This study evaluated the potential of the aerobic Mycobacterium strain JS6O to grow on a variety of organic acid substrates, and the possible effects an organic acid would have on the degradation rate of vinyl chloride (VC). A series of batch growth tests were designed to determine the time it took to consume the substrate and the overall increase in biomass. Strain JS6O was found capable of growth on acetate, propionate, and butyrate, but could not grow on formate or lactate. Acetate was chosen for further study because strain JS6O consumed acetate the most rapidly of all the organic acids tested, and acetate is a common product of fermentation reactions in the subsurface. Strain JS6O was confirmed to grow on both ethylene and vinyl chloride as the sole carbon and energy source. Comparatively, strain JS6O's rate of growth on VC is much slower than that of ethylene. With acetate as an augmenting growth substrate, ethylene and VC utilization rates increased by 30% and 48%, respectively. Since acetate and VC are often found together in contaminated chlorinated ethene plumes, this makes a strong case for natural attenuation of VC by strain JS6O. A series of kinetic tests were implemented to determine the K[subscript s] and k[subscript max] of strain JS6O for ethylene, VC, and c-DCE. The K[subscript s] and k[subscript max] for ethylene determined through NLSR methods was similar to the values published in Coleman et al. (2002), supporting the maintenance of a pure culture throughout the experimental work. When strain JS6O was exposed to the isomers of DCE (trans-1,2-dichloroethylene (t-DCE), cis-1,2-dichloroethylene (c-DCE), and 1,1-dichloroethylene (1,1-DCE)) the cells were unable to grow on these compounds. However, when growing on acetate, strain JS6O cometabolized c-DCE and t-DCE, but not 1,1-DCE, with c-DCE transformed more rapidly than t-DCE. Transformation of c-DCE was also observed with growth on VC and ethylene. The presence of c-DCE was shown to partially inhibit VC degradation, but had no effect on ethylene degradation. The cometabolism results with acetate further indicate that strain JS6O is a good candidate for natural attenuation of multiple chlorinated ethenes in the subsurface. / Graduation date: 2006

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references.

Thesis (Ph.D.) in Food and Nutrition Sciences--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaves 66-76).

Bio-conversion of agricultural wastes provides a viable solution to multiple environmental problems as well as production of natural products. Apple processing for manufacturing juice, pies and sauce results in significant volumes of underutilized by-products. This study aims to optimize the method for producing fermentable sugars from apple processing by-products. The conditions required for pre-treatment, polyphenol removal and enzymatic hydrolysis were optimized. The optimized conditions for dilute sulfuric acid-based hydrothermal pre-treatment were acid concentration of 1.5% (w/v) at 91 oC for 16 min. The final yield of 12.7% fermentable sugars (glucose, fructose and galacturonic acid) was obtained after multistep hydrolysis using commercial cellulase, pectinase and ?-glucosidase at 9, 38 and 8 enzyme units/g FW, respectively. The other optimum conditions were temperature of 40 oC, pH at 4.0 and 24 h of reaction time. These fermentable sugars can further be converted into bio-ethanol and organic acids using specific yeast and bacteria.

