Downstream processing technologies in the biocatalytic production of oligosaccharides.

Oligosaccharides are important ingredients for food and feed products. There has therefore been much interest in the development of biocatalytic processes for their production. Irrespective of the oligosaccharide manufacturing route, that is, bottom-up synthesis or controlled depolymerization of a polysaccharide, isolating the product from the reaction mixture usually presents a considerable challenge. In order to establish a successful production process, development of an efficient (high-yielding, cost-effective) route of downstream processing (DSP) is key. Here, we review unit operations, and their corresponding separation principles, used in the production of oligosaccharides. Ligand-exchange and other forms of chromatography, frequently applied in set-ups for continuous process operation, are widely used. Membrane technologies, especially nanofiltration but also electrodialysis, have gained considerably in importance. Solvent extraction methods are specialized techniques in oligosaccharide production that have occasionally been considered. We use examples from oligosaccharide productions, in which the upstream part of the process has been well established (e.g., galacto- and fructo-oligosaccharides), to discuss advances in the materials used for separation and to describe salient process parameters for optimization of the respective DSP unit operation. The importance of unit operations assembly into an overall efficient DSP route is discussed. The applicability of these unit operations in the production of upcoming oligosaccharide products (e.g., xylo-oligosaccharides) is considered.