Ability of lactic acid bacteria to produce volatile phenols

Thirty-five strains of lactic acid bacteria (20 species) were screened for the ability to produce volatile phenols from the corresponding phenolic acids, p-coumaric and ferulic, in culture medium. The concentration of vinylphenols and ethylphenols in the growth medium was analyzed by gas chromatography. Results showed that 13 strains (37%) were able to produce volatile phenols from p-coumaric acid, although only three (9%) produced 4-ethylphenol, the final product of the p-coumaric acid metabolic pathway. The reduction step of this pathway was only found in the Lactobacillus genus: L. brevis, L. collinoides, and L. plantarum. Seven of the eight pediococci strains studied were able to produce 4-vinylphenol but not 4-ethylphenol from p-coumaric acid. The two Oenococcus oeni strains and the strain of Leuconostoc mesenteroides studied did not produce either of the two p-coumaric acid derivatives. Strains that produced volatile phenols were used in subsequent studies at lower phenolic acid concentrations. Experiments with added 5 mg/L of p-coumaric acid showed that some strains can still produce relatively high (up to 800 Hg/L) concentrations of 4-ethylphenol. The capacity of lactic acid bacteria to produce volatile phenols from ferulic acid was much lower than its capacity to produce volatile phenols from p-coumaric acid.