Non-denaturing process to purify recombinant proteins from plants

A method for production and purification of a soluble heterologous fusion protein comprising a cellulose binding module (CBM), from transgenic plants or transgenic plant cells expressing said fusion protein, comprising

• (a) disrupting the transgenic plant material;
• (b) adding an extraction liquid to the plant material, thereby creating a mixture of soluble and insoluble plant material, so as to extract the soluble fusion protein from said disrupted plant material to the liquid phase to obtain a protein extract;
• (c) separating the insoluble plant material, comprising cell-wall material and solids, from said protein extract comprising said fusion protein of interest;
• (d) contacting said protein extract to a polysaccharide matrix which binds to said fusion protein;
• (e) washing the matrix with the bound fusion protein with one or more suitable aqueous solutions;
• and
• (f) eluting the fusion protein from said polysaccharide matrix by adjusting conditions effecting the release of said fusion protein from the matrix,
• thereby obtaining the soluble heterologous fusion protein substantially purified.