Efficacy of Single and Multi-Strain Probiotics on In Vitro Strain Compatibility, Pathogen Inhibition, Biofilm Formation Capability, and Stress Tolerance.

Compatibility of each strain in a multi-strain probiotic (MSP), along with its properties, becomes a strong base for its formulation. In this study, single-strain probiotics (SSPs) and multi-strain probiotics (MSPs) were evaluated in vitro for strain compatibility, microbial antagonism, biofilm formation capacity, and stress tolerance. Bacillus amyloliquefaciens L11, Enterococcus hirae LAB3, and Lysinibacillus fusiformis SPS11 were chosen as MSP1 candidates because they showed much stronger antagonism to Aeromonas hydrophila and Streptococcus agalactiae than a single probiotic. MSP 2 candidates were Lysinibacillus fusiformis strains SPS11, A1, and Lysinibacillus sphaericus strain NAS32 because the inhibition zone produced by MSP 2 against Vibrio harveyi and Vibrio parahaemolyticus was much higher than that produced by its constituent SSPs. MSP1 in the co-culture assay reduced (p < 0.05) A. hydrophila count from 9.89 ± 0.1 CFU mL−1 to 2.14 ± 0.2 CFU mL−1. The biofilm formation of both MSPs were significantly higher (p < 0.05) than its constituent SSPs and the pathogens. The SSPs in both MSPs generally showed resistance to high temperatures (80, 90, and 100 °C) and a wide range of pH (2 to 9). This in vitro assessment study demonstrates that MSP1 and 2 have the potential to be further explored as multi-strain probiotics on selected aquatic species.

Effects of Probiotics on Growth, Survival, Water Quality and Disease Resistance of Red Hybrid Tilapia (Oreochromis spp.) Fingerlings in a Biofloc System.

Biofloc technology has shown positive effects in aquaculture, especially on the growth performance of cultured animals. The aims of this study were to evaluate the effects of adding different probiotic strains in a biofloc system on the growth performance and disease resistance of red hybrid tilapia (Oreochromis spp.). Three different probiotics (Lysinibacillus fusiformis SPS11, Bacillus amyloliquefaciens L9, and Enterococcus hirae LAB3), commercial probiotics (MG1) and a mixed probiotics (MP) combining all three strains were used in this study. The in vitro assay results showed that the mixed probiotic (MP) was able to inhibit the growth of Streptococcus agalactiae and Streptococcus iniae significantly compared to the single and commercial probiotic. The efficacy of MP was further tested in in vivo tilapia culture challenged with S. agalactiae. The best specific growth rate (3.73 ± 0.23% day-1) and feed conversion ratio (0.76 ± 0.04) were recorded in the group of biofloc with addition of MP. After being challenged with S. agalactiae, the group of biofloc with MP had significantly higher survival (83 ± 1.43%) compared to the other groups. Furthermore, the nitrogen concentration (NO2-N and NH4-N) was significantly lower in all the biofloc groups compared to the control. Hence, the addition of probiotics was able to provide beneficial effects to red hybrid tilapia culture in the biofloc system.