Enzymatic Esterification of Carbohydrates with Fatty Acids Derived from Vernonia Galamensis

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Date

2011-06

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Addis Ababa Universty

Abstract

Sugar fatty acid esters (SFAEs) are compounds produced from renewable and inexpensive substances such as natural oils and glucose or starch. SFAEs are normally non-ionic, non-toxic, non-irritants, odorless, tasteless and biodegradable. Due to these range of properties, these compounds have found applications as diverse as surfactants in the food and cosmetic industries, as insecticides and antimicrobial agents, in stabilizing and detergency or conditioning effects and even as non-caloric fat substitutes. Changing the nature of the starting materials such as using oils with special functional groups has the potential to provide with value-added products and highly versatile materials with interesting characteristics. Vernonia galamensis is a plant, endemic to Ethiopia, containing a very promising naturally epoxidized oil presenting also low toxicity and inherent biodegradability. The synthesis of sugar fatty acid esters based on vernolic fatty acids could provide with products with the potential to be used as a new type of epoxidized surfactants or as starting materials for a variety of value added products. The chemical synthesis of monosubstituted starch/glucose esters is very difficult to achieve due to the poor selectivity of this approach. Enzymatic processes are an excellent alternative due to the high selectivity of the reaction owing to their exquisite stereo-selectivity, regio-selectivity and functional group specificity. In this work, the synthesis of starch/glucose vernolates has been attempted from vernolic acid and methyl vernolate by enzymatic (candida antarctica lipase B) esterification in the ionic liquid [Bmim][TfO]. The use of ionic liquid avoids the use of environmentally unfriendly volatile organic liquids. The low vapour pressure exhibit by ionic liquids avoids the use of molecular sieves as the water produced in the reaction can be continuously extracted under vacuum. The synthetic procedure also includes the use of water mediated supersaturated solutions that allowed us to increase the concentration of glucose in the ionic liquid media. Moreover, the activity of the enzyme was found to be enhanced by the ionic liquid used. The products were characterized by melting point and 1H and 13C NMR spectroscopy and the degree of substitution of the glucose ester was investigated and found to be 2.17. Key words: ionic liquids, [Bmim][TfO], vernonia oil, vernolic acid, methyl vernolate, candida antarctica lipase B, fatty acid esters, glucose esters, starch esters

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Ionic liquids; [Bmim][TfO]; vernonia oil; vernolic acid;methyl vernolate; candida antarctica lipase B; fatty acid esters; glucose esters; starch esters

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