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Valero A, Petrash DA, Kuchenbuch A, Korth B. Enriching electroactive microorganisms from ferruginous lake waters - Mind the sulfate reducers! Bioelectrochemistry 2024; 157:108661. [PMID: 38340618 DOI: 10.1016/j.bioelechem.2024.108661] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 01/23/2024] [Accepted: 01/27/2024] [Indexed: 02/12/2024]
Abstract
Electroactive microorganisms are pivotal players in mineral transformation within redox interfaces characterized by pronounced oxygen and dissolved metal gradients. Yet, their systematic cultivation from such environments remains elusive. Here, we conducted an anodic enrichment using anoxic ferruginous waters from a post-mining lake as inoculum. Weak electrogenicity (j = ∼5 µA cm-2) depended on electroactive planktonic cells rather than anodic biofilms, with a preference for formate as electron donor. Addition of yeast extract decreased the lag phase but did not increase current densities. The enriched bacterial community varied depending on the substrate composition but mainly comprised of sulfate- and nitrate-reducing bacteria (e.g., Desulfatomaculum spp. and Stenotrophomonas spp.). A secondary enrichment strategy resulted in different bacterial communities composed of iron-reducing (e.g., Klebsiella spp.) and fermentative bacteria (e.g., Paeniclostridium spp.). Secondary electron microscopy and energy-dispersive X-ray spectroscopy results indicate the precipitation of sulfur- and iron-rich organomineral aggregates at the anode surface, presumably impeding current production. Our findings indicate that (i) anoxic waters containing geogenically derived metals can be used to enrich weak electricigens, and (ii) it is necessary to specifically inhibit sulfate reducers. Otherwise, sulfate reducers tend to dominate over EAM during cultivation, which can lead to anode passivation due to biomineralization.
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Affiliation(s)
- Astolfo Valero
- Institute of Soil Biology and Biogeochemistry, Biology Centre of the Czech Academy of Sciences, České Budějovice, Czech Republic; Department of Ecosystem Biology, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Daniel A Petrash
- Institute of Soil Biology and Biogeochemistry, Biology Centre of the Czech Academy of Sciences, České Budějovice, Czech Republic; Department of Environmental Geochemistry and Biogeochemistry, Czech Geological Survey, Prague, Czech Republic
| | - Anne Kuchenbuch
- Department of Microbial Biotechnology, Helmholtz Centre for Environmental Research GmbH - UFZ, Leipzig, Germany
| | - Benjamin Korth
- Department of Microbial Biotechnology, Helmholtz Centre for Environmental Research GmbH - UFZ, Leipzig, Germany.
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Khunnonkwao P, Thitiprasert S, Jaiaue P, Khumrangsee K, Cheirsilp B, Thongchul N. The outlooks and key challenges in renewable biomass feedstock utilization for value-added platform chemical via bioprocesses. Heliyon 2024; 10:e30830. [PMID: 38770303 PMCID: PMC11103475 DOI: 10.1016/j.heliyon.2024.e30830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Revised: 05/04/2024] [Accepted: 05/06/2024] [Indexed: 05/22/2024] Open
Abstract
The conversion of renewable biomass feedstock into value-added products via bioprocessing platforms has become attractive because of environmental and health concerns. Process performance and cost competitiveness are major factors in the bioprocess design to produce desirable products from biomass feedstock. Proper pretreatment allows delignification and hemicellulose removal from the liquid fraction, allowing cellulose to be readily hydrolyzed to monomeric sugars. Several industrial products are produced via sugar fermentation using either naturally isolated or genetically modified microbes. Microbial platforms play an important role in the synthesis of several products, including drop-in chemicals, as-in products, and novel compounds. The key elements in developing a fermentation platform are medium formulation, sterilization, and active cells for inoculation. Downstream bioproduct recovery may seem like a straightforward chemical process, but is more complex, wherein cost competitiveness versus recovery performance becomes a challenge. This review summarizes the prospects for utilizing renewable biomass for bioprocessing.
