Biosurfactant activity and biological hydrocarbon removal from crude oil by Bacillus paramycoides SB1

Petroleum hydrocarbon contamination remains a major environmental concern because hydrophobic compounds have limited accessibility to microbial cells. This study hypothesized that Bacillus paramycoides SB1 could maintain growth under crude-oil exposure while exhibiting biosurfactant activity associated with altered oil–water interfacial properties and measurable biological hydrocarbon removal. SB1 maintained growth in mineral salt medium supplemented with up to 2% (v/v) crude oil, reaching a maximum OD₆₀₀ of 0.787 at 36 h. Its cell-free supernatant exhibited biosurfactant activity, with an oil displacement zone of 1.77 ± 0.05 cm, emulsification index of 57.50 ± 3.80% against n-hexane, surface tension of 37.9 mN m−1, and interfacial tension of 8.4 mN m−1 against crude oil. Fourier transform infrared spectroscopy (FTIR) analysis provided preliminary evidence of peptide-associated functional groups consistent with a lipopeptide-like biosurfactant. During 21 days of incubation, residual total petroleum hydrocarbons (TPH) decreased from 93.98 ± 1.72% to 77.56 ± 1.14%, corresponding to a 17.47% relative reduction, compared with 3.9% in the uninoculated control. GC–MS characterized the initial crude oil as a heterogeneous mixture containing aliphatic, aromatic, and halogenated compounds. Lattice Boltzmann simulations parameterized with the measured interfacial tension further showed that wettability influenced pore-scale phase redistribution and residual oil trapping. Overall, the findings integrate biosurfactant activity, biological hydrocarbon removal, and pore-scale fluid behavior into a multiscale framework for evaluating the hydrocarbon-removal potential of B. paramycoides SB1.