A high efficient novel alginate-degrading microorganism was isolated from rotten seaweed using sodium alginate as the sole carbon source.Based on the morphological,physiological characteristics and 16S rDNA sequence,the strain was identified as Isoptericola halotolerans WX.The optimized fermentation medium was composed of sodium alginate 6.0 g/L,tryptone 5.0 g/L,yeast extract 2.5 g/L,NaCl 25.0 g/L,MgSO4 2 mmol/L,CaCl2 0.5 mmol/L,KH2PO4 1 mmol/L,FeSO4 0.2 mmol/L,and MnSO4 0.3 mmol/L.The optimal culture condition was that the strain was cultured in 250 mL shake flasks containing 20 mL medium with shaking speed of 180 r/min and initial pH 8.0 at 25 ℃ for 44 h.Besides,2 mmol/L Mg2+ and 0.2 mmol/L Fe2+ had remarkable effect on enzyme activity.Under the optimized conditions,the activity of alginate lyase was increased significantly from 32 U/mL to 432 U/mL,around 13-fold compared with the state without optimization.Additionally,Isoptericola halotolerans WX was demonstrated to possess the activity of amylase,which confers its extensive potential applications.