Enhanced Biodegradation of Polycyclic Aromatic Hydrocarbons in Contaminated Soils Using Biochar-Immobilized Mixed Bacteria: Mechanisms and Microbial Responses

Polycyclic aromatic hydrocarbons (PAHs), common environmental pollutants, exhibit “triple” toxicity and degrade slowly in soil. Immobilised microbial technology is an innovative environmental protection technology that can significantly improve the degradation efficiency of PAHs. In this study, we developed biochar immobilized mixed bacteria (BIM) materials using rice straw biochar (RBC) as a carrier, established a highly effective PAH-degrading mixed bacteria (M), and conducted a 49-day soil remediation experiment. The results indicated that BIM, RBC, and M eliminated 95.50%, 87.01%, and 90.16% of phenanthrene (PHE), and 73.78%, 44.61%, and 50.94% of benzo[a]pyrene (BaP), respectively. The diversity of soil microbial communities was significantly enhanced by BIM, and the results of the Linear discriminant analysis Effect Size (LEfSe) analysis revealed that the genera with the most notable differences included Lysinibacillus, Rhodococcus, and Lysobacter. Additionally, the Mantel test and correlation heat map results demonstrated that the inclusion of exogenous microbes was the most significant factor influencing biomarker changes, with BIM and M being the primary contributors to alterations in microbial community structure and gene abundance. To further improve the degradation of PAHs and investigate the responses of soil microbial community structure and diversity, we developed effective materials for PAH adsorption and degradation. Along with looking at its improved breakdown of PAHs in contaminated soil, we also reveal the method of soil ecological component identification and biodegradation under microbial reaction. This research provides a theoretical and technological foundation for green and low-carbon remediation technologies aimed at addressing soil contamination by PAHs.

Graphical Abstract