Aqueous two-phase systems (ATPS), m

Aqueous two-phase systems (ATPS), made up of two polymers
or one polymer and a salt in water, have shown interesting
potential for downstream processing of proteins, especially in
view of providing integrated clarification, concentration and
purification of the target product in one unit operation [11]. They
have been successfully applied for large-scale enzyme separation
and purification [12–14]. A desired partition of proteins
in such systems can be obtained by manipulating a variety of
system parameters [15,16]. The polymer–salt–water systems
have the advantage of low cost and low viscosity compared
to polymer–polymer–water systems. The most frequently used
among the former systems has been the polyethylene glycol
(PEG)–phosphate [13,17], however other salts with multivalent
anions have also been used [18]. Use of PEG–phosphate system
has earlier been reported for separation and purification of papain
from papaya latex [19]. The study showed that the separation of
papain was negatively affected by the presence of chymopapain,
however the use of PEG modified with Procion Blue enhanced
the partition of papain to the PEG rich upper phase.
This paper reports the use of ATPS composed of PEG and
ammonium sulfate for purification of papain from C. papaya
latex and compares it with the conventional method based on
precipitation.