In-vitro digestion by simulated gastrointestinal juices of Lactobacillus rhamnosus cultured with mulberry oligosaccharides and subsequent fermentation with human fecal inocula

Abstract

In the present study, mulberry oligosaccharides were produced from mulberry polysaccharide by physical ultrasonic hydrolysis, chemical acid hydrolysis and enzymatic hydrolysis. The impact of the oligosaccharides on the growth four probiotic bacteria—Lactobacillus plantarum, Leuconostoc mesenteroides, Lactobacillus casei and Lactobacillus rhamnosuswas examined. The oligosaccharides produced from β-mannanase hydrolysis had the greatest effect on the growth of L. rhamnosus (252% of the number of cells compared with medium without the hydrolyzate). The enzymatically-prepared mulberry oligosaccharides (EMPS) were superior to the untreated mulberry polysaccharide and commercially available prebiotics (isomaltooligosaccharides and galactooligosaccharides). L. rhamnosus was cultured with EMPS and then subjected to tolerance tests with artificial gastrointestinal fluids. Bacteria remained viable. Subsequently, simulated-digested L. rhamnosus cultured with EMPS was used in in vitro fermentation with human gut microbiota from fecal inoculum. After 48 h of the incubation, in the experimental group (with pretreated L. rhamnosus), the ratio of Bacteroidetes to Firmicutes was 0.848, compared with 0.659 in the control group (saline instead of L. rhamnosus), suggesting that L. rhamnosus and constituents in EMPS were capable of regulating the growth of intestinal microorganisms. Our results inform the potential for the development of mulberry oligosaccharides as a prebiotics or synbiotics.