核黄素是8种B族维生素成员之一，它为哺乳动物的必需营养物。在最近15年时间内，化学合成核黄素完全被微生物合成所替代，目前发酵工业上的主要生产菌株为枯草杆菌和棉囊阿舒氏酵母。近年来，国内农产品以及各种化工原材料价格不断上升，人力、环保等多种开支也在增加，造成核黄素生产成本不断上升。因此，进一步改良核黄素生产菌种，降低发酵生产成本已成当务之急。本项目率先使用合成生物学技术构建高产核黄素的大肠杆菌工程菌株,对枯草杆菌核黄素从头生物合成途径的26个基因进行结构优化和化学合成，在大肠杆菌中重构核黄素生物合成系统。最终，将通过DNA重排技术对T7 RNA聚合酶、核黄素从头生物合成系统和全局转录调控因子进行体外定向分子进化，获得超量生产核黄素的大肠杆菌工程菌株。本项目将为合成生物学在维生素生物制造上的应用奠定基础。

Riboflavin is one of 8 B vitamins, it is essential for animals. Riboflavin production has shifted from chemical synthesis to exclusive microbiological synthesis in less than 15 years,and bacillus subtilis and ashbya gossypii are the main industrial producers. In recent years, riboflavin production costs continue to rise in china,as our cost of production keeps increasing,such as agricultural products, chemical raw materiasl, wages and environmental protection. Therefore, the further improvement of riboflavin producing strains and reduction in fermentation production cost have become a pressing matter of the moment.In this project, riboflavin high producer strains will be created using synthetic biology, 26 genes responsible for de novo riboflavin biosynthesis in bacillus subtilis were structurally optimized and chemically synthesized,then we reconstitute the riboflavin biosynthetic pathway in Escherichia coli.Finally, in vitro directed molecular evolution by DNA shuffling will be used for optimization of the T7 RNA polemerase , riboflavin biosynthetic pathway and Escherichia coli global transcriptional factor. This project will lay the foundation for the application of synthetic biology in vitamin biomanufacturing.