Expression and characterization of a κ-carrageenase from marine bacterium Wenyingzhuangia aestuarii OF219: A biotechnological tool for the depolymerization of κ-carrageenan

κ-Carrageenases are desirable tools for tailoring the molecular weight, physicochemical properties and functionalities of κ-carrageenan, a macromolecule widely utilized in various industries. In this study, a novel GH16 family κ-carrageenase, designated as Cgk16A, was cloned from the genome of marine bacterium Wenyingzhuangia aestuarii OF219 and expressed in Escherichia coli. Its biochemical properties, kinetic parameters and hydrolytic pattern were characterized. The enzyme demonstrated a low optimal reaction temperature (25 °C) and a cold-adapted feature. As an endo-acting glycoside hydrolase, Cgk16A degraded κ-carrageenan in a random manner, and it was competent to prepare the degradation products with varying degrees of polymerization. The mass spectrometry analysis revealed that the end products of Cgk16A were majorly composed of κ-carrageenan tetrasaccharide with a minor portion of disaccharide. The enzyme showed higher enzyme-substrate affinity over all hitherto characterized GH16 κ-carrageenases, indicated by its low Km value (0.17 μM). Cgk16A could be employed as a potential biotechnological tool for depolymerizing κ-carrageenan, which would facilitate the future application of κ-carrageenan and its degradation products.