Optimal membrane choice for microdialysis sampling of oligosaccharides

An analytical methodology based on microdialysis sampling, high- performance anion-exchange chromatography and integrated pulsed electrochemical detection for the monitoring of oligosaccharides in bioprocesses is presented. Amylopectin and model maltooligosaccharide standards; glucose, maltose, maltotriose, maltotetraose, maltopentaose, maltohexaose and maltoheptaose were used to demonstrate its versatility in view to sampling in enzymatic bioprocesses. The performance and characteristics of membranes with the same cut-off ranging between 3 and 100 kDa, were evaluated with respect to their extraction fraction (EF), permeability factors, temperature stability and protein (enzyme) interaction. All investigated membranes showed some non-specific interaction with enzymes. The EF and non-specific membrane-enzyme interactions were higher for the polysulfone membranes compared with the polyamide and polyethersulfone membranes. For all saccharides, the EF was independent of the concentration even for a 250-fold change in concentration. The EF and morphology of the membranes in their dehydrated state, as observed using scanning electron microscopy did not show any significant difference between membranes exposed to a 90°C temperature for 3 and 24 h indicating their applicability to the study of high temperature bioprocesses.