Study on the structure-activity relationship and molecular mechanism of mulberry oligosaccharide EMOS promoting the proliferation of Lactobacillus rhamnose

Lactobacillus rhamnosus (LGG), which has strong colonization ability, is one of the core probiotic bacteria that maintain the structure and function of intestinal flora. It is an important research field of probiotic functional food to explore the regulation factor of LGG proliferation promoting and its mechanism of action from natural plants. Previous studies have found that mulberry oligosaccharide prepared by enzymatic method (EMOS) had significant LGG proliferative activity in vitro, and the proliferative activity was better than that of mulberry oligosaccharides prepared by physical or chemical methods and commercial prebiotics: isomaltooligosaccharide (IMO), galactooligosaccharides (GOS). However the mechanism and structure-activity relationship of EMOS promotive LGG proliferative activity in vitro is unknown. Accordingly, in this project, UPLC/Q-TOF-MS, GC-MS and NMR were used to characterize the physicochemical properties of EMOS oligosaccharide structure and sugar chain structure, and the structure-activity relationship of EMOS-induced LGG proliferation activity was investigated. Based on the RNA-Seq technique, the differentially expressed genes of LGG cultured from EMOS were ascertained from the mRNA transcription level, and qRT-PCR was used to further verify the molecular signaling pathways involved in the regulation of LGG proliferation. UPLC/Q-TOF-MS analyzed the changes of LGG metabolites by EMOS, and the molecular mechanism of EMOS promoting LGG proliferation was elucidated from the levels of gene transcription and metabolic pathway. The research results will provide a theoretical basis for the research and development of mulberry probiotic food.