Effect of commercial xylanases applied at extreme conditions in a eucalyptus pulp mill

Abstract

In this study, we examined the effect of treating eucalyptus pulp with various commercial xylanases to identify the most effective enzyme for use under the industrial bleaching conditions used at the Jacareí mill of the Brazilian firm Fibria, which include a high pH and temperature. Based on the results, the use of two of the nine enzymes studied reduced the kappa number by 1.5 units, increased brightness by 2.5% ISO, and decreased hexenuronic acids (HexA) content by more than 10 μmol/g relative to a control treatment in the absence of enzyme. The most marked changes in brightness were observed on application of an oxidative D stage to enzyme-treated pulp samples. Finally, the chemical oxygen demand (COD), total organic carbon (TOC), color, and turbidity of the effluents obtained at the end of the processes involving the enzymes were all higher than in the control process. Application: The use of xylanases can raise productivity in mills with limited ability to produce chlorine dioxide, can potentially reduce bleaching reagents cost, and can increase the flexibility of the bleaching sequence