Effet chez le porcelet d'une exposition à un régime co-contaminé en ...

INTRODUCTIONII. BIOLOGICAL DETOXIFICATIONEnzymatic or microbial degradation of mycotoxins (“biotransformation”) leading to less- or evennon-toxic metabolites has already been a subject of research for more than 40 years as this strategyis a quite attractive method for the decontamination of crops. Microorganisms including yeast,moulds and bacteria have been screened for their ability to modify or inactivate differentmycotoxins. Only a few microorganisms with respective activity were isolated, the first wasFlavobacterium aurantiacum with the ability to detoxify aflatoxins (Ciegler et al., 1966). Thisorganism has since then been studied extensively for possible degradation products (Bata andLasztity, 1999). Apart from F. aurantiacum, a number of bacterial and especially fungal species havebeen found to detoxify aflatoxins (Karlovsky, 1999). Rhizopus sp. has been claimed to be particularlysuitable for large-scale detoxification of aflatoxin-contaminated feeds by solid-state fermentation(Knol et al., 1990, as cited by Karlovsky, 1999).Ochratoxin A is rapidly degraded by micro-organisms in the rumen to ochratoxin α (OTα) andphenylalanine (Hult et al., 1976; Kiessling et al., 1984). Wegst and Lingens (1983) proved degradationof OTA by the aerobic bacterium Phenylobacterium immobile. Cheng-An and Draughon (1994) havescreened bacteria, yeast and moulds for their ability to detoxify ochratoxin A and foundAcinetobacter calcoaceticus to be able to degrade OTA in an ethanol-containing medium. Differentstrains of Lactobacillus, Bacillus and Saccharomyces have also been shown to degrade ochratoxin A invitro to varying degrees up to 94 % (Böhm et al., 2000). The same strains were also tested fordegradation of trichothecenes, but with less success. Styriak et al. (2001) showed partial degradationof ochratoxin A, nivalenol, deoxynivalenol, zearalenone and fumonisins by yeast strains.A yeast strain isolated from the hindgut of a termite and identified as a member of the genusTrichosporon showed a potential deactivation of both, OTA and ZEA, in animal feeds (Molnar et al.,2004; Schatzmayr et al., 2006). Due to the yeast’s main property to degrade mycotoxins this strainwas named T. mycotoxinivorans (lat. vorare = degrade). The yeast detoxifies OTA by cleavage of thephenylalanine moiety from the isocumarin derivate ochratoxin α (OTα). This metabolite has beendescribed to be nontoxic or at least 500 times less toxic than the parent compound (Bruinink et al.,1999; Schatzmayr et al., 2003). Feeding trials with the aim to test the efficacy of T. mycotoxinivoransto suppress ochratoxicosis proved that the dietary inclusion of this yeast blocks ochtratoxin-inducedimmune suppression in broiler chicks (Politis et al., 2005; Binder, 2007). More recently, a feeding trialwith broiler chicks was performed in order to evaluate the toxic effects of OTA and attenuatingeffects of a commercial toxin deactivator containing the yeast Trichosporon mycotoxinivorans onperformance parameters, serum enzymes and clinic-pathomorphology of internal organs.84