Jiang Ting, Zhang Chen, He Qin, Zheng Zhaojuan, Ouyang Jia
Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, Nanjing, 210037, People's Republic of China.
College of Chemical Engineering, Nanjing Forestry University, Nanjing, 210037, People's Republic of China.
Appl Biochem Biotechnol. 2018 Feb;184(2):703-715. doi: 10.1007/s12010-017-2581-6. Epub 2017 Aug 24.
The efficient utilization of xylose is regarded as a technical barrier to the commercial production of bulk chemicals from biomass. Due to the desirable mechanical properties of polylactic acid (PLA) depending on the isomeric composition of lactate, biotechnological production of lactate with high optical pure has been increasingly focused in recent years. The main objective of this work was to construct an engineered Escherichia coli for the optically pure L-lactate production from xylose. Six chromosomal deletions (pflB, ldhA, ackA, pta, frdA, adhE) and a chromosomal integration of L-lactate dehydrogenase-encoding gene (ldhL) from Bacillus coagulans was involved in construction of E. coli KSJ316. The recombinant strain could produce L-lactate from xylose resulting in a yield of 0.91 g/g xylose. The chemical purity of L-lactate was 95.52%, and the optical purity was greater than 99%. Moreover, three strategies, including overexpression of L-lactate dehydrogenase, intensification of xylose catabolism, and addition of additives to medium, were designed to enhance the production. The results showed that they could increase the concentration of L-lactate by 32.90, 20.13, and 233.88% relative to the control, respectively. This was the first report that adding formate not only could increase the xylose utilization but also led to the fewer by-product levels.
木糖的高效利用被认为是生物质大规模生产大宗化学品的技术障碍。由于聚乳酸（PLA）的理想机械性能取决于乳酸的异构体组成，近年来，高光学纯度乳酸的生物技术生产越来越受到关注。这项工作的主要目标是构建一种工程大肠杆菌，用于从木糖生产光学纯的L-乳酸。大肠杆菌KSJ316的构建涉及六个染色体缺失（pflB、ldhA、ackA、pta、frdA、adhE）和来自凝结芽孢杆菌的L-乳酸脱氢酶编码基因（ldhL）的染色体整合。重组菌株可以从木糖生产L-乳酸，产量为0.91 g/g木糖。L-乳酸的化学纯度为95.52%，光学纯度大于99%。此外，还设计了三种策略来提高产量，包括过表达L-乳酸脱氢酶、强化木糖分解代谢和向培养基中添加添加剂。结果表明，它们相对于对照分别可将L-乳酸浓度提高32.90%、20.13%和233.88%。这是第一份关于添加甲酸盐不仅可以提高木糖利用率，还能降低副产物水平的报告。
