Eco-efficient Pseudomonas-Rhodococcus combination technique to boost the BTEX degradation

This study investigated the aerobic biodegradation potential of two novel indigenous bacterial strains, Pseudomonas aeruginosa DUT-Pa and Rhodococcus erythropolis DUT-Re, utilizing benzene, toluene, ethylbenzene, and o-xylene (BTEX) as the sole carbon source. The optimal metabolic activity for both strains was identified at neutral pH (7.0) and mesophilic conditions (30 °C), establishing a critical baseline for enhancing bioremediation protocols. Biochemical oxygen demand (BOD) analysis revealed a direct correlation between the substrate concentration (up to 400 mg/L) and microbial respiratory activity. Dissolved oxygen (DO) depletion from 7.77 mg/L (pre-experiment) to 2.97 mg/L (DUT-Pa) and 2.15 mg/L (DUT-Re) further confirmed the oxygen-dependent degradation. In the gas phase, the highest degradation rate was recorded for benzene, with 98.43, 97.34, and 98.91% by DUT-Pa, DUT-Re, and mixed bacteria, respectively. Meanwhile, the liquid phase demonstrated superior toluene degradation efficiency by DUT-Pa, DUT-Re, and mixed bacteria with 91.99, 83.54, and 93.27% respectively. Bacterial combinations enhanced BTEX degradation, achieving the shortest half-lives and the highest degradation rate constants. Meanwhile, the SOD (325 U/mL) level and MDA (1.5 to 2.59 nmol/g) increased in the mixed system. This study demonstrates that an additive effect of DUT-Pa and DUT-Re combination promotes efficient, complete degradation of BTEX and offers a scalable, eco-friendly solution based on strain-specific cooperative microbial dynamics.