Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 575, Issue -, Pages 1352-1360Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.scitotenv.2016.09.215
Keywords
Horseradish peroxidase; Encapsulation; Chitosan beads; Thermo-stability; Dye decolorization; Reusability
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In this study, horseradish peroxidase (HRP) was immobilized onto chitosan beads by entrapment method and employed for the degradation of textile dyes. Stable and firm quality chitosan beads developed with 2.5% chitosan concentration exhibited maximum immobilization yield (similar to 92.54 +/- 2.53%). The pH optimum of chitosan-immobilized HRP (CTS-HRP) was marginally displaced towards alkaline region (pH 7.5) than that of F-HRP which displayed its optimum activity at pH 7.0. The free HRP (F-HRP) and CTS-HRP enzyme presented their maximum catalytic activities at 30 degrees C and 70 degrees C, respectively. Relative activities of F-HRP and CTS-HRP were decreased following pre-incubation above 30 degrees C and 50 degrees C, respectively and after 120 min at 70 degrees C, the F-HRP, and CTS-HRP retained 19.3 +/- 1.3 and 48.3 +/- 2.4% activities, accordingly. The CTS-HRP exhibited remarkably better resistance towards heavy metal induced activity inhibition. The effect of potential inhibitors on the activity of F-HRP and CTS-HRP was investigated and found that CTS-HRP was significantly less vulnerable to the denaturation caused by urea, ethylenediaminetetraacetic acid (EDTA), cysteine, 1, 4-dithiothreitol and Triton X-100. Moreover, the CTS-assisted entrapped-HRP was also employed for the decolorization of four different textile dyes i.e. Remazol Brilliant Blue R (RBBR), Reactive Black 5 (RB5), Congo Red (CR) and Crystal Violet (CV). The CTS-HRP showed considerable decolorization efficacy in six consecutive batch operations. Results suggest that CTS-HRP is an attractive choice for use as industrial biocatalyst in larger scale bioremediation of textile dyes and effluents. (C) 2016 Elsevier B.V. All rights reserved.
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