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Detoxification of Deoxynivalenol by a Soil Bacterium Devosia mutans 17-2-E-8

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Title: Detoxification of Deoxynivalenol by a Soil Bacterium Devosia mutans 17-2-E-8
Author: He, Jian Wei
Department: School of Environmental Sciences
Program: Environmental Sciences
Advisor: Boland, Greg J.Zhou, TingSibley, Paul K.
Abstract: The mycotoxin deoxynivalenol (DON) remains an important challenge in many regions in the world. Microbial detoxification of DON represents a new approach to treating DON-contaminated grains. A bacterial isolate identified as Devosia mutans 17-2-E-8, which showed a high similarity in 16sRNA gene sequence to the Devosia genus, was isolated from an alfalfa soil sample that was enriched for six weeks with Fusarium graminearum-infested corn. D. mutans 17-2-E-8 was capable of reducing DON concentration in liquid corn meal medium up to 100% after incubation at temperatures ranging from 15-37 ºC, and pH levels ranging from 6-8 for 48-72 h under aerobic conditions. The major transformation product was purified by high-speed countercurrent chromatography (HSCCC), and characterized as 3-epi-DON by liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR). A minor product, 3-keto-DON, was also detected in the bacterial incubation medium. The cytotoxicity IC50 values of 3-epi-DON and 3-keto-DON were, respectively, 357 and 3.03 times higher than that of DON based on an MTT bioassay assessing cell viability, and were, respectively, 1181 and 4.54 times higher than that of DON based on a BrdU bioassay assessing DNA synthesis. Toxicological effects of 14-day oral exposure of the B6C3F1 mouse to DON and 3-epi-DON were also investigated. Overall, there were no statistically significant differences between the control and the 25 mg/kg bw/day or 100 mg/kg bw/day 3-epi-DON treatments in body and organ weights, haematology and organ histopathology. However, in mice exposed to DON (2 mg/kg bw/day), white blood cell numbers and serum immunoglobulin levels were altered relative to controls, and lesions were observed in adrenals, thymus, stomach, spleen and colon. It was concluded that 3-epi-DON was at least 50 times less toxic than DON in the B6C3F1 mouse. The reduced toxicity was achieved through epimerization by the bacterial isolate, and provides a new DON detoxification pathway. Further investigation will assess practical applications for detoxification by epimerization in treating contaminated feed and food matrices.
Date: 2015-06
Rights: Attribution-NonCommercial-NoDerivs 2.5 Canada
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Attribution-NonCommercial-NoDerivs 2.5 Canada Except where otherwise noted, this item's license is described as Attribution-NonCommercial-NoDerivs 2.5 Canada