Spray incorporation of Bacillus subtilis and Saccharomyces cerevisiae with different binding agents into granules for Oreochromis niloticus

In aquaculture, probiotics appear as one of the alternatives to the excessive use of antibiotics. They promote good health, growth and improve the quality of fish culture water. One route of administration is incorporation into foods. But the mode of incorporation influences their viability and density. The objective of this study is to evaluate the effectiveness of incorporation of Saccharomyces cerevisiae and Bacillus subtilis by spraying with three binding agents (sterile salt water 0.9 %, vegetable oil and egg white). After determining the type of interaction existing between the two probiotics, 3×10⁹ CFU of each of them was sprayed onto 30 g of granules. Then, the viability of the incorporated probiotics was evaluated over 12 days and after 60 minutes of residence in water. The density of incorporated probiotics showed a significant difference with vegetable oil in S. cerevisiae for an average of 3.28×10⁷ CFU/g. This density varies from 1.5×10⁶ to 2.75×10⁶ CFU/g with B. subtilis among all binders. For the viability of 12 days, we observe a progressive increase in microbial density with salt water as a binder in B. subtilis from 2.4×10⁴ to 5.35×10⁶ CFU/g and S. cerevisiae of 7.43×10⁶ to 1.5×10⁷ CFU/g. The contact test on water with B. subtilis shows a decrease in microbial density from 3.5×10⁶ to 1.56×10⁶ CFU/g, while with S. cerevisiae it favors an increase from 3.07×10⁷ to 4, 56×10⁸ CFU/g with all binding agents. Sterile salt water 0.9% is the appropriate binding agent for both probiotic strains.