Biosurfactant Triggered Degradation of Polyaromatic Hydrocarbons in Agricultural Soil

Among the various polyaromatic hydrocarbons (PAHs), naphthalene, fluorene, phenanthrene and pyrene are the predominant pollutants commonly detected in agricultural soils, primarily due to transportation emissions, atmospheric deposition and accidental spillages. To facilitate the degradation of these persistent pollutants, a lipopeptide-based biosurfactant was isolated from Lysinibacillus sp. MW444883 (Accession No.: NAIMCC-B-03918). The biosurfactant exhibited strong oil dispersion activity, showed no halo formation in the CTAB/methylene blue agar test, indicating the absence of glycolipid-type surfactants and produced blue and violet colour reactions with bromothymol blue and biuret tests, respectively, confirming its amino-containing (lipopeptide) nature. Its excellent emulsification property, as evidenced by oil fragmentation into fine droplets, enhanced the bioavailability of hydrophobic PAHs, making them more accessible for microbial degradation in soil. Biodegradation studies conducted in Inceptisol alkaline soil (Delhi soil) demonstrated degradation till 21 days and half-life ranging from 1.5-8.3 days for naphthalene, 7.4-14.2 days for fluorene, 6.1-22.6 days for phenanthrene and 12.3-27.2 days for pyrene under different treatment conditions involving oil, biosurfactant, and Kocuria rosea in comparison with native microbial activity. These findings highlight the potential of the Lysinibacillus derived lipopeptide biosurfactant as an effective bioremediation agent for the degradation of priority pollutant (PAHs) in agricultural soils.