Low-molecular-weight chitosans: Preparation and characterization

► Oxidative reaction depolymerized chitosan to two fractions of LMW chitosans. ► First fraction with Mw 7-9 kDa has lower deacetylation degree (DD) 70-80%. ► Second fraction with Mw 8-10 kDa has higher DD 87-94%. ► The content of chitosan oligomers in LMW chitosan fractions was roughly 20-30 wt%. ► Enzymatic hydrolysis was the best in preparing chitosan oligomers with polymerization degree 2-10.