The abundance of genera Oscillibacter and Anaerotruncus was in opposite associated with healthy elder donors. The genus Oscillibacter has been demonstrated to induce remission in ulcerative colitis patients following fecal microbiota transplantation. Furthermore, its levels decrease in individuals consuming a high-fat diet, and this reduction is linked to the development of insulin resistance and gastrointestinal neoplasms. While the genus Oscillibacter may have beneficial functions in healthy elder donors, the abundance of the genus Anaerotruncus appears to be linked to diets rich in saturated fats, obesity, and the development of certain pro-inflammatory diseases. Based on the relevance network analysis, these genera are positively associated with the production of catabolite 399.105@10.4, which was increased by 2.5 times in healthy elder donors compared to the young donors. Our study determined the different fermentation profiles associated with different microbiomes of the young and elder subjects. This could have previously unknown implications for silymarin metabolism, potentially changing its metabolite profile and, consequently, its biological activities.