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Identifier

000450017

Title

Μελέτη της παραγωγής υδρογόνου, εξωπολυσακχαριτών και πολυυδροξυαλκανοϊκών από φωτοσυνθετικά βακτήρια

Alternative Title

A study of production of hydrogen, polyhydroxyalkanoates and exopolysaccharides in photosynthetic bacteria

Author

Χατζηθανασίου, Αγγελική Α.

Thesis advisor

Γανωτάκης, Δημήτριος

Reviewer

Παυλίδης, Ιωάννης
Τσιώτης, Γεώργιος

Abstract

In the present work the effect of growth conditions on the production of a series of natural products by two photosynthetic bacteria; Nostoc calcicola and Rhodopsedomonas sp. was investigated. This study was divided into two parts: in the first one, the ability of the filamentous cyanobacterium Nostoc calcicole to produce exopolysaccharides (EPS) and hydrogen gas was studied under oxygenic and anoxygenic conditions. The effect of various carbon sources, such as glucose, acetate, carbon dioxide, and sodium carbonate, as well as the deficiency of nitrogen from the growth medium, were also investigated. Results showed that hydrogen production could be achieved almost exclusively under anoxygenic conditions, while EPS production is favored in the presence of atmospheric oxygen. Additionally, an increase in the production of both products was reported in the presence of carbon dioxide as a carbon source and nitrogen deprivation from the growth medium. This section focused on the production of biopolymers by the same bacterium, under continuous air supply and sulfur deficiency. The bio-products were examined by electron microscopy techniques. Furthermore, the production of the EPS by semi-continuous cultures was studied. Nostoc calcicola was able to produce a variety of valuable polymers, such as poly-β-hydroxybutyrates (PHB) as well as cyanophycin. Moreover, EPS accumulation could be improved significantly in semi-continuous cultures. In the second part, a Purple Non-Sulfur Bacterium of the Rhodopseudomonas genus was used. Initially, the anaerobic production of PHB was assessed by using hydrolyzed Chlorella sp. biomass as a growth medium. Experiments were performed under stress conditions for the cells, which included nitrogen and sulfur deprivation from the growth medium, in order to increase PHB’s production. Finally, the growth of the PNSB was investigated in the presence of a digested organic mixture, which is a combination of fresh-shredded garden and yard waste. The study focused on the production of PHB, using the ideal concentration of the waste material in the growth medium. An 8%v/v solution of the digested mixture was found to have an increasing effect on both culture’s growth and ability to produce PHB.

Language

Greek

Subject

Chlorella sp

Cyanobacteria

Exopolysaccharides (EPS)

Hydrogen

Nostoc calcicola

Photosynthetic microorganisms

Poly-β-hydroxybutyrates (PHB)

Purple non-aulfur bacteria (PNSB)

Rhodopseudomonas sp.