Eco-friendly Bleaching of Agrowaste Wheat Straw Using Crude Alkalo-Thermotolerant Cellulase-Free Xylano-Pectinolytic Enzymes.

Abstract

The aim of this study was to evaluate the potential of xylanase-pectinase enzymes in bleaching of wheat straw pulp, just to cut down the toxic wastes, in order to manage the environmental pollution. The appropriate parameters of bleaching were evaluated, and best conditions were xylanase and pectinase dose of 5.0 and 1.66IU/g of pulp, respectively, along with material to liquid ratio of 1:7.5 (g/ml), temperature 55°C, treatment time 3h, Tween-80 1%, and pH 8.5. The release of reducing sugar and other non-cellulosic impurities, phenolic-hydrophobic-lignin was maximum at best bleaching conditions. Prebleaching of wheat straw pulp using these enzymes showed 14.75% decline in kappa number. Enzymatic bleaching plus 100% chemical bleaching also led to 27.90% reduction in yellowness. Using this methodology, the consumption of active chlorine was reduced up to 25%, along with an increase in burst index (7.98%), tear index (3.42%), breaking length (5.30%), viscosity (11.22%), gurley porosity (12.50%), and double-fold number (23.08%), which exhibits a remarkable enhancement in all the properties of pulp treated with enzymes. Microscopic images also confirm the effectiveness of enzymatic treatment in bleaching of wheat straw pulp. BOD and COD values of effluent also decreased by 20.74 and 17.87%, respectively. This research focussing on producing better grade paper using an eco-friendly approach would certainly benefit the paper and pulp industry. This is the first report, depicting bleaching capability of xylanase-pectinase enzymes for soda-anthraquinone pulp of wheat straw.