Isolation and identification of an alkaline protease producing strain and study on enzymatic properties

Abstract:

[Objective] We isolated and identified a protease producing bacterium from Rhizoma Imperatae. [Methods] The species and abundances of bacteria from Rhizoma Imperatae were determined by high-throughput sequencing. The protease producing strain was screened by using selective medium containing casein. Besides, the effects of environmental factors on bacterial growth and protease activity were determined by single factor experiment. [Results] A protease producing strain H-16 was isolated from selective medium and identified as Escherichia marmotae by physiological-biochemical experiments and 16S rDNA sequence analysis. Strain H-16 could produce a protease with molecular weight of about 70 kDa. Tryptone, sucrose, 30℃ or 35℃, and pH 7 were the optimum nitrogen source, carbon source, temperature, and pH, respectively, for the growth of strain H-16. The protease produced by strain H-16 exhibited optimum activity for casein between pH 6 and 8, and it did not lose much enzyme activity under the conditions of below 50℃ and less than 6% salinity. In addition, Cu(II), Ag(I), and other metal ions could inhibit the activity of the protease. [Conclusion] Strain H-16 could be a good candidate for protease production.

Key words:protease;strain screening;molecular identification;enzymatic properties