The Immunomodulatory Properties of β-2,6 Fructans: A Comprehensive Review

Abstract

Polysaccharides such as β-2,1-linked fructans including inulin or fructose oligosaccharides are well-known prebiotics with recognised immunomodulatory properties. In recent years, other fructan types covering β-2,6-linked fructans, particularly microbial levans, have gained increasing interest in the field. β-2,6-linked fructans of different degrees of polymerisation can be synthesised by plants or microbes including those that reside in the gastrointestinal tract. Accumulating evidence suggests a role for these β-2,6 fructans in modulating immune function. Here, we provide an overview of the sources and structures of β-2,6 fructans from plants and microbes and describe their ability to modulate immune function in vitro and in vivo along with the suggested mechanisms underpinning their immunomodulatory properties. Further, we discuss the limitations and perspectives pertinent to current studies and the potential applications of β-2,6 fructans including in gut health.

Keywords: exopolysaccharide; fructan; fructooligosaccharide; fructose; gut health; immunity; immunomodulatory; levan; microbiota; polysaccharide.

Figure 1

Schematic structural representation of plant or microbial β-2,6 fructans with reported immunomodulatory properties. Microbial levan or plant β-2,6 fructans are shaded orange or blue, respectively. Green pentagons represent fructose, blue circles, glucose and black circles, O-acetylated glucose. * Tentative structure. Also see Table 1 and Table 2 for descriptive structures.