1
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Han J, Asano K, Matsumoto T, Yamada R, Ogino H. Engineering acyl-ACP reductase with fusion tags enhances alka(e)ne synthesis in Escherichia coli. Enzyme Microb Technol 2023; 168:110262. [PMID: 37224590 DOI: 10.1016/j.enzmictec.2023.110262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 05/17/2023] [Accepted: 05/18/2023] [Indexed: 05/26/2023]
Abstract
Alka(e)nes are high-value chemicals with a potentially broad range of industrial applications because of their following advantages: (1) chemical and structural resemblance to petroleum hydrocarbons and (2) higher energy density and hydrophobicity than those of other biofuels. The low yield of bio-alka(e)nes, however, hinders their commercial application. The activity and solubility of acyl carrier protein (ACP) reductase (AAR) affect alka(e)ne biosynthesis in cyanobacteria. The enhancement of the activity and concentration of soluble AAR through genetic and process engineering can improve bio-alka(e)ne yield. Although fusion tags are used to enhance the expression or solubility of recombinant proteins, their effectiveness in improving the production of bio-alka(e)nes has not yet been reported. Fusion tags can be used to improve the amount or activity of soluble AAR in Escherichia coli and to increase the yield of alka(e)nes in E. coli cells co-expressing aldehyde deformylating oxygenase (ADO). Hence, in the present study, histidine (His6/His12), thioredoxin (Trx), maltose-binding protein (MBP), and N-utilization substance (NusA) were used as AAR fusion tags. The strain expressing SeAAR with His12 tag and NpADO showed a 7.2-fold higher yield of alka(e)nes than the strain expressing AAR without fusion tag and NpADO. The highest titer of alka(e)nes (194.78 mg/L) was achieved with the His12 tag.
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Affiliation(s)
- Jiahu Han
- Department of Chemical Engineering, Osaka Metropolitan University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Koki Asano
- Department of Chemical Engineering, Osaka Metropolitan University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Takuya Matsumoto
- Department of Chemical Engineering, Osaka Metropolitan University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan.
| | - Ryosuke Yamada
- Department of Chemical Engineering, Osaka Metropolitan University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
| | - Hiroyasu Ogino
- Department of Chemical Engineering, Osaka Metropolitan University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan
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2
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Hayashi Y, Arai M. Recent advances in the improvement of cyanobacterial enzymes for bioalkane production. Microb Cell Fact 2022; 21:256. [PMID: 36503511 PMCID: PMC9743570 DOI: 10.1186/s12934-022-01981-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 12/01/2022] [Indexed: 12/14/2022] Open
Abstract
The use of biologically produced alkanes has attracted considerable attention as an alternative energy source to petroleum. In 2010, the alkane synthesis pathway in cyanobacteria was found to include two small globular proteins, acyl-(acyl carrier protein [ACP]) reductase (AAR) and aldehyde deformylating oxygenase (ADO). AAR produces fatty aldehydes from acyl-ACPs/CoAs, which are then converted by ADO to alkanes/alkenes equivalent to diesel oil. This discovery has paved the way for alkane production by genetically modified organisms. Since then, many studies have investigated the reactions catalyzed by AAR and ADO. In this review, we first summarize recent findings on structures and catalytic mechanisms of AAR and ADO. We then outline the mechanism by which AAR and ADO form a complex and efficiently transfer the insoluble aldehyde produced by AAR to ADO. Furthermore, we describe recent advances in protein engineering studies on AAR and ADO to improve the efficiency of alkane production in genetically engineered microorganisms such as Escherichia coli and cyanobacteria. Finally, the role of alkanes in cyanobacteria and future perspectives for bioalkane production using AAR and ADO are discussed. This review provides strategies for improving the production of bioalkanes using AAR and ADO in cyanobacteria for enabling the production of carbon-neutral fuels.
