Xylooligosaccharides production by acid hydrolysis of an alkaline extraction filtrate from Eucalyptus globulus bleached kraft pulp

Abstract

Xylooligosaccharides (XOS) are emerging prebiotics with several benefits for both physical and mental health. Their production from lignocellulosic materials is a challenging process, as lignin hinders xylan availability for XOS formation.In this study, bleached kraft pulp from Eucalyptus globulus, a lignin-free material, was used for XOS production. An alkaline extraction with 10 % NaOH to isolate the xylan was performed and the resulting filtrate was submitted to an acid hydrolysis with HNO3. When firstly concentrated by ultrafiltration, this alkaline filtrate allows the recycling of some NaOH, making the process more economic and sustainable, with no influence on the yield of XOS. Within 30 min at 100 °C and pH 0.5, a maximum conversion of xylan to XOS of 30.2 % was obtained, with xylobiose and xylotriose (40 %) prevailing. Although a high amount of xylose (45 %) was produced, the formation of other by-products, such as furfural, was not detected.