The Isolation and Identification of Deep-sea Bacteria That Produce Salt-tolerant Proteases

This study was aimed at screening deep-sea bacteria that produce salt-tolerant proteases from deep-sea mud samples based onhigh-salt accumulation, fermentation rescreening, and salt-tolerant stability tests. Twenty-five strains of deep-sea marine microorganisms were selected, 14 of which demonstrated an increase inhydrolysis cycles on casein plates. A strain withhigh enzyme activity and salt stability was obtained based on fermentation rescreening and a salt-tolerance test, and was labeled as SWJSS3. Strain SWJSS3 was identified using 16S rDNA and a preliminary study on the effects of salt concentration on its protease yield and stability was conducted. The strain was able to grow in medium with salt concentrations between 0% and 10% and an OD600 of the bacterial suspension ranging from 0.08 to 1.98. The activity of proteases produced by SWJSS3 was maximal for a 1% salt concentration in the fermentation rescreening(233.56 ± 2U/mL). After treatment with 15%(final concentration) sodium chloride solution at 4 ℃ for 1h, the enzyme activity decreased to 40.70 ± 2.06% of the initial enzyme activity, but remained stable for up to 9h. strain SWJSS3 was identified as Pseudomonas aeruginosa, exhibiting 99% 16S rDNA sequence similarity to P. aeruginosa RP28.