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Affiliation(s)
- Yuuki Hayashi
- grid.26999.3d0000 0001 2151 536XDepartment of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902 Japan ,grid.26999.3d0000 0001 2151 536XEnvironmental Science Center, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 Japan
| | - Munehito Arai
- grid.26999.3d0000 0001 2151 536XDepartment of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902 Japan ,grid.26999.3d0000 0001 2151 536XDepartment of Physics, Graduate School of Science, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902 Japan
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3
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Biosynthesis of alkanes/alkenes from fatty acids or derivatives (triacylglycerols or fatty aldehydes). Biotechnol Adv 2022; 61:108045. [DOI: 10.1016/j.biotechadv.2022.108045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 09/22/2022] [Accepted: 09/24/2022] [Indexed: 11/27/2022]
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4
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Parveen H, Yazdani SS. Insights into cyanobacterial alkane biosynthesis. J Ind Microbiol Biotechnol 2022; 49:kuab075. [PMID: 34718648 PMCID: PMC9118987 DOI: 10.1093/jimb/kuab075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Accepted: 09/09/2021] [Indexed: 11/12/2022]
Abstract
Alkanes are high-energy molecules that are compatible with enduring liquid fuel infrastructures, which make them highly suitable for being next-generation biofuels. Though biological production of alkanes has been reported in various microorganisms, the reports citing photosynthetic cyanobacteria as natural producers have been the most consistent for the long-chain alkanes and alkenes (C15-C19). However, the production of alkane in cyanobacteria is low, leading to its extraction being uneconomical for commercial purposes. In order to make alkane production economically feasible from cyanobacteria, the titre and yield need to be increased by several orders of magnitude. In the recent past, efforts have been made to enhance alkane production, although with a little gain in yield, leaving space for much improvement. Genetic manipulation in cyanobacteria is considered challenging, but recent advancements in genetic engineering tools may assist in manipulating the genome in order to enhance alkane production. Further, advancement in a basic understanding of metabolic pathways and gene functioning will guide future research for harvesting the potential of these tiny photosynthetically efficient factories. In this review, our focus would be to highlight the current knowledge available on cyanobacterial alkane production, and the potential aspects of developing cyanobacterium as an economical source of biofuel. Further insights into different metabolic pathways and hosts explored so far, and possible challenges in scaling up the production of alkanes will also be discussed.
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Affiliation(s)
- Humaira Parveen
- Microbial Engineering Group, International Centre for Genetic Engineering and Biotechnology, New Delhi 110067 India
| | - Syed Shams Yazdani
- Microbial Engineering Group, International Centre for Genetic Engineering and Biotechnology, New Delhi 110067 India
- DBT-ICGEB Centre for Advanced Bioenergy Research, International Centre for Genetic Engineering and Biotechnology, New Delhi 110067, India
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5
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Banerjee R, Srinivas V, Lebrette H. Ferritin-Like Proteins: A Conserved Core for a Myriad of Enzyme Complexes. Subcell Biochem 2022; 99:109-153. [PMID: 36151375 DOI: 10.1007/978-3-031-00793-4_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Ferritin-like proteins share a common fold, a four α-helix bundle core, often coordinating a pair of metal ions. Although conserved, the ferritin fold permits a diverse set of reactions, and is central in a multitude of macromolecular enzyme complexes. Here, we emphasize this diversity through three members of the ferritin-like superfamily: the soluble methane monooxygenase, the class I ribonucleotide reductase and the aldehyde deformylating oxygenase. They all rely on dinuclear metal cofactors to catalyze different challenging oxygen-dependent reactions through the formation of multi-protein complexes. Recent studies using cryo-electron microscopy, serial femtosecond crystallography at an X-ray free electron laser source, or single-crystal X-ray diffraction, have reported the structures of the active protein complexes, and revealed unprecedented insights into the molecular mechanisms of these three enzymes.
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Affiliation(s)
- Rahul Banerjee
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
| | - Vivek Srinivas
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Hugo Lebrette
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
- Laboratoire de Microbiologie et Génétique Moléculaires (LMGM), Centre de Biologie Intégrative (CBI), CNRS, UPS, Université de Toulouse, Toulouse, France.
