Propionibacterium freudenreichii, more than meets the ‘eyes’

Summary

Propionibacterium freudenreichii is a bacterium found in a variety of cheese types that is able to produce the human-active form of vitamin B₁₂ in high quantities and that has probiotic properties. In this research we studied the main metabolism of P. freudenreichii, aiming at increasing our understanding of survival in gastro-intestinal tracts and for increasing production of vitamin B₁₂. Due to its sensitivity to oxygen, P. freudenreichii is usually grown without oxygen. We have shown low oxygen contents are beneficial for P. freudenreichii and that these conditions can be used to produce higher biomass and vitamin B₁₂ contents. Furthermore, we have shown P. freudenreichii can metabolize an important gut substrate, 1,2-propanediol, by expression of bacterial organelles called bacterial microcompartments and that these compartments also allow utilization of ethylene glycol. The thesis concludes with a discussion on the impact of our findings on P. freudenreichii as probiotic.