Imobilização de α-amilase em fibras de álcool polivinílico via electrospinning e sua atividade em diferentes substratos

Abstract

α-amylase is an enzyme widely used in the food industry, however, there are some factors that may affect its efficiency and stability and immobilization arises as an alternative. Electrospinning is emerging as a promising technology for the immobilization of enzymes where various polymers can be used. Polyvinyl alcohol (PVA) has good characteristics for use as a support in the immobilization of enzymes, since it has good fiber production capacity by electrospinning, it is biodegradable, biocompatible, among others. However, fibers made with PVA have low thermal stability. In order to increase its thermal stability, the use of a crosslinking agent, such as glutaraldehyde in the vapor phase, has been suggested. The aim of the study was to immobilize α-amylase in PVA fibers by electrospinning and apply it to substrates of corn starch, germinated wheat and ungerminated wheat. To that end, solutions of 8% (w / v) PVA were added α-amylase at concentrations of 1, 1.5 and 2% (w / v) and produced ultrafine fibers via electrospinning. The fibers were evaluated for morphology and size distribution, functional groups and chain, enzymatic activity, loading capacity and stability at different temperatures and pH's. In another step, glutaraldehyde cross-linking was carried out at 1, 2, 3 and 4 hours of exposure using the fibers with 1.5% α-amylase. After the crosslinking the fibers were evaluated for morphology, enzymatic activity and thermogravimetric analysis. The results showed that the incorporation of enzyme caused a slight change in the morphology of the fibers, presenting fibers more flattened and thicker with the increase of the enzyme concentration. The mean diameters ranged from 187 to 282 nm. FTIR spectra indicated that the enzyme was incorporated into the fibers. PVA exhibited high loading capacity for α-amylase at all concentrations tested, showing good support for immobilization of enzymes. Enzymatic immobilization improved α-amylase stability over a wide temperature range and pH. The germinated wheat starch presented higher value of enzymatic activity, at different temperatures and pH's, presenting a great potential for application in α-amylase hydrolysis. After the crosslinking, the fiber morphology presented a denser and more compact structure between the fibers, resulting from the chemical interaction of glutaraldehyde with PVA and α-amylase. A decrease in enzyme activity was also observed after different exposure times to glutaraldehyde vapor. The TGA analysis showed an increase in the initial decomposition temperature for the fibers, demonstrating a higher thermal stability of the crosslinked fibers. From the results obtained it is possible to conclude that the membranes of immobilized α-amylase PVA presented good characteristics for use in the hydrolysis of starch from different sources.