School of Medicine

Gut bacteria mine dietary fiber to release beneficial nutrients

Human gut microbes can extract beneficial nutrients from fiber byproducts that would be otherwise lost as waste, such as the pulp discarded after orange juice production. A new study from Washington University School of Medicine in St. Louis found that the fiber byproduct of orange juice manufacturing contains a molecule similar in structure to serotonin, but it is locked away in the fiber. The molecule, when liberated by specific gut bacteria, shows beneficial metabolic effects in mice. (Photo: Getty Images)

A new study from Washington University School of Medicine in St. Louis demonstrates that certain human gut microbes can mine dietary fiber to extract nutrients that otherwise would remain inaccessible to the human body. The study, published June 27 in the journal Cell, illustrates how the fiber byproducts of food production — such as rinds, peels and seeds of fruits and vegetables — may be an untapped source of beneficial biomolecules that contribute to human health.

Many factors, including population growth, climate change, and the societal disruptions caused by the COVID-19 pandemic have focused attention on food production. This includes consideration of the massive amount of waste generated during food manufacturing and the potential nutritive value of what is normally discarded. The composition of fibers present in these byproduct streams reflects their different sources as well as the different types of steps applied during food manufacturing.

“These byproduct streams could represent a sustainable and scalable source of previously uncharacterized biomolecules, and of known biomolecules that are otherwise difficult to obtain in quantity,” said senior author Jeffrey I. Gordon, MD, the Dr. Robert J. Glaser Distinguished University Professor and director of the Edison Family Center for Genome Sciences & Systems Biology. “For example, about 140 million tons of citrus were produced in the world in 2020. Only about half of the total weight of processed fruits is used in the production of juices, with tens of millions of tons of citrus product waste generated annually. We turned to our gut microbes as ‘master biochemists’ and asked what types of normally inaccessible biomolecules are they able to liberate, or mine, from these fibers.”

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