Synthesis of fructooligosaccharides (FosA) and inulin (InuO) by GH68 fructosyltransferases from Bacillus agaradhaerens strain WDG185

Abstract

Fructooligosaccharides (FOS) and inulin, composed of β-2-1 linked fructose units, have a broad range of industrial applications. They are known to have various beneficial health effects and therefore have broad application potential in nutrition. For (modified) inulin also for non-food purposes more applications are arising. Examples are carboxymethylated inulin as anti-scalant and carboymlated inulin as emulsifiers. Various plants synthesize FOS and/or inulin type of fructans. However, isolating of FOS and inulin from plants is challenging due to for instance varying chains length.There is an increasing demand for FOS and inulin oligosaccharides and alternative procedures for their synthesis are attractive. We identified and characterized two fructosyltransferases from Bacillus agaradhaerens WDG185. FosA, a β-fructofuranosidase, synthesises short chain fructooligosaccharides (GF2-GF4) at high sucrose concentration, whereas InuO, an inulosucrase, synthesises a broad range of inulooligosaccharides (GF2-GF24) from sucrose, very similar to plant derived inulin.FosA and InuO showed activity over a broad pH range from 6 to 10 and optimal temperature at 60°C. Calcium ions and EDTA were found to have no effect on the activity of both enzymes. Kinetic analysis showed that only at relatively low substrate concentrations both enzymes showed Michaelis-Menten type of kinetics for total and transglycosylation activity. Both enzymes showed increased transglycosylation upon increasing substrate concentrations. These are the first examples of the molecular and biochemical characterization of a β-fructofuranosidase (FosA) and an inulosucrase enzyme (InuO) and its product from a Bacillus agaradhaerens strain.