Decolorization of the Textile Dyes Using Purified Banana Pulp Polyphenol Oxidase

Polyphenol oxidase (PPO) purified using DEAE-cellulose and Biogel P-100 column chromatography from banana pulp showed 12.72-fold activity and 2.49% yield. The optimum temperature and pH were found to be 30 degrees C and 7.0, respectively for its activity. Catechol was found to be a suitable substrate for banana pulp PPO that showed Vmax, 0.041 mM min-1 and Km, 1.6 mM. The enzyme activity was inhibited by sodium metabisulfite, citric acid, cysteine, and -mercaptoethanol at 10 mM concentration. The purified enzyme could decolorize (90%) Direct Red 5B (160 g mL-1) dye within 48 h and Direct Blue GLL (400 g mL-1) dye up to 85% within 90 h. The GC-MS analysis indicated the presence of 4-hydroxy-benzenesulfonic acid and Naphthalene-1,2,3,6-tetraol in the degradation products of Direct Red 5B, and 5-(4-Diazenyl-naphthalene-1-ylazo)-8-hydroxy-naphthalene-2-sulfonic acid and 2-(4-Diazenyl-naphthalene-1-ylazo)-benzenesulfonic acid in the degradation products of Direct Blue GLL.