Encapsulation of α-amylase into starch-based biomaterials: An enzymatic approach to tailor their degradation rate

This paper reports the effect of α-amylase encapsulation on the degradation rate of a starch-based biomaterial. The encapsulation method consisted in mixing a thermostable α-amylase with a blend of corn starch and polycaprolactone (SPCL), which were processed by compression moulding to produce circular disks. The presence of water was avoided to keep the water activity low and consequently to minimize the enzyme activity during the encapsulation process. No degradation of the starch matrix occurred during processing and storage (the encapsulated enzyme remained inactive due to the absence of water), since no significant amount of reducing sugars was detected in solution. After the encapsulation process, the released enzyme activity from the SPCL disks after 28 days was found to be 40% comparatively to the free enzyme (unprocessed). Degradation studies on SPCL disks, with α-amylase encapsulated or free in solution, showed no significant differences on the degradation behaviour between both conditions. This indicates that α-amylase enzyme was successfully encapsulated with almost full retention of its enzymatic activity and the encapsulation of α-amylase clearly accelerates the degradation rate of the SPCL disks, when compared with the enzyme-free disks. The results obtained in this work show that degradation kinetics of the starch polymer can be controlled by the amount of encapsulated α-amylase into the matrix.