The first precipitation was
performed using ammonium sulfate while sodium chloride
was used for the second precipitation step. As shown in
Table 1, increase in protein concentration used during each
precipitation step resulted in an increase in the amount of
protease activity (including papain) recovered in the precipitate,
but a lower purity of papain. This may be explained by
enhanced protein aggregation caused by increase in number of interactions between the surface hydrophobic groups as the
protein concentration is increased. A maximum of about 39%
of the protease activity present in the latex was precipitated
with ammonium sulfate at an initial protein concentration of
40 mg/ml. The second precipitation step provided significantly
lower recovery of protease activity but with a relatively enriched
papain fraction. The maximum purity of papain (>89%) was
achieved by limiting the protein concentration during the
second precipitation to 6 mg/ml (Table 1).