Mw.ir. M.E. Bruins : Oligosaccharide production with thermophylic enzymes

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23 Jun 2003 16:00
Unit: Wageningen University
Location: Aula (gebouw 362), Gen. Foulkesweg 1, Wageningen
Promotor: prof.dr. R.M. Boom (Food Process Engineering)
Co Promotor: dr.ir. A.E.M. Janssen

 The goal of the research reported in this thesis was to develop a process concept for the tailor made production of oligosaccharides. Our main interest was in a production process at elevated temperatures. This can have many advantages, amongst which is the possibility to increase the substrate concentration. We used a thermophilic ß-glycosidase from Pyrococcus furiosus. The ß-glycosidase was used in the enzymatic oligosaccharide synthesis from monosaccharides or disaccharides. Monosaccharides can be condensated to disaccharides and disaccharides can be transglycosylated to trisaccharides. The high substrate concentrations gave a substantial increase in the oligosaccharide yields. Unfortunately, the higher temperatures also led to faster enzyme inactivation, not only because of the direct denaturation of the enzyme due to temperature, but also because of the occurrence of Maillard reactions. The Maillard reaction occurs in sugar-protein (in our case enzyme) systems at higher process temperatures. Maillard products are brown pigments that colour the reaction mixture. The brown colour formation and the enzyme inactivation were described as a function of temperature and time. The prevention of Maillard reactions is discussed. Further reaction optimisation required a downstream processing method for oligosaccharide separation. This was also essential for the production of a pure oligosaccharide product. Chromatographic experiments were performed and a simulated moving bed (SMB) was modelled. This system was compared to a system with nanofiltration for separation. Various aspects of the process were discussed further. Emphasis was on the specific influence of temperature on the process and on further optimisation of the downstream processing of oligosaccharides.
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