Peptidolytic, esterolytic and amino acid catabolic activities of selected bacterial strains from the surface of smear cheese

Enzymes produced by bacteria present on the surface of smear cheeses play essential roles in flavour development during cheese ripening. In this study, strains including brevibacteria, corynebacteria, staphylococci and brachybacteria, from the surface of two smear cheese (Tilsit and Gubeen) were screened for a range of enzyme activities including aminopeptidase (substrates: Leu-pNA and His-pNA), dipeptidase (Met–Ala, Ala–Met, Pro–Ala, His–Leu and Pro–Leu), tripeptidase (Phe–Gly–Gly, Gly–Gly–Gly and Leu–Ala–Pro), esterase (β-naphthyl butyrate, β-naphthyl caprate and β-naphthyl palmitate), l-methionine aminotransferase and cystathionine lyase activities. There were marked differences in the activities observed between different bacteria studied. Brachybacteria showed low activity on all substrates assayed. There was no consistency in activities within groups of related bacteria. For example, Staphylococcus equorum 14 showed higher activity than S. equorum 6 on all the substrates tested. Among the corynebacteria, Corynebacterium ammoniagenes CA8 had greatest aminopeptidase, esterase and cystathionine lyase activity while C. casei B showed more di- and tri-peptidase activity. It was noted that individual bacteria displayed similar activities on all three esterase substrates, i.e., the chain length of the fatty acid did not appear to affect activity. l-Methionine aminotransferase activity was observed in only one strain (S. equorum 14) whereas all strains had cystathionine lyase activity.