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Klein E, Wurst R, Rehnlund D, Gescher J. Elucidating the development of cooperative anode-biofilm-structures. Biofilm 2024; 7:100193. [PMID: 38601817 PMCID: PMC11004076 DOI: 10.1016/j.bioflm.2024.100193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2023] [Revised: 03/13/2024] [Accepted: 03/21/2024] [Indexed: 04/12/2024] Open
Abstract
Microbial electrochemical systems are a highly versatile platform technology with a particular focus on the interplay of chemical and electrical energy conversion and offer immense potential for a sustainable bioeconomy. The industrial realization of this potential requires a critical focus on biofilm optimization if performance is to be controlled over a long period of time. Moreover, the aspect and influence of cooperativity has to be addressed as many applied anodic bioelectrochemical systems will most likely be operated with a diversity of interacting microbial species. Hence, the aim of this study was to analyze how interspecies dependence and cooperativity of a model community influence the development of anodic biofilms. To investigate biofilm activity in a spatially resolved manner, a microfluidic bioelectrochemical flow cell was developed that can be equipped with user-defined electrode materials and operates under laminar flow conditions. With this infrastructure, the development of single and co-culture biofilms of the two model organisms Shewanella oneidensis and Geobacter sulfurreducens on graphite electrodes was monitored by optical coherence tomography analysis. The interdependence in the co-culture biofilm was achieved by feeding the community with lactate, which is converted by S. oneidensis into acetate, which in turn serves as substrate for G. sulfurreducens. The results show that co-cultivation resulted in the formation of denser biofilms than in single culture. Moreover, we hypothesize that S. oneidensis in return utilizes the conductive biofilm matrix build by G. sulfurreducens for direct interspecies electron transfer (DIET) to the anode. FISH analysis revealed that the biofilms consisted of approximately two-thirds G. sulfurreducens cells, which most likely formed a conductive 3D network throughout the biofilm matrix, in which evenly distributed tubular S. oneidensis colonies were embedded without direct contact to the anode surface. Live/dead staining shows that the outermost biofilm contained almost exclusively dead cells (98 %), layers near the anode contained 45-56 % and the entire biofilm contained 82 % live cells. Our results exemplify how the architecture of the exoelectrogenic biofilm dynamically adapts to the respective process conditions.
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Affiliation(s)
- Edina Klein
- Institute of Technical Microbiology, University of Technology Hamburg, Hamburg, Germany
| | - René Wurst
- Institute of Technical Microbiology, University of Technology Hamburg, Hamburg, Germany
| | - David Rehnlund
- Department of Chemistry – Ångström Laboratory, Uppsala University, Box 538, SE-751 21, Uppsala, Sweden
| | - Johannes Gescher
- Institute of Technical Microbiology, University of Technology Hamburg, Hamburg, Germany
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Philipp LA, Bühler K, Ulber R, Gescher J. Beneficial applications of biofilms. Nat Rev Microbiol 2024; 22:276-290. [PMID: 37957398 DOI: 10.1038/s41579-023-00985-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/05/2023] [Indexed: 11/15/2023]
Abstract
Many microorganisms live in the form of a biofilm. Although they are feared in the medical sector, biofilms that are composed of non-pathogenic organisms can be highly beneficial in many applications, including the production of bulk and fine chemicals. Biofilm systems are natural retentostats in which the biocatalysts can adapt and optimize their metabolism to different conditions over time. The adherent nature of biofilms allows them to be used in continuous systems in which the hydraulic retention time is much shorter than the doubling time of the biocatalysts. Moreover, the resilience of organisms growing in biofilms, together with the potential of uncoupling growth from catalytic activity, offers a wide range of opportunities. The ability to work with continuous systems using a potentially self-advancing whole-cell biocatalyst is attracting interest from a range of disciplines, from applied microbiology to materials science and from bioengineering to process engineering. The field of beneficial biofilms is rapidly evolving, with an increasing number of applications being explored, and the surge in demand for sustainable and biobased solutions and processes is accelerating advances in the field. This Review provides an overview of the research topics, challenges, applications and future directions in beneficial and applied biofilm research.
