Riboflavin is widely used as a food additive. Here, multiple strategies were used to increase riboflavin production in Escherichia coli LS31T. First, purR deletion and co-overexpression of fbp, purF, prs, gmk, and ndk genes resulted in an increase of 18.6% in riboflavin titer (reaching 729.7 mg/L). Second, optimization of reduced nicotinamide adenine dinucleotide phosphate/nicotinamide adenine dinucleotide ratio and respiratory chain activity in LS31T increased the titer up to 1020.2 mg/L. Third, the expression level of the guaC gene in LS31T was downregulated by ribosome binding site replacement, and the riboflavin production was increased by 10.6% to 658.5 mg/L. Then, all the favorable modifications were integrated together, and the resulting strain LS72T produced 1339 mg/L of riboflavin. Moreover, the riboflavin titer of LS72T reached 21 g/L in fed-batch cultivation, with a yield of 110 mg riboflavin/g glucose. To our knowledge, both the riboflavin titer and yield obtained in fed-batch fermentation are the highest ones among all the rationally engineered strains.

中文翻译：

---

大肠杆菌高水平生产核黄素的合理工程

核黄素被广泛用作食品添加剂。在这里，使用多种策略来增加大肠杆菌LS31T 中核黄素的产量。首先，是purR缺失和共同过表达FBP，purF的，PRS，GMK和NDK基因导致核黄素滴度增加了18.6％（达到729.7毫克/升）。其次，LS31T 中还原型烟酰胺腺嘌呤二核苷酸磷酸/烟酰胺腺嘌呤二核苷酸比率和呼吸链活性的优化将滴度提高到 1020.2 mg/L。三、guaC的表达水平LS31T 基因被核糖体结合位点置换下调，核黄素产量增加 10.6% 至 658.5 mg/L。然后，将所有有利的修饰整合在一起，得到的菌株 LS72T 产生了 1339 mg/L 的核黄素。此外，LS72T的核黄素滴度在补料分批培养中达到21g/L，核黄素产量为110mg/g葡萄糖。据我们所知，补料分批发酵获得的核黄素滴度和产量都是所有合理工程菌株中最高的。