Decolorization of the Textile Dyes Using Purified Banana Pulp Polyphenol Oxidase

Abstract

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°C and 7.0, respectively for its activity. Catechol was found to be a suitable substrate for banana pulp PPO that showed V_max, 0.041 mM min⁻¹ and K_m, 1.6 mM. The enzyme activity was inhibited by sodium metabisulfite, citric acid, cysteine, and β-mercaptoethanol at 10 mM concentration. The purified enzyme could decolorize (90%) Direct Red 5B (160 μg mL⁻¹) dye within 48 h and Direct Blue GLL (400 μg 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.

KEY WORDS:

• banana
• dye decolorization
• enzyme purification
• polyphenol oxidase
• remediation

ACKNOWLEDGMENTS

We are thankful to Dr. Rajaram P. Patil for his fruitful suggestions and Mr. Nilesh V. Pawar for his technical assistance.