降解玉米赤霉烯酮菌株的筛选、降解机制及特性研究

Screening, Degradation Mechanism and Characteristics of Strains Degrading Zearalenone

玉米赤霉烯酮(Zearalenone,ZEN)是一种易于污染谷物和饲料的雌激素类真菌毒素,严重危害人类和动物健康。采集霉变饲料、土壤等样品,以ZEN为唯一碳源的培养基进行初筛,采用ELISA法筛选对ZEN的降解能力较强的菌株。采用形态学和分子生物学方法对菌株进行鉴定。对菌株的菌体、上清液、细胞内容物分别进行降解实验,探讨其降解机制。研究不同温度、pH、接种量和时间对菌株降解效率的影响。接种到污染ZEN(1μg/mL)的原料,评价筛选菌株对原料中ZEN的降解效率。通过小白鼠攻毒实验评价菌株的安全性。结果表明,从96个分离菌株中筛选出1株ZEN降解能力较强的菌株G-6,最高达到81.19%。菌株为G+,呈杆状,中等大小,能够形成芽孢。16S rDNA序列分析表明G-6和解淀粉芽孢杆菌的亲缘关系最近。不同成分降解实验表明该菌株主要是通过细胞分泌的胞外酶降解ZEN。菌株G-6最佳降解ZEN的条件为:温度37℃,pH5.0,接种量3%,培养时间72 h。样品毒素降解实验证明菌株均能100%降解可溶性淀粉、玉米粉、豆粕粉中的ZEN。小白鼠实验结果表明该菌株不具致病性,是一种安全菌株。

Zearalenone(ZEN)is a kind of estrogenic mycotoxin which is easy to contaminate grain and feed,causing serious harm to human and animal health.Samples of moldy feed and soil were collected and screened with ZEN as the sole carbon source.The strains with strong ability to degrade ZEN were screened by ELISA method.The strains were identified by morphological and molecular biological methods.The degradation experiments were carried out on the cell,supernatant and cell contents of the strain,and the degradation mechanism was discussed.The effects of different temperature,pH,inoculum amount and time on the degradation efficiency of the strain were studied.The strain was inoculated into the raw material contaminated with ZEN(1μg/mL),and the degradation efficiency of ZEN in the raw material was evaluated.The safety of the strain was evaluated by mouse challenge test.The results indicated that one strain G-6 with strong ZEN degradation ability was selected from 96 isolated strains,and the highest was 81.19%.The strain was G+,rod-shaped,medium-sized and capable of forming spores.16s rDNA sequence analysis indicated that G-6 had the closest genetic relationship with Bacillus amylolyticus.The degradation tests of different components indicated that the strain degraded ZEN mainly through extracellular enzymes secreted by cells.The optimum conditions for the degradation of ZEN by strain G-6 were as follows:temperature of 37℃,pH of 5.0,inoculum of 3%,culture time of 72 h.The toxin degradation test of the sample indicated that the strain could degrade ZEN in soluble starch,corn meal and soybean meal.The results of mouse test indicated that the strain was not pathogenic and the strain was a safe strain.