ABSTRACT
The use of light energy to drive carbon dioxide (CO2) reduction for production of chemicals is of great significance for relieving environmental pressure and solving energy crisis. Photocapture, photoelectricity conversion and CO2 fixation are the key factors affecting the efficiency of photosynthesis, and thus also affect the efficiency of CO2 utilization. To solve the above problems, this review systematically summarizes the construction, optimization and application of light-driven hybrid system from the perspective of combining biochemistry and metabolic engineering. We introduce the latest research progress of light-driven CO2 reduction for biosynthesis of chemicals from three aspects: enzyme hybrid system, biological hybrid system and application of these hybrid system. In the aspect of enzyme hybrid system, many strategies were adopted such as improving enzyme catalytic activity and enhancing enzyme stability. In the aspect of biological hybrid system, many methods were used including enhancing biological light harvesting capacity, optimizing reducing power supply and improving energy regeneration. In terms of the applications, hybrid systems have been used in the production of one-carbon compounds, biofuels and biofoods. Finally, the future development direction of artificial photosynthetic system is prospected from the aspects of nanomaterials (including organic and inorganic materials) and biocatalysts (including enzymes and microorganisms).
Subject(s)
Carbon Dioxide/metabolism , Photosynthesis , Metabolic EngineeringABSTRACT
Environmental protection and energy supply are our two major concerns. Greenhouse gases released from energy consumption have serious impact on the environment. CO₂ fixation can be used to convert CO₂ into fuels or chemicals. However, natural carbon-fixing organisms usually have some disadvantages such as slow growth and low carbon fixation efficiency. Enhancing or remodeling CO₂ fixation pathways in model microorganisms can realize CO₂ recycling, which can further increase fuel or chemical production and reduce greenhouse gas emission. This review describes in detail metabolic engineering of CO₂ fixation pathways to improve chemical production and sugar synthesis, elaborates the role of relevant metabolic pathways and key enzymes in CO₂ fixation, introduces the application of electro-biochemical synthesis system, shows the great potential of CO₂ fixation, and prospects the future research direction of CO₂ fixation.
Subject(s)
Carbon Cycle , Carbon Dioxide , Heterotrophic Processes , Metabolic Engineering , Metabolic Networks and PathwaysABSTRACT
Background CO2 emission, water pollution and petroleum shortage are the issues coming with the development of industry. A cost effective system was constructed to fix the CO2 in flue gas (15% CO2), remove nitrogen and phosphorus from manure wastewater and produce biofuels at the same time. The significant cultivation conditions were selected by Plackett-Burman design, and then optimized with central composite design. Results Optimum culture condition was predicted at light intensity of 238 µmol·m- 2·s- 1, TN of 152 mg·L- 1, inoculum density of 0.3 g·L- 1, under which the measured CO2 fixation rate, total nitrogen and phosphorus removing rate, and lipid content were 638.13 mg·L- 1·d- 1, 88.16%, 73.98% and 11.9%, respectively. The lipid content was then enhanced to 24.2% by a nitrogen starvation strategy. Conclusion A cultivation strategy was suggested to achieve effective C/N/P removal from flue gas and manure wastewater, and meanwhile obtained high lipid content from microalgal biomass.