Resumen de Enzymatic synthesis of novel bioactive oligosaccharides via microbial transglycosidases acting on sucrose: structural characterization and bioactivity study
The production of new bioactive oligosaccharides today raises a great interest due to their potential use as functional components in the food and pharmaceutical industry. Among the various strategies employed for the production of these oligosaccharides, enzymatic processes have great potential, as they usually have a high substrate specificity as well as regio- and stereo- selectivity. In this PhD Thesis, the production, via enzymatic synthesis, of various oligosaccharides that could present a potential industrial interest, particularly regarding their prebiotic capacity, has been studied. In general, these oligosaccharides are synthesized by transglycosidase enzymes (EC 2.4.1) produced by lactic acid bacteria capable of catalyzing reactions of transferring the glucose or fructose unit of sucrose (donor) to a wide range of carbohydrate acceptors, giving rise to high yields of synthesis. Specifically, in this PhD Thesis, the optimized synthesis of the trisaccharide 2-alpha-glucosyl-lactose, also called 4'-galactosyl-kojibiose, the disaccharide kojibiose, the trisaccharide lactulosucrose and sets of fructosyl oligosaccharides derived from maltose, lactosucrose, and raffinose is described. Besides, the structural characterization (glycosidic linkage, monosaccharide composition and degree of polymerization) of novel synthesized oligosaccharides, carried out by nuclear magnetic resonance (NMR) or mass spectrometry (MS) is also discussed. Both the synthesis and characterization of these oligosaccharides are presented in the first six chapters, encompassing the first part of this thesis. Moreover, once the synthesis was optimized, the purification of compounds of interest was carried out to be used in the bioactivity studies in order to determine the prebiotic potential of these oligosaccharides. These studies are presented in the second part of this thesis, Chapters 7 to 10. Depending on the viability of the purification process, which is usually one of the most expensive in the process of obtaining oligosaccharides, different types of tests were conducted both in vitro and in vivo using animal models. Both the structural characterization of these oligosaccharides as well as bioactivity studies conducted, will further allow deepen in the knowledge of the structure-function relationship, essential for the development and eventual commercialization of these new ingredients with potential functionality.
