Conversion of cyclodextrin into high-amylose starch of low molecular mass by means of cyclodextrin glucanotransferase

alpha-Cyclodextrin (CD) was converted by Bacillus macerans cyclodextrin glucanotransferase into highly insoluble high-amylose starch with a low average degree of polymerization (56-73), in yields as high as 78% over a wide range of temperatures (25-70 degreesC). Ability to undergo this conversion was highly concentration-dependent. gamma-CD was also convertible in good yield; however, beta-CD was relatively resistant to conversion. Degrees of polymerization and the percentages of amylose in the high-amylose products were estimated from spectrophotometric measurements on their iodine complexes. A plausible mechanism for conversion of CD into starch is proposed.