Research On Cd(â…¡) Enrichment And Its Mechanism Of Interaction With Phanerochaete Chrysosporium

Along with our country economic development gradually accelerated, all kindsof increasingly serious environmental pollution, organic, inorganic and heavy metalpollutants on the environment caused by pollution cannot be ignored. Because of theheavy metals with strong toxicity, wide spread, strong concealment and difficult torepair, thus it increased the difficulty of the field of environment protection for itstreatment. How to efficiently handle wastewater containing heavy metals has becomea hot research for scientists and environmental organizations. Phanerochaetechrysosporium (P. chrysosporium) can be efficient enrichment of heavy metals.Therefore, P. chrysosporium as absorbent in biological absorption method has beenwidely concerned. However, heavy metals are toxic to white-rot fungi when present inexcess. So white-rot fungi gradually form the defense mechanism to alleviate thetoxic injury.In this study, laboratory wastewater containing Cd2+simulated environmentalwastewater. The experiments studied the enrichment effect and mechanism of Cd2+toP. chrysosporium. At different initial Cd2+concentratons, the study determined theintracellular and extracellular Cd2+concentration of P. chrysosporium andcharacterized fungal hyphae by ESEM and EDS. The results showed that the cellwalls of P. chrysosporium could strongly enrich Cd2+and adsorption efficiencyincreased with increasing Cd2+concentration. P. chrysosporium can also accumulatetrace amount of Cd2+inside the cell, but its intracellular accumulation did not play amajor role and the surface compleaxtion adsorption was the main mechanism.In order to study the physiological effect of Cd2+toxicity on P. chrysosporiumand resistance effect of P. chrysosporium, dry weight of mycelium pellets, ligninperoxidase (LiP) activity, manganese peroxidase (MnP) activity, oxalic productionand Cd2+concentration after acid extraction were determinated. The results showedthat Cd2+was of highly toxic heavy metal to P. chrysosporium. The toxicity of Cd2+inthis study mainly had fungistatic effect but not fungicide effect on P. chrysosporiumbelow100mg/L. Cadmium would seriously inhibit fungal growth and reproduction at50mg/L. LiP and MnP activities would be inhibited by trace amounts of Cd2+. Withthe increasing Cd2+concentration, LiP and MnP activities decreased and the inhibitiongradually strengthened. The activities of lignin-degrading enzymes were stronglyinhibited under the Cd2+concentrations of50mg/L and100mg/L, but20mg/L of Cd2+did not have a significant inhibitory impact. For resisting the toxic injury, P.chrysosporium produced active defense mechanisms through secreting oxalic. Cd2+concentrations of heavy metals in the range of the experimental studies (0-100mg/L)could promote extracellular secretion of oxalate.Further study on the impact of different concentrations of Cd2+to the secretion oforganic acids by P. chrysosporium, for oxalic, Cd2+concentrations in the range of0-0.8mmol/L could promote secretion of oxalate, and Cd2+concentration of1.0mmol/L and above could inhibit secretion, and the higher concentration, the moreobvious inhibition. For malic acid, all of the Cd2+concentrations under theexperimental studies (0-5.0mmol/L) played on the malic acid secretion inhibition.For fumaric acid, Cd2+concentrations in the range of0-0.8mmol/L could promote itssecretion, and the Cd2+concentration promoted the strongest tendency for0.5mmol/L. Cd2+concentration of1.0mmol/L and above could inhibit secretion, and the higherthe concentration, the stronger inhibitory effect.