Characterization of laccase from Trichoderma sp. UBDFT12 isolated from a Bornean tropical forest

Aims: This study was aimed to characterize laccase from a selected fungal strain and examine the enzyme's ability to remove lignin from paper pulp. Methodology and results: Twelve fungal strains were screened for laccase production, resulting in the selection of Trichoderma sp. UBDFT12. The highest laccase activity (103 U/L) was observed from the culture filtrate on the fourth day of incubation. The optimum temperature and pH for the enzyme were 40 degrees C and pH 4, respectively. However, the enzyme stability was found to be reduced with time after 1 h incubation. At 1 mM, it was found that AgNO3, CaCO3, CuSO4, KCl, MgSO4, MnSO4 and ZnSO4 increased the laccase activity to 107, 107, 111, 112, 106, 105 and 107%, respectively, whereas FeSO4 and NH4Cl reduced the activity to 84 and 99%, respectively. The addition of 1% H2O2, 1% NaCl, 1% sodium dodecyl sulphate (SDS), 1 mM ethylenediaminetetraacetic acid (EDTA), 10 mM EDTA, 1 mM phenanthroline and 10 mM phenanthroline reduced the activity to 95, 73, 0, 79, 79, 73 and 37%, respectively. The culture filtrate was partially purified via ammonium sulphate precipitation and the recovered enzyme had a specific activity of 0.176 U/mg. Using sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE), the molecular weight of the enzyme was approximately 65 kDa and its activity was confirmed by zymography. The culture filtrate was also found to be able to remove lignin from different types of paper pulp. Conclusion, significance and impact of study: Laccase produced by Trichoderma sp. UBDFT12 was found to have the ability to remove lignin from paper pulp.