Purification and characterization of peroxidase from sprouted green gram (Vigna radiata) roots and removal of phenol and p‐chlorophenol by immobilized peroxidase

BACKGROUND Peroxidase activity was increased during germination of green gram and such an increase may have benefits in many physiological processes. The present study aimed to investigate the optimum conditions for the extraction, purification and characterization of peroxidase from the germinated green gram roots and also its application for the removal of phenols in water. RESULTS Peroxidase activity was increased by 300‐fold in 5‐day germinated green gram. Because the root was rich in peroxidase activity, peroxidase from roots was isolated and purified to homogeneity. The purified peroxidase showed a single band on sodium dodecyl sulphate‐polyacrylamide gel electrophoresis with a molecular weight of 50 kDa, an optimum pH of 5.5 and a pH stability ranging from 5 to 9. The enzyme had 50% residual activity at 70 °C. It catalyzed the oxidation of a variety of substrates. The Km value of the enzyme was 1.28 mmol L−1 for o‐dianisidine and 0.045 mmol L−1 for H2O2. The enzyme lost 100% activity in the presence of dithiothreitol and cysteine. The addition of copper ion increased the enzyme activity by three‐fold. Both soluble and immobilized peroxidases removed more phenol than p‐chlorphenol, whereas horseradish peroxidase removed more p‐chlorphenol. Thus, the green gram root peroxidase showed good pH and temperature stability, as well as the ability to remove phenolic compounds from effluent. CONCLUSION Peroxidase with good thermal and pH stability was purified from germinated green gram roots and has the ability to oxidize phenolic compounds from waste water. © 2016 Society of Chemical Industry