Key Laboratory of Industrial Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457, China.
National Engineering Laboratory for Industrial Enzymes, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, China.
Microb Cell Fact. 2024 Sep 14;23(1):251. doi: 10.1186/s12934-024-02501-2.
Seven-carbon sugars, which rarely exist in nature, are the key constitutional unit of septacidin and hygromycin B in bacteria. These sugars exhibit a potential therapeutic effect for hypoglycaemia and cancer and serve as building blocks for the synthesis of C-glycosides and novel antibiotics. However, chemical and enzymatic approaches for the synthesis of seven-carbon sugars have faced challenges, such as complex reaction steps, low overall yields and high-cost feedstock, limiting their industrial-scale production.
In this work, we propose a strain engineering approach for synthesising sedoheptulose using glucose as sole feedstock. The gene pfkA encoding 6-phosphofructokinase in Corynebacterium glutamicum was inactivated to direct the carbon flux towards the pentose phosphate pathway in the cellular metabolic network. This genetic modification successfully enabled the synthesis of sedoheptulose from glucose. Additionally, we identified key enzymes responsible for product formation through transcriptome analysis, and their corresponding genes were overexpressed, resulting in a further 20% increase in sedoheptulose production.
We achieved a sedoheptulose concentration of 24 g/L with a yield of 0.4 g/g glucose in a 1 L fermenter, marking the highest value up to date. The produced sedoheptulose could further function as feedstock for synthesising structural seven-carbon sugars through coupling with enzymatic isomerisation, epimerisation and reduction reactions.
七碳糖在自然界中很少存在，是细菌中 septacidin 和 hygromycin B 的关键结构单元。这些糖对低血糖和癌症具有潜在的治疗作用，并且可用作 C-糖苷和新型抗生素合成的构建块。然而，化学和酶法合成七碳糖面临着反应步骤复杂、总收率低和原料成本高的挑战，限制了其工业规模生产。
在这项工作中，我们提出了一种利用葡萄糖作为唯一原料合成 sedoheptulose 的菌株工程方法。失活 Corynebacterium glutamicum 中编码 6-磷酸果糖激酶的 pfkA 基因，以使细胞代谢网络中的碳通量定向流向戊糖磷酸途径。这种遗传修饰成功地实现了 sedoheptulose 从葡萄糖的合成。此外，我们通过转录组分析确定了负责产物形成的关键酶，并过表达了它们相应的基因，从而使 sedoheptulose 的产量进一步提高了 20%。
我们在 1 L 发酵罐中实现了 24 g/L 的 sedoheptulose 浓度，葡萄糖得率为 0.4 g/g，这是迄今为止的最高值。所产生的 sedoheptulose 可以通过与酶促异构化、差向异构化和还原反应偶联，进一步用作合成结构七碳糖的原料。
