Microbial community structure in a biofilm anode fed with a fermentable substrate: The significance of hydrogen scavengers
Article first published online: 17 AUG 2009
Copyright © 2009 Wiley Periodicals, Inc.
Biotechnology and Bioengineering
Volume 105, Issue 1, pages 69–78, 1 January 2010
How to Cite
Parameswaran, P., Zhang, H., Torres, C. I., Rittmann, B. E. and Krajmalnik-Brown, R. (2010), Microbial community structure in a biofilm anode fed with a fermentable substrate: The significance of hydrogen scavengers. Biotechnol. Bioeng., 105: 69–78. doi: 10.1002/bit.22508
- Issue published online: 19 NOV 2009
- Article first published online: 17 AUG 2009
- Accepted manuscript online: 17 AUG 2009 12:00AM EST
- Manuscript Accepted: 12 AUG 2009
- Manuscript Revised: 9 AUG 2009
- Manuscript Received: 12 JUN 2009
- anode respiring bacteria;
- microbial electrolysis cells
We compared the microbial community structures that developed in the biofilm anode of two microbial electrolysis cells fed with ethanol, a fermentable substrate—one where methanogenesis was allowed and another in which it was completely inhibited with 2-bromoethane sulfonate. We observed a three-way syntrophy among ethanol fermenters, acetate-oxidizing anode-respiring bacteria (ARB), and a H2 scavenger. When methanogenesis was allowed, H2-oxidizing methanogens were the H2 scavengers, but when methanogenesis was inhibited, homo-acetogens became a channel for electron flow from H2 to current through acetate. We established the presence of homo-acetogens by two independent molecular techniques: 16S rRNA gene based pyrosequencing and a clone library from a highly conserved region in the functional gene encoding formyltetrahydrofolate synthetase in homo-acetogens. Both methods documented the presence of the homo-acetogenic genus, Acetobacterium, only with methanogenic inhibition. Pyrosequencing also showed a predominance of ethanol-fermenting bacteria, primarily represented by the genus Pelobacter. The next most abundant group was a diverse community of ARB, and they were followed by H2-scavenging syntrophic partners that were either H2-oxidizing methanogens or homo-acetogens when methanogenesis was suppressed. Thus, the community structure in the biofilm anode and suspension reflected the electron-flow distribution and H2-scavenging mechanism. Biotechnol. Bioeng. 2010;105: 69–78. © 2009 Wiley Periodicals, Inc.