Degradation And Accumulation Mechanisms Of Carbendazim And Fenvalerate In Pleurotus Ostreatus Fruits

There are few peticides registrated in edible fungus production in China.Actually a few pesticide were used in Pleurotus ostreatus production to control pest and disease and several has been detected in mushrooms and composts during investigation., and some exceed the standards of GB2763 such as carbendazim.In this paper mechanism of degradation and accumulation of carbendazim and fenvalerate were studied in Pleurotus ostreatus fruits, mycelium and substrates, to provide theoretical support for the risk assessment of carbendazim and fenvalerate in the Pleurotus ostreatus. The conclusion were drawn as following:(1) Established the carbendazim and fenvalerate residue detection methods in different matrix including pleurotus ostreatus, substrates, mycelium, culture. The samples were extracted by acetonitrile, puring by 50 mg PSA, 50 mg ODS and 150 mg anhydrous Mg SO4, using the UPLC-PDA, LC/MS/MS, GC/MS/MS to detection respectively. Add recovery rates were between 80.7 to 105.5, RSD were in the range of 0.5% to 10.7%.(2)Using culture medium containing medicine and medicated shake flask methods researched degradation accumulation characteristics about carbendazim and fenvalerate in Pleurotus ostreatusa and the process of liquid fermentation culture. 24-hour dynamic monitoring of carbendazim result showed little changes in the mycelium and culture. Results showed that In 20 mg/kg carbendazim adding, the residues of culture and accumulation of mycelium were 18.84, 0.7 mg/kg, 98 hours after were 5.11, 4.83 mg/kg respectively. Under the condition of 20 mg/kg adding, at 98 hours culture residuesand mycelium accumulation of carbendazim were reached the most value. Under fenvalerate dose in 0.2, 2, and 20 mg/kg, it can be rapidly degradated to 100% in 24 hours, accumulating to the most value on 9 hours. Under the dosing concentration of 2 mg/kg, in vitro mycelium, fenvalerate accumulation value most in occured in 2 to 3 hours. In Pleurotus ostreatus mycelium liquid fermentation process, accumulation of carbendazim meet pseudo-second adsorption kinetics model, while fenvalerate accumulation fitting was not batter than carbendazim. Degradation of carbendazim and fenvalerate in Pleurotus ostreatus fermented culture meet First order kinetics. Fenvalerate degradation rate in mycelium fermentation process were faster than in vitro. In the case of static, not inactivated vitro mycelium accumulation of fenvalerate were more than in the volatile situation and existed significant difference. There may be some composition that occurred in mushroom fermentation that can promote the degradation of fenvalerate. Edible fungus mycelium can almost accumulate all fenvalerate added in the culture, but different edible fungi to the degradation of fenvalerate were different.(3)At application rate of 0.1%, 0.3% effective ingredient in substrates, carbendazim residues accumulated in the first and last flush fruit bodies were 0.089 ~ 0.077 mg/kg and 0.533 ~ 0.485 mg/kg separately, whick were below 1 mg/kg, the EU maximum residue level standards. The accumulation ability of carbendazim in different parts of fruit body was different significantly with foot>stipe>full body>cap. The degradation of carbendazim in substrates followed one-order exponential equation, and different layer of the culture bag, mycelium growth and sterilization could affect the carbendazim degradation. In upper layer of the culture bag, carbendazim reduced more quickly with half- life of 33 d than in middle and bottom layer with half-life at 36.47 d and 63 d. Mycelium growth after inoculation of strains was beneficial to degradation of carbendazim in substrates because of the higher degradation rate than without inoculation. Sterilization of substrates at high pressure promoted the reduction of carbendazim residue effectively with degradation rate of 92.05% and 86.46%. However, the carbendazim kept almost stable in non-sterile substrates.(4)At application rate of 0.004%, 0.02% effective fenvalerate ingredient in substrates, fenvalerate residues accumulated in the first and last flush fruit bodies were not detected. Fenvalerate unfavorable accumulated in different part of Pleurotus ostreatus. The degradation of fenvalerate in substrates followed one-order exponential equation, and different layer of the culture bag, mycelium growth and sterilization could affect the carbendazim degradation. In upper layer of the culture bag, Fenvalerate reduced more lowly than in middle and bottom layer, Half-life were 36.474 d, 31.5d,28.875 and 40.765 d, 33 d, 27.72 d respectively. Mycelium growth after inoculation of strains was beneficial to degradation of Fenvalerate in substrates. But not for sterilization, fenvalerate degradation in substrates is faster than high pressure sterilization due to microbial degradation, Half-life were 86.625, 77 d and 115.5d, 173.25d.