Synergistic Co-Metabolism of Aspergillus Niger, Azotobacter Vinelandii , and Pseudomonas Aeruginosa for Enhanced Bioremediation of Crude Oil–Polluted Soil: Implications for Soil Recovery and Food Security

Abstract

Petroleum-impacted soils containing total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAHs) restrict land reuse and pose long-term threats to soil productivity and food security in oil-producing regions. This study evaluates the performance of mutually adapted bacterial–fungal consortia comprising Pseudomonas aeruginosa, Azotobacter vinelandii, and Aspergillus niger, with targeted NPK nutrient amendments, for accelerating hydrocarbon removal and restoring soil function for post-remediation agricultural use. Simulated crude-oil-polluted soils (SCOPs) were treated under controlled soil glass columns (2.5 cm × 3.2 cm) at 30 ± 2 °C over 21- and 42-day periods. Microbial inocula were standardised at 1.5 × 108 cells cm−3. Nine treatment configurations evaluated live/inactive consortium members under bioaugmentation (BA) and combined bioaugmentation–biostimulation (BA+BS) conditions. TPH and PAH concentrations were quantified by GC-FID following n-hexane/dichloromethane extraction, and soil protein content served as a proxy for microbial biomass and soil quality recovery. First-order kinetic modelling and regression analysis were applied to all treatment groups. First-order kinetic modelling and Duncan's Multiple Range Test (DMRT) revealed that the ternary consortium featuring Live P. aeruginosa + Dead A. vinelandii + Live A. niger (Group A9/B9) achieved the highest overall bioremediation performance. This arrangement drove an 83.0% reduction in TPH (from 794.9 mg/kg to 138.5 mg/kg; k = 0.0416 d−1, t1/2 = 16.6 days) and a 76.4% reduction in PAHs (75.7 mg/kg to 17.9 mg/kg; k = 0.0343 d−1, t1/2 = 20.2 days), statistically outperforming biostimulated binary controls (P < 0.05). Soil protein concentration correlated positively with cumulative hydrocarbon removal (R2 = 0.71–0.89 across, p < 0.005 for BA+BS groups), confirming protein as a reliable activity indicator. The study proposes an operational bioremediation framework incorporating consortium selection, staged nutrient dosing, pH control, moisture and aeration management, and dual GC-FID/protein monitoring. Findings demonstrate that optimised microbial co-metabolism can shorten remediation timelines, lower environmental footprint and cost relative to physicochemical treatments, and measurably restore soil functions supporting post-remediation agricultural reuse and food security in oil-impacted regions.