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