Bioproduction of N-acetyl-d-glucosamine (GlcNAc) from chitin, the second most abundant natural renewable polymer on earth, is of great value in which chitinolytic enzymes play key roles. In this study, a novel glycoside hydrolase family-18 β-N-acetylglucosaminidase (PbNag39) from Paenibacillus barengoltzii suitable for GlcNAc production was identified and biochemically characterized. It possessed a unique shallow catalytic groove (5.8 Å) as well as a smaller C-terminal domain (solvent-accessible surface area, 5.1 × 103 Å2) and exhibited strict substrate specificity toward N-acetyl chitooligosaccharides (COS) with GlcNAc as the sole product, showing a typical manner of action of β-N-acetylglucosaminidases. Thus, an environmentally friendly bioprocess for GlcNAc production from ball-milled powdery chitin by an enzyme cocktail reaction was further developed. By using the new route, the powdery chitin conversion rate increased from 23.3% (v/v) to 75.3% with a final GlcNAc content of 22.6 mg mL-1. The efficient and environmentally friendly bioprocess may have great application potential in GlcNAc production.
Keywords: N-acetyl-d-glucosamine; ball milling; crystal structure; powdery chitin; β-N-acetylglucosaminidase.