3. Results and discussion
3.1. Selection of the immobilization support
Derivatives were prepared using high activated supports with
the objective of achieving an intense multipoint covalent attachment
or an intense adsorption [10,15]. Through titration of
the remaining sodium periodate, an activation degree of 106
micromoles of glyoxyl groups mL−1 packed agarose beads was
determined. Therefore, we can assume that each enzyme molecule
has many reactive groups under its surface after immobilization.
If the enzyme interacts with the supports through many points,
enzyme stability by their three-dimensional structure “rigidification”
may be obtained [10,31].
The beta-amylase immobilization was performed by using
glyoxyl, MANAE and glutaraldehyde-agarose supports under the
conditions described in methods. Different protein:support ratios
were tested for each support (data not shown). The expressed
activity gradually increased whilst 100% immobilization was maintained;
with the highest possible loads being obtained using
MANAE and glutaraldehyde supports (Table 1). Using the glyoxylagarose
support, it was not possible to achieve high percentages
of immobilization, even using the lowest protein loading. This low
loading using glyoxyl supports could be due to the lack of a region
bearing many exposed Lys residues able to react with the enzyme