Identification of Detoxification Esterase StrH Initiating Strobilurin Fungicides Degradation in Hyphomicrobium sp. DY-1

Strobilurin fungicides are widely used in agricultural production due to their broad-spectrum and fungal mitochondrial inhibitory activities. However, their massive application has detained the growth of eukaryotic algae and increased the collateral damage in freshwater systems, notably the harmful cyanobacterial blooms (HCBs). In this study, a strobilurin fungicide-degrading strain Hyphomicrobium sp. DY-1 was isolated and characterized successfully. Moreover, a novel esterase gene strH responsible for the de-esterification of strobilurin fungicides was cloned, and the enzymatic properties of StrH were studied. For trifloxystrobin, StrH displayed the maximum activity at 50°C and pH 7.0. The catalytic efficiency (kcat/Km) of StrH for different strobilurin fungicides were 196.32±2.30 μM−1·s−1 (trifloxystrobin), 4.64±0.05 μM−1·s−1 (picoxystrobin), 2.94±0.02 μM−1·s−1 (pyraclostrobin), and (2.41±0.19)×10−2 μM−1·s−1 (azoxystrobin). StrH catalyzed the de-esterification of a variety of strobilurin fungicides generating the corresponding parent acid to achieve the detoxification of strobilurin fungicides and relieve strobilurin fungicides growth inhibition on Chlorella. This research will provide insight into the microbial remediation of strobilurin fungicides-contaminated environments. IMPORTANCE Strobilurin fungicides have been widely acknowledged as an essential group of pesticides worldwide. So far, their residues and toxic effects on aquatic organisms have been reported in different parts of the world. Microbial degradation could eliminate xenobiotics from the environment. Therefore, the degradation of strobilurin fungicides by microorganisms has also been reported. However, little is known about the involvement of enzyme or gene in strobilurin fungicides degradation. In this study, a novel esterase gene strH responsible for the detoxification of strobilurin fungicides was cloned in the newly isolated strain Hyphomicrobium sp. DY-1. This degradation process detoxifies the strobilurin fungicides and relieves their growth inhibition on Chlorella.

Determination of Neonicotinoid Insecticides and their Metabolites, and Strobilurin Fungicides in Atmospheric Particles using Liquid Chromatography-Positive Electrospray Ionization-Tandem Mass Spectrometry

A liquid chromatography-tandem mass spectrometry method has been developed for the simultaneous determination of metabolites of neonicotinoid insecticides with neonicotinoid insecticides and strobilurin fungicides in the particle phase fraction of atmospheric samples. Pressurized solvent extraction was used to extract the target analytes from particles collected on glass fiber filters, followed by a C18 SPE cleanup step. Recoveries of 85.9 to 108.3% and relative standard deviation <13% were obtained for all analytes. The method detection limit for metabolites of neonicotinoid insecticides were 0.5-3 ng/ mL (air concentrations of 0.44-2.66 pg/m³). Matrix effects were compensated for using standard addition calibration for quantitation. This paper provides the first detection of desmethyl-thiamethoxam which coincided with higher concentrations of thiamethoxam in atmospheric particles. Other neonicotinoid insecticides and strobilurin fungicides detected in the particle phase in the atmosphere included acetamiprid, clothianidin, imidacloprid, azoxystrobin, kresoxim-methyl, pyraclostrobin, and trifloxystrobin. This research highlights the potential of not only neonicotinoid insecticides and strobilurin fungicides moving in the atmosphere in the particle phase, but also a metabolite of thiamethoxam (desmethyl-thiamethoxam) in a region with orchards and vineyards where foliar applications with air blast sprayers dominate.

Preparation of magnetic zeolitic imidazolate framework-8 for magnetic solid-phase extraction of strobilurin fungicides from environmental water samples.

In this paper, magnetic zeolitic imidazolate framework-8 composites were synthesized by the simple in-situ method and then firstly used as adsorbent in magnetic solid-phase extraction for extracting multiple strobilurin fungicides....