PROPERTIES OF BACTERIOCINS PRODUCED BY LACTIC ACID BACTERIA ISOLATED FROM RAW COW'S MILK

Abstract

Strains PDI4, BV20, PD2.9 were isolated from raw cow's milk of Bavi and Phu Dong dairy farms. Bacteriocins produced by strains PDI4, BV20, PD2.9 were active against closely related lactic acid bacteria including Lb. plantarum JCM 1149, Lb. plantarum JCM 1048,Lb. algilis JCM 1230, Lb. salivarius JCM 5804. The antimicrobial spectrum of these strains was nearly identical to that nisin. These bacteriocins are heat stable at low pH values. Antimicrobial activities of the bacteriocins were not destroyed by exposure to elevated temperatures from 60 to121°C at pH2 and pH 5. However, bacteriocins of these strains were lost activity at high pHvalues (from pH 8 and 9). Bacteriocins produced by PDl4 and P02.9 have been lost activity when were treated at high temperature (121°C) and pH as well (pH = 7) while bacteriocin synthesizes by BV20 was stable at this condition (3% activity remained). These 3 bacteriocins were affected by proteolysis enzymes as trypsin, a - chymotrypsin, papain, bromelin, proteinaseK. SOS - PAGE analysis of the purified bacteriocins indicated they were the same molecular weight of3.3 kOa as that of nisin