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Understanding of deoxynivalenol detoxification through epimerization by Devosia mutans 17-2-E-8

Zhou, T. 2017. Understanding of deoxynivalenol detoxification through epimerization by Devosia mutans 17-2-E-8. International Seminar of Basic Techniques on Grain Storage and Transportation. May 20, Changchun, China.

Abstract

Enzymatic detoxification of deoxynivalenol (DON) is a promising mitigation strategy for the contamination of cereal grains with this mycotoxin. A recently described bacterium Devosia mutans, which is capable of transforming DON into non-toxic stereoisomer 3-epi-DON, is opening the doors for the development of such applications. Earlier observations suggested that the epimerization proceeds via a two-step process with 3-keto-DON as an intermediate. To test the hypothesis, 3-keto-DON was chemically synthesized and incubated with cell-free lysate of Devosia mutans 17-2-E-8. Protein fraction enriched by ammonium sulfate precipitation at 35- 55% saturation selectively reduced 3-keto-DON to 3-epi-DON but DON was not epimerized, showing that the enzymatic steps involved were physically separated. The reduction of 3-keto- DON by cell-free protein extract of D. mutans required NADPH. Seven Devosia species reduced 3-keto-DON to 3-epi-DON but only cultures of D. mutans were able to epimerize DON. The epimerization was suppressed in media with a high concentration of glucose, sucrose, starch, ammonium salts or urea. The nature of the epimerizatioin suggests that the process can be optimized and exploited for the development of feed additives and/or genetically engineered crops in order to reduce foodborne exposure of consumers and farm animals to DON.

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