Novel thermally and mechanically stable hydrogel for enzyme immobilization of penicillin G acylase via covalent technique

kappa-Carrageenan hydrogel crosslinked with protonated polyethyleneimine (PEI+) and glutaraldehyde (GA) was prepared and evaluated as a novel biocatalytic support for covalent immobilization of penicillin G acylase (PGA). The method of modification of the carrageenan biopolymer is clearly illustrated using a schematic diagram and was verified by FTIR, elemental analysis, DSC, and INSTRON using the compression mode. Results showed that the gels' mechanical strength was greatly enhanced from 3.9 kg/cm(2) to 16.8 kg/cm(2) with an outstanding improvement in the gels thermal stability. It was proven that, the control gels were completely dissolved at 35 degrees C, whereas the modified gels remained intact at 90 degrees C. The DSC thermogram revealed a shift in the endothermic band of water from 62 to 93 degrees C showing more gel-crosslinking. FTIR revealed the presence of the new functionality, aldehydic carbonyl group, at 1710 cm(-1) for covalent PGA immobilization. PGA was successfully immobilized as a model industrial enzyme retaining 71% of its activity. The enzyme loading increased from 2.2 U/g (control gel) to 10 U/g using the covalent technique. The operational stability showed no loss of activity after 20 cycles. The present support could be a good candidate for the immobilization of industrial enzymes rich in amino groups, especially the thermophilic ones. (c) 2008 Wiley Periodicals, Inc.