Production Characteristics Of White Rot Fungi EPS And SMP Under Pb/Cd Stress And Removal Of Pb/Cd By EPS

The white rot fungus mycelium has strong adsorption to heavy metals,and its extracellular polymeric substances(EPS)is an important component of the extracellular defense system.At present,the role of EPS in removing heavy metals is not completely clear,but soluble microbial products(SMP)and EPS are produced by microorganisms,and the main components contain polysaccharides,proteins and the like.Therefore,this paper studied the production characteristics of EPS and SMP of white rot fungi under heavy metal stress and the removal of Pb/Cd by EPS.In this study,the lead and cadmium removal experiment was carried out using the white rot fungus model strain Phanerochaete chrysosporium,and the extraction method of EPS from white rot fungus was optimized,and the production of EPS and SMP under Pb/Cd stress was optimized,as well as the removal of Pb/Cd by EPS,the specific research results are as follows:(1)Part 1 studied the optimization of extraction methods for white rot fungi EPS.The effects of EDTA-2Na method,ultrasonic centrifugation method and high-speed centrifugation method on extracting EPS of Phanerochaete chrysosporium were studied by experiments.When the concentration of EDTA-2Na was 2% and the centrifugal speed was 10000 rpm,the protein concentration reached the maximum 18.439 mg/L.The concentration of polysaccharide in the EPS solution extracted under ultrasonic treatment for 10 min and 12000 rpm was the highest,reaching 613.638 mg/L.(2)Part 2 studies the production characteristics of EPS and SMP under Pb/Cd stress.In the Cd-containing experimental group,the lower concentration of Cd had a significant inhibitory effect on EPS yield,and the higher concentration of Cd had a weaker inhibitory effect on EPS yield.The concentration of polysaccharide in SMP increased with the increase of culture time.In the Pb-containing experimental group,the yield of EPS polysaccharide increased with the increase of culture time.The protein yield of EPS increased at different times under Pb stress.On the 7th day of culture,the higher concentration of heavy metal stress,the higher polysaccharide concentration in SMP.(3)Part 3 studied the removal of Pb/Cd by EPS.The higher the Cd stress concentration,the higher the Cd removal per unit mass EPS;the negative correlation between Cd removal and protein content in EPS,and the positive correlation with polysaccharide content;in the 100 mg/L Cd experimental group after extracted EPS,the Cd mass fraction in the surface components of the cells decreased from 5.14% to 4.42%.In the Pb-removed experimental group,the Pb removal per unit mass of EPS was basically same under different Pb concentrations;there was a positive correlation between Cd removal and protein content in EPS,and a negative correlation with polysaccharide content;in the 400 mg/L Pb experiment group after extracted EPS,the Pb mass fraction in the surface components decreased from 16.22% to 2.16%.Through the above studies,it was determined that ultrasonic polymerization was used to extract EPS in subsequent experiments.The EPS of Phanerochaete chrysosporium had a removal effect on Pb/Cd,and the Pb/Cd content on the surface of the cells decreased after extracted EPS,which further proved that EPS plays a certain role in the removal process of Cd/Pb.There was a positive correlation between Cd removal and polysaccharide content in EPS.There was a positive correlation between Pb removal and protein content in EPS.After extracted EPS,the Pb mass fraction on the surface of the cells decreased significantly,while the surface Cd mass fraction decreased is not obvious,which indicates that there are differences in the removal mechanism of Pb and Cd by Phanerochaete chrysosporium,which needs further improvement.