Application of chitosan‐entrapped β‐galactosidase in a packed‐bed reactor system

The model enzyme β‐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 μmol/mL for the free and immobilized enzymes, respectively. The maximum velocity of the reaction ( V max ) was 285.7 and 55.25 μmol mL −1 min −1 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 × 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 0.003 M ), and repeated use of the test bed on efficiency of the system. Parameters were analyzed using repeated‐measures analysis of variance. Flow ( p < 0.05) and concentration ( p < 0.05) significantly affected substrate conversion, as did the interaction progressing from Run 1 to Run 2 on a bed ( p < 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.