Heavy Metals Removal By Filamentous Fungus Pleurotus Ostreatus And Its Tolerance Mechanisms

In recent years,with the rapid development of China's economy,the problem of environmental soil pollution is becoming more and more serious at the same time.According to the Ministry of Land and Resources,about 1/10 of the national arable land is polluted,mostly by heavy metal pollution.The heavy metal in soil by dust get into the atmosphere,and can also be absorbed passively by plants and enter the food chain,thus to be a hazard to human health.However,at present there have been no ideal agricultural repair methods for heavy metal pollution of soil.Many macro fungi are capable of taking enrichment for heavy metal,and it is expected to become a new method for repair.However,its tolerance and absorptive capacity to metal are limited.This study aims to further improve its tolerance ability by domesticated strains of fungi pleurotus ostreatus,which are domesticated under the cultivated conditions in concentration of1500 mg/L Pb²⁺,250 mg/L Cr³⁺ and 50 mg/L Cd²⁺ respectively and they can still grow.Shaking research after the domestication of fungi pleurotus ostreatus to research tolerance mechanism,found Pb²⁺and Cr³⁺ caused P.ostreatus soluble protein decreased,while Cd²⁺ Stress the P.ostreatus soluble protein increased.Three heavy metals stress strain fungi SOD,CAT and POD activity increased first and then decreased.Three heavy metals induce P.ostreatus significantly increased H2O2 and MDA content,suggesting that reactive oxygen species-mediated membrane lipid peroxidation produce MDA,oxidative damage on fungi.Also found P.ostreatus GSH content also increased significantly,indicating that GSH helped alleviate heavy metal poisoning cells,which pellagra Cd²⁺ under the action of the ear GSH content increased most significantly,which is 25?g/g.Shake flask experiments showed P.ostreatus liquid medium has a certain ability to remove heavy metals,heavy metal removal rate decline with increasing concentration.Wherein,when Pb²⁺Stress at a concentration of 100 200mg/L,the strain of its removal rate reached 100%,when concentrations of up to 1500 mg / L,the strain can still be removed 49.9%;for Cr³⁺,at a concentration of 50mg/L,its removal is maximum?68.5%?,at a concentration of 250mg/L,its removal rate is lowest?40.5%?;for Cd²⁺,when the concentration of 10 mg / L,the strain of its highest removal efficiency?79.4 %?,at a concentration of 50mg/L,the removal rate is lowest?47.4%?.Also found that the strain is mainly absorbed by intracellular and extracellular adsorption to achieve the removal of heavy metals.And intracellular and adsorption capacity with increasing average concentration of heavy metals increases.for Pb²⁺,intracellular and adsorption maximum at the concentration of 1500mg/L,the respectively 165mg/g and 31.94mg/g.For Cr³⁺,at a concentration of 250mg/L,the maximum intracellular and adsorption,respectively,3.94 mg / g and6.4mg / g.For Cd²⁺,when the concentration of 50mg/L,the maximum amount of intracellular and adsorption,respectively 1.8mg/g and 1.57mg/g.Through pot experiment found after domesticated strains have certain ability of enrichment of heavy metals in soil.Among them,the soil heavy metal concentration of 500 mg/kg,the capacity of its enrichment is 8.22 mg/kg;under the effect of EDTA with heavy metal absorption capacity was up to 124 mg/kg,and it was 14.1 times that of the control group.Therefore,macro fungi are expected to be used for repair of soil with heavy metal pollution in the future.