Enhanced petroleum hydrocarbon degradation by biosurfactant-producing bacteria from Iko River estuarine sediments, Akwa Ibom State, Nigeria.

Hydrocarbon contamination of estuaries poses a major environmental concern because of persistence and ecological toxicity, while nutrient availability often limit natural attenuation by indigenous microorganisms. This study evaluated the effects of glucose and sucrose biostimulation on petroleum hydrocarbon degradation by biosurfactant-producing bacteria from Iko River estuarine sediments, Akwa Ibom State, Nigeria, using standard physicochemical and microbiological techniques. Heavy metal concentrations of iron (1.43 mg/kg), vanadium (1.74 mg/kg), zinc (3.28 mg/kg), lead (3.01 mg/kg), cobalt (0.09 mg/kg), and nickel (0.43 mg/kg) were below sediment quality guideline thresholds. The mean heterotrophic bacterial abundance was 5.57 ± 0.9 log₁₀ CFU/g, which was 2.34 times higher than the 2.38 log₁₀ CFU/g recorded for hydrocarbonoclastic bacteria. Molecular characterization identified the isolates as Bacillus subtilis (MH145363.1), Pseudomonas aeruginosa (MZ299002.1), Bacillus cereus (AJ277908.1), Micrococcus luteus (OP848034.1), and Bacillus luti (CP040336.1), showing 99.72-100% similarity to GenBank reference strains. Pseudomonas aeruginosa exhibited 64% emulsification activity and reduced surface tension to 31.2 mN/m, indicating strong biodegradation potential. Glucose supplementation increased bacterial growth, with optical density ranging from 0.15 to 1.17 at 20% glucose by days 30-40, compared to 0.10-0.20 in the control, suggesting strong stimulation of microbial proliferation. Sucrose also enhanced growth, with optical density ranging from 0.38 ± 0.01 to 1.01 ± 0.02 at 20% sucrose by day 50, compared with 0.15 ± 0.02 to 0.20 ± 0.02 in the control. Glucose stimulation at 15% improved the abundance of Pseudomonas aeruginosa, with values ranging from 5.30 ± 0.92 to 5.74 ± 0.62 log₁₀ CFU/mL by day 50, while the unstimulated control declined to 3.94 ± 0.45 log₁₀ CFU/mL at the same time point, indicating nutrient limitation. Sugar amendment enhanced hydrocarbon degradation, with the highest efficiency observed at 10% glucose, recording 59.56%, followed by 5% and 15% glucose at 57.13% and 55.03% respectively, compared to 31.11% in the control. Sucrose treatments also improved degradation, with values ranging from approximately 50% to 67%, although no clear concentration-dependent trend was observed. Simple sugar biostimulation enhanced microbial growth and hydrocarbon degradation, highlighting a cost-effective and environmentally sustainable strategy for the bioremediation of hydrocarbon-impacted estuarine environments.