Microaerobic metabolism of lactate and propionate enhances vitamin B production in Propionibacterium freudenreichii.

Background: Propionibacterium freudenreichii is used in biotechnological applications to produce vitamin B. Although cultured mainly in anaerobic conditions, microaerobic conditions can greatly enhance biomass formation in P. freudenreichii. Since B yields may be coupled to biomass formation, microaerobic conditions show great potential for increasing B yields in P. freudenreichii.

Results: Here we show biomass formation increases 2.7 times for P. freudenreichii grown in microaerobic conditions on lactate versus anaerobic conditions (1.87 g/L vs 0.70 g/L). Consumption of lactate in microaerobic conditions resulted first in production of pyruvate, propionate and acetate. When lactate was depleted, pyruvate and propionate were oxidised with a concomitant sixfold increase in the B titer compared to anaerobic conditions, showing potential for propionate and pyruvate as carbon sources for B production. Consequently, a fed-batch reactor with anaerobically precultured lactate-grown cells was fed propionate in microaerobic conditions resulting in biomass increase and production of B. Vitamin yields increased from 0.3 [Formula: see text] B per mmol lactate in anaerobic conditions to 2.4 [Formula: see text] B per mmol lactate and 8.4 [Formula: see text] B per mmol propionate in microaerobic conditions. Yield per cell dry weight (CDW) increased from 41 [Formula: see text] per g CDW in anaerobic conditions on lactate to 92 [Formula: see text] per g CDW on lactate and 184 [Formula: see text] per g CDW on propionate in microaerobic conditions.

Conclusions: Here we have shown both B yield per substrate and per CDW were highest on cells oxidising propionate in microaerobic conditions, showing the potential of propionate for biotechnological production of vitamin B by P. freudenreichii.