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Affiliation(s)
- Laura-Alina Philipp
- Hamburg University of Technology, Institute of Technical Microbiology, Hamburg, Germany
| | - Katja Bühler
- Department of Environmental Microbiology, Helmholtz-Centre for Environmental Research, Leipzig, Germany
| | - Roland Ulber
- RPTU Kaiserslautern-Landau, Institute of Bioprocess Engineering, Kaiserslautern, Germany
| | - Johannes Gescher
- Hamburg University of Technology, Institute of Technical Microbiology, Hamburg, Germany.
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Yang G, Xia X, Nie W, Qin B, Hou T, Lin A, Yao S, Zhuang L. Bidirectional extracellular electron transfer pathways of Geobacter sulfurreducens biofilms: Molecular insights into extracellular polymeric substances. ENVIRONMENTAL RESEARCH 2024; 245:118038. [PMID: 38147916 DOI: 10.1016/j.envres.2023.118038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 12/05/2023] [Accepted: 12/22/2023] [Indexed: 12/28/2023]
Abstract
The basis for bioelectrochemical technology is the capability of electroactive bacteria (EAB) to perform bidirectional extracellular electron transfer (EET) with electrodes, i.e. outward- and inward-EET. Extracellular polymeric substances (EPS) surrounding EAB are the necessary media for EET, but the biochemical and molecular analysis of EPS of Geobacter biofilms on electrode surface is largely lacked. This study constructed Geobacter sulfurreducens-biofilms performing bidirectional EET to explore the bidirectional EET mechanisms through EPS characterization using electrochemical, spectroscopic fingerprinting and proteomic techniques. Results showed that the inward-EET required extracellular redox proteins with lower formal potentials relative to outward-EET. Comparing to the EPS extracted from anodic biofilm (A-EPS), the EPS extracted from cathodic biofilm (C-EPS) exhibited a lower redox activity, mainly due to a decrease of protein/polysaccharide ratio and α-helix content of proteins. Furthermore, less cytochromes and more tyrosine- and tryptophan-protein like substances were detected in C-EPS than in A-EPS, indicating a diminished role of cytochromes and a possible role of other redox proteins in inward-EET. Proteomic analysis identified a variety of redox proteins including cytochrome, iron-sulfur clusters-containing protein, flavoprotein and hydrogenase in EPS, which might serve as an extracellular redox network for bidirectional EET. Those redox proteins that were significantly stimulated in A-EPS and C-EPS might be essential for outward- and inward-EET and warranted further research. This work sheds light on the mechanism of bidirectional EET of G. sulfurreducens biofilms and has implications in improving the performance of bioelectrochemical technology.
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Affiliation(s)
- Guiqin Yang
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 510632, China
| | - Xue Xia
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 510632, China
| | - Weijie Nie
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 510632, China
| | - Baoli Qin
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 510632, China
| | - Tiqun Hou
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 510632, China
| | - Annian Lin
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 510632, China
| | - Sijie Yao
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 510632, China
| | - Li Zhuang
- Guangdong Key Laboratory of Environmental Pollution and Health, School of Environment, Jinan University, Guangzhou, 510632, China.
