Insights into the role of hexa-bacterial consortium for bioremediation of soil contaminated with chlorantraniliprole

Abstract

This study evaluates the efficacy of discrete bacterial consortia in bioremediating sandy loamy soil deliberately contaminated with 20 mg/kg of chlorantraniliprole (CAP). It monitors alterations in total bacterial populations and CO₂ emissions, tracking residual CAP levels through UV scanning and HPLC analysis. Six active bacterial degraders (four Bacillus strains (B. subtilis subsp. subtilis AZFS3, B. pumilus AZFS5, B. mojavensis AZFS15, and B. paramycoides AZFS18), one Alcaligenes strain (A. aquatilis KZFS11), and one Pseudomonas strain (P. aeruginosa KZFS4)) were used in single or combined preparations and grown on trypticase soy broth for 24 h at 30 °C before preparing the inoculants and adjusting the bacterial cell count to 10⁷ CFU/dwt g soil. The bacterial consortia were added to the CAP-contaminated soil and incubated for 20 days at 30 °C. The di-, tetra-, and hexa-bacterial consortia recorded the highest levels of viable bacteria, reaching their peak after 3 to 11 days of incubation. Then, they declined to the minimum levels at the end of the 20 days, which coincided with their complete removal of CAP from the soil. At the end of the incubation period (20 days), the CAP was mainly biodegraded, scoring biodegradation rates of 90.05%, 93.65%, and 98.65% for T3, T4, and T5, respectively. This concurred with the highest average CO₂ production. Based on the results of the HPLC analysis, the hexa-bacterial consortium T5 demonstrated the highest rate of CAP biodegradation (99.33%) after a 20-day incubation period, resulting in the lowest residual level of CAP in the soil (0.67%). Bioinformatic analysis predicted that the CAP biodegradation pathway reached CO₂ and H₂O. Under optimized conditions, the hexa-bacteria consortium is the most effective CAP biodegraded and is recommended as an eco-friendly treatment for eliminating CAP pollution in the field.