Laccase production and dye decolorization by Ganoderma lucidum

The production of high amount of laccase (EC 1.10.3.2) enzyme by different white rot fungi are very important for biotechnological applications. In this study, white rot fungus Ganoderma lucidum was used. First of all, this newly isolated G. lucidum was incubated on Sabouraud dextrose agar containing 2,2'-Azino-bis(3-ethylbenzathiozaline-6-sulphonic acid) (ABTS) as a laccase substrate to detect the possible laccase activity of this strain. The oxidation zone of ABTS showed the presence of laccase enzyme in this fungus. Then, laccase production ability of this fungus was investigated at different growth media under repeated bach conditions. Molasses medium was determined as the most effective growth medium for laccase production. Therefore, molasses medium was preferred as a laccase production medium and the effect of various inducers (copper, ABTS and 2,5-xylidine) on laccase production efficiency of this fungus was tested. Addition of copper induced the laccase production and 9.58 U/mL laccase activity was detected in molasses medium containing 5mM copper. The other two inducers (ABTS and 2,5-xylidine) had no effect on laccase production of this fungus. The possible synergistic effect of copper and ABTS, and also copper and 2,5-xylidine was also tested. Copper+2,5-xylidine exhibited a synergistic effect on laccase production activity of G. lucidum. Zymogram analysis showed only one band of laccase activity. The dye decolorization activity of this fungus against various reactive dyes was also investigated.