Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: August 6, 2010
Publication Date: August 6, 2010
Citation: Cote, G.L., Dunlap, C.A., Vermillion, K., Rastall, R.A., Hernandez-Hernandez, O., Sanz, M.L. 2010. New food oligosaccharides via alternansucrase acceptor reactions [abstract]. International Carbohydrate Symposium. Abstract E-05-008. Technical Abstract: Alternansucrase [EC 22.214.171.124] is a glycosyltransferase from food-grade bacteria that is capable of synthesizing unique polysaccharides and oligosaccharides from sucrose. The enzyme typically produces the high-molecular weight polysaccharide alternan. However, in the presence of low-molecular weight acceptors, glucosyl units are transferred to the acceptor to form oligosaccharides. We have characterized the reactions with several acceptors in terms of both structures and biological activity. Maltose is one of the cheapest and most efficient acceptors. The initial reaction with alternansucrase leads to panose as the sole trisaccharide product. Panose can then react to form tetrasaccharides, which in turn lead to pentasaccharides, etc. Although early calculations postulated the possibility of an exponentially increasing number of products as degree of polymerization (DP) increased, we found that only a limited number of structures were formed, apparently determined by the kinetics of each subsequent glycosyl transfer reaction. Gentiobiose, although it contains a ß-D-glucosyl linkage instead of the a-linkage found in sucrose, alternan and maltose, was also a very efficient acceptor. The pattern of product structures was analogous to those from maltose. The acceptor reaction was found to be useful in eliminating the bitter taste of gentiobiose. Both the gentiobiose and maltose products were shown to possess prebiotic activity when tested against human fecal bacterial cultures in vitro. However, the maltose products are digested in humans to give a slow increase in blood glucose levels. For this reason, the maltose acceptor products are used in the commercial low-glycemic sweetener Sucromalt. Most recently, the products arising from raffinose have been characterized. One unusual structural feature is that both the galactosyl and fructosyl units become glucosylated, leading to a much greater number and variety of oligosaccharide products. In vitro testing with mixed human fecal bacteria suggests that these products increase the number of both bifidobacteria and lactobacilli whereas the population of bacteroides does not change.