Most proteins require some kind of buffer and it would be rare to find a protein that is happy is pure water without any salt. It might be good to check with the manufacturer on their recommended method. Aggregates may be eliminated with filtration or centrifugation - at the risk of loss of material. Try different buffers, and potentially test for presence of aggregates with dynamic light scattering, if available to you.

I agree with the comments given by Ulf. You need to identify solution conditions that maintain your protein in its soluble and stable forms. Bufer pH, ionic strength, presence of solublizing and stabilizing additives are some of the most critical parameters.

Here is the paper on lipase for you to grasp some idea.

Article Increased enantioselectivity of lipase in the transesterific...

Dear Farhen Naz

I agree with the solutions provides by Mr. Ulf and Alemu. I used to dissolve lipases in buffer tris pH7 or phosphate (1M). The limit of ionic strength that I have been used was 50mM NaCl.

However, I also recommend you, use UV spectra at a concentration of 30uM or less, because there are fluorescence and UV spectra evidence that aggregation happened at this point.

If you can, It is possible measured diluted solutions that provide the information that you require.