Statistical Optimization of Biobleaching Efficacy of endo-β-1,4-xylanase from an Actinobacterium Streptomyces olivaceus (MSU3) in Comparison with Zinc Oxide Pretreated Sugarcane Bagasse Pulp Using Box–Behnken Design

Abstract

ABSTRACT The bio-bleaching efficacy of endo-β-1,4-xylanase from an actinobacterium Streptomyces olivaceus (MSU3) was studied by using sugarcane bagasse pulp in comparison with chemical-mediated bleaching. Before that, the sugarcane bagasse pulp was processed with various concentrations of xylanase (20–100IU) and zinc oxide (0.2–1.0 g) individually through laboratory conditions. Simultaneously, both enzyme- and chemical-mediated bleaching process were optimized through response surface methodology by using the reaction condition containing pH 6.6, temperature 47°C with the incubation time of 3 h. The analysis of variance of the parameters expressed the maximum level of coefficient (R 2 = 0.963–0.996) with more significant (P < 0.0001). In bleaching process under-optimized conditions, the highest level of reducing sugar (110.02 mg/g), reduction of kappa number (14.69 k), degree of brightness (43.62%ISO), level of residual lignin (2.20%) with the discharge of phenolic (λ 237 = 0.119 OD), and hydrophobic (λ 465 = 0.046 OD) groups were attained in xylanase (80.0 IU) mediated bleaching than zinc oxide bleaching. Further, the effect of bleaching on processed pulp samples with loosening and changes of surface cell fiber was examined by field emission scanning electron microscopic analysis. The efficient fibrillation and porosity of pulp fiber were seen in xylanase bleached pulp than chemical-bleached pulp. These results clearly indicated that the endo-β-1,4-xylanase of the chosen actinobacterium could able to bleach the bagasse pulp effectively than the zinc oxide-mediated bleaching.