(650i) Concanavalin a Coated Activated Carbon for Enzyme Immobilization

While the large pore size, good mechanical property, non-toxicity, as well as the availability of chemical or physical modification makes activated carbon (AC) an ideal support for enzyme immobilization, direct adsorption of enzymes onto AC often yields poor apparent activity and reusability. This might be attributed to the strong interaction that leads to undesired conformational changes of the adsorbed enzymes. Here we present a novel and facile method, as featured by coating AC with Concanavalin A (ConA), a lectin that specifically binds to glyosidic molecules, to prepare AC immobilized enzymes.

During a run, AC was loaded into ConA solution of appropriate concentration and incubated at room temperature for 12 hours. Then glycoenzyme such as laccase and HRP was loaded into the suspension of ConA coated AC and incubated for 12 hours. BSA, which was frequently used as a stabilizer of aqueous protein or during free drying was also used as a control to evaluate the stabilization effect of ConA. 

It is shown that HRP immobilized on ConA coated AC remained 50% initial activity after 25 cycles. In contrast, the directly adsorbed HRP on AC lost all activity after 12 cycles. Replace of ConA with BSA resulted in 18% apparent activity remain after 25 cycles. The laccase immobilized on ConA coated AC appeared 96% of initial activity after 11 cycles. In contrast, the direct adsorption of laccase on AC led to a reduction of apparent activity by 74%. Moreover, the immobilized enzymes showed a 2.5-fold increase in activity compared to direct adsorption and an improved stability over a wider range of pH and at a higher temperature. The high yield of activity, enhanced reusability and stability of immobilized enzyme, in combination with the high adsorption ability of AC, make the enzyme immobilized on ConA coated AC promising for various applications of enzymatic catalysis.