Effect of yeast culture supernatant on the probiotic properties and biochemical characteristics of three probiotics, in vitro and in vivo evaluation of yeast-probiotic combination against the pathogen V. anguillarum

Research hypothesis: If yeast and probiotics enhance each other they might provide improved protection against pathogens. Growth, aggregation, biofilm formation and hydrophobicity as well as evaluation, of pH lactic acid, free amino nitrogen and reducing sugars in the growth media were estimated for probiotics in the presence of three ratios of yeast cell free supernatant (CFS). The effect of the best working ratio of each probiotic with yeast in terms of the characteristics examined, on the fish pathogen Vibrio anguillarum properties, namely aggregation, biofilm formation and hydrophobicity, was studied in vitro. Then an in vivo examination on Artemia franciscana nauplii was performed following administration of yeast and probiotic bacteria at the selected ratios and a challenge test with the pathogen to examine any possible protection offered in terms of Artemia survival.