Solar-to-chemical and solar-to-fuel production from CO2 by metabolically engineered microorganisms
Graphical abstract
Introduction
The direct conversion of carbon dioxide to chemicals and fuels presents a sustainable solution for reducing greenhouse gas emissions and sustaining our supply of energy [1]. Ultimately, solar energy must be used for CO2 reduction and conversions to provide a sustainable system, and this system is now available in the forms of solar-to-chemical (S2C) and solar-to-fuels (S2F) technologies. Thus, the S2C and S2F technology must be developed to capture and convert the essential feedstocks using only three inputs (CO2, H2O, and solar energy) to produce the desired value-added chemicals and fuels (Figure 1). In the post-genomic era, photosynthetic organisms (including cyanobacteria) have been engineered to produce value-added chemicals, providing a number of promising S2C and S2F platforms. In addition to engineering photosynthetic organisms, improving natural systems of capturing solar energy and converting CO2 has motivated the development of inorganic-based S2C and S2F technologies. Electro-catalytic conversion of CO2 has been shown to produce methane and methanol [2] and efficient solar water-splitting (hydrolysis) using a photocatalyst has also been developed [3]. However, catalyst-based S2C and S2F technology only, has proven inadequate to complete biological CO2 conversion systems with carbon-carbon bond formation, high specificity, and low-cost materials. Moreover, such systems lack the properties of self-replication and self-repair. Thus, hybrid systems comprising an electrochemical in situ hydrogen-evolution reaction at the electrode and the biological CO2 fixation using autotrophic bacteria have been suggested as an alternative S2C and S2F platform.
The purpose of this review is to summarize the recent literature on S2C and S2F technology to produce desired products from CO2 and to describe their potential role in bioenergy applications using next-generation microbe-based technologies. The details on the platforms for S2C and S2F are shown in Figure 2.
Section snippets
Metabolic engineering of photoautotrophs for solar-to-chemicals (S2C)
Photoautotrophic bacteria (and cyanobacteria) are promising microbial platforms for continuous production of biochemicals and biofuels from CO2 and light (carbon and energy sources, respectively). This is because the practical maximum efficiency of the direct CO2 conversion process with cyanobacteria is seven-fold higher that of an algal open pond in terms of photon loss [4]. Furthermore, metabolic engineering of cyanobacteria has been focused for direct production, product secretion, and
Integrated bio-electrochemical systems with engineered chemolithoautotrophs for solar-to-chemicals (S2C)
Chemolithoautotrophic bacteria are non-phototrophic, CO2-utilizing microorganisms that oxidize dihydrogen (H2) or metabolically accept electrons for reduction. Gas fermentation and metabolic engineering of the chemolithoautotrophic strains have been discussed in terms of C1-carbon sources [41] and production of fuels and chemicals [42], as will be discussed in more detail below. The role of CO2 fixation through various metabolic pathways in chemolithoautotrophs can be substituted into the ‘dark
Conclusions
In this paper, I review the current status of solar-to-chemical and solar-to-fuels platforms for production of value-added chemicals from CO2, focusing on engineering of photosynthetic organisms and developing microbe-water splitting catalyst systems. Synthetic biology-inspired metabolic engineering of next-generation microbes will be established to accommodate more efficient S2C and S2F platforms. Beyond the proof-of-concept work on these platforms, further development for industrial scale-up
References and recommended reading
Papers of particular interest, published within the period of review, have been highlighted as:
• of special interest
•• of outstanding interest
Acknowledgements
I would like to thank Prof. Dr. Sang Jun Sim at Korea University, Dr. Byoung Koun Min, Dr. Youngsoon Um, Dr. Yun Jeong Hwang, and Dr. Sun-Mi Lee at Korea Institute of Science and Technology (KIST) for helpful discussions. This work was supported by Korea CCS R&D Center (KCRC) (Grant No. 2014M1A8A1049277) funded by the Korean Government (Ministry of Science, Information and Communications Technology (ICT) & Future Planning).
