Talaromyces verruculosus tannase immobilization, characterization, and application in tea infusion treatment

Abstract

Partially purified tannase of Talaromyces verruculosus (305.6 U/mL) was immobilized on calcium alginate beads (8.0 ± 1.0 mm) using 1% glutaraldehyde as a cross-linking agent. Immobilized enzyme preparation retained (39.4%) 120.4 U/mL tannase activity, 79.6% immobilization yield, and 49.5% efficiency. Immobilized preparation was characterized by SEM and it revealed the changed topology of the immobilized bead. Functional groups present in immobilized beads were examined by FTIR spectra. Immobilized tannase was found optimally active at pH 8.0 and 60 °C, whereas the stability was obtained between 30 and 60 °C, but at high (9.0) and low pH (4.0), immobilized tannase was also found very stable. Beads were found stable up to 9th cycle of reuse with 49.27% relative activity. After the treatment by immobilized tannase, 78.02 ± 1.93, 72.24 ± 2.05, 65.29 ± 1.21, 59.06 ± 0.96, and 64.61 ± 1.07% tannin reduction were measured in black tea product 1, black tea product 2, black tea product 3, green tea product 1, and green tea product 2, respectively. The greatest change in pH, turbidity, and antioxidant activity was found in black tea product 2 infusion while the least change was obtained in green tea product 2 infusion after the tannase treatment.