Development of intelligent anaerobic fermentation process for reuse of carbon dioxide

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A strict anaerobic acetogen, Acetobacterium sp. can utilize CO_2 as a co-substrate with methanol and accumulates high amount of vitamin B1 in the cells. Therefore, it is possible theoretically to produce acetate which is useful as chemical raw material or methane from the acetate which is. useful as fuel gas together with vitamin B_1_2.The results obtained in this work were as follows :1. In chemostat continuous culture on CO_2/methanol, Acetobacterium sp. had really high vitamin B_1_2 content in the cells (5 mg/g cell) and produced acetate almost stoichiometrically from CO_2/methanol, that is, the molar ratio of consumption of methanol and CO_2 was 2 and 1. And specific production rates of vitamin B_1_2 and acetate were increased linearly with increase of dilution rate. Based on this fact, to increase the production rates of acetate and vitamin Bin, a fixed bed bioreactor packed with ceramic material was operated at a high dilution rate than growth rate resulting high production rates of acetate and intracellular vitamin B_1_2.2. A nobel coculture of Acetobacterium with a metanogen, Methanosaeta concilii was developed to convert acetate to OH.First, a flxed bed reactor of M.concilii was set up, where polypropyrene/ceramic mixture was packed to adhere the cells. Then, this reactor was connected to a chemostat culture of Acetobacterium since the growth rate of the methanogen was 10 times lower than Acetobacterium.By using this combined reactor process where the methanogen cells consumed acetate produced by Acetobacterium, acetate in the chemostat culture was almost completely converted to methane and vitamin B_1_2 productivity increased up to 170 mg/lid at a high dilutions rate of 0.15 h^-^1, which is ca. 2 times higher than the maximum growth rate of Acetobacterium in batch culture.