BIOREACTOR DEVELOPMENT FOR MICROBIAL CARBON DIOXIDE FIXATION BY SPECIFICGAS ABSORPTION METHOD

本研究旨在为设计一种生物反应器提供基础信息，在该生物反应器中培养一种自养细菌，该细菌分别利用二氧化碳和氢气作为碳源和能源进行好氧生长，从而有效地固定二氧化碳。该微生物的最佳气体底物是所谓的爆炸性气体混合物，即氢、氧和二氧化碳的混合物。为了使操作底物组分脱离混合物组分的爆炸区，应降低氧分压，以确保生长所需的酶活性。寻找恢复甚至提高由于氧分压降低而导致的增长率下降的对策是本研究的主要主题。为此，寻找了即使在较低的氧分压下也能补偿降低的氧转移速率的氧载体，并选择了全氟碳和一些正构烷烃。利用所选择的氧气载体，在罐式发酵罐中考察了最佳操作条件。确保高氧传递率的最重要的特征是在介质在氧气载体的连续相中滴状分散的条件下操作反应器。当氧载体的加入量大于约65%时，该条件即可实现。在使用全氟化碳的情况下，增加氧转移的效率最高，从而导致生长速度的相应增加。然而，工艺经济限制了它的使用，而碳氢化合物，如正十七烷、正十六烷和正十二烷，将是反应堆应用的有希望的候选者。

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.