| Fermentation of transportation fuels from cellulosic biomass is one suggested solution to address concerns over energy security and sustainability. However, saccharification of cellulosic biomass faces several challenges. Firstly, cellulose is highly stable. Conversion of cellulose to sugars requires several days to reach sufficient conversion levels, even with enzymatic assistance. Secondly, the enzymes are expensive and sensitive to thermal and mechanical inactivation. Finally, cellulose is found in biomass in conjunction with other structural components such as hemicellulose and lignin, which block access to the cellulose and necessitate harsh, energy intensive pretreatment processes.;To address these difficulties, this research demonstrates that moderate electric field (MEF) treatments can increase the effectiveness of enzymatic saccharification. MEF treatments apply alternating current electric fields with arbitrary waveforms (typically ranging in intensity from 1-100 V cm-1). MEF treatments have been shown to influence a number of biological processes, which range from diffusion and extraction to microbial metabolisms. In the following studies, MEF treatments were applied under various experimental conditions with the objective of determining which aspects of the treatment were most significant to enzyme activity. Six MEF treatment variables were considered: field strength, frequency, application regime, temperature, agitation/mass transfer, and substrate.;Although the enzyme responded to changes in the frequency of the waveform, field strength and application regime had a greater effect on enzyme activity. It was found that the electric field could have a positive, negative, or negligible effect depending on the field strength. At 50°C, the optimal temperature for cellulase, field strengths of 8 V cm-1 and 8.75 V cm-1 improved early reaction rates. Treatments at 6.25 V cm-1 did not produce a significant effect while 12 V cm-1 treatments significantly increased enzyme inactivation. These effects were maximized at a frequency of 50-60 Hz. No effects were observed when the system was well agitated implying the improvement stems from enhanced mass transfer. Lignocellulose was also used as the substrate during well-mixed enzymatic hydrolysis. However, no improvement was observed under those conditions.;Most notably, when MEF treatments were applied over a range of temperatures, it was found that MEF treatment significantly improved enzyme activity at lower temperatures. This leads to the observation that MEF treatment imitates a temperature increase. Calculations simulating the electrophoretic motion of the enzymes verified that the magnitude of motion associated with the MEF treatments was similar to the change in molecular motion associated with temperature increases.;The final chapter considered the use of ohmic heating during alkali pretreatment of lignocellulose. Alkali pretreatment is a leading method for biomass pretreatment because it removes lignin with only minor reductions to the cellulose content. No significant differences were observed in either the biomass composition or yield from hydrolysis between the ohmic and conventionally heated alkali pretreatments. This suggests that energy-efficient ohmic heating is a viable method for providing process heat during alkali pretreatment processes. |
