###### Abstract  
Microbial degradation has been considered as a rapid, green, and cost-effective technique to reduce insecticide pullutions in a contaminated environment. However, the instability and low efficacy of non-indigenous microorganisms hampers their further exploitation when being introduced into a real environmental matrix. In order to overcome the restriction that these functional microorganisms are under, we investigated the optimal conditions to improve the pyrethroid-degrading ability of one previously isolated bacterium _Bacillus cereus_ BCC01, where 9.6% of the culture suspension (with cell density adjusted to OD\({}_{600}\) = 0.6) was inoculated into 50 mL media and cultivated at pH 8 and 30 \({}^{\circ}\)C, and its metabolic pathway was illuminated by analyzing the main metabolites via gas chromatography mass spectrometry (GC-MS). Most importantly, a key pyrethroid-hydrolyzing carboxylase gene _estA_ was identified from the genomic library of strain BCC01, and then expressed in _Escherichia coli_ BL21 (DE3). After purification, the recombinant protein EstA remained soluble, displaying high degrading activity against different pyrethroids and favorable stability over a wide range of temperatures (from 15 \({}^{\circ}\)C to 50 \({}^{\circ}\)C) and pH values (6.5-9). Therefore, the EstA-associated biodegradation of pyrethroids was determined, which could provide novel insights to facilitate the practical application of _B. cereus_ BCC01 in the microbial detoxification of pyrethroid contamination. Keywords:pyrethroids; biodegradation; hydrolyzing carboxylase; heterologous expression; metabolic pathway +
Footnote †: journal: Applied Soft  
signaling in excitable cells. As reported, pyrethroids display negligible acute toxicity to mammals (the LD50 in rats is at 2000 mg/kg), but these compounds are highly toxic to target pests, including Lepidoptera (_Spodoptera litura_ [PERSON], _Spodoptera exigua_ [PERSON], and _Hellula undalis_ [PERSON]) and Diptera (_Liriomyza trifolini_ [PERSON] and _Melanagromyza sojae_ [PERSON]) (the average of LD50 is at 0.45 mg/kg) [4; 5; 6]. Commercial pyrethroids are mainly applied to control pests in agricultural crops and domestic health. However, they can easily be adsorbed by soil particles and transported via surface runoff, leaching, ground water, and wind drift, thereby causing agricultural nonpoint pollution [7; 8]. In addition, their high hydrophobicity and persistence due to continuous input may cause residual pollutions in sediment and other ecosystems, posing long-term exposure concerns to non-target organisms via bioaccumulation in food chain [9; 10]. Most importantly, increasing evidence alarmed the potential neurotoxicity of pyrethroids towards bees and fish, in addition to potential threats to influence reproduction in mammals [11; 12; 13], requiring effective techniques to remove pyrethroid contaminations to guarantee environmental safety [14]. In recent decades, a myriad of simple and eco-friendly methods have emerged for cleaning up contaminated environments by employing microorganisms' catalytic ability of hazardous xenobiotic. This approach, known as bioremediation, is generally considered to be less invasive and more restorative of soil functions in removing contaminants from the environment compared to conventional physicochemical methods [15]. As reported, numerous microorganism species have been identified as able to degrade pyrethroid insecticides in polluted soils, including _Pseudomonas aeruginosa_[16], _Steotrophomonas_ sp. [17], and _Serratia marcscens_, etc. [18]. However, the degradation performance of these microorganisms is restricted by many factors, including temperature, pH, nutritional conditions, and the impacts of indigenous flora. Therefore, understanding the mechanism that drives the microbial degradation is essential to improve bioremediation techniques.