The function of lipase in laccase delignification of wheat straw

The fat and wax on the surface of wheat straw inhibit permeation of cooking reagent in cooking. Due to the lipase can decompose fat and wax, wheat straw is treated with the mixture of lipase and laccase in order to increase the permeation of cooking reagent and improve the pulping performance. The optimum conditions of lipase pretreatment and the optimum ratio of lipase and laccase were investigated in this paper. The results indicated that the optimum conditions for lipase pretreatment were: pH value 5.5, pretreatment temperature 45°C, liquor to raw material ratio 5:1, dosage of lipase 0.7 IU/g. The optimum ratio of lipase and laccase was 20:80. The pulp yield after cooking increased by 14.1% and 2.0%, the kappa number decreased by 23.7% and 2.9% respectively for the untreated and only laccase treated wheat straw. The strength and brightness of the pulp were improved obvi ously. The breaking length and brightness increased by 11.9% and 1.7% SBD respectively for the sample treated with the mixture of lipase and laccase compared with the sample only treat with laccase. The function of lipase in laccase delignification was confirmed by SEM analysis.