Catabolism of L-phenylalanine by some microorganisms of cheese origin

Abstract

Summary The ability of 42 microorganisms isolated from cheese, including strains of yeasts, Geotrichum candidum, Arthrobacter, Moraxella spp., Brevibacterium linens and Staphylococcus saprophyticus spp. to produce phenethyl alcohol (PEA) from L-phenylalanine was studied. All the yeast strains produced labelled PEA from L-[U- 14 C]phenylalanine. Phenylpyruvic acid was detected as an intermediate of PEA production and CO 2 was produced by decarboxylation of this acid. For five strains tested, the level of PEA which had accumulated in the culture at the end of exponential growth phase represented 39–52% of the L-Phe added. None of G. candidum strains nor bacterial isolates produced PEA from L-Phe. Strains of Moraxella spp. and four strains of the S. saprophyticus group produced phenylacetaldehyde. For three strains of Arthrobacter spp., five of B. linens and all the Moraxella , 14 CO 2 produced from uniformly labelled L-Phe represented more than one carbon atom of the L-Phe molecule, suggesting that Phe was catabolized beyond the stage of phenylacetic acid. Production and disappearance of PEA during Camembert cheese ripening is probably related to the metabolic activity of microorganisms present at the cheese surface.