Distribution, characteristics of extracellular polymeric substances of Phanerochaete chrysosporium under lead ion stress and the influence on Pb removal

The distribution, characteristics of extracellular polymeric substances (EPS) of Phanerochaete chrysosporium under Pb(2+) stress and the influence on Pb removal were investigated. Polysaccharides was found to be the main composition in both soluble EPS (SEPS) and bounded EPS (BEPS). More polysaccharides and protein in BEPS were detected with the increased Pb(2+) concentration. The ratio of Pb amount distributed in BEPS to the total Pb removed by the fungal biomass gradually decreased from 91.66 to 61.27% in group with 50 mg/L of initial Pb(2+), but kept at about 35% or 25% in groups with higher Pb(2+). It implies that BEPS played a certain role in the lead removal process, and the role of BEPS was relatively more important in the removal of lower concentration of Pb(2+) and in the initial period of Pb removal. With FTIR analysis and Pb(2+) adsorption experiment, more effective functional groups and better Pb(2+) adsorption capacity was demonstrated in BEPS than in SEPS. SEM–EDS analysis demonstrated that part of Pb immobilized in BEPS was in the form of Pb precipitation. The increased molecular weight in SEPS and more polysaccharides in BEPS were probably beneficial for the adhesion of Pb precipitation.