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Thesis(M.S.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Howard Liljestrand. Vita. Includes bibliographical references. Also available from UMI.

Thesis (M.S.)--University of Montana, 2007. / Title from title screen. Description based on contents viewed July 24. 2007. Includes bibliographical references (p. 109-114).

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Maize (Zea mays L.) is an important cereal world-wide, serving as seed for growers, food for man and livestock as well as an industrial raw material. Unfortunately, it is also a suitable substrate for growth, development and activity of spoilage fungi. Fungal growth is a major problem in cereal grains throughout the world and may lead to poor quality of the products, as well as adverse effects to human and animal health due to mycotoxin production. Maize is usually harvested at high moisture content and then dried to bring down the moisture content to a safe level before storage. Delay in drying to safe moisture levels increases risks of mould growth and mycotoxin production. In rural villages maize is dried using only sun drying and they rely on sacks, thatched silo and drums as their storage facilities. This is insufficient to prevent damage by insects, rain, and rodents, which in turn allows fungi to invade these storage facilities. Maize was sampled in two rural areas of Venda (Limpopo Province) and the percentage moisture content was determined and then screened for total fungal contamination. The samples were also analysed for mycotoxins that have been reported to commonly occur in maize. There was no significant difference in the extent of fungal contamination in Mapate and Folovhodwe villages. Of the fungal species detected, Aspergillus species were the most common with Aspergillus flavus being the most predominant. On analysis by the multi-mycotoxin screen, aflatoxin had the highest incidence amongst mycotoxin, followed by T-2 toxin. However on using the VICAM method of analysis aflatoxins, deoxynivalenol and fumonisin were the most predominant mycotoxins in the samples, while zearalenone toxin was also amongst predominant mycotoxins but with the highest level of 0.1 ppm. Most of the mycotoxin-containing extracts were found to reduce the % cell viability of human lymphocytes, after 24 hours of incubation as determined by the methyl thiazole tetrazolium salt assay. vii In conclusion the co-occurrence of these toxins in maize and maize meal may highlight the problems associated with the intake of numerous toxins that could in turn lead to more adverse health effects such as liver, oesophageal, breast and cervical cancer, male reproductive tract damage and gynacomastasia. There is, therefore, need to disseminate information to these people, using simplified methods such as programs on radio and televisions on mycotoxin hazards and discussion on the issue should also feature regularly on daily newspapers and magazines, about the dangers and management aspects of mycotoxins, and the susceptible produce. / Prof. M. F. Dutton Mr. F. E. van Zyl

D.Tech. (Biomedical Technology) / To determine the quality of human food commodities commonly consumed in Cameroon, various districts in the western highland (Bamenda and Kumbo) and tropical rain forest (Douala and Yaounde) regions were sampled. Two mycological investigations were conducted to evaluate the incidences of mycotoxigenic fungi (95 samples) and mycotoxins (82 samples). Serial dilution of ground samples was employed to isolate fungi, subculture on various culture media and fungal species were identified morphologically followed by molecular phylogenetic approach. In general, data obtained indicate samples from various geographical regions showed no consistent variation with regard to the type of fungal species. The mycobiota of food materials were characterized by a diversity of fungal species with the predominance of Aspergillus (125 isolates) followed by Penicillium (94 isolates) and Fusarium (52 isolates). The less predominant genera include Rhizopus (14 isolates) and the Alternaria (9 isolates). Aspergillus flavus and A. parasiticus occurred in 53 and 44% of the samples, respectively, with higher frequencies in maize than peanuts or beans and absent in rice, pumpkin seed and cassava products. Aspergillus fumigatus was detected in 20% of samples and A. niger in 18% of the samples. Aspergillus isolated less frequently included A. carbonarius A. awamori, A. oryzae and A. tamarii, A. pseudotamarii, A. ochraceus, A. ostianus, A. avenaceum, A. oryzae and A. variabile. Consistent results were observed for A. tamarii, A. pseudotamarii, A. ochraceus and A. ostianus with respect to substrate specificity. While A. tamarii, A. pseudotamarii and A. ochraceus were isolated only from peanuts, A. ostianus strains occurred only in bean samples. Penicillium contamination was dominated by P. polonicum and P. crustosum with incidence rates of 43 and 41%, respectively, with highest contamination levels registered in samples from Yaounde. Penicillium citrinum, P. purpurogenum, P. islandicum, P. aurantiogriseum, P. expansum were also inconsistently isolated from food samples. There was a relatively low incidence of Penicillium spp. in pumpkin seed and fermented cassava product samples.