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6
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Vuorio E, Thiel K, Fitzpatrick D, Huokko T, Kämäräinen J, Dandapani H, Aro EM, Kallio P. Hydrocarbon Desaturation in Cyanobacterial Thylakoid Membranes Is Linked With Acclimation to Suboptimal Growth Temperatures. Front Microbiol 2021; 12:781864. [PMID: 34899663 PMCID: PMC8661006 DOI: 10.3389/fmicb.2021.781864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Accepted: 10/26/2021] [Indexed: 11/28/2022] Open
Abstract
The ability to produce medium chain length aliphatic hydrocarbons is strictly conserved in all photosynthetic cyanobacteria, but the molecular function and biological significance of these compounds still remain poorly understood. This study gives a detailed view to the changes in intracellular hydrocarbon chain saturation in response to different growth temperatures and osmotic stress, and the associated physiological effects in the model cyanobacterium Synechocystis sp. PCC 6803. We show that the ratio between the representative hydrocarbons, saturated heptadecane and desaturated heptadecene, is reduced upon transition from 38°C toward 15°C, while the total content is not much altered. In parallel, it appears that in the hydrocarbon-deficient ∆ado (aldehyde deformylating oxygenase) mutant, phenotypic and metabolic changes become more evident under suboptimal temperatures. These include hindered growth, accumulation of polyhydroxybutyrate, altered pigment profile, restricted phycobilisome movement, and ultimately reduced CO2 uptake and oxygen evolution in the ∆ado strain as compared to Synechocystis wild type. The hydrocarbons are present in relatively low amounts and expected to interact with other nonpolar cellular components, including the hydrophobic part of the membrane lipids. We hypothesize that the function of the aliphatic chains is specifically associated with local fluidity effects of the thylakoid membrane, which may be required for the optimal movement of the integral components of the photosynthetic machinery. The findings support earlier studies and expand our understanding of the biological role of aliphatic hydrocarbons in acclimation to low temperature in cyanobacteria and link the proposed role in the thylakoid membrane to changes in photosynthetic performance, central carbon metabolism, and cell growth, which need to be effectively fine-tuned under alternating conditions in nature.
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Affiliation(s)
| | | | | | | | | | | | - Eva-Mari Aro
- Molecular Plant Biology, Department of Life Technologies, University of Turku, Turku, Finland
| | - Pauli Kallio
- Molecular Plant Biology, Department of Life Technologies, University of Turku, Turku, Finland
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7
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Biophysical and structural studies reveal marginal stability of a crucial hydrocarbon biosynthetic enzyme acyl ACP reductase. Sci Rep 2021; 11:12045. [PMID: 34103559 PMCID: PMC8187606 DOI: 10.1038/s41598-021-91232-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2020] [Accepted: 05/19/2021] [Indexed: 11/22/2022] Open
Abstract
Acyl-ACP reductase (AAR) is one of the two key cyanobacterial enzymes along with aldehyde deformylating oxygenase (ADO) involved in the synthesis of long-chain alkanes, a drop-in biofuel. The enzyme is prone to aggregation when expressed in Escherichia coli, leading to varying alkane levels. The present work attempts to investigate the crucial structural aspects of AAR protein associated with its stability and folding. Characterization by dynamic light scattering experiment and intact mass spectrometry revealed that recombinantly expressed AAR in E. coli existed in multiple-sized protein particles due to diverse lipidation. Interestingly, while thermal- and urea-based denaturation of AAR showed 2-state unfolding transition in circular dichroism and intrinsic fluorescent spectroscopy, the unfolding process of AAR was a 3-state pathway in GdnHCl solution suggesting that the protein milieu plays a significant role in dictating its folding. Apparent standard free energy \documentclass[12pt]{minimal}
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\begin{document}$$\left( {\Delta {\text{G}}_{{{\text{NU}}}}^{{{\text{H}}_{2} {\text{O}}}} } \right)$$\end{document}ΔGNUH2O of ~ 4.5 kcal/mol for the steady-state unfolding of AAR indicated borderline stability of the protein. Based on these evidences, we propose that the marginal stability of AAR are plausible contributing reasons for aggregation propensity and hence the low catalytic activity of the enzyme when expressed in E. coli for biofuel production. Our results show a path for building superior biocatalyst for higher biofuel production.