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Michalska K, Brown RK, Schröder U. Carbon source priority and availability limit bidirectional electron transfer in freshwater mixed culture electrochemically active bacterial biofilms. BIORESOUR BIOPROCESS 2023; 10:64. [PMID: 38647932 PMCID: PMC10991894 DOI: 10.1186/s40643-023-00685-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 09/02/2023] [Indexed: 04/25/2024] Open
Abstract
This study investigated, if a mixed electroactive bacterial (EAB) culture cultivated heterotrophically at a positive applied potential could be adapted from oxidative to reductive or bidirectional extracellular electron transfer (EET). To this end, a periodic potential reversal regime between - 0.5 and 0.2 V vs. Ag/AgCl was applied. This yielded biofilm detachment and mediated electroautotrophic EET in combination with carbonate, i.e., dissolved CO2, as the sole carbon source, whereby the emerged mixed culture (S1) contained previously unknown EAB. Using acetate (S2) as well as a mixture of acetate and carbonate (S3) as the main carbon sources yielded primarily alternating electrogenic organoheterotropic metabolism with the higher maximum oxidation current densities recorded for mixed carbon media, exceeding on average 1 mA cm-2. More frequent periodic polarization reversal resulted in the increase of maximum oxidative current densities by about 50% for S2-BES and 80% for S3-BES, in comparison to half-batch polarization. The EAB mixed cultures developed accordingly, with S1 represented by mostly aerobes (84.8%) and being very different in composition to S2 and S3, dominated by anaerobes (96.9 and 96.5%, respectively). S2 and S3 biofilms remained attached to the electrodes. There was only minor evidence of fully reversible bidirectional EET. In conclusion the three triplicates fed with organic and/or inorganic carbon sources demonstrated two forms of diauxie: Firstly, S1-BES showed a preference for the electrode as the electron donor via mediated EET. Secondly, S2-BES and S3-BES showed a preference for acetate as electron donor and c-source, as long as this was available, switching to CO2 reduction, when acetate was depleted.
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Affiliation(s)
- Karina Michalska
- Institute of Biochemistry, University of Greifswald, Felix-Hausdorff-Str. 4, 17489, Greifswald, Germany
| | - Robert Keith Brown
- Institute of Biochemistry, University of Greifswald, Felix-Hausdorff-Str. 4, 17489, Greifswald, Germany
| | - Uwe Schröder
- Institute of Biochemistry, University of Greifswald, Felix-Hausdorff-Str. 4, 17489, Greifswald, Germany.
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Pereira J, Neves P, Nemanic V, Pereira MA, Sleutels T, Hamelers B, Heijne AT. Starvation combined with constant anode potential triggers intracellular electron storage in electro-active biofilms. WATER RESEARCH 2023; 242:120278. [PMID: 37413745 DOI: 10.1016/j.watres.2023.120278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Revised: 06/13/2023] [Accepted: 06/26/2023] [Indexed: 07/08/2023]
Abstract
The accumulation of electrons in the form of Extracellular Polymeric Substances (EPS) and poly-hydroxyalkanoates (PHA) has been studied in anaerobic processes by adjusting the access of microorganisms to the electron donor and final electron acceptor. In Bio-electrochemical systems (BESs), intermittent anode potential regimes have also recently been used to study electron storage in anodic electro-active biofilms (EABfs), but the effect of electron donor feeding mode on electron storage has not been explored. Therefore, in this study, the accumulation of electrons in the form of EPS and PHA was studied as a function of the operating conditions. EABfs were grown under both constant and intermittent anode potential regimes and fed with acetate (electron donor) continuously or in batch. Confocal Laser Scanning Microscopy (CLSM) and Fourier-Transform Infrared Spectroscopy (FTIR) were used to assess electron storage. The range of Coulombic efficiencies, from 25 to 82%, and the biomass yields, between 10 and 20%, indicate that storage could have been an alternative electron consuming process. From image processing, a 0.92 pixel ratio of poly-hydroxybutyrate (PHB) and amount of cells was found in the batch fed EABf grown under a constant anode potential. This storage was linked to the presence of living Geobacter and shows that energy gain and carbon source starvation were the triggers for intracellular electron storage. The highest EPS content (extracellular storage) was observed in the continuously fed EABf under an intermittent anode potential, showing that constant access to electron donor and intermittent access to the electron acceptor leads to the formation of EPS from the excess energy gained. Tailoring operating conditions can thus steer the microbial community and result in a trained EABf to perform a desired biological conversion, which can be beneficial for a more efficient and optimized BES.
