Recycling of phase components during lysozyme extraction from hen egg white in the EO50PO50/K2HPO4 aqueous two-phase system

An aqueous two-phase system (ATPS) composed of a thermoseparating copolymer EO50PO50 [50% (w/w) ethylene oxide and 50% (w/w) propylene oxide] and K2HPO4 was used to extract lysozyme from hen egg white over four successive extractions, using the recovery and recycling of phase components. Extraction was performed in two stages. In the first stage the primary two-phase system of 40% EO50PO50/10% K2HPO4 (w/w) was formed and the lysozyme partitioned to the top copolymer-rich phase while the contaminant proteins remained in the bottom phosphate-rich phase. In the next stage the copolymer-rich phase was isolated and subjected to temperature-induced phase separation. The resultant secondary two-phase system was composed of a concentrated solution of copolymer and a water solution of lysozyme. Next, the concentrated solution of EO50PO50 recovered after thermoseparation was mixed with the phosphate solution recovered from the primary system and a new portion of hen egg white added to obtain a new lysozyme extraction system. The specific activity of lysozyme preparations obtained during the four successive extractions ranged from 38,438 to 42,907 U/mg of protein.