Reaction-integrated separation of isomaltose by ad- and desorption on zeolite

This paper describes studies carried out into downstream processing for an enzymatic system producing isomaltose by glucosyltransfer, in which the isomaltose appears as an intermediate in a consecutive reaction chain. To avoid these consecutive reactions, reaction-integrated separation by adsorption was established. A specific β-zeolite was investigated as a selective adsorbent for the product isomaltose, and the influence of eluent and temperature on the desorption process was researched. As eluent, 50% (v/v) ethanol and pure water were compared. Using 50% ethanol the amount of desorbed isomaltose is about 23% higher than in pure water. In both cases desorption takes place over a period of more than 50 h and at a temperature of 70 °C. Residual moisture on zeolite significantly decreases adsorption capacity. In batch experiments, the half-life of zeolite stored in water is about 50 h, but for a continuous flow in a packed bed column, the half-life decreases to 7 h. Based on these findings, a design for downstream processing is proposed using a counter-current flow temperature swing displacement desorption sequence. Here, product concentration can be increased by multiple usage of the desorption liquid.