Probiotic potential of lactic acid bacteria strain LD/4

Abstract

Lactic acid bacteria (LAB) are a group of phylogenetically diverse Gram-positive bacteria. Strain LD/4 showed sigmoidal growth responses in the modified TGYE medium. The kinetics of antimicrobial production followed typically a primary metabolite and was detected after 3h of growth in modified TGYE medium, in the mid- log phase. Antimicrobial production increased continuously during the growth of the bacterium and maximum activity was observed at the beginning of the stationary phase (8h). Thereafter, the antimicrobial compound remained stable on further incubation. During bacterial growth another important feature was observed, the pH of the medium that dropped from neutral to acidic range, which is a characteristic feature of lactic acid bacteria. The antimicrobial activity was assayed in the culture filtrate using qualitative method i.e. agar well diffusion assay (AWDA), showed inhibition zone, which indicated the presence of antimicrobial activity. After the initial identification, probiotic potential of the strain LD/4 has been assessed in vitro by studying several properties such as cell surface hydrophobicity assays [spontaneous aggregation assay (SA), auto-aggregation assay (AA), salt aggregation test (SAT), surface accumulation assay (SAA), cell adherence to the glass surface, microbial adhesion to hydrocarbon (MATH)], and survival in the simulated condition. From all the conducted tests, strain LD/4 exhibited a moderate level of cell surface hydrophobicity and also showed low pH tolerance (pH 2.5).