Many scientists are paying new attention to prebiotics, as they may promote the growth and health of beneficial microorganisms in the intestines, according to nutritional microbiologist David Sela at the University of Massachusetts Amherst. In a new study, he and colleagues reported on evidence that certain beneficial gut bacteria are able to grow when fed a carbohydrate found in cranberries, and that they exhibit a special non-typical metabolism.

Findings could add value to future food products or lead to a new supplement based on the cranberry, of which Massachusetts is a major producer. Details were published in Applied and Environmental Microbiology.

What we eat not only nourishes us but also feeds the beneficial bacteria, the microbiome, in our intestines, Mr. Sela pointed out, and food scientists are increasingly interested in these less obvious benefits of food. There are thought to be as many bacterial cells in the bodies as are human cells, “so we’re basically eating for two. These gut bacteria are extremely significant to us, they really are very important. Our food makes a difference for us as well as the beneficial microbes that we carry around with us.”

Further, “a lot of plant cell walls are indigestible,” he said, “and indeed we cannot digest the special sugars found in cranberry cell walls called xyloglucans. But when we eat cranberries, the xyloglucans make their way into our intestines where beneficial bacteria can break them down into useful molecules and compounds.”

Using the model beneficial bacterium bifidobacteria, Mr. Sela, an expert in the human gut microbiome, and colleagues tested the hypothesis that cranberries, a research topic at UMass Amherst for more than 60 years, might be a candidate for a new supplement to boost gut health. To obtain a supply of purified xyloglucan for these experiments, he enlisted help from Ocean Spray, Inc., which provided the original research material, and collaborating experts David Rowley and Jiadong Sun at the University of Rhode Island (URI).

Mr. Sela and his PhD student and first author Ezgi Özcan could then feed this purified plant sugar as the only carbohydrate available to the bifidobacteria living in 96-well plates in an anaerobic environment in the laboratory.

Bifidobacteria are found in adults to some degree but the highest concentrations are found in the gut microbiome of newborn, breast-fed babies, Mr. Sela said. This study provides the first evidence that certain bifidobacteria do consume xyloglucans, and the ones that do exhibit a special metabolism that is not typical. Specifically, these bifidobacteria produce formic acid while consuming xyloglucans and less lactic acid than is typically secreted.

It is not clear yet what the impacts to health are, but the authors suspect this unusual production has implications for the rest of the microbial community in the gut. “This is not traditional food science,” said Mr. Sela, a food scientist who has adjunct appointments in microbiology at UMass Amherst and in microbiology and physiological systems at UMass Medical School. The work was supported by a $64,000 grant from Ocean Spray, Inc. to Mr. Sela and $25,000 from the President’s Enhancement Fund at the Graduate School of the University of Massachusetts Amherst.

Mr. Sela believes there is stronger motivation for both researchers and consumers in studying prebiotics than probiotics. “With probiotics, we are taking extra doses of beneficial bacteria that may or may not help our gut health,” he said. “But with prebiotics, we already know that we have the beneficial guys in our guts, so let’s feed them. Let’s give them more nutrients and things that they like.”

“Prebiotics and probiotics might interact with our own physiology to help balance the microbiome, and we already know that when things are not in balance you can get problems like inflammation. Underlying chronic inflammation can lead to or worsen many different medical conditions. That’s the health side of this kind of study of microbiology, food and health.”

He suggested the next series of studies might look at the interaction of cranberry xyloglucans with other bacterial species and strains. Mr. Sela is also interested in other cranberry molecules interacting with bifidobacteria and other members of the gut microbiome. “We also found certain genes turned on that are consistent with xyloglucan metabolism,” Mr. Sela noted. “This is another good place to pursue our findings further.”