Unlocking antimicrobial potential of microalgae on food-borne bacteria: A standardized framework and future directions

• Microalgae represent a source of antimicrobial bioactives. • No antimicrobials from microalgae are currently commercially available. • Microalgal growth, bioactives extraction, and testing choices affect bioactivity. • Standardized framework for bioactivity testing is critically needed. • Future developments lie in the selection of sampling sites, omics and artificial intelligence. Foodborne infections are a global challenge, costing billions annually through food losses, trade restrictions, and healthcare expenses. Growing concerns over chemical antimicrobials such as antibiotics, sanitizers, and disinfectants, have driven interest in sustainable bio-control strategies for food systems. Microalgae, which produce a plethora of biomolecules including carbohydrates, lipids, proteins, and various secondary metabolites, represent a promising source of antimicrobial compounds. Despite numerous reports demonstrating antimicrobial activity in microalgal extracts, no microalgae-derived antimicrobials have yet reached commercialization. This review focuses on some microalgal species already produced at commercial scale, including those with GRAS status (e.g., Chlorella vulgaris and Chlamydomonas reinhardtii ). As for other microalgae-based products (e.g., biofuel oil), successful antimicrobial production depends on identifying key species and strains, optimizing growth conditions, and refining harvesting, cell disruption, and extraction protocols. Although research in this area is expanding, further studies are needed to improve our understanding of antimicrobials synthesis and to assess how these factors influence antimicrobial activity. Commonly used antibacterial assays such as disc diffusion and microdilution have limitations that must be considered when evaluating the antimicrobial activity of microalgal extracts. Overall, inconsistencies in testing and reporting have hindered the clear identification of microalgae as sources of effective antimicrobials. This review proposes a framework for future extract preparation and antimicrobial assessment and discusses future prospects to enhance the discovery and yield of microalgal antimicrobials.