Synthesis of alkyl glycosides by cyclodextrin glycosyltranserase from Paenibacillus sp. RB01

Abstract

Alkyl glycosides have potential use as biodegradable detergents due to their high surface activity with low toxicity. Recent progress in the application of enzymes to the preparation of these surface-active compounds demonstrates the advantages to the chemical synthesis. In this work, alkyl glycosides were synthesized from β-cyclodextrin (β-CD) and various soluble alcohols by transglycosylation reaction using cyclodextrin glycosyltransferase (CGTase) from Paenibacillus sp. RB01. Several alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and 2-butanol) as glycosyl-acceptor substrates were evaluated. It was found that the reaction products which were analyzed by TLC were maximum for 30% methanol, 20-30% ethanol, 10-20% 1-propanol, 10% 2-propanol, 8% 1-butanol and 5-10% 2-butanol. Methanol was the most efficient acceptor toward this enzyme. From product analysis by HPLC, optimal reaction conditions for methyl glycoside synthesis from CD were to incubate 1.2% (w/v) β-CD and 240 U/mL of CGTase in a water/methanol system containing 30% (v/v) methanol, pH 6.0 and a temperature of 40C for 96 hours. The molecular weights of the main products were 194, 356, and 518 Daltons which were in accordance with methyl glycosides having one to three monosaccharide units attached to methyl group of methanol. The methyl monoglucoside (MG1) was prepared in large scale and isolated by Amberlite IRA-900 column. The structure of MG1 was confirmed as methyl α-D-glucopyranoside via 13C-NMR analysis.