MODULATION OF GLYCEROL METABOLISM PATHWAYS BY Pediococcus pentosaceus FROM WINE

SERGIO ENRIQUE PASTERIS; SAAD, A. M. S.

Paris-France

Congreso; THE WORLD OF MICROBES; 2002

Pediococcus pentosaceus N5p uses glycerol as sole carbon source in microaerophylic contiditions by the glycerol kinase pathway, that involves  glycerol kinase (GK) and NAD-independent glycerol 3-P dehydrogenase (G3PDHi). In addition, low level of glycerol  dehydrogenase (GDH) activity was detected. We studied the modulation of the expression of both pathways by glycerol and oxygen availability. The strain was grown in MRS medium with glycerol (5,7 to 42,6 mM) in aerobic and anaerobic conditions. In aerobiosis, the enzymes activities of the GK (GK, G3PDHi) and GDH (GDH, DHA-K) pathways were expressed in the presence of glycerol and the higher activities were found under glycerol-limiting conditions. Further increases in glycerol concentration  produce a decreased of enzymes activities. In anaerobiosis, the levels of the enzymes activities of the GK pathway were lower than aerobiosis whereas the higher levels of the enzyme activities of the GDH pathway were detected in anaerobiosis. Maximum enzyme activities were determined with glycerol-limiting concentration, but the increase in glycerol concentration affected only the second enzyme (G3PDHi and DHA-K) activity of both pathways. In both incubation conditions the product obtained from glycerol were D-lactate, acetate and diacetyl. In addition, in aerobiosis, 2,3-butanediol was detected. From these results we can conclude that in Pediococcus pentosaceus N5p, glycerol concentration regulates the catabolism of glycerol and that the expression of GK and GDH pathways depend on the oxygen availability.