A long journey from bioanode to biocathode
The goal of this thesis was to understand the effect of three different dynamic conditions and disturbances that bioanodes and biocathodes may encounter namely storage, starvation, and potential change. Storage and starvation are disturbances that can affect biological electrodes in all kinds of systems, and it is important to understand their consequences for performance. Changing electrode potential has been shown as a promising method for start-up of biocathodes from enriched bioanodes, but little is known about the long-term performance and changes in microbial community composition as the biocathode develops.
First, the possibility for storage of acetate-oxidizing bioanodes using refrigeration, glycerol freezing, and acetone dehydration was investigated. It was shown that storage of acetate-oxidizing bioanodes was possible. Bioanodes stored using refrigeration were the only electrodes that showed biological activity right after five weeks of storage. Then, starvation of acetate-and glucose-fed bioanodes was investigated. It was shown that the acetate- and glucose-fed bioanodes can survive 10 days starvation. However, the overall performance of the glucose-fed bioanodes deteriorated more after each starvation phase compared to the acetate-fed bioanodes. The conversion of acetate- and glucose-fed bioanodes to biocathodes was also compared. Immediately after the potential change, the glucose-fed bioanodes showed better cathodic activity but over time the performance converged. Then, we compared the conversion of bioanodes to biocathodes with direct start-up of biocathodes from a wastewater inoculum. Bare electrodes started-up faster compared to pre-enriched bioanodes. In the end, both types of enrichment procedures led to very similar biocathode communities, which were completely different from the bioanode communities. Indeed, for the microbial communities, it was a long journey from bioanode to biocathodes. Hydrogen appeared to be an important intermediate in the biocathode biofilms, therefore, start-up of biocathodes with pre-enriched hydrogenotrophic cultures was investigated. Hydrogenotrophic microorganisms could facilitate start-up of the biocathodes. All the microbial electrolysis cells inoculated by the enrichment cultures started to generate noticeable current directly after inoculation.
In summary, the bioelectrodes in our experiments were robust and could handle storage and starvation periods although the results depended on the experimental conditions, the feed, and the microbial communities. Conversion of bioanodes into biocathodes was less successful and resulted in a complete transition of the microbial community on the electrode. Start-up of biocathodes with hydrogen-oxidizing enrichment cultures was a more successful strategy.
Microbial electrolysis cell
Microbial fuel cell
Mixed microbial communities
Soroush Saheb Alam
Chalmers, Arkitektur och samhällsbyggnadsteknik, Vatten Miljö Teknik
Effect of start-up strategies and electrode materials on carbon dioxide reduction on biocathodes
Applied and Environmental Microbiology,; Vol. 84(2018)
Artikel i vetenskaplig tidskrift
Effects of storage on mixed-culture biological electrodes
Scientific Reports,; Vol. 5(2015)p. no. 18433-
Artikel i vetenskaplig tidskrift
SAHEB-ALAM, S., PERSSON, F., WILEN, B. M., HERMANSSON, M. & MODIN, O. Biodiversity, community composition and response to dynamic conditions of microbial electrodes enriched on acetate and glucose.
SAHEB-ALAM, S., PERSSON, F., WILEN, B. M., HERMANSSON, M. & MODIN, O. A variety of hydrogenotrophic enrichment cultures catalyse cathodic reactions.
Biokatalys och enzymteknik
Livsvetenskaper och teknik (2010-2018)
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4437
SB-H6, Sven Hultins gara 6, Göteborg
Opponent: Dr. Deepak Pant, Flemish Institute for Technological Science (VITO), Belgium