Center for Bioresource and Bioenergy, School of Biotechnology, Jiangnan University, 1800 Lihu Avenue, Wuxi, 214122, China.
School of Life Science and Food Engineering, Huaiyin Institute of Technology, 1st East Meicheng Road, Huaian, 223003, China.
Microb Cell Fact. 2018 May 2;17(1):66. doi: 10.1186/s12934-018-0915-x.
Lignocellulosic ethanol could offer a sustainable source to meet the increasing worldwide demand for fuel. However, efficient and simultaneous metabolism of all types of sugars in lignocellulosic hydrolysates by ethanol-producing strains is still a challenge.
An engineered strain Escherichia coli B0013-2021HPA with regulated glucose utilization, which could use all monosaccharides in lignocellulosic hydrolysates except glucose for cell growth and glucose for ethanol production, was constructed. In E. coli B0013-2021HPA, pta-ackA, ldhA and pflB were deleted to block the formation of acetate, lactate and formate and additional three mutations at glk, ptsG and manZ generated to block the glucose uptake and catabolism, followed by the replacement of the wild-type frdA locus with the ptsG expression cassette under the control of the temperature-inducible λ pR and pL promoters, and the final introduction of pEtac-PA carrying Zymomonas mobilis pdc and adhB for the ethanol pathway. B0013-2021HPA was able to utilize almost all xylose, galactose and arabinose but not glucose for cell propagation at 34 °C and converted all sugars to ethanol at 42 °C under oxygen-limited fermentation conditions.
Engineered E. coli strain with regulated glucose utilization showed efficient metabolism of mixed sugars in lignocellulosic hydrolysates and thus higher productivity of ethanol production.
木质纤维素乙醇可以提供一种可持续的来源，以满足全球对燃料日益增长的需求。然而，通过生产乙醇的菌株高效且同时代谢木质纤维素水解物中的所有类型的糖仍然是一个挑战。
构建了一株经过基因工程改造的大肠杆菌 B0013-2021HPA，其葡萄糖利用受到调控，能够利用木质纤维素水解物中的所有单糖进行细胞生长，而仅利用葡萄糖进行乙醇生产。在大肠杆菌 B0013-2021HPA 中，缺失了 pta-ackA、ldhA 和 pflB 以阻止乙酸、乳酸和甲酸的形成，并且在 glk、ptsG 和 manZ 处额外引入了三个突变以阻断葡萄糖的摄取和分解代谢，随后在温度诱导的 λ pR 和 pL 启动子的控制下，用 ptsG 表达盒取代野生型 frdA 基因座，最后引入携带运动发酵单胞菌 pdc 和 adhB 的 pEtac-PA 用于乙醇途径。B0013-2021HPA 能够在 34°C 下几乎利用所有木糖、半乳糖和阿拉伯糖但不利用葡萄糖进行细胞繁殖，并且在 42°C 下在限氧发酵条件下将所有糖转化为乙醇。
经过基因工程改造的葡萄糖利用受到调控的大肠杆菌菌株显示出对木质纤维素水解物中混合糖的高效代谢能力，从而提高了乙醇生产的生产力。
