Catalyzed degradation of disperse dyes by calcium alginate-pectin entrappedbitter gourd (Momordica charantia) peroxidase
Rukhsana Satar , Qayyum Husain
DOI:
Received July 24, 2010,Revised March 04, 2011, Accepted , Available online
Volume 23,2011,Pages 1135-1142
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Calcium-alginate pectin entrapped bitter gourd peroxidase (BGP) has been employed for the treatment of disperse dyes: Disperse
Brown 1 (DB 1) and Disperse Red 17 (DR 17). Peroxidase alone was unable to decolorize DR 17 and DB 1. However, the investigated
dyes were decolorized maximally by BGP in the presence of 0.2 mmol/L redox mediator, violuric acid (VA). A slow decrease in percent
decolorization was observed when VA concentration was higher than 0.2 mmol/L which could likely be due to the high reactivity of its
aminoxyl radical (> N–O.) intermediate, that might undergo chemical reactions with aromatic amino acid side chains of the enzyme
thereby inactivating it. Maximum decolorization of the dyes was observed at pH 3.0 and 40°C within 2 hr of incubation. Immobilized
peroxidase decolorized 98% DR 17 and 71% DB 1 using 35 U of BGP in batch process in 90 min. Immobilized enzyme decolorized
85% DR 17 and 51% DB 1 whereas soluble enzyme decolorized DR 17 to 48% and DB 1 to 30% at 60°C. UV-visible spectral analysis
was used to evaluate the degradation of these dyes and their toxicity was tested by Allium cepa test. The generally observed higher
stability of the bioaffinity bound enzymes against various forms of inactivation may be related to the specific and strong binding of
enzyme with bioaffinity support which prevents the unfolding/denaturation of enzyme. Thus entrapped peroxidase was found to be
effective in the decolorization of the investigated dyes.
