Characterization and molecular identification of probiotic bacteria and their proliferation analysis on treatment with metformin from home-made and commercial curd of south India

Abstract

Probiotics have gained much attention for their health benefits, which has led to the widespread use of food products containing probiotic bacteria and probiotic supplements. Since most South Indian households regularly consume curd, this study aims to investigate the probiotic potential of bacteria from different homemade curd (HMC), commercial curd (CC), and commercial oral probiotic supplements (CP). In the current study, a total of 25 strains were isolated and evaluated for probiotic properties. Strains from CP showed the highest bile acid tolerance, whereas strains from CC had more propensity to form biofilms. Antibiotic sensitivity was seen across all samples. Also, molecular characterization by 16 S rRNA sequencing identified Lactobacillus sp.(n = 14), Enterococcus sp.(n = 5), Bacillus sp.(n = 4), and Acetobactor sp.(n = 1). Furthermore, though probiotics are clinically explored in diabetic therapeutics, no study has addressed the question of whether metformin can affect the probiotic strains. Our results showed no change in bacterial growth at 5 mmol/L, 6 mmol/L, 12 mmol/L, 30 mmol/L, 45 mmol/L, and 60 mmol/L of metformin. MTT assay revealed that cell viability was lower in CP than CC at 5 mmol/L of metformin. HMC had enhanced adhesion to A549 cells on metformin treatment (30 mmol/L) than CC or CP strains. There was no difference in α-amylase activity across the three groups. To conclude, our findings suggest that probiotic bacteria isolated from HMC, CC, and CP sources offer health benefits for both non-diabetic individuals and diabetic patients undergoing metformin therapy, and future studies should elucidate the metformin-mediated pathways in probiotics.