This publication details the isolation of proteins from biological materials, techniques for solid-liquid separation, concentration, crystallization, chromatography, scale-up, process monitoring, and product formulation, and regulatory and commercial considerations in protein production. The authors discuss release of protein from biological host, selectivity in affinity chromatography, precipitation of proteins (both non-specific and specific), extraction for rapid protein isolation, adsorption as an initial step for the capture of proteins, scale up and commercial production of recombinant proteins, and process monitoring in downstream processing.