Stirred tank reactor and method

A method for purifying a biomolecule selected from the group consisting of proteins and antibodies, from a mixture containing impurities selected from the group consisting of cells, cell debris, host cell proteins and DNA, comprising:

• a. providing an assembly comprising providing a first container having an interior space, a first base sealingly affixed to said first container and supporting at least one membrane sealed to said first base for filtering said mixture;
• an outlet in said base, a second container in fluid communication with the outlet of said first base, and a second base sealingly affixed to said second container, said second base comprising a second membrane and a supporting surface comprising grooves for fluid flow;
• b. providing the mixture at a set of conditions,
• c. adding one or more polymers, soluble in said mixture under the set of conditions and capable of reversibly and selectively binding to the biomolecule, said one or more polymers selected from the group consisting of poly(N-vinyl caprolactam), poly(N-acryloylpiperidine), poly(N-vinylisobutyramide), poly(N-isopropylacrylamide), poly(N,N′-diethylacrylamide), poly(N-acryloyl-N-alkylpiperazine), hydroxyalkylcellulose, copolymers of acrylic acid and methacrylic acid, and polymers and copolymers of 2 or 4-vinylpyridine and chitosan with either a ligand or functional group attached to it,
• d. mixing the one or more solubilized polymers throughout the mixture;
• e. precipitating the one or more polymers and bound biomolecule out of solution by changing the set of conditions in the mixture;
• f. washing said precipitate by contacting said precipitate with a wash solution and filtering the supernatant through said first membrane, and
• g. recovering the bound biomolecule from the polymer and filtering the biomolecule through said second membrane.