Browsing by Subject "NADH oxidation"

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    Intensified biocatalysis for production of fuel and chemicals from lipids.
    (2010-03) Zhao, Xueyan
    Triglycerides are abundant biorenewable resources found in vegetable oils and fats. The effective utilization of triglycerides is one of the key interests in developing renewable fuels and products. However, triglycerides are difficult and inefficient to be used as fuels directly in regular combustion engines. The area of biodiesel synthesis concerns reactions converting triglycerides to methyl or ethyl monoesters for better fuel properties. This process releases glycerol as byproduct. This thesis aims at developing novel biocatalytic conversion of triglycerides and glycerol for the production of fuels and chemicals. One key challenge in realizing efficient biocatalytic synthesis of biodiesel is to improve reaction velocity and catalyst efficiency. This research explored a unique approach by developing organic-soluble lipase for a one-pot synthesis-and-use strategy. The productivities of the modified lipase in a water-free reaction system were found to be over two orders of magnitude higher than previously reported results. Whereas native lipases showed no activity in the absence of water, the organic soluble lipase demonstrated reaction rates of up to 33 g-product/g-enzyme-h. As for the byproduct (glycerol) from biodiesel synthesis, current research has mostly focused on derivation of value-added chemicals instead of being used as a simple additive in processing of food and personal care products. Key issues centered on how to produce the desired products most efficiently and selectively from glycerol. Enzymatic conversion of glycerol can produce 1,3-dihydroxyacetone (DHA), a unique and versatile chemical with a broad range of application potentials, by selective oxidizing the hydroxyl group(s) of glycerol. The price of DHA is more than 200 times higher than that of glycerol. In this work, DHA production was tackled through a novel biocatalytic process. Focus was placed on several aspects in understanding and optimizing the process including selection and improvement of biocatalyst, development of novel carbon electrode materials for cofactor regeneration, and reactor design. One potential advantage of using bioelectrochemical method for cofactor regeneration is the possibility to integrate the biochemical process with biofuel cells for simultaneous chemical production and power generation. Toward that, this thesis explored the necessary fundamental issues, including the construction and study of a model glucose/oxygen biofuel cell.