Accumulation And Degradation Of Pesticide Residues In Pleurotus Ostreatus And Its Influence By Enzymes

China is rich in varieties of edible fungi,and its output ranks first in the world.However,pesticide residue problems occur frequently,and the study of their residue laws is weak.This study investigated the dynamic accumulation degradation of dimethoate,acetamiprid,Lambda-cyhalothrin and carbendazim in Pleurotus ostreatus liquid culture,and analyzed the degradation effect of edible fungus crude enzyme solution and laccase on pesticides.The purpose is to provide technical support for deep research on pesticide residue accumulationmechanism in edible fungi and potential pesticide contamination degradation by mushroom enzymes.The research results are as follows:?1?Established detection methods for dimethoate,acetamiprid,lambda-cyhalothrin,and carbendazim in two matrices of Pleurotus ostreatus mycelium and culture fluid,and the average recovery of four pesticides in mycelium is 82.3%?102.2%,the relative standard deviation is 1.3?7.8,the average recovery in the culture medium is 81.9%?103.2%,and the relative standard deviation is 1.9?7.2.?2?Liquid culture method was used to investigate the enrichment and degradation behavior of four pesticides during the growth of Pleurotus ostreatus.At a concentration of 5 mg·kg^-1of dimethoate,2 mg·kg^-1of acetamiprid,25 mg·kg^-1of Lambda-cyhalothrin,and 10 mg·kg^-1of carbendazim,The four pesticides were enriched to varying degrees,and the residual amounts showed a trend of first adsorption and then degradation,reaching the highest points of accumulation at 24 h,72 h,16 h,and 120 h,respectively,and the adsorption amount is 3.55 mg·kg^-1?1.02 mg·kg^-1?192.59 mg·kg^-1?3.54 mg·kg^-1.The pesticide adsorption rate from high to low is:Acetamiprid>Dimethoate>lambda-cyhalothrin>Carbendazim.The accumulation dynamics of four pesticides in Pleurotus ostreatus mycelium proved to be the behavior of simultaneous adsorption and degradation.The accumulation dynamics in Pleurotus ostreatus mycelia complies with the equation proposed in this experiment:Rt=Re(1-e^-a*t)e^-d*t.?3?The dynamic degradation behaviors of four pesticides in Pleurotus ostreatus culture medium were studied,and the results showed that the degradation trends of four pesticides in culture all accorded with the first-order kinetic model.After 19 days of dimethoate and acetamiprid culture,the residual amounts in the culture solution were1.51 mg·kg^-1and 0.79 mg·kg^-1,respectively.After 15 days of cultivation of Lambda-cyhalothrin and carbendazim,the residual amounts of the culture medium were0.24 mg·kg^-1and 0.86 mg·kg^-1,respectively,and the degradation half-life were 2.93 d,4.38 d,11.83 d,and 14.01 d.The degradation rate of pesticides in the culture medium from high to low was:Lambda-cyhalothrin>carbendazim>dimethoate>acetamiprid.At 2 h,1 d,3 d,5 d,7 d,and 10 d after dosing,the degradation rate of pesticides in the culture solution after sterilization was significantly lower than that in the unsterilized culture solution.Proved that the culture medium has a certain degradation effect on the four pesticides.?4?Laccase will be produced during the liquid culture of Pleurotus ostreatus.Before and after adding the four pesticides of dimethoate,acetamiprid,lambda-cyhalothrin and carbendazim,the laccase activity increased first and then decreased,and the peak of activity was reached on the 3rd day after the pesticide was added?10th day of culture time?,and the laccase activities were 1156.05 U·m L^-1?1138.47 U·m L^-1?727.7 U·m L^-1and 762.91 U·m L^-1.The addition of pesticides will inhibit the laccase activity.Dimethoate,acetamiprid,and carbendazim have the strongest inhibitory effect on the 3rd day after dosing,and lambda-cyhalothrin have the strongest inhibitory effect on the 7th day after dosing.At 1 h and 4 h,in systems containing 0 m L,5 m L,10 m L,25 m L,and 50 m L of crude enzyme solution with different concentrations,the higher the crude enzyme solution content,the higher the laccase activity,and the more the degradation rate of pesticides high.With the increase of time,the degradation rate of pesticides increases,and the degradation rate of pesticides?y?and laccase activity?x?conform to the Exp Dec1 type function:y=A₁*exp?-x/t₁?+y₀,four kinds of pesticide degradation rates Positively correlated with laccase activity in the reaction system.The addition of metal ions will affect the laccase activity.The relative enzyme activity of laccase under 1mM Cu²⁺treatment is 106.61%,and the relative activity of laccase under 5 mM Fe³⁺treatment is only 10.29%.This will simultaneously promote and inhibit the degradation rate of the four pesticides.The degradation effect of laccase activity on four pesticides was proved.