Functionalizing ultrafine fibers via di-functional reagents and their applications in enzyme immobilization

Immobilization of enzymes enables repeated uses, simplifies after-reaction separation and purification as well as improves operational stability. Among solid supports for enzyme immobilization developed to date, fibrous polymeric materials are excellent candidates due to their unique advantages, including high specific surface area, wide ranging porosity, high mechanical strength, and versatile geometries. This research aims to generate functional fibers with highly reactive surfaces as solid supports. Toward this end, three approaches have been developed from the perspectives of attaching amphiphilic spacers, entrapping proteins into ultrafine fibers, and creating surface reactive groups.; The first approach involves activation of cellulose fiber surfaces to provide spacers and reactive groups to tether enzyme proteins. Ultrafine cellulose fibers (500∼800 nm) were generated from an electrospinning process. Activation of cellulose fibers was achieved by reacting with diacylchloride bearing amphiphilic spacers---polyethylene glycol (PEG). Coupling of a lipase enzyme to the PEG-attached cellulose fibers was accomplished by amide bond formation in the presence of a water-soluble carbodiimide. The bound lipase showed much improved stability upon the exposure to organic solvents, and significantly higher retention of catalytic activity at elevated temperatures up to 80°C than crude lipase.; Physical entrapment of enzymes in fibers is a simple yet efficient approach to immobilize enzymes. This work demonstrated that up to 50 wt% of lipase can be electrospun into ultrafine polyvinyl alcohol (PVA) fibers without significant loss in its activity and macroscopic phase separation. Entrapped lipase exhibited much improved storage stability than crude lipase.; Another functional support---aldehyde-containing cellulose (Cell-CHO) was generated from the reactions of cellulose with glutaraldehyde (GA). The factors that controlled the activation level---the quantity of aldehyde, including concentrations of GA and a Lewis acid catalyst, and reaction temperature were studied. Furthermore, a small amine-bearing compound was attached to Cell-CHO, showing its potential for protein immobilization.; Finally, ultrafine fibrous PVA membranes, produced by electrospinning of aqueous PVA solution, were rendered water stability by reacting with GA and PEG diacylchloride. This water-stable PEG grafted PVA membrane is expected to be useful in biomedical and biotechnological fields.