Lipase-catalysed acylation of starch and determination of the degree of substitution by methanolysis and GC
1 WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Thomas Graham Building, 295 Cathedral Street, Glasgow, G1 1XL, UK
2 BASF-AG, Fine Chemicals and Biocatalysis Research, 67056, Ludwigshafen, Germany
3 School of Chemistry, Manchester Interdisciplinary Biocentre, 131 Princess Street, Manchester, M1 7DN, UK
BMC Biotechnology 2010, 10:82 doi:10.1186/1472-6750-10-82Published: 29 November 2010
Natural polysaccharides such as starch are becoming increasingly interesting as renewable starting materials for the synthesis of biodegradable polymers using chemical or enzymatic methods. Given the complexity of polysaccharides, the analysis of reaction products is challenging.
Esterification of starch with fatty acids has traditionally been monitored by saponification and back-titration, but in our experience this method is unreliable. Here we report a novel GC-based method for the fast and reliable quantitative determination of esterification. The method was used to monitor the enzymatic esterification of different starches with decanoic acid, using lipase from Thermomyces lanuginosus. The reaction showed a pronounced optimal water content of 1.25 mL per g starch, where a degree of substitution (DS) of 0.018 was obtained. Incomplete gelatinization probably accounts for lower conversion with less water.
Lipase-catalysed esterification of starch is feasible in aqueous gel systems, but attention to analytical methods is important to obtain correct DS values.