Fractionation of mono- and disaccharides via nanofiltration: Influence of pressure, temperature and concentration

Abstract

During the enzymatic biotransformation of lactose to galactooligosaccharides, complex saccharide solutions are generated. In most cases, solely a fraction of these saccharides is desired. Therefore, four industrial relevant nanofiltration membranes were tested regarding their suitability to fractionate mono- and disaccharides. The most promising membrane was selected for further experiments. With this membrane additional parameters, namely transmembrane pressure difference ΔpTM, filtration temperature ϑ and saccharide concentration cS, were varied under steady state conditions. Saccharide concentrations in all retentate and permeate samples were analyzed by HPLC-ELSD. The criteria of flux J, rejection RS, solute flux JS, fractionation purity ΔRS and efficiency QJS were evaluated in a complex food matrix at an industrial relevant scale. The interaction between ΔpTM and ϑ and their influence on ΔRS and QJS was further investigated by performing a multiple linear regression analysis with a quadratic model. The results suggest that for the chosen membrane and saccharides, trade-offs between purity and efficiency are necessary depending on the overall aim of the process. In the case that high purities need to be achieved, combinations of either low pressures and temperatures or high pressures and temperatures are promoting, while only increasing one parameter decreases the purity of the fractions. In order to achieve a high process efficiency high pressures are promoting.