Immobilization of Laccase in Alginate Beads

Abstract

The elimination or degradation of micropollutants from wastewater is becoming ever more important nowadays. Using oxidoreductase enzymes to treat different micropollutants seems a promising solution. However, the viability of the process is highly dependent on the availability and stability of the applied enzymes. In order to improve the stability and provide faster reaction rates, enzymes can be immobilized in various carriers. Properties such as simple production, easy retention and biodegradable carrier material are advantageous, e.g. entrapping laccase in alginate beads. This paper shows the results of the preparation and characterization of immobilized laccase entrapped in calcium alginate beads. The technique of adding a mixture of sodium alginate and laccase dropwise into calcium chloride has been applied, improved and standardized to produce laccase-containing beads of uniform size and activity. For the purpose of characterization, a widely used substrate, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, was used to evaluate the performance of the laccase-containing alginate beads. In addition to the characterization of the laccase-containing alginate beads, the enzyme kinetic constants (= 26.43 µM, ax = 0.23 µM/min) were determined. The reduction in the activity during storage has been described by a decay constant (0.26 d−1 ) that provides information concerning the design constraints of the process. Results will be used to test the method in terms of the removal of organic micropollutants in continuous systems.