Cyclodextrins are cyclic α-1,4-glucans that are produced from starch or starch derivates using cyclodextrin glycosyltransferase (CGTase). The most common forms are α-, β-, and γ-cyclodextrins. This mini-review focuses on the enzymatic production, unique properties, and applications of γ-cyclodextrin as well as its difference with α- and β-cyclodextrins. As all known wild-type CGTases produce a mixture of α-, β-, and γ-cyclodextrins, the obtaining of a CGTase predominantly producing γ-cyclodextrin is discussed. Recently, more economic production processes for γ-cyclodextrin have been developed using improved γ-CGTases and appropriate complexing agents. Compared with α- and β-cyclodextrins, γ-cyclodextrin has a larger internal cavity, higher water solubility, and more bioavailability, so it has wider applications in many industries, especially in the food and pharmaceutical industries.

Malto-oligosaccharides were products of the degradation of corn starch in the γ-CGTase production by Bacillus macorous WSH02-06, and catabolically repressed the synthesis of γ-CGTase. The investigation of the enzyme production at different agitation speeds, pH-stat values and temperatures revealed that the amount of malto-oligosaccharides accumulated in cultivation was in direct connection with the specific cell growth rate. When the maximal specific growth rate was higher than 0.2 h−1, the γ-CGTase yield decreased. Thus, the nutrients were supplied in the exponential feeding mode for limiting the maximal specific growth rate and the γ-CGTase yield was promoted to the highest value of 2565UmL−1 that was 6.88-fold higher than that achieved in the batch fermentation. © 2006 Elsevier Inc. All rights reserved.

The production of γ-cyclodextrin glucanotransferase (γ-CGTase) from Bacillus macorous WSH02-06 was optimized in shake flasks using conventional sequential techniques and statistical experimental design. Effects of nutrients including carbon and nitrogen sources, cation ions, initial pH, and temperature on γ-CGTase production were investigated. Corn starch, peptone, Mn2+, and Zn2+ were found to be essential for obtaining high γ-CGTase activity and biomass. The promoting effect of manganese and zinc on enzyme production has not been reported previously. According to the results of orthogonal array experiment, the optimal culture medium for high γ-CGTase activity was determined. Maximal γ-CGTase activity obtained in the optimized culture broth was about 250U/mL which was 10-fold higher than that obtained in the basal medium. Time course of cell growth and γ-CGTase production in a 7 l fermenter showed that enzyme production was growth associated, and that maximum g-CGTase activity reached 277U/mL in 17 h.

The effects of different agitation speeds and DO concentrations on g-CGTase production by Bacillus macorous WSH02-06 were investigated. Higher agitation speeds and DO concentrations were favorable for cell growth but inhibited g-CGTase production. Lower agitation speeds and DO concentrations were in favor of attaining relatively higher value of specific g-CGTase production rate in the later stage of fermentation. Two-stage agitation speed control strategy and two-stage DO control strategy were developed and compared for their potential in improving g-CGTase production. By using the two-stage DO control strategy, gCGTase yield and productivity reached 552.3 U/ml and 6.13 kU/(l h), respectively, increasing by 77.9% and 50.9% over the fermentation at constant agitation speed of 300 rpm.