Biodegradation of deltamethrin and its hydrolysis product 3-phenoxybenzaldehyde by a newly isolated Streptomyces aureus strain HP-S-01

A newly isolated actinomycete strain HP-S-01 from activated sludge could effectively degrade deltamethrin and its major hydrolysis product 3-phenoxybenzaldehyde. Based on the morphological, cultural, physio-biochemical characteristics, and 16S rDNA sequence analysis, strain HP-S-01 was identified as Streptomyces aureus. Strain HP-S-01 was also found highly efficient in degrading cyfluthrin, bifenthrin, fenvalerate, fenpropathrin, permethrin, and cypermethrin. Strain HP-S-01 rapidly degraded deltamethrin without a lag phase over a wide range of temperature (18~38°C) and pH (5~10), and metabolized to produce α-hydroxy-3-phenoxy-benzeneacetonitrile and 3-phenoxybenzaldehyde by hydrolysis of the carboxylester linkage. The 3-phenoxybenzaldehyde was further oxidized to form 2-hydroxy-4-methoxy benzophenone resulting in its detoxification. No persistent accumulative product was detected by gas chromatography-mass spectrometry (GC/MS) analysis. Response surface methodology was used to optimize degradation conditions. Strain HP-S-01 completely removed 50~300 mg L⁻¹ deltamethrin within 7 days under the optimal degradation conditions. Furthermore, the biodegradation kinetics corresponded with the first-order model. Therefore, strain HP-S-01 is suitable for the efficient and rapid bioremediation of pyrethroid-contaminated environment.