The fungal strain FBV40 was isolated from soil containing decayed wood in Ba Vi National Forest and capable of producing an extracellular laccase in the TSH1 medium. Two isozyme such as Lac1 and Lac2 were purified were estimated to be 55 and 60 kDa by SDS-PAGE. The optimum pH and temperature for the enzymatic activity of Lac1 were 3.0 and 60°C with ABTS using as the substrate. Kinetic constants Km and Vmax of Lac 1 were 0.3 µM and 200,000 µM/mins with ABTS as substrate. Cl-, SDS, and EDTA at any concentration (2 mM; 5 mM and 10 mM) strongly inhibited the activity of laccase. The enzyme was stable in the presence of several metal ions including Ni2+ (1 mM), Cu2+ (1 mM and 3 mM), Ca2+ (3 mM and 4 mM); in the presence of Cu2+ (2 mM) and Ca2+ (0.5 mM, 1.0 mM and 2.0 mM), laccase even showed the increase in the activity. The presence of metal ions Mn2+, Mg2+, Fe2+ completely inhibited the enzymatic activity at any examined concentration. The crude enzyme, as well as Lac 1, was able to decolourization MN.FBN dye from the textile industry from Ministry of Defence. This strain was able to degrade 2,3,7,8-TCDD isotop with initial concentration 2,000 ng-TEQ/L at rates over 46.8 % after ten days cultivation in the TSH1 medium. In the presence of three strains FBV40, FBVLa1 and FBD154 with the ratio 1:1:1, the degradation of this congener was achieved more than 95 % at the same time cultivation.
A new technique to estimate percentage decolorization of synthetic dyes on solid media by extracellular laccase from white-rot fungus
