Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
A New Approach for Evaluating Electron Transfer Dynamics by Using In Situ Resonance Raman Microscopy and Chronoamperometry in Conjunction with a Dynamic Model
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.ORCID iD: 0000-0002-3386-701x
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.ORCID iD: 0000-0003-3268-1691
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.ORCID iD: 0000-0002-1600-8424
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.ORCID iD: 0000-0003-0079-5950
Show others and affiliations
2020 (English)In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 86, no 20, article id e01535-20Article in journal (Refereed) Published
Abstract [en]

Geobacter sulfurreducens is a good candidate as a chassis-organism due to its ability to form thick, conductive biofilms, enabling long distance extracellular electron transfer (EET). Due to the complexity of EET pathways in G. sulfurreducens, a dynamic approach is required to study genetically modified EET rates in the biofilm. By coupling on-line resonance Raman microscopy with chronoamperometry, we were able to observe the dynamic discharge response in the biofilm's cytochromes to an increase in anode voltage. Measuring the heme redox state alongside the current allows for the fitting of a dynamic model using the current response and a subsequent validation of the model via the value of a reduced cytochrome c Raman peak. The modelled reduced cytochromes closely fitted the Raman response data from the G. sulfurreducens wild-type strain, showing the oxidation of heme groups in cytochromes until achieving a new steady state. Furthermore, the use of a dynamic model also allows for the calculation of internal rates, such as acetate and NADH consumption rates. The Raman response of a mutant lacking OmcS showed a sharper initial rate than predicted, followed by an almost linear decrease of the reduced mediators. The increased initial rate could be attributed to an increase in biofilm conductivity, previously observed in biofilms lacking OmcS. One explanation for this is that OmcS acts as a conduit between cytochromes; therefore deleting the gene restricts the electron transfer rate to the extracellular matrix. This could, however, be modelled assuming a linear oxidation rate of intercellular mediators.

IMPORTANCE Bioelectrochemical systems can fill a vast array of application niches, due to the control of redox reactions that it offers. Although native microorganisms are preferred for applications such as bioremediation, more control is required for applications such as biosensors or biocomputing. The development of a chassis organism, in which the EET is well defined and readily controllable, is therefore essential. The combined approach in this work offers a unique way of monitoring and describing the reaction kinetics of a G. sulfurreducens biofilm, as well as offering a dynamic model that can be used in conjunction with applications such as biosensors.

Place, publisher, year, edition, pages
American Society for Microbiology , 2020. Vol. 86, no 20, article id e01535-20
Keywords [en]
online resonance Raman, chronoamperometry, Electron transfer, Geobacter sulfurreducens, dynamics, bioelectrochemical system, OmcS
National Category
Applied Mechanics Bioprocess Technology
Research subject
Biochemical Process Engineering; Experimental Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-80312DOI: 10.1128/AEM.01535-20ISI: 000582928300026PubMedID: 32826217Scopus ID: 2-s2.0-85092681553OAI: oai:DiVA.org:ltu-80312DiVA, id: diva2:1456602
Funder
Vattenfall AB, 2017-04867Swedish Research Council, 2014-05906Swedish Foundation for Strategic Research
Note

Validerad;2020;Nivå 2;2020-10-27 (alebob)

Available from: 2020-08-05 Created: 2020-08-05 Last updated: 2023-09-05Bibliographically approved
In thesis
1. Sound, Light and Electricity: as applications and analysis techniques to study metabolic effect and biofilm characterization of Geobacter sulfurreducens
Open this publication in new window or tab >>Sound, Light and Electricity: as applications and analysis techniques to study metabolic effect and biofilm characterization of Geobacter sulfurreducens
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Electricity

Bio-electrochemical systems such as microbial fuel cells (MFCs) and microbial electrolysis cells have shown promise in wastewater treatment, bioremediation, desalination, carbon sequestration and as an alternative, renewable energy source. MFCs produces electricity via anaerobic oxidation of substrates with the subsequent extracellular electron transfer to an electrode. A wide variety of feedstocks have been researched, including various artificial and real wastewater sources as well as lignocellulosic material. Sweet sorghum, has been identified as a possible feedstock for electricity production in MFCs, using an anaerobic sludge inoculum, due to its high sugar content. To study sweet sorghum as an MFC feedstock a standard two chamber H-cell MFC was used, with an anaerobic sludge inoculum (Boden Biogas). A maximum voltage of 546±10 mV was obtained, and a maximum power and current density of 131±8 mW/m2 and 543±29 mA/m2 respectively. The substrate concentrations were monitored during the MFC operation, and the sugars were quickly fermented to volatile fatty acids which were then consumed during electricity generation. The power output was essentially independent of the substrate profile, with little difference between different VFAs. A more direct way was therefore needed to monitor the growth of an MFC biofilm as well as the effect of various substrates on extracellular electron transfer (EET).

