Gum Tragacanth Gels as a New Supporting Matrix for Immobilization of Whole-Cell

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We introduce a new smooth, non-toxic, biocompatible method for cross-linking of gum tragacanth (GT), a polysaccharide of natural origin, in order to serve as a new supporting matrix for immobilization systems.  The modified gum is used as a matrix for the catalysis of the conversion of benzyl penicillin to 6-aminopenicillanic acid (6-APA) by means of Escherichia coli ATCC11105 with penicillin G acylase (PGA) activity.  The results show that GT beads can not only serve as a proper matrix for immobilization, but show enhanced hydrolysis rate and stability compared to other immobilization systems used for this reaction.  This signifies the potential of GT as a biocompatible matrix for immobilization and its positive prospects for use in more demanding immobilization applications where traditional matrices such as alginate may fall short. The effect of environmental factors, such as temperature, pH, and substrate concentration, have also been studied on the hydrolysis rate and compared with the other immobilizing systems used for the same reaction, such as calcium alginate.  Under the optimal conditions, penicillin G conversion reached 91.5% after 6 h and remained over 80% after 45 repeated cycles of 6 h each.