Optimized bacterial consortium-based strategies for bioremediation of PAHs-contaminated soils: insights into microbial communities, and functional responses

Microbial technologies hold great promise for in situ remediation of polycyclic aromatic hydrocarbons (PAHs)-contaminated soils. However, the selection of enhancement measures and corresponding remediation strategies remains insufficiently understood. In this study, a series of enhancement treatments, including bacterial consortium inoculation (comprising Achromobacter denitrificans BP1, Rhodococcus aetherivorans BW2, and Lysinibacillus sp. BS3), nutrient addition, and bio-ventilation, were implemented to develop effective in situ remediation strategies for PAHs-contaminated soil. Over a 60-day incubation, the enhancement treatments achieved phenanthrene (PHE) degradation efficiencies of 68.0–94.7 % and benzo[a]pyrene (BaP) degradation efficiencies of 12.9–82.4 %. Degradation rates across soil layers followed the pattern: upper layer > lower layer > middle layer. Enhancement treatments significantly boosted soil dehydrogenase (DH) and fluorescein diacetate (FDAH) activities. Among these, the sequential consortium inoculation with nutrient addition treatment (T6) demonstrated the highest degradation efficacy. In the treatment T6, the relative abundance of consortium genera was significantly increased, playing critical roles in PAHs degradation. The connectivity and stability of the soil bacterial network were enhanced, providing greater resilience to pollutants. Quantitative PCR analysis showed that the enhancement strategy increased RHDα-GN gene abundance by 1.98-fold at the initial and maintained a positive correlation with PAHs residues throughout the process (p < 0.05), and the phe gene exhibited a continuous upward trend during remediation, ultimately reaching 1.61–1.96 times its initial abundance. Overall, this study provides a strong candidate of integrated enhancement strategies to advance in situ bioremediation of PAH-contaminated sites.