Abstract
Olive pomace (OP), the solid residue left from olive oil production, is rich in bio-functional compounds, particularly phenolics with well-documented health-promoting properties. However, OP remains largely underutilised, leading to the waste of a valuable food-processing by-product. Its exploitation is further hindered by the inherent chemical instability of phenolic compounds. To address these limitations, we developed a novel nano-encapsulated hydroalcoholic OP extract embedded within a chitosan matrix cross-linked with tripolyphosphate (OPFE-lyo-NPs), a formulation designed to protect bioactive compounds and enhance their targeted delivery to the gut. Using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®), we investigated the impact of OPFE-lyo-NPs and a placebo (lyo-NPs) on gut bacterial communities and their metabolic activity before (T0), after 3 and 10 days of treatment (T3, T10), and 7 days washout (W7). Both formulations increased total short-chain fatty acid (SCFA) production, with OPFE-lyo-NPs inducing higher butyrate levels than lyo-NPs in both proximal (21.68 vs 13.32 mM) and distal colon (24.50 vs 18.81 mM) at T10. Phenolics-loaded nanoparticles promoted a potentially beneficial modulation of the gut microbiota, defined by an increased relative abundance of health-associated taxa such as Lactobacillus and Faecalibacterium, and a shift toward a more butyrogenic profile. While lyo-NPs also enriched several health-associated taxa, OPFE-lyo-NPs uniquely promoted polyphenol-responsive genera with known health benefits and suppressed potentially detrimental genera, including Blautia and Microbacterium. These results suggest that the chitosan-based nanoparticles effectively deliver OP phenolics to the colon, where they exert targeted modulatory effects on the gut ecosystem, supporting potential benefits for host health.