Oligosaccharides with different glycosidic bonds regulate gut microbiota: differential modulation of bacterial and fungal communities and their metabolism in vitro.

Oligosaccharides significantly impact host health by modulating gut microbial composition and metabolic activities. However, the influence of oligosaccharides with different glycosidic bonds on intestinal microecology remains unclear, hindering their functional food applicability. This study examined the impact of six disaccharides, including trehalose (α-1,1), maltose (α-1,4), isomaltose (α-1,6), cellobiose (β-1,4), β-lactose (β-1,4), and gentiobiose (β-1,6), at concentrations of 10 mM. The results showed that α-disaccharides (maltose and isomaltose) were metabolized faster than β-disaccharides (cellobiose and gentiobiose). They also significantly increased both bacterial and fungal richness (Chao1 and ACE indexes) and diversity (PD whole tree) compared to β-disaccharides (p < 0.05). Both α- and β-disaccharides significantly enriched Megamonas funiformis and Phocaeicola vulgatus while reducing Klebsiella pneumoniae abundance. Notably, β-disaccharides enhanced Faecalibacterium prausnitzii and Paraprevotella clara proliferation. Despite a less pronounced effect on fungi than bacteria, isomaltose and gentiobiose substantially altered fungal composition by reducing Candida africana abundance and promoting Penicillium citrinum growth. These oligosaccharides promoted complex gut microbial networks, with key taxa including Occultifur kilbournensis, Ruminococcaceae bacterium, and Streptococcus salivarius. Notably, α-disaccharides increased core microbial interactions. The gut microbial composition affected short-chain fatty acids production, with trehalose and cellobiose showing the greatest enhancement. Additionally, β-disaccharides, particularly cellobiose, were more successful in increasing the butyric acid levels than α-disaccharides. Metabolomic profiling indicated that α-disaccharides upregulated antioxidative amino acids (e.g., L-proline) and glycerophospholipids, while β-disaccharides increased delta2-THA, a hepatoprotective fatty acid. This study highlights the differential modulation of gut microbiota and metabolism by disaccharide glycosidic bonds, providing insights into their functional roles.