Studies were conducted to investigate the interactive effects of exogenous enzymes andorganic acids on in vitro and in vivo nutrient digestion and growth performance of broiler chicks.In Study 1, five exogenous enzyme products including ??-glucanase, xylanase, amylase, ??-galactosidase and protease, were assayed in triplicate at their optimum pH levels and at pH levelsof 3.0, 6.0, 6.5, 7.0 and 7.5, which were used to simulate pH levels found in the gizzard, the diet,the crop, and the proximal and distal parts of small intestine, respectively. The pH gradient wasobtained by dissolving the enzymes in different buffers. Results suggested that the pH levelscommonly found in the avian digestive tract were either too high or too low for maximumactivity of the exogenous enzymes, such as ??-galactosidase and protease.In Study 2, broiler chicks were fed corn basal, barley basal or wheat basal diets withdifferent levels or different sources of organic acids. Dietary inclusion of graded levels oforganic acids linearly reduced the pH of the diet and crop content, but not the pH of the digestasampled in the gizzard and small intestine. The inclusion of 2% organic acids (citric acid orfumaric acid) in broiler diets had either no effect or negative effects on chick growthperformance.In Study 3, an in vitro model was used to simulate the chicken's digestive process in thecrop, the gizzard and the small intestine. Soybean meal and raw whole soybeanwere used as substrates. Graded levels of either ??-galactosidase (0 to 13,792 units/kg) or protease(0 to 888 units/kg) and 0 or 2% citric acid were added to the substrates in a factorialarrangement. Reducing sugars, ??-amino nitrogen and trypsin inhibitor content were measured.The data indicated that increasing levels of ??-galactosidase linearly increased the release of thereducing sugars from the soybean meal. Addition of citric acid further increased the activity of ??-galactosidase, resulting in more reducing sugars were released. Increasing the supplementarylevels of protease linearly increased the ??-amino nitrogen release from the soybean meal and rawwhole soybean. Trypsin inhibitor content in the raw whole soybean was not influenced by theapplication of the protease.In Study 4, broilers were fed low energy or normal energy basal diets with ??-galactosidase,amylase and acidification of diet and water. Growth performance, AMEn and digestibility ofDM, CP and NDF were observed. Alpha-galactosidase improved the AMEn of the diets andincreased the weight gain and feed intake of broiler chicks. Citric acid decreased the crop pH andenhanced the activity of ??-galactosidase in the crop. Citric acid decreased the AMEn of the dietsand chick growth performance. These effects were corrected by supplementing ??-galactosidase.The activity of ??-galactosidase was enhanced by simultaneously using organic acid. Thenegative effects on chick growth performance by dietary inclusion of organic acids werecorrected by simultaneously using ??-galactosidase.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 80-84). Also available on the World Wide Web.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract, appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on October 9, 2009) Thesis advisor: Dr. Andrew D. Clarke. Includes bibliographical references.

Thesis (Ph.D.) - University of St Andrews, June 2009.

No description available.

Dissertation presented in partial compliance with the requirements for the Masters Degree in Technology: Chemistry, Durban University of Technology, 2009. / This study was mainly a response to a challenge faced by ESKOM in its coal-fired power stations. In spite of using high purity water to drive the turbines, the latter were damaged by ‘pitting’, possibly related to acids generated at high temperatures. In the light of this a relatively simple method for determination of short chain organic acids was identified by comparing the efficacies of several methods. It was found that high performance liquid chromatography (HPLC) method preceded by derivatization (with o-nitrophenyl hydrazine) is suitable for analyzing mixtures of simple acids at ppb levels. Calibration was effected by using methanoic acid (formic acid), ethanoic acid (acetic acid), propanoic acid (propionic acid) and butanoic acid (butyric acid). The HPLC instrument used was from Thermo Separations with P2000 pump, SN 4000 interface and UV1000 with a column heater. A comparative study between the HPLC methods using ion exclusion and partition chromatography was carried out in order to find a suitable method that can be used with aqueous environmental samples. The two essential columns that were used were ion exclusion Phenomenex Rezex OA column and a Nucleodur C8 column. The method of partition chromatography using a C8 column showed the most success using a mobile phase consisted of acidified water using HCl (pH4.5) along with a 60:40 Acetonitrile/Methanol mixture. Both isocratic and gradient programs were utilized. Limits of detection were improved from 800ppb (formic acid), 480ppb (acetic), 350ppb (propionic) and 680ppb (butyric acid) to 25ppb (acetic), 60ppb (propionic) and 90ppb (butyric). Samples used in analysis were collected from the main stream, economiser, condensers, polishing plant and turbines of the Tutuka Power Station in Mpumalanga province and analysed using with final developed method / Eskom Tertiary Support Programme. Durban University of Technology