Low power microwave‐assisted enzymatic esterification of starch

Abstract

AbstractA series of starch esters was obtained using microwave‐assisted enzymatic transformation of starch. For the reaction hog pancreas lipase was used as a biocatalyst as well as followed acyl donors: acetic, lauric, and stearic acid. DMF and DMSO were applied as a reaction media. Experiments focused on low level microwave irradiation were compared with conventional heating of the reaction mixture. The structure of obtained starch esters was investigated by means of FTIR, analysis of substitution degree, changes in molecular parameters (MWs and MWs distributions), and microscopic studies (SEM). The spectroscopic analysis confirmed the ester bond formation. The microwave‐assisted reaction in DMF and lauric acid as an acyl donor, gave the highest degree of substitution (0.513) what followed the lowest polysaccharide degradation and maintaining the granular structure of starch. According to all the results the significant shortening in the reaction time (about 2.5 times) for microwave‐assisted reactions were observed. The influence of microwaves on esterification of starch was discussed focusing on reaction media and acyl donor type. The investigated reaction systems were demonstrated as new protocols for obtaining starch ester with higher efficiency in comparison to those known as conventional. Replacement of sophisticated derivatives including vinyl esters or acyl chlorides by simple acyl donors were shown as an additional benefit of proposed starch esterification method.