ISOLATION AND SELECTION OF LACTIC ACID BACTERIA FROM VIETNAMESE FERMENTED PORK MEAT PRODUCT WITH NTIMICROBIAL ACTIVITY AND CHARACTERIZATION OF BACTERIOCIN

Abstract

      The objective of this study was to isolate lactic acid bacteria (LAB) from Vietnamese fermented pork meat (nem chua) and to determine their antimicrobial activity. A total of 101 LAB isolates were screened for their inhibitory effect on the indicator organism Lactobacillus plantarum JCM 1149 in the first selection by the agar spot test. Results showed that 58 isolates had activity against Lb. plantarum JCM 1149. From the 58 LAB, the second selection by agar well diffusion method used Lb. plantarum JCM 1149, Listeria monocytogenes, Bacillus cereus, E. coli, and Salmonella typhimurium as indicator organisms, and were inhibited by 18, 17, 6, 16, and 0 isolates, respectively. There were 5 strains (NH3.6, NT1.3, NT1.6, NT2.9, and NT3.20) with wide spectrum inhibition antimicrobial activity of both pathogenic gram-positive B. cereus and L. monocytogenes, and gram-negative E. coli. Furthermore, protease K enzyme was applied to test the antimicrobial activity of the 5 LAB isolates by bacteriocin, acid, or H₂O₂. Results indicated the NH3.6 strain had antimicrobial activity by bacteriocin. In addition, this research characterized the bacteriocin of the NH3.6 isolate and found it was stable in temperatures at 100^oC and 120^oC for 10 minutes, a pH = 3, and tolerant of NaCl concentration less than 8%.