Exploitable results
The project investigates both chemical and enzyme based methods of producing surface active materials (surfactants and emulsifiers) based on esterification of any of a number of different sugars with any of a number of different long chain fatty acids. Some such products, such as sucrose esters, are available commercially, finding use in cosmetics and foods. However, in general they are relatively costly due to difficulties in production and purification. These compounds consist of the combination of a sugar molecule, which is water soluble, with a long chain fatty acid which is soluble in organic solvents. The problem is to identify solvents in which both components will dissolve and then react as required. Such reactions may require the production of complex intermediates and reaction sequences. A number of the solvents which can be used are potentially harmful and have to be removed from the products. An alternative is to use enzymes which catalyse esterifications or transesterifications. However, again there is a need to find conditions under which the reactants will dissolve, the enzymes are stable and the products formed in sufficient quantities to be separated from the reaction mixture.
The products recovered were used in evaluation of the surface active properties. The structural analysis of products demonstrated that the enzymic synthesis of fructose monooleate led to a mixture of 4 isomers. In addition surface and interfacial tensions as well as the foaming and emulsifying powers were determined. Fructose monooleates caused a significant decrease in both surface and interfacial tensions, even at low concentrations. The critical micelle concentration of fructose monooleates was determined as 2.4E-4 This biosurfactant showed a high capacity to stabilize emulsions. In practice, 20% separation of phases were obtained with 0.1% fructose monooleates previously solubilized in xylene phase. In addition, on beating, this surfactant formed a foam which was very stable with time.
The project is investigating both chemical and enzyme based methods of producing surface active materials (surfactants and emulsifiers) based on esterification of any of a number of different sugars with any of a number of different long chain fatty acids. Some such products, such as sucrose esters, are available commercially, finding use in cosmetics and foods. However, in general they are relatively costly due to difficulties in production and purification. These compounds consist of the combination of a sugar molecule, which is water soluble, with a long chain fatty acid which is soluble in organic solvents. The problem is to identify solvents in which both components will dissolve and then react as required. Such reactions may require the production of complex intermediates and reaction sequences. A number of the solvents which can be used are potentially harmful and have to be removed from the products. An alternative is to use enzymes which catalyse esterifications or transesterifications. However, again there is a need to find conditions under which the reactants will dissolve, the enzymes are stable and the products formed in sufficient quantities to be separated from the reaction mixture. The study involves the following aspects:
the initial enzymic or chemical alkylation of the sugars;
the enzymic esterification of the saccharides with varying fatty acids and lipases, under different operational parameters;
the sugar esters purification by liquid and supercritical carbon dioxide extractions, precipitation and chromatography to achieve different degrees of purity;
the determination of the composition and surface properties of the synthesised sugar esters.
The knowledge gained on these processes will contribute to the development of economically competitive technologies and of novel surfactants for use as detergents or as additives for cosmetics, food and pharmaceuticals.
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