Li Chao, Tao Fei, Ni Jun, Wang Yu, Yao Feng, Xu Ping
State Key Laboratory of Microbial Metabolism, and School of Life Sciences &Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.
Sci Rep. 2015 May 5;5:9777. doi: 10.1038/srep09777.
It is increasingly attractive to engineer cyanobacteria for bulk production of chemicals from CO2. However, cofactor bias of cyanobacteria is different from bacteria that prefer NADH, which hampers cyanobacterial strain engineering. In this study, the key enzyme d-lactate dehydrogenase (LdhD) from Lactobacillus bulgaricus ATCC11842 was engineered to reverse its favored cofactor from NADH to NADPH. Then, the engineered enzyme was introduced into Synechococcus elongatus PCC7942 to construct an efficient light-driven system that produces d-lactic acid from CO2. Mutation of LdhD drove a fundamental shift in cofactor preference towards NADPH, and increased d-lactate productivity by over 3.6-fold. We further demonstrated that introduction of a lactic acid transporter and bubbling CO2-enriched air also enhanced d-lactate productivity. Using this combinational strategy, increased d-lactate concentration and productivity were achieved. The present strategy may also be used to engineer cyanobacteria for producing other useful chemicals.
通过工程改造蓝细菌以从二氧化碳大规模生产化学品越来越具有吸引力。然而，蓝细菌的辅因子偏好与偏好NADH的细菌不同，这阻碍了蓝细菌菌株的工程改造。在本研究中，对来自保加利亚乳杆菌ATCC11842的关键酶d-乳酸脱氢酶（LdhD）进行了工程改造，使其偏好的辅因子从NADH转变为NADPH。然后，将工程化酶引入聚球藻PCC7942中，构建了一个高效的光驱动系统，该系统可从二氧化碳生产d-乳酸。LdhD的突变推动了辅因子偏好向NADPH的根本性转变，并使d-乳酸生产率提高了3.6倍以上。我们进一步证明，引入乳酸转运蛋白和鼓入富含二氧化碳的空气也提高了d-乳酸生产率。使用这种组合策略，实现了d-乳酸浓度和生产率的提高。本策略也可用于工程改造蓝细菌以生产其他有用化学品。
