黑蒜功能性寡糖结构特征及其对肠道菌群的影响与作用机制研究

Black garlic is produced by fresh garlic undergoing controlled high temperature and humidity without any additives. Thermal degradation is the main source of functional oligosaccharides in the black garlic processing. Previous studies indicated that one product of the polysaccharides degradation was oligosaccharides. However, it is difficult to further elucidate the method of controlled degradation to produce functional oligosaccharides due to the incomplete degradation of polysaccharides, excessive degradation of oligosaccharides and the unclear of oligosaccharides structure; in addition, whether oligosaccharides endowed new functions to black garlic has not been reported yet. Oligosaccharides are often used as prebiotics and their probiotic effects play a beneficial role in host health by altering the composition of the intestinal microflora. This study is screened the functional oligosaccharides fraction of black garlic with bioactive in vitro. Then the oligosaccharides in the mixture are isolated, purified and identified; a comprehensive study of oligosaccharides on intestinal microflora are done using in vitro experiments and 16S rDNA metagenomics sequencing, while fluorescence labeling technique is used to study the relationship between oligosaccharides and probiotics, to clarify the structure of oligosaccharides and its structure-activity relationship and mechanism with intestinal microflora. All these will serve as a theoretical basis and technical support for targeted producing the oligosaccharides, and revealing the new function of black garlic.

黑蒜是新鲜大蒜通过控制温度和湿度加工形成的一种大蒜深加工产品。高温降解是黑蒜加工过程中功能性寡糖的主要来源，但由于在黑蒜加工过程中存在多糖降解不完全、功能性寡糖过度降解、功能性寡糖结构特征未知等问题，难以进一步阐明可控降解生成功能性寡糖的方法。此外功能性寡糖是否赋予黑蒜新的功能也未见报道。寡糖常被用作益生元，其益生作用主要通过改变肠道菌群的组成对宿主健康发挥有益作用。本课题拟通过体外试验筛选益生活性较强的功能性寡糖组分，对其进行分离纯化和结构鉴定，进一步采用体外试验和16SrDNA宏基因组测序的方法，全面研究黑蒜功能性寡糖对肠道菌群的影响，并通过荧光标记示踪技术研究其与益生菌的作用历程，以期阐明功能性寡糖的结构及其与肠道菌群的构效关系和作用机制，为进一步探究多糖可控降解生成功能性寡糖方法、揭示黑蒜的新功能提供理论指导和技术支持。

大蒜多糖主要为果聚糖，约占大蒜干重的75%以上，是大蒜的重要组成成分。黑蒜加工过程中，大蒜多糖主要通过高温降解产生寡糖，但多糖降解过程复杂，存在降解不完全、功能性寡糖过度降解、功能性寡糖未知等问题，难以发挥其益生作用，并未能对大蒜多糖的有效降解进行控制。.本项目在体外模拟多糖降解的基础上，采用膜分离技术获得了不同分子量寡糖，并确定了不同分子量寡糖对益生菌的增殖作用，其中分子量为300-1000 Da的寡糖对益生菌的增殖作用最佳。以此寡糖为目标，确定了酸水解与膜分离技术的最佳工艺，建立了连续制备分离系统，并进一步通过Bio gel P-2、活性炭柱、核磁共振等手段分离纯化鉴定了其结构。项目探究了寡糖的体外消化特性及其对小鼠肠道菌群的影响，明确了其在胃液少量降解外，在口腔、肠道难以消化的特性，并且其可以增加小鼠粪便含水量及肠道中SCFAs含量，改善了肠道菌群结构，并进一步确定了其提高肠道免疫能力及微生物的代谢活性等作用，为揭示黑蒜新功能提供了理论依据。同时，确定了可控降解生成黑蒜功能性寡糖的方法。此外，研究中发现了黑蒜加工过程中存在一些内生菌可以产生菊粉水解酶，是否会在黑蒜加工中发挥多糖降解作用产生功能性寡糖有待进一步研究。