Application of immobilized tannase from Aspergillus niger for the removal of tannin from myrobalan juice

Tannase produced optimally on an agroresidue by an Aspergillus niger isolate under submerged fermentation immobilized on sodium alginate beads with 93.6% efficiency was applied for tannin removal from myrobalan/aonla (Phyllanthus emblica) juice. The pH and temperature optima of the immobilized enzyme were found to be 5.4 and 40 degrees C while the corresponding values of the soluble enzyme were 5.8 and 35 degrees C. Maximum tannin removal of 73.6% was obtained at 40 degrees C and 150 rpm in 180 min with 36.6 U/ml of immobilized enzyme while the same amount of the soluble enzyme removed 45.2% of tannin at 37 degrees C and 150 rpm in the same time period. The immobilized beads could be used repeatedly till 7th cycle with 77% efficiency. When preserved at 6 degrees C the beads retained 71.7% of enzyme activity after 60 days. Reduction in vitamin C content, which is responsible for antioxidant property of the fruit, was minimum at only 2% during the treatment.