【作者】 齐德生；

【导师】 刘凡；

【作者基本信息】 华中农业大学 ， 土壤学， 2004， 博士

【摘要】 黄曲霉毒素能造成动物急慢性中毒并具有强致癌性，是已知对人畜健康危害最为严重的霉菌毒素之一。它可存在于粮食、饲料和土壤中，饲料中的黄曲霉毒素能在畜产品中残留，因此，如何消除黄曲霉毒素的潜在威胁是当前饲料卫生领域研究的热点。蒙脱石性质稳定，作为霉菌毒素的结合剂在工业化大规模饲料生产中呈现出良好应用前景。本研究通过等温吸附与解吸、透析、离体肠囊、急性小鸭毒性、肉仔鸡饲养试验和X-射线衍射分析、红外光谱分析等，研究了蒙脱石和改性蒙脱石对黄曲霉毒素B₁（AFB₁）、赖氨酸、蛋氨酸及维生素B2的吸附特性，评价了它们在动物体内对黄曲霉毒素B₁的脱毒效果和对动物健康与生产性能的影响，探讨了它们对黄曲霉毒素B₁的吸附机制。主要研究结果如下： 1 蒙脱石及改性蒙脱石对AFB₁的吸附曲线符合Langmuir和Freundlich方程。在pH2.0及pH8.0下，前者的最大吸附量分别为613.5μg／g和628.9μg／g；后者的最大吸附量分别为598.8μg／g和625.0μg／g。蒙脱石与改性蒙脱石对AFB₁的吸附量无明显差别，但改性蒙脱石吸附的AFB₁解吸率较低，可见，蒙脱石经适当改性后可获得更好的吸附脱毒效果。 2 按猪禽配合饲料中合成赖氨酸一般添加水平，在吸附反应体系中添加0.2％合成赖氨酸，不影响蒙脱石及改性蒙脱石对AFB₁的吸附。 3 蒙脱石和改性蒙脱石吸附AFB₁后，其红外光谱中1403cm^-1和1355cm^-1吸收峰消失。说明蒙脱石和改性蒙脱石对AFB₁存在化学吸附，其选择性吸附机制可能主要是由于它们边缘的羟基与AFB₁之间形成了双氢键。 4 蒙脱石和改性蒙脱石对AFB₁吸附的初始反应属于一级动力学反应，20min后吸附达到平衡。在反应初始阶段，AFB₁含量的半衰期为14.4—16.7min。这一结果对将蒙脱石和改性蒙脱石用于对抗AFB₁的急性毒性作用和用作饲料生产中的霉菌毒素脱毒剂都有重要参考价值。 5 AFB₁标样溴化钾压片的最大红外吸收峰为1749cm^-1，其后依次为1589cm^-1、1479cm^-1、1621cm^-1、1548cm^-1、1126cm^-1、1425cm^-1、1066cm^-1。 6 蒙脱石及改性蒙脱石对赖氨酸和维生素B2有一定的吸附性。在溶液pH 2.0和8.0时，蒙脱石的赖氨酸最大吸附量分别为64.1mg／g和49.3mg／g；改性蒙脱石的赖氨酸最大吸附量分别为45.4mg／g和33.8mg／g。它们对维生素B2的吸附符合Nernst模型，即吸附量与溶液中维生素B2的浓度呈直线相关。蒙脱石对赖氨酸及维生素B2的吸附量较改性蒙脱石的大。在蛋氨酸含量低于0.2％时，它们对蛋氨酸均不吸附。 赖氨酸、维生素B2被它们吸附后可被水解吸。在本试验条件下，即分别在pH2.0及pHS.o环境下吸附后，再用pHS.O的水解吸时，蒙脱石表面赖氨酸的解吸率分别为0.3%和20.8%，改性蒙脱石的解吸率分别为38.7%和25.2%;蒙脱石吸附维生素B2的解吸率分别为79.3%和44.6%，改性蒙脱石的解吸率分别为89.2%和51.9%。改性蒙脱石对赖氨酸和维生素B2的吸附量较蒙脱石小，而解吸率较蒙脱石大，可见，蒙脱石经适当改性后能获得更理想的物化性能，应用价值提高。 7体外离体肠囊试验显示，动物肠道有主动吸收AFB，的过程，且该过程不影响蒙脱石及改性蒙脱石对AFB;的吸附。 8体内试验结果表明，蒙脱石及改性蒙脱石能阻止动物对AFB:的吸收、对抗舫Bz对动物的急慢性毒性作用、减少动物急性中毒死亡率，恢复动物生产性能。 在肉鸡日粮中添加0 .5%的蒙脱石或改性蒙脱石对鸡骨骼强度无不良影响，对鸡骨骼钙、磷、铜、铁、锌沉积无影响;使骨骼铅、氟沉积减少，有利于预防动物铅中毒、氟中毒和提高畜产品品质，但同时也使骨骼的锰含量降低，生产中应注意补充。 本研究的创新点主要有: 1系统研究了蒙脱石对黄曲霉毒素B:的吸附特性及其影响因素，测定出了蒙脱石对黄曲霉毒素Bl的最大吸附量;对蒙脱石作了季按盐改性处理并证明改性后其对黄曲霉毒素B;和营养成分的吸附特性更符合生产需要。 2探索了蒙脱石对黄曲霉毒素B，的吸附机制，提出了蒙脱石边面的硅醇基、铝醇基与黄曲霉毒素B;间形成的双氢键是蒙脱石对黄曲霉毒素B:选择吸附的重要机制之一。 3首次用离体肠囊试验和透析袋试验，研究了肠道吸收过程和肠内容物对蒙脱石吸附黄曲霉毒素B:效果的影响，并发现了动物肠道对AFB:有主动吸收。综合体外、离体器官和动物体内试验，证明蒙脱石对APB:有脱毒效果。关键词:蒙脱石;黄曲霉毒素B、;吸附机制;肠囊;鸭雏;肉仔鸡;脱毒更多还原

