Horseradish peroxidase-assisted approach to decolorize and detoxify dye pollutants in a packed bed bioreactor. 
In this study, horseradish peroxidase (HRP) was covalently immobilized on the calcium-alginate support using glutaraldehyde (GA) as a cross-linking reagent for detoxification and degradation of synthetic dyes.  Immobilization procedure furnished significant immobilization efficiency (86.27 ± 3.43%) along with apparent and relative activity of 24.39 ± 1.03 U/g and 84.97 ± 3.54%, respectively, for immobilized-HRP.  In comparison to free-state, immobilized-HRP catalyzed the substrate oxidation reaction in a slightly acidic and wider temperature range, with an optimum at 60 °C.  After 10 and 60 min of incubation at 60 °C, the immobilized-HRP displayed 99.0% and 89.0% of residual activities, whereas the free counterpart retained only 34.0% and 18.0% of residual activities, respectively.  Moreover, the immobilized-HRP showed potential efficiency for the decolorization of dyes in sequential dye-decolorizing batch reactions.  Cytotoxicity analysis using a plant bioassay and acute test demonstrated that the Ca-alginate immobilized-HRP may effectively be used for detoxification of dyes and has a great potential for large-scale environmental remediation.