Enzymatic synthesis of oligosaccharides: product removal during a kinetically controlled reaction.

Abstract

In this article, the enzymatic production of oligosaccharides, which is an example of a kinetically controlled reaction, is studied. The aim is to show that the product yield can be enhanced by continuous removal of oligosaccharides from the reaction mixture. The oligosaccharides were removed by adsorption on activated carbon. The absorption could be described by the multicomponent Langmuir isotherm with different maximum saturation constants for mono-, di-, and trisaccharides. The affinity for trisaccharides was larger (k(tri) = 3.52 l/g) than for di- (k(di) = 0.94 l/g) and monosaccharides (k(mono) = 0.11 l/g). A model combining kinetics, adsorption on activated carbon, and mass transfer in an adsorption column was developed. Model calculations for the batch process with removal showed a yield improvement of 23% compared to the batch process without removal. Experimentally, a yield improvement of 30% was obtained. Model calculations for the continuous process studied did not result in an increase of the yield. The advantages of removal were masked by the negative influence of recirculation and the relative large time between formation and removal.