Low Concentration Ionic Liquid-Assisted Efficient Enzymatic Degradation of Xanthan

One of the main obstacles to preparing oligoxanthan through the enzymatic degradation of xanthan gum (XG) is its dense structure. To achieve the large-scale production of oligoxanthan, it is necessary to perturbate the conformation of XG and increase enzyme accessibility. This research developed an efficient system for the enzymatic degradation of XG assisted by low concentrations of ionic liquids (ILs). Structural characterization results indicated that a low concentration of [EMIM]DEP (1%, v/v) not only loosens the structure of XG but also alters the secondary structure of enzyme, thereby dramatically increasing its hydrolytic activity and eventually enhancing the production of oligoxanthan. The results were further elucidated by molecular dynamics (MD) simulation. Under the hydrolysis conditions of 1.5 mg/mL Aspergillus niger cellulase (AnCel), 0.2 mg/mL XG, and 1% (v/v) [EMIM]DEP at 40°C and pH 5.0 for 20 min, XG can be hydrolyzed into a mixture with a glucose equivalent of 32.25%. The degree of polymerization (DP) of XG hydrolysates was 3-10. Moreover, the xanthan hydrolysates obtained using this system exhibit excellent antioxidant activity. This study proposed an effective method for the preparation of functional oligosaccharides, which is of significant importance for the valorization of XG.