Chitooligosaccharides (CHOS) can be obtained by partial and controlled enzymatic hydrolysis of chitin and chitosan. CHOS are oligomers of N-acetylglucosamine (GlcNAc) and glucosamine (GlcN; = deacetylated GlcNAc) and may vary in their degree of polymerization (DP), their degree of deacetylation (DD) and the pattern of acetylation. Although structure–function relationships for CHOS are still unclear, it is clear that the biological properties of CHOS depend on DP, DD and the acetylation pattern. Harnessing the application potential of CHOS requires that well-defined CHOS can be produced in an efficient and environmentally friendly manner.

As reported in other Deliverables, such as Deliverables 2.3 & 4.1, during the first half of the VALUABLE project, protocols have been developed that generate fungal chitin with a purity that is sufficient to allow its conversion to different derivatives, such as chitosan (Task 4.2, M1-35). The resulting fungal chitosans, with varying DD and produced as reported in D4.3, are hydrolysed enzymatically, to obtain CHOS with different size-distributions and DD, using well-established procedures previously developed by NMBU (Sørbotten et al., 2005; Horn et al., 2006; Aam et al., 2010; Rahman et al., 2014). CHOS have successfully been produced in g scale and will, after further analysis of the samples, be delivered to the end user partners in M19-M21.. In addition, we are developing an innovative enzymatic protocol for direct conversion of the fungal chitin to CHOS, thus avoiding the chitin -> chitosan conversion step, and this work has already given highly promising results.