A SHIME®-Based In Vitro Study to Simulate Human Gut Microbiota Modulation by Polyphenols from Pomegranate Juice

Polyphenol-rich pomegranate juice (PJ) has attracted growing interest in its health-promoting properties. However, most studies have focused on purified extracts rather than the whole beverage. Here, we evaluated the effects of whole PJ on gut microbiota composition and functionality using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®). The PJ was characterized by a high polyphenol content (2.3 g/L) and largely dominated by anthocyanins (~98% of identified compounds), with ellagic acid derivatives and flavonols present at lower concentrations. Following 7 days of treatment in the SHIME® model, PJ polyphenols exhibited a bioaccessibility of 20–30%, in agreement with data from the literature. PJ supplementation induced a time-dependent modulation of the gut microbiota, leading to enhanced microbial fermentation and increased SCFA production, particularly in the descending colon, where total SCFA levels surpassed baseline values and reached 100 mmol/L. Moreover, PJ promoted the enrichment of beneficial taxa, including Akkermansia, supporting the ability of the whole juice matrix to improve gut microbial composition and metabolic activity. Overall, these findings support the potential of whole pomegranate juice as a functional food capable of modulating gut microbiota composition and activity.