Development and application of a nanofiltration process as membrane bioreactor for the production of galacto-oligosaccharides with increased degree of polymerization
Food Chemistry
Final Report Abstract
A membrane bioreactor for the continuous production of gal-COS and GOS was developed. For the production of these oligosaccharides the ultrafiltration membrane GE with a Nominal Molecular Weight Cut-Off of 500-1000 Da was proven to be suitable. Gal-COS and GOS are described to exhibit bioactive and especially anti-adhesive activities by inhibiting the adhesion of pathogens at the intestinal epithelial cell surface. These sugars were synthesized successfully in the developed membrane bioreactor. A purified and enriched GOS product was obtained within one process step (milestone 1). The separation of the GOS (DP 3 – 5) from mono- and disaccharides by membrane filtration was difficult due to their little difference in molecular weight. Therefore, no GOS with higher degree of polymerization in comparison to the corresponding batch process without filtration could be synthesized. Nevertheless, the concentration of the GOS and the oligosaccharide content in total sugar was higher in all experiments in the membrane bioreactor in comparison to the batch process without filtration. A purified and enriched oligosaccharide preparation containing gal-COS was produced in a membrane bioreactor for the first time (milestone 2). The developed membrane bioreactor process is an effective, continuous method to produce gal-COS in high amounts. The enzymatic production of the gal-COS and the ultrafiltration for 16 h in the membrane bioreactor showed a high enrichment and purification of the sugars, which was better than after 6 h processing. The retentate contained a concentration of oligosaccharides up to 340 g/ L and an oligosaccharide content in total sugar of 75.6 %. The oligosaccharide product containing gal-COS exhibited anti-adhesive activity against a pathogen E. coli strain with K88 fimbriae (ETEC K88 ECL 13795) on adhesion to porcine erythrocytes in a hemagglutination assay in vivo (milestone 3). The establishment of the membrane bioreactor process on industrial scale would facilitate the manufacturing of bioactive gal-COS in sufficient amounts and be available as functional food ingredients for consumers.
