| 1. |
- Coman, Vasile, et al.
(author)
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A membrane-, mediator-, cofactor-less glucose/oxygen biofuel cell.
- 2008
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In: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 10:40, s. 6093-6096
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Journal article (peer-reviewed)abstract
- We report the fabrication and characterisation of a non-compartmentalised, mediator and cofactor free glucose-oxygen biofuel cell based on adsorbed enzymes exhibiting direct bioelectrocatalysis, viz. cellobiose dehydrogenase from Dichomera saubinetii and laccase from Trametes hirsuta as the anodic and cathodic bioelements, respectively, with the following characteristics: an open-circuit voltage of 0.73 V; a maximum power density of 5 muW cm(-2) at 0.5 V of the cell voltage and an estimated half-life of >38 h in air-saturated 0.1 M citrate-phosphate buffer, pH 4.5 containing 5 mM glucose.
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| 2. |
- Coman, Vasile, et al.
(author)
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Investigation of electron transfer between cellobiose dehydrogenase from Myriococcum Thermophilum and gold electrodes
- 2007
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In: Chemical Analysis. - 0009-2223. ; 52:6, s. 945-960
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Journal article (peer-reviewed)abstract
- Cellobiose dehydrogenase (CDH) is a monomeric protein consisting of two subdomains: a larger flavin-associated domain (DHcdh) and a smaller heme-binding domain (CYTcdh), connected via a protease cleavable linker region. In this study, the inter-domain electron transfer, using the CDH from the ascomycete fungus Myriococcum thermophilum and thiol (SAM) modified gold electrodes, was investigated with cyclic voltammetry and UV-VIS spectroelectrochemistry. The effect of the SAM and pH on the formal potential of the heme domain of CDH and on the current generated by the electrocatalytic oxidation of cellobiose and lactose was evaluated with voltammetric techniques. The oxidation-reduction midpoint potentials of the DHcdh, CYTcdh, and whole CDH unit were estimated at different pH values using a long-optical-pathway thin capillary-type spectroelectrochemical cell.
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| 3. |
- Harreither, Wolfgang, et al.
(author)
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Carbon Nanotube Fiber Microelectrodes Show a Higher Resistance to Dopamine Fouling
- 2013
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In: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 85:15, s. 7447-7453
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Journal article (peer-reviewed)abstract
- We have compared the properties and resistance to DA fouling of a carbon nanotube fiber (CNTF) microelectrode to a traditional carbon fiber (CF) microelectrode. These two materials show comparable electrochemical activities for outer-sphere and inner-sphere redox reactions. Although the CNTF might have a higher intrinsic RC constant, thus limiting its high-frequency behavior, the CNTF shows a significantly higher durability than the CF in terms of electrode stability. During constant oxidation of 100 mu M DA, the signal measured by the CNTF rnicroelectrode shows a 2-h window over which no decrease in current is observed. Under the same conditions, the current obtained at the CF microelectrode decreases by almost 50%. A model of the fouling process, assuming the formation of growing patches of insulator on the surface, has been compared to the data. This model is found to be in good agreement with our results and indicates a growth rate of the patches in the 0.1-2 nm s(-1) range.
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| 4. |
- Harreither, Wolfgang, et al.
(author)
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Catalytic Properties and Classification of Cellobiose Dehydrogenases from Ascomycetes
- 2011
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In: Applied and Environmental Microbiology. - 0099-2240. ; 77:5, s. 1804-1815
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Journal article (peer-reviewed)abstract
- Putative cellobiose dehydrogenase (CDH) genes are frequently discovered in various fungi by genome sequencing projects. The expression of CDH, an extracellular flavocytochrome, is well studied in white rot basidiomycetes and is attributed to extracellular lignocellulose degradation. CDH has also been reported for plant-pathogenic or saprotrophic ascomycetes, but the molecular and catalytic properties of these enzymes are currently less investigated. This study links various ascomycetous cdh genes with the molecular and catalytic characteristics of the mature proteins and suggests a differentiation of ascomycete class II CDHs into two subclasses, namely, class IIA and class IIB, in addition to the recently introduced class III of hypothetical ascomycete CDHs. This new classification is based on sequence and biochemical data obtained from sequenced fungal genomes and a screening of 40 ascomycetes. Thirteen strains showed CDH activity when they were grown on cellulose-based media, and Chaetomium atrobrunneum, Corynascus thermophilus, Dichomera saubinetii, Hypoxylon haematostroma, Neurospora crassa, and Stachybotrys bisbyi were selected for detailed studies. In these strains, one or two cdh-encoding genes were found that stem either from class IIA and contain a C-terminal carbohydrate-binding module or from class IIB without such a module. In several strains, both genes were found. Regarding substrate specificity, class IIB CDHs show a less pronounced substrate specificity for cellobiose than class IIA enzymes. A pH-dependent pattern of the intramolecular electron transfer was also observed, and the CDHs were classified into three groups featuring acidic, intermediate, or alkaline pH optima. The pH optimum, however, does not correlate with the CDH subclasses and is most likely a species-dependent adaptation to different habitats.
