Production of hexaoligochitin from colloidal chitin using a chitinase from Aeromonas schubertii

• The optimal conditions for hexaoligochitin production by chitinase ASCHI61 were studied.
• The production of hexaoligochitin in E. coli was determined by experimental design.
• The interactive effect between chitin concentration and pH was the most significant.
• A maximum 42.175 mg L−1 hexaoligochitin was obtained at pH 6.55 from 3.4 mg mL−1 chitin.

Chitin derivatives, such as those with modified main saccharide chains and deacetylated side chains, exhibit versatile biological functions. The biomedical properties of chitin oligosaccharides depend on their degree of oligomerization. Of the chitin oligosaccharides, chitin hexamers are generally the most potent. In our recent study, N-acetylchitohexaose was obtained by digesting chitin with ASCHI61, a chitinase from Aeromonas schubertii. In this work, the factors involved in the production of chitin hexasaccharide were evaluated experimentally. Using steep map analysis and cross-analysis, the substrate concentration and reaction pH were identified as the key factors in this reaction, and the interactions between these parameters were observed. Using a response surface experimental design, we predicted that a colloidal chitin concentration of 3.4 mg mL−1 and a pH of 6.54 were the optimal conditions for producing hexaoligochitin. These conditions were verified in separate experiments, in which 38.73 mmol L−1 of N-acetylchitohexaose was obtained. The maximum amount of hexamer produced was 42.175 mg L−1, an increase of only 0.27% from the predicted value.