黑孢块菌液体深层发酵产香机理

Aroma is an important characteristic for the flavor of fermented food. The aroma is contributed by the comprehensive action of the dozens or even hundreds of aroma-active compounds. During the submerged fermentation process of fermented food, the aroma-producing of microbiology play a key role in the formation of aroma. However, the aroma-producing mechanism is still unclear. Tuber melanosporum, the precious edible mushroom originated from France, is highly appreciated due to its unique and characteristic aroma. By taking T. melanosporum as a typical example of aroma-producing microbiology, this project is to study the aroma-producing mechanism during its submerged fermentation process. Firstly, gas chromatography-olfactometry (GC-O) will be used to screen the aroma active compounds, and then the significance of aroma active compounds on the original aroma will be investigated by aroma reconstitution and omission experiments. Secondly, gene expression profiles will be employed to screen the genes related to the biosynthesis of aroma active compounds, and then the metabolic network of aroma active compounds will be constructed by gene function enrichment analysis. Finally, based on the gene expression response to environmental stimulation, the metabolic flux of aroma active compounds biosynthesis will be analyzed to study the response mechanism of metabolic network to fermentation environment. The expected results will elucidate the aroma-producing mechanism during the submerged fermentation process of T. melanosporum, and also should be useful for the control of the aroma of fermented food during the submerged fermentation process.

香味是构成发酵食品风味特色的重要因素，发酵食品的香味是由数十种乃至上百种香味活性物质协同作用而形成的，微生物发酵产香过程直接决定发酵食品的香味，而目前微生物发酵产香机理的研究相当匮乏。黑孢块菌是一种原产自法国的名贵食用菌，以其浓郁而独特的香味成为研究热点。本项目拟以课题组首创的黑孢块菌液体深层发酵过程为典型模型，研究微生物发酵产香机理。首先，利用GC-O嗅辩筛选出香味活性物质，再利用香味活性成分重构和缺失的方法评价香味活性物质对香味形成的影响规律；然后，通过解析基因表达谱筛选出香味活性物质生物合成基因，通过基因功能富集分析构建香味活性物质生物合成代谢网络；最后，采用"发酵环境刺激--基因表达响应"的模式，解析生物合成代谢通量分布，阐明香味活性物质生物合成代谢网络对发酵环境的应答机制。研究成果预期将阐明黑孢块菌液体深层发酵产香机理，为风味食品发酵过程质量控制奠定科学基础。

香味是构成发酵食品风味特色的重要因素，发酵食品的香味是由数十种乃至上百种香味活性物质协同作用而形成的，微生物发酵产香过程直接决定发酵食品的香味，而 目前微生物发酵产香机理的研究相当匮乏。黑孢块菌是一种原产自法国的名贵食用菌，以其浓郁而独特的香味成为研究热点。本项目以课题组首创的黑孢块菌液体深层发酵过程为典型模型，研究微生物发酵产香机理。首先，利用GC-O嗅辩仪筛选出了香味活性物质，再利用香味活性成分缺失和重构的方法评价香味活性物质对香味形成的影响规律；然后，筛选并鉴定了与香味活性物质生物合成密切相关的基因，确定了挥发性有机含硫化合物（VOSCs）生物合成途径关键酶基因氨基转移酶基因ARO8-2、脱羧酶基因PDC1和脱巯基酶基因STR3，构建了6种氨基酸(甲硫氨酸、缬氨酸、丝氨酸、苯丙氨酸、苏氨酸和异亮氨酸)与香味活性物质的生物合成代谢网络；最后，采用“发酵环境刺激——基因表达响应”的模式，阐明了黑孢块菌液体发酵过程中一类关键香味活性物质——VOSCs的分子调控机制：甲硫氨酸的添加，调控了VOSCs的生物合成途径中主效酶基因ARO8-2、PDC1和STR3的转录水平，进而影响VOSCs的生物合成，最终提升了黑孢块菌液体深层发酵过程中的香味特征。研究成果阐明了黑孢块菌液体深层发酵产香机理，为风味食品发酵过程质量控制奠定科学基础。