Abstract:Galactomannan boasts the function of regulating the composition of intestinal microbiome and improving metabolic diseases.However，the mechanisms of its low molecular weight products in increasing the abundance of bifidobacteria in the intestine and improving obesity are not clear.In this study，low molecular weight（2 kDa-10 kDa）galactomannan polysaccharides（GMPS）were obtained from guar gum by enzymatic hydrolysis.The monosaccharide composition of GMPS was mannose（M）and galactose（G）（mol/mol，M∶G=1.75∶1）.Subsequently，the effect of GMPS on the diversity and composition of the intestinal microbiota of obese mice was explored through an in vitro simulated intestinal fermentation model with high-throughput sequencing technology.The potential target strains were selected by 16S rDNA identification and BOX-PCR from the feces samples.The intervention of GMPS promoted the production of short-chain fatty acids including acetic acid and propionic acid and regulated the composition of the intestinal microbiota of obese mice significantly increasing the abundance of lactic acid-producing bacteria including Enterococcus and Bifidobacterium，and reducing the abundance of disease-causing bacteria such as Clostridium and Aeromonas（p＜0.05）.Bifidobacterium pseudolongum became one of the dominant strains after the treatment of GMPS.Finally，five B.pseudolongum strains were selected from the samples，demonstrating B.pseudolongum was a characteristic species highly responsive to GMPS.This study explored the effect of GMPS on the intestinal flora of obese mice and proposed a potential target strain（B.pseudolongum），which provides a basis for the deep research of GMPS and B.pseudolongum，and contributes to the development of novel synbiotic products.