**2. Methods of isolation of xylan-rich hemicelluloses**

Hemicelluloses are the second most abundant non-crystalline linear or branched polysaccharides after cellulosic one, which can be isolated from plant resources (**Figure 1**) or some bio-based industrial processes. It is a predominant byproduct of chemical and mechanical pulps [5, 6] in pulp industries and is severely wasted without an appropriate treatment. However, they could be used as a renewable matrix material with tunable functionality and biocompatibility in the field of pharmacy, cosmetic, food, etc. Hemicelluloses have lower molar masses than cellulose. Xylan is the principal structural hemicellulosic polysaccharides, present as 15–30% and 7–10% in hardwood and softwood, respectively. The major chain of xylan is composed of D-xylopyranosyl residues as backbone, which is linked by β-(1 → 4) glycosidic linkages, is similar to that of cellulose with a missing C-6 group. However, in marine

**Figure 1.**

*Working plan for delignification and xylan isolation.*
