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Noori MT, Rossi R, Logan BE, Min B. Hydrogen production in microbial electrolysis cells with biocathodes. Trends Biotechnol 2024:S0167-7799(23)00366-9. [PMID: 38360421 DOI: 10.1016/j.tibtech.2023.12.010] [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: 09/11/2023] [Revised: 12/17/2023] [Accepted: 12/29/2023] [Indexed: 02/17/2024]
Abstract
Electroautotrophic microbes at biocathodes in microbial electrolysis cells (MECs) can catalyze the hydrogen evolution reaction with low energy demand, facilitating long-term stable performance through specific and renewable biocatalysts. However, MECs have not yet reached commercialization due to a lack of understanding of the optimal microbial strains and reactor configurations for achieving high performance. Here, we critically analyze the criteria for the inocula selection, with a focus on the effect of hydrogenase activity and microbe-electrode interactions. We also evaluate the impact of the reactor design and key parameters, such as membrane type, composition, and electrode surface area on internal resistance, mass transport, and pH imbalances within MECs. This analysis paves the way for advancements that could propel biocathode-assisted MECs toward scalable hydrogen gas production.
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Affiliation(s)
- Md Tabish Noori
- Department of Environmental Science and Engineering, Kyung Hee University - Global Campus, Yongin-Si, South Korea
| | - Ruggero Rossi
- Department of Environmental Health and Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Bruce E Logan
- Department of Civil and Environmental Engineering, Penn State University, Pennsylvania, PA 16801, USA
| | - Booki Min
- Department of Environmental Science and Engineering, Kyung Hee University - Global Campus, Yongin-Si, South Korea.
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2
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Greening C, Kropp A, Vincent K, Grinter R. Developing high-affinity, oxygen-insensitive [NiFe]-hydrogenases as biocatalysts for energy conversion. Biochem Soc Trans 2023; 51:1921-1933. [PMID: 37743798 PMCID: PMC10657181 DOI: 10.1042/bst20230120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 09/13/2023] [Accepted: 09/14/2023] [Indexed: 09/26/2023]
Abstract
The splitting of hydrogen (H2) is an energy-yielding process, which is important for both biological systems and as a means of providing green energy. In biology, this reaction is mediated by enzymes called hydrogenases, which utilise complex nickel and iron cofactors to split H2 and transfer the resulting electrons to an electron-acceptor. These [NiFe]-hydrogenases have received considerable attention as catalysts in fuel cells, which utilise H2 to produce electrical current. [NiFe]-hydrogenases are a promising alternative to the platinum-based catalysts that currently predominate in fuel cells due to the abundance of nickel and iron, and the resistance of some family members to inhibition by gases, including carbon monoxide, which rapidly poison platinum-based catalysts. However, the majority of characterised [NiFe]-hydrogenases are inhibited by oxygen (O2), limiting their activity and stability. We recently reported the isolation and characterisation of the [NiFe]-hydrogenase Huc from Mycobacterium smegmatis, which is insensitive to inhibition by O2 and has an extremely high affinity, making it capable of oxidising H2 in air to below atmospheric concentrations. These properties make Huc a promising candidate for the development of enzyme-based fuel cells (EBFCs), which utilise H2 at low concentrations and in impure gas mixtures. In this review, we aim to provide context for the use of Huc for this purpose by discussing the advantages of [NiFe]-hydrogenases as catalysts and their deployment in fuel cells. We also address the challenges associated with using [NiFe]-hydrogenases for this purpose, and how these might be overcome to develop EBFCs that can be deployed at scale.
