Biocatalisadores sintetizados a partir de β-galactosidase de Kluyveromyces lactis imobilizada em suportes revestidos com polietilenimina (PEI) e sua aplicação na síntese de prebióticos

Abstract

Lactose intolerance affects thousands of people nowadays, and the increase in the incidence of cases of intolerance has awakened the interest of the food industries to develop free lactose products. Thus, the use of immobilized enzymes to obtain these products is an attractive alternative from an industrial point of view, mainly due to the possibility of their reuse. β-galactosidases are able to catalyze these reactions. In addition to hydrolyzing lactose, these enzymes are also responsible for producing sugars with prebiotic function, such as lactulose, a prebiotic widely used for the treatment of chronic constipation and hepatic encephalopathy. Enzymatic prebiotics production, when compared to chemical production currently used by industries, has certain advantages such as high specificity and selectivity of enzymes to the substrate, besides being biodegradable, which makes this process greener. Besides, enzyme-catalyzed reactions are generally conducted under mild conditions, thus minimizing product degradation and reducing process energy expenditure. Immobilization strategies using multi-functional polymer coated supports have certain advantages, such as promoting greater enzymatic stabilization, especially of multimeric enzymes, such as β-galactosidases, as well as extending the life of biocatalysts and protecting them against environmental variations. Moreover, these strategies can substantially improve the immobilization parameters and, consequently, the efficiency of enzymatic processes. Therefore, the aim of this work was to evaluate the use of chitosan-glutaraldehyde and glyoxyl-agarose supports uncoated and coated with polyethylenimine (PEI) to immobilize β-galactosidase from Kluyveromyces lactis and apply the obtained biocatalysts in the hydrolysis of lactose and synthesis of prebiotics, using whey as feedstock. PEI-coated agarose supports performed better to immobilize β-galactosidase. Besides that, these biocatalysts were efficient in the hydrolysis of lactose and prebiotic production, achieving over 90% lactose conversion and maximum lactulose production of 7.02 ± 0, 02 g/L and 11.31 ± 1.60 g/L for the Qui_Glu_PEI_Gal and Aga_Gli_PEI_Gal biocatalysts, respectively. However, biocatalysts obtained using PEI-coated supports showed lower thermal stability at 50 °C and low operational stability, a fact explained by the interaction between the enzyme and the support being of the adsorption type. The lactulose synthesis using whey as feedstock was very effective, reaching a maximum lactulose production of 7.60 ± 0.4 g/L for the biocatalyst Qui_Glu_PEI_Gal and 13.90 ± 0.96 g/L for the Aga_Gli_PEI_Gal biocatalyst, proving to be an industrially promising alternative for the production of prebiotics and ecologically sustainable because it reduces the environmental impact caused by the direct disposal of this waste in the environment.