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| 5. |
- Harreither, Wolfgang, et al.
(author)
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Cysteine residues reduce the severity of dopamine electrochemical fouling
- 2016
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In: Electrochimica Acta. - : Elsevier BV. - 0013-4686. ; 210, s. 622-629
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Journal article (peer-reviewed)abstract
- The fouling of neurotransmitter during electrochemical detection can dramatically jeopardize the viability of the sensor. Several recent developments in electrode fabrication and design have helped mitigating this issue. For instance, carbon nanotube fiber (CNTF) electrodes were found to be more resistant to fouling than the traditional carbon fiber (CF) electrodes. Here, we investigate the fouling resistance of these two materials in the presence of albumin. Interestingly, our data shows that the presence of albumin reduces the impact of dopamine (DA) fouling in a dose-dependent manner. A protective effect from DA fouling was also observed for other thiol containing substances, thus hinting that the sulfur competes with the amine moiety for the nucleophilic binding to the oxidized catechol, a critical step initiating DA fouling, and therefore reduces the rate of DA polymerization on the electrode surface. Overall, this study furthers our understanding of the mechanisms controlling DA detection in situ, and suggests using solutions of albumin as a background for calibrating sensors.
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| 6. |
- Harreither, Wolfgang, et al.
(author)
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Investigation of graphite electrodes modified with cellobiose dehydrogenase from the ascomycete Myriococcum thermophilum
- 2007
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In: Electroanalysis. - : Wiley. - 1040-0397 .- 1521-4109. ; 19:2-3, s. 172-180
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Journal article (peer-reviewed)abstract
- The catalytic properties of cellobiose dehydrogenase (CDH) from the ascomycete fungus Myriococcum thermophilum adsorbed on a graphite electrode were investigated for a large variety of carbohydrate substrates. The effects of applied potential, pH and buffer composition were tested and optimized, and the most suitable conditions were used to evaluate the detection limit, linear range, and sensitivity of the sensor for different carbohydrates in the flow injection mode. Subsequently, the long term stability of the modified electrodes was determined. Additionally, the direct and mediated electron transfer between the active site of the enzyme and the electrode has been investigated by amperometric flow injection measurements in the absence and presence of the mediator 1,4-benzoquinone in the presence of cellobiose or lactose.
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| 7. |
- Harreither, Wolfgang, et al.
(author)
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Investigation of the pH-dependent electron transfer mechanism of ascomycetous class II cellobiose dehydrogenases on electrodes
- 2012
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In: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 28:16, s. 6714-6723
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Journal article (peer-reviewed)abstract
- Cellobiose dehydrogenase (CDH) is capable of direct electron transfer (DET) on various carbon and thiol-modified gold electrodes. As a result, these systems have been utilized as biocatalyst in biosensors and biofuel cell anodes. Class I CDHs, from basidiomycetous fungi, are highly specific to cellulose or lactose, and DET is only observed at pH values below 5.5. To extend the applicability of CDH-based electrodes, the catalytic properties and the behavior on electrode surfaces of ascomycetous class II CDHs from Chaetomium attrobrunneum, Corynascus thermophilus, Dichomera saubinetii, Hypoxylon haematostroma, Neurospora crassa, and Stachybotrys bisbyi were investigated. We found that class II CDHs have diverse properties but generally show a lower substrate specificity than class I CDHs by converting also glucose and maltose. Intramolecular electron transfer (IET) and DET at neutral and alkaline pH were observed and elucidated by steady-state kinetics, pre-steady-state kinetics, and electrochemical measurements. The CDHs ability to interact with the electron acceptor cytochrome c and to communicate with electrode surfaces through DET at various pH conditions was used to classify the investigated enzymes. In combination with stopped-flow measurements, a model for the kinetics of the pH-dependent IET is developed. The efficient glucose turnover at neutral/alkaline pH makes some of these new CDHs potential candidates for glucose biosensors and biofuel cell anodes. © 2012 American Chemical Society.
