Dynamics of cathode-associated microbial communities and metabolite profiles in a glycerol-fed bioelectrochemical system

Dennis, Paul G., Harnisch, Falk, Yeoh, Yun Kit, Tyson, Gene W. and Rabaey, Korneel (2013) Dynamics of cathode-associated microbial communities and metabolite profiles in a glycerol-fed bioelectrochemical system. Applied and Environmental Microbiology, 79 13: 4008-4014. doi:10.1128/AEM.00569-13

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Author Dennis, Paul G.
Harnisch, Falk
Yeoh, Yun Kit
Tyson, Gene W.
Rabaey, Korneel
Title Dynamics of cathode-associated microbial communities and metabolite profiles in a glycerol-fed bioelectrochemical system
Journal name Applied and Environmental Microbiology   Check publisher's open access policy
ISSN 0099-2240
1098-5336
Publication date 2013-07-01
Year available 2013
Sub-type Article (original research)
DOI 10.1128/AEM.00569-13
Open Access Status File (Publisher version)
Volume 79
Issue 13
Start page 4008
End page 4014
Total pages 7
Place of publication United States
Publisher American Society for Microbiology
Language eng
Abstract Electrical current can be used to supply reducing power to microbial metabolism. This phenomenon is typically studied in pure cultures with added redox mediators to transfer charge. Here, we investigate the development of a current-fed mixed microbial community fermenting glycerol at the cathode of a bioelectrochemical system in the absence of added mediators and identify correlations between microbial diversity and the respective product outcomes. Within 1 week of inoculation, a Citrobacter population represented 95 to 99% of the community and the metabolite profiles were dominated by 1,3-propanediol and ethanol. Over time, the Citrobacter population decreased in abundance while that of a Pectinatus population and the formation of propionate increased. After 6 weeks, several Clostridium populations and the production of valerate increased, which suggests that chain elongation was being performed. Current supply was stopped after 9 weeks and was associated with a decrease in glycerol degradation and alcohol formation. This decrease was reversed by resuming current supply; however, when hydrogen gas was bubbled through the reactor during open-circuit operation (open-circuit potential) as an alternative source of reducing power, glycerol degradation and metabolite production were unaffected. Cyclic voltammetry revealed that the community appeared to catalyze the hydrogen evolution reaction, leading to a +400-mV shift in its onset potential. Our results clearly demonstrate that current supply can alter fermentation profiles; however, further work is needed to determine the mechanisms behind this effect. In addition, operational conditions must be refined to gain greater control over community composition and metabolic outcomes.
Formatted abstract
Electrical current can be used to supply reducing power to microbial metabolism. This phenomenon is typically studied in pure cultures with added redox mediators to transfer charge. Here, we investigate the development of a current-fed mixed microbial community fermenting glycerol at the cathode of a bioelectrochemical system in the absence of added mediators and identify correlations between microbial diversity and the respective product outcomes. Within 1 week of inoculation, a Citrobacter population represented 95 to 99% of the community and the metabolite profiles were dominated by 1,3-propanediol and ethanol. Over time, the Citrobacter population decreased in abundance while that of a Pectinatus population and the formation of propionate increased. After 6 weeks, several Clostridium populations and the production of valerate increased, which suggests that chain elongation was being performed. Current supply was stopped after 9 weeks and was associated with a decrease in glycerol degradation and alcohol formation. This decrease was reversed by resuming current supply; however, when hydrogen gas was bubbled through the reactor during open-circuit operation (open-circuit potential) as an alternative source of reducing power, glycerol degradation and metabolite production were unaffected. Cyclic voltammetry revealed that the community appeared to catalyze the hydrogen evolution reaction, leading to a +400-mV shift in its onset potential. Our results clearly demonstrate that current supply can alter fermentation profiles; however, further work is needed to determine the mechanisms behind this effect. In addition, operational conditions must be refined to gain greater control over community composition and metabolic outcomes.
Keyword Extracellular electron-transfer
1,3-Propanediol
Fermentation
Electrosynthesis
Klebsiella
Q-Index Code C1
Q-Index Status Confirmed Code
Grant ID ARC DP0879245
Institutional Status UQ
Additional Notes Supplemental material (read only) - http://aem.asm.org/content/79/13/4008/suppl/DCSupplemental

 
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Created: Fri, 12 Jul 2013, 23:50:05 EST by Mrs Louise Nimwegen on behalf of Advanced Water Management Centre