Biochemical characterization of a cold-adapted κ-carrageenase from Colwellia echini: A biotechnological tool for efficient preparation of carrageenan oligosaccharides

κ-Carrageenase (EC 3.2.1.83) is a glycoside hydrolase that efficiently breaks down κ-carrageenan into κ-carrageenan oligosaccharides (κ-COS). In this study, a novel GH16 family κ-carrageenase called CeCgkB was cloned from the genome of Colwellia echini. Escherichia coli BL21 (DE3) was used to express CeCgkB. CeCgkB has a complete length of 987 bp, encoding 329 amino acid residues, and a molecular weight of 37.44 kDa. Biochemical characterization indicated that CeCgkB exhibits cold-adapted properties and was able to reach a maximum activity of 1530 U/mg at pH 8.0 and 35 °C. Kinetic parameters showed that CeCgkB has a low K_m value (2 mg/mL), indicating high substrate affinity. As an endo-type κ-carrageenase, CeCgkB can degrade κ-carrageenan into products of varying DP, with a preference for DP4, DP6, and DP10. ESI-MS analysis revealed that the major products of CeCgkB consist of κ-carratetraose, κ-carrahexaose, and κ-carradecaose. As a result of CeCgkB's high activity, cold-adapted, and principal products, it is a promising biotechnological tool for the efficient preparation of κ-carrageenan oligosaccharides.