Isolation and in vitro characterization of bacterial isolates from fermented pearl millet.

INTRODUCTION: This study aimed to isolate and characterize bacterial strains from fermented pearl millet and evaluate their in vitro characteristics.

METHODS: A total of 66 bacterial colonies were isolated, of which three representative isolates (PJ2, PJ8, and PJ23) were selected for further analysis based on the preliminary screening criteria. Based on 16S rRNA gene sequencing, the isolates were identified as Bacillus aryabhattai, Pediococcus pentosaceus, and Lactiplantibacillus plantarum.

RESULTS AND DISCUSSION: The selected isolates demonstrated tolerance to acidic pH and bile salt conditions, with survival rates ranging from 50.3 to 88.8% at pH 2.0 and 42.7 to 83.5% following exposure to 0.3% bile salts for 1 to 3 h of incubation. Under the tested in vitro conditions, the isolates exhibited antagonistic activity against foodborne pathogens, antioxidant activity, phenotypic exopolysaccharide-associated characteristics, and varying levels of cell surface hydrophobicity. Pediococcus pentosaceus PJ8 exhibited the highest DPPH radical scavenging activity (62.3%). In agar well diffusion assays, Lactiplantibacillus plantarum PJ23 demonstrated inhibitory activity against Escherichia coli (29.3 ± 4.0 mm), whereas Pediococcus pentosaceus PJ8 exhibited inhibitory activity against Bacillus cereus (35 ± 5 mm) and Staphylococcus aureus (40 ± 5 mm). Among the isolates, Lactiplantibacillus plantarum PJ23 displayed comparatively higher cell surface hydrophobicity values (45.7-50.3%). Overall, the findings demonstrated that the selected bacterial isolates exhibited preliminary in vitro characteristics under the conditions tested.