Investigation of the probiotic characteristics of Lactobacillus fermentum isolates from Ghanaian fermented maize dough

Abstract

Isolates of dominant Lactobacillus fermentum from fermented maize dough were investigated for their probiotic characteristics with the purpose of selecting appropriate starter cultures to improve and enhance the quality and safety of maize dough. 21 isolates were tested for their tolerance to pH 2.5, their sensitivity to the toxic effect of bile salts, their antimicrobial activity and adhesion to Caco-2 cell lines. In general, all isolates showed good survival rates in MRS pH 2.5 and in the presence of bile salts (0.3% oxgall). The strains did not show growth at pH 2.5 but maintained a high cell viability. High viability and weak growth was observed for bile salts. Antimicrobial activity varied among the strains. 90% of the strains inhibited the growth of Shigella flexneri, 47% inhibited Salmonella typhimurium, 42% Escherichia coli, 19% Bacillus cereus and 19% Listeria monocytogenes under conditions of low organic acid production indicating the presences of other antimicrobial substances other then acid. For their adhesion potential 34% of the strains had the property to adhere to Caco-2 cells. They were not strongly adhesive compared to positive adhesive strains included as reference. For two strains verification of probiotic characteristics was carried out in a pig feeding trials. The results attained showed that one strain did not survive the maize fermentation process where as the other was recovered as the dominant. Lactobacillus sp. in the intestinal tract of the pigs. This indicated the importance of acid tolerance for probiotic cultures. The overall results indicate a rich source of strain variability in the micrbiota of maize dough in which strains with probiotic characteristics can be selected