Abstract
We purified and investigated an extracellular ligninolytic enzyme, lignin peroxidase (LiP) from Aspergillus terreus LD-1 cultured with the medium containing highly alkaline cooking waste of manila hemp. This LiP was purified 10.8-fold with 8.2% yield by five steps using ammonium sulfate fractionation and a series of column chromatographies from the culture supernatant to elicit a single band upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) . The molecular weight of this LiP was estimated to be 24 kDa by SDS-PAGE and 22 kDa by gel permeation chromatography, suggesting a monomeric structure. The optimum pH of this LiP was pH 9.5 and the enzyme was stable in the pH range from 9.0 to 10.0. No activity was shown under pH 8.0. This enzyme is activated by 1 mM Fe2+ up to 1.3-fold and inhibited by Hg2+, Pb2+ and Ag+ completely. Maleate (1mM) increased the enzyme activity 2-fold. EDTA (1mM) inhibited the enzyme activity completely. Absorption spectrum of the enzyme suggested that the enzyme contains protoporphyrin IX. This LiP has potential for use in the pulp and paper industry to treat highly alkaline cooking or bleaching waste.
