To compensate for the loss of enzymatic activity of bromelain
after the lyophilization process, some cryoprotectors were used
in order to decrease the tension force generated by the ice crystals on the bromelain. The best cryoprotector for bromelain was observed
for 10% (w/v) glucose in a phosphate buffer of pH 7.0, which
allowed for a 90.3% recovery of initial activity. The efficiency of the
process was confirmed in the native-PAGE shown in Fig. 1D, in
which the presence of white bands is related to the maintenance
of activity after lyophilization. It was also possible to recover about
61.0% of the enzymatic activity of bromelain in the presence of 10% sucrose (w/v) in a phosphate buffer of pH 7.0. Sugars, mainly
monosaccharides and some disaccharides, are considered good
cryoprotectors because they act by reducing the water that can
be frozen on the surface of protein molecules, helping to reduce injury
caused by water crystallization [39].