<scp>GC</scp> – <scp>MS</scp> Analysis and Antiviral Efficacy of <i>Lactiplantibacillus plantarum</i> Postbiotic Extracts Against Infectious Haematopoietic Necrosis Virus

ABSTRACT Infectious haematopoietic necrosis virus (IHNV) causes devastating economic losses in salmonid aquaculture and effective control measures are urgently needed. This study investigates the anti‐IHNV potential of postbiotics derived from Lactiplantibacillus plantarum . The crude postbiotic extract (PBP20o) and a neutralized version (PBP20a) were evaluated for cytotoxicity and antiviral activity in epithelioma papulosum cyprini (EPC) cells. Both extracts exhibited a safe concentration threshold of 1.15 μgmL −1 . Remarkably, treatment with PBP20o and PBP20a at this non‐cytotoxic concentration reduced IHNV titers by 0.82 log₁₀TCID₅₀/ml (84.9%) and 0.46 log₁₀TCID₅₀/ml (65.3%), respectively. The enhanced efficacy of the acidic extract might suggest a dual mechanism involving direct acid‐mediated viral inactivation combined with the action of pH‐stable bioactive metabolites. GC–MS identified three potential antiviral compounds, including such as trans‐cinnamic acid (RT = 33.688, A% = 0.39), pyrrolo[1,2‐a]pyrazine‐1,4‐dione, hexahydro‐3‐(2‐methylpropyl) (RT = 48.516, A% = 13.54) and hexadecanamide (RT = 56.226, A% = 3.11) from L. plantarum postbiotic. This study identifies L. plantarum postbiotics as a novel and promising source of antiviral compounds, offering a potential alternative strategy for mitigating IHNV outbreaks in aquaculture while ensuring biosafety for the target host and end consumers.