Study Of Detoxification Of Zearalenone By Bacillus Spp.

Zearalenone (Zearalenone, ZEN) is a mycotoxin mainly produced by Fusariumwhich widely present in cereals and cereal products. ZEN is an estrogen analogue, with avariety of toxicity leading estrogen hyperthyroidism, infertility or miscarriage in animals,and is a threat to health of animals and human.In this paper we got four strains of bacteria with ZEN detoxification ability throughscreeming. We further studied their mechanisms of detoxification, detoxification relatedfactors and ability of detoxifying other toxins.Through screening, four strains of bacteria were isolated and purified from moldycorn and soil tillage layers. The strains had strong and stable ZEN detoxification capacity.After16S rDNA sequencing and comparing with Genbank database, the four strains wereidentified as genus Bacillus, and named as Bacillus sp. LY5-20，Bacillus sp. LY5-28，Bacillus sp. LY6-5，and Bacillus sp. LY6-15. Within24hours culture at30℃, the strainsremoved96.9%,95.0%,98.0%and95.8%of ZEN from the solution with2μg/ml ZEN.The ZEN detoxifying mechanisms were studied, the results indicated thathigh-temperature-inactivated strains dicreased detoxification ability significantly, whichwere31.2%,29.5%,38.5%,34.6%, respectively. The precipitation of bacterial cell lysisalso had detoxification capacity, which could remove37.6%,54.4%,47.1%and55.1%of ZEN in the reaction system. The data indicated that cell wall of all the four strains hadZEN adsorption capacity. In addition, ZEN scavenging ability of supernatant from LBbroth culturewere detected, Bacillus sp. LY5-20, LY5-28, LY6-5, and LY6-15showed98.6%,100%,92.2%,85.3%of ZEN removing capability. The results indicated that fermentation supernatant contained degrading enzymes which were capable of degradingmost of ZEN in the solution, and the ZEN degrading enzymes were extracellular enzyme.The effects of different culture conditions on ZEN detoxification by LY5-20,LY5-28, LY6-5, LY6-15were studied. The results showed that the increasingconcentration of bacterial suspension obviously played an important role on promotingZEN detoxification effect. The four strains were not sensitive to temperature ranging20-42℃. When temperature rose to50℃, the detoxification ability of LY5-20, LY6-5and LY6-15went down to40%-54%, indicating that their degrading enzymes wereinhibited by50℃; while the strain LY5-28were not impacted in50℃. Alkalineconditions were better for ZEN detoxification. LY5-20, LY5-28, LY6-5had bestdetoxification efficiency at pH9, and LY6-15had best detoxification efficiency at pH7.EDTA is capable of binding metal ions and thereby inhibiting the activity of mentalenzymes. After adding EDTA, a significant decline in detoxification ability of thesestrains was observed, indicating metal enzymes were involved in the detoxificationprocess.Deoxynivalenol (DON) and ochratoxin A (OTA) were also common mycotoxins incereals. After cultured with DON or OTA, the strains could remove only12%-20%of thetoxins, and little significant differences were observed in high-temperature-inactivatedcells. These indicated that the detoxification of DON and OTA mainly depended onadsorption, and the four strains could not biodegrade OTA and DON.