Qualitative Assays and Quantitative Determinations of Laccases of White Rot Fungi from Plantation and Natural Forests of Arsi Forest Enterprise, Ethiopia

The white rot fungi (WRF) isolated from the plantation and natural forests of Arsi forest enterprise (Dagaga and Gambo sites) were screened for their ligninolytic potentials and their Laccases were quantitatively determined. The fungi were grown in both submerged fermentation (SmF) and solid state fermentation (SSF) of wheat bran (WB) and sawdust of Eucalyptus grandis (sawdust). The activities of Laccases of the fungal isolates were quantified and their productions were optimized. Quantification of Laccases indicated that the fungal isolates secreted their highest enzymes on the 8th day of SmF and on 12th day of SSF in WB and sawdust substrates. Laccase activities of SSF were higher than Laccase activities of SmF in both growth substrates. The highest Laccase activities of 0.345 U/ml and 0.379 U/ml were obtained during SmF and SSF of WB, respectively, by isolate 003-2G. Laccase activities of 0.430 U/ml and 0.446 U/ml were also obtained while SSF of sawdust by the same isolate. Laccase quantification data indicated sawdust to be more suitable than WB for Laccase production. 45 °C was most optimum for the Laccase activities and the enzyme was stable in the temperature range of 40-45 °C. It was also found that the Laccases of the fungi were active and stable at pH 5.0. Optimization experiments also revealed that production of Laccases from the fungal isolates can be maximized by adjusting the fungi cultivation conditions and supplementations of the growth media.