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| 8. |
- Harreither, Wolfgang, et al.
(author)
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Recombinantly produced cellobiose dehydrogenase from Corynascus thermophilus for glucose biosensors and biofuel cells
- 2012
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In: Biotechnology Journal. - : Wiley. - 1860-6768. ; 7:11
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Journal article (peer-reviewed)abstract
- Cellobiose dehydrogenase (CDH) is an emerging enzyme in the field of bioelectrocatalysis. Due to its flexible cytochrome domain, which acts as a built-in redox mediator, CDH is capable of direct electron transfer (DET) to electrode surfaces. This rare property is employed in mediatorless "third generation" biosensors. The ability of Corynascus thermophilus CDH to oxidize glucose under physiological conditions makes it a promising candidate for miniaturized glucose biosensors or glucose powered biofuel cell anodes. We report for the first time the electrochemical application and characterization of a recombinantly produced CDH in a glucose biosensor. Recombinant CDH from C. thermophilus (rCtCDH) was expressed by the methylotrophic yeast Pichia pastoris (376 U L-1, 132 mg L-1). A comparative characterization of rCtCDH and CtCDH shows identical pH optima, KM values and heme b midpoint potentials. In contrast, the specific activity of rCtCDH (2.84 U mg(-1)) and consequently the turnover numbers were similar to five-times lower than for CtCDH, which was caused by a sub-stoichiometric occupation of catalytic sites with flavin-adenin-dinukleotid (FAD). The performance of rCtCDH-modified electrodes demonstrates the suitability for electrochemical studies. This opens the possibility to engineer the substrate specificity of C. thermophilus CDH for specific carbohydrates by rational engineering or directed evolution.
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| 9. |
- Kovacs, Gabor, et al.
(author)
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Graphite electrodes modified with Neurospora crassa cellobiose dehydrogenase: Comparative electrochemical characterization under direct and mediated electron transfer
- 2012
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In: Bioelectrochemistry. - : Elsevier BV. - 1878-562X .- 1567-5394. ; 88, s. 84-91
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Journal article (peer-reviewed)abstract
- The electrochemical characterization of a class II cellobiose dehydrogenase (CDH), from the ascomycete fungus Neurospora crassa. adsorbed on graphite (G), was performed in regard to direct (DET) and mediated electron transfer (MET). The effects of the applied potential, mediator (1,4 benzoquinone) concentration and flow carrier pH on the amperometric response of the G/CDH modified electrodes were investigated under flow conditions. From the calibration curves, recorded at two pH values (5.2 and 7.0) for nine different sugars, the kinetic and the analytical parameters were evaluated under DET and MET operation modes. These results together with those obtained from long term operational stability measurements showed that: (i) for all nine investigated sugars the sensitivity was higher for MET than for DET and for pH 5.2 compared to pH 7.0; (ii) irrespective of DET or MET operation mode, the sensitivity of the new enzyme towards the investigated sugars decreased in the following sequence: cellobiose > lactose > (cellotriose approximate to cellopentaose) > > (maltotriose approximate to maltotetraose approximate to maltopentaose) > (maltose approximate to glucose); (iii) for all tested substrates, the apparent CDH affinity was roughly higher in DET than in MET operation mode. (C) 2012 Elsevier B.V. All rights reserved.
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| 10. |
- Ludwig, Roland, et al.
(author)
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Cellobiose Dehydrogenase: A Versatile Catalyst for Electrochemical Applications.
- 2010
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In: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 11, s. 2674-2697
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Journal article (peer-reviewed)abstract
- Cellobiose dehydrogenase catalyses the oxidation of aldoses-a simple reaction, a boring enzyme? No, neither for the envisaged bioelectrochemical applications nor mechanistically. The catalytic cycle of this flavocytochrome is complex and modulated by its flexible cytochrome domain, which acts as a built-in redox mediator. This intramolecular electron transfer is modulated by the pH, an adaptation to the environmental conditions encountered or created by the enzyme-producing fungi. The cytochrome domain forms the base from which electrons can jump to large terminal electron acceptors, such as redox proteins, and also enables by that path direct electron transfer from the catalytically active flavodehydrogenase domain to electrode surfaces. The application of electrochemical techniques to the elucidation of the molecular and catalytic properties of cellobiose dehydrogenase is discussed and compared to biochemical methods. The results lead to valuable insights into the function of this cellulose-bound enzyme, but also form the basis of exciting applications in biosensors, biofuel cells and bioelectrocatalysis.
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