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8
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Hu Y, Zhu Z, Nielsen J, Siewers V. Engineering Saccharomyces cerevisiae cells for production of fatty acid-derived biofuels and chemicals. Open Biol 2020; 9:190049. [PMID: 31088249 PMCID: PMC6544985 DOI: 10.1098/rsob.190049] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The yeast Saccharomyces cerevisiae is a widely used cell factory for the production of fuels and chemicals, in particular ethanol, a biofuel produced in large quantities. With a need for high-energy-density fuels for jets and heavy trucks, there is, however, much interest in the biobased production of hydrocarbons that can be derived from fatty acids. Fatty acids also serve as precursors to a number of oleochemicals and hence provide interesting platform chemicals. Here, we review the recent strategies applied to metabolic engineering of S. cerevisiae for the production of fatty acid-derived biofuels and for improvement of the titre, rate and yield (TRY). This includes, for instance, redirection of the flux towards fatty acids through engineering of the central carbon metabolism, balancing the redox power and varying the chain length of fatty acids by enzyme engineering. We also discuss the challenges that currently hinder further TRY improvements and the potential solutions in order to meet the requirements for commercial application.
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Affiliation(s)
- Yating Hu
- 1 Department of Biology and Biological Engineering, Chalmers University of Technology , 41296 Gothenburg , Sweden.,2 Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology , 41296 Gothenburg , Sweden
| | - Zhiwei Zhu
- 1 Department of Biology and Biological Engineering, Chalmers University of Technology , 41296 Gothenburg , Sweden.,2 Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology , 41296 Gothenburg , Sweden
| | - Jens Nielsen
- 1 Department of Biology and Biological Engineering, Chalmers University of Technology , 41296 Gothenburg , Sweden.,2 Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology , 41296 Gothenburg , Sweden.,3 Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark , 2800 Kgs Lyngby , Denmark.,4 BioInnovation Institute , Ole Måløes Vej, 2200 Copenhagen N , Denmark
| | - Verena Siewers
- 1 Department of Biology and Biological Engineering, Chalmers University of Technology , 41296 Gothenburg , Sweden.,2 Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology , 41296 Gothenburg , Sweden
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9
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Shakeel T, Fatma Z, Yazdani SS. In vivo Quantification of Alkanes in Escherichia coli. Bio Protoc 2020; 10:e3593. [PMID: 33659559 DOI: 10.21769/bioprotoc.3593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 02/11/2020] [Accepted: 02/12/2020] [Indexed: 11/02/2022] Open
Abstract
Microbial production of alkanes employing synthetic biology tools has gained tremendous attention owing to the high energy density and similarity of alkanes to existing petroleum fuels. One of the most commonly studied pathways includes the production of alkanes by AAR (acyl-ACP (acyl carrier protein) reductase)-ADO (aldehyde deformylating oxygenase) pathway. Here, the intermediates of fatty acid synthesis pathway are used as substrate by the AAR enzyme to make fatty aldehyde, which is then deformylated by ADO to make linear chain alkane. However, the variation in substrate availability to the first enzyme of the pathway, i.e., AAR, via fatty acid synthesis pathway and low turnover of the ADO enzyme make calculation of yields and titers under in vivo conditions extremely difficult. In vivo assay employing external addition of defined substrates for ADO enzyme into the medium helps to monitor the influx of substrate hence providing a more accurate measurement of the product yields. In this protocol, we include a detailed guide for implementing the in vivo assay for monitoring alkane production in E. coli.
