Effects of substrates and reaction conditions on production of cyclodextrins using cyclodextrin glucanotransferase from newly isolated Bacillus agaradhaerens KSU-A11

Abstract

The effects of reaction conditions on cyclodextrins (CDs) production by CGTase from newly isolated Bacillus agaradhaerens KSU-A11 is reported. Among six types of starch tested, potato starch gave highest starch conversion into CDs. In addition, CDs yield was about three fold higher when using gelatinized potato starch in comparison to raw starch. The total CDs production was increased with increasing pH, showing maximum starch conversion at pH 10. Furthermore, the proportion of γ-CD was relatively higher under slightly acidic-neutral conditions than at alkaline pH with a maximum proportion of 35.6% at pH 7 compared to 7.6% at pH 10. Maximum starch conversion into CDs was seen at reaction temperature of 55ºC. Lower reaction temperature led to higher proportion of γ-CD with maximum percentage at 35ºC. Cyclization reaction was significantly promoted in the presence CaCl 2 (10 mM), while in the presence of ethyl alcohol there was significant decrease in CD production particularly at high concentration. β-CD was the major product up to 1 hr reaction period with traces of α-CD and no detectable γ-CD. However, as the reaction proceed, γ-CD started to be synthesised and α-CD concentration increased up to 4 hrs, where the CDs ratios were 0.27:0.65:0.07 for α-CD:β-CD:γ-CD, respectively. In addition, optimum CGTase/starch ratio was obtained at 80 U/g starch, showing highest starch conversion into CDs. All the parameters involved have been shown to affect the products yield and/or specificity of B. agaradhaerens KSU-A11 CGTase.

Integral Use of Amaranth Starch to Obtain Cyclodextrin Glycosyltransferase, by Bacillus megaterium, to Produce β-Cyclodextrin

“…Both values were very similar to those obtained in this study. On the other hand, Ibrahim et al ( 2011 ) reported that the CGTase from B. agaradhaerens was purified in three steps, with a recovery of 26% and twice as much specific activity when compared to that observed in this study. After 3 months, the purified CGTase stored at −4°C kept 85% of its biological activity.…”

“…The CGTase shows a Mr similar to other CGTases such as the produced in SmF by Bacillus sp. (69 kDa) and B. firmus (80 kDa) using CS as carbon source (Suntinanalert et al, 1997 ; Pishtiyski et al, 2008 ; Savergave et al, 2008 ; Ibrahim et al, 2011 ). However, there are some reports on CGTases with different Mr, such as that of Paenibacillus macerans grown with CS where its Mr was 114 kDa (Urban et al, 2012 ).…”

“…Potato starch seems to give the highest conversion into CDs. Additionally, CDs yield was about 3-fold higher when using gelatinized potato starch in comparison to raw starch (Ibrahim et al, 2011 ).…”

“…Corn starch (CS) was also used as a positive control of the trial. The method carried out by Ibrahim et al ( 2011 ), with some modifications, was used for the CDs formation. Briefly, starch gelatinization was performed at 50 and 70°C (for AS and CS, respectively) for 10 min in 50 mM glycine buffer (pH 8); then the reaction mixture was cooled to room temperature.…”

Continuous production of cyclodextrins in an ultrafiltration membrane reactor, catalyzed by cyclodextrin glycosyltransferase from Bacillus circulans DF 9R

“…These authors obtained the best results with corn starch and concluded that starches from different sources can affect the production of CD and that this could be due to differences in the physical structure of the starch granules and their properties. Ibrahim et al used starches from various sources, including corn, potato, sago, rice, and cassava and obtained the highest CD conversion with potato starch (38.7%). These authors found no differences in the α‐:β‐:γ‐CD relation obtained by varying the starch source.…”