Initial Adhesion of Methanosarcina Barkeri to Support Materials

Akinori Yoshihara, Toshiyuki Nomura, Shunsuke Nagamine, and Yasuhiro Konishi. Department of Chemical Engineering, Osaka Prefecture University, 1-1 Gakuencho, Naka-ku, Osaka, 599-8531, Japan

The methane fermentation process has been used for recovering the energy from organic waste with much water. Methanogenic sludge consists of a densely packed structure of anaerobic microorganisms. Anaerobic digestion of complex organic matter to methane consists of a cascade of biochemical conversions catalysed by different physiological groups of interacting microorganisms. Conventional mixed digestion systems contain a mixture of microorganisms which can catalyse all phases of the cascade. The reaction rates normally obtained in different phases are markedly different with the overall process becomes rate restricted by the slowest phase. Immobilization of the methanogens to support material was noticed as a method for retaining the methanogens at the high concentration in the reactor. Adhesion properties of microorganisms play an important role in the immobilization. Adhesion is strongly dependent on the surface characteristics of microorganisms. Surface electricity and hydrophobicity of microorganisms may be taken as an indicator for the adhesion properties. In this study, the effect of electrostatic and hydrophobic properties of Methanosarcina barkeri on the immobilization to support material was examined experimentally. Methanosarcina barkeri of the pure culture was used for the experiment. As a result, it was found that M. barkeri was a hydrophobic and negatively-charged cell. And, M. barkeri adhered well to the anion exchange resin than the hydrophobic resin. The activity of the cell adhered to the hydrophobic resin increased further than that of dispersed cell.