In this study, the potential value of dried grape pomace (whole, seed, and skin) obtained from Fetească Neagră (FN) and Tămâioasă Românească (TR) as a source of secondary metabolites was evaluated following hydroethanolic extraction. The total polyphenol, flavonoid, and anthocyanin contents of FN and TR extracts have been determined, along with their antioxidant and antimicrobial activities. The investigation of seeds and the whole pomace FN extracts revealed higher levels of polyphenol, flavonoid, and anthocyanin content in comparison to those extracted from TR. Fifteen polyphenolic compounds were identified through ultra-high-performance liquid chromatography (UHPLC) analysis. The most abundant concentrations of catechin and epicatechin were detected in seed and whole pomace extracts derived from both Romanian grape varieties. The antioxidant activity was higher in the whole pomace and skin extracts derived from FN than those derived from TR. The antimicrobial evaluation demonstrated that 15 out of 18 reference pathogenic bacteria exhibited low MIC and MBC values, indicating a strong antibacterial activity of FN and TR extracts. No anti-Candida activity was observed. It can be reasonably deduced that the Fetească Neagră and Tămâioasă Românească by-products represent a sustainable resource for the development of new functional ingredients for the pharmaceutical and food industries, in alignment with the principles of the circular bioeconomy.

The rising threat of antimicrobial resistance (AMR) has driven the search for safe and effective alternatives to conventional antibiotics. This study investigated the probiotic potential and postbiotic properties of Enterococcus faecium (one strain), Pediococcus acidilactici (five strains), and Pediococcus pentosaceus (five strains), identified by 16S rRNA sequencing. Among the strains, Pediococcus pentosaceus MI124 and Pediococcus acidilactici MI129 demonstrated robust survival under simulated gastrointestinal conditions. Cell surface analyses revealed strong auto-aggregation and hydrophobicity in selected strains, notably P. pentosaceus MI124 and P. acidilactici MI127. Enzymatic profiling revealed potential complex metabolic capabilities across different strains. Safety assessments confirmed the absence of hemolytic and gelatinase activities across all strains. Antibiotic susceptibility testing showed resistance to certain β-lactams, while susceptibility to chloramphenicol and tetracycline varied. All LAB strains demonstrated high freeze-drying survivability, exceeding 78.69%. The antibacterial activity of CFSs was confirmed against 14 Gram-positive and Gram-negative pathogens, with results supporting their potential as antimicrobial agents. The CFSs demonstrated a higher total phenolic content (TPC) and displayed significant antioxidant activity, while the total flavonoid content (TFC) remained consistent across most strains. An FTIR spectral analysis confirmed the presence of key functional groups associated with phenolics, organic acids, and peptides, indicating a complex biochemical profile. Probiotics and their postbiotic derivatives offer promising health benefits, including pathogen inhibition and immune modulation. These findings highlight several LAB strains with promising probiotic traits and postbiotic efficacy, supporting their potential use in functional foods and therapeutic applications.