce different metabolic states in Propionibacterium freudenreichii, with lactate supporting high vitamin B12 yields and hexoses causing redox constraints.

• Why it matters: Understanding how carbon sources influence microbial metabolism is crucial for optimizing bioproduction processes, especially for valuable compounds like vitamin B12, but the system-level effects remain poorly understood.
• What they did: The study used label-free quantitative proteomics, physiological, and metabolite analyses to compare metabolic reprogramming in PFR strain DSM 20271 T grown on lactate versus hexoses, revealing distinct redox and biosynthetic strategies.
• The result: Lactate promotes a balanced state with high vitamin B12 production (~100 µg g -1 wet biomass), while hexoses induce redox constraints involving aspartate metabolism and reduced biosynthetic efficiency, highlighting carbon source as a key regulator of metabolic configuration.