BIOREACTOR DEVELOPMENT FOR MICROBIAL CARBON DIOXIDE FIXATION BY SPECIFICGAS ABSORPTION METHOD

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The research aimed to obtain fundamental informations for designing a bioreactor in which an autrotroph Alkaligenes eutrophus, which growed aerobically by utilizing carbon dioxide and hydrogen as carbon and energy sources respectively, was cultured for an efficient fixation of carbon dioxide. The optimum gaseous substrate for the microbe was a so called explosive gaseous mixture componets of hydrogen and oxygen together with carbon dioxide. In order to escape the operational substrate components from the explosive region of mixture componets, the oxygen partial pressure should be lowered in reference to securing the enzyme activity necessary for the growth. Finding out a countermeasure for recovering or even increasing the lowered growth rate due to the lowered oxygen partial pressure was the main subject of the research. For this end oxygen carriers, which enable to compensate the lowered oxygen transfer rate even under the lowered oxygen partical pressure, were searched and perfluorocarbon and some n-hydrocarbons were selected. By using thus selected oxygen carriers the optimum operational conditions were examined in a jar fermentor. The most important feature for securing the high oxygen transfer rate was found to operate the reactor under the condition that the medium was dispersed dropwise in a continuous phase of the oxygen- carrier. The condition was realized when the additional amount of the oxygen carrier was greater than about 65%. The efficiency for incrassing the oxygen transfer, which resulted in the corresponding increase in growth rate, was the higherst in case of perfluorocarbon use. However, the process economy prohibited its use, while the hydrocarbons such as n-heptadecane, n-hexadecane and n-dodecane would be promising candidates for the reactor application.