Purification and Characterization of Protease from Marine B. thuringiensis SWJS07
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Abstract:
The protease produced by the marine strain B. thuringiensis SWJS07 was purified to homogeneity by ultrafiltration, ammonium sulfate precipitation, anion-exchange chromatography (DEAE-Sepharose Fast Flow) and gel filtration chromatography (Sephadex G-75), with a 6.39-fold increase in specific activity and 37.14% recovery and the molecular weight was estimated to be 37.0 kDa on SDS-PAGE. The optimal temperature and pH for the purified protease were determined to be 55 ℃ and pH 6.5. The protease was highly stable from 30 ℃ to 45 ℃ and between pH 6.0 and 9.0 and it was activated by Ca2+and Mn2+, while Hg2+, Cd2+, Al3+ had a strong inhibitory effect. The optimal temperature were 60 ℃ and 55 ℃ in the presence of 2 mM Ca2+and Mn2+, and the activity were increase by 32.86%, 28.35%, respectively. Meanwhile, thermostability of the protease was enhanced by Ca2+ and Mn2+. In the presence of 2 mM Ca2+and Mn2+, the activity of the protease were retained unchanged after heating for 30 min at 60 ℃, however, it retained 21.02% of its initial activity in the absence of them. It was strongly inhibited by EDTA-Na2, indicating that the protease may be metalloprotease.
