短乳杆菌JYX2接种发酵抑制低盐泡菜中亚硝酸盐积累的分子机制

The accumulation of nitrite in low-salt paocai fermentation process will bring the safety problems. The inoculation of screened nitrite-reducing Lactobacillus brevis JYX2 (L. brevis JYX2) could inhibit the accumulation of nitrite during low-salt paocai fermentation, but its mechanism remains unknown. This study will focus on the nitrogen metabolism of microbial community in spontaneous and inoculated fermentation with L. brevis JYX2 as starter. To determine the key microbes involved in the pathway of nitrate degradation, the gene and protein profiles of microbial community involved in nitrogen metabolism will be investigated by using metatranscriptomics and metaproteomics in low-salt paocai. The genes and proteins expression of L. brevis JYX2 involved in the nitrite degradation pathway will be revealed. Combined with the metabolic and Dual RNA-seq analysis of the co-culture, the regulation of the gene expression of the key microbes by L. brevis JYX2 will be determined. Collectively, the inhibited molecular mechanism of the accumulation of nitrite in low-salt paocai by inoculated L. brevis JYX2 will be clarified. This study will provide theoretical basis for the scientific application of functional lactic acid bacteria to control quality of fermented food.

泡菜低盐发酵过程中亚硝酸盐的积累给产品带来了安全问题，接种发酵能够有效抑制亚硝酸盐的积累，但其分子机制尚不清晰。本项目利用前期筛选的具有降亚硝酸盐能力的短乳杆菌（L. brevis）JYX2为发酵剂，采用宏转录组和宏蛋白质组技术解析自然发酵和接种发酵低盐泡菜中参与氮代谢的微生物基因和蛋白表达谱，挖掘参与亚硝酸盐产生的关键微生物，揭示L. brevis JYX2参与亚硝酸盐降解途径的基因和蛋白表达情况。结合共培养的互作转录组和代谢物分析，明确L. brevis JYX2对关键微生物参与硝酸盐还原途径基因表达的调控方式。从分子层面揭示L. brevis JYX2接种发酵抑制低盐泡菜中亚硝酸盐积累的机制。为乳酸菌发酵剂在发酵食品品质控制方面的科学应用提供理论基础。

泡菜低盐发酵过程中亚硝酸盐的积累给产品带来了安全问题，接种发酵能够有效抑制亚硝酸盐的积累，但其分子机制尚不清晰。本项目首先开展了前期筛选的降亚硝酸盐短乳杆菌JYX2菌株产酸、耐酸、耐盐等发酵特性，明确了盐度、酸度等环境对其降亚硝酸盐特性的影响，以及低盐发酵泡菜中亚硝酸盐的积累规律。然后，开展了短乳杆菌JYX2接种发酵不同原料泡菜中亚硝酸盐以及代谢产物的动态变化规律研究，明确原料对短乳杆菌JYX2抑制泡菜中亚硝酸盐的积累无显著影响，揭示亚硝酸盐积累峰值节点处微生物群落组成，并筛选获得主要产亚硝酸盐微生物。根据PICRUSt基因功能预测分析结果，短乳杆菌JYX2通过抑制发酵体系中亚硝酸盐的还原来减少亚硝酸盐的积累。最后，基于共酵泡菜的宏组学分析结果，明确短乳杆菌JYX2通过促进发酵体系中反硝化途径中nosZ基因的表达以及抑制硝酸盐还原酶基因的表达来减少泡菜中亚硝酸盐的积累。另外，本项目还研究了接种发酵对泡菜品质的影响，为泡菜中亚硝酸盐的调控提供靶点信息，为低盐泡菜的品质提升奠定理论基础。