A Process for large‐scale isolation of β‐galactosidase from E. coli in an aqueous two‐phase system

A method suitable for large-scale isolation of beta-galactosidase from a suspension of disintegrated E. coli cells has been developed. In an aqueous two-phase system consisting of PEG 6000 and potassium phosphate, all cell debris and the major part of the proteins and nucleic acids were partitioned to the denser salt phase. Seventy-five percent of the beta-galactosidase was recovered in the lighter PEG phase, giving a purification ratio of about 12.