Bioremediation of benzoic acid in sequencing batch reactor using immobilized Pseudomonas sp. BJ-1

Benzoic acid (BA), a widely recognized low-molecular-weight organic contaminant, is widespread in wastewater and poses significant environmental risks. Consequently, the persistent existence of BA in the ecosystem necessitates the development of effective remediation strategies, particularly bioremediation method utilizing high-efficient degradation strains. In this study, a novel BA-degrading bacterium, Pseudomonas sp. BJ-1, was successfully isolated from activated sludge of a paper mill. Based on the central composite design and response surface method (CCD-RSM), the optimal parameters for the biodegradation of BA in an sequencing batch reactor (SBR) were determined as the initial BA concentration of 1037.86 mg·L⁻¹, immobilized bacterial pellets dosage (IBPD) of 213.87 g·L⁻¹, and pH of 7.02, where the maximum degradation efficiency was 99.10 ± 0.85 % at 24 h. Furthermore, the immobilized bacterial pellets maintained degradation capacity for 5 days, demonstrating a robust activity and structural integrity. Further analysis by whole genome sequencing and liquid chromatography tandem high-resolution mass spectrometry (LC-HRMS) indicated that the removal of BA was dependent on the ortho-cleavage pathway of catechol and eventually entered the TCA cycle. Notably, compared to 77.90 ± 5.17 % by free bacteria, the degradation efficiency of BA in the actual wastewater was dramatically enhanced to 98.59 ± 0.04 % by the immobilized bacterial pellets. This study highlights the feasibility of immobilized microbial technology in conjunction with the SBR system in the remediation of BA-containing wastewater, providing valuable insights into the application of bioremediation method in environmental management.