Development and application of a nanofiltration process as membrane bioreactor for the production of galacto-oligosaccharides with increased degree of polymerization

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Beta galactooligosaccharides (GOS) are beta glycosidically linked non digestible oligosaccharides composed of galactose with glucose or galactose at the reducing end and a degree of polymerization of 3 to 10 (mostly 3, 4 and 5). These oligosaccharides are synthesized from lactose by transgalactosylation activity of the enzyme beta galactosidase. Galactooligosaccharides exhibit biological activities. As prebiotics they promote the growth of commensal bacteria in the intestine, they modulate the immune system and inhibit the adhesion of pathogens on the gastrointestinal epithelial cell surface. A combination of the enzymatically production of galactooligosaccharides and a nanofiltration for the separation of the residual monosaccharides and disaccharides in a membrane bioreactor (MBR) could be a more efficient process for galactooligosaccharide production. Highly pure oligosaccharide preparations could be achieved within one process step. Moreover, the inhibition of the enzyme by high glucose and galactose concentrations could be decreased by the simultaneously separation of the monosaccharides from the glucose. Galactooligosaccharides with higher degree of polymerization could be synthesized. The main goal of the research work is the development and application of a nanofiltration process as membrane bioreactor for the production of galactooligosaccharides with increased degree of polymerization.The milestones of the research plan are: The establishment of a nanofiltration on a 2 to 3 L scale for the retention of oligosaccharides and removal of residual mono- and disaccharides by permeation through the membrane. The use of a nanofiltration system as membrane bioreactor to produce galacto-oligosaccharides with increased degree of polymerization. The use of the membrane bioreactor to produce galactosylated chitin oligosaccharides, and chitosan oligosaccharides with increased degree of polymerization. The instrumental analysis of oligosaccharides and the effect of oligosaccharides on pathogen adhesion. Advantages of the planned research work: The conversion of lactose to oligosaccharides with biological activities can lead to a valorization of the disaccharide. Chitin and chitosan, which should be applied as galactosyl acceptors, are inexpensive to produce and exhibit various biological activities (e.g. antibacterial, prebiotic, antiadhesive activities). The combination of the separate processes for the oligosaccharide production by enzymatic beta transgalactosylation and the nanofiltration for the purification of the product within one process in a membrane bioreactor could be more efficient.By permeation of the monosaccharides during oligosaccharide production in the membrane bioreactor the yield and the degree of polymerization of these sugars could be increased.