BIOREACTOR DEVELOPMENT FOR MICROBIAL CARBON DIOXIDE FIXATION BY SPECIFICGAS ABSORPTION METHOD

本研究的目的是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株分别以二氧化碳和氢气为碳源和能源的自养真养产碱菌，以实现高效固定二氧化碳。该菌的最适气体基质是由氢气、氧气和二氧化碳组成的爆炸性气体混合物。为了从混合物组分的爆炸区域逸出操作底物组分，应降低氧分压以确保生长所需的酶活性。研究的主要课题是找到恢复甚至提高由于氧分压降低而降低的生长速率的对策。为此目的，寻找即使在降低的氧分压下也能够补偿降低的氧传递速率的氧载体，并选择了全氟化碳和一些正构烃。通过使用这样选择的氧载体，在罐式发酵罐中考察了最佳操作条件。发现确保高氧转移速率的最重要特征是在介质逐滴分散在氧载体的连续相中的条件下操作反应器。当氧载体的添加量大于约65%时，实现该条件。在使用全氟化碳的情况下，增加氧传递的效率最高，这导致了相应的生长速率的增加。然而，工艺经济性禁止其使用，而碳氢化合物，如正十七烷，正十六烷和正十二烷将是有希望的候选人的反应器应用。

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.