Microbiota Characterization and Bioactive Potential of Broccoli (Brassica oleracea var. italica) By-Products: Implications for Sustainable Antimicrobial Applications

Broccoli (Brassica oleracea var. italica) by-products represent an abundant and underutilized source of bioactive compounds with potential applications in sustainable food systems. This study aimed to characterize the microbiota associated with different plant fractions (leaves, stems, and heads) of broccoli (Parthenon and Tritón cultivars) and to evaluate the antioxidant and antimicrobial properties of their extracts, using cauliflower as a reference. Microbial counts and fungal identification (ITS sequencing) were performed, while phytochemical profiles were analyzed by HPLC-ESI-QTOF. Antioxidant activity was assessed using DPPH and ABTS assays, and antimicrobial activity under in vitro conditions was evaluated against selected foodborne bacteria and phytopathogenic fungi. Broccoli by-products, particularly leaves, showed lower microbial loads in certain cultivars and were rich in phenolic compounds and glucosinolates; however, higher phenolic content did not always correlate with greater antioxidant activity, highlighting the importance of compound composition. All extracts showed strong antibacterial activity at higher concentrations, especially against Listeria spp. Notably, antifungal activity was selective but relevant, with consistent inhibition observed against Alternaria alternata, while Penicillium purpurogenum and Botrytis cinerea exhibited higher resistance. Overall, these findings highlight the potential of broccoli by-products as sustainable sources of natural bioactive compounds for food applications, particularly in the development of preservation strategies and postharvest treatments. Further studies focusing on individual compounds and their specific biological activities are needed to better understand the mechanisms underlying these effects and to support their application in real food systems.