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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 Res 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] [What about the content of this article? (0)] [Affiliation(s)] [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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Pereira J, Mediayati Y, van Veelen HPJ, Temmink H, Sleutels T, Hamelers B, Heijne AT. The effect of intermittent anode potential regimes on the morphology and extracellular matrix composition of electro-active bacteria. Biofilm 2022; 4:100064. [PMID: 34984335 PMCID: PMC8693015 DOI: 10.1016/j.bioflm.2021.100064] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 11/01/2021] [Accepted: 12/08/2021] [Indexed: 11/25/2022] Open
Abstract
Electro-active bacteria (EAB) can form biofilms on an anode (so-called bioanodes), and use the electrode as electron acceptor for oxidation of organics in wastewater. So far, bioanodes have mainly been investigated under a continuous anode potential, but intermittent anode potential has resulted in higher currents and different biofilm morphologies. However, little is known about how intermittent potential influences the electron balance in the anode compartment. In this study, we investigated electron balances of bioanodes at intermittent anode potential regimes. We used a transparent non-capacitive electrode that also allowed for in-situ quantification of the EAB using optical coherence tomography (OCT). We observed comparable current densities between continuous and intermittent bioanodes, and stored charge was similar for all the applied intermittent times (5 mC). Electron balances were further investigated by quantifying Extracellular Polymeric Substances (EPS), by analyzing the elemental composition of biomass, and by quantifying biofilm and planktonic cells. For all tested conditions, a charge balance of the anode compartment showed that more electrons were diverted to planktonic cells than biofilm. Besides, 27–43% of the total charge was detected as soluble EPS in intermittent bioanodes, whereas only 15% was found as soluble EPS in continuous bioanodes. The amount of proteins in the EPS of biofilms was higher for intermittent operated bioanodes (0.21 mg COD proteins mg COD biofilm−1) than for continuous operated bioanodes (0.05 mg COD proteins mg COD biofilm−1). OCT revealed patchy morphologies for biofilms under intermittent anode potential. Overall, this study helped understanding that the use of a non-capacitive electrode and intermittent anode potential deviated electrons to other processes other than electric current at the electrode by identifying electron sinks in the anolyte and quantifying the accumulation of electrons in the form of EPS. Continuous acetate feeding and intermittent anode potential lead to EPS production in electro-active bacteria. A charge balance was made including soluble EPS and planktonic cells. Patchy biofilm morphologies and more planktonic cells were observed when intermittent anode potential was applied. Biofilms grown under intermittent anode potential had more EPS and more proteins.
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Affiliation(s)
- João Pereira
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911MA, Leeuwarden, the Netherlands.,Environmental Technology, Wageningen University, Bornse Weilanden 9, P.O. Box 17, 6700, AA, Wageningen, the Netherlands
| | - Yuniki Mediayati
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911MA, Leeuwarden, the Netherlands.,Environmental Technology, Wageningen University, Bornse Weilanden 9, P.O. Box 17, 6700, AA, Wageningen, the Netherlands
| | - H Pieter J van Veelen
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911MA, Leeuwarden, the Netherlands
| | - Hardy Temmink
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911MA, Leeuwarden, the Netherlands.,Environmental Technology, Wageningen University, Bornse Weilanden 9, P.O. Box 17, 6700, AA, Wageningen, the Netherlands
| | - Tom Sleutels
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911MA, Leeuwarden, the Netherlands
| | - Bert Hamelers
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911MA, 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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