香草兰发酵菌群结构解析及其调控香兰素生成的机制研究

Vanilla is a tropical cash crop, and their cured beans were the valuable spices. Vanillin is one of the most important odor components and the content of vanillin is regulated by both enzymes and microbes. The profile of microbes on the surface of the beans is greatly affected by the surrounding environment. However, it remains unclear about the composition characterization of microbes on the beans and their effect on the production of vanillin under Hainan regional climates. The present study focuses on the variation of vanillin and glycosidically-bound vanillin, as well as the microbial profile and gene expression at different stages of fermented beans. The correlation relationship between microbial composition and vanillin production was assessed to understand the biological function of microbial ecological system on the surface of beans.The key microbial strains involved in the production of vanillin were separated and their function was identified by the classical characteristics, phylogenetic results, physiological and biochemical data. On the basis of the enzyme activity and properties, the strains with key regulatory enzymes were selected, and introduced into the beans to verify their effect on vanillin formation. The effects of abiotic factors, such as temperature, humidity, oxygen and light, on the fermentation of key microbial strains and the production of vanillin were investigated. Through these work, the mechanism of microbial ecological system regulating vanillin formation will be dissected, and vanilla curing method will be improved.

香草兰是典型的热带经济作物，其豆荚经发酵后成为名贵香料，香兰素是最主要的呈香物质，其含量受豆荚酶系和发酵微生物的共同调节。而豆荚表面发酵微生物菌群结构形成受环境条件的显著影响，目前关于海南气候条件下香草兰发酵微生物菌群结构特点及其对香兰素生成的调节作用尚不清楚。本研究拟选取不同发酵阶段的香草兰豆荚，分析香兰素及其糖苷物以及豆荚发酵微生物菌群结构的动态变化，确定与香兰素生成正相关的关键菌株，研究关键菌株的生物学功能，阐明关键菌株参与香兰素生成的作用通路、方式及机制；对关键菌株采用经典分类学方法，结合系统发育学分析、生理生化分析鉴定关键菌株的分类学地位；探究非生物因素对关键菌株发酵行为及香兰素生成的影响；从而阐明香草兰发酵过程豆荚微生态系统中关键菌株调控香兰素生成的机理，为香草兰优质高效发酵提供科学依据。

香草兰是典型的热带经济作物，其豆荚经发酵后成为名贵香料，香兰素是最主要的呈香物质，其含量受豆荚酶系和发酵微生物的共同调节。而豆荚表面发酵微生物菌群结构形成受环境条件的显著影响，目前关于海南气候条件下香草兰发酵微生物菌群结构特点及其对香兰素生成的调节作用尚不清楚。. 本研究选取不同发酵阶段的香草兰豆荚，分析香兰素及其糖苷物以及豆荚发酵微生物菌群结构的动态变化，确定与香兰素生成正相关的关键菌株，研究关键菌株的生物学功能，阐明关键菌株参与香兰素生成的作用通路、方式及机制；对关键菌株采用经典分类学方法，结合系统发育学分析、生理生化分析鉴定关键菌株的分类学地位；探究非生物因素对关键菌株发酵行为及香兰素生成的影响；从而阐明香草兰发酵过程豆荚微生态系统中关键菌株调控香兰素生成的机理。. 项目解析了豆荚发酵生香过程中微生物演替特征，明确了芽孢杆菌及其所产葡萄糖苷酶在香兰素生物合成中的重要贡献，修正了前人认为内源葡萄糖苷酶转化香兰素葡萄糖苷决定香荚兰豆荚品质的学术假说；从发酵豆荚分离到51 株芽孢杆菌，发现新种Bacillus vanillea sp. nov.，其可产生β-D-葡萄糖苷酶参与香兰素葡萄糖苷水解，生成香兰素；构建芽孢杆菌复合菌系，优化发酵豆荚特征菌群，结合单元式热空气发酵技术，香兰素产量达国际领先水平，验证了功能菌株调控豆荚发酵生香提升品质的新理论。