Study On An Antarctic Psychrophilic Bacterium Colwellia Sp.NJ341 Producing A Cold-Adapted Protease And Its Low-Temperature Adaptation

Antarctica, due to its specific geographical position and climate, which characterized by strong seasonal changes in light and UV intensity, low-temperature (–50℃in winter), high dissolved oxygen and high-salinity (150‰salinity in sea ice saline channels), is considered an extreme environment on the earth. To be colonized in this extreme environment, microorganisms form gradually a series of physiological, chemical and molecular mechanisms. Therefore, Antarctic microorganisms provide a useful model system for studying cold adaptation, and also are the optimal sources of cold-adapted enzymes. It is of not only greatly biological value to study on these microorganisms and their cold-adapted enzymes, but also important practical value due to their potential for biotechnological applications. Consequently, selecting Colwellia sp.NJ341 as a research material, we describe the optimization of its cold-adapted protease production using RSM, purification and characterization of its cold-adapted protease, and unveil strain's low-temperature adaptation mechanisms. The results are summarized as follows.(i) Protease activity of the cultures from 260 strains of Antarctic bacteria was qualitatively screened using the method of flat proteolysis casein Niujin. The results showed that there were 107 strains formed clear zones, meaning that they secreted the extracellular protease and protease activity of five strains NJ276, NJ341, NJ5-9, NJ16-70 and NJ345 was higher than 45 U/ml. The growth and producing protease characteristics of four Antarctic psychrophilic bacteria were studied, and the result showed that there were different among the strains. Proteases from NJ276 and NJ16-70 were mesophilic proteases, while NJ341 and NJ345 proteases were cold-adapted proteases. The 16S rRNA gene sequences homology and phylogenetic analysis showed that NJ276,NJ5-9,NJ16-70,NJ345 belonged to the described genus Pseudoalteromonas sp., and NJ341 belonged to the genus Colwellia sp.(ii) Antarctic psychrophilic bacteria Colwellia sp.NJ341 was chosen for the further...