You must specify the source of the enzyme.

I saw this article describing a highly salt tolerant alkaline protease.

http://link.springer.com/article/10.1007/BF02916414#page-1

It seems that the activity is about the same from 0 to 5M NaCl.

Most of the enzymes can work at low salinity. Even in you desalt your enzyme and activity decrease, you can measure different NaCl concentration in order to get the optimum concentration for activity.

HNS

Thanks Adam B Shapiro and Hector Nolasco!

This enzyme is produced from  Bacillus licheniformis and Bacillus amyloliquefaciens.Cause I dont want to have a lot of NaCl in final hydrolysate solution, so I would like to desalt NaCl as much as posible at the beginning.  I hope that enzyme can work well at 0M NaCl? Hector Nolasco, you said "most of the enzymes can work at low salinity", could you tell me what do you mean "low salinity"?.

By the way, could you tell me why commercial enzyme is stored in such concentrated NaCl upto 90% (w/w), NaCl is used to stablize enzyme?

Best regards!

Low NaCl concentration is close to 0.15 M, a physiological concentration in animals. Also used in PBS buffer, for instance.

Yes some commercial enzyme preparation are stored in high salt concentation (4 M ammonium sulphate, for instance) to increase stability during storage.

HNS

I don't think it is possible to have a solution of 90% (w/v) of NaCl in cold or room temperature water. The solubility is 36% at room temp, about 6M. The enzyme may be stored this way because it is stable, but such a high salt concentration discourages growth of microorganisms in the solution.

Xuannam Truong please check Concentration. Is it 0.9 % NaCl? that is 0.15 M NaCl.

Dear Adam B Shapiro and Hector Nolasco!

Thanks for your interest in my question. The product is in solid form, not solution, containing 90% NaCl, 7% - enzyme, and 3% of humidity, totally 100%. This concentration is indicated in the product data sheet.  So the data is correct. The product has a brown color. Is it the color of protease or some additional excipients?

I've just conduct the dialysis to remove NaCl out of protease today, and observed that NaCl is effectively removed, proved by decrease of electrical conductivity of removed solution. By the way, for the first some cycles of dialysis, the removed solution  has a light brown color, then, pure white color, while the concentrated solution containing protease still have brown color.  So what make the removed solution has this light brown color?  I dont beleive that the protease enzyme get through the pore of the dialysis membrane (5 kDa), because, as i suppose, the size of protease is much bigger, is about 28kDa. So could you tell me where the light brown come from?

Looking forward to hearing from you soon. 

The enzyme is probably not highly purified but is a partially purified or crude extract. The brown color is the remains of the bacterial extract, containing a wide variety of substances. The protease itself is probably colorless. Some of the brown material is low molecular weight and passes through the dialysis membrane, whereas some is high molecular weight and stays with the enzyme. Colored substances in the bacteria would include flavin cofactors, heme-containing proteins, and secondary metabolites particular to the species.

Adam is correct. After dialisys you can run a gel filtration chromatography, and it is possible that coloured material could be separated from your enzyme. In the same proceses you can use the proper buffer for your enzyme activity and stability.

HNS

Thank you to both of you, especially,  Adam B Shapiro, for your clear explanation. I was curious about the colour of the enzyme, wanted to know why, and  I'm satisfied with your answer. Now I have a better knowledge about the components of commercial enzyme.

To Hector Nolasco: I do not have the gel filtration chromatography, first of all, I would like to apply this method to remove NaCl, but finally chose dialysis (for me it's easier and simpler). It's not necessary for me to get the absolutely purified protease, I just want to remove NaCl out of it. If the protease still work well after removing NaCl, so, it is good for me.

Best regards!