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Affiliation(s)
- Tabinda Shakeel
- Microbial Engineering Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India.,DBT-ICGEB Centre for Advanced Bioenergy Research, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Zia Fatma
- Microbial Engineering Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India.,DBT-ICGEB Centre for Advanced Bioenergy Research, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
| | - Syed Shams Yazdani
- Microbial Engineering Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, India.,DBT-ICGEB Centre for Advanced Bioenergy Research, International Centre for Genetic Engineering and Biotechnology, New Delhi, India
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10
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Building cell factories for the production of advanced fuels. Biochem Soc Trans 2020; 47:1701-1714. [PMID: 31803925 DOI: 10.1042/bst20190168] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 11/13/2019] [Accepted: 11/15/2019] [Indexed: 12/31/2022]
Abstract
Synthetic biology-based engineering strategies are being extensively employed for microbial production of advanced fuels. Advanced fuels, being comparable in energy efficiency and properties to conventional fuels, have been increasingly explored as they can be directly incorporated into the current fuel infrastructure without the need for reconstructing the pre-existing set-up rendering them economically viable. Multiple metabolic engineering approaches have been used for rewiring microbes to improve existing or develop newly programmed cells capable of efficient fuel production. The primary challenge in using these approaches is improving the product yield for the feasibility of the commercial processes. Some of the common roadblocks towards enhanced fuel production include - limited availability of flux towards precursors and desired pathways due to presence of competing pathways, limited cofactor and energy supply in cells, the low catalytic activity of pathway enzymes, obstructed product transport, and poor tolerance of host cells for end products. Consequently, despite extensive studies on the engineering of microbial hosts, the costs of industrial-scale production of most of these heterologously produced fuel compounds are still too high. Though considerable progress has been made towards successfully producing some of these biofuels, a substantial amount of work needs to be done for improving the titers of others. In this review, we have summarized the different engineering strategies that have been successfully used for engineering pathways into commercial hosts for the production of advanced fuels and different approaches implemented for tuning host strains and pathway enzymes for scaling up production levels.
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11
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Jaroensuk J, Intasian P, Wattanasuepsin W, Akeratchatapan N, Kesornpun C, Kittipanukul N, Chaiyen P. Enzymatic reactions and pathway engineering for the production of renewable hydrocarbons. J Biotechnol 2020; 309:1-19. [DOI: 10.1016/j.jbiotec.2019.12.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 12/14/2019] [Accepted: 12/15/2019] [Indexed: 01/23/2023]
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12
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Kudo H, Hayashi Y, Arai M. Improving hydrocarbon production by engineering cyanobacterial acyl-(acyl carrier protein) reductase. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:291. [PMID: 31890019 PMCID: PMC6916063 DOI: 10.1186/s13068-019-1623-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2019] [Accepted: 11/27/2019] [Indexed: 05/31/2023]
Abstract
BACKGROUND Acyl-(acyl carrier protein (ACP)) reductase (AAR) is a key enzyme for hydrocarbon biosynthesis in cyanobacteria, reducing fatty acyl-ACPs to aldehydes, which are then converted into hydrocarbons by aldehyde-deformylating oxygenase (ADO). Previously, we compared AARs from various cyanobacteria and found that hydrocarbon yield in Escherichia coli coexpressing AAR and ADO was highest for AAR from Synechococcus elongatus PCC 7942 (7942AAR), which has high substrate affinity for 18-carbon fatty acyl-ACP, resulting in production of mainly heptadecene. In contrast, the hydrocarbon yield was lowest for AAR from Synechococcus sp. PCC 7336 (7336AAR), which has a high specificity for 16-carbon substrates, leading to production of mainly pentadecane. However, even the most productive AAR (7942AAR) still showed low activity; thus, residues within AAR that are nonconserved, but may still be important in hydrocarbon production need to be identified to engineer enzymes with improved hydrocarbon yields. Moreover, AAR mutants that favor shorter alkane production will be useful for producing diesel fuels with decreased freezing temperatures. Here, we aimed to identify such residues and design a highly productive and specific enzyme for hydrocarbon biosynthesis in E. coli. RESULTS We introduced single amino acid substitutions into the least productive AAR (7336AAR) to make its amino acid sequence similar to that of the most productive enzyme (7942AAR). From the analysis of 41 mutants, we identified 6 mutations that increased either the activity or amount of soluble AAR, leading to a hydrocarbon yield improvement in E. coli coexpressing ADO. Moreover, by combining these mutations, we successfully created 7336AAR mutants with ~ 70-fold increased hydrocarbon production, especially for pentadecane, when compared with that of wild-type 7336AAR. Strikingly, the hydrocarbon yield was higher in the multiple mutants of 7336AAR than in 7942AAR. CONCLUSIONS We successfully designed AAR mutants that, when coexpressed with ADO in E. coli, are more highly effective in hydrocarbon production, especially for pentadecane, than wild-type AARs. Our results provide a series of highly productive AARs with different substrate specificities, enabling the production of a variety of hydrocarbons in E. coli that may be used as biofuels.
