Aerobic Biodegradation of Acetylated Starch

Some acetylated starch samples with degrees of substitution varying from 0.03 to 1.6 are submitted to aerobic degradation by Bacillus amyloliquefaciens. The degradation is expressed by the concentration of reducing sugars evolved from the substrate, by the amylolytic activity and by the assessment of the CO₂ release resulting from the mineralization of the acetylated starch. With formation of exclusively glucose and maltose as control substrates, the hydrolysis is complete. For the samples with a low acetylation degree, the hydrolysis is slowed down as a result of inhibition by the acetyl groups. When the degree of acetylation is high, it becomes necessary to add inducers of acetylesterase activity. So, for acetylated starch with a degree of substitution of 1.6, the mineralization percentage increases up to 30% upon addition of isopropyl-β-D -thiogalactopyranoside.