Production Of Laccase From Coprinus Comatus And Its Application In Decolorization Of Dyes And Bleaching Of Pulp

In this paper, an optimum condition was found to improve the expression level of laccaseLac1in Pichia pastoris. The condition follow as: pH7, initial inoculation amount at30(OD600),Cu2+400μM, methanol1.5%, casamino acid0.5%in BMMY cultured at25℃,250rpm. InducedLac1at the condition for6days, the enzymatic activity reached up to0.938IU/mL.The laccase Lac1pproduced from Pichia pastoris and LacApfrom Coprinus comatus werepurified by DEAE Sepharose CL-6B and Sephadex G-75. The purification fold of them was1.14and17.72with the overall yield were10.07%and9.88%, respectively. The molecular weight ofthe purified lacase from Coprinus comatus and the purified laccase Lac1was estimated to be70kDa on SDS-PAGE.In the paper,14dyes were used for decolorization test. These were indicated from thecontrast test in several conditions that: The decolorization of anthraquinone and triphenylmethanedyes by the crude/purified laccase (LacAc/LacAp) from Coprinus comatus and the crude/purifiedlacase Lac1(Lac1c/Lac1p) were better than the decolorization of azo dyes. After HBT added asthe mediator, both the decolorization rates of LacAc/LacApand Lac1c/Lac1pwere increased. Withor without mediator, both the decolorization rates of Lac1pwere better than the decolorizationrates of Lac1c. With or without mediator, both the decolorization rates of LacApwere better thanthe decolorization rates of LacAc, with little difference. It was indicated that LacApplayed a mainrole.With or without mediator, poplar wood pulp after bleached by Lac1c, the rate of pulp lignin,brightness, viscosity, tear strength and bursting strength were improved. Bleached pulp by Lac1cwith the mediator violuric acid, lignin decreased mostly. Without mediator, the brightness of pulpbleached by Lac1cwas best. With or without violuric acid, the viscosities of pulp bleached byLac1cwere increased successively. However, when instead of violuric acid by ABTS and veratrylalcohol, the viscosities were decreased. The tear strength of pulp bleached by Lac1cwithmediator was better than without, follow as the order: veratryl alcohol, Violuric acid, and ABTS.With or without mediator, the bursting strength were increased, follow as the order: veratrylalcohol, Violuric acid, Lac1cand ABTS.