Acid resistance, bile tolerance and antimicrobial properties of dominant lactic acid bacteria isolated from traditional “maari” baobab seeds fermented condiment
Maari is a fermented food condiment obtained by spontaneous fermentation of seeds from the baobab tree (Adansonia digitata). Nine dominant lactic acid bacteria (LAB) strains, isolated from traditional maari fermentation were examined for their resistance to pH 2.5, their tolerance to 0.3% bile and their antimicrobial activities against pathogenic bacteria. The agar spot test was used to screen the dominant LAB for antagonistic activity against a total of 21 indicator organisms including Bacillus cereus strains, Salmonella spp., Listeria monocytogenes, Yersinia enterocolitica, Escherichia coli and Micrococcus luteus. It was observed that all LAB strains survived in 0.3% bile and exhibited antimicrobial activity against a broad spectrum of bacteria, including food spoilage and pathogenic organisms such as B. cereus, Salmonella spp., L. monocytogenes, E. coli and M. luteus. None of the tested LAB strains was active against Y. enterocolitica strains. At pH 2.5, Pediococcus acidilactici L87 survived over a period of 4 h whereas a slight decrease was observed for Enterococcus faecium L169. E. faecium L154 cell number decreased considerably. The rest of the tested strains did not survive at pH 2.5 over a period of 4 h. Based on the present results, P. acidilactici L87, P. acidilactici L169 and E. faecium L154 in addition to the Bacillus sp. which are the main microorganisms responsible of the fermentation of baobab seeds can be useful as starter cultures for improving maari quality and safety with respect to protection against food spoilage and pathogenic microorganisms.
Key words: Baobab seeds, maari, fermentation, lactic acid bacteria, acid resistance, bile tolerance, antimicrobial activity.