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Identifier 000426493
Title Μελέτη της φωτοσυνθετικά ελεγχόμενης διαφοροποίησης του pH του περιβάλλοντος των μικροφυκών
Alternative Title Study of the photosynthetic controlled pH differentiation of the microalgae environment
Author Μέντε, Μελπομένη-Σοφία Δ.
Thesis advisor Κοτζαμπάσης, Κυριάκος
Reviewer Σαρρής, Παναγιώτης
Πυρίντσος, Στέργιος
Abstract Photosynthesis is a biological process that converts solar energy into exploitable chemical energy, which is invested in converting inorganic matter into organic. In this paper we investigate how the photosynthetic process is affected and affects the proton environment of the plant cell and how we can use these effects in various future biotechnological applications. Thus, with the unicellular green alga Scenedesmus obliquus, we measured combined the variations in environmental pH, cell volume (μl PCV/ml), photosynthetic efficiency (Fv / Fm), and a number of other factors related to molecular structure and function of the photosynthetic apparatus. Experiments were performed at different intensities of light and in the dark, at different nutrient concentrations, at different cell concentrations, in open and closed cultures. In the present work we showed that in acidic environments the photosynthesis and growth of microalgae increased in relation to the corresponding alkaline one, especially when the environment was saturated with nutrients and photons. Correspondingly, during photosynthesis in all experimental treatments the pH increased, which indicates proton uptake. This variation of pH in the existing literature has most often been related to the uptake and removal of CO2, although in green algae (and not only) have identified a series of H+-channels, and some of them are photoregulated. When keep the CO2 flow in open cultures constant, we saw a clear and sharp increase in pH during photosynthesis while in the dark, in the absence of photosynthesis, the pH remained constant. Taking these facts into consideration we can conclude that: Photosynthesis of microalgae requires the absorption of protons resulting in a pH increase in aquatic environment. The photosynthetic controlled pH increase in microalgal culture medium is the result of cellular proton pumping (H+) rather than a decrease in the CO2 concentration in the culture medium. The proton uptake during photosynthesis is proportional to cell concentration and light intensity. The high concentration of protons (low pH) in the aquatic environment, when light and inorganic nutrients are not the limiting factor, strongly induces the photosynthetic process and consequently the growth of the culture expressed as a packed cell volume. The mitochondrial respiratory process, in the absence of photosynthetic activity, does not substantially differentiate the culture pH, but when intensified by exogenous supplied glucose significantly reduces the pH of the culture. The decrease in pH induced by the respiratory process is a result of CO2 . All of the above allow us to be optimistic that in the near future we will be able to exploit this knowledge of the interaction of microalgae with their protonated environment in order to understand and deal better with major environmental problems, such as ocean acidification and eutrophication.
Language Greek
Subject Microalgae
Model selection
Issue date 2019-11-29
Collection   School/Department--School of Sciences and Engineering--Department of Biology--Post-graduate theses
  Type of Work--Post-graduate theses
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