Xylanase recycling for the economical biobleaching of sugarcane bagasse and straw pulps

In this work, the applicability of xylanases in sugarcane straw pulps and the possibility of recovering this enzyme were evaluated. A commercial xylanase (Pulpzyme HC) was used for pulp treatment and this enzyme was recovered and reused several times in the new pulp enzymatic treatment without addition of new enzyme load. In addition, a combined process of pulping was also evaluated, such as the fungal pretreatment of straw (biopulping) and the acetosolv pulping. Quantity of recovered enzyme in the first treatment was approximately 7% of initial enzyme load. After the second treatment no enzyme recovery was possible. Several factors interfered on xylanase recovery, such as pulp type, treatment medium (buffered or aqueous) and the methodology employed in the enzyme recovery. An alkaline extraction stage was carried out to verify the action of Pulpzyme on enzymatic treated pulps, but due to concentration of NaOH used in the stage differences were not observed in the kappa numbers and viscosity of the pulps. The Fourier transform infrared and principal component analyses (FTIR–PCA) were used to analyze sugarcane bagasse pulps of a previous work and FTIR–PCA showed differences among untreated, xylanase-treated and alkaline-extracted pulps of sugarcane bagasse.