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Affiliation(s)
- Hisashi Kudo
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902 Japan
| | - Yuuki Hayashi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902 Japan
| | - Munehito Arai
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902 Japan
- Department of Physics, Graduate School of Science, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo 153-8902 Japan
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13
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Chang M, Shimba K, Hayashi Y, Arai M. Electrostatic interactions at the interface of two enzymes are essential for two-step alkane biosynthesis in cyanobacteria. Biosci Biotechnol Biochem 2019; 84:228-237. [PMID: 31601165 DOI: 10.1080/09168451.2019.1677142] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Cyanobacterial alkane biosynthesis is catalyzed by acyl-(acyl carrier protein (ACP)) reductase (AAR) and aldehyde-deformylating oxygenase (ADO) in a two-step reaction. AAR reduces acyl-ACPs to fatty aldehydes, which are then converted by ADO to alkanes, the main components of diesel fuel. Interaction between AAR and ADO allows AAR to efficiently deliver the aldehyde to ADO. However, this interaction is poorly understood. Here, using analytical size-exclusion chromatography (SEC), we show that electrostatic interactions play an important role in the binding of the two enzymes. Alanine-scanning mutagenesis at charged residues around the substrate entry site of ADO revealed that E201A mutation greatly reduced hydrocarbon production. SEC measurement of the mutant demonstrated that E201 of ADO is essential for the AAR-ADO interaction. Our results suggest that AAR binds to the substrate entrance gate of ADO and thereby facilitates the insertion of the reactive and relatively insoluble aldehyde into the hydrophobic channel of ADO.Abbreviations: AAR: acyl-ACP reductase; ACP: acyl carrier protein; ADO: aldehyde-deformylating oxygenase; ASA: solvent accessible surface area; BSA: bovine serum albumin; CD: circular dichroism; DMSO: dimethyl sulfoxide; DTT: dithiothreitol; GC-MS: gas chromatography-mass spectrometer; HPLC: high-performance liquid chromatography; IPTG: isopropyl-β-D-thiogalactoside; MRE: mean residue ellipticity; NpAAR: AAR from Nostoc punctiforme PCC 73102; NpADO: ADO from Nostoc punctiforme PCC 73102; PmADO: ADO from Prochlorococcus marinus MIT 9313; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis; SeAAR: AAR from Synechococcus elongatus PCC 7942; SeADO: ADO from Synechococcus elongatus PCC 7942; SEC: size-exclusion chromatography; TeAAR: AAR from Thermosynechococcus elongatus BP-1; TeADO: ADO from Thermosynechococcus elongatus BP-1; UV: ultraviolet.
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Affiliation(s)
- Mari Chang
- Department of Physics, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Keigo Shimba
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Yuuki Hayashi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Munehito Arai
- Department of Physics, Graduate School of Science, The University of Tokyo, Tokyo, Japan.,Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
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14
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Kudo H, Hayashi Y, Arai M. Identification of non-conserved residues essential for improving the hydrocarbon-producing activity of cyanobacterial aldehyde-deformylating oxygenase. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:89. [PMID: 31015863 PMCID: PMC6469105 DOI: 10.1186/s13068-019-1409-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 03/14/2019] [Indexed: 05/25/2023]
Abstract
BACKGROUND Cyanobacteria produce hydrocarbons corresponding to diesel fuels by means of aldehyde-deformylating oxygenase (ADO). ADO catalyzes a difficult and unusual reaction in the conversion of aldehydes to hydrocarbons and has been widely used for biofuel production in metabolic engineering; however, its activity is low. A comparison of the amino acid sequences of highly active and less active ADOs will elucidate non-conserved residues that are essential for improving the hydrocarbon-producing activity of ADOs. RESULTS Here, we measured the activities of ADOs from 10 representative cyanobacterial strains by expressing each of them in Escherichia coli and quantifying the hydrocarbon yield and amount of soluble ADO. We demonstrated that the activity was highest for the ADO from Synechococcus elongatus PCC 7942 (7942ADO). In contrast, the ADO from Gloeobacter violaceus PCC 7421 (7421ADO) had low activity but yielded high amounts of soluble protein, resulting in a high production level of hydrocarbons. By introducing 37 single amino acid substitutions at the non-conserved residues of the less active ADO (7421ADO) to make its sequence more similar to that of the highly active ADO (7942ADO), we found 20 mutations that improved the activity of 7421ADO. In addition, 13 other mutations increased the amount of soluble ADO while maintaining more than 80% of wild-type activity. Correlation analysis showed a solubility-activity trade-off in ADO, in which activity was negatively correlated with solubility. CONCLUSIONS We succeeded in identifying non-conserved residues that are essential for improving ADO activity. Our results may be useful for generating combinatorial mutants of ADO that have both higher activity and higher amounts of the soluble protein in vivo, thereby producing higher yields of biohydrocarbons.
