ABSTRACT:The model enzyme -galactosidase was entrapped in chitosan gel beads and tested for hydrolytic activity and its potential for application in a packed-bed reactor. The chitosan beads had an enzyme entrapment efficiency of 59% and retained 56% of the enzyme activity of the free enzyme. The Michaelis constant (K m ) was 0.0086 and 0.011 mol/mL for the free and immobilized enzymes, respectively. The maximum velocity of the reaction (V max ) was 285.7 and 55.25 mol mL Ϫ1 min Ϫ1 for the free and immobilized enzymes, respectively. In pH stability tests, the immobilized enzyme exhibited a greater range of pH stability and shifted to include a more acidic pH optimum, compared to that of the free enzyme. A 2.54 ϫ 16.51-cm tubular reactor was constructed to hold 300 mL of chitosan-immobilized enzyme. A full-factorial test design was implemented to test the effect of substrate flow (20 and 100 mL/min), concentration (0.0015 and 0.003M), and repeated use of the test bed on efficiency of the system. Parameters were analyzed using repeated-measures analysis of variance. Flow (p Ͻ 0.05) and concentration (p Ͻ 0.05) significantly affected substrate conversion, as did the interaction progressing from Run 1 to Run 2 on a bed (p Ͻ 0.05). Reactor stability tests indicated that the packed-bed reactor continued to convert substrate for more than 12 h with a minimal reduction in conversion efficiency.
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