Laboratory evaluation of bacterial strains and their consortium for bioremediation of soils contaminated with obsolete pesticides

The aim of this study was to evaluate indigenous bacterial strains and their consortium for laboratory bioremediation of soil contaminated with obsolete organochlorine pesticides. Soil samples were collected from an abandoned pesticide warehouse in Zhany-Zher, Kyrgyzstan, and five isolates, JJ-1, JJ-2, JJ-3, JJ-6 and JJ-7, were selected. The 90-day experiment included individual strain treatments and a bacterial consortium. Treatment efficiency was assessed by cultivable microbial abundance, cellulose decomposition, spectrophotometric indicators of microbial metabolic activity and GC-MS determination of residual 4.4’-dichlorodiphenyldichloroethane (4.4’-DDD). The bacterial consortium produced the greatest increase in cultivable microorganisms, reaching (6.5 ± 0.5)×104 CFU/g compared with (2.6 ± 0.2)×104 CFU/g in the contaminated control. Among individual strains, JJ-1 and JJ-3 showed the highest microbial counts, reaching (4.3 ± 0.4)×104 CFU/g. Cellulose decomposition was most pronounced in the JJ-1 and JJ-2 treatments, exceeding 70%, while the consortium demonstrated moderate cellulose-associated activity. The concentration of 4.4’-DDD reduced from 0.021 ± 0.002 mg/kg to 0.008 mg/kg, corresponding to a 61.9% reduction. Individual strains showed lower reduction efficiency, with JJ-1 and JJ-3 reaching residual concentrations of 0.016 mg/kg. The results indicate that indigenous bacterial isolates, especially when applied as a consortium, can increase microbial abundance, support cellulose-associated microbial activity and reduce residual 4.4’-DDD in pesticide-contaminated soil under laboratory conditions.