Elucidating the Multi-Biofunctional Roles of Olive Oil By-Products: A Study about Phenolic Profiles, Antioxidant Capacity, Prebiotic Characteristic, and Antimicrobial Activities
The olive oil industry, a cornerstone of Mediterranean agricultural economies, generates substantial by-products such as olive pomace and stones, posing environmental challenges while harboring untapped bioactive potential. This study investigates antioxidant, prebiotic and antimicrobial activities of such by-products and their hydroalcoholic extracts: olive pomace (OP), olive pomace extract (OPE), olive stones (OS), and olive stone extract (OSE). Phenolic composition, assessed by HPLC-DAD/MS, revealed a richer profile and higher levels of phenolics in OPE than in OSE, in agreement with their antioxidant levels, which resulted 56.8% higher in OPE (as Trolox equivalents). Prebiotic activities were investigated with probiotic strains of Lactiplantibacillus plantarum IMC 509® and Lacticaseibacillus rhamnosus IMC 501®, monitoring the growth curves, short-chain fatty acids (SCFAs) production, total phenol content (TPC), and antioxidant levels in the culture fluids supplemented with OP, OPE, OS, OSE. Antimicrobial activities against common gut pathogens, i.e. Escherichia coli, Pseudomonas aeruginosa, Bacillus cereus, and Staphylococcus aureus, were also explored. All substrates supplied favorable conditions for probiotic proliferation. Fermenting fluids from L. plantarum IMC 509® cultured in presence of OP, OPE, OS, and OSE increased significantly SCFAs production, compared to control sample, after 28 hours of fermentation. Fluids supplemented with OP and OPE significantly increased TPC and antioxidant capacity at the end of fermentation for both probiotic strains. Both OPE and OSE revealed inhibitory effects on the investigated pathogens. These findings position olive by-products as valuable resources for sustainable production of functional foods, nutraceuticals, and pharmaceuticals, offering a compelling solution to environmental concerns while unlocking health benefits.