STUDY OF THE INHIBITION EFFECT ON THE MICROENCAPSULATED ENZYME b-GALACTOSIDASE

Abstract

The aim of this work is to investigate the influence of an inhibitor over free and microencapsulated enzymes. Microencapsulation is one of the techniques for enzyme immobilization, which is a very common process in the industry to stabilize enzymes and to increase the time and the range of applicability. There are several microencapsulation techniques, with different adaptations and specificities. In this work we used a spray drying method which is a technology used in industry due to its low cost, availability of equipment and efficiency. Spray drying is also a clean technology because it avoids the use of organic solvents during the encapsulation process. This study focused on the enzyme β-galactosidase, due to its importance in health and industry. Chitosan was selected as encapsulating agent considering all the advantages of this natural polymer. The microcapsules were prepared by spray drying and characterized by their particle size and surface morphology. Structural analysis of the surface of the particles was performed by Scanning Electron Microscopy (SEM). The SEM results show that the obtained microcapsules have a diameter smaller than 5 μm and a regular shape. The activity of the enzyme was studied by a spectrophotometric method using the substrate ONPG (O-Nitrophenyl-β,Dgalactopyranoside) and MGP (methyl-β,D-galactopyranosidase) as an inhibitor. It was concluded that there are differences on β-galactosidase activity in the presence of the inhibitor. The results also showed that the use of an encapsulating agent increases the diffusional effect of the released enzyme, and also reduces the initial activity of the enzyme.

Effect of the pH in the formation of β-galactosidase microparticles produced by a spray-drying process

“…The parameter Vmax, representing the maximum reaction rate at a given enzyme concentration, decreased its value after microencapsulation process thus confirming what has been observed by other authors [26,33]. Some active centres are likely to be blocked after microencapsulation, which reduces the reaction rate, causing the decrease of the maximum reaction velocity.…”

“…Comparing the results obtained in this study with the previous ones [23,24,26], we can conclude that the selection of the pH for the immobilization (microencapsulation) of the enzyme is so important as the selection of the encapsulating agent or the selection of the operational conditions of the spray dryer for the optimization of the β-galactosidase activity.…”

“…The highest value of the Vmax was obtained from the microencapsulated β-galactosidase formulation obtained at pH 6, being more than four times higher than the Vmax obtained from the formulations produced with different pH ( Figure 5). However, this value is smaller than the Vmax obtained with the free enzyme [26].…”

“…The spray drying methodology and the operation conditions were optimized based on preliminary studies [23,24,26]. The product yield (quantity of powder recovered reported to the quantity of raw materials) was in average 30%.…”

“…The Michaelis-Menten parameters were determined for the microencapsulated formulations with different pH and are presented in Table 1. The values related to the free enzyme have already been determined by the authors [26].…”