Identification of a proteolytic bacterium, HW08, and characterization of its extracellular cold-active alkaline metalloprotease Ps5.

A psychrophilic protease-producing bacterium, HW08, was isolated from sediment of the Yellow Sea in eastern China. On the basis of 16S rDNA sequence analysis and physiological properties, the isolate was identified as Pseudomonas lundensis. The secreted protease, named Ps5, was purified from the culture supernatant as a monomer with an apparent molecular mass of 46 kDa on SDS-PAGE. As a metalloprotease (inhibited by EDTA), the enzyme showed maximum activity at 30 degrees C at pH 10.4. It had no activity loss exposed at 4 degrees C for 60 d or under repeated freezing and thawing. Broad temperature (25-40 degrees C) and pH (7.0-11.0) stability was observed in the presence of 5 mm Ca(2+). Furthermore, the enzyme was resistant to detergent additives such as non-ionic surfactants and bleaches. It showed considerable potential for industry that requires alkaline-protease.