Complete Genome Sequence and In Vitro Probiotic Assessment of Bacillus subtilis DC-11 Isolated from Traditionally Fermented Idli Batter.

Abstract

In this study, we reported in vitro probiotic assessment and complete genome sequence of Bacillus subtilis DC-11 isolated from traditionally fermented Idli Batter. The strain was evaluated for probiotic properties, biofilm formation, and antimicrobial compound production. The phenotypic safety was determined by accessing the strain's ability to produce enterotoxins, degrade mucin, and antibiotic sensitivity. Whole genome sequencing (WGS) was performed to identify the strain and determine genetic safety by analyzing the presence of plasmids, antibiotic resistance genes, and virulence factors. In the results, B. subtilis DC-11 showed 88.98% viability in gastric juice, and 98.60% viability in intestinal juice. It showed 18.33 ± 0.44% autoaggregation, 32.53 ± 3.11% adhesion to xylene, 0.98 ± 0.05 OD unit's adhesion to mucin (crystal violet equivalence at 550nm), 21.2 ± 2.3% adhesion to Caco-2 cells, and - 22.3 ± 0.65mV zeta potential. The highest co-aggregation was recorded with Escherichia coli (23.62 ± 0.70%). The strain was found negative for enterotoxin production, mucin degradation, and antibiotic resistance to the commonly used therapeutic antibiotics. It formed a good biofilm and capable of producing antimicrobial peptide subtilosin A with a molecular mass of 3400Da. The peptide has inhibited the growth of methicillin-resistant Staphylococcus aureus (18.6 ± 0.58mm). In genetic safety, no plasmids, antibiotic-resistant genes, and virulence factors were detected. Moreover, the strain showed close similarity with B. subtilis ATCC 6051 and proteins involved in probiotic attributes. In conclusion, B. subtilis DC-11 is safe potential probiotic candidate.