Development of Lactic Acid bacteria starter culture for probiotic yogurt

Abstract

Lactobacillales or lactic acid bacteria (LAB) are one of the most numerous groups of bacteria linked to humans. Lactic acid bacteria show antimicrobial properties and these are generally recognized as safe (GRAS). The primary antimicrobial effect exhibited by the LAB is the production of lactic acid and a lower pH. In recent years, it has been seen that, several pathogenic bacteria are getting resistant to multiple antibiotics. In such conditions, new probiotics with potential antimicrobial properties can play an important role. In the present study, the industrially important lactic acid bacteria are mainly focused with the purpose of creating a probiotic starter culture. The study started with 20 isolates of LAB isolated from fermented vegetables and dairy products from the previous project. Among them 10 isolates were selected with maximum growth on MRS media. The antagonistic activity of these isolates was monitored using several parameters. The agar well diffusion results zone of inhibition with the cell-free supernatant of LAB isolates derived from Cauliflower, Carrot, Cabbage, Brinjal, Aarong yogurt, Dhaka cheese against indicator organisms Streptococcus agalactiae, Streptococcus pyogenes, Streptococcus pneumoniae, Bacillus subtilis, Bacillus cereus, Shigella dysenteriae, Shigella flexneri, Klebsiella sp., Enterobacter cloacae, and Salmonella typhi. Measured pH of cell-free supernatant and MRS broth was in higher range. The aim of this study is to find out antimicrobial properties present in LAB strains isolated from fermented vegetables and dairy products and developing an economically affordable probiotic yogurt starter culture. The production of probiotic yogurt starter culture involved inoculating three types of milk: whole milk, skimmed milk and powdered milk with the LAB isolates. Four hours to an overnight incubation at 30-40 ºC showed desired yogurt production. Further dehydration of a portion of the yogurt at 65 ºC for 2-3 hours gave yogurt powder. Finally addition of the produced yogurt powder into milk sample resulted in yogurt again. Such yogurt powder can be industrially manufactured at a low cost in developing countries where the consumption of probiotic products is growing intensively. Consumption of active probiotic yogurt can eventually lessen the intake of traditional antibiotics.