The Synthesis Study Of Functional Inorganic Materials Based On Bacterial Surface Display System

Bacterial surface display technology,can be used to display specific functional protein on the surface of bacteria,which then can be acted as a micro-reactor.Surface displayed functional proteins are equipped with high activity and easier to be manipulated,which therefore are widely used in many fields,such as catalysis in vitro,bio-adsorption,recombinant bacterial vaccines,antigen epitope analysis,environmental remediation,and so on.Ice nucleation protein（INP）,is one kind of common and efficient carrier protein used in bacterial surface display system.INP can not only be stably expressed in a various host cells,but also be effectively transported throughout cell membrane and anchored on the surface of cells by N-terminal domain.Additionally,INP is able to display proteins with higher molecular weight,and the transport efficiency is high;the passenger proteins displayed by INP can properly fold and maintain high protein activity.Bacterial surface display technology is also an important technique of cellular shellization.A single cell without mineral shell can be constructed with an artificial shell by displaying protein which can induce mineralization.Natural Silaffin and Silicatein protein can effectively aggregate silica from the external environment and form sophisticated siliceous structure.Furthermore,Silicatein can catalyze and deposit some other metal oxide materials,such as titanium dioxide,gallium oxide.Utilizing molecular biology techniques,we combined two kinds of silicon proteins,Silaffin and Silicatein,and displayed them on the surface of E.coli by INP,and then we proceeded the biomineralization,the specific studies are show as follows:（1）:Two kinds of silicon protein,Silaffin and Silicatein,were displayed on the surface of E.coli by INP,and the recombinant protein（INPSiliSila）was induced by Isopropyl-β-D-thiogalactopyranoside（IPTG）.After optimizing protein expression conditions,we can obtain surface displayed E.coli with high expression rate of protein.By SDS-PAGE electrophoresis analysis,we can see that INPSiliSila was distributed in inclusion bodies and cell membranes,and thus we can conclude that part of the recombinant proteins can be transported,secreted and anchored to the cell membrane by INP anchoring motif.（2）:The surface displayed silicon protein was used for E.coli silicification study.By characterizing,we can conclude that the displayed INPSiliSila can effectively deposit silica particles on the surface of E.coli,and the E.coli cells can maintain the bacterial morphology after deposition.In addition,in the TEOS system,we can see that the bacteria with INPSiliSila expression survived longer after deposition;and from the measurement results of viability detection;we can reach a conclusion that the bacteria with INPSiliSila maintained good bacterial morphology after thermal treatment.All of these results indicated that the silicon mineralization shell can be a protective coat for E.coli.（3）:The displayed silicon protein was used to deposit titanium on the surface of E.coli.After characterization,we can draw a conclusion that INPSiliSila can effectively deposit titanium dioxide on the surface of E.coli,and the titanium dioxide deposited E.coli cells with INPSiliSila can maintain good bacterial morphology before and after calcination.Furthermore,in TiBALDH system,the biomineralization buffer and time definitely had influence on the crystalline:in the PBS system,at the incipient time of biomineralization,TiP2O7 is prone to produce,but NaTi2（PO4）3 is more easier to produce when incubation time was prolonged;in the TBS system,at the incipient time of biomineralization,NaTi₂（PO₄）₃ is prone to produce,but anatase is more easier to produce when incubation time was prolonged.（4）:The bacteria displayed with INPSiliSila were used as template to synthesize titanium materials.We synthesized a kind of uniformed anatase titanium dioxide（TiO₂）material with morphology of short-rod-shape and smaller nanoparticles.By the characterization of as-prepared samples,it proved to be hollow mesoporous anatase titanium dioxide material,which exhibited higher charge-discharge capacity and excellent cycle stability when it was used as anode material in lithium-ion battery.