Xylooligosaccharides from lignocellulosic biomass: A comprehensive review

• For LCB pretreatment, the alkaline method is recommended. • For XOS production, enzymatic hydrolysis of pretreated LCB is advised. • For enzymatic hydrolysis, the use of auxiliary enzymes is recommended. • For XOS purification, ultrafiltration followed by nanofiltration is advised. • For XOS characterization, HPAEC-PAD analysis is recommended. Xylooligosaccharides (XOS), produced from lignocellulosic biomass (LCB), are short-chain polymers with prebiotic activity which, in the last few decades, have gained commercial interest due to their potential application as ingredients for the nutraceutical industry. This article reviews relevant topics to consider when researching XOS productive processes, such as the selection of raw materials and strategies for XOS production, purification, characterisation, quantification and evaluation of the prebiotic effects. With regard to the production approach, this article focuses on LCB pre-treatments and the enzymatic hydrolysis of xylan, exploring the reported alternatives and enzymes. A critical view on the current process reveals that comparative analysis between different studies is difficult due to the lack of consensus on the criteria and parameters used in the evaluation of XOS production processes. However, the most generally recommended XOS production strategy is the two-stage approach through alkaline pre-treatment and enzymatic hydrolysis with further purification through membrane filtration.