(463h) Kinetic Study of Galacto-Oligosacharides Production From Lactose and Whey Using Immobilized ?-Galactosidase

Kinetic study of Galacto-Oligosacharides Production from Lactose and Whey
using immobilized b-Galactosidase

 Guio, Felipe* ¹, Serrato, Juan ¹, Sánchez, Óscar ¹

1.       Department of Chemical Engineering, School of Engineering, Universidad Nacional de Colombia, Bogota, Colombia.

* Corresponding author

Galacto-oligosaccharides (GOS) are prebiotics used in functional food formulations.  GOS are produced during lactose hydrolysis by b-galactosidase. In this study GOS production was evaluated using lactose and dry whey with Lactozym 6500 L free and immobilized. The synthesis was performed at 30, 40 and 50°C, pH 5.5, 6.0 and 6.5, lactose concentration 300, 400 and 500 g L^-1 and enzyme concentration 1.5, 3 and 4.5 U ml^-1. B-galactoside was immobilized by entrapment in calcium alginate and covalent adsorption in silica gel 60.  Both immobilized enzymes were characterized with ONPG before GOS production to determine activity retention. The obtained GOS yield for free enzyme was 32.7% and 24.5% using lactose and dry whey, respectively. Immobilization on silica gel 60 showed enzyme activity retention of 41.8%, compared with entrapment technique with only 18.4%. GOS yield with immobilized enzyme on silica gel 60 was 22.9% using lactose and 11.2% with dry whey as substrate.  Two kinetic models for GOS production were proposed to experimental data adjustment for free and immobilized enzyme on silica gel 60. They were based on a reaction mechanism described by elementary equations (engineering approach) and Michaelis-Menten kinetic equations (classical approach). The model based on an engineering approach adjusted experimental profiles with an overall average percentage error of 13.74 and 16.85, using lactose and whey in GOS production with immobilized enzyme, respectively. This immobilization technique and kinetic study could be studied in a continuous GOS production system using the same enzyme several times.