Efficacy of encapsulated yeast (Saccharomyces cerevisiae)against streptococcosis in tilapia

Abstract

S. cerevisiae JCM 7255 from brewing industry was tested to be a possible probiotic candidate in aquaculture together with encapsulation and freeze-drying technique. In vitro viability and morphology analysis of probiotic during storage and during transient with stimulated tilapia gut and bile conditions were evaluated as well as In vivo growth performance efficacy, gut mucosal immune parameters and anti-Streptococcal activity. The In vitro results showed that the viabilities of encapsulated yeasts remained in the high number after storage in room temperature for 14 days, while the viability of free S. cerevisiae could not be detected after 7 days pass. The viability of encapsulated yeast in simulated gastric condition and in tilapia bile was significantly higher than the free non-encapsulated group. The morphology of free S. cerevisiae revealed oval, rough bumpy surface and 2- 4 budding knots with rupture on the surface during incubation in gut and bile conditions. The in vitro anti-streptococcal activity of encapsulated yeast using agar spot test showed inhibitory reaction against 20 from 30 strains of S. agalactiae. The in vivo study showed that supplementation with encapsulated yeast improved the intestinal structure and growth performance in tilapias. A significantly increase number of intraepithelial lymphocytes in proximal intestine were observed while acidophilic granulocytes and mucous cells were not statistically different in any part of the intestine. Lowering the cumulative mortality after oral streptococcal challenge was also observed without statistical significance when compare with control group. The results suggested that encapsulated S. cerevisiae JCM 2755 could be a potential probiotic candidate in tilapia culture.