Invertase was immobilized on aminopropyl silica (APTS-SiO2) activated with
humic substances (APTS-SiO2-HS) and on aminopropyl silica activated with gl
utaraldehyde (APTS-SiO2-GA). The resulting activity of both systems was com
pared Humic substances (HS) used for the activation of the silica were extr
acted from soil of Cananeia, Sao Paulo State, Brazil, according to the proc
edure recommended by the international Humic Substances Society. Activity w
as determined by measuring the rate of formation of reduced sugars using th
e reaction with dinitrosalicylic acid (DNS). The amount of HS bound on the
APTS-SiO2 was equal to 50 mg. The maximum amount of invertase immobilized o
n APTS-SiO2-HS was 15200 U/g while in the system APTS-SiO2-GA it was 13400
U/g. The experimental enzymatic activity was 3700 and 3300 U/g, for the sys
tems APTS-SiO2-HS and APTS-SiO2-GA, respectively. Considering the increased
amount and activity of immobilized enzyme compared with the glutaraldehyde
method, it was concluded that this technique opens a new perspective in th
e preparation of supports for enzyme immobilization employing humic substan
ces.