Enzymatic production of cyclodextrins

Cyclodextrins (CD) are enzymatically modified starches with a wide range of applications in food, pharmaceutical and chemical industries, agriculture and environmental engineering. They are produced from starch via enzymatic conversion using cyclodextrin glycosyl transferases (CGTases) and partly alpha-amylases. Due to its low solubility in water, separation and purification of beta-CD is relatively easy compared to alpha- and gamma-CD. In recent years more economic processes for gamma-CD and especially alpha-CD production have been developed using improved CGTases and downstream processing. New purification steps, e.g. affinity adsorption, may reduce the use of complexing agents. The implementation of thermostable CGTases can simplify the production process and increase the selectivity of the reaction. A tabular overview of alpha-CD production processes is presented. CDs are normally retailed as a dry, fine and crystalline powder, which remains stable long term. Due to its easier purification, the price of beta-CD has decreased significantly in the past, whereas alpha- and gamma-CDs are still more expensive. For industrial application, beta-CD costs around US$ 3-4/kg, alpha-CD US$ 20-25/kg and gamma-CD US$ 80-100/kg. In 1998, global consumption was around 6,000 metric tons, with an annual growth rate of 15-20% (McCoy 1999). Most CD sold is low-priced beta-CD but, with their prices coming down, market shares of alpha- and gamma-CD Are expected to increase significantly in the next decade. The main producers are Cerestar, and Roquette Freres (France), Wacker Biochem (Germany) and Ensuiko Sugar and Nihon Shokuhin Kako in Japan (McCoy 1999).