Novel nanobiocatalysts for chemical processing and biofuel cells

Low catalytic efficiency and stability of enzymes have been seen as barriers for the development of large-scale operations to compete with traditional chemical processes. Over the past decade, the rapid growth of nanotechnology has created a lot of novel functional materials, as well as nano/microfabrication tools and processes. These technological progresses may also offer promising opportunities for the field of biocatalysis. The present work explored the possibility of utilizing nano-structured materials to construct highly active and stable biocatalysts for applications in both aqueous and non-aqueous environments.; Enzyme-carrying polymeric nanoparticles can be well dispersed in aqueous buffer solution. Due to the unique solution behavior, reactions catalyzed by "nanoparticle enzymes" may represent a transition region between homogeneous (free enzyme) and heterogeneous (immobilized enzyme) catalysis. Mathematic model from reaction mechanism and collision theory indicated that the activity of nanoparticle enzymes might be affected by their mobility. It has been found that the experimental data agreed with the mathematic model in particle size ranging from 100 to 1000 nanometer.; Electrospinning has been proven as an effective and economic process for the preparation of polymeric nanofibers. Bioactive nanofibers were prepared via attaching enzymes to electrospun nanofibers in the present work. The resulting bioactive nanofibers displayed high activity in both aqueous solution and organic solvents. Compared to native enzyme, the stability of the enzyme against solvent denaturation was also greatly improved.; This work also demonstrated that multi-wall carbon nanotubes (MWCNT) could be used to prepare enzymatic electrodes for biofuel cell applications. High enzyme loading was achieved by covalently immobilization of glucose oxidase (a model enzyme) in MWCNT-Nafion composite, which was then coated on conductive backing materials to construct the electrodes. The composite electrodes afforded higher electrochemical flux and enhanced electrode reaction kinetics, as measured by cyclic voltammetry. In a model glucose/O2 biofuel cell system, a power density up to 152 muW/cm2 was observed with the resulting enzymatic electrodes as the anodes. It was believed that mass transfer was the bottleneck that limited the output current and power densities of the biofuel cell system.; Poly(lactic acid) (PLA) is a highly versatile biomaterial for medical and ecological applications. Incorporation of sugars into PLA may generate a new class of polymer with unique properties. A novel two-step approach was successfully developed in the present work utilizing the selectivity of enzymatic catalysis to prepare sugar-containing PLA with linear structure and tunable properties. It is expected that, the catalyst efficiency may greatly improved by immobilization of enzymes (beta-galactosidase, lipase) in nanoporous materials such as silica glass.