Host-Associated Probiotics: A Key Factor in Sustainable Aquaculture

The aquaculture industry has dramatically developed during the last two decades. However, this development has, in some cases, resulted in environmental degradation, emergence of diseases, and low productivity. The need for improving disease resistance, growth performance, feed efficiency, and safe aquatic production for human consumption has stimulated development and applications of probiotics in aquaculture. Probiotics used in aquaculture include genera of Bacillus, Lactobacillus, Enterococcus, and Carnobacterium, and yeast. However, most of these probiotics are derived from terrestrial sources and not from the environment in which the aquatic animals live or the host animal. The use of "host-associated probiotics" has gained attention, as they offer an alternative strategy within aquaculture, which per se is dependent on the use of terrestrial microorganisms. The benefits of host-associated probiotics include improved growth performance, feed value, enzymatic contribution to digestion, inhibit adherence, and colonization of pathogenic microorganisms in the gastrointestinal tract, increase hematological parameters, and immune response. The present review addressed insight into the application of host-associated probiotics within aquaculture, with special focus on their immunomodulatory and growth enhancing effects. Furthermore, the current review address research gaps and issues that merit further investigations.