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In order to produce ethanol derived from lignocellulosic feeds at a cost that is competitive with current gasoline prices, the fermentation process, converting sugars to produce ethanol and the subsequent purification steps, must be enhanced. Due to their comparatively lower costs, the widespread availability across a range of climates, and their status as a dedicated energy crop, lignocellulosic biomass feeds are ideal raw materials that can be used to produce domestic fuels to partly displace our dependence on non-renewable sources. Currently, a major drawback of the technology is the relatively low ethanol tolerance of the micro-organisms used to ferment xylose and glucose. To alleviate the ethanol inhibition of Escherichia coli KO11 (ATCC 55124) during fermentation, online ethanol sequestration was achieved through the implementation of an externally located packed bed adsorber for the purpose of on-line ethanol removal (using F-600 activated carbon). By removing ethanol from the broth during the fermentation, inhibition due to the presence of ethanol could be alleviated, enhancing the substrate utilization and fermentation rate and the ethanol production of the fermentation. This study details a comprehensive adsorbent screening to identify ethanol selective materials, modelling of multi-component adsorption systems, and the design, implementation and modelling of a fermentation unit coupled with an externally located packed bed adsorber.

M.Tech. (Chemical Engineering) / Please refer to full text to view abstract

According to a conditioning analysis of tolerance, pharmacological conditional responses (CRs) contribute to tolerance. It has previously been reported that, as expected on the basis of this model, tolerance to the hypothermic effect of ethanol is attenuated by "external inhibition," i e., by the presentation of a novel stimulus (a strobe light). However, results of more recent research indicate that novel stimuli augment the hypothermic effect of ethanol in rats receiving the drug for the first time It is possible, therefore, that a novel stimulus apparently attenuates ethanol tolerance because it augments ethanol-hypothermia, rather than because it functions as an external inhibitor. Results presented in this thesis confirm reports that ethanol-induced hypothermia is augmented by a novel stimulus, thus prior demonstrations of external inhibition of ethanol tolerance is equivocal Further experiments in this thesis evaluated external inhibition tolerance to another effect of ethanol — ataxia Although the initial ataxic effect of ethanol (unlike the hypothermic effect) is not enhanced by a novel stimulus (a strobe light/white noise combination), the stimulus reinstated ethanol-induced ataxia in tolerant rats. Tolerance was also disrupted by the novel omission of the strobe/noise stimulus Thus, experiments in this thesis demonstrate external inhibition of ethanol tolerance in a preparation not confounded by the effects of the novel stimulus on initial responding to ethanol. Experiments reported in this thesis also demonstrate that tolerance to the ataxic effect of ethanol is mediated by a compensatory CR, termed "hypertaxia " The compensatory CR was disrupted by the novel addition and novel omission of the strobe/noise stimulus providing converging evidence that the attenuation of tolerance by a novel stimulus results from external inhibition of Pavlovian conditioning Finally, external inhibition of ethanol tolerance was not evident when there was a long delay between tolerance development sessions and testing These data are consistent with an associative analysis of tolerance which suggests that contextual control of tolerance should be minimized as the interval between training and testing is increased / Thesis / Doctor of Philosophy (PhD)

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

This study evaluated the effectiveness of using cellulosic adsorbents to dehydrate 95 wt% ethanol/5 wt% water mixture. Hardwood sawdust, kenaf core, and bleached wood pulp were used as adsorbents in both liquid phase and gas phase experiments. All three adsorbents preferentially adsorbed water compared to ethanol. Bleached wood pulp exhibited the best performance of adsorbents examined. Data from the liquid ? phase experiments were fitted to the Chakravarti ? Dhar isotherm equation. From the vapor ? phase experiments, the average water loading of hardwood sawdust, kenaf core, and bleached wood pulp was 0.0037, 0.0076, and 0.0121 g H2O/g adsorbent, respectively. Two methods, the Colburn J Factor and the Thoenes ? Kramers correlation, were used to evaluate the mass transfer coefficient of water. Furthermore, the surface area of the adsorbents was measured using the B.E.T. method. Surface areas were 4.91, 9.99, and 8.84 m2/g for the hardwood sawdust, kenaf core, and the bleached wood pulp, respectively.

Ethanol produced from lignocellulosic agricultural products and waste is an environmentallyriendly alternative to petroleum-derived fuel. Lignocellulosic biomass is gasified producing synthesis gas, which is composed of CO, CO2, and H2. Synthesis gas is fermented via anaerobic biocatalyst. The bacterium was grown in a fructose-rich medium then concentrated in ethanol production medium for synthesis gas fermentation. While the known ethanol-producing bacterium Clostridium ljungdahlii was used to provide baseline values for synthesis gas utilization and ethanol production, synthesis gas fermentation were conduced with a culture discovered at Mississippi State University. Additionally, efforts were made to isolate other anaerobic cultures capable of fermenting synthesis gas to ethanol.

Commercial activated carbon and newly polymer-derived carbon were utilized to selectively remove the model fermentation inhibitor, furfural, from water solution during bio-ethanol production. Morphology, pore structure and surface chemistry of the sorbents were characterized. The oxygen groups on the carbon surface were believed to have contributed to the decrease on the selectivity of activated carbon between furfural and sugars (Sugars are the valuable source of bio-ethanol production and should not be separated from solution). Oxidization of activated carbon by nitric acid generated more information which supports the above assumption. Different adsorption isotherm models and kinetic models were studied to fit commercial activated carbon and polymer-derived carbon individually. Bacterial cell growth, sugar consumption, and ethanol yield during the fermentation were investigated after inhibitors were selectively removed from the broth. The fermentation time was reduced from one week to one day after inhibitor removal. Different methods of sorbent regeneration were investigated, including thermal regeneration, pH adjustment and organic solvent stripping. Low ethanol-containing water solution appears to be the most cost-effective way to regenerate the spent sorbent in the industrial application. A sorption/desorption cycle was designed and the sorbents were regenerated in a fixed-bed column system using ethanol-containing liquid from fermentation. The results were stable after running 20 times of sorption/desorption cycle.