EFFECT OF DIETARY INCLUSION OF Vibrio proteolyticus AND Shewanella putrefaciens POSTBIOTICS IN JUVENILE GILTHEAD SEABREAM (Sparus aurata)

The most effective way to ensure good health in aquaculture species is through the prevention of potential diseases. To this aim, diverse microorganisms have been investigated and applied as probiotics that are capable of improving the immune system of the animals. Furthermore, in recent years, there has been a surge in the use of postbiotic, bioactive compounds of microbial origin that demonstrated great potential for improving fish health. In this context, there is a need to identify and develop novel postbiotics derived from bacterial extracellular products (ECPs).

This study evaluates the use of a combination of two ECPs, Vibrio proteolyticus (VP) and Shewanella putrefaciens (PDP11), in an in vivo feeding assay, in which these are included at a low concentration (10¹⁰ CFU kg^-1) in an experimental diet for juvenile gilthead seabream (Sparus aurata) against a control feed (CT) without ECPs. Growth, chemical composition and intestinal functionality were evaluated. The results showed no significant differences between the two experimental groups in growth and muscle chemical composition. Otherwise, the study of intestinal functionality evidenced the same tendency, where fish fed both diets presented similar levels of enzymatic activities. It can be concluded that the inclusion of these ECPs did not produce any adverse effects on fish growth, chemical composition of the filet and digestive functionality. Consequently, the combination of both substances could be a potential candidate for a future postbiotic in aquaculture nutrition.