A Novel Xylan-Polyvinyl Alcohol Hydrogel Bead with Laccase Entrapment for Decolorization of Reactive Black 5

Wichnaee Bankeeree, Sehanat Prasongsuk, Tsuyoshi Imai, Pongtharin Lotrakul, Hunsa Punnapayak

Abstract


In an attempt to find a more efficient technique for biodegradation of the recalcitrant Reactive Black 5 (RB-5) dye, a composite xylan-polyvinyl alcohol (xylan-PVOH) hydrogel was used to immobilize laccase from the white-rot fungus Trametes versicolor. Xylan was prepared from the black liquor of pulp and paper effluent, and it was esterified with citric acid prior to cross-linking with polyvinyl alcohol (PVOH). The optimum composition for the immobilized laccase bead formation consisted of 4% (w/v) modified xylan, 10% (w/v) PVOH, and 15 U.mL-1 crude laccase. The maximum decolorization of RB-5 (98.45  1.96 %) was obtained within the first cycle (6 h) at 40 °C. In the eighth cycle, the reused beads were able to decolorize 55.35  2.46 % of the RB-5. Moreover, the xylan-PVOH beads extended the optimum pH range of laccase activity from 6 to 10 and tolerated a temperature up to 10 °C higher than that of the free enzyme. These results suggest that the xylan-PVOH bead has great potential as the polymer matrix for enzyme immobilization, which has applications in wastewater treatment.

Keywords


Reactive Black 5; Trametes versicolor; Alkaline tolerant; Immobilization; Hydrogel

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