Catabolism of aromatic amino acids in cheese-related bacteria: aminotransferase and decarboxylase activities

摘要

Bacterial decarboxylases and aminotransferases may be involved in the production of flavour or off-flavour compounds from aromatic amino acids during cheese ripening. Transamination is one of the first steps in amino acid catabolism for both lactococci and lactobacilli (Gao et al. 1997; Klein et al. 2001). Biologically active amines, produced by decarboxylation, such as tyramine, phenylethyl-amine, tryptamine, histamine, cadaverine and putrescine, known as biogenic amines, have been found in cheese and can cause migraine and hypertension in susceptible consumers (McSweeney & Sousa, 2000). In this study, we investigated whether several cheese-related bacteria, including lactic acid bacteria (LAB) and strains isolated from the surface of smear cheese, were capable of transamination and decarboxylation of aromatic amino acids. The activity of amino acid catabolic enzymes from smear strains has not been studied previously and compared with the activities of LAB. The production of biogenic amines by selected strains was also studied in a chemically defined medium, which was designed to simulate cheese-ripening conditions. It has been shown that under simulated cheese ripening conditions, certain lactobacilli and lactococci produce enzymes active in catabolism of sulphur-containing and aromatic amino acids (Gao et al. 1997; Gummala & Broadbent, 1999, 2001), however, the enzymes of smear strains have not been studied in this manner.