ORIGINAL ARTICLE Effect of organic solvents on the yield and specificity of cyclodextrins by recombinant cyclodextrin glucanotransferase (CGTase) from Anaerobranca gottschalkii Berhane T. Tesfai • Dan Wu • Sheng Chen • Jian Chen • Jing Wu Received: 2 April 2012 / Accepted: 19 July 2012 Ó Springer Science+Business Media B.V. 2012 Abstract Cyclodextrin glucanotransferase (CGTase, EC 2.4.1.19) is an enzyme that degrades starch and starch related glucans into cyclodextrins (CDs) by intramolecular transglycosylation reaction. The biochemical activity of recombinant CGTase from Anaerobranca gottschalkii for the yield and product specificity of cyclodextrins was investigated in the presence of organic solvents. Compared with the control of starch bioconversion, addition of vari- ous organic solvents generally increased the total CD and product specificity by affecting product inhibition and/or intermolecular transglycosylation reaction. The highest conversion (45 %) of starch to CDs was obtained in the presence of ethanol, while the simultaneous addition of two organic solvents, decanol-ethanol, comparatively showed a reduced total yield of 39 %. Despite this, the highest product ratio of 91 % a-CD, and 64 % b-CD was obtained in the presence of decanol and cyclohexane respectively. The effect of organic solvents on the yield and specificity of CD was attributed mainly to their effect on product inhibition and transglycosylation reaction. Although the use of two organic solvents showed almost a significant increase in total yield of CDs, it resulted in a comparatively lower specific product yield compared to their respective individual effect. Generally, normal enzyme activity was favoured at higher temperature of 65 °C, but the addition of organic solvents, in most cases, was found to decrease the bioconversion. Thus, the preferred optimal condition was reduced to 40 °C, where the maximal conversion of starch to CDs in general and a-CD in particular was achieved. Keywords Cyclodextrin Glucanotransferase (CGTase)  Cyclodextrin (CD)  Organic solvents  Biochemical activity  Starch Bioconversion  Anaerobranca gottschalkii Introduction Cyclodextrin glucanotransferase (CGTase, EC 2.4.1.19) is an enzyme that degrades starch and starch related glucans into cyclodextrins (CDs) by intramolecular transglycosy- lation reaction called cyclization reaction [1]. Additionally, CGTases also catalyze intermolecular transglycosylation reactions such as coupling and disproportionation as well as hydrolytic reactions [2]. Unlike the cyclization reaction in which a linear oligosaccharide (starch) chain is cleaved to form a non-reducing end sugar of the same molecule and thus forming a cyclic oligosaccharide (CDs), the coupling reaction cleaves the cyclic oligosaccharides to form a linear acceptor maltooligosaccharide substrate, while the dispro- portionation reaction cleaves a linear maltooligosaccharide to form a new acceptor maltooligosaccharide [2]. CGTases are also known for their relatively weak hydrolytic reac- tions. CGTases are named as a-, b-, and c- according to their major CD product. Cyclodextrins (CDs) are cyclic oligosaccharides con- sisting of 6(a-cyclodextrin) 7(b-cyclodextrin), 8(c-cyclo- dextrin) and more glucose units linked by a-(1, 4) bonds [3]. CDs have a special hollow truncated structure [1] with hydrophobic interior and hydrophilic surface part [4]. This B. T. Tesfai  S. Chen  J. Chen  J. Wu (&) State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Avenue, Wuxi 214122, People’s Republic of China e-mail: jingwu@jiangnan.edu.cn B. T. Tesfai  D. Wu  S. Chen  J. Chen  J. Wu School of Biotechnology and Key Laboratory of Industrial Biotechnology Ministry of Education, Jiangnan University, 1800 Lihu Avenue, Wuxi 214122, People’s Republic of China 123 J Incl Phenom Macrocycl Chem DOI 10.1007/s10847-012-0225-6