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Identifier

000364475

Title

Μαθηματική μοντελοποίηση ρυθμιστικών μηχανισμών ανάπτυξης των ευκαρυωτικών φωτοσυνθετικών μικροοργανισμών

Alternative Title

Mathematical modeling of regulatory mechanisms development of eukaryotic photosynthetic microorganisms

Author

Παπαδάκης, Ιωάννης Α

Thesis advisor

Λύκα, Κωνσταντίνα
Κοτσαμπάσης, Κυριάκος

Abstract

If we accept that scientific knowledge has contributed, through applications, to improve the quality of human life, the same scientific knowledge is required to help address the problems arising from the use of technology. Climate change, reduction of oceans pH, environmental pollution with toxic substances are just some of the problems posed by the use of technology. The holding capacity of photosynthetic organisms is already contributing to overcoming these problems and trying continuously to an even greater contribution. In this attempt, the mathematical modelling of the regulatory mechanisms of development of the photosynthetic organisms will be of use. Photosynthetic microorganisms that grow at a constant light intensity and constant concentration of carbon dioxide adjust their photosynthetic mechanism in these environmental growth conditions (Acclimation). The basic assumptions of the mathematical model developed in Chapter 2 are two: 1. Cells grown in high light intensity have a larger number of photosynthetic units compared with cells grown in low light, and 2. The cells that grow in an environment of high concentration of carbon dioxide have lower cost for carbon fixation compared with cells that grow in an environment of low concentration of carbon dioxide. The model is the first that manages to predict the experimentally observed intersection curves of photosynthesis - light in-tensity (PI-curves) for cells grown in conditions of high and low intensity. When environmental conditions change, the photosynthetic cells adapt their photosynthetic mechanism (adaptation) to the new growth conditions. The basic assumptions of the mathematical model developed in Chapter 3 are two: 1. The photosynthetic cells adjust their antenna size for the partition of the absorbed light energy in the linear electron flow (LEF), the cyclic electron flow (CEF) and water-water cycle (WWC), and other quenching mechanisms, and 2. The cells regulate the number of functional photosynthetic units serving each of these processes and also degrade the disabled photosynthetic units and construct new functional photosynthetic units. The allocation of the absorbed light energy is done by rules that take into account the relative availability of light and carbon dioxide. When the light intensity increases and/or the concentration of carbon dioxide reduced, decreasing the amount of energy allocated in LEF, while increasing the percentage goes to CEF and other quenching mechanisms. The inactivation of photosynthetic units caused by the energy allocated to the LEF and that cannot be used by the photosynthetic cell. The cell has mechanisms of degradation of photosynthetic units disabled and synthesis of new functional photosynthetic units. However, when the rate of deactivation is greater than the rate of repair a reduction in photosynthetic rate occurs, a phenomenon known as photoinhibition. The mathematical model is the first to quantify the management of absorbed energy and interface with the photoinhibition and provides for the first time, and in agreement with experimental data from different and independent literature sources that the rate of wasted energy is affected by changes in levels of carbon dioxide. By increasing the light intensity the rate of deactivation as well as the rate of oxygen production increases. After a critical value of the light intensity the oxygen production rate decreases revealing photoinhibition. The photosynthetic cell grows in a population. Chapters 4 and 5 show the population models that structured based on the individual model of regulation modulation (Chapter 3). The first population model developed in the water column and captures intraspecies competition for light and dissolved inorganic car-bon, the self shading and the photoadaptation of photosynthetic microorganisms. The model predicts correctly the distribution patterns of phytoplankton biomass and distribution patterns of chlorophyll in the water column and answers to the disagreement about whether we can use patterns of chlorophyll to predict patterns of biomass. It also provides that the increased concentration of inorganic carbon in sea water has no significant effect on the distribution of phytoplankton biomass in the water column. The second population model developed in a closed photobioreactor aiming to highlight the applications that have the population models that are constructed based on trustworthy individual mechanistic mathematical models. In this model we quantify the degradation of phenolic compounds from photosynthetic organisms, assuming that the biodegradation has increased demands for oxygen and high biochemical cost. The model predicts that in addition to the successful biodegradation there is a small but not insignificant gain in biomass. It also predicts that during biodegradation dominate almost anoxic conditions which as observed experimentally promote photosynthetic hydrogen production. The construction of a mathematical model that provides this production could be another application and this will be one of our future plans.

Language

Greek

Subject

Algae

DEB theory

Mathematical model

Photosynthesis

Photosynthetic unit

Phytoplankton

Population model

Μαθηματικό μοντέλο

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