Thesis (Ph. D.)--University of Alabama at Birmingham, 2006. / Title from first page of PDF file (viewed Feb. 22, 2007). Includes bibliographical references (p. 84-95).

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

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

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Mycotoxins are poisonous secondary metabolites commonly produced by fungi and are involved in human disease conditions known as mycotoxicoses. There is evidence to show that food eaten by the rural Black population of Southern Africa is contaminated with mycotoxins. A tenuous relationship exists between the occurrence of mycotoxins in foods and certain disease conditions in humans. In order to verify this relationship, efforts have, in the past, been made to detect mycotoxins and their metabolites in physiological fluids and tissues. The difficulty with this approach is that mycotoxins in the body have short half lives, being rapidly excreted or metabolised to other forms. More recently it has been shown that aflatoxin B1, as its activated epoxide, can conjugate with macromolecules such as nucleic acids and proteins. These survive for much longer than the free toxins and by suitable methods can be isolated and measured. This allows for a much better estimate of exposure of the individual to aflatoxin. This study reviews and evaluates screening methods for the detection and analysis of mycotoxin contamination in rural foodstuffs such as maize and groundnuts. Methods for the production of aflatoxin-lysine and protein adducts are motivated and developed then used in the identification of naturally occurring adducts in humans. Isolation and quantitative analysis techniques are proposed to routinely screen patients for evidence of aflatoxin exposure. / Thesis (M.Med.)-University of Natal, Durban, 1995.

This work begins with chemotaxis studies involving Salmonella typhimurium. Known chemical attractants (ribose, aspartic acid, etc.) and repellents (nickel chloride, sodium acetate, etc.) were tested to direct bacteria swimming patterns. It was found that high concentrations of both attractant and repellent, approximately 10% chemical in deionized (DI) water, yielded better separation results than lower concentrations, such as 1% and .1% chemical in DI water. Utilizing these attractants or repellents appropriately can allow live bacteria to be directed in a desired manner in a microfluidic device, while dead bacteria, which yield no response, can be separated into a waste reservoir. Another important aspect of bacteria separation is preconcentration, or the process of concentrating bacteria in a usable amount of liquid for further analysis in a microfluidic device. This study introduces a method of capturing Salmonella typhimurium through the use of magnetic nanoparticles (MNPs) without functionalizing them with antibody or amine coatings. Based on the work by Deng et al., MNPs were prepared in various ways to alter their diameter and surface characteristics to achieve optimal bacteria capture efficiency. A capture efficiency of approximately 94% has been achieved by altering chemical quantities in the MNP fabrication process. A macro-scale flow cell prototype was designed and characterized in order to ‘clean’ large volumes of buffer and separate the bacteria-MNP aggregates through the use of a magnetic field. Finally, intervention of bacteria is a significant topic in food safety applications. This study utilizes Fe (III) to inhibit bacteria growth. This chemical was used in the presence of Salmonella, E. coli, Staphylococcus, and Pseudomonas. Further experiments were conducted with raw chicken and lettuce contaminated with Salmonella typhimurium. Using as little as .005M Fe III in DI water, up to 5 orders of magnitude reduction in bacteria growth was seen on test plates as compared to control plates.

Several powdered food products were screened using repetitive element palindrome PCR (rep-PCR) for the presence of enterotoxin producing species of Bacillus. Samples from these products were screened by being placed into a tryptone-peptoneglucose-yeast enrichment medium (TPGY), heat-treated, and shake-incubated. DNA was extracted using a modification of established protocol, leading to the development of an optimized method for each food system. Purified DNA was amplified through rep-PCR using extragenic sequence-targeting primers and optimized for each food product. Amplified PCR products were analyzed electrophoretically and viewed using an ultraviolet photodocumentation system. Bacillus cereus positive control DNA fingerprints were compared to banding patterns from enriched food samples, revealing the presence of the typical diagnostic 1,230 bp band in non-fat dry milk (NFDM). Restriction Fragment Length Polymorphism (RFLP) with Alu I restriction enzyme was performed on the 1230 bp diagnostic band from NFDM and displayed a profile consistent with Bacillus cereus positive control. RPLA (Reverse Passive Latex Agglutination) and BDE ELISA (Bacillus Diarrhoeal Enterotoxin Enzyme Linked Immunosorbent Assay - Tecra Diagnostics) confirmed the presence of HBL and NHE enterotoxin production in NFDM, Coffee creamer, infant milk formula, and two lecithin samples. / Department of Biology

Thesis (M.P.H.)--University of Nevada, Reno, 2006. / "May 2006." Includes bibliographical references (leaves 83-87). Online version available on the World Wide Web.

Thesis (M. Sc.)--Victoria University (Melbourne, Vic.), 2006. / Includes bibliographical references.

Thesis (M.S.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographical references.