RESUMO
Probiotics face harsh conditions during their transit through the gastrointestinal tract (GIT) of fish because of low-pH environments and intestine fluid. Therefore, the evaluation of probiotic viability under simulated gastrointestinal conditions is an important step to consider for probiotic supplementation in fish feed prior to in vivo trials. Therefore, this study aimed to evaluate the effect of stomach and intestinal simulated conditions on the viability of encapsulated Lactococcus lactis A12 using an in vitro digestion model for tilapia. A Box Behnken design was used to evaluate the potential effect of three factors, namely stomach pH, residence time in the stomach, and enzyme quantity, on the viability of encapsulated Lactococcus lactis A12. As the main results, low pH (4.00), long residence time (4 h), and enzyme quantity (2.68 U of total protease activity) led to lower final cell counts after the phases of the stomach and intestine. Encapsulated probiotic bacteria showed higher viability (p < 0.05) and antibacterial activity (p < 0.05) against the pathogen Streptococcus agalactiae than non-encapsulated bacteria. The results suggest that L. lactis A12 survives in GIT conditions and that the proposed in vitro model could be used to explore the viability of probiotic bacteria intended for fish feed supplementation.
RESUMO
BACKGROUND: Probiotics are viable microorganisms that when administered in adequate amounts confer health benefits to the host. In fish, probiotic administration has improved growth, and immunological parameters. For this reason, it is necessary production of probiotic bacteria, however, commercial culture mediums used for probiotic growth are expensive, so the design of a "low" cost culture medium is necessary. Therefore, this research aimed to produce a potential multistrain probiotic preparation composed of L. lactis A12 and Priestia species isolated from Nile tilapia (Oreochromis niloticus) gut using an agro-industrial by-products-based culture medium. RESULTS: A Box-Behnken design with three factors (whey, molasses, and yeast extract concentration) was used. As the main results, a high concentration of three components enhanced the viability of L. lactis A12, however, viable cell counts of Priestia species were achieved at low molasses concentrations. The Optimal conditions were 1.00% w/v whey, 0.50% w/v molasses, and 1.50% w/v yeast extract. L. lactis A12 and Priestia species viable counts were 9.43 and 6.89 Log10 CFU/mL, respectively. L. lactis A12 concentration was higher (p < 0.05) in the proposed medium compared to commercial broth. CONCLUSIONS: It was possible to produce L. lactis A12 and Priestia species in co-culture conditions. Whey and molasses were suitable components to produce the multistrain preparation. The cost of the proposed culture medium was 77.54% cheaper than the commercial medium. The proposed culture medium could be an alternative to commercial mediums for the production of this multistrain probiotic.
