In vitro screen of Lactobacillus plantarum as probiotic bacteria and their fermented characteristics in soymilk

One hundred and two strains of Lactobacillus plantarum, all isolated from traditional dairy products of minority nationalities, were evaluated for in vitro probiotic properties, including acid and bile tolerance, aggregation activity, and antibacterial activity. Of these, 12 strains with a high tolerance to simulated gastric juice (pH 2.5, 3 h of incubation) were selected, of which eight of these also showed a good tolerance to bile salt. All selected 12 strains showed a high autoaggregation percentage after being incubated at room temperature for 20 h, and nine of these significantly inhibited growth of the five indicator intestinal pathogens. Six L. plantarum strains (IMAU10120, IMAU10156, IMAU40126, IMAU70004, IMAU60042, and IMAU60171) were selected for further evaluation of their fermentation characteristics, sensory quality, and viable counts, both during the fermentation process of soymilk and following a 28-day storage of the soymilk. The six strains had an acid-producing ability at the refrigerated temperature. All of the fermented soymilk samples had a viable count above log 8.45 CFU/ml, and viability in the samples was maintained during storage. Based on both the probiotic properties and fermented characteristics, L. plantarum IMAU10120 was the best potential probiotic strain of those tested for the production of fermented functional soymilk.