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.
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