Enhancement of selectivity for producing gamma-cyclodextrin

The production of cyclodextrins (CDs) by cyclodextrin-glycosyl-transferase (CGTase) from Bacillus firmus was studied, with respect to the effect of th e source of starch upon CD yield and on the selectivity for producing gamma -CD. Cyclodextrin production tests were run for 24 h at 50 degrees C, pH 8. 0, and 1 mg/L of CGTase, and substrates were maltodextrin or the starches o f rice, potato, cassava, and corn hydrolyzed up to D.E. 10. Cornstarch was the best substrate for producing gamma-CD. Later, glycyrrhizin (2.5% [w/v]) , which forms a stable complex with gamma-CD, was added to the cornstarch r eaction medium and increased the yield of gamma-CD to about four times that produced with only maltodextrin, but the total yield of CDs remained pract ically unchanged. Therefore, the results showed that the studied CGTase is capable of giving relatively high yield of gamma-CD in the presence of glyc yrrhizin as complexant and cornstarch as substrate.