双功能寡养单胞菌CW117降解黄曲霉毒素B1和赭曲霉毒素A的生物机制

Aflatoxin B1 and ochratoxin A are a group of highly toxic secondary metabolites, which mainly produced by Aspergillus and Penicillium strains. Two mycotoxins are the most hazardous and widely contaminated toxins in agro-products and processed food. Mycotoxins detoxification study is much important to agricultural production and food safety. Biodetoxification method developed fast in recent years due to the various merits. However, the intensive mechanisms of biodetoxification are undering the development. Stenotrophomonas sp. CW117, an efficient and difunctional degrading bacterium of AFB1 and OTA, was screened and selected as the experimental subject in the present project. The cluster of degrading and regulation genes, the key degrading enzymes and two mycotoxins metabolic pathways are going to be cloned and characterized from the strain CW117 by using the protocols of modern molecular and biochemical methods. Furthermore, the biological characteristics of the key degrading enzymes and the enzymatical specificity to other structure mycotoxins are furhter investigated. Based on the results of the degrading gene cluster (including degrading and regulation genes), the characteristics of key degrading enzymes and the metabolic pathways, the biological degradation mechanism of the bacterial strain CW117 will be explored, and the biodetoxification values of the difunctional strain are going to envaluated for the potential use in agricultural products and processed food.

黄曲霉毒素B1（AFB1）和赭曲霉毒素A（OTA）是由曲霉和青霉菌产生的一类次生代谢产物，毒性巨大，在农产品与加工食品中污染广泛。利用微生物方法对AFB1和OTA进行降解脱毒对农业生产和食品安全意义显著。然而，其系统的生物降解机制研究还有待突破，尤其是对两类毒素双功能降解机制探索尚未见报道。鉴于此，本项目以前期筛选得到的AFB1和OTA双功能降解菌寡养单胞菌CW117为研究对象，拟通过基因组和转录组学等技术，克隆AFB1和OTA降解代谢过程中的降解酶基因及调控因子，揭示其降解代谢路径；探明降解关键酶酶学特征及其对其它化学结构曲霉毒素降解偏好性。从降解代谢基因组成及功能、关键酶和代谢路径角度，揭示以菌株 CW117为代表的细菌降解两类曲霉毒素的生物学机制，为曲霉类真菌毒素污染的高效生物脱毒方法研发提供重要理论基础。

黄曲霉毒素B1（AFB1）和赭曲霉毒素A（OTA）是由曲霉属和青霉属真菌产生的一类次生代谢产物，毒性巨大，在农产品与加工食品中污染广泛。利用微生物方法对AFB1和OTA进行降解脱毒对农业生产和食品安全意义显著。本项目以生物富集方法筛选得到的AFB1和OTA双功能降解菌寡养单胞菌CW117，对该菌株生物分类学地位，菌株对AFB1和OTA降解特性进行了详细的探讨。在此基础上，通过生物组学和分子遗传学等技术，对菌株CW117降解AFB1和OTA代谢过程中的降解基因及调控因子，进行了进一步的探索，初步探明了寡养单胞菌CW117对两类毒素降解代谢的生物机制。研究发现，菌株CW117对OTA的降解属于酰胺酶ADH3特异性酶促降解，其降解产物为赭曲霉毒素α和L-β-苯丙氨酸；菌株CW117对AFB1的降解属于单加氧酶HPPD介导生成的小分子氧化物非特异性降解作用。该研究结果显示，同一菌株对不同的曲霉毒素具有完全不相同的降解作用机制，微生物对各类霉菌毒素的降解机制有多样性特征。本研究从降解代谢基因组成及功能、关键酶和代谢方式的角度，揭示了以菌株 CW117为代表的细菌，降解两类曲霉毒素的生物学机制，为曲霉类真菌毒素污染的高效生物脱毒方法研发积累了理论基础。