Detalle de: Glycerol and cobalamin metabolism in lactobacilli: relevance of the propanediol dehydrogenase pdh30

The genes involved in the glycerol metabolism, glycerol dehydratase (gdh) and two propanediol dehydrogenases (pdh30 and pdh1734), were analyzed in different reuterin- and non-reuterin-producing lactobacilli of biotechnological interest. All the reuterin-producing lactobacilli expressed the gdh, pdh30 and pdh1734, except Lb. coryniformis CECT 5711 which did not contain pdh30. Reuterin production levels in Lb. coryniformis CECT 5711 were much lower than those in reuterin-producing Lb. reuteri. A positive relationship between cobalamin production levels and reuterin production levels was observed in all reuterin-producing lactobacilli tested. Intriguingly, when Lb. coryniformis CECT 5711 was supplemented with cobalamin, a seven times increase in reuterin production was observed. On the other hand, Lb. brevis ESI38 that possess and express gdh, pdh30 and pdh1734, was unable to produce reuterin or cobalamin. To study the role of pdh30 during glycerol metabolism, the gene disruption mutant Lb. brevis INIA ESI38::pORI28-pdh30 was constructed. HPLC analysis of the glycerol fermentation products showed an involvement of the pdh30 in the 3-hydroxypropionic acid (3-HP) biosynthesis. However, Lb. coryniformis, that lack pdh30, showed the higher levels of 3-HP, indicating other catalytic mechanisms to produce 3-HP in this strain. The 1,3-propanediol peak was detected in the Lb. reuteri and Lb. coryniformis chromatograms, but not in Lb. brevis, which also confirm divergences in Lactobacillus glycerol metabolism.