Objective: We screened and identified protease-producing bacterial strains from the Arctic, the results would help find cold-adapted protease.
Methods: In total 68 protease-producing strains were screened from the Arctic using the casein-agar plate under low temperature. All strains were classified using the 16S rRNA gene-restriction fragment length polymorphism (RFLP) and traditional phenotypic test. One strain was chosen to be the representative strain from each group respectively and identified using 16S rRNA gene sequence analysis, GenBank database Basic Local Alignment Search Tool (BLAST), phylogenetic analysis and phenotypic features analysis. The enzymatic properties of the representative strains were determined.
Results: The 68 strains belonged to 3 groups (54.41%, 42.65% and 2.94%), and strains 6, 11 and 52 were the representative strains respectively. The results of the 16S rRNA gene sequence analysis showed that: Strain 11 was most closely related to Chryseobacterium scophthalmum with 98.24% sequence similarity; strain 52 was most closely related to Stenotrophomonas rhizophila with 98.55% sequence similarity; strain 6 was most closely related to Stenotrophomonas rhizophila with 96.50% sequence similarity, which might represent a novel species of the genus. The phenotypic study showed that: strains 6, 11 and 52 were Gram negative, straight rod-shaped, did not produce extracellular lipase and amylase, possessed strong proteolytic activity. The optimal temperature and pH for the enzyme activity were 55 degrees C and 6.7 for the protease from strain 6, 40 degrees C and 8.5 for the protease from strain 11 and 65 degrees C and 7.4 for the protease from strain 52.
Conclusion: The research firstly introduced the distribution of Stenotrophomonas and Chryseobacterium specieses in the Arctic marine water, extended the diversity of the protease-producing bacteria from the Arctic, and provided a useful basis for further study of cold-adapted protease.