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Affiliation(s)
- Chris Greening
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia
- Securing Antarctica's Environmental Future, Monash University, Clayton, VIC 3800, Australia
- Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
- ARC Research Hub for Carbon Utilisation and Recycling, Monash University, Clayton, VIC 3800, Australia
| | - Ashleigh Kropp
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia
| | - Kylie Vincent
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford OX1 3QR, U.K
| | - Rhys Grinter
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia
- Centre for Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria 3052, Australia
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3
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Morra S. Fantastic [FeFe]-Hydrogenases and Where to Find Them. Front Microbiol 2022; 13:853626. [PMID: 35308355 PMCID: PMC8924675 DOI: 10.3389/fmicb.2022.853626] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 02/10/2022] [Indexed: 01/01/2023] Open
Abstract
[FeFe]-hydrogenases are complex metalloenzymes, key to microbial energy metabolism in numerous organisms. During anaerobic metabolism, they dissipate excess reducing equivalents by using protons from water as terminal electron acceptors, leading to hydrogen production. This reaction is coupled to reoxidation of specific redox partners [ferredoxins, NAD(P)H or cytochrome c3], that can be used either individually or simultaneously (via flavin-based electron bifurcation). [FeFe]-hydrogenases also serve additional physiological functions such as H2 uptake (oxidation), H2 sensing, and CO2 fixation. This broad functional spectrum is enabled by a modular architecture and vast genetic diversity, which is not fully explored and understood. This Mini Review summarises recent advancements in identifying and characterising novel [FeFe]-hydrogenases, which has led to expanding our understanding of their multiple roles in metabolism and functional mechanisms. For example, while numerous well-known [FeFe]-hydrogenases are irreversibly damaged by oxygen, some newly discovered enzymes display intrinsic tolerance. These findings demonstrate that oxygen sensitivity varies between different [FeFe]-hydrogenases: in some cases, protection requires the presence of exogenous compounds such as carbon monoxide or sulphide, while in other cases it is a spontaneous built-in mechanism that relies on a reversible conformational change. Overall, it emerges that additional research is needed to characterise new [FeFe]-hydrogenases as this will reveal further details on the physiology and mechanisms of these enzymes that will enable potential impactful applications.
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Affiliation(s)
- Simone Morra
- Faculty of Engineering, University of Nottingham, Nottingham, United Kingdom
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Ash PA, Kendall-Price SET, Evans RM, Carr SB, Brasnett AR, Morra S, Rowbotham JS, Hidalgo R, Healy AJ, Cinque G, Frogley MD, Armstrong FA, Vincent KA. The crystalline state as a dynamic system: IR microspectroscopy under electrochemical control for a [NiFe] hydrogenase. Chem Sci 2021; 12:12959-12970. [PMID: 34745526 PMCID: PMC8514002 DOI: 10.1039/d1sc01734a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 06/03/2021] [Indexed: 12/24/2022] Open
Abstract
Controlled formation of catalytically-relevant states within crystals of complex metalloenzymes represents a significant challenge to structure-function studies. Here we show how electrochemical control over single crystals of [NiFe] hydrogenase 1 (Hyd1) from Escherichia coli makes it possible to navigate through the full array of active site states previously observed in solution. Electrochemical control is combined with synchrotron infrared microspectroscopy, which enables us to measure high signal-to-noise IR spectra in situ from a small area of crystal. The output reports on active site speciation via the vibrational stretching band positions of the endogenous CO and CN- ligands at the hydrogenase active site. Variation of pH further demonstrates how equilibria between catalytically-relevant protonation states can be deliberately perturbed in the crystals, generating a map of electrochemical potential and pH conditions which lead to enrichment of specific states. Comparison of in crystallo redox titrations with measurements in solution or of electrode-immobilised Hyd1 confirms the integrity of the proton transfer and redox environment around the active site of the enzyme in crystals. Slowed proton-transfer equilibria in the hydrogenase in crystallo reveals transitions which are only usually observable by ultrafast methods in solution. This study therefore demonstrates the possibilities of electrochemical control over single metalloenzyme crystals in stabilising specific states for further study, and extends mechanistic understanding of proton transfer during the [NiFe] hydrogenase catalytic cycle.
