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

Abstract

Lactose is an underutilized byproduct of the dairy industry. Galacto-oligosaccharides (GOS) are established prebiotics with health-promoting properties. This study demonstrates a facile and high-yield chemical process to synthesize GOS from lactose as potential prebiotics in which lactose is hydrolyzed into galactose and glucose first, and they then undergo glycosylation to GOS in concentrated sulfuric acid. A GOS yield of 96% was obtained from 50% (w/w) initial lactose loading in 76% H 2 SO 4 after reaction at 70 °C for 20 min, with 99% conversion of lactose and minimal side products (galactose, glucose, anhydrosugars, and sugar degradation products). The synthesized GOS were a mixture of di-, tri-, and tetrasaccharides (47%, 25%, and 16%, respectively) with a small portion of larger oligosaccharides (DP up to 6). Diverse glycosidic linkages including α/β-(1→6), α/β-(1→4), β-(1→3), α/β-(1→2), and α-(1→1) were identified between galactose and glucose units in the GOS. In vitro fermentation studies revealed that GOS promoted the growth of all tested Lactobacillus strains, with performance comparable to that of a commercial prebiotic GOS synthesized enzymatically.

Revolutionizing Renewable Resources: Cutting-Edge Trends and Future Prospects in the Valorization of Oligosaccharides

“…These challenges rendered the chemical synthesis approach impractical for large-scale production [72].…”

Selective utilization of gluco‐oligosaccharides by lactobacilli: A mechanism study revealing the impact of glycosidic linkages and degree of polymerization on their utilization

“…For the three tested GlcOS mixtures, their sugar components were characterized by high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) (see Section 2.4). Besides, the type(s) of O-glycosidic linkages between glucose residues in the GlcOS mixtures were characterized by two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D HSQC NMR, 1 H-13 C) spectroscopy, which was carried out on a Bruker AVANCE III 500 MHz instrument with a DCH cryoprobe at 30 • C. The detailed procedure of HSQC NMR analysis was described in our previous studies (Zeng, Li, et al, 2023;Zeng, Mohapatra, et al, 2023).…”

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

“…Recent literature reports that glucan oligomer has versatile applications in agriculture, healthcare, and functional materials depending on its intramolecular glycosidic bond type. For example, the β(1 → 4) glycosidic bond-linked glucan oligomer is a unique nontoxic elicitor that can activate plant defense responses and therefore improve resistance to fungi, bacteria, and viruses. , The α-type (e.g., α(1 → 4), α(1 → 6)) glucan oligomer cannot be digested by the upper gastrointestinal tract but can stimulate the growth and function of probiotics in the colon, such as Bifidobacteria and Lactobacilli , which can be used as prebiotics to maintain the health of the host digestive system. , Besides, a recent study also summarized the utilization of a short-chain glucan oligomer linked through α(1 → 4) glycosidic bonds in functional biomaterial preparation through self-assembly, offering potential applications in drug carriers, Pickering emulsifiers, or renewable films . Thus, the production of structure-tunable glucan oligomers with a specific type of glycosidic linkage has a critical effect on its valorization.…”