Enzymatic degradation and deacetylation of native and acetylated starch-based extruded blends

Blends including natural starch and acetylated starch (with a substitution degree of 1.5) have been extruded to obtain an innovative packaging materia l. The influence of extrusion on the biodegradability of the blends was stu died for several acetylated-to-raw starch ratios, by colourimetry (measure of reducing sugars) and chromatographic analysis (determination of the amou nts of degradation products). The action of a single alpha -amylase (Termam yl LS 120 from Bacillus licheniformis) solely led to the degradation of unm odified parts of the starch. In order to increase the biodegradation rate o f starch, the hydrolysis of acetylated groups was performed thanks to vario us acetyleterases, one coming from Sigma and the other one originating from the viscozyme. These acetylesterases will be refered to as Sigma acetylest erase (Sac) and Viscozyme acetylesterase (Vac), respectively. For identical percentages of ethanoic acid released, it appears that the biodegradation obtained after action of the alpha -amylase is more pronounced when the Sig ma acetylesterase was utilized in a first step, because the biodegradation rate increased from 10 to 15%. The main degradation products are dp2 and dp 5. Thus, the present work presents the degradation behaviour of a new packa ging material, even at high acetylation value, provided the acetylesterase employed leads to a deacetylation compatible with the alpha -amylase. (C) 2 001 Elsevier Science Ltd. All rights reserved.