Solar-to-chemical and solar-to-fuel production from CO2 by metabolically engineered microorganisms

https://doi.org/10.1016/j.copbio.2016.11.017Get rights and content

Highlights

  • Development of solar-to-chemical and solar-to-fuel production platforms with bacteria.

  • Applying CRISPR-Cas9 system to cyanobacteria for solar-to-chemical production.

  • Integrating bio-electrochemical systems with engineered microbial system.

Recent development of carbon capture utilization (CCU) for reduction of greenhouse gas emission are reviewed. In the case of CO2 utilization, I describe development of solar-to-chemical and solar-to-fuel technology that refers to the use of solar energy to convert CO2 to desired chemicals and fuels. Photoautotrophic cyanobacterial platforms have been extensively developed on this principle, producing a diverse range of alcohols, organic acids, and isoprenoids directly from CO2. Recent breakthroughs in the metabolic engineering of cyanobacteria were reviewed. In addition, adoption of the light harvesting mechanisms from nature, photovoltaics-derived water splitting technologies have recently been integrated with microbial biotechnology to produce desired chemicals. Studies on the integration of electrode material with next-generation microbes are showcased for alternative solar-to-chemical and solar-to-fuel platforms.

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)

  • C. Liu et al.

    Water splitting-biosynthetic system with CO(2) reduction efficiencies exceeding photosynthesis

    Science

    (2016)
  • J.C. Liao et al.

    Fuelling the future: microbial engineering for the production of sustainable biofuels

    Nat Rev Microbiol

    (2016)
  • K.P. Kuhl et al.

    Electrocatalytic conversion of carbon dioxide to methane and methanol on transition metal surfaces

    J Am Chem Soc

    (2014)
  • L.B. Liao et al.

    Efficient solar water-splitting using a nanocrystalline CoO photocatalyst

    Nat Nanotechnol

    (2014)
  • D.E. Robertson et al.

    A new dawn for industrial photosynthesis

    Photosynth Res

    (2011)
  • S. Gudmundsson et al.

    Cyanobacteria as photosynthetic biocatalysts: a systems biology perspective

    Mol Biosyst

    (2015)
  • A.M. Varman et al.

    Photoautotrophic production of D-lactic acid in an engineered cyanobacterium

    Microb Cell Fact

    (2013)
  • S.E. Cohen et al.

    Circadian rhythms in cyanobacteria

    Microbiol Mol Biol Rev

    (2015)
  • R. Saha et al.

    Diurnal regulation of cellular processes in the Cyanobacterium Synechocystis sp. strain PCC 6803: insights from transcriptomic, fluxomic, and physiological analyses

    MBio

    (2016)
  • S. Diamond et al.

    The circadian oscillator in Synechococcus elongatus controls metabolite partitioning during diurnal growth

    Proc Natl Acad Sci U S A

    (2015)
  • S. Zhang et al.

    The tricarboxylic acid cycle in cyanobacteria

    Science

    (2011)
  • X. Chen et al.

    The Entner–Doudoroff pathway is an overlooked glycolytic route in cyanobacteria and plants

    Proc Natl Acad Sci U S A

    (2016)
  • S.Y. Zhang et al.

    Biochemical validation of the glyoxylate cycle in the cyanobacterium Chlorogloeopsis fritschii strain PCC 9212

    J Biol Chem

    (2015)
  • W. Xiong et al.

    The gamma-aminobutyric acid shunt contributes to closing the tricarboxylic acid cycle in Synechocystis sp. PCC 6803

    Mol Microbiol

    (2014)
  • W. Xiong et al.

    Phosphoketolase pathway contributes to carbon metabolism in cyanobacteria

    Nat Plants

    (2015)
  • J. Anfelt et al.

    Genetic and nutrient modulation of acetyl-CoA levels in Synechocystis for n-butanol production

    Microb Cell Fact

    (2015)
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