The Research On Extraction Of White-rot Fungal Extracellular Polymer Substances And Its Adsorption Of Heavy Metal Cd

White rot fungi have been studied deeply in heavy metal wastewater treatment because of their strong adsorption capacity of heavy metals.The extracellular polymer on the surface of a microorganism was an important barrier to resist the toxicity of heavy metals.By chelation and immobilization,the biological harmful effects of heavy metals was changed to protect the microbodies from the toxicity of heavy metal ions.But so far,scholars in various countries have not studied comprehensively the characteristics and functions of white rot fungi on the surface extracellular polymeric substances?EPS?.Among them,the optimization of the extraction method of EPS was a problem to be solved;the traditional culture method was used to improve the biomass of white rot fungi,and the influence of culture conditions on the extracellular polymer of the mycelium was not clear;In addition,the study on the effect and influence factors of the adsorption of heavy metals on the extracellular polymers of white rot fungi was not comprehensive.Therefore,this paper took the model fungus of white rot fungus Phanerochaete chrysosporium as the research object,mainly from the above three research directions to carry out the experiment,the specific work and the research results are as follows:The first part was optimized the extraction method of extracellular polymeric substances from white rot fungi.Three kinds of more mild methods were extracted by EDTA-2Na,ultrasonic extraction and high speed centrifugation.The protein was determined by Coomassie brilliant blue method and the anthrone sulfuric acid method was used to determine polysaccharide.The experimental results showed that the extraction effect of three mild extraction methods had little difference,and the high speed centrifugation method was the most simple and can extract more.Extracellular polymeric substances,so 10000 rpm high speed centrifugation for subsequent experiments.In the second part,in order to improve the output of extracellular polymer,by changing the temperature,time,speed and inoculation amount in the culture process of Phanerochaete chrysosporium,the output of extracellular polymers under different culture conditions was compared,and the best culture conditions were obtained.In the process of culture,the output of EPS increased with the increase of temperature,and the best culture temperature was 40?.Speed was related to dissolved oxygen,the higher the rotational speed was,the more dissolved oxygen was,but the dissolved oxygen in water was certain.So the 100 rpm speed was most suitable.The best culture conditions were culture time of 5d and inoculation volume of 2 ml,and the highest yield of EPS was 228.15 mg/g.In the third part,firstly,the adsorption of extracellular polymers was indirectly verified,by comparing the adsorption of cadmium with the pre-and post-extraction of extracellular polymeric microspheres.Then the dialysis EPS was used for direct adsorption experiments,and the changes of dialysis time,dosage,pH and temperature were investigated to obtain better adsorption conditions for cadmium adsorption by Phanerochaete chrysosporium extracellular polymers:adsorption time At 12 h,the dosage of Cd²⁺/EPS was 4,the pH was 3,and the adsorption amount of extracellular polymer per unit mass was 130 mg/g at a temperature of 50°C.The above research indicated that the extraction method suitable for high speed centrifugation was a simple and efficient method for extracting extracellular polymeric substances.A large number of extracellular polymers can be obtained by optimizing the culture conditions to increase the production of extracellular polymers.Extracellular polymeric substances have good adsorption effect on heavy metal Cd²⁺,and their adsorption process is affected by adsorption conditions.This study can provide important reference for further research on the biosorption mechanism of heavy metals in white rot fungi.