In addition to its use to make beads for enzyme immobiliza-tion, chitosan is used for flocculating microorganisms [21,22]. Rehnet al. [23] reported chitosan flocculation for immobilization ofwhole-cells without cross-linking. Chitosan flocculation is optimalat slightly basic conditions, such flocculated cells are not suitable forreactions in acidic conditions. The reported method to collect floc-culated cells by sediment is also very difficult to control in industrialscale. Such collected immobilized cells contain too much water,which makes them difficult to store and transport.