Grafted Carrageenan Gel Disks and Beads with Polyethylenimine and Glutaraldehyde for Covalent Immobilization of Penicillin G Acylase

Abstract

The precursor for production of 65% worldwide antibiotics, 6-aminopenicillanic acid, has been produced using covalently immobilized penicillin G acylase (PGA) onto modified grafted carrageenan gels. Two shapes of gel were prepared, gel disks and gel beads by using the parallel plates and Encapsulator devises, respectively. Different sizes of gel disks and beads were tested to choose the best sizes for both gel types. 2 2 Full-factorial central composite design (CCD) was applied for optimisation of enzyme loading process. The results revealed that maximal enzyme loading of 11.07 and 14.30 U/g of gel disks and beads respectively could be achieved after soaking the gels in an enzyme loading solution of 20 U of PGA for 16 h for both gel types. The generated model was found to be very adequate for PGA immobilization process 91% accuracy was attained for gel disks as the experimental value was 11.07 U/g disk compared to 10.1 U/g disk for the predicted value while 95% accuracy was attained using gel beads as the experimental value was 14.30 U/g beads compared to 14.07 U/g beads for the predicted value. This result is 40% higher than that obtained in our previous work using gel disks. The immobilization of PGA onto gel beads increased the optimum pH from 6 to 6.5–7 while the reaction temperature increased dramatically from 45 � Ct o 75 � C compared to the free enzyme, respectively. Thus, the modified carrageenan-polyethylenimine-glutaraldehyde gel beads could be a good and promising candidate for the industrial use.