Production and functional applications of fructooligosaccharides and their core bioactive components.

Fructooligosaccharides (FOS) are widely recognized as functional prebiotics with diverse physiological activities, including modulation of the gut microbiota, anti-diabetic effects, enhancement of immune responses, and other health promoting functions. Based on their terminal residues, FOS can be classified into fructose-terminated fructooligosaccharides (Fn, n = 2 ~ 9) and glucose-terminated fructooligosaccharides (GFn, n = 2 ~ 8). Compared with Fn, GFn exhibit distinct advantages in terms of raw material availability, production processes, manufacturing costs, and application potential, and therefore have received more attention. Among GFn, kestoses (GF2), nystose (GF3), and fructosylnystose (GF4) represent the core bioactive components and display distinct physiological effects. This review critically summarizes the current advances in the production and purification techniques of GFn mixtures and their core components (GF2, GF3 and GF4), with particular emphasis on 1-kestose due to its superior efficacy in gut microbiota modulation, aiming to provide valuable insights to support future production, application and development.