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Identifier

000463260

Title

Μελέτη της παραγωγής βιο-υδρογόνου από αζωτοδεσμευτικά βακτήρια

Alternative Title

Study of biohydrogen production by nitrogen fixing bacteria

Author

Μανουσάκη, Μαρία Σ.

Thesis advisor

Γανωτάκης, Δημήτριος

Reviewer

Παυλίδης, Ιωάννης
Χανιωτάκης, Νικόλαος

Abstract

In the present master's thesis, the morphology, as well as a series of cultivation conditions influencing the metabolism, nitrogen fixation, and hydrogen production by a bacterial strain of the genus Clostridium were studied. Initially, the morphology of the bacterium was studied using optical and electron microscopy techniques. Subsequently, the effect of various carbon sources, inorganic components, and the presence of different gases on the organism's metabolism was investigated. Specifically, organic substrates, including monosaccharides, disaccharides, organic acids, and glycerol were used. Additionally, gases such as N₂, He, O₂, and CO₂ in the growth environment, as well as the presence of various metallic ions and salts in the nutrient medium, such as Fe²⁺, Mg²⁺ , and CaCO₃, were examined. Gas chromatography was employed for the quantitative determination of produced hydrogen and fixed nitrogen, while ¹H NMR was used for the identification and quantification of metabolic by-products. Our results indicated that this Clostridium strain is an anaerobic rod-shaped bacterium, measuring 4-5 μm in length and approximately 0.5 μm in thickness. It was also found that the microorganism possesses the nitrogenase enzyme and has the ability to fix molecular nitrogen, concurrently producing hydrogen. Moreover, it has the metabolic tools to produce bio- hydrogen through dark fermentation. Experiments showed that the bacterium also contains the hydrogenase enzyme. Among the studied conditions, the highest hydrogen production was observed with mannitol, sucrose, and pyruvate at 1271, 1003, and 1059 mL H₂ L^-1 of culture, respectively. Extremely high hydrogen production was recorded in the condition with sucrose and ammonium in the medium and CO₂ in the gas environment during growth, with 1966 mL H₂ L^-1 of cultivation. It was also found that the final products of metabolism, regardless of the condition, are primarily butyric and acetic acids in various proportions. In the case of glycerol as the carbon source, the bacterium possesses the metabolic tools to produce 1,3-propanediol in addition to butyric and acetic acids. The results of this thesis demonstrated that through the rational design of bacterial cultivation conditions, it is possible to achieve the production of high amounts of biofuels and valuable organic molecules through the metabolic processes of the bacterium.

Language

Greek

Subject

1,3-propanediol

1,3-προπανοδιόλη

Bio-hydrogen

Clostridium sp.

Dark fermentation

Hydrogen

Nitrogen fixation

Sugar metabolism

Αζωτοδεσμευτικά βακτήρια