Enhanced Stability Of Immobilized Enzyme By Biomimetic Nano-coating And Microreactor Construction

Biomimetic nano-coatings refer to the films synthesized under mild conditions?room temperature,atmospheric pressure,neutral pH?inspired by natural phenomena and principles.Biomimetic nano-coating can provide a good physical and chemical microenvironment for enzyme molecules attributed to its mild preparation conditions and controllable structure.Due to the low enzyme stability and difficulty for continuous synthesis of product in industrial scale,the biomimetic nano-coating was itroduced into enzyme immobilization,which finally effectively enhanced the stability of the immobilized enzyme.Then,a packed bed microreactor was constructed for the enzymatic synthesis of 6-aminopenicillanic acid continuously and efficiently.The main contents are as follows:Firstly,the immobilized enzyme microreactor was constructed through immobilizing penicillin G acylase?PGA?on the cordierite honeycomb ceramics modified by biomimetic coating of poly?dopamine?.Poly?dopamine?increased the stability of immobilized enzyme by covalent binding of catechol/quinone with enzyme molecules.The enzyme activity was maintained 84.01%of its initial activity after 195 min reaction at 313 K.Secondly,PGA was immobilized on the cordierite honeycomb ceramics modified with poly?dopamine?nanocoatings.Then,an organosilicon layer was formed through thesol-gelprocessof?3-aminopropyl?-triethoxysilane?APTES?and tetraethylorthosilicate?TEOS?induced by the poly?dopamine?nanocatings.This organosilicon layer can effectively protect the enzyme and improve its structural stability.The immobilized enzyme microreactor was constructed and showed good stability in extreme pH values?pH 6.0 and pH 10.0?after 195 min reaction.The enzyme activity was maintained 89.72%of its initial activity after 195 min reaction at313 K.The activity of Organosilicon/PGA/Poly?dopamine?/Cordierite still maintained73.05%of its initial activity after 15 reaction cycles.Thirdly,PGA was immobilized in AB-8 macroporous resins by physical adsorption,and then TA-Ti^IV layer was formed by tannins?TA?and titanium?IV?coordination.TA-Ti^IV coating can improve the hydrophilicity of the surface of the resin,effectively prevent the leakage of the enzyme and improve the stability of the immobilized enzyme,especially the cycle stability and storage stability.TA-Ti^IV-capped PGA@Resins maintained 103.7%of the initial enzyme activity after storage for 68 days,and maintained 81.51%of the initial enzyme activity after 20reaction cycles.