Enzyme cyclomaltodextrin glucanotransferase

It is prepared from 5% solutions of - potato starch, which is incubated at 40 °C with the - enzyme cyclomaltodextrin glucanotransferase (CG-tease) (EC 2.4.1.19 nomenclature a-l,4-D-glu-can-4-a-D-( 1,4-a-glucano)-transferase). 

The cyciomaitodextrins (a-CD, -CD, and y-CD) can be selectively obtained from a fermentation culture or an enzyme digest of cyclomaltodextrin glucanotransferase reaction with solubilized starch. The majority of the cyclomaltohexaose (a-CD) can be separated from cycloma-Itoheptaose (/3-CD) and y-CD by their selective precipitation with p-cymene from the culture supernatant or from an enzyme digest [168]. The a-CD can then be precipitated from the supernatant with cyclohexene, which is extracted with acetone to remove the cyclohexene and the a-CD can be crystallized from water or a propanol-1/water solution [169]. The p-cymene precipitates of /3-CD and y-CD are put into a water solution and /3-CD selectively precipitated from y-CD with fluorobenzene. The y-CD is then precipitated with anthracene saturated in diethyl ether. After the removal of the fluorobenzene from /3-CD with acetone or ethanol extraction, /3-CD can be crystallized from water, and after the removal of anthracene with acetone or ethanol extraction from y-CD, it can also be crystallized from water [170,171]. The selective precipitations of the cyciomaitodextrins with various organic molecules is based on the selective formation of complexes of the organic molecules with the specific sizes of the cyciomaitodextrins and the relatively hydrophobic interior cavities of the cyciomaitodextrins [166,167,168]. 

Since CD production without the application of solvents may lead to microbial contamination, the process should be conducted at increased reaction temperature. A heat-resistant cyclomaltodextrin glucanotransferase, stable at temperatures above 100 °C, was isolated from Thermococcus species. The enzyme possesses also a-amylase activity and the production of CD is possible without the addition of a-amylase for the preliminary starch liquefaction [48]. 

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