I'd suggest PVP or PVPP

http://en.wikipedia.org/wiki/Polyvinylpyrrolidone

http://en.wikipedia.org/wiki/Polyvinylpolypyrrolidone

but I'm not sure whether are they used also for protein purification.

Dear Vincent

Protein content of microalgal biomass is assessed either by

(i) colorimetric methods (sensitive to interference), or

(ii) by methods that measure the concentration of elemental nitrogen in biomass (sensitive to interference).

The cells are to be conditioned (involving bursting of cells, physically or chemically) so that it fully releases intracellular proteins, prior to assessment. Hydrolytic enzymes and chemicals like SDS can be used. Milling a cell slurry with glass beads, exposure to ultrasonic frequencies etc. could be effective as well.

Following references may be of some help to you

1. Barbarino, E., Lourenço, S.O., 2005. An evaluation of methods for extraction and

quantification of protein from marine macro- and microalgae. J. Appl. Phycol. 17, 447–460.

2. Meijer, E.A., Wijffels, R.H., 1998. Development of a fast, reproducible and effective

method for the extraction and quantification of proteins of micro-algae. Biotechnol. Tech. 12, 353–358.

3. Chisti, Y., Moo-Young, M., 1986. Disruption of microbial cells for intracellular products. Enzyme Microb. Technol. 8, 194–204.

Best

Dola

Another one:

http://cdn.intechopen.com/pdfs/28765/InTech-Protein_purification.pdf