Coating That Protects Beneficial Bacteria

Coating Protects Beneficial Bacteria

The human gut hosts thousands of bacterial species, and some of these bacteria have potential to treat various gastrointestinal diseases. While some types help combat colon cancer, others may assist in treating or preventing infections such as C. difficile. One of the obstacles in developing these "living biotherapeutics" is that many of the potentially beneficial species are harmed by oxygen, making their production, storage and delivery difficult. MIT chemical engineers have now demonstrated that they can protect these bacteria with a coating that helps them survive the production process. In a study published in the Journal of the American Chemical Society, researchers showed they could apply the coating to an E. coli strain and also to other species that may help digest plant starches. Researchers say the coating could be applied to many other species. Ariel Furst, the Raymond and Helen St. Laurent Career Development Professor of Chemical Engineering and senior author of the new study, says: "We believe this coating can be used to protect almost any type of microbe. We think there are microbes that could help with various diseases and that we can manufacture and preserve them for production." MIT postdoc Gang Fan is the lead author of the study. Pris Wasuwanich, an MIT undergraduate student, and Mariela Rodriguez-Otero, a former MIT Materials Research Laboratory Summer Fellow, are among the paper's other authors.

Protective Coating

Most microbes living in the human gut are anaerobic and have varying degrees of sensitivity to oxygen. While some can tolerate some oxygen, for others it is lethal. This makes it difficult to test their potential as therapeutic treatments for human diseases, because bacteria must be freeze-dried and formulated into capsules to be used therapeutically. In this study, Furst and colleagues decided to test protection by coating anaerobic bacteria with a material made from metal ions and organic compounds called polyphenols. When polyphenols and metal ions are placed in a solution, they form a two-dimensional, lattice-like layer. For this study, researchers used iron, which is safe for human consumption, and three polyphenols, all classified by the U.S. Food and Drug Administration (FDA) as GRAS (generally recognized as safe): gallic acid, tannic acid, and epigallocatechin (EGCG), all of which are found in tea and other plant-based products. When bacteria are also added to the solution, the material self-assembles to form a coating on individual bacterial cells. This coating protects the bacteria during freeze-drying and the production process. Researchers demonstrated that coated cells remained healthy and, despite their growth being temporarily inhibited, could perform normal cellular activities. When exposed to an acidic environment such as the stomach, the coating breaks down and releases the bacteria. Bacterial Colonization One of the strains researchers used to test the coating was Bacteroides thetaiotaomicron. This species, which has enzymes specialized for digesting carbohydrates, appears to be more abundant in the gut microbiome of healthy humans. However, because they are very sensitive to oxygen, it has been difficult to investigate how these bacteria could improve health when delivered as a biotherapeutic. Bacteria with this type of protective coating could also be useful for agricultural applications, such as helping make crop seeds more resistant to stress. Another possible application for the coating is its use in protecting microbes used as vaccines. The BCG vaccine, which consists of a bovine version of the microbe that causes tuberculosis, is difficult to produce and must be stored at low temperatures. Furst says coating with a protective layer could eliminate the need for cold storage and facilitate distribution. "If we can eliminate the need for cold storage and transport, we think this could make many therapeutics more widely available," he says. The research was funded by the MIT Deshpande Center, the Undergraduate Research Opportunities Program at MIT, and the National Science Foundation's MIT Materials Research Laboratory MRSEC Program.

Source:

Materials provided by Massachusetts Institute of Technology. Original written by Anne Trafton. Journal Reference: Gang Fan, Pris Wasuwanich, Mariela R. Rodriguez-Otero, Ariel L. Furst. Protection of Anaerobic Microbes from Processing Stressors Using Metal–Phenolic Networks. Journal of the American Chemical Society, 2021; DOI: 10.1021/jacs.1c09018 Massachusetts Institute of Technology. "A step toward 'living biotherapeutics': Chemical engineers have created a coating for microbes that could make it easier to deploy the organisms to treat gastrointestinal disease." ScienceDaily. www.sciencedaily.com/releases/2021/12/211210093032.htm (accessed 4 January 2022).