Removal of lignin and hexenuronic acids from sisal fibers with novel xylanases belonging to different GH families

Abstract

The aim of this study was to evaluate five different preparations of xylanases from Paenibacillus barcinonensis, a highly xylanolytic species, who is able to grow on xylan as a sole carbon source. As raw material to assess, fibers from sisal (Agave sisalana) were chosen. Sisal pulps were bleached by an XP sequence, where X denotes the enzyme treatment and P a hydrogen peroxide extraction stage. Kappa number, brightness, viscosity and hexenuronic acid content of samples were determined. Sugars released from sisal pulps, other non-wood fibres and also eucalyptus fibres, by the treatment with the xylanases were also analysed. The best results were obtained with the GH10 xylanase and with crude supernatants of P. barcinonensis, which produced a lignin removal of 23% and a reduction of 25% in the hexenuronic acid content of sisal pulps without a significant loss of viscosity. The xylanases of family GH30 showed good performance, being more efficient when applied as a single catalytic domain. On the contrary, Xyn11E did not show any significant effect on pulp properties. The release of sugars in the effluents from the X stage applied to sisal correlated with the effectiveness of the xylanases tested. The xylan content of wood and non-wood fibres, the type of xylan and its accessibility also had an influence on the xylanase activity on pulps