Study On The Detoxification Of Zearalenone By Candida Parapsilosis

Zearalenone(ZEN,ZEA),also known as F-2 mycotoxin,mainly produced by Fusarium species in many grains and their by-products worldwide,such as corn,wheat and sorghum.ZEN causes reproductive disorders and hyperestrogenic syndromes in animals and humans due to its xenoestrogenic effects.Thus effective methods of ZEN detoxification are urgently needed.Recently,biological approach for ZEN detoxification is being explored.Among them,based on the catalytic action of degrading enzyme,the biotransformation method of oriented converting ZEN into low-toxic metabolites has become the focus.The toxicity of main derivatives of ZEN is ranked as follows: ?-Zearaleno L(?-ZOL)> ?-Zearalanol(?-ZAL)> ?-Zearalanol(?-ZAL)> Zearalanone(ZAN)> ZEN > ?-Zearalenol(?-ZOL),which often coexist with ZEN in crops and make the risk of mycotoxin contamination increasing.This study aimed to screen out the specific microorganism that can efficiently catalyze directional reactions to produce less toxic or non-toxic products based on the structure of ZEN and the toxicity of its known products.Yeast was selected from the microorganisms reported to catalyze the orientation of ZEN by carbonyl reduction and glycosylation.The detoxification of ZEN was study,including product analysis and the possible mechanisms involved.The specific results are as follows:In this study,one promising strain,Candida.parapsilosis PRG501 with high reductase activity was evaluated for its ability to directly convert ZEN to less toxic ?-ZOL.The results showed that the degradation rate of ZEN(20 ?g/m L)was 79.37%,when it incubated with whole cells within 24 h at 30°C,38% of ZEN is converted into ?-ZOL,and about 20% of ZEN was adsorbed.And the degradation rate of ZEN by the culture supernatant was only 16.92%.The mechanisms involved in the degradation of ZEN by C.parapsilosis PRG501 may be the production of associated intracellular enzyme,which have the ability to degrade ZEN.In this study,different concentration of glucose and sucrose were added to trigger ZEN glucosylation by C.parapsilosis PRG501.When glucose was at the concentration of 20 mg/m L,the conversion efficiency of ZEN was the highest,and C.parapsilosis PRG501 could catalyze the conversion of ZEN to 80% ZEN-glycosides and 10% ?-ZOL within 5 hours.After 12 h,ZEN were completely converted.Nuclear Magnetic Resonance(NMR)analysis revealed that C14 and C16 positions of the benzene ring of ZEN were combined with a molecule of glucose respectively to generate ZEN-14,16-di G,which was stable under digestive conditions.Furthermore,C.parapsilosis PRG501 cell fragments have a greater glycosylation catalytic ability for ZEN than cell-broken intracellular extracts,which is equivalent to the catalytic conversion rate of whole cells,indicating that enzyme may be on the cell membrane or cell wall.In addition,C.parapsilosis PRG501 also exhibited glucosyltransferase activities toward ?-ZOL,?-ZOL and ZAN with yields of 98%,76%,and 99%,respectively.In this study,the estrogenic effects of ZEN and its conversion products were explored based on molecular docking technology.The binding energy of ZEN-14,16-di G and ?-ZOL to estrogen receptors was higher than that of ZEN,and the affinity were lower,indicating that the products show weaker estrogen toxicity.The proliferation experiment of human breast cancer cell MCF-7 showed that the cell proliferation rate of ZEN to MCF-7 was 110.27% at low concentrations,and that of ZEN-14,16-di G and ?-ZOL to MCF-7 were 86.49% and 97.59%,respectively.Both of them could inhibit the normal cell proliferation.Compared with promotion of ZEN to MCF-7 proliferation,the estrogen toxicity of the products was significantly reduced.The results of this study are conducive to the effective detoxification of ZEN,which will lay the foundation for technical research to reduce the estrogen toxicity of ZEN,and open a new situation for the further development and application of ZEN biodegradation technology in cereals and feed.