Xylanase and laccase aided bio‐bleaching of wheat straw pulp

Abstract 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.