Identification and Application of a Probiotic Strain Functioning in Both Ammonia Nitrogen Removal and Vibrio parahaemolyticus Antagonism

Abstract:

Three bacterial strains, 20131023A00, 20131023A01, and 20131023A05, were isolated from shrimp guts and the farming ponds using inorganic selecting medium. When cultured in the liquid selecting medium (pH=7.2) containing 0.12% ammonia nitrogen at 28℃ for 24 h, the ammonia conversion rates of the three strains were (38.9±0.1)%, (43.1±0.4)%, and (49.9±0.5)% respectively. Using the paper disk method, we identified that 20131023A05 was the only strain that antagonized Vibrio parahaemolyticus. We measured the diameters of inhibition zones produced by Strain 20131023A05 on the plates coated with V. parahaemolyticus at the densities of 1.57×105 CFU/cm2, 1.57×104 CFU/cm2, and 1.57×103 CFU/cm2, and the diameters were (9.14±0.05) mm, (11.57±0.03) mm, and (13.59±0.02) mm respectively. It was identified that the strain had the closest genetic relationship with Pseudoalteromonas piscicida according to 16S rDNA sequencing. Marsupenaeus japonicus immersed with Strain 20131023A05 at 2.5×105 CFU/ml showed resistance to intramuscular-injected V. parahaemolyticus and the relative survival rate (RPS) was 35%. We applied strain 20131023A05 at 3.13×104 CFU/ml once every three days as well as brown sugar (70% of diet) every day in the culture water of Litopenaeus vannamei for 60 days. Subsequently the concentration of ammonia nitrogen in the water became significantly lower than the control and other groups. Our results suggested that Strain 20131023A05 could function in both ammonia removal and V. parahaemolyticus inhibition, therefore may have great potentials in shrimp farming industry.