Abstract：
d-mannose has been widely used in food, medicine, cosmetic, and food-additive industries. To date, chemical synthesis or enzymatic conversion approaches based on iso/epimerization reactions for d-mannose production suffered from low conversion rate due to the reaction equilibrium, necessitating intricate separation processes for obtaining pure products on an industrial scale. To circumvent this challenge, this study showcased a new approach for d-mannose synthesis from glucose through constructing a phosphorylation-dephosphorylation pathway in an engineered strain. Specifically, the gene encoding phosphofructokinase (PfkA) in glycolytic pathway was deleted in Escherichia coli to accumulate fructose-6-phosphate (F6P). Additionally, one endogenous phosphatase, YniC, with high specificity to mannose-6-phosphate, was identified. In ΔpfkA strain, a recombinant synthetic pathway based on mannose-6-phosphate isomerase and YniC was developed to direct F6P to mannose. The resulting strain successfully produced 25.2 g/L mannose from glucose with a high conversion rate of 63% after transformation for 48 h. This performance surpassed the 15% conversion rate observed with 2-epimerases. In conclusion, this study presents an efficient method for achieving high-yield mannose synthesis from cost-effective glucose.
摘要：
D-甘露糖已广泛应用于食品中,医学,化妆品,和食品添加剂行业。迄今为止,基于异/差向异构化反应生产d-甘露糖的化学合成或酶转化方法由于反应平衡而转化率低，需要复杂的分离方法以工业规模获得纯产物。为了规避这一挑战，这项研究展示了一种通过在工程菌株中构建磷酸化-去磷酸化途径从葡萄糖合成d-甘露糖的新方法。具体来说,在大肠杆菌中删除了糖酵解途径中编码磷酸果糖激酶（PfkA）的基因，以积累果糖-6-磷酸（F6P）。此外,一种内源性磷酸酶，YniC,对甘露糖-6-磷酸具有高特异性，已确定。在ΔpfkA菌株中，开发了基于甘露糖-6-磷酸异构酶和YniC的重组合成途径以将F6P定向到甘露糖。转化48小时后，所得菌株成功地从葡萄糖中产生了25.2g/L甘露糖，转化率高达63％。该性能超过了2-差向异构酶观察到的15％转化率。总之,这项研究提出了一种从经济有效的葡萄糖中实现高产率甘露糖合成的有效方法。
