Screening of thermophilic lactic acid bacteria producing bacteriocins in the tropics

Bacteriocin-like activity (BLA) was screened in 50 and 30 strains of thermo philic lactic acid bacteria (LAB) isolated from silages and fermented veget ables, respectively. The BLA of the isolates against some bacterial strains was hardly detected by the paper disk method, while in the isolates of 50 strains (62.5% of all) it was clearly detected by the spot-on-lawn method. Only one strain K-4 isolated from grass silage showed a clear BLA against E nterococcus faecium in both methods. The strain belonging to the genus Ente rococcus produced BLA in the logarithmic growth phase in MRS medium. The BL A was completely inhibited by treatment with trypsin, remained stable under boiling conditions and the molecular weight was about 20,000 based on SDS- PAGE analysis. The BLA produced by this strain was due to bacteriocin and p ositive against only Ec. faecium and Ec. faecalis.