Modification of dissolving wood pulp using endoglucanase

Abstract

Dissolving wood pulp, a final product of the pulping and bleaching processes, with a cellulose content greater than 90%, has many applications. Each application requires specific properties of the dissolving wood pulp and to achieve these properties, alteration is required. Various techniques exist to modify cellulose, such as chemical, mechanical and enzymatic modification. Enzymatic modification has the benefits of reduced energy input, reduced chemical consumption during bleaching and viscose production, reduced environmental influence and a high specificity towards cellulose molecules. The aim of this study was to improve the properties (reactivity and viscosity) of dissolving wood pulp (cellulose) by treatment with endoglucanase enzymes. Therefore, the objectives of this study were to investigate the effects of two different formulations of endoglucanases, using a range of enzyme concentrations and incubation times, on pulp viscosity and reactivity and to integrate the enzyme treatments with a bleaching sequence. This study comprised two experimental phases. In the first phase, bench-scale tests were conducted on semi-bleached pulp to determine the best enzyme formulation to use. In the second phase, the enzyme treatments were integrated with a bleaching sequence to produce fully bleached pulp. The bench-scale tests showed that endoglucanase could successfully modify pulp properties. The pulp viscosity could be reduced by 50 to 100 units, with relatively low enzyme dosages (<250 mg/kg), without modifying the alkali solubility (S10) of the pulp (±5.5 %). Integration of the enzyme treatment with a bleaching sequence had several benefits. The treatment reduced chemical charges of pulp for ozone (40%) and peroxide (>63%), improved brightness, and resulted in economic benefits (>30% savings). These results show that endoglucanases can successfully reduce pulp viscosity without causing excessive damage to the cellulose. Integration of the enzyme with a bleaching sequence is straightforward and can lead to reduced chemical consumption and increased cost savings. In future studies, complete enzyme assays should be conducted to understand the limitations of the enzyme and the brightness boosting effect should be investigated for further benefits of the enzyme.