Immobilization of Aspergillus oryzae tannase and properties of the immobilized enzyme

Abstract

. Tannase enzyme from Aspergillus oryzae was immobilized on various carriers by different methods. The immobilized enzyme on chitosan with a bifunctional agent (glutaraldehyde) had the highest activity. The catalytic properties and stability of the immobilized tannase were compared with the corresponding free enzyme. The bound enzyme retained 20·3% of the original specific activity exhibited by the free enzyme. The optimum pH of the immobilized enzyme was shifted to a more acidic range compared with the free enzyme. The optimum temperature of the reaction was determined to be 40°C for the free enzyme and 55°C for the immobilized form. The stability at low pH, as well as thermal stability, were significantly improved by the immobilization process. The immobilized enzyme exhibited mass transfer limitation as reflected by a higher apparent K m value and a lower energy of activation. The immobilized enzyme retained about 85% of the initial catalytic activity, even after being used 17 times.

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

“…At high H + concentrations, the amino groups of gelatin would be protonated, thereby attracting hydroxide ions, which would maintain a higher microenvironmental pH than in the bulk solution and thus stabilize the immobilized enzyme (Cao, 2005). These results are in agreement with those obtained for other immobilized tannases (Abdel-Naby et al, 1999;Yu et al, 2004). …”

“…The plots of both free and immobilized tannase were linear and the activation energy of immobilized tannase was lower (7.6 kcal mole -1 ) than the activation energy of free enzyme (9.8 kcal mole -1 ). These results are similar to those reported for immobilized and free A. oryzae tannase (Abdel-Naby et al, 1999). This decrease in the activation energy may be due to the diffusion limitations (Yu et al, 2007).…”

“…Entrapment inside a semi-permeable membrane capsule using sodium alginate is very common and cost effective and shows good performance in industrial applications. As anticipated, Abdel-Naby et al (1999) observed a higher activity of tannase when cross-linked to the surface of chitosan beads than when entrapped in polyacrylamide or calcium alginate. Tannase could be bioaffinity immobilized on concanavalin ASepharose CL-4B beads (Sharma et al, 2002) and microencapsulated in a coacervate calcium alginate membrane (Yu et al, 2004), with higher conversion of methyl gallate/tannic acid into gallic acid than with the free enzyme.…”

“…The wet chitin was mixed with 4.0 ml of the enzyme solution (300 U; A. aculeatus tannase) for 1.0 h at room temperature (23-25°C). The unbound tannase were removed by washing with 0.1M acetate buffer pH 5.5 (Abdel-Naby et al, 1999).…”

“…According to Abdel-Naby et al (1999), A. aculeatus tannase solution (4.0 mL, containing 300 U) was mixed with different concentrations of sodium alginate (Pharmacia chemicals) to final concentrations of 3.0, 5.0, and 7.0%. The entrapment was carried out by dropping alginate solution in 0.1 M CaCl 2 solution.…”