Abstract: Large-ring cyclodextrin (LR-CD) is a cyclic α-1,4-glucan consisting of nine to several hundred glucopyranose units. LR-CD is mainly prepared by the cyclization activity of cyclodextrin glucosyltransferase or 4-α-glucanotransferase that catalyzes intramolecular transglycosylation reaction on amylose. Compared with common α-, β-, and γ-CD, LR-CD has a larger cavity size and exhibits unique structural and physicochemical properties, showing potential applications in several fields like food, medicine and biology. However, LR-CD has not been industrially produced or applied due to the high cost and low productivity as well as lack of effective separation and purification methods. In this article, recent progress and challenges on the enzymatic preparation of LR-CD are reviewed from the aspects of optimizing reaction substrates, designing new reaction pathways based on template induction, enzyme modification, and separation and purification of products. We hope this article could provide a reference for the industrial production and application of LR-CD.

Key words: large-ring cyclodextrin; cyclodextrin glycosyltransferase; 4-α-glucanotransferase; starch; template induction; molecular modification