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Affiliation(s)
- Hisashi Kudo
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo, 153-8902 Japan
| | - Yuuki Hayashi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo, 153-8902 Japan
| | - Munehito Arai
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo, 153-8902 Japan
- Department of Physics, Graduate School of Science, The University of Tokyo, 3-8-1 Komaba, Meguro, Tokyo, 153-8902 Japan
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Lehtinen T, Virtanen H, Santala S, Santala V. Production of alkanes from CO 2 by engineered bacteria. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:228. [PMID: 30151056 PMCID: PMC6102805 DOI: 10.1186/s13068-018-1229-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Accepted: 08/14/2018] [Indexed: 06/08/2023]
Abstract
BACKGROUND Microbial biosynthesis of alkanes is considered a promising method for the sustainable production of drop-in fuels and chemicals. Carbon dioxide would be an ideal carbon source for these production systems, but efficient production of long carbon chains from CO2 is difficult to achieve in a single organism. A potential solution is to employ acetogenic bacteria for the reduction of CO2 to acetate, and engineer a second organism to convert the acetate into long-chain hydrocarbons. RESULTS In this study, we demonstrate alkane production from CO2 by a system combining the acetogen Acetobacterium woodii and a non-native alkane producer Acinetobacter baylyi ADP1 engineered for alkane production. Nine synthetic two-step alkane biosynthesis pathways consisting of different aldehyde- and alkane-producing enzymes were combinatorically constructed and expressed in A. baylyi. The aldehyde-producing enzymes studied were AAR from Synechococcus elongatus, Acr1 from A. baylyi, and a putative dehydrogenase from Nevskia ramosa. The alkane-producing enzymes were ADOs from S. elongatus and Nostoc punctiforme, and CER1 from Arabidopsis thaliana. The performance of the pathways was evaluated with a twin-layer biosensor, which allowed the monitoring of both the intermediate (fatty aldehyde), and end product (alkane) formation. The highest alkane production, as indicated by the biosensor, was achieved with a pathway consisting of AAR and ADO from S. elongatus. The performance of this pathway was further improved by balancing the relative expression levels of the enzymes to limit the accumulation of the intermediate fatty aldehyde. Finally, the acetogen A. woodii was used to produce acetate from CO2 and H2, and the acetate was used for alkane production by the engineered A. baylyi, thereby leading to the net production of long-chain alkanes from CO2. CONCLUSIONS A modular system for the production of drop-in liquid fuels from CO2 was demonstrated. Among the studied synthetic pathways, the combination of ADO and AAR from S. elongatus was found to be the most efficient in heterologous alkane production in A. baylyi. Furthermore, limiting the accumulation of the fatty aldehyde intermediate was found to be beneficial for the alkane production. Nevertheless, the alkane productivity of the system remained low, representing a major challenge for future research.
