Optimization of κ-carrageenase production by Pseudoalteromonas sp. AJ5

Abstract:

[Objectives] To optimize the culture conditions of Pseudoalteromonas sp. AJ5 for a higher production of extracellular κ-carrageenase. [Methods] A k-carrageenan-degrading bacterium AJ5, capable of utilizing k- carra-geenan as sole source of carbon and energy, was isolated from the intestine of holothurian Apostichopus japonicus by enrichment culture technique. The strain was identified as the genus Pseudoalteromonas sp. according to its morphological and physiological characterization and 16S rRNA gene analysis. Culture conditions for the bacte-rium were standardized for the maximal productivity of the extracellular k-carrageenase by the single factor and orthogonal tests. [Results] According to the single factor test, the optimal culture conditions were: 75 mL medium in 250 mL Erlenmeyer flask, shaking speed of 150 r/min, inoculum’s volume 7%, and pH 8.0. Based on the single factor and orthogonal tests the optimal medium components were: k-carrageenan (1 g/L), beef extract (2 g/L ), NaCl (20 g/L), K2HPO4·3H2O (1 g/L), MgSO4·7H2O (0.5 g/L), MnCl2·4H2O (0.2 g/L), FePO4·4H2O (0.01 g/L), with the incubation temperature and time of 28°C and 28 h. [Conclusions] Pseudoalteromonas sp. AJ5 secreted an extracellular k-carrageenase. Under the optimal culture conditions, four-fold increase in k-carrageenase activity was achieved as compared to the control.