Reversible, selective immobilization of nuclease P1 from a crude enzyme solution on a weak base anion resin activated by polyethylenimine

The reversible immobilization of crude nuclease P 1 fermented by Penicllium citrinum and used without further purification was performed via adsorption on a weak base anion resin activated by polyethylenimine (PEI). The immobilization conditions, including PEI concentration, the amount of support, the immobilization time, and the reusability of the PEI-activated resin were investigated. The results have shown that the PEI-activated resin has the capability of selectively adsorbing nuclease P 1 . Subsequently, the functional properties of the immobilized nuclease P 1 were studied and compared to those of the free enzyme. The apparent K m value for immobilized nuclease P 1 on the activated resin (15.31   g   L −1 ) was about 4.41-fold higher than that of the free enzyme (3.47   g   L −1 ), and the apparent V max value of the immobilized enzyme (530   U   g −1 ) was about 3.9-fold less than that of the free enzyme (2082   U   mL −1 ). The optimum temperature was observed to be 70   °C, 15   °C higher than that of the free enzyme. The optimum pH was the same for both free and immobilized nuclease P 1 (pH 5.0). The apparent activation energies ( E a ) of the free and immobilized nuclease P 1 were 163.09   kJ   mol −1 and 156.32   kJ   mol −1 , respectively, implying that the catalytic efficiency of the immobilized enzyme was restricted by mass-transfer rather than kinetic limitations.