Immobilization of laccase in κ-carrageenan based semi-interpenetrating polymer networks

Laccase enzyme (L) was immobilized by entrapment into semi-interpenetrating polymer networks (semi-IPNs) prepared from κ-carrageenan with either poly(acrylamide–acrylic acid) [P(AAm–AA)/κ-car] or poly(acrylamide–itaconic acid) [P(AAm–IA)/κ-car]. For both systems, immobilized enzymes achieved the same optimum values observed for free enzyme (pH = 5.0 and T = 40 °C), except for P(AAm–IA)/κ-car system there was a shift to 5.5 in optimum pH value. At the end of 42 days of storage immobilized enzymes retained more than 80% of their original activities while the retained activities of both systems after 10 uses in batch type application were found to be higher than 50%. Km values were calculated as 2.52 × 10−2 mM and 1.08 × 10−2 mM and Vmax values were found as 6.8 × 10−3 mM min−1 and 4.4 × 10−3 mM min−1, for P(AAm–AA)/κ-car–L and P(AAm–IA)/κ-car–L, respectively. When methyl orange containing solutions (10 mg/L) were treated with the immobilized laccases (68.2 U), enzymatic decolorization of methyl orange in 6 h was achieved to the level of 35% for both systems. Supplementing the reaction medium with ABTS as the redox mediator increased this value to about 70%. These initial results show that, laccase containing semi-IPNs can find some applications in decolorization of the industrial wastes.