Synthesis of Levan and Fructooligosaccharides by Levansucrase: Catalytic, Structural and Substrate-Specificity Properties

Due to their physiological and functional properties, novel fructooligosaccharide (FOSs) and levan production has gained significant interest. Levansucrase (EC 2.4.1.10, LS), a glycosyl transferase, catalyzes the transfer of fructose from a non-activated sucrose donor, to an acceptor molecule, typically via a β-(2-6)-glycosidic bond. Significant prebiotic products of LS-catalyzed transfructosylation reaction include β-(2-6)-levans, neo-type FOSs, levan-type FOSs and heterofructooligosaccharides. The LS reaction/product profile consists of four reactions: exchange (sucrose), hydrolysis (glucose and fructose), oligomerization (FOSs) and polymerization (levan). Within the context of this review, the catalytic efficiency and the reaction specificity (transfructosylating versus hydrolytic) of LS was discussed as function of the enzyme’s structure and the reaction conditions. The acceptor specificity of LSs, leading to the synthesis of heterofructooligosaccharides, was also examined. With the purpose of increased enzymatic stability, reusability, advanced levan/FOS production, the immobilization of LS was discussed.