In an effort to use a biocatalyst repeatedly with acceptable stability, amylosucrase from Neisseria polysaccharea (NpAS) was non-covalently immobilized on a pH-dependent autoprecipitating polymer, Eudragit L100. About 87% of the enzyme activity and 96% of the protein were recovered after the immobilization process. The immobilized NpAS showed significantly improved thermostability, whereas no difference was observed in the temperature and pH profiles of activity between the native and immobilized NpAS. To evaluate the reusability of the immobilized NpAS, repeated production of linear alpha-(1,4)-glucans was carried out at 35 degrees C with 0.1 M sucrose as substrate. Although only 71-74% of the protein was recovered after each reaction cycle, high stability index was observed from 0.93 to 0.96. Reusability of the immobilized NpAS was further confirmed by comparing its linear alpha-(1,4)-glucan products with that produced by native one. Almost identical production yield and molecular size distribution of the linear alpha-(1,4)-glucans were obtained between them. (C) 2011 Elsevier Ltd. All rights reserved.