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Affiliation(s)
- Tapio Lehtinen
- Department of Chemistry and Bioengineering, Tampere University of Technology, Korkeakoulunkatu 8, 33720 Tampere, Finland
| | - Henri Virtanen
- Department of Chemistry and Bioengineering, Tampere University of Technology, Korkeakoulunkatu 8, 33720 Tampere, Finland
| | - Suvi Santala
- Department of Chemistry and Bioengineering, Tampere University of Technology, Korkeakoulunkatu 8, 33720 Tampere, Finland
| | - Ville Santala
- Department of Chemistry and Bioengineering, Tampere University of Technology, Korkeakoulunkatu 8, 33720 Tampere, Finland
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Arai M, Hayashi Y, Kudo H. Cyanobacterial Enzymes for Bioalkane Production. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1080:119-154. [PMID: 30091094 DOI: 10.1007/978-981-13-0854-3_6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cyanobacterial biosynthesis of alkanes is an attractive way of producing substitutes for petroleum-based fuels. Key enzymes for bioalkane production in cyanobacteria are acyl-ACP reductase (AAR) and aldehyde-deformylating oxygenase (ADO). AAR catalyzes the reduction of the fatty acyl-ACP/CoA substrates to fatty aldehydes, which are then converted into alkanes/alkenes by ADO. These enzymes have been widely used for biofuel production by metabolic engineering of cyanobacteria and other organisms. However, both proteins, particularly ADO, have low enzymatic activities, and their catalytic activities are desired to be improved for use in biofuel production. Recently, progress has been made in the basic sciences and in the application of AAR and ADO in alkane production. This chapter provides an overview of recent advances in the study of the structure and function of AAR and ADO, protein engineering of these enzymes for improving activity and modifying substrate specificities, and examples of metabolic engineering of cyanobacteria and other organisms using AAR and ADO for biofuel production.
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Affiliation(s)
- Munehito Arai
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.
| | - Yuuki Hayashi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Hisashi Kudo
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
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17
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Lehtinen T, Efimova E, Santala S, Santala V. Improved fatty aldehyde and wax ester production by overexpression of fatty acyl-CoA reductases. Microb Cell Fact 2018; 17:19. [PMID: 29422050 PMCID: PMC5806253 DOI: 10.1186/s12934-018-0869-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 02/01/2018] [Indexed: 12/31/2022] Open
Abstract
Background Fatty aldehydes are industrially relevant compounds, which also represent a common metabolic intermediate in the microbial synthesis of various oleochemicals, including alkanes, fatty alcohols and wax esters. The key enzymes in biological fatty aldehyde production are the fatty acyl-CoA/ACP reductases (FARs) which reduce the activated acyl molecules to fatty aldehydes. Due to the disparity of FARs, identification and in vivo characterization of reductases with different properties are needed for the construction of tailored synthetic pathways for the production of various compounds. Results Fatty aldehyde production in Acinetobacter baylyi ADP1 was increased by the overexpression of three different FARs: a native A. baylyi FAR Acr1, a cyanobacterial Aar, and a putative, previously uncharacterized dehydrogenase (Ramo) from Nevskia ramosa. The fatty aldehyde production was followed in real-time inside the cells with a luminescence-based tool, and the highest aldehyde production was achieved with Aar. The fate of the overproduced fatty aldehydes was studied by measuring the production of wax esters by a native downstream pathway of A. baylyi, for which fatty aldehyde is a specific intermediate. The wax ester production was improved with the overexpression of Acr1 or Ramo compared to the wild type A. baylyi by more than two-fold, whereas the expression of Aar led to only subtle wax ester production. The overexpression of FARs did not affect the length of the acyl chains of the wax esters. Conclusions The fatty aldehyde production, as well as the wax ester production of A. baylyi, was improved with the overexpression of a key enzyme in the pathway. The wax ester titer (0.45 g/l) achieved with the overexpression of Acr1 is the highest reported without hydrocarbon supplementation to the culture. The contrasting behavior of the different reductases highlight the significance of in vivo characterization of enzymes and emphasizes the possibilities provided by the diversity of FARs for pathway and product modulation. Electronic supplementary material The online version of this article (10.1186/s12934-018-0869-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Tapio Lehtinen
- Department of Chemistry and Bioengineering, Tampere University of Technology, Tampere, Finland.
| | - Elena Efimova
- Department of Chemistry and Bioengineering, Tampere University of Technology, Tampere, Finland
| | - Suvi Santala
- Department of Chemistry and Bioengineering, Tampere University of Technology, Tampere, Finland
| | - Ville Santala
- Department of Chemistry and Bioengineering, Tampere University of Technology, Tampere, Finland
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