Production of <i>N</i>‑Acetyl‑d‑glucosamine from Mycelial Waste by a Combination of Bacterial Chitinases and an Insect <i>N</i>‑Acetyl‑d‑glucosaminidase

<i>N</i>-Acetyl-d-glucosamine (GlcNAc) has great potential to be used as a food additive and medicine. The enzymatic degradation of chitin-containing biomass for producing GlcNAc is an eco-friendly approach but suffers from a high cost. The economical efficiency can be improved by both optimizing the member and ratio of the chitinolytic enzymes and using new inexpensive substrates. To address this, a novel combination of bacterial and insect chitinolytic enzymes was developed in this study to efficiently produce GlcNAc from the mycelia of Asperillus niger, a fermentation waste. This enzyme combination contained three bacterial chitinases (chitinase A from Serratia marcescens (<i>Sm</i>ChiA), <i>Sm</i>ChiB, <i>Sm</i>ChiC) and one insect <i>N</i>-acetyl-d-glucosaminidase from Ostrinia furnacalis (<i>Of</i>Hex1) in a ratio of 39.1% of <i>Sm</i>ChiA, 26.7% of <i>Sm</i>ChiB, 32.9% of <i>Sm</i>ChiC, and 1.3% of <i>Of</i>Hex1. A yield of 6.3 mM (1.4 mg/mL) GlcNAc with a purity of 95% can be obtained from 10 mg/mL mycelial powder in 24 h. The enzyme combination reported here exhibited 5.8-fold higher hydrolytic activity over the commercial chitinase preparation derived from Streptomyces griseus