Isomerization and biodegradation of beta-cypermethrin by Pseudomonas aeruginosa CH7 with biosurfactant production

Pseudomonas aeruginosa CH7, isolated from activated sludge, was able not only to isomerize and degrade beta-cypermethrin but also to utilize it as the sole source of carbon and energy for growth and produce biosurfactant. The strain effectively degraded beta-cypermethrin with inocula biomass of 0.1-0.2 g L(-1) at 25-35°C, pH 6-9, and a final concentration of beta-cypermethrin 25-900 mg L(-1). Via response surface methodology analysis, we found the optimal condition was 29.4°C, pH 7.0, and inocula biomass of 0.15 g L(-1); under these conditions, about 90% of the beta-cypermethrin could be degraded within 12 days. Noticeably, biosurfactant was detected in the MSM culture of strain CH7, suggesting that the biosurfactant (rhamnolipid) could potentially enhance the degradation of beta-cypermethrin by promoting the dissolution, adsorption, and absorption of the hydrophobic compounds. Therefore, CH7 may serve as a promising strain in the bioremediation of wastewater and soil polluted by beta-cypermethrin.