Riboflavin is a commercially important compound in the food, pharmaceutical, chemical, and cosmetic industries. The down-regulation of expression levels of ribF, purA and guaC genes involved in the downstream or branch reactions of riboflavin biosynthesis pathway could direct more carbon flux to riboflavin accumulation. In this study, we made an attempt to fine-tune the expression levels of the 3 genes by using synthetic regulatory small RNA to enhance riboflavin production in Escherichia coli. Firstly, each of the 3 genes was knocking down by using 5 different sRNAs, respectively, and a highest increase of 50.2 % in riboflavin titer was achieved by using anti-ribF₅ sRNA. Then this sRNA was further co-expressed with 5 anti-purA and 5 anti-guaC sRNAs to simultaneously knocking down 2 or 3 genes. Co-expression of anti-ribF₅ and anti-guaC₃ led to the highest riboflavin production of 1091.3 mg/L, which was further increased by 97.6 % compared to the base strain. Finally, the expression levels of anti-ribF₅ and anti-guaC₃ were further fine-tuned by using 4 different promoters. The best strain WY40, in which the two sRNAs were respectively expressed by P_J23100 and P_J23107 promoter, produced 1454.5 mg/L riboflavin with an increase of 163.4 % compared to the base strain. To our knowledge, it’s the first study to enhance riboflavin synthesis by simultaneously regulating the expression levels of ribF, purA and guaC genes, which led to a highest yield of 0.147 g/g glucose among all reported riboflavin-producing strains.

核黄素是食品、制药、化学和化妆品行业中一种重要的商业化合物。的表达水平的下调ribF，的purA和guaC涉及核黄素生物合成途径的下游或分支反应基因可以引导更多的碳通量核黄素积累。在这项研究中，我们尝试通过使用合成的调节性小 RNA 来微调 3 个基因的表达水平，以提高大肠杆菌中的核黄素产量。首先，分别使用5种不同的sRNAs敲除3个基因中的每一个，使用anti- ribF ₅实现了核黄素滴度最高50.2%的增加sRNA。然后此的sRNA用5抗进一步共表达的purA和5抗guaC的sRNA向下2或3种基因同时爆震。anti- ribF ₅和 anti- guaC _{3 的}共表达导致最高的核黄素产量为 1091.3 mg/L，与基础菌株相比进一步增加了 97.6%。最后，通过使用 4 种不同的启动子进一步微调anti- ribF ₅和 anti- guaC ₃的表达水平。最佳菌株WY40，其中两种sRNA分别由P _J23100和P _J23107表达启动子产生了 1454.5 mg/L 的核黄素，与基础菌株相比增加了 163.4%。据我们所知，这是第一个研究中，通过同时调节的表达水平，以提高核黄素合成ribF，的purA和guaC基因，其导致了0.147克/克葡萄糖所有报告的核黄素生产菌株中具有最高的产率。