Cyclodextrin glucanotransferase: fundamentals and biotechnological implications.

Cyclodextrin glucanotransferase (CGTase) is an extracellular enzyme of the GH13 α-amylase family that catalyzes a unique intramolecular reaction known as cyclization to transform α-1, 4-glucans and similar starches into cyclodextrins. They also catalyze intermolecular transglycosylation reactions namely coupling, disproportionation, and some hydrolyzing effects on starch. The monomeric structures of the CGTase exhibit five domains (A, B, C, D, and E domains) with different molecular weights and amino acid sequences depending on the source. Among bacteria, Bacillus genus covers approximately 90% of the CGTase producers, while other genera like Klebsiella, Paenibacillus, and Thermoanaerobacter also shown decent contributions in recent studies. CGTase production is highly supported by alkaliphilic bacteria under submerged fermentation rather than solid-state fermentation. The bacterial sources, biochemical properties, production conditions, and structure of CGTases are compiled in this review. Cyclodextrins have the unique property of making inclusion complexes with various compounds, hence widely used in the food, pharmaceutical, cosmetics, laundry, and chemical sectors. This review presents a comprehensive view of CGTase produced by Bacillus spp., and other bacterial genera like Klebsiella, Paenibacillus, and Microbacterium. It also gives insight of the properties and recent biotechnological applications of cyclodextrins. KEY POINTS: • Transglycosylation reactions catalyzed by CGTase and their structural properties. • Comparative data of CGTase production by various genera and Bacillus spp. • Structures, properties, and applications of different cyclodextrins.