豆豉是集营养价值和保健功能于一体的大豆微生物发酵食品，风味在一定程度上直接决定豆豉的质量和消费者的可接受度。利用纯种芽孢杆菌（Bacillus）发酵豆豉，会使豆豉风味单一，且具有不同程度的氨味。在我们前期研究中，将乳酸菌尤其是乳酸杆菌（Lactobacillus）添加至Bacillus纯种发酵豆豉中进行混合发酵，能显著改善豆豉的风味。本项目拟选取L. plantarum YM-5-2和B. subtilis SP-8-5为研究材料，比较分析YM-5-2单独发酵和YM-5-2-SP-8-5混合发酵两种工艺条件下挥发性物质的变化情况和基因表达差异，从YM-5-2基因组中筛选出与风味形成相关的候选基因，利用基因敲除技术研究部分关键候选基因的生物学功能，为建立豆豉风味物质合成路径，诠释混合发酵改善豆豉风味的分子机制，使豆豉兼具味佳和益生两种功能提供理论依据。

Douchi which combined nutrient value with health function is a microbe-fermented soybean food. Flavor, to some extent, determines directly the quality of douchi and acceptance by consumers. Fermented douche with a pure Bacillus sp. will make douchi of single flavor and have ammoniacal odour at different degrees. In our previous studies, add lactic acid bacteria (especially Lactobacillus sp.) to fermented douchi with a pure Bacillus sp. as mixed-fermentation will improve significantly the flavor of douchi. With L. plantarum YM-5-2 and B. subtilis SP-8-5 as study material, we plan to compare and analyze the changes condition of volatile compounds and difference of gene expression between YM-5-2 separate fermentation and YM-5-2-SP-8-5 mixed-fermentation, and to screen candidate genes which probably related to flavor form from genome of YM-5-2, and to study the biological functions of partial key-candidate genes using gene knock-out technology. These studies will provide theoretical foundation for building pathway of synthesizing and douchi flavor compounds, and interpreting the molecular mechanism of improving douchi flavor with mixed-fermentation, and making douchi have both tasty and benefit health functions.