Partial purification and characterization of the anti-listeria compount produced by Lactobacillus curvatus CRL1579.

P. CASTELLANO,; M. ARISTOY ; M. A. SENTANDREU; G. VIGNOLO ; F. TOLDRÁ.

Valencia

Congreso; FoodInnova; 2010

This work has as main objective to characterize lactocin AL705, a bacteriocin produced by L. curvatus CRL1579 previously isolated from regional meat products, in order to evaluate its potential as a new food protective agent. The antimicrobial compound displayed a strong anti-Listeria effect inhibiting L. monocytogenes, L. sellegeri, L. innocua, although no inhibition of Gram-negative microorganisms was observed. Proteolytic enzymes (trypsin, protease V and proteinase K) completely inactivated the antimicrobial effect of cell-free supernatant confirming the protein nature of the inhibitor. The antimicrobial activity was heat stable (45 min at 70°C) and showed inhibitory activity over a wide pH range (3.0 to 8.0). Production of lactocin AL705 by L. curvatus CRL1579 was initially detected at exponential phase and reached the maximum activity of 6,400 AU/ml in the early stationary phase. The anti-Listeria compound was isolated from cell free culture supernatant and further purified. Crude bacteriocin sample was prepared by a process of selective fractionation with ammonium sulfate followed by precipitation with methanol and reversed-phase HPLC of the supernatant on a C18 column. Active fractions were eluted between 24-32 % of acetonitrile, indicating its hydrophobic nature. The estimated molecular mass of the anti-Listeria compound was < 7000 Da on sodium dodecyl sulphate-polyacrylamide gel electrophoresis (PAGE), which is in accordance to molecular weighs previously reported for other anti-Listeria bacteriocins. On the basis of its biological characteristics and specific anti-Listeria action, Lactocin AL705 can be considered as a potential food preservative.