Synergistic Fermentation of Pomegranate Peel Extract by Leuconostoc mesenteroides and Pediococcus pentosaceus for Simultaneous Ellagic Acid Enhancement and Probiotic Enrichment

<ns3:p> Abstract* Background Pomegranate peel is a valuable, nutrient-rich agro-industrial byproduct containing bioactive ellagitannins with limited bioavailability. Biological fermentation, particularly synergistic co-culturing, is a powerful bioprocess for enhancing the nutritional and functional properties of plant matrices. This study aimed to maximize the ellagic acid content of Pomegranate Peel Extract (PPE) by exploiting synergistic fermentation using <ns3:italic>Leuconostoc mesenteroides</ns3:italic> and <ns3:italic>Pediococcus pentosaceus</ns3:italic> , while simultaneously enriching the extract with viable probiotic biomass. Methods Aqueous PPE was subjected to three fermentation treatments: single-strain <ns3:italic>L. mesenteroides</ns3:italic> , single-strain <ns3:italic>P. pentosaceus</ns3:italic> , and a synergistic co-culture of both strains, alongside a non-inoculated control. Samples were incubated anaerobically at 30°C for 72 hours. Analytical parameters included pH, total phenolic content (TPC) via the Folin-Ciocalteu reagent, and antioxidant properties via the FRAP assay. Sugar consumption, lactic acid production, and ellagic acid content were quantified using High-Performance Liquid Chromatography (HPLC). Microbial viability was determined using the standard plate count method. Results During the first 30 h, the pH values of all inoculated fermentations decreased significantly, and the LM+PP culture showed the lowest final pH (~2.0). All inoculated samples showed a significant increase in total phenolic content (TPC), but the mixed culture showed the most noticeable enhancement. The mixed culture showed the highest glucose depletion (68%), surpassing PP (58%) and LM (43%). It exhibited the most extensive glucose depletion, with concentrations decreasing from 180 mg/L at 0 h to 58 mg/L at 72 h, which corresponded to a 68% reduction. In contrast, the PP culture achieved 76 mg/L at 72 h (58% reduction), whereas LM displayed the slowest utilization rate, reaching 102 mg/L (43% reduction) over the same period. Conclusion Synergistic fermentation serves as an effective biotransformation method for converting pomegranate polyphenols into free ellagic acid. Additionally, this process successfully enriches the extract with viable probiotics, enhancing its functional and nutritional value. </ns3:p>