Biocompatibility, Antioxidant and Anti-Infective Effect of Biosurfactant Produced by Marinobacter litoralis MB15

Objective: In this study, the biosurfactant, produced by a potent non-pathogenic bacterial strain of Marinobacter litoralis MB15 was used for anti-microbial, anti-oxidant and biocompatibility assay. Materials and Methods: Biosurfactant producing bacteria were screened by oil displacement assay and emulsification assay. The best isolate was sequenced by 16S rRNA gene analysis. The biosurfactant was produced in modified Zobel marine broth media followed by the recovery of biosurfactant by solvent extraction method. The produced biosurfactant was characterized by using thin layer chromatography, Fourier transform infrared spectroscopy and Electron spray Ionization-Mass Spectroscopy analysis. 1-diphenyl-2-picrylhydrazyl (DPPH) assay, crystal violet assay, 3-(4, 5-dimethylthiazole-2-yl)-2, 5-diphenyltetrazolium bromide) (MTT) assay were performed to determine the anti-oxidant activity, anti-microbial activity and biocompatibility of biosurfactant respectively. Results: The best biosurfactant producing isolate was found to be Marinobacter litoralis. The produced biosurfactant was characterized as rhamnolipid molecules, comprising of both mono (m/z = 358.98 [M+H]+, Rha-C12:2; m/z = 543.29 [M+K]+,Rha–C10-C10) and di rhamnolipid homologs (m/z = 689.34 [M+K]+,Rha-Rha-C10-C10). The product showed excellent antimicrobial properties against several pathogens including Candida albicans, Escherichia coli, Vibrio parahaemolyticus, Bacillus subtilis, S. aureus, Klebsiella pneumonia and Streptococcus pyogenes. The antioxidant activity of biosurfactant was 72.6% at 5 mg/ml. The biosurfactant showed negligible cytotoxic effect to mouse L292 fibroblastic cell line. Most importantly, after 48 h of incubation, 84.7 % of cell viability on L292 was observed at 250 μg/ml for biosurfactant. Conclusion: Therefore, this investigation shows the utility of rhamnolipids as non-cytotoxic, natural antimicrobial and antioxidant agent for various industrial and biomedical application.