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In this study, we evaluated the effect of probiotic bacteria Pediococcus pentosaceus supplemented at different inclusion levels in a control diet [basal diet containing 0.5% fructooligosaccharide (FOS)] on the growth performance, feed conversion ratio, immune response, and the disease resistance of whiteleg shrimp Litopenaeus vannamei juveniles against Vibrio parahaemolyticus. A control diet with 0.5% FOS but without P. pentosaceus supplementation (Control) was prepared. In addition, three other test diets were also formulated: control diet supplemented with P. pentosaceus at (i) 1 × 106 cfu g–1 diet (P1), (ii) 1 × 107 cfu g–1 diet (P2), or (iii) 1 × 108 cfu g–1 diet (P3). After a 60-day feeding trial, the experimental shrimps were challenged with V. parahaemolyticus. The results showed that dietary supplementation of P. pentosaceus significantly improved the growth performance and immune responses of L. vannamei juveniles. The juveniles that were fed with a P2 or P3 diet recorded the maximum increase in the final body weight, final length, weight gain, and survival rate. The total hemocyte counts, phenoloxidase, and lysozyme activity of shrimp fed with either of these two diets were significantly enhanced. The results also showed that juveniles fed with a P2 or P3 diet exhibited significantly lower mortality when challenged with V. parahaemolyticus. Overall results suggested that a combination of P. pentosaceus at the inclusion level of 1 × 107 cfu g–1 diet (P2) and 0.5% FOS could be considered as a potential synbiotic formulation for improving the growth, health, and robustness of L. vannamei.

Background and Objective: Production of gamma-aminobutyric acid has recently much interested because of its benefits for health. The objective of this study was to optimize y-aminobutyric acid production by a novel identified Lactiplantibacillus pentosus isolated from a fermented shrimp paste of ruoc. Material and Methods: A species of lactic acid bacterial was isolated from 'ruoc', a highsalt fermented shrimp paste and identified using matrix-assisted laser desorption/ionizationtime of flight mass spectrometry. The gamma-aminobutyric acid production was optimized using various culture conditions (initial cell density from 5 x 10(5) to 5 x 10(7) CFU ml(-1), monosodium glutamate concentration of 0.5-2% (w v(-1)), initial pH of 4-9, incubation temperature of 30-50 degrees C and incubation time of 24-120 h) with one-factor-at-a-time approach. Results and Conclusion: Of 20 lactic acid bacteria isolated from 'ruoc', four isolates of R1, R3, R12 and R13 produced significant quantities of gamma-aminobutyric acid. Isolate R13 produced the highest gamma-aminobutyric acid quantity, identified as Lactiplantibacillus pentosus using matrix-assisted laser desorption/ionization-time of flight mass spectrometry. A culture media optimization study was carried out for Lactiplantibacillus pentosus R13 to improve its gamma-aminobutyric acid yield. Results showed that at optimal conditions of 1.5% monosodium glutamate (w v(-1)), initial pH of 7, initial cell density of 5 x 10(6) CFU ml(-1), cultivation temperature of 45 degrees C and fermentation time of 96 h, Lactiplantibacillus pentosus R13 produced 23.34 mM +/- 0.11 of gamma-aminobutyric acid. In conclusion, gamma-aminobutyric acid production by this isolate was verified to be heavily dependent on monosodium glutamate concentration, initial cell density, initial pH, incubation temperature and fermentation time.