The Effects of Recombinant Cellulomonas fimi β-1,4-glycanases on Softwood Kraft Pulp Fibre and Paper Properties

摘要

Recombinant Cellulomonas fimi β-1,4-endoglucanases (Ce15A and Cel6A) and cellobiohydrolases (Cel6B and Cel48A) were assessed for their capacity to selectively modify the physical and optical properties of handsheets derived from a fully bleached, never-dried softwood pulp. The isolated binding domain (Cel6A CBD) and catalytic domain (Cel6A CD) were also evaluated. Treatment with endoglucanases, particularly Cel6A CD, caused substantial damage to the intrinsic fibre strength of the kraft furnish, and consequently compromised the physical handsheet properties. In contrast, treatment with Cel48A produced beneficial modifications, including improvements in handsheet tensile strength following mechanical refining and various degrees of wet pressing. Cel6B and Cel6A CBD had very limited effects on the fibre characteristics, and therefore did not alter the quality of the handsheets produced. An examination of carbohydrate solubilization and changes in the degree of polymerisation of the polysaccharides indicated that the capacity for Cel48A to beneficially modify pulp and paper characteristics seems to be related to its capacity to selectively degrade cellulose-hemicellulose linkages, and release and modify xylan moieties. Furthermore, this enzyme preparation demonstrated limited carbohydrate dissolution, indicating that the observed modifications were attained with very little yield loss. These results suggest that Cel48A, and enzymes with similar glycanase activity should be considered and further evaluated for their potential to treat pulp fibres to improve paper properties.