Preparation and some properties of immobilized Penicillium funiculosum 258dextranase

The production of dextranase was investigated in static cultures of Penicil lium funiculosum 258. Maximal enzyme productivity was attained at pH 8.0, w ith 3.5% (w/v) dextran (MW, 260 000) as carbon source, NaNO3 (1%, w/v) and yeast extract (0.2%, w/v) as nitrogen source, 0.4% (w/v) K2HPO4 and 0.06% ( w/v) MgSO4. It was possible to increase the productivity of dextranase to 4 1.8 units ml(-1) in the modified medium. The enzyme was immobilized on diff erent carriers by different techniques of immobilization. The enzyme prepar ed by covalent binding on chitosan using glutaraldehyde had the highest act ivity, the immobilized enzyme retaining 63% of its original specific activi ty. Compared with the free dextranase, the immobilized enzyme exhibited: a higher pH optimum, a higher optimal reaction temperature and energy of acti vation, a higher Michaelis constant, improved thermal stability and higher values of deactivation rate constant. The immobilized enzyme retained about 80% of the initial catalytic activity even after being used for 12 cycles. (C) 1999 Elsevier Science Ltd. All rights reserved.