A new application of humic substances: activation of supports for invertase immobilization

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.