Pilot-scale extraction of an intracellular recombinant cutinase from E. coli cell homogenate using a thermoseparating aqueous two-phase system

A thermoseparating aqueous two-phase system for extraction of a recombinant cutinase fusion protein from Escherichia coli homogenate has been scaled up to pilot scale. The target protein ZZ-cutinase-(WP)(4) was produced in a fed batch process at 500 l to a concentration of 12% of the total protein and at a cell concentration of 19.7 g l(-1). After harvest and high-pressure homogenisation a first extraction step was performed in an EO(50)PO(50) (50% (w/w) ethylene oxide and 50% (w/w) propylene oxide) thermopolymer/amylopectin rich Waxy barley starch system. The (WP)(4) tag was used for enhanced target protein partitioning to the EO(50)PO(50) phase while the cell debris was collected in the starch phase. A second extraction step followed where the recovered EO(50)PO(50) phase from the first step was supplemented with a non-ionic detergent (C(12-18)EO(5)) and heated to the cloud point (CP) temperature (45 degrees C). One polymer-rich liquid phase and one almost pure aqueous phase were formed. The target protein could be obtained in a water phase after the thermal phase separation at a total recovery over the extraction steps of 71% and a purification factor of 2.5. We were able to demonstrate that a disk-stack centrifugal separator could be adapted for rapid separation of both primary and thermoseparated phase systems.