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Activités de biotransformation et de séquestration des fusariotoxines chez les bactéries fermentaires pour la détoxification des ensilages de maïs

Abstract : The contamination of silages by fusariotoxins takes place in the field, independantly from any problem of conservation. Ingestion by livestock of silage with high concentration of these mycotoxins can cause a reduction of performances and affects animal health. Due to the partial efficiency of preventive measures and the inadaptability of physical and chemical detoxification, the use of biological detoxification methods seems a valid alternative to explore. The objective of this work was to test the ability of fermentative bacteria to remove fusariotoxins. The screening of 202 strains of fermentative bacteria for their ability to biotransform and/or bind deoxynivalenol (DON), zearalenone (ZEN) and fumonisins B1 and B2 (FB1 and FB2) showed that binding of these major fusariotoxins is widespread in these microorganisms. The genera Streptococcus and Enterococcus were the most effective with up of 33%, 49%, 24% and 62% of DON, ZEN, FB1 and FB2 bound, respectively. This property could decrease bioavailability of ingested fusariotoxins in animals and, thus effectively reducing their toxicity. In addition, about 5% (11/202) of tested strains biotransformed ZEN into its activated form, zearalenol. The binding interaction was further studied in FB, I showed that peptidoglycan from bacterial cell wall is likely the binding site of FB1 and FB2 which are bound by their tricarballylic acid chains (TCA). The large difference in binding observed with these two analogues (FB2 > FB1) was elucidated by molecular modelling that showed that the additional hydroxyl group in FB1 form an hydrogen bond with one TCA decreasing the binding property. Experiments showed that a large fraction of ZEN can also be bound instantaneously by ruminal fluid, forming a complex that, under conditions simulating the abomasum and small intestine, was as stable as that formed between Streptococci and ZEN. This binding by ruminal fluid could contribute to the resistance of ruminants to the effects of fusariotoxins. The use of fermentative bacteria to reduce toxicity could be more useful in monogastric animals like pig. However, in vivo studies are needed to evaluate the real impact of this technology. At term, the ability of fermentative bacteria to bind fusariotoxins could advantageously supplement the acidifying or probiotic properties of bacterial inoculants used in animal nutrition.
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Submitted on : Friday, July 13, 2012 - 2:56:16 PM
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Vincent Niderkorn. Activités de biotransformation et de séquestration des fusariotoxines chez les bactéries fermentaires pour la détoxification des ensilages de maïs. Biologie végétale. Université Blaise Pascal - Clermont-Ferrand II, 2007. Français. ⟨NNT : 2007CLF21729⟩. ⟨tel-00717731⟩

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