This paper illustrates the application of enzymes (e.g. xylanase and laccase) in the bio‐bleaching of non‐woody material (e.g. wheat straw). The objective of this paper is to develop an alternative bleaching sequence avoiding the use of chlorine during bleaching. In the study, wheat straw pulp has been treated with commercially available xylanase and laccase separately and sequentially. Optimised parameters for the xylanase pre‐treatment are pH 5.5, temperature 60°C, enzyme dose 6 IU/g, pre‐treatment time 75 min and speed of agitation 80 rpm. Similarly, optimum parameters for laccase delignification are pH 3.5, temperature 60°C, enzyme dose 22.5 IU/g of oven dried pulp, mediator concentration 1.5% of oven dried pulp (odp), delignification time 10 h and speed of agitation 120 rpm. On the other hand, sequential treatments such as xylanase pre‐treatment (X) followed by laccase (L) and alkaline perdoxide (E) in presence of mediator have shown better reduction in kappa number, that is 24.84% as compared to LE in presence and absence of a mediator.

In the present work, a novel approach to pretreat wheat straw pulping was investigated with ultrasound and xylanase to achieve maximum reduction in lignin content. Sequential xylanase pretreatment and alkaline pulping was found to reduce kappa number by 0.31 to 4.84 % compared with only alkaline pulping alone at different pulping conditions. Although Klason lignin of ultrasound-treated straw was found to be 7.37 % less compared with untreated straw, sequential ultrasound pretreatment and alkaline pulping could not show any significant reduction in kappa number compared with alkaline pulping alone. Also, sequential xylanase and ultrasound pretreatment could not show any significant reduction in kappa number. Total yield of the pulp was found to be less in ultrasound-assisted processing compared with both alkaline pulping alone and sequential xylanase pretreatment and alkaline pulping.