Screening and identification of lactic acid bacteria with antimicrobial activity against food-borne pathogen

Abstract

This study focused on screening and identification of lactic acid bacteria with antimicrobial activity against Escherichia coli from milk samples. There were 250 isolates, showing different antimicrobial activities. Five isolates with predominant anti-E. coli efficiency were chosen for the study of bacteria identification, bacterial growth as well as the stability in pH change, heating and proteolytic treatment. The sequences of 16s rDNA indicated that selected isolates were Lactobacillus sp.. The antimicrobial efficiency, described in the term of Antimicrobial Index (AI) ranged from 0.63 to 0.84. However, the anti-E coli activity did not change when performing the test under proteinase-treated condition and high temperature-treated condition. Conversely, the pH adjustment of cell-free bacterial culture to 7.0 demolished their antimicrobial activity. This data implied that their antimicrobial activities were results of acidic condition, produced by lactic acid bacteria. From this study, the selected lactic acid bacteria showed their potential as a starter culture for fermented foods.