Selective Utilization of Human Milk Oligosaccharides 2’-FL and 3-FL by Probiotic Bacteria Resulting in Different Metabolite Production by These Bacteria (P20-012-19)

Abstract

Abstract Objectives Human breast milk contains a high quantity of oligosaccharides (HMOs) which are not digested by infants but are selectively utilized by beneficial gut microbes such as Bifidobacterium species. The gut microbiome in breast-fed infants is dominated by Bifidobacterium species, whereas formula-fed infants have a higher representation of Bacteroides and Enterobacteria species. The aim of this study was to evaluate the ability of various potentially pathogenic bacteria and commercially available probiotic strains to grow using the HMOs 2’-fucosyllactose (2’-FL) and 3-fucosyllactose (3-FL), glucose, lactose or galacto-oligosaccharide (GOS) as a sole carbon source. We also compared the production of short-chain fatty acids (SCFAs) and lactic acid during the fermentation of 2’-FL by B. infantis, B. bifidum and Bacteroides strains. Methods Bacterial growth was monitored by measuring the absorbance at 600 nm every 30 min for 24 h using the automatic Bioscreen© C system under anaerobic conditions in culture media containing 1% 2’-FL, 3-FL, glucose, lactose or GOS as a sole carbon source. Metabolites were analyzed by chromatographic methods in spent culture media after over-night growth of bacterial strains with 1% 2’-FL. Results Only certain bifidobacteria strains, B. infantis and B. bifidum, were able to utilize 2’-FL and 3-FL, whereas other tested Lactobacillus and Bifidobacterium strains as well as pathogenic bacteria grew with all other carbon sources. We also confirmed that Bacteroides fragilis, B. thetaiotaomicron and B. vulgatus strains utilized HMO. Distinct SCFA and lactic acid quantities were observed between Bifidobacterium and Bacteroides strains in 2’-FL fermentation. For instance, acetic and lactic acids were produced at much higher levels in Bifidobacterium than in Bacteroides, and propionic acid was produced at low level only in Bacteroides. Conclusions These results show the selectivity of 2’-FL and 3-FL utilization in certain Bifidobacterium and Bacteroides strains, which is translated to differences in metabolite production between these individual HMO-utilizing bacteria. Further studies will enlighten the role and potential benefits of HMOs as a selective substrate for gut microbes, as well as for competition and cross-feeding of microbial metabolites among gut species. Funding Sources This research was funded by DuPont Nutrition and Health.