Purification and characterization of a new thermostable κ-carrageenase from the marine bacterium Pseudoalteromonas sp QY203

A new extracellular kappa-carrageenase, namely CgkP, 34.0 kDa in molecular weight, was purified from Pseudoalteromonas sp. QY203. CgkP showed relatively high activity at acidities ranging from pH6.0 to pH9.0 and temperatures ranging from 30A degrees C to 50A degrees C with the highest activity at 45A degrees C and pH7.2. Sodium chloride increased its activity markedly, and KCl increased its activity slightly. The divalent and trivalent metal ions including Cu2+, Ni2+, Zn2+, Mn2+, Al3+ and Fe3+ significantly inhibited its activity, while Mg2+ did not. CgkP remained 70% of original activity after being incubated at 40A degrees C for 48 h, and remained 80% of the activity after being incubated at 45A degrees C for 1 h. It exhibited endo-kappa-carrageenase activity, mainly depolymerizing the kappa-carrageenan into disaccharide and tetrasaccharide. CgkP was more thermostable than most of previously reported kappa-carrageenases with a potential of being used in industry.