Synergistic bioremediation of petroleum-contaminated soil using immobilized consortium of Rhodococcus rhodochrous and Bacillus subtilis laccase

Petroleum-contaminated soil represents a significant environmental and public health challenge on a global scale. Microbial bioremediation has shown potential, yet the role of enzymes in enhancing petroleum degradation remains underexplored. In this study, the synergistic effects of Rhodococcus rhodochrous (R.rh) and Bacillus subtilis-derived laccase (BsLac) was investigated in the remediation of petroleum-contaminated soil. Immobilized R.rh (PSIMRH) and BsLac (ADIMLac) exhibited higher petroleum degradation rates than their free state, achieving 78.3% and 56.3% degradation in liquid systems, respectively. The combined treatment of PSIMRH and ADIMLac demonstrated a synergistic effect on petroleum degradation, achieving 43.6% with a maximum degradation constant of 0.0335 d^-1, representing a 202.7% improvement over untreated soil. PSIMRH enhanced petroleum degradation through microbial metabolism, while ADIMLac accelerated the initial breakdown of complex hydrocarbons into simpler, more bioavailable ones via enzymatic oxidation, providing growth substrates for microbes and significantly improving petroleum degradation rates. The microbial analysis revealed an increase abundance of known petroleum-degrading bacterial genera, including Rhodococcus, Lysobacter, Micromonospora, and Streptomyces. However, the presence of BsLac appeared to reduce the competitive advantage of Rhodococcus, promoting the proliferation of indigenous strains like Lysobacter and Streptomyces. These results suggest that enzyme-microbe synergy can enhance the bioremediation process by altering microbial community dynamics and accelerating petroleum degradation. This study attempts to remediate petroleum-contaminated pollution with the combined use of strains and enzymes, providing a new approach for the remediation of other pollution problems.