An extracellular protease was purified from a novel moderately halophilic bacterium Salinivibrio sp. strain MS-7 by the combination of an acetone precipitation (40-80 %) step and a DEAE-cellulose anion exchange column chromatography. Kinetic parameters of the enzyme exhibited V (max) and K (m) of 130 U/mg and 1.14 mg/ml, respectively, using casein as a substrate. The biochemical properties of the enzyme revealed that the 21-kDa protease had a temperature and pH optimum of 50 A degrees C and 8.0, respectively. The enzyme was strongly inhibited by phenylmethylsulfonyl fluoride, Pefabloc SC, chymostatin, and also EDTA, indicating that it belongs to the class of serine metalloproteases. Interestingly, Ba2+ and Ca2+ (2 mM) strongly enhanced the enzyme activity, while Fe2+ and Mg2+ activated moderately and Zn2+, Ni2+, and Hg2+ decreased the enzyme activity. The effect of organic solvents with different logP on the purified protease revealed complete stability in toluene, ethyl acetate, chloroform, and n-hexane at 10 and 50 % (v/v) and moderate stability even in 50 % of DMSO and ethanol. The behavior of the MS-7 protease in three imidazolium-based ionic liquids exhibited suitable activity in these green solvent systems, especially in 1-hexyl-3-methylimidazolium hexafluorophosphate ([C6MIM][PF6]). Comparison of the purified protease with other previously reported proteases suggests that strain MS-7 secrets a novel organic solvent-tolerant protease with outstanding activity in organic solvents and imidazolium-based ionic liquids, which could be applied in low water synthetic section of industrial biotechnology.