黄原胶降解产生的低聚糖不仅有抗氧化活性，而且有较强的诱抗活性，是一种有价值的功能性寡糖。然而，现阶段微生物降解黄原胶的可控性差，获得的寡糖产物为聚合度分散、侧链结构不单一的混合物，不利于后续构效分析和工业化生产。因此，解析黄原胶生物降解途径并进行理性改造是亟待解决的问题。本项目拟在枯草芽孢杆菌模式菌株中异源表达微细菌Microbacterium sp. XT11的黄原胶降解基因簇，并阐明相关基因元件的功能。同时，通过黄原胶内切酶与糖结合单元的融合，提高酶切割黄原胶主链的特异性，降低寡糖产物分散度。最后，基于“基因电路”思想，利用上述研究获得的功能基因元件，实施黄原胶降解基因簇的功能改造，构建能够可控降解黄原胶的枯草芽孢杆菌工程菌，获得分散度低、侧链结构单一的寡糖并进行初步构效分析。本项目将进一步阐明黄原胶降解的分子基础，获得的新信息和新材料将对研制食品级功能寡糖具有重要理论意义和经济价值。

Xantho-oligosaccharide produced by xanthan degradation has special physiological activities, such as anti-oxidant and the defense responce. Therefore, xantho-oligosaccharide is a valuable functional oligosaccharide. However, at present, the xanthan degradation is not controllable that lead to mixed oligosaccharides with different degree of polymerization and side-chain structure. Thus it is difficult to study the structure-activity relationship. It is important to reveal and reconstruct the pathway of xanthan degradation. In this project, we are going to heterelogously express the xanthan-degrading cluster in the type strain Bacillus subtilis and reveal the function of the cluster. Meanwhile, we will increase the degrading specificity of xanthan backbone by fusing endoxanthanase with carbohydrate binding modules to produce oligosaccharides with low dispersity. Finally, the xanthan-degrading cluster will be reconstructed and expressed in B. subtilis based on “gene networks”, resulting in a recombinant strain that could specifically degrade xanthan and produce xantho-oligosaccharides with uniform structure. Our work will elucidate the molecular mechanism of xanthan degradation and is significant for the production of functional oligosaccharides at food grade.