A novel immobilization method for nuclease P1 on macroporous absorbent resin with glutaraldehyde cross-linking and determination of its properties

Microbial nuclease P1 from Penicllium citrinum was immobilized on macroporous absorbent resins: strong polar poly (styrene-co-DVB) resin (SPPSD), polymethacrylic ester resin and poly (styrene-co-DVB)-Br resin. The results showed that SPPSD was the best carrier. Three methods of glutaraldehyde cross-linking were used and simultaneous immobilization and cross-linking (CIS) was demonstrated to be the best method. The functional properties of immobilized nuclease P1 were studied and compared to those of the free enzyme. The highest enzyme activities of free and immobilized nuclease P1 were obtained in 0.2 M acetate buffer at pH 4.5 and a temperature of 70 °C. An increase in Km (from 3.165 to 18.125 mg mL−1) and a decrease in Vmax (from 1667.18 to 443.95 U min−1 mL−1) were recorded after immobilization. SPPSD-glutaraldehyde-nuclease P1 exhibited better thermal stability than the free enzyme. The apparent activation energy (Ea) of the free and immobilized nuclease P1 was 137.04 kJ mol−1 and 98.43 kJ mol−1, respectively, implying that the catalytic efficiency of the immobilized enzyme was restricted by mass-transfer rather than kinetic limit.