Much research was performed in order to find alternative energy sources. In the new concept presented in this thesis, methane was produced by a microbial consortium which is fed only by glycolate excreted by photosynthetic algae. It was unknown how the biogas production and the process stability are influenced by certain parameter shifts in glycolate feed, pH of the feed, oxygen
input and temperature. Therefore, different parameter changes were applied to the reactor system. Gas formation and composition, pH, FosTac and organic acid content in the media were analyzed. Additionally, the community composition induced by the changes of the process parameters was analyzed. Therefore, the single cell level using flow cytometry and the genetic level using T-RFLP were observed. The R based tool flowCyBar was applied to follow community dynamics and to find key players in the process. Abiotic and biotic
parameters were used for correlation analysis (Spearman´s Rho) to determine specific functions of sub-communities and the T-RFs found in the whole community.
The cultivation at room temperature indicated that the biogas yield was 30 % lower in comparison to the cultivation at 37°C. The community seemed to be able to sustain pulsating oxygen input in case glycolate as substrate is available. Additionally, the system was able to recover after the oxygen application of one day. A linear correlation between the feed glycolate and the biogas production was observed (R^2 = 0.97). High biogas yields were obtained
(up to 90 %) indicating that glycolate is a suitable substrate. The efficiency of the process was high with 41 ± 3 % methane in the biogas under defined conditions. It could be observed that biogas can be produced on glycolate as mono-substrate by a complex microbial community while it remained complex over the complete study (505 days cultivation) although glycolate was used as sole carbon source. Key sub-communities (e.g. cluster 1 and 3) and T-RFs (e.g. T-RF representing Planctomycetaceae or 67 bp) were defined and indicated the status of the bioreactor. The community was able to sustain certain parameter shifts, like changes in the pH of the feed (from 3 to 7), while others led to a complete crash of the system, like high glycolate feeds (3.6 g d^-1 L^-1). All in all, the stability of the process seemed to be susceptible on external influences.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:13387 |
| Date | 12 June 2015 |
| Creators | Reinert, Susann |
| Contributors | Wilhelm, Christian, Posten, Clemens, Universität Leipzig |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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