E-Locus - Institutional Repository of the University of Crete

Home Search

Results - Details

Search command : Author="Κοτζαμπάσης" And Author="Κυριάκος"

Current Record: 21 of 70

[Add to Basket]

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

Photosynthesis

Respiration

Αναπνοή

Μικροφύκη

Φωτοσύνθεση

Issue date

2019-11-29