Kinetic Study of Lactose Hydrolysis by Aspergillus oryzae Beta-galactosidase immobilized in Sodium Alginate
Special Symposium - Innovations in Food Technology (LMC Congress)
Innovations in Food Technology - Poster Session (LMC/Food - P1)
Keywords: -galactosidase, immobilization, optimization, sodium alginate
The milk is a complex, nutritious and stable mixture of fat, proteins, lactose, vitamins and other components that are found in suspension on water. The lactose causes intolerance to a great parcel of the human population, also being a low soluble sugar, turning the milk into a difficult raw material to use in concentrated and frozen products. To minimize such problems, an adequate solution is the lactose hydrolysis through the -galactosidase enzyme. An alternative for industries using enzymatic processes is using the enzyme in its immobilized form, as costs can be reduced when compared with the use of the soluble enzyme and the process operation can be optimized with a good immobilization technology. In this work a study regarding the immobilization process optimization of the - galactosidase enzyme from Aspergillus oryzae by entrapment in sodium alginate gel and gelatin cross-linked with glutaraldehyde was achieved. The optimal concentrations of sodium alginate (6.6% w/v), gelatin (4.05% w/v) and glutaraldehyde (3.64% w/v) in the immobilization process were determined through a Central Composite Design (CCD), having as an answer the immobilized enzyme activity. After being used 30 times, the obtained immobilized enzyme showed a reduction of only 20% in its enzymatic activity, thus suggesting that the used immobilization process implied in a considerably stable biocatalyst when compared with similar immobilization processes for this enzyme. A study of the combined influence of the pH and the temperature was carried out by using a Central Composite Design (CCD) and the optimal results for the enzymatic activity were a pH of 5 and a temperature of 60ºC. The lactose hydrolysis by immobilized -galactosidase results were adjusted to the substratum inhibition and galactose competitive inhibition models. The immobilized enzyme was fairly stable in a pH ranging from 4 to 8 and possessed a half-life time of approximately 630 minutes in a temperature of 53ºC.
