Characterization of thoeniicin 447 produced by Propionibacterium thoenii

[摘要] ENGLISH ABSTRACT:Antimicrobial peptides continue to be one of the most important classes of food additives.The food industry is especially interested in the application of naturally occuring andbiologically derived preservatives. Among the metabolites of industrial importance producedby propionibacteria are peptides called bacteriocins. Bacteriocins are ribosomally synthesizedpeptides with antagonistic activity against closely related microorganisms. Manymicroorganisms associated with food produce bacteriocins, which have stimulated interest inthe use of these peptides as natural food preservatives. Numerous bacteriocins are producedby lactic acid bacteria, but only a few have been reported for propionibacteria. Sincepropionic acid bacteria have GRAS (generally regarded as safe) status, their metaboliccompounds should be safe for human consumption.Propionibacterium thoenii 447, isolated from Emmentaler cheese, produces abacteriocin-like peptide, named thoeniicin 447, with a narrow spectrum of activity. Thepeptide displays a bactericidal mode of action against Lactobacillus delbrueckii subsp.bulgaricus and a bacteriostatic action against Propionibacterium acnes.Optimal bacteriocin production was detected during the early stationary growth phase.The peptide is resistant to heat treatments of 60°C and 80°C for 15 and 30 min and to 100°Cfor 15 min, but loses 80% of its activity after autoclaving (10 min at 121°C). Thoeniicin 447remains active after incubation in buffers with pH values ranging from 1-10. The peptide isinactivated by pepsin, pronase, a-chymotrypsin, trypsin and Proteinase K. Thoeniicin 447was partially purified by ammonium sulfate precipitation, followed by SP-Sepharose cationexchange chromatography. The estimated size of thoeniicin 447, according to tricine-SDSPAGE,is approximately 6 kDa. Based on DNA sequencing, the mature peptide is 7130 Da insize and homologous to propionicin Tl produced by P. thoenii strain 419.Thoeniicin 447 is a relatively small, cationic and heat-stable peptide and can therefor beclassified as a member of class II bacteriocins. These features are very similar to those ofbacteriocins produced by lactic acid bacteria. However, no unique classification system hasbeen proposed for bacteriocins of propionibacteria.As a member of the genus Propionibacterium, P. thoenii 447 is generally regarded assafe. This, together with the narrow spectrum of activity, particularly the action against P.acnes, heat tolerance of thoeniicin 447 and its activity over a wide pH range renders thepeptide suitable for possible pharmaceutical applications.

[发布机构] Stellenbosch University