Dynamic Adsorption Behaviors Of Metal Ions-Bt Protein Binary Systems On Minerals And Microbial Surfaces

The cultivation area of transgenic insect resistant Bt crops is increasing.The Bt protein released into the soil environment may affect the adsorption and migration of metal ions on the surface of minerals and microorganisms with multi-media/multi interface behavior,and further restrict the availability of metals in the soil.In this thesis,Quartz crystal microbalance with dissipation（QCM-D）technology was used to monitor the adsorption dynamic behavior and micro mechanism of metal ions-Bt protein binary system interaction on the surface of minerals and microorganisms in real time.The main research results are as follows:1、The difference of adsorption capacity between the two minerals for Bt protein,Cd²⁺/Zn²⁺and metal ion-Bt protein binary system is related to the difference of charge and surface activity on the mineral surface.Macromolecular Bt protein is adsorbed on the first surface layer by minerals through electrostatic interaction at regional sites.Metal ions can interact with Bt protein to form double-layer adsorption on the mineral surface.2、The changes of p H,buffer concentration,ionic strength and initial metal concentration in environmental conditions will affect the changes of charge and force between Zn²⁺/Cd²⁺-Bt protein binary system and minerals,and further affect the changes of adsorption capacity and adsorption state behavior of Zn²⁺/Cd²⁺-Bt protein binary system on the surface of mineral Al₂O₃ and Si O₂.3、The pseudo second-order reaction kinetic equation is more suitable to describe the adsorption of Zn²⁺/Cd²⁺-Bt protein binary system on the surfaces of two minerals,and the Freundlich isothermal adsorption model is well suitable to describe the adsorption of minerals on Zn²⁺/Cd²⁺-Bt protein binary system,indicating that it is the double-layer adsorption of metal ion-Bt protein binary system on the surfaces of minerals Si O₂ and Al₂O₃.3、The pseudo second-order reaction kinetic equation is more suitable to describe the adsorption process of Zn²⁺/Cd²⁺-Bt protein binary system on the surfaces of two minerals and microorganisms,indicating that the process is mainly controlled by chemical adsorption;Freundlich isothermal adsorption model is suitable to describe the adsorption process of Zn²⁺/Cd²⁺-Bt protein binary system on the surface of minerals and microorganisms,indicating that the metal ion-Bt protein binary system has double-layer adsorption on Al₂O₃、Si O₂ and E.coli.4、The ability of microorganisms to adsorb metal ions is greater than that of Bt protein and metal ion-Bt protein binary system.The existence of metal ions inhibits or promotes the adsorption of Zn²⁺/Cd²⁺-Bt protein binary system on the microbial surface in varying degrees,which is related to the ability of metal to quench tryptophan in Bt protein.5、Part of the driving force of metal ions adsorbed by microorganisms is electrostatic interaction,and the other part is the combination of metal ions and functional groups on the microbial surface.Metal ions and Bt protein form metal protein complexes through the combination,forming double-layer adsorption on the microbial surface,which is mutually confirmed with Freundlich isothermal adsorption model.6、The results of FTIR showed that Zn²⁺and Cd²⁺coordinated with-NH₂ group on the surface of Bt protein to form metal protein complexes,which was the reason for the formation of double-layer adsorption on the surface of minerals and microorganisms.In addition,hydrophobicity is also an important factor affecting the migration and adsorption of metal ion-Bt protein binary system on microbial surface.