Immobilization of Aspergillus niger tannase by microencapsulation and its kinetic characteristics.

Tannase from Aspergillus niger was microcapsulated with a coacervate calcium alginate membrane surrounding a liquid core. The activity yield was 36.8% under the optimum conditions of immobilization, namely 6 g/litre sodium alginate and 0.18 M CaCl(2). The optimum pH and temperature for free and immobilized tannase were 5.0 and 30 degrees C, and 6.0 and 40 degrees C, respectively. The pH stability, as well as thermal stability, was improved significantly after microencapsulation. K(m) values for the free and immobilized enzyme were 0.011 and 0.041 microM respectively. V(max) values changed from 416 to 131 micromol x min(-1) x mg(-1) upon immobilization. The kinetic parameters for free and immobilized tannase were also determined. The immobilized tannase was stable enough to be used for up to 15 runs. These kinetic characteristics of the immobilized tannase show more promise for industrial application than those of the free enzyme.