White Rot Fungus Extracellular Iron Oxide And Its Formation Mechanism

White rot fungus is a good biosorption material.Studies have shown that white rot fungus coupled with iron oxide had a better adsorption effect on pollutants,but most of the current studies used chemically synthesized iron oxide.Iron oxides are widespread in nature,and their natural formation process is affected by microbial mineralization.However,the nature of the iron oxides directly involved in the formation of white rot fungus and their compound environmental effects with white rot fungus are currently unknown.Therefore,this study focused on the nature of the extracellular iron oxide formed by the interaction of Fe³⁺with Phanerochaete chrysosporium,a model species of white rot fungus,and its environmental significance and the influence of the extracellular polymeric substances secreted by white rot fungus on the formation of iron oxides was further analyzed,and the self-assembly behavior of polysaccharides themselves was studied in depth.influences.First,the changes in the physicochemical properties of white rot fungus extracellular polymers and the characteristics of iron oxide on the surface of the bacteria under different concentrations of Fe³⁺were studied.The results showed that in the acidic environment containing iron,stable iron oxides could still be formed on the surface of the bacteria balls;the characterization results showed that the surface of the bacteria balls without Fe³⁺was smooth and free of particles,and the group with Fe³⁺had more particles with a diameter of about 60 nm.The ball was iron oxide particles.The higher the concentration of Fe³⁺added,the denser the iron oxide particles formed on the surface of the bacteria.The infrared spectroscopy data indicated that the hydroxyl groups of polysaccharides in EPS of white rot fungus may be the formation sites of extracellular iron oxides.The white rot fungus loaded with iron oxide increased the adsorption of the two pollutants compared with the blank control bacteria pellets without iron.Capacity,the higher the iron loading capacity,the stronger the adsorption capacity.Because the surface area of the adsorption site was limited,the adsorption efficiency didn’t increase after reaching a certain concentration.The increase of pH was conducive to the dissociation of protons on functional groups,and more electronegative functional groups were generated to bond with pollutants.The maximum adsorption rate was94.58%when the pH was 6 and the maximum adsorption capacity was also 181.36mg/g.The adsorption of methylene blue was significantly affected by temperature.The main phase of iron mineralization in the white rot fungus SMP polysaccharide system in the late stage of the simulation experiment wasβ-FeOOH,while the iron oxide mineral phase usually formed by iron bacteria in nature wasα-FeOOH.When the mineralization time,the initial addition of Fe³⁺concentration,polysaccharide concentration,temperature,and pH changed,the iron oxide also transformed betweenα-Fe₂O₃,α-FeOOH andβ-FeOOH.Through the Congo red experiment and the molecular weight determination,the white rot fungus polysaccharide has a triple helix structure,and it was determined to be an amorphous non-crystalline structure through characterization.Microscopic experiments showed that its shape was a chain-like agglomerated structure and had Self-assembly behavior.The experimental results also show that the-OH groups in polysaccharides provide sites for the formation of iron oxides.In summary,under acidic culture conditions,iron oxide nanoparticles could be formed on the surface of white rot fungus.The formation process was affected by extracellular polysaccharides,which improved adsorption of white rot fungus on pollutants.In addition,the soluble polysaccharides produced by bacteria also affected the formation of iron oxides through regulation,and their self-assembly properties may also play a part in this process.The research results of this paper were of great significance to further understand the biomineralization process of iron oxides and its environmental effects,and provided a theoretical basis for the combination of environmental nanomaterials and environmental microbes.