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Affiliation(s)
- João Pereira
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA, Leeuwarden, the Netherlands; Environmental Technology, Wageningen University, Bornse Weilanden 9, P.O. Box 17, 6700 AA, Wageningen, the Netherlands
| | - Patrícia Neves
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA, Leeuwarden, the Netherlands; Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal
| | - Vivian Nemanic
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA, Leeuwarden, the Netherlands
| | - Maria Alcina Pereira
- Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal; LABBELS -Associate Laboratory, Braga/Guimarães, Portugal
| | - Tom Sleutels
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA, Leeuwarden, the Netherlands; Faculty of Science and Engineering, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, the Netherlands
| | - Bert Hamelers
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA, Leeuwarden, the Netherlands; Environmental Technology, Wageningen University, Bornse Weilanden 9, P.O. Box 17, 6700 AA, Wageningen, the Netherlands
| | - Annemiek Ter Heijne
- Environmental Technology, Wageningen University, Bornse Weilanden 9, P.O. Box 17, 6700 AA, Wageningen, the Netherlands.
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Martinez Ostormujof L, Teychené S, Achouak W, Fochesato S, Bakarat M, Rodriguez‐Ruiz I, Bergel A, Erable B. Systemic Analysis of the Spatiotemporal Changes in Multi‐Species Electroactive Biofilms to Clarify the Gradual Decline of Current Generation in Microbial Anodes. ChemElectroChem 2023. [DOI: 10.1002/celc.202201135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
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7
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Maximum thickness of non-buffer limited electro-active biofilms decreases at higher anode potentials. Biofilm 2022; 4:100092. [DOI: 10.1016/j.bioflm.2022.100092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 10/13/2022] [Accepted: 11/06/2022] [Indexed: 11/13/2022] Open
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Meng J, Duan H, Yuan Z, Zheng M. Gravity settling and centrifugation increase the acid buffer capacity of activated sludge. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 820:153231. [PMID: 35065124 DOI: 10.1016/j.scitotenv.2022.153231] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 01/13/2022] [Accepted: 01/13/2022] [Indexed: 06/14/2023]
Abstract
Buffer capacity is a critical parameter in sludge management of domestic wastewater treatment plants that determines acid/base usage. It is here shown that gravity settling or centrifugation significantly increased the buffer capacity in the supernatant of the sludge. The sludge thickening considerably elevated the total alkalinity of the sludge from 16.0 to 31.5 mgCaCO3 taking pH 5.0 for example with the sludge concentration times increasing from 2 to 20 times, while insignificantly affected the total acidity (initial 335.3 vs 240.2 mgCaCO3 at concentration times of 10 considering pH increased to 11.0). These findings indicate that the inherent buffer in sludge can be released during sludge thickening and the primary component of this buffer is alkalinity. The released buffer may be correlated to a negative surface charge inside sludge flocs, as it consumed base in titration. The increased buffer capacity in supernatant could be due to the buffer released from bound water to free water, and in particular, from the release of interstitial water, an important part of the bound water. Further mechanism analysis suggested that the increased buffer capacity in thickened sludge could relate to extracellular polymeric substances, for which more studies are needed. Overall, this study for the first time reports that sludge thickening can change the buffer capacity of sludge, affecting the efficiency and acid/base usage of sludge treatment.
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Affiliation(s)
- Jia Meng
- Australian Centre for Water and Environmental Biotechnology (ACWEB, formerly AWMC), The University of Queensland, Brisbane, QLD 4072, Australia; State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, 73 Huanghe Road, Harbin 150090, China
| | - Haoran Duan
- Australian Centre for Water and Environmental Biotechnology (ACWEB, formerly AWMC), The University of Queensland, Brisbane, QLD 4072, Australia
| | - Zhiguo Yuan
- Australian Centre for Water and Environmental Biotechnology (ACWEB, formerly AWMC), The University of Queensland, Brisbane, QLD 4072, Australia
| | - Min Zheng
- Australian Centre for Water and Environmental Biotechnology (ACWEB, formerly AWMC), The University of Queensland, Brisbane, QLD 4072, Australia.
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