Pesticide residue levels in green beans cultivated in Souss Masa valley (Morocco) after multiple applications of bifenthrin and λ-cyhalothrin

Lambda-cyhalothrin alters locomotion, mood and memory abilities in Swiss mice

Lambda-cyhalothrin (LCT) is a type II pyrethroid widely used in agriculture for plant protection against pests. However, pyrethroids represents a risk for rural female farmworkers, and few studies addressed LCT-behavioural alterations in mice. The present study evaluates the effect of LCT on behaviour of eight weeks aged female mice. Mice were divided into three groups including treated mice that received through gavage (i) 0.5 mg/kg bw and (ii) 2 mg/kg of LCT dissolved in corn oil, and (iii) the vehicle controls. Behavioural tests assess the locomotor activity using open field test, the anxiety by the dark-light box test, the learning memory with novel object recognition test, the memory retention by the elevated plus maze test, and the spatial working memory using the Y-maze test. Subacute treatment with low doses of LCT decreases total distance travelled, induces anxiogenic effect by reducing the time spent in the enlightened compartment, alters memory retention by increasing the latency time, and also affects learning memory by reducing the recognition index parameter. However, LCT does not significantly alter spatial working memory. In conclusion, LCT-treated female mice show an alteration in locomotor activity, mood state and memory abilities probably related to oxidative stress and altered neurotransmission.

Residual levels and dietary risk assessment of bifenthrin and dinotefuran and its major metabolites in open wheat field conditions

To evaluate the residual levels of bifenthrin and dinotefuran, a modified quick, easy, cheap, effective, rugged, and safe (QuEChERS) and high-performance liquid chromatography-tandem mass spectrometry method for simultaneous detection of bifenthrin and dinotefuran and its major metabolites in wheat was developed and validated. Dietary risk assessments were further performed based on the relevant residual data from 12 wheat fields, toxicology data and dietary patterns. In wheat grain and straw, the recoveries of all analytes ranged from 77 to 102% with the relative standard deviation <9.7% and the limit of quantitation 0.05 mg kg^-1 . The highest terminal residue of bifenthrin in wheat grain was 0.069 mg kg^-1 and dinotefuran was 0.34 mg kg^-1 . Residual concentrations of bifenthrin and dinotefuran decreased to <0.05 and 0.15 mg kg^-1 at 21 days (pre-harvest interval), respectively. The chronic risk quotient ranged from 6.4 to 62.7% and the acute risk quotient varied from 0.38 to 17.73%. The chronic and acute dietary risks caused by the terminal residues of the two insecticides were negligible for Chinese populations. The recommended pre-harvest interval was proposed to ensure safe wheat consumption. These data could provide a scientific reference to establish the Chinese maximum residue limit of dinotefuran in wheat.

Facile One-Pot Immobilization of a Novel Thermostable Carboxylesterase from Geobacillus uzenensis for Continuous Pesticide Degradation in a Packed-Bed Column Reactor

The novel carboxylesterase gene (est741) was cloned from Geobacillus uzenensis. The optimal pH and temperature of Est741 were 8.0 and 50 °C. Through site-directed mutation, the optimum temperature of the mutant M160K(EstM160K) was increased from 50 to 60 °C, and showed enhanced T1/2 of 2.5 h at 70 °C in comparison to the wild type (1.3 h). EstM160K was successfully expressed Pichia pastoris and EstM160K fermentation broth was directly immobilized on epoxy-functionalized supports via a one-pot strategy to obtain the immobilized enzyme lx-EstM160K. Additionally, lx-EstM160K showed enhanced T1/2 of 36.8 h at 70 °C in comparison to free enzyme. lx-EstM160K could degrade various pyrethroid pesticides. After 40 min reaction with 50 U of the lx-EstM160K, the malathion removal was 95.8% with a malathion concentration of 20 mg/L. When 2.5 g lx-EstM160K was added to the 10 mL column reactor with the concentration of bifenthrin was 500 mg/L and the transfer rate of the pump was 0.7 mL/min, the degradation rate of lx-EstM160K to bifenthrin was 90.4%. lx-EstM160K exhibited high operational stability and maintained 72% initial activity after ten batches of continuous reaction for bifenthrin pesticide biodegradation.