Optimization and characterization of exopolysaccharide produced by Bacillus aerophilus rk1 and its in vitro antioxidant activities

Objective: In this study, the isolation and identification of Exopolysaccharide (EPS) producing bacteria from polluted soil samples and its in vitro antioxidant activities were investigated. Methods: Isolation and identification of bacteria was investigating using 16 s rDNA genome sequencing method. Further, optimization (pH, time, and temperature), purification and characterization of EPS were performed using different (UV, FT-IR, C-13-NMR and H-1-NMR) methods. In addition, 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2) scavenging activities of EPS were performed. Results: The molecular characterization of isolated strain was confirmed as Bacillus aerophilus by 16S rDNA sequencing. The sequence was submitted to NCBI (Genbank accession number MH553072). Characterization of EPS by UV, FT-IR, C-13-NMR and H-1-NMR revealed the presence of hydroxyl, carbonyl, and carboxyl functional groups. SEM analysis of EPS showed a solid surface with an irregular shape. The optimum conditions for EPS production were pH 7.0, cultivation time 72 h (3.73 +/- 0.211 g/L) and temperature 30 degrees C respectively. The yeast and sucrose extract showed higher EPS production. In addition, in vitro DPPH, H2O2 studies showed 56.6 and 67.5% of scavenging activity at 4 mg/mL of concentration. Conclusions: From this study, the novel EPS producing Bacillus aerophilus rk1 was identified. Further, the purified EPS showed good antioxidant activity. (C) 2021 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.