The biological activity of chitooligosaccharides (COS) has made them targets for industrial and medical sectors. In this work, endo-chitinase Chit33 from Trichoderma harzianum CECT 2413 was expressed in Pichia pastoris GS115 to levels never achieved before (630 mg/L; 3.3 U/mL), without its biochemical characteristics being substantially affected. Chit33 produced a mixture of fully and partially acetylated COS from different chitin derivatives. HPAEC-PAD Chromatography and mass spectrometry analyses showed that (GlcNAc)4 and GlcN-(GlcNAc)2 were mainly produced from colloidal chitin and chitosan, respectively. COS in reaction mixtures were fragmented according to their size and their antioxidant activity analyzed by reducing power and free radical scavenging activity essays. The highest antioxidant activity was achieved with COS in the range of 0.5-2 and 2-10 kDa produced from colloidal chitin and chitosan, respectively, which gives biotechnological potential to both the chitin derivatives of 0.5-10 kDa and the biocatalyst producing them.
Keywords: Bioactive chito-oligomers; COS, chitooligosaccharides; Chitin; Chitosan; DD, degree of deacetylation; DP, degree of polymerization; FRAP, Ferric Reducing Antioxidant Power; GH, Glycoside Hydrolase; GlcN, D-glucosamine; GlcNAc, N-Acetyl-d-glucosamine; Heterologous expression; Pichia pastoris; RSA, Radical Scavenging Activity; paCOS, partially acetylated COS.
© 2020 The Authors. Published by Elsevier B.V.