Effect of Surface Characteristics of Microorganisms in Anaerobic Sludge on Immobilization to Support Materials

Toshiyuki Nomura1, Takanori Nagao1, Akinori Yoshihara1, Shunsuke Nagamine III2, and Yasuhiro Konishi1. (1) Department of Chemical Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, 599-8531, Japan, (2) Department of Chemical Engineering, Kyoto University, Katsura Campus, Nishikyo-ku, Kyoto, 615-8510, Japan

It is necessary to retain the methanogens in the fermenter at the high concentration in order to realize the high-efficient methane fermentation process. In this study, the effect of electrostatic and hydrophobic properties of microorganisms existed in anaerobic sludge on the immobilization to support materials was examined experimentally. As a result, Methanosaeta concilii which is the most popular aceticlastic methanogen was non-charged and hydrophobic. Methanosarcina barkeri of a methyltrophic methanogen, and acidogens (proteolytic bacteria, amylolytic bacteria, llipolytic bacteria) cultivated selectively from the anaerobic sludge were charged negatively and hydrophobic. In addition, the immobilized microorganisms on support materials were incubated with sodium acetate. It was found that the methanogens were dramatically immobilized to bamboo charcoal in contract to hydrophilic alumina. And, it was also proven that Methanosaeta–like microorganism was immobilized to bamboo charcoal. These results of our experiments indicate that the hydrophobic and negative charged support material which can suppress the immobilization of the microorganisms except for Methanosaeta sp. is suitable for selective immobilization of Methanosaeta sp. which is the most important microorganism in the methane fermentation.