High current densities enable exoelectrogens to outcompete aerobic heterotrophs for substrate

Handle URI:
http://hdl.handle.net/10754/598464
Title:
High current densities enable exoelectrogens to outcompete aerobic heterotrophs for substrate
Authors:
Ren, Lijiao; Zhang, Xiaoyuan; He, Weihua; Logan, Bruce E.
Abstract:
© 2014 Wiley Periodicals, Inc. Chemical oxygen demand (COD) removal rates could be described by first-order kinetics with respect to COD concentration at different current densities, even under open circuit conditions with no current generation. The COD concentration was reduced more quickly with current generation due to the greater consumption of substrate by exoelectrogens, and less substrate was lost to aerobic heterotrophs. Higher current densities enabled exoelectrogens to outcompete aerobic heterotrophs for substrate, allowing for increased coulombic efficiencies with current densities. © 2014 Wiley Periodicals, Inc. In mixed-culture microbial fuel cells (MFCs), exoelectrogens and other microorganisms compete for substrate. It has previously been assumed that substrate losses to other terminal electron acceptors over a fed-batch cycle, such as dissolved oxygen, are constant. However, a constant rate of substrate loss would only explain small increases in coulombic efficiencies (CEs, the fraction of substrate recovered as electrical current) with shorter cycle times, but not the large increases in CE that are usually observed with higher current densities and reduced cycle times. To better understand changes in CEs, COD concentrations were measured over time in fed-batch, single-chamber, air-cathode MFCs at different current densities (external resistances). COD degradation rates were all found to be first-order with respect to COD concentration, even under open circuit conditions with no current generation (first-order rate constant of 0.14±0.01h-1). The rate of COD removal increased when there was current generation, with the highest rate constant (0.33±0.02h-1) obtained at the lowest external resistance (100Ω). Therefore, as the substrate concentration was reduced more quickly due to current generation, the rate of loss of substrate to non-exoelectrogens decreased due to this first-order substrate-concentration dependence. As a result, coulombic efficiencies rapidly increased due to decreased, and not constant, removal rates of substrate by non-exoelectrogens. These results show that higher current densities (lower resistances) redirect a greater percentage of substrate into current generation, enabling large increase in CEs with increased current densities. Biotechnol. Bioeng. 2014;111: 2163-2169.
Citation:
Ren L, Zhang X, He W, Logan BE (2014) High current densities enable exoelectrogens to outcompete aerobic heterotrophs for substrate. Biotechnology and Bioengineering 111: 2163–2169. Available: http://dx.doi.org/10.1002/bit.25290.
Publisher:
Wiley-Blackwell
Journal:
Biotechnology and Bioengineering
KAUST Grant Number:
KUS-I1-003-13
Issue Date:
5-Aug-2014
DOI:
10.1002/bit.25290
PubMed ID:
24889278
Type:
Article
ISSN:
0006-3592
Sponsors:
Contract grant sponsor: King Abdullah University of Science and Technology (KAUST)Contract grant number: KUS-I1-003-13
Appears in Collections:
Publications Acknowledging KAUST Support

Full metadata record

DC FieldValue Language
dc.contributor.authorRen, Lijiaoen
dc.contributor.authorZhang, Xiaoyuanen
dc.contributor.authorHe, Weihuaen
dc.contributor.authorLogan, Bruce E.en
dc.date.accessioned2016-02-25T13:21:10Zen
dc.date.available2016-02-25T13:21:10Zen
dc.date.issued2014-08-05en
dc.identifier.citationRen L, Zhang X, He W, Logan BE (2014) High current densities enable exoelectrogens to outcompete aerobic heterotrophs for substrate. Biotechnology and Bioengineering 111: 2163–2169. Available: http://dx.doi.org/10.1002/bit.25290.en
dc.identifier.issn0006-3592en
dc.identifier.pmid24889278en
dc.identifier.doi10.1002/bit.25290en
dc.identifier.urihttp://hdl.handle.net/10754/598464en
dc.description.abstract© 2014 Wiley Periodicals, Inc. Chemical oxygen demand (COD) removal rates could be described by first-order kinetics with respect to COD concentration at different current densities, even under open circuit conditions with no current generation. The COD concentration was reduced more quickly with current generation due to the greater consumption of substrate by exoelectrogens, and less substrate was lost to aerobic heterotrophs. Higher current densities enabled exoelectrogens to outcompete aerobic heterotrophs for substrate, allowing for increased coulombic efficiencies with current densities. © 2014 Wiley Periodicals, Inc. In mixed-culture microbial fuel cells (MFCs), exoelectrogens and other microorganisms compete for substrate. It has previously been assumed that substrate losses to other terminal electron acceptors over a fed-batch cycle, such as dissolved oxygen, are constant. However, a constant rate of substrate loss would only explain small increases in coulombic efficiencies (CEs, the fraction of substrate recovered as electrical current) with shorter cycle times, but not the large increases in CE that are usually observed with higher current densities and reduced cycle times. To better understand changes in CEs, COD concentrations were measured over time in fed-batch, single-chamber, air-cathode MFCs at different current densities (external resistances). COD degradation rates were all found to be first-order with respect to COD concentration, even under open circuit conditions with no current generation (first-order rate constant of 0.14±0.01h-1). The rate of COD removal increased when there was current generation, with the highest rate constant (0.33±0.02h-1) obtained at the lowest external resistance (100Ω). Therefore, as the substrate concentration was reduced more quickly due to current generation, the rate of loss of substrate to non-exoelectrogens decreased due to this first-order substrate-concentration dependence. As a result, coulombic efficiencies rapidly increased due to decreased, and not constant, removal rates of substrate by non-exoelectrogens. These results show that higher current densities (lower resistances) redirect a greater percentage of substrate into current generation, enabling large increase in CEs with increased current densities. Biotechnol. Bioeng. 2014;111: 2163-2169.en
dc.description.sponsorshipContract grant sponsor: King Abdullah University of Science and Technology (KAUST)Contract grant number: KUS-I1-003-13en
dc.publisherWiley-Blackwellen
dc.subjectCurrent densitiesen
dc.subjectExoelectrogensen
dc.subjectHeterotrophsen
dc.subjectMicrobial fuel cellen
dc.subjectSubstrate consumptionen
dc.titleHigh current densities enable exoelectrogens to outcompete aerobic heterotrophs for substrateen
dc.typeArticleen
dc.identifier.journalBiotechnology and Bioengineeringen
dc.contributor.institutionDepartment of Civil and Environmental Engineering; 212 Sackett Building, The Pennsylvania State University; University Park 16802 Pennsylvaniaen
dc.contributor.institutionState Key Laboratory of Urban Water Resource and Environment; Harbin Institute of Technology; Harbin P.R. Chinaen
kaust.grant.numberKUS-I1-003-13en

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