High cell density and productivity cannot be achieved for freely suspended cell culture and fermentation system under chemostat conditions because of the auto-balance between growth of ceils within bioreactors and their continuous removal with effluent.Immobilized cells with various supporting materials were thus proposed in the 1970s and have been intensively studied since then.Unfortunately, most of those immobilized cell systems were unsuccessful, technically and economically as well, particularly for the production of primary me tabolites.