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

Abstract

Tannase produced optimally on an agroresidue by an Aspergillus niger isolate under submerged fermentation immobilized on sodium alginate beads with 93.6% effi ciency 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°C while the corresponding values of the soluble enzyme were 5.8 and 35°C. Maximum tannin removal of 73.6% was obtained at 40°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°C and 150 rpm in the same time period. The immobilized beads could be used repeatedly till 7th cycle with 77% effi ciency. When preserved at 6°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.

Catalytic properties of immobilized tannase produced from Aspergillus aculeatus compared with the free enzyme

“…This is an industrially promising result similar to that obtained by Sharma et al (2002) and Yu et al (2007). In addition, A. niger tannase immobilized on sodium alginate beads was used repeatedly for 7 cycles with 77% efficiency (Srivastava and Kar, 2010). …”

“…This increase of the optimum temperature is probably a consequence of enhanced thermal stability. The shift of optimum temperature to higher values after the immobilization of tannase was previously reported by Sharma et al (2008), Su et al (2010) and Srivastava and Kar (2010). The temperature data are replotted in the form of Arrhenius plots (Figure 4).…”

“…This may be attributed to an ionic change around the enzyme active site as result of the immobilization process (Krajewska et al, 1990). The shift of pH optima to more acidic pH values has been previously reported for other immobilized tannases (Abel-Naby et al, 1999, Srivastava andKar, 2010). In contrast, the optimal pH of the A. niger tannase entrapped in Ca-alginate was shifted to a more alkaline range (Yu et al, 2004).…”

“…Furthermore, improvement of the color and organoleptic properties of tea occurred when it was treated with tannase (Lu et al, 2009). Tannase is also used in clarification to remove the unwanted bitterness in many fruits juices, lowering haze without deteriorating juice quality (Rout and Banerjee, 2006;Srivastava and Kar, 2010). In animal feed, tannase is used to reduce the anti-nutritional effects of tannins and improve animal digestibility (Graminha et al, 2008;Murugan and Al-Sohaibani, 2010).…”

“…The operational stability of immobilized tannase is the most important factor affecting the release of gallic acid in tannin bioconversion and in other industrial applications in food, beverage and juices to remove the undesirable effects of tannins such as astringency, bitterness and deterioration of juice quality (CruzAldaco et al, 2009;Srivastava, and Kar, 2010;Belur and Mugeraya, 2011). The operational stability of immobilized tannase is evaluated in repeated batch processes.…”