Leveraging the green remediation potential of a biosurfactant producing indigenous oleophilic bacterium isolated from hydrocarbon soiled environment

Abstract

The present investigation focused on the physicochemical characterization and bioprospecting of an Indigenous oleophilic bacterium (OB) and its biosurfactant (BA) in bioremediation application. Within 14 days of culture at 30 °C with 2% (v/v) n-hexadecane, the OB could reduce the surface tension of the culture medium up to 34.4 mN/m. Standard screening tests verified that the isolated OB produces BA and displayed an average of about 98% 16S rRNA sequence similarity with Pseudomonas aeruginosa. The BA production was 434.7mg/l with a CMC of 195.6 mg/l, which was purified and characterized through standard chromatographic and spectroscopic techniques. FTIR analysis confirmed the glycolipid nature of the BA. TLC of the partially purified BA revealed two homologues of rhamnolipid (RL), which were subsequently purified by column chromatography and had their structures confirmed by ¹H and ¹³C NMR. Seven distinct RL congeners were identified by LCMS-MS, of which di-RLs constituted a notably large proportion.. The BS displayed a stable and substantial emulsification index (E₂₄%) against different hydrocarbons, especially against crude oil. Both surface and emulsification activities of BS demonstrated significant stability against various pH (3-10), temperature (4-121 °C), salinity (2-10%) and heavy metals. The OB could able to utilize crude oil within 60 days, confirmed through GCMS. In the soil washing experiment, BS was able to separate ≥80% of crude oil from the contaminated sand at CMC. Results suggest that RLs and their producer, oleophilic bacterium, are propitious for various biotechnological applications in the bioremediation of extreme and complex environments.