Skip to main content
ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Dairy and Functional Foods Research » Research » Research Project #439225

Research Project: In vitro Human Gut System: Interactions Between Diet, Food Processing, and Microbiota

Location: Dairy and Functional Foods Research

2023 Annual Report

1. Following consumption of milk, lactose, a disaccharide of glucose and galactose, is hydrolyzed and absorbed in the upper gastrointestinal tract. However, hydrolysis and absorption are not always absolute, and some lactose will enter the colon where the gut microbiota can consume lactose. Yet the effect of lactose on the gut microbial community, which is a known contributor to human health, was unclear. To address this gap in knowledge, ARS scientists in Wyndmoor, Pennsylvania, applied a short-term, in vitro culturing strategy where the gut microbiota of eighteen donors were cultured with and without lactose, and the data compiled to identify donor-independent responses to treatment. The results found that lactose mediated the gut microbiota in a donor-independent manner that was consistent with other described prebiotics, increasing levels of the health-associated microbe Bifidobacterium and stimulating short chain fatty acid production. Together, these results provided further insight into how dietary milk consumption promotes human health through modifications of the gut microbiome.

2. Lacticaseibacillus rhamnosus strain GG (LGG) is commonly used and sold as a probiotic, and there are health benefits associated with its presence in the gut microbial community. However, it is not well known how LGG travels through the gut, how long a treatment dose may last, and what other benefits might be conferred due to its use. Aiming at resolving this issue, ARS scientists in Wyndmoor, Pennsylvania, designed and performed an in vitro experiment to understand the ability of LGG to persist within an established gut microbial community and determine how LGG can change the function of said community. This work found that LGG persists within the in vitro gut microbial community for at least 7 days after introduction, with little to no additional effects and that the presence of LGG within the gut promotes the production of tryptophan-pathway metabolites such as indole propionic acid. These findings were true across multiple donor communities, indicating that the health benefits associated with LGG are likely due to its ability to engraft into the gut microbial community and adjust metabolic functions.

3. Fructooligosaccharides (FOS) are carbohydrates found in many vegetables (chicory root, onions, garlic, etc.) and are often used as a prebiotic. FOS has been previously demonstrated to increase Bifidobacterium within the gut microbiota, a beneficial microbe that is often more prevalent in children and young people. In this study, ARS scientists in Wyndmoor, Pennsylvania, collaborated with an international research team to use a new short-term culturing method to understand how FOS changes the gut microbiota of different age groups. In this study, donors ranged in age from 25-70, and were separated into young adult, adult, and older adult age groups. The results of this study found age-specific changes in the gut microbiota in response to FOS treatment, demonstrating that different members of Bifidobacteria become more critical in metabolic pathways related to the breakdown of carbohydrates at different age groups. These results demonstrate that FOS can be a useful prebiotic at any age group.

4. Pectins are plant polysaccharides consumed as part of a diet containing fruits and vegetables. Inside the gastrointestinal tract, pectin cannot be metabolized by the mammalian cells but is fermented by the gut microbiota in the colon with the subsequent release of short-chain fatty acids. Previous reports on the prebiotic effects of pectin have produced inconsistent results, most likely due to differences in the pectin chemical structure. To address this gap in knowledge, ARS scientists in Wyndmoor, Pennsylvania, applied an in vitro model to evaluate the effects of two structurally different lemon pectins on the gut microbiota of two donors. The results found that both lemon pectins were able to alter community structure and enhance levels of short-chain fatty acids. Together, these data provide valuable information linking chemical structure of pectin to its effect on the gut microbiota structure and function, which is important to understanding its prebiotic potential.

Review Publications
Mahalak, K.K., Firrman, J., Narrowe, A.B., Hu, W., Bittinger, K., Moustafa, A., Liu, L.S. 2023. Fructooligosaccharides (FOS) differentially modifies the in vitro gut microbiota in an age-dependent manner. Frontiers in Nutrition.
Firrman, J., Liu, L.S., Mahalak, K.K., Tu, V., Tanes, C., Bittinger, K., Bobokalonov, J., Mattei, L., Zhang, H., Van Den Abeele, P. 2022. The impact of environmental pH on the gut microbiota community structure and short chain fatty acid production. FEMS Microbiology Ecology. 98(5).
Mahalak, K.K., Firrman, J., Bobokalonov, J., Narrowe, A.B., Bittinger, K., Daniel, S., Tanes, C., Mattei, L., Zeng, W., Soares, J.W., Kobori, M., Scarino Lemons, J.M., Tomasula, M.M., Liu, L.S. 2022. Persistence of the probiotic Lacticaseibacillus rhamnosus strain GG (LGG) in an in vitro model of the gut microbiome. International Journal of Molecular Sciences.
Liu, L.S., Narrowe, A.B., Firrman, J., Mahalak, K.K., Bobokalonov, J., Scarino Lemons, J.M., Bittinger, K., Daniel, S., Tanes, C., Mattei, L., Friendman, E., Soares, J.W., Masuko, K., Zeng, W., Tomasula, M.M. 2023. Lacticaseibacillus rhamnosus strain GG (LGG) regulate gut microbial metabolites, an in vitro study using three mature human gut microbial cultures in a simulator of human intestinal microbial ecosystem (SHIME). Foods.