Light

One option for the direct monitoring of a biofilm is to use Raman spectroscopy to monitor the redox status of the biofilm, since Raman can be used to detect the redox state heme groups. Therefore, resonance Raman spectroscopy was chosen to monitor the cytochrome redox of Geobacter sulfurreducens, is a well know electroactive microorganism commonly found in mixed culture MFCs. G. sulfurreducensis able to produce thick, conductive biofilms as well as high current densities in MFCs. Due to the large variety of cytochromes present in G. sulfurreducens, it has various intricate and adaptable EET pathways, which makes the characterization of the essential EET components difficult. Due to the resonance of the cytochromes found in G. sulfurreducens it is possible to measure the redox state of the biofilm using resonance Raman spectroscopy. This was used for on-line monitoring of various G. sulfurreducens mutants during MFC operation (including the wild type PCA, the ii enhanced KN400 strain capable of higher current densities, and two deficient strains missing key cytochromes involved in the EET, i.e. ΔOmcS and ΔpilA). From this, the applicability of resonance Raman spectroscopy was shown to provide a non-destructive analytical tool for the in-situ monitoring of the oxidation state of proteins responsible for the EET process and the dynamics thereof. Resonance Raman with short integration times was further used, along with a dynamic model, to describe the dynamics of the EET pathways in the wild type as well as in an OmcS deficient strain during a stepped chronoamperometry measurement. This showed a significant difference in EET dynamics between ΔOmcS and the wild type, which was not detectible in the chronoamperometry data alone. The ΔOmcS biofilm showed a linearly decreasing trend in the reduced cytochrome concentration. This was likely caused by the saturation of a limiting mediator, resulting in an oxidation rate that was independent of the mediator concentration. The ΔOmcS biofilms response could, however, be better modelled using an empirical zeroth order model. This analytical method could prove valuable for the establishment of G. sulfurreducens as a chassis microorganism, allowing one to observe the effect of genetic modification on EET mechanisms.

Sound

Furthermore, to see if an abiotic factor such as sound can affect the functions in bacterial cells, we selected to study the effect of ultrasound on the growth of G. sulfurreducens. G. sulfurreducens is a key candidate for the development of a chassis organism in bioelectrochemical systems, and an external abiotic method of affecting growth or metabolite production could be extremely beneficial. For this, a well-defined sonobioreactor was developed and modelled to study the effect of ultrasound on G. sulfurreducens. This resulted in a significant increase in malate production during the exponential phase of planktonic growth (11 mmol when sonicated vs the 5 mmol control). Transcriptomics was then used to determine the reason for the observed increase. Although there was a large variance in the samples, this was possibly linked to the overexpression of glycosyltransferases, which are known to play a role in membrane stability and bind malate. Finally, a low-cost modification, which modifies a standard 3D printer into a bio-printer was developed to print artificial biofilms for bio-electrochemical systems. This was then used to print an artificial biofilm of G. sulfurreducens, significantly reducing the time required to produce an established biofilm

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2020. p. 55
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
Keywords
MFC, Microbial fuel cell, Raman microscopy, BES, Geobacter sulfurreducens
National Category
Biological Sciences Industrial Biotechnology
Research subject
Biochemical Process Engineering
Identifiers
urn:nbn:se:ltu:diva-80314 (URN)978-91-7790-628-5 (ISBN)978-91-7790-629-2 (ISBN)
Public defence
2020-09-29, F1031, Luleå University of Technology, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 2017-04867Vattenfall AB, 2014-05906
Available from: 2020-08-10 Created: 2020-08-05 Last updated: 2023-09-05Bibliographically approved

Open Access in DiVA

No full text in DiVA

Other links

Publisher's full textPubMedScopus

Authority records

Krige, AdolfRamser, KerstinSjöblom, MagnusChristakopoulos, PaulRova, Ulrika

Search in DiVA

By author/editor
Krige, AdolfRamser, KerstinSjöblom, MagnusChristakopoulos, PaulRova, Ulrika
By organisation
Chemical EngineeringFluid and Experimental Mechanics
In the same journal
Applied and Environmental Microbiology
Applied MechanicsBioprocess Technology

Search outside of DiVA

GoogleGoogle Scholar

doi
pubmed
urn-nbn

Altmetric score

doi
pubmed
urn-nbn
Total: 239 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf