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Identifier 000397251
Title Hydrogen production by lichens
Alternative Title Παραγωγή υδρογόνου από λειχήνες
Author Καστανάκη, Ελισάβετ Ν.
Thesis advisor Κοτζαμπάσης, Κυριάκος
Reviewer Πυρίντσος, Στέργιος
Τσαγρή, Ευθυμία
Abstract This master’s thesis project examines the capability and the optimization of hydrogen (H2) production by lichens in a closed system. Lichens are symbionts formed by different species of fungi (mycobiont) and a photosynthesizing partner (photobiont) usually green algae or in some cases cyanobacteria. As the mycobiont provides protection from the external environment and accumulates water resources the photobiont provides chemical energy by means of photosynthesis. The photosynthetic H2 production occurs in the green algae when they are under anoxic conditions, anoxic conditions (in a closed system) are primarily established via the respiratory O2 consumption from the fungus but also from algae. A range of parameters affecting photosynthesis and respiration were experimentally tested in an attempt to identify the best experimental conditions for hydrogen production by the lichen Pleurosticta acetabulum in a closed system. These were; the concentration of glucose as an exogenously supplied carbon source, the incubation medium volume, the composition of the incubation medium, temperature and light intensity. Hydrogen production (in photobiont) and oxygen consumption (in photobiont and mycobiont) were quantified using Gas Chromatography (GC-TCD). A series of important photosynthetic, respiratory and hydrogen production proteins (PSaA, D1, COX, AOX, PTOX, PFOR and HYDA) were analyzed for their expression using western blots in order to identify and confirm the specific hydrogen production pathways under the optimal hydrogen production experimental conditions identified. The results demonstrated that lichens are able to establish anoxic conditions in a closed system mainly through O2 consumption by the mycobiont while producing high yields of hydrogen by the photobiont utilizing three different pathways (PSII-dependent, PSII-independent and dark fermentation pathways). Under light conditions, they successfully use mainly the PSII-dependent and the PSII-independent pathways to transfer electrons to hydrogenase, while under dark conditions, lichens use the PFOR enzyme and the dark fermentative pathway to supply electrons to hydrogenase. Following the experimental testing of the lichen Pleurosticta acetabulum, the optimum conditions were utilized in the examination and analysis of Η2 production in a number of other lichen species which confirmed the general capability of lichens to produce large quantities of H2 in a closed system. These benefits in conjunction with lichens' ability to survive in extreme environments constitute them as invaluable hydrogen producers, with great potential in future hydrogen production applications. A large part of the results presented in this master thesis were published in PLOS ONE [Papazi A, Kastanaki E, Pirintsos S, Kotzabasis K (2015) Lichen Symbiosis: Nature's High Yielding Machines for Induced Hydrogen Production. PLoS ONE 10(3): e0121325. doi:10.1371/journal.pone.0121325].
Language English
Subject Symbiosis
Issue date 2015-11-20
Collection   School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
  Type of Work--Post-graduate theses
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