The roles of probiotic purple nonsulfur bacteria to control water quality and prevent acute hepatopancreatic necrosis disease (AHPND) for enhancement growth with higher survival in white shrimp (Litopenaeus vannamei) during cultivation

This study aimed to investigate the potential of a mixed probiotic purple nonsulfur bacteria (PNSB) for controlling water quality and preventing acute hepatopancreatic necrosis disease (AHPND) to promote growth performance and increase survival of white shrimp (Litopenaeus vannamei) in postlarval stage during cultivation. Four probiotic PNSB (Rhodobacter sphaeroides strains SS15, S3W10, TKW17 and Afifella marina STW181) were investigated for controlling water quality using a mixed culture at a ratio of 1: 1 (roughly 1 × 10⁸ cells mL^− 1 for each, every week 1–7) as follows; T1 (S3W10 + SS15), T2 (S3W10 + TKW17) and T3 (S3W10 + STW181) and found that throughout 8 weeks shrimp cultivation the most effective sets to reduce NH₄ ⁺ and promote shrimp growth (based on weight and total length) were T1 and T3, respectively. Hence, PNSB strains (SS15, S3W10 and STW181) were used as a mixed culture (1: 1: 1, roughly 1 × 10⁸ cells mL^− 1 for each at weeks 1, 2 and 3) assessing their potential to prevent AHPND by challenge test on shrimp with a virulent strain AHPND-causing Vibrio parahaemolyticus SR2 (roughly 1 × 10⁵ cells mL^− 1 at day 15) during shrimp cultivation for 30 days. Inoculated PNSB sets (positive control: only PNSB inoculation, and treatment: both PNSB and SR2 inoculations) significantly decreased (P < 0.05) the levels of NH₄ ⁺, NO₂ ⁻, NO₃ ⁻ and chemical oxygen demand (COD) with significantly higher (P < 0.05) of dissolved oxygen (DO) compared to native control (no inoculation) and challenge test (only SR2 inoculation). The maximal growth performance of shrimp was observed in the positive control; while no significant difference (P > 0.05) was observed for other sets. PNSB survived and colonized in intestinal shrimp tract to prevent AHPND by increasing 11% survival rate of infected shrimp by strain SR2. The correlation coefficient between PNSB population and shrimp survival showed a positive strong correlation, but a negative strong correlation between vibrios population and shrimp survival. Overall results proved that a mixed three probiotic PNSB are a good candidate for applying in white shrimp cultivation to maintain water quality and to protect shrimp diseases for promoting shrimp growth with higher survival rate.