Probiotics in aquaculture: mechanisms of action and technological approaches (Part 1)

Abstract

The first part of this review synthesizes current evidence on probiotics as tools for nonspecific prevention of infectious fish diseases and technology-oriented health management in aquaculture. Infectious risks associated with intensive fish production and immunological features of fish that determine the effectiveness of microbiota-oriented interventions are outlined. Feed-based and water-applied probiotics, synbiotics, paraprobiotics, postbiotics, and functional microbial communities used in biofloc systems are reviewed. Major mechanisms of action include competitive exclusion of pathogens, production of antimicrobial metabolites, modulation of intestinal, skin and gill microbiota, strengthening of barrier functions, immunomodulation, improved digestion and feed conversion, and stabilization of the microbiological status of the aquatic environment. Particular attention is paid to probiotic biocontrol of saprolegniosis and other oomycete infections, including the limitations of translating in vitro antagonism into field-level protection. Technological approaches to strain selection, fermentation, stabilization, microencapsulation and delivery through feed or water are summarized. The evidence indicates that probiotics are best regarded as a fundamental background component of fish health and biosecurity programs, whose effectiveness is strongly dependent on strain identity, host species, husbandry conditions and rigorous validation under controlled and production settings.