Enzymatic degradation of glucosaminoglucan and cellulase resistance of cellulose nanofiber coated with glucosaminoglucan.

Abstract

Enzymatic degradation of β-1,4-linked glucose and glucosamine (glucosaminoglucan, GG), which is prepared from Thiothrix nivea and can act as a cellulose-aminating agent with a strong affinity to cellulose, was attempted. A chitosanase-secreting fungal strain was isolated as a GG-degrading microbe. GG was found to be degraded by not only chitosanases but also cellulases. Based on nuclear magnetic resonance spectroscopy, both enzymes were found to produce GlcN-Glc from GG. The cellulases also produced GlcN-Glc-GlcN-Glc as an additional final digest. Furthermore, aminated (GG-coated) cellulose nanofibers exhibited cellulase resistance. The flexibility of GG adsorbed onto a cellulose crystal was almost identical to that of cellulose, as estimated via the molecular dynamics calculations. The chitosanase and cellulase hydrolyzed the β-1,4-linkage from Glc to GlcN and were expected to recognize the tetramer and hexamer units of GG depending on their final products. The cellulose nanofibers acquired cellulase resistance via amination with GG, probably because of the lower activity of cellulase to GG than cellulose.