ASSESSMENT OF THE PROBIOTIC POTENTIAL OF Bacillus species ISOLATED FROM LOCALLY FERMENTED LOCUST BEAN ‘IRU’

Abstract

ABSTRACT

Bacillus species is gaining interest in human health related functional food research due to their probiotic property and survivability under hostile environment of the gastrointestinal tract. There is currently the need to shift focus to locally produced foods that are rich in probiotics as they can confer great health benefits on humans. This study assessed the probiotic potential of Bacillus species isolated from a locally fermented locust bean “Iru” Bacillus species were isolated from “Iru” using standard microbiological techniques. The isolates were characterized using morphological and biochemical methods, then were then subjected to preliminary acid test at varied pH rates (2.0, 4.0 and 7.0) and bile concentrations (0.3, 0.5 and 1.0) %. The isolates that survived the preliminary test were further subjected to varied pH values (2.0, 3.0, 4.0, 5.5 and 7.0) and bile concentrations (0.1, 0.3, 0.75 and 1.0) %. Antibiotic susceptibility test, antimicrobial activity against some bacterial pathogens and toxin production ability of the Bacillus isolates were carried out. The Bacillus isolates were further assayed for their hydrophobicity, auto-aggregation, co-aggregation ability and cholesterol reducing ability. Molecular characterization was carried out on the isolates and their clonal diversity with other probiotic Bacillus deposited in the National Center for Biotechnology Information (NCBI) databank was determined. Data obtained were analyzed using Statistical Package for Social Sciences Version 17.0. Values were separated using mean and standard deviation. Seven Bacillus species were identified and only three; Bacillus subtilis strain NCDO 1769, Bacillus thuringiensis strain HER1410 and Bacillus sp. RZ2MS9 had high survival rates (66.3% - 97.9%) at different pH values and (76.7% -97.9%) at different bile concentrations. The Bacillus isolates showed susceptibility to antibiotics used. Zones of inhibition against bacterial pathogens ranged from 6.0 - 19.0 mm and all the three Bacillus species tested negative to the toxins. The three Bacillus isolates had high survival rates (68 -870) % when assayed for hydrophobicity and auto-aggregation. Survival rates of co-aggregation was however low (18.6 - 20.0) %. The three isolates utilized cholesterol 200mg/dl at a reduction rate of (91.1, 86.1 and 95.4) % respectively. Result of molecular characterization confirmed the three Bacillus isolates as Bacillus subtilis strain NCDO 1769, Bacillus thuringiensis strain HER1410 and Bacillus sp. RZ2MS9. The three isolates showed diversity with other probiotic Bacillus species deposited in the NCBI data bank as the three of them clustered separately with other strains. In conclusion, this research study revealed that the Bacillus in “Iru” exhibited probiotic and hypocholesterolaemic properties.