A Novel laccase from Lentinus sp.

Abstract

Laccase is known to play an important role in various industrial applications, such as biopulping, pretreatment of lignocellulosics for bioethanol production, dye decoloration, and bioremediation. A native laccase protein of Lentinus sp. was purified and identified as N‐linkage glycosylated by LC/MS‐MS analysis. Kinetics study showed that the specific activity of the purified laccase was 2047 U mg−1 at pH 2.5 and 70°C with ABTS as the substrate. The kcat, Km and catalytic efficiency (kcat/Km) of the enzyme were 2017 s−1, 8.4 μM, and 240 s−1μM−1, respectively. The enzyme was stable at pH 2.5–6.0, and t1/2 of enzymatic activity was approximately of 20 min at 70°C and pH 2.5 and 118 h at 25ºC and pH 6.0. Differential scanning calorimetry analysis demonstrated that the laccase possesses a high Tm value at 77.1°C. Glycosylation was found to play an important role to the enzymatic activity. N75D, N236D, N399D, and N458D mutant laccases exhibited approximately 80–100% decreases in enzyme activity. The laccase showed a good stability against ethanol and remained 80% of the original activity after a 120‐h incubation in 25% ethanol. We found 34% lignin degradation efficiency on rice straw with crude laccase enzymes, and 47% decoloration efficiency on Remazol Brilliant Blue R with partial purified laccase. The fungal laccase identified in this study possesses novel functions with great potential in bio‐industrial applications.