Xylooligosaccharides from lignocellulosic biomass: Structural features, prebiotic activity, and application in dairy systems

The increasing prevalence of chronic non-communicable diseases and recognition of diet as a key health modulator have intensified interest in functional foods, particularly prebiotics. Xylooligosaccharides (XOS) are structurally diverse, non-digestible oligosaccharides that can be produced from lignocellulosic biomass, supporting agro-industrial residue valorization and circular-bioeconomy strategies. This review critically examines XOS production, structure-dependent prebiotic mechanisms, metabolic and clinical evidence, analytical characterization, and applications in dairy systems. Recent literature highlights advances in enzymatic processes, pretreatment, purification, and compositional analysis, while also revealing important evidence gaps. XOS generally resist upper-gastrointestinal digestion and consistently support bifidogenic responses, but effects on other microbial groups and systemic metabolic outcomes vary with structure, dose, microbiota, and experimental model. In dairy applications, XOS may influence product stability, texture, sensory properties, and culture viability; however, these responses are matrix-, formulation-, and dose-dependent, and technological compatibility should not be interpreted as proof of prebiotic efficacy.