Catabolism of L-phenylalanine by some microorganisms of cheese origin

SummaryThe ability of 42 microorganisms isolated from cheese, including strains of yeasts,Geotrichum candidum, Arthrobacter, Moraxellaspp.,Brevibacterium linensandStaphylococcus saprophyticusspp. to produce phenethyl alcohol (PEA) from L-phenylalanine was studied. All the yeast strains produced labelled PEA from L-[U-14C]phenylalanine. Phenylpyruvic acid was detected as an intermediate of PEA production and CO2was 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 ofG. candidumstrains nor bacterial isolates produced PEA from L-Phe. Strains ofMoraxellaspp. and four strains of theS. saprophyticusgroup produced phenylacetaldehyde. For three strains ofArthrobacterspp., five ofB. linensand all theMoraxella,14CO2produced 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.