Effect of Direct-Current Electric Field on Enzymatic Activity and the Concentration of Laccase

Abstract

This work investigates the effect of direct-current electric field on the extracellular enzymatic activity, concentration and other experimental parameters of laccase from Trametes versicolor. The results showed that laccase could significantly contribute to the change of pH at the end of graphite electrode. In addition, it increased the electrical conductivity of the water. In the experiment, the optimum pH and catalytic pH range for laccase activity were 3.0 and pH 2.5-4.0. The application of 6 V direct current showed significant effects on the laccase enzyme activity. The activity of laccase was enhanced in the anodic region, but at the same time was strongly inhibited at the cathode. The electric charge characteristics of laccase were changed when exposed to electric field, and some laccases molecules moved to the anode, which produced a slight migration phenomenon. This study is the basis of combination of laccase and electrical technology, at the same time, providing a new direction of enhancing laccase activity. Compared to immobilization, using electric field is simple, no chemical additives, and great potential.

Keywords: Concentration; Direct-current electric field; Enzymatic activity; Laccase.

Fig. 1

Schematic view of the electric field apparatus

Fig. 2

Effect of electric field on pH and electrical conductivity of pure water environment. Squares, triangle and circle represent the environment in cathodic region, anodic region, and the middle region, respectively. Inverted triangle represents the environment without electric field. Every value represents the mean of in duplicate measurements

Fig. 3

Effect of Laccase on DC electric field mediated changes in pH and electrical conductivity. Squares, triangle and circle represent the environment in cathodic region, anodic region, and the middle region, respectively. Every value represents the mean of in duplicate measurements

Fig. 4

Catalytic activity of laccases in different pH. The effect of pH is determined using buffer solutions (HAc–NaAc) to obtain the desired pH in the standard assay method. The maximum activities of laccase is shown as 100 % in the figure. Every value represents the mean of triplicate measurements that varied from the mean by no more than 8 %

Fig. 5

Effect of electric field on the concentration of 4 U/ml laccases. Squares, triangle and circle represent the environment in cathodic region, anodic region, and the middle region, respectively. Inverted triangle represent the environment without electric field. Every value represents the mean of in duplicate measurements

Fig. 6

Effect of electric field on the different concentration of laccases. Squares, circle and triangle represent 1 U/ml laccases, 2 U/ml laccases, and 4 U/ml laccases, respectively. The initial concentration of 1, 2 and 4 U/ml laccases is 5.10, 12.04, and 23.16 µg/ml, respectively. Every value represents the mean of triplicate measurements that varied from the mean by no more than 5 %

Fig. 7

Effect of electric field on catalytic activity of 0.1 U/mL laccases. Circle, inverted triangle and triangle represent the environment in cathodic region, anodic region, and the middle region, respectively. Squares represents the environment without electric field. The maximum activities of laccase is shown as 100 % in the figure. Every value represents the mean of in duplicate measurements

Fig. 8

Effect of electric field on catalytic activity of 4 U/ml laccases. Circle, inverted triangle and triangle represent the environment in cathodic region, anodic region, and the middle region, respectively. Squares represents the environment without electric field. The maximum activities of laccase is shown as 100 % in the figure. Every value represents the mean of in duplicate measurements