Avaliação in vitro do potencial probiótico de Phaffia brasiliana, desenvolvimento de ração e efeitos in vivo sobre desempenho e saúde de Tilápia-do-Nilo (Oreochromis niloticus) em sistemas de bioflocos e água clara

Abstract

Given the intensification of the production of Nile tilapia (Oreochromis niloticus), and the consequent growing scenario of antimicrobial resistance, the demand for functional alternatives that promote nutritional, physiological, and productive benefits in fish is increasing. In this context, yeasts of the genus Phaffia stand out for their antioxidant properties, ability to modulate the intestinal microbiota, and potential to intensify the natural muscle coloration of these animals with natural pigments, such as astaxanthin. Therefore, this study evaluated the in vitro safety and antioxidant of Phaffia brasiliana strains and analyzed different methodologies for incorporating this microorganism into feed to assess its probiotic potential and health of O. niloticus in biofloc (BFT) and clear water (AC) systems. The three of P. brasiliana strains were found to be safe in vitro, showing no virulence factors and indicating sensitivity to first-line antifungals. They also exhibited strong antioxidant activity, with astaxanthin showing a predominant relative potency (507.2), despite its concentration (6.56%) compared to other antioxidants, such as phytoene (53.95%; potency 208.645). Among the feed preparation strategies, the spray coating method stood out, maintaining microbial concentration during storage and administration in water, while microencapsulation, lyophilization, and spray drying presented several limitations on a small scale, mainly related to insufficient yield. In the in vivo experiment, the fish started the experiment with an average weight of 1.53 g and, after 63 days, reached higher final weights in the AC treatments (p < 0.05) – with yeast (AC-L; 78.99 g) and without yeast (AC-C; 74.90 g) –, while the BFT treatments with and without yeast showed lower values (BFT-L; 59.41 g; and BFT-C; 64.47 g). Feed conversion ranged from 0.79 to 0.82 (AC-L and AC-C) to 0.96 to 0.86 (BFT-L and BFT-C). Furthermore, a positive effect on hematological stress biomarkers was indicated in the AC-L and BFT-L groups (p < 0.05), possibly related to astaxanthin produced by the yeast. Characteristic colonies of P. brasiliana were detected in both sampling collections, indicating survival through processing, storage, and consumption. Analysis of fillet color showed an intensification of the reddish hue (a*) in the AC-L and BFT-L groups when compared to their respective controls, confirming the presence of the administered yeast and absorption of antioxidant pigments. No significant differences were observed between BFT and AC regarding the utilization of the yeast's effects. In summary, P. brasiliana UFMG-CM-Y6497 demonstrated safety and biotechnological potential, with observable benefits in the health and pigmentation of tilapia. Future studies should focus on defining optimal doses, effects dependent on the amount administered, and application in large-scale systems.