Expanded metabolic diversity of Propionibacterium freudenreichii potentiates novel applications in food biotechnology

Propionibacterium freudenreichii is used as a cheese-ripening adjunct culture and also receives interest as de novo producer of vitamin B₁₂ (B₁₂) and for its probiotic potential. Recent advances suggest P. freudenreichii is adapted for growth in intestinal tracts enabled by the capacity to metabolize important gut cross-feeding metabolites such as lactate and 1,2-propanediol (1,2-PD), further supporting its potential as probiotic. Notably, P. freudenreichii was recently shown to capture and utilize low amounts of oxygen such as encountered in the gut. This enabled complete oxidation of lactate, further stimulating P. freudenreichii growth, resulting in increased biomass and B₁₂ production. In addition, bacterial microcompartment (BMC)-dependent utilization of 1,2-PD in anaerobic conditions, has implications for potential mutualistic interactions between P. freudenreichii and mucus-degrading bacteria such as bifidobacteria. The capacity to metabolize short-chain fatty acids and 1,2-PD may further support innovative applications of P. freudenreichii such as in situ B₁₂ enrichment of fermented foods.