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Affiliation(s)
- Panwana Khunnonkwao
- Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, Phayathai Road, Wangmai, Pathumwan, Bangkok, 10330, Thailand
- Center of Excellence in Bioconversion and Bioseparation for Platform Chemical Production, Chulalongkorn University, Phayathai Road, Wangmai, Pathumwan, Bangkok, 10330, Thailand
| | - Sitanan Thitiprasert
- Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, Phayathai Road, Wangmai, Pathumwan, Bangkok, 10330, Thailand
- Center of Excellence in Bioconversion and Bioseparation for Platform Chemical Production, Chulalongkorn University, Phayathai Road, Wangmai, Pathumwan, Bangkok, 10330, Thailand
| | - Phetcharat Jaiaue
- Center of Excellence in Bioconversion and Bioseparation for Platform Chemical Production, Chulalongkorn University, Phayathai Road, Wangmai, Pathumwan, Bangkok, 10330, Thailand
- Program in Biotechnology, Faculty of Science, Chulalongkorn University, Phayathai Road, Wangmai, Pathumwan, Bangkok, 10330, Thailand
| | - Katsaya Khumrangsee
- Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, Phayathai Road, Wangmai, Pathumwan, Bangkok, 10330, Thailand
- Center of Excellence in Bioconversion and Bioseparation for Platform Chemical Production, Chulalongkorn University, Phayathai Road, Wangmai, Pathumwan, Bangkok, 10330, Thailand
| | - Benjamas Cheirsilp
- Center of Excellence in Innovative Biotechnology for Sustainable Utilization of Bioresources, Faculty of Agro-Industry, Prince of Songkla University, Hat Yai, Songkhla, 90110, Thailand
| | - Nuttha Thongchul
- Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, Phayathai Road, Wangmai, Pathumwan, Bangkok, 10330, Thailand
- Center of Excellence in Bioconversion and Bioseparation for Platform Chemical Production, Chulalongkorn University, Phayathai Road, Wangmai, Pathumwan, Bangkok, 10330, Thailand
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Yadav S, Sadhotra C, Patil SA. Retracted: The bidirectional extracellular electron transfer process aids iron cycling by Geoalkalibacter halelectricus in a highly saline-alkaline condition. Appl Environ Microbiol 2023:e0060923. [PMID: 37681980 DOI: 10.1128/aem.00609-23] [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: 04/12/2023] [Accepted: 07/16/2023] [Indexed: 09/09/2023] Open
Abstract
Bidirectional extracellular electron transfer (EET) is crucial to upholding microbial metabolism with insoluble electron acceptors or donors in anoxic environments. Investigating bidirectional EET-capable microorganisms is desired to understand the cell-cell and microbe-mineral interactions and their role in mineral cycling besides leveraging their energy generation and conversion, biosensing, and bio-battery applications. Here, we report on iron cycling by haloalkaliphilic Geoalkalibacter halelectricus via bidirectional EET under haloalkaline conditions. It efficiently reduces Fe3+ oxide (Fe2O3) to Fe0 at a 0.75 ± 0.08 mM/mgprotein/d rate linked to acetate oxidation via outward EET and oxidizes Fe0 to Fe3+ at a 0.24 ± 0.03 mM/mgprotein/d rate via inward EET to reduce fumarate. Bioelectrochemical cultivation confirmed its outward and inward EET capabilities. It produced 895 ± 23 µA/cm2 current by linking acetate oxidation to anode reduction via outward EET and reduced fumarate by drawing electrons from the cathode (‒2.5 ± 0.3 µA/cm2) via inward EET. The cyclic voltammograms of G. halelectricus biofilms revealed redox moieties with different formal potentials, suggesting the involvement of different membrane components in bidirectional EET. The cyclic voltammetry and GC-MS analysis of the cell-free spent medium revealed the lack of soluble redox mediators, suggesting direct electron transfer by G. halelecctricus in achieving bidirectional EET. By reporting on the first haloalkaliphilic bacterium capable of oxidizing and reducing insoluble Fe0 and Fe3+ oxide, respectively, this study advances the limited understanding of the metabolic capabilities of extremophiles to respire on insoluble electron acceptors or donors via bidirectional EET and invokes the possible role of G. halelectricus in iron cycling in barely studied haloalkaline environments. IMPORTANCE Bidirectional extracellular electron transfer (EET) appears to be a key microbial metabolic process in anoxic environments that are depleted in soluble electron donor and acceptor molecules. Though it is an ecologically important and applied microbial phenomenon, it has been reported with a few microorganisms, mostly from nonextreme environments. Moreover, direct electron transfer-based bidirectional EET is studied for very few microorganisms with electrodes in engineered systems and barely with the natural insoluble electron acceptor and donor molecules in anoxic conditions. This study advances the understanding of extremophilic microbial taxa capable of bidirectional EET and its role in barely investigated Fe cycling in highly saline-alkaline environments. It also offers research opportunities for understanding the membrane components involved in the bidirectional EET of G. halelectricus. The high rate of Fe3+ oxide reduction activity by G. halelectricus suggests its possible use as a biocatalyst in the anaerobic iron bioleaching process under neutral-alkaline pH conditions.
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Affiliation(s)
- Sukrampal Yadav
- Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali (IISER Mohali) , Knowledge City, Punjab, India
| | - Chetan Sadhotra
- Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali (IISER Mohali) , Knowledge City, Punjab, India
| | - Sunil A Patil
- Department of Earth and Environmental Sciences, Indian Institute of Science Education and Research Mohali (IISER Mohali) , Knowledge City, Punjab, India
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