Hydrophobic Complexation Promotes Enzymatic Surfactant Synthesis from Alkyl Glucoside/Cyclodextrin Mixtures

The unique ability of cyclodextrin glycosyltransferase to form and utilize the cyclic maltooligosaccharide cyclodextrin (CD) makes this enzyme an attractive catalyst for the synthesis of alkyl glycosides. Here, we characterize the sugar headgroup elongation of alkyl glucosides (acceptor) via two transglycosylation reactions from either a linear (maltohexose) or a cyclic (CD) glycosyl donor. Inclusion complex formation overcomes both poor substrate solubility and aggregation. We have used pure alkyl glucosides and alpha CD as model compounds. The complex between CD and alkyl glucoside was efficiently used as a substrate. Kinetic and thermodynamic measurements allow the prediction of the optimal synthesis conditions. This optimum corresponds to the transition between a donor-limiting and an acceptor-limiting regime. The resulting rational design should lead to the practical development of a cost-efficient industrial synthesis. Our findings with respect to the importance of complexation should also readily apply to other enzymatic systems.