Abstract: The purpose of this work is to obtain a strain with an ability to degrade alginate. With sodium alginate as a sole carbon source,a strain of marine bacterium with the solid ability to degrade alginate was screened and purified from the cankered gulfweed,coded as X511. According to the morphological observation,physicochemical indexes and the techniques of molecular biology,the strain was identified as Vibrio,designated as Vibrio sp. X511. The exponential phase of strain X511 was about 5-16 h,and the suitable salinity for its growth was around 2%-6%（W/V）. It was capable to grow in the culture medium with a sole carbon source like glucose,mannitol,or starch,et al. Also,4%-6%（W/V）of the salinity,the kelp powder,and the laminarin extended its stationary phase. The activity of intracellular crude alginate lyase reached 12.68 ± 0.13 U/mL when the X511 fermented in the screening medium for 24 h. The intracellular crude alginate lyase was extracted,and its ability to digest alginate sodium,poly mannurono acid,and poly guluronic acid was measured as such order：alginate sodium > poly mannurono acid > poly guluronic acid. The results of the Thin Layer Chromatography（TLC）showed that the enzymatic degradation product of alginate sodium was trisaccharide. The above results indicate that the X511 is a marine strain with strong salt tolerance,short growth cycle,and it simultaneously utilizes the sodium alginate,poly mannurono acid,and poly-guluronic acid as its growing carbon resource.

Key words: alginate, screening, identification, salt tolerance, polysaccharides use