Studying the activity and stability of Free and immobilized Laccase enzyme (Trametes versicolor) on Montmorillonite and zeolite minerals

Laccase is among the most important enzymes that has attracted much attention in the field of bioremediation in recent years, due to its ability to oxidize various compounds and persistent environmental pollutants. Since free from of Laccase has low operational stability with high cost of production, there are some limitations on the commercial applications in industrial and environmental biotechnology. In this regard, immobilization of such enzymes on absorbent surfaces can be a good way to increase stability and operational life of the enzyme. In order to examine the interactions between Laccase (Trametes versicolor) with Montmorillonite and zeolite minerals, three different experiments were done separately in a completely randomized design with two replications in vitro conditions. Experiments were included four levels of pH (5, 6, 7 and 8), nine levels of temperature (4 °C and 10-80 °C) and seven levels of incubation time (0, 1, 2, 5, 10, 20 and 30 days), respectively. Based on the results, the highest enzyme adsorption on the surface of studied minerals was observed in pH=5 and enzyme absorption decreased with increasing pH. Furthermore, the highest relative activities were obtained for free Laccase at 20 °C, for immobilized Laccase on Montmorillonite at 80 and 4 °C and for immobilized Laccase on zeolite at 4 and 70 °C. Immobilized Laccase showed a remarkable stability to low and high temperatures. Maximum relative activity (100%) for immobilized Laccase on Montmorillonite and zeolite was observed in 20th day of incubation time and for free Laccase in 5th day of incubation time. Indeed, immobilization indicated a proper effect on Laccase enzyme activity retention.