title: Biosynthesis of platform chemical 3-hydroxypropionic acid (3-HP) directly from CO2 in cyanobacterium Synechocystis sp. PCC 6803.
abstract: 3-hydroxypropionic acid (3-HP) is an important platform chemical with a wide range of applications. So far large-scale production of 3-HP has been mainly through petroleum-based chemical processes, whose sustainability and environmental issues have attracted widespread attention. With the ability to fix CO2 directly, cyanobacteria have been engineered as an autotrophic microbial cell factory to produce fuels and chemicals. In this study, we constructed the biosynthetic pathway of 3-HP in cyanobacterium Synechocystis sp. PCC 6803, and then optimized the system through the following approaches: i) increasing expression of malonyl-CoA reductase (MCR) gene using different promoters and cultivation conditions; ii) enhancing supply of the precursor malonyl-CoA by overexpressing acetyl-CoA carboxylase and biotinilase; iii) improving NADPH supply by overexpressing the NAD(P) transhydrogenase gene; iv) directing more carbon flux into 3-HP by inactivating the competing pathways of PHA and acetate biosynthesis. Together, the efforts led to a production of 837.18 mg L(-1) (348.8 mg/g dry cell weight) 3-HP directly from CO2 in Synechocystis after 6 days cultivation, demonstrating the feasibility photosynthetic production of 3-HP directly from sunlight and CO2 in cyanobacteria. In addition, the results showed that overexpression of the ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco) gene from Anabaena sp. PCC 7120 and Synechococcus sp. PCC 7942 led to no increase of 3-HP production, suggesting CO2 fixation may not be a rate-limiting step for 3-HP biosynthesis in Synechocystis.
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, P.R. China; Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin 300072, P.R. China; Synbio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China.
authors.forename: Yunpeng
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, P.R. China; Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin 300072, P.R. China; Synbio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China.
authors.forename: Tao
authors.initials: T
authors.lastname: Sun
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, P.R. China; Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin 300072, P.R. China; Synbio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China.
authors.forename: Xingyan
authors.initials: X
authors.lastname: Gao
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, P.R. China; Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin 300072, P.R. China; Synbio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China.
authors.forename: Mengliang
authors.initials: M
authors.lastname: Shi
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, P.R. China; Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin 300072, P.R. China; Synbio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China.
authors.forename: Lina
authors.initials: L
authors.lastname: Wu
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, P.R. China; Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin 300072, P.R. China; Synbio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China.
authors.forename: Lei
authors.initials: L
authors.lastname: Chen
authors.affiliation: Laboratory of Synthetic Microbiology, School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, P.R. China; Key Laboratory of Systems Bioengineering, Ministry of Education of China, Tianjin 300072, P.R. China; Synbio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering, Tianjin, P.R. China. Electronic address: wwzhang8@tju.edu.cn.
authors.forename: Weiwen
authors.initials: W
authors.lastname: Zhang
mesh_terms: D002245:Carbon Dioxide / Q000378:metabolism*; D019344:Lactic Acid / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000302:isolation & purification; D008027:Light; D060847:Metabolic Engineering / Q000379:methods*; D053858:Metabolic Networks and Pathways / Q000502:physiology; D009249:NADP / Q000235:genetics / Q000378:metabolism*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology / Q000528:radiation effects; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D011994:Recombinant Proteins; D002245:Carbon Dioxide; D019344:Lactic Acid; D009249:NADP; C031601:hydracrylic acid; D010088:Oxidoreductases; C454539:malonyl-Coa reductase
keywords: 3-HP; Biosynthesis; Optimization; Synechocystis; Synthetic biology