Developments in enzyme immobilization and near-infrared Raman spectroscopy with downstream renewable energy applications.

摘要

The use of renewable forms of energy has been proposed to be one long-term pathway to reducing the world's dependence on fossil fuels, despite the current requirement of fossil fuel input to generate renewable fuels. Bioethanol is produced from the hydrolysis of cellulose to glucose, and subsequent or simultaneous fermentation of glucose to ethanol. Grasses such as miscanthus and switchgrass, as well as crop residues, such as sugarcane bagasse and corn stover, have shown promise as sources for bioethanol production. In order for the bioethanol industry to supplant fossil fuel production, the conversion of lignocellulosic materials to fuel must be economically viable. This economic practicality includes the techniques used to screen and select from the diverse range of biomass, the cost of pretreatment reagents and organisms used in hydrolyzing and fermenting cellulose and glucose, respectively, and the neutralization of pretreatment effluents. Hemicellulosic and lignin wastes and side-reaction products must also be developed into useful bio-products. An instrumental technique is needed that can rapidly screen biomass in situ, or with little to no sample preparation, that is not inhibited by the presence of water, and that can provide both qualitative and quantitative information.;The first objective, in this thesis research, was to study how immobilized cellulase compared to free cellulase in the ability to convert cellulose to glucose at sub-optimal reaction conditions. Immobilization has been shown to provide enhanced enzyme stability as well as recyclability, which inherently lowers production costs of the end product. Ethanol yields increased 2.1-2.3 times when immobilized cellulase was used in simultaneous saccharification and fermentation (SSF) reactions, compared to free cellulase.;The second objective was to develop near-infrared (NIR) Raman spectroscopy applications for the characterization of lignocellulosic biomass. NIR Raman spectroscopy can meet current needs in the rapid screening of biomass for biofuel production, given its non-invasive and non-destructive nature, and its amenability to samples containing water. A 1064 nm Raman instrument is described, and applications include quantifying lignin monomer composition in extracted lignin and raw lignocellulosic biomass, as well as the characterization of biomass feedstocks for extractive content.