I have powdered cellulase from aspergillus niger (sigma cat: C1184-5KU). How do I make a stock solution of this enzyme, and what is the best temperature for long term storage of the stock solution?
Have you examined the possibility of using ionic liquids to dissolve and store. This is a suggestion to explore and not a ready solution to the problem.
We all ways dissolve in MES buffer (pH 5 or 5.5) pre-cooled at 4 degree Celsius. Pl see the literature for preparation of MES buffer. The entire solution then is centrifuged at 10,000 RPM at 4 degree for about 30 min. The clear supernatant is dispensed in vials and stored at -20 degree Celsius. The enzyme is very stable at lower temperatures and can be used even after one year storage at such conditions.
You can prepare the stock solution of cellulase in either citrate buffer or acetate buffer (pH range 4.5-5.5) and store it at 4 degree Celsius in cold room. This can easily serve your purpose for 6 months. For further stabilization you can add KCl or glycerol to increase its shelf life (Upto 1-3 years) as normally these are the ingredients used by Industries to stabilize enzyme samples.
You can prepare a solution 20% in water pre-filtered (0.45um+0.8+1.2) then filtered on 0.22um in laminar flow and store at 4°C. It's easily and long term storage.