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Affiliation(s)
- Philip A Ash
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
- School of Chemistry, University of Leicester Leicester LE1 7RH UK
- Leicester Institute of Structural and Chemical Biology, University of Leicester LE1 7RH UK
| | - Sophie E T Kendall-Price
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Rhiannon M Evans
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Stephen B Carr
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
- Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus Didcot UK
| | - Amelia R Brasnett
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Simone Morra
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Jack S Rowbotham
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Ricardo Hidalgo
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Adam J Healy
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Gianfelice Cinque
- Diamond Light Source, Harwell Science and Innovation Campus Didcot OX11 0QX UK
- Department of Engineering Sciences, University of Oxford Parks Road Oxford OX1 3PJ UK
| | - Mark D Frogley
- Diamond Light Source, Harwell Science and Innovation Campus Didcot OX11 0QX UK
| | - Fraser A Armstrong
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Kylie A Vincent
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
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Shepard EM, Impano S, Duffus BR, Pagnier A, Duschene KS, Betz JN, Byer AS, Galambas A, McDaniel EC, Watts H, McGlynn SE, Peters JW, Broderick WE, Broderick JB. HydG, the "dangler" iron, and catalytic production of free CO and CN -: implications for [FeFe]-hydrogenase maturation. Dalton Trans 2021; 50:10405-10422. [PMID: 34240096 DOI: 10.1039/d1dt01359a] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The organometallic H-cluster of the [FeFe]-hydrogenase consists of a [4Fe-4S] cubane bridged via a cysteinyl thiolate to a 2Fe subcluster ([2Fe]H) containing CO, CN-, and dithiomethylamine (DTMA) ligands. The H-cluster is synthesized by three dedicated maturation proteins: the radical SAM enzymes HydE and HydG synthesize the non-protein ligands, while the GTPase HydF serves as a scaffold for assembly of [2Fe]H prior to its delivery to the [FeFe]-hydrogenase containing the [4Fe-4S] cubane. HydG uses l-tyrosine as a substrate, cleaving it to produce p-cresol as well as the CO and CN- ligands to the H-cluster, although there is some question as to whether these are formed as free diatomics or as part of a [Fe(CO)2(CN)] synthon. Here we show that Clostridium acetobutylicum (C.a.) HydG catalyzes formation of multiple equivalents of free CO at rates comparable to those for CN- formation. Free CN- is also formed in excess molar equivalents over protein. A g = 8.9 EPR signal is observed for C.a. HydG reconstituted to load the 5th "dangler" iron of the auxiliary [4Fe-4S][FeCys] cluster and is assigned to this "dangler-loaded" cluster state. Free CO and CN- formation and the degree of activation of [FeFe]-hydrogenase all occur regardless of dangler loading, but are increased 10-35% in the dangler-loaded HydG; this indicates the dangler iron is not essential to this process but may affect relevant catalysis. During HydG turnover in the presence of myoglobin, the g = 8.9 signal remains unchanged, indicating that a [Fe(CO)2(CN)(Cys)] synthon is not formed at the dangler iron. Mutation of the only protein ligand to the dangler iron, H272, to alanine nearly completely abolishes both free CO formation and hydrogenase activation, however results show this is not due solely to the loss of the dangler iron. In experiments with wild type and H272A HydG, and with different degrees of dangler loading, we observe a consistent correlation between free CO/CN- formation and hydrogenase activation. Taken in full, our results point to free CO/CN-, but not an [Fe(CO)2(CN)(Cys)] synthon, as essential species in hydrogenase maturation.
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Affiliation(s)
- Eric M Shepard
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, MT 59717, USA.
| | - Stella Impano
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, MT 59717, USA.
| | - Benjamin R Duffus
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, MT 59717, USA.
| | - Adrien Pagnier
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, MT 59717, USA.
| | - Kaitlin S Duschene
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, MT 59717, USA.
| | - Jeremiah N Betz
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, MT 59717, USA.
| | - Amanda S Byer
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, MT 59717, USA.
| | - Amanda Galambas
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, MT 59717, USA.
| | - Elizabeth C McDaniel
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, MT 59717, USA.
| | - Hope Watts
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, MT 59717, USA.
| | - Shawn E McGlynn
- Earth-Life Science Institute, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - John W Peters
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99163, USA
| | - William E Broderick
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, MT 59717, USA.
| | - Joan B Broderick
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, MT 59717, USA.
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Bortolus M, Costantini P, Doni D, Carbonera D. Overview of the Maturation Machinery of the H-Cluster of [FeFe]-Hydrogenases with a Focus on HydF. Int J Mol Sci 2018; 19:E3118. [PMID: 30314343 PMCID: PMC6212873 DOI: 10.3390/ijms19103118] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 10/04/2018] [Accepted: 10/06/2018] [Indexed: 01/01/2023] Open
Abstract
Hydrogen production in nature is performed by hydrogenases. Among them, [FeFe]-hydrogenases have a peculiar active site, named H-cluster, that is made of two parts, synthesized in different pathways. The cubane sub-cluster requires the normal iron-sulfur cluster maturation machinery. The [2Fe] sub-cluster instead requires a dedicated set of maturase proteins, HydE, HydF, and HydG that work to assemble the cluster and deliver it to the apo-hydrogenase. In particular, the delivery is performed by HydF. In this review, we will perform an overview of the latest knowledge on the maturation machinery of the H-cluster, focusing in particular on HydF.
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Affiliation(s)
- Marco Bortolus
- Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy.
| | - Paola Costantini
- Department of Biology, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy.
| | - Davide Doni
- Department of Biology, University of Padova, Viale G. Colombo 3, 35131 Padova, Italy.
| | - Donatella Carbonera
- Department of Chemical Sciences, University of Padova, Via F. Marzolo 1, 35131 Padova, Italy.
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