Biodegradation of crude oil by biosurfactant-producing microaerophilic bacterium Pseudomonas aeruginosa MAR1

Oil pollution presents a significant global environmental challenge that necessitates sustainable and eco-friendly solutions. One promising approach involves utilizing surfactant-producing microorganisms for the bioremediation of areas contaminated by crude oil. Biosurfactants enhance the microbial biodegradation of crude oil by increasing its bioavailability, thereby making the degradation process more efficient. In this study, oil-degrading and biosurfactant-producing bacteria were isolated from soil and water samples contaminated with crude oil, collected from Assam, India. Among all tested strains Pseudomonas aeruginosa MAR1 demonstrated superior biosurfactant production and crude oil degradation, evidenced by the largest halo zone (14 mm) on CTAB agar, highest oil displacement (42 mm), emulsifying activity (132.0 mL^-1), emulsifying index (E24) of 24.12 %, haemolysis clearance zone (16 mm), foaming activity (76.7 %), optimal growth (OD₆₀₀ = 1.99) in crude oil media, and highest degradation efficiency (85.34 %) in gravimetric analysis. The identification of this strain was confirmed through morphological, biochemical, and molecular (16S rRNA) analyses. Media optimization for biosurfactant production was performed using the One-Factor-at-a-Time (OFAT) method, focusing on surface tension reduction and absorbance (bacterial growth). The optimal conditions included glucose (1 %) and yeast extract (1 %) as carbon and nitrogen sources, respectively, with a pH of 7 and incubation at 30-40 °C. Under these conditions, a honey-colored biosurfactant was extracted using the acid precipitation method, yielding 1.8 g/L and demonstrating a critical micelle concentration (CMC) of 76.0 mg/L. The biosurfactant reduced the surface tension of water from 70.1 to 30.9 dynes/cm. Further analysis, including FTIR and HPLC, revealed the presence of rhamnolipids, specifically mono- and di-rhamnolipids. This study highlights the bioremediation potential of P. aeruginosa MAR1 and its biosurfactant, signifying their applicability in environmental remediation.