Gluco‐oligosaccharides as potential prebiotics: Synthesis, purification, structural characterization, and evaluation of prebiotic effect

Abstract

Prebiotics have long been used to modulate the gut microbiota and improve host health. Most established prebiotics are nondigestible carbohydrates, especially short-chain oligosaccharides. Recently, gluco-oligosaccharides (GlcOS) with 2-10 glucose residues and one or more O-glycosidic linkage(s) have been found to exert prebiotic potentials (not fully established prebiotics) because of their selective fermentation by beneficial gut bacteria. However, the prebiotic effects (non-digestibility, selective fermentability, and potential health effects) of GlcOS are highly variable due to their complex structure originating from different synthesis processes. The relationship between GlcOS structure and their potential prebiotic effects has not been fully understood. To date, a comprehensive summary of the knowledge of GlcOS is still missing. Therefore, this review provides an overview of GlcOS as potential prebiotics, covering their synthesis, purification, structural characterization, and prebiotic effect evaluation. First, GlcOS with different structures are introduced. Then, the enzymatic and chemical processes for GlcOS synthesis are critically reviewed, including reaction mechanisms, substrates, catalysts, the structures of resultant GlcOS, and the synthetic performance (yield and selectivity). Industrial separation techniques for GlcOS purification and structural characterization methods are discussed in detail. Finally, in vitro and in vivo studies to evaluate the non-digestibility, selective fermentability, and associated health effects of different GlcOS are extensively reviewed with a special focus on the GlcOS structure-function relationship.

Novel Galacto-oligosaccharides from Lactose: Chemical Synthesis, Structural Characterization, and in Vitro Assessment of Prebiotic Activity

“…For now, the neutralization method was used for the lab-scale separation of GOS. Certainly, greener, more efficient separation methods with good scalability are needed for future large-scale production, such as nanofiltration and ion-exchange chromatography. − Our laboratory has been investigating the nanofiltration separation for the purification (removal of sulfuric acid and glucose) and fractionation of oligosaccharides. The residual sulfuric acid in the permeate is proposed to be recycled and reused to improve sustainability and reduce the environmental impact of the production process.…”

“…This moderate DP range (2−4) meets the general requirement of prebiotic oligosaccharides in terms of nondigestibility and fermentability because larger oligomers would be less fermentable with lower selectivity (probably act as dietary fibers instead of prebiotics). 50 Glycosidic Linkage Analysis by HSQC NMR. The glycosidic linkages in the synthesized GOS were identified by 2D HSQC NMR in D 2 O and compared with those in the commercial β-GOS (Figure 6).…”

“…This is likely because the residual lactose in the β-GOS is purposely removed by nanofiltration. , Overall, the MALDI-TOF MS analysis revealed that the synthesized GOS and the commercial β-GOS both are a mixture of oligosaccharides (DP 2–6) with dominantly di-, tri-, and tetrasaccharides present (89% in GOS_lactose and 92% in β-GOS). This moderate DP range (2–4) meets the general requirement of prebiotic oligosaccharides in terms of nondigestibility and fermentability because larger oligomers would be less fermentable with lower selectivity (probably act as dietary fibers instead of prebiotics) …”

Treatment of preterm brain injury via gut‐microbiota–metabolite–brain axis

“… 104 , 105 Prebiotic ingredients typically have a longer shelf life than probiotic ingredients, and this stability also provides convenience for storage and processing. 106 Therefore, prebiotics are gaining popularity in the field of digestive health or parenteral health.…”

Structure-Tunable Glucan Oligomer Production from Glucose and Disaccharide Glycosylation in an Unacidified LiBr·3.2H2O Molten Salt Hydrate

“…Another challenge of the top–down method lies in the fact that the glucan oligomer concentration is lower than 5 wt % − due to the limited polysaccharide solubility in most of the solvents, which inhibits its commercial application. As glucose/disaccharides have a much higher solubility in molten salt hydrates (MSHs) than polysaccharides, the bottom–up method can be carried out using concentrated glucose/disaccharides as the substrate, and it generally results in a promising glucan oligomer concentration higher than 50 wt %. , The conversion pathway of the bottom–up method involves two critical issues: (1) acid-catalyzed glycosylation among the hydroxyl groups on sugars; (2) in situ removal of the generated H 2 O from glycosylation to inhibit the rehydrolysis of the formed glucan oligomer into glucose. Recently, Zeng et al reported a simple glucan oligomer synthesis method using 76 wt % concentrated sulfuric acid as the reaction medium, achieving a promising glucan oligomer yield under mild conditions of 70 °C for 20 min .…”