(27e) Cellulose Hydrolysis Using Chitosan Coated Enzyme-Magnetic Nanoparticle

The heavy energy dependency on foreign oil, emissions of greenhouse gases, and risks associated with the price fluctuations in the international energy markets lead many countries to start to look into new energy strategies emphasizing various renewable energy sources is emphasized. Among strategic renewable energy resources (biomass, solar, wind, and geothermal), biomass is given a high priority as it can be directly utilized for the production of various alternative transportation fuels with a better carbon footprint. However, ethanol production from biomass consists of several costly and energy-inefficient steps and enzyme-magnetic nanoparticles(MNPs) conjugate was one suggested technology proposed to overcome this hurdle. However, the colloidal stability of magnetic nanoparticles becomes an issue due to self-aggregation. In particular, aggregation can be considered as a limiting factor for non-soluble substrates such as pretreated cellulose. In this study, we have investigated increasing the colloidal stability of magnetic nanoparticles by surface modification with chitosan (CS) and immobilized exo-cellulase, endo-cellulase and β-glucosidases on the surface of MNPs. Over 65^oC, native enzymes lost their glucose production capacity dramatically after a two-hour exposure. In contrast, CS-MNP bioconjugates retained their glucose productivity (39.4% at 65^oC and 22.2% at 85^oC) after 5 hours to exposure high temperatures. Recycling stability tests indicated that CS-MNPs bioconjugates can be used over 20 cycles with reasonable glucose production, and after 10 times reuse, glucose production can be comparable with a single use of a native enzyme. It was found that we can achieve the same, or even more product in the process of recycling and the enzyme is sufficiently stable such that recycling affords an opportunity for reducing costs.