【Abstract】 Aflatoxins were widespread contaminants of foods, feeds and soil ,which could result in a variable toxicosis from death to adverse effects on productivity and health of host consuming contaminated diets ,depending on their concentration . They were among the most potent hepatocarcinogens and their high toxicity to both animals and humans made them the most dangerous known mycotoxins. The most toxic aflatoxin has been designated aflatoxin B₁（AFB₁） and its toxic metabolite could residue in animal products. Consequently, how to alleviate the toxicity of AFB₁ had become the highlight in the area of feed science . Montmorillonite was stability with chemical characteristic and had great specific surface area and high adsorption ability ,which implied a good prospect of montmorillonite utilized as mycotoxin adsorbents in feed. The objective of this study were to investigate the adsorptive properties of AFB₁, lysine （Lys）, methionine （Met）, vitamin B2 （VitB2）, on montmorillonite and modified montmorillonite, inspect the detoxify effect of montmorillonite and modified montmorillonite for AFB₁ in animals , and explore the mechanism of AFB₁ adsorption on them by isothemal adsorption experiment , desorption experiment, everted small intestine sack experiment, acute toxicity experiment with duckling and chronic toxicity experiment with broiler , X-ray diffraction and infrared absorption spectrum. The main results of the study were as following.1 The isothermal adsorption of AFB₁ on montmorillonite and modified montmorillonite was fitted by Langmuir and Freundlich equation. The maxium amount of AFB₁ adsorbed on montmorillonite was 613.5 and 628.9 礸/g at pH 2.0 and pH8.0 respectively, and that on modified montmorillonite was 598.8 and 625.0 礸/g, respectively. There was no significantly different for the the maxium adsorption between montmorillonite and modified montmorillonite, but the desorbing rate of the latter was lower than the former. This results indicated that montmorillonite could get better detoxification effect for AFB₁ after modified treatment.2 The level of Lys added in formula feed was about 0.2%, and Lys of the ratio did not affect the adsorption of AFB₁ on montmorillonite and modified montmorollonite.3 The infrared absorption bands at 1403cm^-1 and 1355cm^-1 of montmorillonite and modified montmorillonite were weaken or disappeared after AFB₁ was adsorbed ,which indicated mat the chemical adsorption existed. The main chemical mechanism of the adsorption was the formation of double hydrogen bands between AFB₁ and montmorillonite or modified montmorillonite.4 The adsorption reaction of AFB₁ on montmorillonite and modified montmorillonite was described by the first order reaction,the half time of AFB₁ disappeared ranged from 14.4 to 16.7 min in initial stage of the reaction. The adsorption reaction reached balance after 20 min.5 The bigest infrared absorption band of AFB₁ in a thin KBr disk prepared under high pressure was 1749cm^-1, the sequence after 1749cm^-1 were 1589 cm^-1,l479 cm^-1,1621 cm^-1, 1548 cm^-1, 1126 cm^-1,1425cm^-1, 1066 cm^-1.6 The maximum amount of Lys adsorbed on montmorillonite was 64.1mg./g and 49.3mg/g at pH2.0 and pH8.0 respectively ,and the maximum amount of lysine adsorbed on modified montmorillonite was45.4mg/g and 33.8mg/g respectively. Met was not adsorbed on montmorillonite and modified montmorillonite as the concentration of was lower than 0.2%.The isothermal adsorption of vitamin B2 on montmorillonite and modified montmorillonite was fitted by the Nernst model .Lys and VitB2 could be desorbed from adsorptive complex partially. The adsorption amount of Lys and VitB2 on montmorillonite was more than that on modified montmorillonite, but their desorbing rate from montmorillonite adsorptive complex was less than that from modified montmorilloniteadsorption complex.These results showed that the adsorptive characteristic of montmorillonite could be improved by modified treatment.7 There was a active assimilation mechanism of aflatoxin B₁ in chick small更多还原