Transglycosylation reaction of cyclodextrin glycosyltransferase from Paenibacillus sp. RB01 for the synthesis of medium-chain alkyl glycosides

Abstract

Alkyl glycosides belong to the group of non–ionic surfactant. They were synthesized by transglycosylation reaction from β–cyclodextrin donor to alcohol acceptors using cyclodextrin glycosyltransferase (CGTase) from Paenibacillus sp. RB01 as a catalyst. The effect of alcohol acceptors on enzyme was determined by phenolphthalein method. The results showed that alcohol had effect on enzyme to some extent. The reaction performed as two phase system had lower influence to enzyme. However, the yield of transglycosylation products was also found to be lower. In the group of medium chain alcohol acceptor, isobutanol gave the highest yield while β–CD was reported as an appropriate donor. The results obtained after treatment the products with glucoamylase and α–glucosidase could be preliminary summarized that the products were both isobutyl monoglucoside and isobutyl (poly)glucoside with α 1, 4–linkage. The suitable condition was to incubate 5% (v/v) of isobutanol with 1.2 % (w/v) β–CD in 0.5 M acetate buffer pH 6.0 with enzyme 450 units/mL for 48 hours. The three main products were observed at Rt~7, 8 and 9 min by HPLC analysis. PLC was employed to isolate the expected products at indicated Rf values to confirm by mass relationship. The molecular weight of product at Rf = 0.74 (Rt~9 min) and Rf = 0.56 (Rt~8 min) were 259.1 and 421.2 g/mol, respectively. Thus, they were isobutyl–α–monoglucoside and isobutyl–α–maltoside, respectively. Reaction was then prepared in larger scale and purified by Amberlite IRA–900 column chromatography. The two purified products were checked for the emulsification properties using n–hexadecane forming–emulsion. The results revealed that isobutyl–α–monoglucoside had emulsification activity of 11.4% while isobutyl–α–maltoside had 41.1% of triton X–100. The emulsification stability of both products was more than 80 %.