The polysaccharide O-carboxymethyl poly-beta-cyclodextrin(M= 1.3 x 10(4), 40% COOH groups) was employed as modification agent for Bacillus badius phenylalanine dehydrogenase via a carbodiimide-catalyzed reaction. The neoglycoenzyme retained 63% of its initial activity and contained about 2.5 mol of polymer per mole of enzyme. The optimum temperature for the enzyme was increased by 15 degrees C and its thermostability was improved by about 6 degrees C over 10 min incubation. The conjugate was also more resistant to thermal inactivation at different temperatures, ranging from 45 to 60 degrees C. The improved conformational stability of the modified enzyme was confirmed by fluorescence spectroscopy. (c) 2006 Elsevier Inc. All rights reserved.