Knockout of the p -Coumarate Decarboxylase Gene from Lactobacillus plantarum Reveals the Existence of Two Other Inducible Enzymatic Activities Involved in Phenolic Acid Metabolism

Abstract

ABSTRACT Lactobacillus plantarum NC8 contains a pdc gene coding for p -coumaric acid decarboxylase activity (PDC). A food grade mutant, designated LPD1, in which the chromosomal pdc gene was replaced with the deleted pdc gene copy, was obtained by a two-step homologous recombination process using an unstable replicative vector. The LPD1 mutant strain remained able to weakly metabolize p -coumaric and ferulic acids into vinyl derivatives or into substituted phenyl propionic acids. We have shown that L. plantarum has a second acid phenol decarboxylase enzyme, better induced with ferulic acid than with p -coumaric acid, which also displays inducible acid phenol reductase activity that is mostly active when glucose is added. Those two enzymatic activities are in competition for p -coumaric and ferulic acid degradation, and the ratio of the corresponding derivatives depends on induction conditions. Moreover, PDC appeared to decarboxylate ferulic acid in vitro with a specific activity of about 10 nmol · min −1 · mg −1 in the presence of ammonium sulfate. Finally, PDC activity was shown to confer a selective advantage on LPNC8 grown in acidic media supplemented with p -coumaric acid, compared to the LPD1 mutant devoid of PDC activity.