Environmental concerns about urban air quality, global climate change, energy security and economic considerations motivate a growing interest in alternative fuels for the transportation sector. Ethanol, a fermentation-derived fuel, can be produced by bioconversion of renewable materials, such as wood, grass, and waste. Combustion of ethanol fuel, in both neat and blended form, can improve the engine efficiency, and lower the emission of CO, NO[subscript x], and volatile organic compounds (VOC), hence reducing the urban ozone level. Moreover, enhanced agricultural activities for production and collection of lignocellulosic feedstocks and industrial developments for production of ethanol will help the economic growth by creating new jobs and new income sources. Bioconversion of lignocellulosic feedstocks into ethanol requires a pretreatment process to increase the digestibility of cellulose by cellulolytic enzymes. The dilute-sulfuric acid pretreatment can hydrolyze hemicelluloses (xylan), disrupt lignin structure, and increase the yield of ethanol production from fermentation of monomeric units of cellulose (glucose). In this study, herbaceous (corn stover and switchgrass) and woody (poplar chips) feedstocks were pretreated with dilute sulfuric acid (0.6, 0.9, and 1.2% w/w) in a batch reactor at relatively high temperatures (140, 160 and 180��C). A unifying kinetic model including reaction time, temperature and acid concentration was developed, and pertinent kinetic parameters were determined. This model can predict the percentages of xylan remaining in the pretreated solids, net xylose yield in the liquid prehydrolysate, and xylose loss after pretreatment of a feedstock at a certain set of reaction conditions. Using this model, four optimum reaction conditions for obtaining maximum net xylose yield in the liquid prehydrolysate were identified. The yield and rate of ethanol production from the optimum prehydrolysates by the pentose fermenting yeast, Pichia stipitis, were determined. It was found that pretreating the selected feedstocks at 170-180��C with 1.0-1.2% sulfuric acid for 1-3 min resulted in the recovery of 80-85% of the original xylan in the liquid prehyrolysate. It was also found that feedstocks with higher neutralizing capacity (e.g., corn stover) produced lower sugar yields as a result of acid neutralization. Pretreatment of feedstocks at conditions beyond the optimum reaction conditions would increase the extent of xylose degradation, and lower the yield and rate of ethanol production due to loss of fermentable sugars and formation of toxic byproducts. The optimum prehydrolysates of corn stover produced the highest yields of ethanol (0.39-0.47 g ethanol/g xylose) followed by switchgrass (0.36-0.45) and poplar (0.26-0.44). The inhibitory effects of byproducts (e.g., acetate) was more pronounced in poplar prehydrolysates. / Graduation date: 1997

Aerobic heterotrophic bacteria associated with oyster larvae feed algae Isochrysis galbana, Monochrysis lutheri and Pseudoisochrysis paradoxa were isolated and enumerated. The bacterial numbers ranged from 7.8x10³ to 3.9x10⁶ CFU per ml. The bacteria associated with Pseudoisochrysis sp. were identified and the majority of isolates belonged to genera Leucothrix (51%). Also present were members of Pseudomonas III sp. (19.1%), atypical Moraxella sp. (16.8%), Moraxella sp. (7.2%) and Flavobacterium sp. (5.9%). The growth of bacteria on marine agar was fastidious and took four days to form visible colonies. None of the bacterial isolates grew in buffered salt broth in which the algae had been grown. Marine broth supplemented with 0.1% beef extract best supported the growth of the isolates, while ferric citrate (3x10⁻⁴ M) supported their growth in buffered salt broth. The role of algae as a solid support for bacteria was investigated by studying the attachment of bacteria on glass slides suspended in the growth medium. The percent of Leucothrix sp. attached to the slide was 2.1-3.0%. This was four to six times greater than that of Staphylococcus (0.5%), an organism well known for its commensal growth on skin and mucus membranes of man and animal. Hydrophobic attraction, which is thought to play an important role in the orientation of bacteria to solid surfaces, was studied by measuring the adsorption of bacteria on hydrocarbons introduced to a bacterial suspension. Leucothrix sp. exhibited the strongest affinity, whereas Flavobacterium sp. and Pseudomonas sp. adsorbed the least. An attempt to obtain an axenic culture of algae by antibiotic treatment was unsuccessful due to the detrimental effect of antibiotics to both algae and bacteria. / Graduation date: 1982

Thesis (Ph. D.)--Oregon State University, 1981. / Typescript (photocopy). Includes bibliographical references (leaves 93-98). Also available on the World Wide Web.

No description available.

Thesis (Ph. D.)--Case Western Reserve University, 2009. / Frances Payne Bolton School of Nursing. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaf 137). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaf 137). Also available on the Internet.

Thesis--PlanA (M.S.)--University of Wisconsin--Stout, 2003. / Includes bibliographical references.

Thesis--M. Phil., University of Hong Kong, 1978. / Errata slip inserted.

Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Andrei Fedorov; Committee Member: Srinivas Garimella; Committee Member: Timothy Lieuwen; Committee Member: William Koros; Committee Member: William Wepfer. Part of the SMARTech Electronic Thesis and Dissertation Collection.