Energy conservation by succinate decarboxylation in Veillonella parvula

SUMMARY: Veillonella parvula cannot grow with succinate as sole energy source. However, succinate decarboxylation simultaneous with malate or lactate fermentation increased growth yields by 2.4–3.5 g (mol succinate)-1. Malate was fermented stoichiometrically to acetate and propionate whereas lactate fermentation produced more acetate and considerable amounts of H2. Aspartate was utilized only in the presence of succinate as co-substrate. Methylmalonyl-CoA decarboxylase and ATP-dependent pyruvate carboxylase, but not methylmalonyl-CoA: pyruvate transcarboxylase, were detected in cell-free extracts of malate- or lactate-grown cells. The energetic aspects of these fermentation patterns are discussed.