Propionate acts as earboxylic group acceptor in aspartate fermentation by ropionibacterium freudenreichii

Abstract

Cells of Propionibacterium freudenreichii ssp. shermanii and ssp. freudenreichii did not show significant growth or product formation in a mineral medium with 10 mM aspartate or 10 mM fumarate, vitamins, and a small amount (0.05% w/v) of yeast extract. In the presence of added propionate, growth with aspartate or fumarate was possible, and depended strictly on the amount of propionate provided, according to the equation: 3 aspartate + propionate ~ 3 succinate + acetate + CO2 + 3 NH3. Cocultures of P.freudenreichii with the succinate-decarboxylating strain Ft2 converted 3 aspartate stoichiometrically to acetate and 2 propionate. High activity of methylmalonyl-CoA: pyruvate transcarboxylase, and lack of methylmalonyl-CoA decarboxylase and oxaloacetate decarboxylase activity in cell-free extracts of aspartate-grown cells indicated that failure to use aspartate as sole substrate was due to the inability of these strains to catalyze a net decarboxylation of C4- dicarboxylic acids.