Guar is a galactomannan derived from the seed of the guar plant. It is extensively used in food and industrial applications as a thickener, sizing agent, flocculent, and gelling agent. Since guar is a neutral polysaccharide, sometimes it is desirable to convert it to an anionic polymer. This can be done via the reaction of guar with succinic anhydride in the presence of a suitable lipase (Scheme 2).
Previously, acid anhydrides such as succinic anhydride [17,18] and acetic anhydride  were used for enzymatic acylation of small organic compounds or monosaccharides via lipases, but not much has been published on polysaccharides. Three enzymes, lipase from Pseudomonas sp. (lipase AK, Amano), lipase from Candida cylindracea (Sigma), and lipase OF-360 (Meito-Sangyo Ltd.), have been studied for this acylating reaction. Among the three enzymes, lipase AK showed the highest catalytic activity and Candida cylindracea lipase the lowest activity. Interestingly, the succinated guar shows somewhat enhanced viscosity relative to that of the guar .
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