Isolation and Probiotic Characterization of Bacillus stercoris VR19 from the polyherbal Ayurvedic fermented formulation Madhookasavam

The human gut is a bustling ecosystem, home to trillions of microscopic residents that help digest food, train the immune system, and protect against invaders. Among these residents, a specific group known as probiotics—live microorganisms that offer health benefits when consumed in the right amounts—has long been a focus of medical interest. While many people associate these helpful bacteria with yogurt or dairy products, scientists are increasingly looking elsewhere for new strains, particularly in traditional fermented foods and medicines. These ancient preparations often rely on natural fermentation, a process where plants and sugars interact with wild microbes over time, creating complex environments that can nurture robust, resilient bacteria. The question driving recent research is whether these traditional sources hold untapped potential for finding new, effective probiotics that can survive the harsh journey through the human digestive tract and settle in the gut to do good work.

In a recent study, researchers turned their attention to a traditional Ayurvedic medicine called Madhookasavam, a fermented liquid made from flowers of the Madhuka tree, honey, and other herbs like cardamom and sandalwood. This formulation has been used for centuries to support gut health, but its internal microbial world remained largely unexplored. The team set out to isolate bacteria from this liquid and test whether any of them possessed the specific traits required to function as a probiotic. They were not just looking for any bacteria; they needed organisms that could survive the acidic environment of the stomach, withstand the bile salts found in the intestine, and safely colonize the gut without causing harm. From a collection of twenty different bacterial strains they pulled from the medicine, one stood out as a promising candidate.

The researchers named this standout strain VR19. Before declaring it a potential probiotic, they subjected it to a rigorous safety check. They first tested whether the bacteria could destroy red blood cells, a sign of potential danger; VR19 showed no such activity, indicating it was safe. They then exposed it to a battery of common antibiotics, including chloramphenicol and azithromycin, to ensure it would not become a carrier of drug resistance. The strain proved sensitive to all of them, meaning it would not survive if a patient needed to take these medications, a crucial safety feature. With safety established, the team tested its resilience. They placed the bacteria in solutions mimicking the human stomach, ranging from highly acidic to moderately acidic, and found that VR19 survived and grew well, especially in conditions closer to pH 5 and 6. They also challenged it with pepsin, a digestive enzyme, and bile salts, which are found in the small intestine. The bacteria endured these stressors with remarkable ease, maintaining its growth even when exposed to bile concentrations up to 3 percent and salt levels as high as 10 percent.

Beyond mere survival, the researchers wanted to know what VR19 could actually do once it arrived in the gut. They discovered that the strain produces an enzyme called cellulase, which helps break down cellulose, a tough fiber found in plant cell walls. This ability is significant because it suggests the bacteria could help the host digest dietary fibers, potentially feeding other beneficial microbes in the gut. Furthermore, the strain demonstrated a strong capacity to neutralize harmful free radicals, a process known as antioxidant activity. In tests, the bacterial extract scavenged up to 72.9 percent of free radicals, a measure of its ability to reduce oxidative stress, which is linked to inflammation and chronic disease.

To see if these bacteria could actually take up residence in a living organism, the scientists used a tiny, transparent worm called Caenorhabditis elegans as a model. These worms have a simple digestive system that functions similarly to that of larger animals, making them ideal for observing how bacteria interact with a host. The researchers fed the worms the VR19 strain and watched what happened. Over several days, they found that the bacteria successfully colonized the worm's intestine and persisted there, even when the worms were starved of food. The bacteria remained inside the worms in higher numbers than a standard laboratory food source, proving that VR19 could not only survive the journey but also establish a foothold.

Finally, to identify exactly what kind of organism they had found, the team analyzed its genetic code. By sequencing a specific gene known as the 16S rRNA gene, they determined that VR19 belongs to a species called Bacillus stercoris. This is a relatively newly recognized species of bacteria, and while it has been studied for its ability to break down biomass and produce antimicrobial compounds, this study marks the first time it has been isolated from an Ayurvedic formulation and characterized as a potential probiotic. The findings suggest that Bacillus stercoris VR19 combines safety, the ability to survive harsh digestive conditions, and useful functional traits like fiber digestion and antioxidant production. While the researchers caution that further testing in mammals and humans is needed before it can be used as a therapy, the study highlights traditional fermented medicines as a rich, underexplored source of new microbial allies for human health.