Unveiling the hydrolase Oph2876 mediated chlorpyrifos degradation mechanism in Pseudomonas nitroreducens and its potential for environmental bioremediation

Elucidating the kinetics and mechanisms of tetramethrin biodegradation by the fungal strain Neocosmospora sp. AF3

Tetramethrin is a common pyrethroid insecticide, but there is limited knowledge about its degradation kinetics and mechanisms. In this study, a novel fungal strain, Neocosmospora sp. AF3, was obtained from pesticide-contaminated fields and was shown to be highly effective for degrading tetramethrin and other widely used pyrethroids. The AF3 strain completely removed 10 mg/L of tetramethrin from mineral salt medium in 9 days. The first-order kinetic analysis indicated that the degradation rate constant of the AF3 strain on 50 mg/L tetramethrin was 0.2835 d-1 (per day), and the half-life was 2.45 days. A response surface model analysis showed that the optimal degradation conditions for the AF3 strain are a temperature of 33.37 ℃, pH of 7.97, and inoculation amount of 0.22 g/L dry weight. The Andrews nonlinear fitting results suggested that the optimal concentration of tetramethrin metabolized by the AF3 strain is 12.6073 mg/L, and the qmax, Ki, and Ks values were 0.9919 d-1, 20.1873 mg/L, and 7.8735 mg/L, respectively. The gas chromatography-mass spectrometry (GC-MS) analysis indicated that N-hydroxymethyl-3,4,5,6-tetrahydrophthalimide, chrysanthemic acid and tetrahydrophthalimide are the main intermediates involved in the metabolism of tetramethrin by the AF3 strain. Furthermore, this strain was shown to effectively degrade other pyrethroid pesticides including permethrin, beta-cypermethrin, chlorempenthrin, fenvalerate, D-cyphenothrin, bifenthrin, meperfluthrin, cyfluthrin, and deltamethrin within a short period, suggesting that Neocosmospora sp. AF3 can play an important role in the remediation of pyrethroid contamination. Taken together, these results shed a new light on uncovering the degradation mechanisms of tetramethrin and present useful agents for developing relevant pyrethroid bioremediation strategies.

Laccase immobilized on magnetic nanoparticles for the degradation of imidacloprid: Based on multi-spectroscopy and molecular docking

As a typical class of environmental endocrine disruptors, imidacloprid (IMI) poses a potential threat to the sustainable survival and reproduction of living beings and human beings. Consequently, it is crucial to establish an efficient degradation method to remove imidacloprid from the environment. The present study aimed to investigate the immobilized laccase for the detoxification of imidacloprid via multi-spectroscopy and molecular docking. Herein, laccase was immobilized on magnetic nanoparticles (NiFe2O4 NPs) using a novel immobilization technique based on glutaraldehyde cross-linking polymerization. A single factor experiment approach was used to optimize the immobilization conditions, which included temperature, pH, enzyme concentration, and reaction time. Notably, the optimal condition was determined as 50℃, pH 4, laccase concentration of 1.0 mg/mL and 1.5 h. Based on the immobilization conditions, the degradation efficiency of immobilized laccase was 41.92 % after 24 h. Following eight degradations, the immobilized laccase's relative activity stayed at 34.09 % of its initial activity, demonstrating exceptional operational stability and reusability. Moreover, the binding free energy between imidacloprid and laccase was calculated on the basis of molecular docking, as -7.2 kcal/mol. This study provides experimental techniques and theoretical references for the biological digestion of hazardous pesticide residues in the environment. In addition, this study improved the shortcomings of free laccase, provided an environmentally friendly and efficient method for the degradation of imidacloprid.

Construction of P450 scaffold biocatalysts for the biodegradation of five chloroanilines

Chloroanilines represent a class of persistent and highly toxic environmental pollutants, posing significant challenges for green remediation strategies. While P450BM3 monooxygenases are renowned for their ability to catalyze the monooxidation of inert C-H bonds, costly NAD(P)H and complex electron transport systems required for P450BM3 catalysis limit their practical applications. This study pioneers the development of innovative artificial biocatalysts by strategically engineering the active site of P450BM3. Specifically, the substitution of the highly conserved threonine 268 with aspartic acid effectively induces peroxygenase activity, allowing for enhanced catalytic efficiency. Remarkably, the engineered P450BM3 mutants achieved degradation rates of 98.38-99.18 % for five chloroanilines (4-chloroaniline, 2-chloroaniline, 2,4-dichloroaniline, 3,4-dichloroaniline, and 3,5-dichloroaniline) in just 10-15 min, all without the need for NAD(P)H or dual-functional small molecules. Comprehensive degradation mechanism analysis via UPLC-MS corroborated the remarkable performance of these biocatalysts. This research not only demonstrates a novel approach for engineering P450 monooxygenases to exhibit peroxygenase activity but also significantly broadens their potential applications in synthetic chemistry and synthetic biology, paving the way for greener and more sustainable remediation technologies.

Unraveling the degradation mechanism of multiple pyrethroid insecticides by Pseudomonas aeruginosa and its environmental bioremediation potential

Extensive use of pyrethroid insecticides poses significant risks to both ecological ecosystems and human beings. Herein, Pseudomonas aeruginosa PAO1 exhibited exceptional degradation capabilities towards a range of pyrethroid family insecticides including etofenprox, bifenthrin, tetramethrin, D-cypermethrin, allethrin, and permethrin, with a degradation efficiency reaching over 84 % within 36 h (50 mg·L-1). Strain PAO1 demonstrated effective soil bioremediation by removing etofenprox across different concentrations (25-100 mg·kg-1), with a degradation efficiency over 77 % within 15 days. Additionally, 16S rDNA high-throughput sequencing analysis revealed that introduction of strain PAO1 and etofenprox had a notable impact on the soil microbial community. Strain PAO1 displayed a synergistic effect with local degrading bacteria or flora to degrade etofenprox. UPLC-MS/MS analysis identified 2-(4-ethoxyphenyl) propan-2-ol and 3-phenoxybenzoic acid as the major metabolites of etofenprox biodegradation. A new esterase gene (estA) containing conserved motif (GDSL) and catalytic triad (Ser38, Asp310 and His313) was cloned from strain PAO1. Enzyme activity and gene knockout experiments confirmed the pivotal role of estA in pyrethroid biodegradation. The findings from this study shed a new light on elucidating the degradation mechanism of P. aeruginosa PAO1 and present a useful agent for development of effective pyrethroid bioremediation strategies.