ISOLATION, IDENTIFICATION, AND PRELIMINARY CHARACTERIZATION OF Bacillus subtilis WITH BROAD-RANGE ANTIBACTERIAL ACTIVITY FROM MUONG KHUONG CHILLI SAUCE

Abstract

       Bacillus subtilis is usually found in foods such as dry cured sausages, cheeses, traditional fermented milks, etc., in which they cooperate with other microorganisms during fermentation, release amylases, lipases and proteases… B. subtilis not only play with probiotic role but also produce antimicrobial substance. Muong Khuong chilli sauce is a naturally fermented product derived from Muong Khuong special peppers without heat treatment and is able to be preserved in ambient conditions for 1.5-2 years. Amongst 512 types of colonies, 48 Bacillus sp. strains were isolated from 80 chilli samples. Their ability against pathogenic bacteria was determined using the agar-well diffusion method through measuring the inhibition zone diameter. The four pathogenic bacteria strains tested were Escherichia coli RG1.1, Salmonella typhi GT4.3, Listeria monocytogenes MI2.6, and Staphylococcus aureus TS1.9. The results of 16S rRNA genotype sequencing for the two strains, TO43.13 and TO53.2, that had broad-range antimicrobial activity indicated that the TO43.13 sequence was homologous up to 95% with B. subtilis BcX1 (JX504009.1) and B. subtilis EPP2 2 (JQ308548.1). The TO53.2 strain sequence was homologous up to 94% with the two strains B. subtilis Pe-Lg-1 (FR687210.1) and B. subtilis YT2 (HQ143571.1). The optimal conditions for the growth and development of these two strains were with a 0.6% concentrations of NaCl, a pH of 7, and a temperature of 35°C