Isolation Of Algin-Degrading Bacteria, Fermentation And Some Properties Of Alginase

The algin is abundant in brown algae and a common intercellular substance in all brown algae. The algin degradation products which have more advantages than algin have various potential applications in biomedical, pharmaceutical, agricultural, and food field. The development of viable processes for degradation of algin is an attracting growing interest. However, further investigation is required for practical application of this enzyme.In this study, 52 strains have been isolated with alginase activity from the decaying parts of Laminaria japonica and Undaria pinnatifida and 12 of them show higher enzyme activity than the others.Among the 12 strains, the Strain X7 showed the highest alginase activity during the second screening and demonstrates a good stability, so it is chosen to investigate the fermentation condition and some properties of alginase produced by strain X7.There are many factors that influence the alginase production. It was found that the strain can not produce alginase without sodium alginate and can not grow without NaCl. The different carbon sources tests also showed that the alginase of Strain X7 was an induced enzyme. The strain grew significantly better in organic nitrogen resources such as beef extract than inorganic nitrogen resources like (NH4)2SO4, so it produced much larger amount of alginase in fermentation medium which contained organic nitrogen resources. When incubated at 25℃for 48h in the liquid medium which contains 1g beef extract, 0.5g yeast extract, 0.6g sodium alginate, 0.5g NaCl, 0.1g MgSO4.7H2O, 0.5g K2HPO4, 0.001g FeSO4.7H2O and 100 ml tag water, the strain X7 produces the highest amount of alginase. The highest alginase activity is 654.7U/ml.The alginase of the strain X7 is extracted by ammonium sulfate precipitation(30～80% saturation), purified by ion-exchange chromatography (Q-Sepharose Fast Flow column) and gel filtration (Sephacryl S-100 column).