Microaerobic metabolism of lactate and propionate enhances vitamin B12 production in Propionibacterium freudenreichii

Abstract

Abstract Background Propionibacterium freudenreichii is used in biotechnological applications to produce vitamin B 12 . Although cultured mainly in anaerobic conditions, microaerobic conditions can greatly enhance biomass formation in P. freudenreichii . Since B 12 yields may be coupled to biomass formation, microaerobic conditions show great potential for increasing B 12 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 12 titer compared to anaerobic conditions, showing potential for propionate and pyruvate as carbon sources for B 12 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 12 . Vitamin yields increased from 0.3 $$\mu g$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>g</mml:mi> </mml:mrow> </mml:math> B 12 per mmol lactate in anaerobic conditions to 2.4 $$\mu g$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>g</mml:mi> </mml:mrow> </mml:math> B 12 per mmol lactate and 8.4 $$\mu g$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>g</mml:mi> </mml:mrow> </mml:math> B 12 per mmol propionate in microaerobic conditions. Yield per cell dry weight (CDW) increased from 41 $$\mu g$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>g</mml:mi> </mml:mrow> </mml:math> per g CDW in anaerobic conditions on lactate to 92 $$\mu g$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>g</mml:mi> </mml:mrow> </mml:math> per g CDW on lactate and 184 $$\mu g$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>g</mml:mi> </mml:mrow> </mml:math> per g CDW on propionate in microaerobic conditions. Conclusions Here we have shown both B 12 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 12 by P. freudenreichii.

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