Degradation of BTEX or pyridine by a salt-tolerant Rhodococcus ruber strain KH-1: characterization, metabolic pathways, and application

The sustainable treatment of industrial wastewater from printing processes poses significant challenges due to its high salinity, elevated pH levels, and the presence of multiple toxic contaminants. Bioremediation mediated by microorganisms represents an economical and effective approach for treating printing wastewater. In this study, a strain of Rhodobacter ruber KH-1 was isolated from the wastewater of a printing plant in Tai’an, Shandong Province, which was capable of utilizing BTEX (benzene, toluene, ethylbenzene, xylene) or pyridine individually as the sole carbon source for growth. Within 72 h, strain KH-1 completely degraded 80 mg/L of benzene, 40 mg/L of toluene, 50 mg/L of ethylbenzene, 40 mg/L of xylene, or 40 mg/L of pyridine in the culture medium. Salt tolerance tests indicated that strain KH-1 could grow normally within a salinity range of 0%–5%, and maintained its pollutant degradation rate at 3% salinity. Through genomic sequencing and homologous gene comparison, 11 genes have been identified as potentially involved in the degradation of pyridine and BTEX. Furthermore, the application of KH-1 in the bioremediation of real printing wastewater significantly reduced the levels of COD, benzene, toluene, pyridine, and other organic compounds. This study enriches the microbial resources capable of simultaneously degrading BTEX and pyridine, and holds significant implications for the treatment of alkaline high-salinity printing wastewater. Multi-panel illustration of *Rhodococcus ruber* KH-1, biodegradation data, wastewater treatment, and pollutant pathways.The figure includes panels depicting a scanning electron micrograph of *Rhodococcus ruber* KH-1, graphs showing biodegradation rates for pollutants (Benzene, Toluene, Ethylbenzene, Xylene, Pyridine) over time, and a wastewater treatment facility along with bar charts of COD removal efficiency. The schematic below highlights biodegradation pathways for pollutants, showing enzymatic breakdown into intermediates leading to the TCA cycle and final products CO2 and H2O. A strain of salt-tolerant Rhodococcus ruber was isolated from printing wastewater.This strain demonstrates significant tolerance to alkaline conditions.The strain is capable of utilizing BTEX or pyridine as a carbon source for growth.Genomic analysis reveals pollutant degradation pathways in this strain.The strain can efficiently degrade various organic pollutants in real printing wastewater. A strain of salt-tolerant Rhodococcus ruber was isolated from printing wastewater. This strain demonstrates significant tolerance to alkaline conditions. The strain is capable of utilizing BTEX or pyridine as a carbon source for growth. Genomic analysis reveals pollutant degradation pathways in this strain. The strain can efficiently degrade various organic pollutants in real printing wastewater.