Effects of Enzymatic Removal of Xylan and Glucomannan on the Pore Size Distribution of Kraft Fibres

Abstract

The effects of enzymatic removal of xylan and glucomannan from pine and birch kraft pulps on the pore size distribution and median pore width of the pulp fibres were determined by modified solute exclusion and NMR techniques. With the NMR method, clearly higher median pore sizes of the kraft fibres were obtained compared with the solute exclusion method. However, the effects of enzymatic treatments on pore size distributions and median pore widths of fibres were detected by both techniques. An increase in the pore width of both pine and birch kraft fibres was observed even after a limited xylanase treatment. The NMR technique appeared to be more suitable than the solute exclusion method for determination of the further increase of the median pore width and the widening of the pore size distribution of fibres by a more extensive xylanase treatment. Both techniques revealed an increase of the median pore width of fibres caused by the extensive removal of pine kraft pulp glucomannan. Despite their basic differences and specific limitations, both the NMR and solute exclusion techniques showed the enzymatic effects on the porosity of pulp fibres.

The enhancement of enzymatic hydrolysis of lignocellulosic substrates by the addition of accessory enzymes such as xylanase: is it an additive or synergistic effect?

“…It is also worth noting that the xylanase-aided bleaching treatment of cellulosic pulps promoted physical changes to the pulp fibers, such as an increase in fiber porosity and fiber disintegration [18,22,23]. Similar changes during hydrolysis of lignocellulosic biomass are likely to increase the available specific surface area of the cellulose to cellulase enzymes and therefore the effectiveness of the cellulases, a process termed amorphogenesis [41].…”

NMR cryoporometry to study the fiber wall structure and the effect of drying

“…NMR relaxometry, has previously been used on pulp suspensions to detect the fiber surface area as well as the pore size distribution (PSD) (Li et al 1993). NMR relaxometry provided higher median pore radii than solute exclusion and ISEC (Maloney et al 1997;Suurnäkki et al 1997). This has been explained by pore systems with ''bottle-neck'' gateways, which will not be detected by the techniques using macromolecules as probes since these cannot enter the bottle-necked pores (Alince 2002), whereas water can.…”

Effects of Modified Cooking on Fiber Wall Structure of E. globulus and E. nitens

“…In the last few decades, the pore structure of the fiber walls has received a considerable amount of research attention (Kerr and Goring 1975;Suumaki et al 1997;Alince and van de Ven 1997;Berthold 1997;Selenius and Lindström 1997;Hubbe et al 2007;Sjöstedt 2014). This is appropriate because the "geometry" of pores in the fiber walls (i.e., size, shape, and arrangement) influences many aspects of fiber behavior.…”