Identification of a secreted lipolytic esterase in Propionibacterium freudenreichii
Résumé
Free fatty acids are important flavour compounds in cheese, where they bring “pungent”, “rancid”, “cheese”, and “fruity” notes. They mainly result from the lipolytic activity of cheese micro-organisms. In Emmental cheese, the main agent of lipolysis is Propionibacterium freudenreichii, a species used as a ripening culture. By combining in silico prediction of subcellular localisation, zymography, and identification by mass spectrometry, we recently demonstrated that P. freudenreichii CIRM1T possess one secreted lipolytic esterase, PF279. PF279 possesses an atypical motif TXSXG instead of the classical GXSXG of esterases, and shares only weak homology with the proteins of NCBI nr database. It is constitutively expressed during Pf growth and is active on milk fat. Transformed P. freudenreichii CIRM1T clones over-expressing PF279 showed ~5 times more lipolytic activity on milk fat than the wild strain. PF279 is likely a key component in Emmental cheese lipolysis.