Preparation of various aminooligosaccharides using a novel chitinase and its CBM fusion mutants

Aminooligosaccharides, including N-acetyl chitooligosaccharides (N-acetyl COSs), chitooligosaccharides (COSs), and partially acetylated chitooligosaccharides (paCOSs) have gained significant attention owing to their diverse bioactivities. Thus, the preparation of aminooligosaccharides particularly paCOSs, is a prospective way to reuse the huge amount of crustacean waste for high value-added products. In this study, a novel GH family 18 chitinase (MyChi54) suitable for aminooligosaccharides preparation was identified and characterized. MyChi54 showed maximal activity at pH 5.0 and 45 °C. Two CBM fusion mutants were obtained to enhance the enzyme activity. It should be noted that CBM26MyChi54 exhibited a 2.5-fold increase in chitinase activity (25.8 U mg^-1) relative to the wild-type, while CBM26MyChi54 and CBM3MyChi54 demonstrated enhanced chitinase activity against chitosan, displaying a 2.0- and 3.6-fold rise in comparison to the wild-type, respectively. The aminooligosaccharides were subsequently prepared by CBM26MyChi54 and three types of N-acetyl COSs, four types of paCOSs, as well as five types of COSs were obtained, and some of them were identified by HPLC and ESI-MS. It is conceivable that the bioprocess may be employed to considerable advantage in the enrichment of an aminooligosaccharides library.