Yield And Composition Of Extracellular Polymeric Substances （EPS） By White-rot Fungi And Mechanism Of Its Biosorption Of Pb²⁺

Because white-rot fungi have the unique ability in the degradation thexenobiotics, making clear its interactions with heavy metals is becoming a newhotspot. During heavy metal wastewater treating process, the extracellularpolymeric substances on the cell surfaces, which contained sugar and protein,playe an important roleI on the ions absorption. There was no report about the EPSyield, composition and micromechanisms of Pb²⁺biosorption. In this article,extracellular biosorption capacity were studied under different culture mediums inorder to get the most appropriate medium and EPS extraction methods. The yieldand composition of EPS were analysised. Their micro mechanisms on leadabsorption were investigated using SEM and FTIR technologies.More white-rot fungi biomass can be got in patato culture medium than others.The growth of biomass was affected by Pb²⁺. Under patato medium, the best culturetime was78h and the adsorption efficiency and adsorption capacity were60%and16.23mg/g. Under glucose medium, the values were37%and119.35mg/grespectively. The extracellular biosorption capacity was little with two mediums.Dry cell weight and EPS yield were determined by optimizing the culturemedium and EPS extraction methods. Results showed that the EPS secretion hadclose links with the growth of white-rot fungi. At113h, the maximum yield of EPSand dry cell weight were125.5mg/L and1.612g/L respectively, which containedmore than78%of sugar and protein.The control test results after EPS extraction displayed a decrease ofbiosorption capacity of Pb²⁺among2.12-7.73mg/g. The results of environmentscanning electron microscope （ESEM） showed that the cell walls of white-rot fungihad remarkable changes after EPS extraction. After Pb²⁺biosorption, many micronwell-regulated Pb-protein ball particles were observed which adhered to thesurface of cell wall. Results of Fourier transform infrared spectroscopy （FTIR） onunloaded and lead-loaded cells demonstrated that hydroxyl group on cell wallsurface seemed to be the main binding sites.All studies above indicated that EPS of white-rot fungi can be obtainedthrough appropriate culture conditions and extraction methods. The white-rotfungi can increase the tolerance to Pb²⁺by formation of micron particles with the EPS which contained protein. It was very useful for further study on heavy metalbiosorption mechanism.