References (52)
- et al.
Cyanobacterial chemical production
J Biotechnol
(2016) - et al.
Engineering cyanobacteria for direct biofuel production from CO2
Curr Opin Biotechnol
(2015) - et al.
2,3 Butanediol production in an obligate photoautotrophic cyanobacterium in dark conditions via diverse sugar consumption
Metab Eng
(2016) - et al.
Engineered xylose utilization enhances bio-products productivity in the cyanobacterium Synechocystis sp. PCC 6803
Metab Eng
(2015) - et al.
The plasticity of cyanobacterial metabolism supports direct CO2 conversion to ethylene
Nat Plants
(2015) - et al.
Engineering the methylerythritol phosphate pathway in cyanobacteria for photosynthetic isoprene production from CO2
Energy Environ Sci
(2016) - et al.
Genome engineering in cyanobacteria: where we are and where we need to go
ACS Synth Biol
(2015) - et al.
Self-photosensitization of nonphotosynthetic bacteria for solar-to-chemical production
Science
(2016) - et al.
Hybrid bioinorganic approach to solar-to-chemical conversion
Proc Natl Acad Sci U S A
(2015) - et al.
Efficient solar-to-fuels production from a hybrid microbial-water-splitting catalyst system
Proc Natl Acad Sci U S A
(2015)
Water splitting-biosynthetic system with CO(2) reduction efficiencies exceeding photosynthesis
Science
Fuelling the future: microbial engineering for the production of sustainable biofuels
Nat Rev Microbiol
Electrocatalytic conversion of carbon dioxide to methane and methanol on transition metal surfaces
J Am Chem Soc
Efficient solar water-splitting using a nanocrystalline CoO photocatalyst
Nat Nanotechnol
A new dawn for industrial photosynthesis
Photosynth Res
Cyanobacteria as photosynthetic biocatalysts: a systems biology perspective
Mol Biosyst
Photoautotrophic production of D-lactic acid in an engineered cyanobacterium
Microb Cell Fact
Circadian rhythms in cyanobacteria
Microbiol Mol Biol Rev
Diurnal regulation of cellular processes in the Cyanobacterium Synechocystis sp. strain PCC 6803: insights from transcriptomic, fluxomic, and physiological analyses
MBio
The circadian oscillator in Synechococcus elongatus controls metabolite partitioning during diurnal growth
Proc Natl Acad Sci U S A
The tricarboxylic acid cycle in cyanobacteria
Science
The Entner–Doudoroff pathway is an overlooked glycolytic route in cyanobacteria and plants
Proc Natl Acad Sci U S A
Biochemical validation of the glyoxylate cycle in the cyanobacterium Chlorogloeopsis fritschii strain PCC 9212
J Biol Chem
The gamma-aminobutyric acid shunt contributes to closing the tricarboxylic acid cycle in Synechocystis sp. PCC 6803
Mol Microbiol
Phosphoketolase pathway contributes to carbon metabolism in cyanobacteria
Nat Plants
Genetic and nutrient modulation of acetyl-CoA levels in Synechocystis for n-butanol production
Microb Cell Fact
Cited by (69)
Full-spectrum photo-thermal conversion enabled by plasmonic titanium carbide modified phase change microcapsules
2023, Journal of Energy StorageEmerging chemo-biocatalytic routes for valorization of major greenhouse gases (GHG) into industrial products: A comprehensive review
2022, Journal of Industrial and Engineering ChemistryExploring the metabolic versatility of cyanobacteria for an emerging carbon-neutral bioeconomy
2022, Cyanobacterial Physiology: From Fundamentals to BiotechnologyCurrent processes and future challenges of photoautotrophic production of acetyl-CoA-derived solar fuels and chemicals in cyanobacteria
2020, Current Opinion in Chemical BiologyCurrent understanding of the cyanobacterial CRISPR-Cas systems and development of the synthetic CRISPR-Cas systems for cyanobacteria
2020, Enzyme and Microbial Technology