A 71-day study investigated the effects of increasing dietary levels (0, 250, 500, 1000 mg kg feed⁻¹) of a blend of microencapsulated organic acids (citric and sorbic acid) and nature-identical compounds (thymol and vanillin) on growth, intestinal immune parameters, and gut microbiota of European sea bass juveniles under normal and suboptimal conditions (high temperature, low oxygen). The blend did not enhance growth but significantly upregulated IL-8, IL-10, and TGFβ gene expression. Next-generation sequencing revealed prebiotic effects, stimulating beneficial bacteria like *Lactobacillus*, *Leuconostoc*, and *Bacillus*. Suboptimal conditions reduced beneficial bacteria and increased inflammation, effects partially mitigated by the blend.

Serena Busti, Barbara Rossi, Enrico Volpe, Sara Ciulli, Andrea Piva, Federica D'Amico, Matteo Soverini, Marco Candela, Pier Paolo Gatta, Alessio Bonaldo, Ester Grilli, Luca Parma