A comparative study of free laccase and laccase immobilized in copper alginate

Sunkar, Swetha ; G, Ranimol

Abstract

Enzyme immobilization has gained considerable attention due to the incredible properties exhibited by the enzymes in immobilized condition. Therefore, in the present study, a comparative analysis of free and immobilized laccase is reported using various substrates. The ideal substrate for immobilization was found to be copper alginate with an immobilization yield of 91.078%. The optimum pH was 4 and 5, respectively, for free and immobilized enzymes while the optimum temperature was found to be 50 and 60C, respectively. The kinetic parameters Vmax and Km were found from the Line weaver-Burk plot and were 48.076 U/mL and 0.480 mM for free enzyme while 55.55 U/mL and 1.277 mM for the immobilized enzyme, respectively. The catalytic efficiency Kcat was found as 100.01s1 for free enzyme and 43.5s1 for its immobilized counterpart. Out of the various metal ions used, Co2+ was found to enhance the activity of an immobilized enzymes. The storage stability of the enzyme was studied and was found that only 32.44% of initial activity was retained by free enzyme whereas, 70.21% of activity was retained by immobilized enzyme upon storage for four weeks at 4C. The thermal stability studies shows that the immobilized enzyme retained 32.60% of its initial activity and the free enzyme retained 1.14% of initial activity on exposure to 60C for 3 h. Finally, the reusability of immobilized laccase beads was evaluated by decolorization of methyl orange for five repeated cycles and a percentage decolorization of 32.04% could be retained at the fifth cycle. This study therefore, suggests copper alginate-immobilized beads to be an effective option for various applications

Keyword(s)

Copper alginate; Immobilization; Laccase; Stability analysis; Storage analysis

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