Laccase based de-inking of mixed office waste and evaluation of its impact on physico-optical properties of recycled fiber

Abstract

The de-inking ability of the crude laccase (benzenediol: oxygen oxidoreductase, EC 1.10.3.2) produced by a white rot fungus Peniophora sp. (NFCCI-2131) was tested using mixed office waste paper. In addition, the impact on physical and optical properties of the de-inked pulp, and the chemical load of the effluent generated during laccase based de-inking process was also analyzed. In the present study, 2.5 U/ml laccase was produced by the fungus under submerged culture conditions. Laccase (10 U/g of air dried pulp) was found to improve the tensile strength of recycled pulp by 1.7-fold, de-inking efficiency by 1.5-fold, opacity by 3.84%, and brightness by 5.83%. Scanning electron microscopy analysis revealed less rupturing of cellulose fibers and increased detachment of ink particles from the surface of the fibers in comparison to chemical de-inking. Fourier-transform infrared spectroscopy analysis of laccase treated pulp revealed degradation of the guaiacyl group and a high degree of deformation in methyl group of lignin. The biochemical and chemical oxygen demand (BOD and COD) were found to be reduced by 52 and 36% respectively, in the effluent generated after crude laccase based de-inking of mixed office waste.