Development of Coconut Shell Activated Carbon-Tethered Urease for Degradation of Urea in a Packed Bed

Coconut shell activated carbon (AC)-tethered urease (from jack bean) was successfully developed to degrade urea in a packed bed reactor. The loading capacity of urease in AC was 78.8 mg/g. The tethered enzyme showed a maximum activity at 70 °C and pH 7.2. For higher than 75% of the maximum activity, the tethered urease showed a broader temperature range of 42–80 °C compared to 45–75 °C for the free enzyme. Similarly, the tethered urease had an increased stability against the changes of pH. The Km value of the free urease was 0.271 mol/L and 0.345 mol/L for the tethered one. This may be caused by the conformational changes of the enzyme. The Vmax values were 0.215 and 0.110 mol/min for the tethered and free ureases, respectively, which is reflected by an increase in catalytic activity. The catalytic degradation of urea was performed in a packed bed reactor. The remaining activity of the tethered urease was over 80% after 50 h of operation.