Synthesis of large-ring cyclodextrin from tapioca starch by amylomaltase and complex formation with vitamin E acetate for solubility enhancement

Abstract

Recombinant amylomaltase from Corynebacterium glutamicum (CgAM) was used to synthesize large-ring cyclodextrins (LR-CDs) from tapioca starch. A mixture of LR-CDs (CD22–CD54) was obtained from both raw and soluble tapioca starch, but with different ratio of main products (CD25–CD30). Almost three-fold higher amount of products was formed indicating the preference for raw tapioca starch. The optimal condition was to incubate 1.0% (w/v) starch with 0.05U/ml CgAM in buffer pH 6.0 at 30°C for 18h. Total LR-CDs yield was 60.5mg/g starch. LR-CDs were resistant to hydrolysis by Rhizopus sp. glucoamylase but completely hydrolyzed by CgAM at high enzyme concentration. Solid inclusion complex between LR-CDs mixture and vitamin E acetate was formed, as analyzed by FTIR. For complex preparation, the 1:10mol ratio of LR-CDs to vitamin E was chosen because maximum amount of the vitamin was bound to LR-CDs and high complex yield was obtained. Aqueous solubility of vitamin E acetate in complex form increased 800-fold while the antioxidant activity decreased about 30%. This is the first work to demonstrate the use of tapioca starch in LR-CDs synthesis by CgAM and the complex formation between LR-CDs and vitamin E acetate as solubility enhancement process of vitamin.