Biodeinking of mixed office waste paper by alkaline active cellulases from alkalotolerant Fusarium sp.

Abstract

Two extracellular alkalistable 1,4-β- d-glucan-4-glucanohydrolase (EC 3.2.1.4) fractions, namely Endo A and Endo B were separated from the culture filtrate of an alkalotolerant Fusarium strain by gel chromatography on Bio Gel P-100 column. The viscometric characterization of enzyme indicated that the Endo B was 1.9 times more random in action as compared to Endo A. Both the endoglucanases showed comparable patterns of their ability to release short fibers in the reaction mixture when filter paper was used as the substrate. The average size of released short fibers was determined by scanning electron microscopy ranged between 20 and 100 μm. Adsorption characteristics of the endoglucanases indicated that the enzyme complex acts prominently at the surface of substrate rather than at their cracked edges. The X-ray diffractograms showed that the crystallinity of the substrates does not vary significantly in the initial stages of the enzymatic action. The extracellular enzyme preparation was found to be suitable for deinking of mixed office waste papers. The enzyme treatment resulted in the increase in brightness with the reduction in ink counts of the recycled paper. Based on the distinct properties of endoglucanases a probable mechanism of enzymatic deinking process is presented schematically.