One-step purification of glucoamylase by affinity precipitation with alginate

It was found that alginate binds to glucoamylase, presumably through the re cognition of starch binding domain of the latter. The present work exploits this for purification of glucoamylases from commercial preparation of Aspe rgillus niger and crude culture filtrate of Bacillus amyloliquefaciens by a ffinity precipitation technique in a single-step protocol. Glucoamylase is selectively precipitated using alginate as macroaffinity ligand and later e luted with 1.0 m maltose. In the case of A. niger, 81 % activity is recover ed with 28-fold purification. The purified glucoamylase gave a single band on SDS-PAGE corresponding to 78 kDa molecular weight. The developed affinit y precipitation process also works efficiently for purification of Bacillus amyloliquefaciens glucoamylase from its crude culture filtrate, giving 78% recovery with 38-fold purification. The purified preparation showed a majo r band corresponding to 62 kDa and a faint band about 50 kDa on SDS-PAGE. T he latter corresponds to the molecular weight for a-amylase of Bacillus amy loliquefaciens. Copyright (C) 2001 John Wiley & Sons, Ltd.