National Center of Excellence in Molecular Biology (CEMB)
Abstract
Background: Nitrifying bacteria in aquaculture environments are capable of removing toxic nitrogen compounds such as ammonium and nitrite. Using these indigenous microbial resources can improve shrimp production.Methods: Screening method was used to isolate aerobic strains of nitrifying bacteria. Species identification for these isolates was done by biomolecular method based on 16S rDNA gene sequence. Ammonium, nitrite and nitrate concentrations from the culture were determined by spectrophotometry at the appropriate wavelength. Temperature, pH, dissolved oxygen and salinity were measured by specialized equipment. Formation and development of flocs during shrimp culture were determined based on their volume and weight. A trial of shrimp nursery was carried out on a small scale with 0.5 m3 tanks containing diluted seawater to 16-18‰ salinity at a density of 400 individual/m3 for 24 days on April 2019. Results: This study isolated two strains of Pseudomonas (BF01 and BF03) and one strain of Cupriavidus oxalaticus BF02 from seawater in Thua Thien Hue province, Vietnam. These bacterial isolates have shown ability to remove nitrogen compounds such as ammonium, nitrite and nitrate in culture medium. Formation and development of flocs were found in trials of shrimp nursery with diluted seawater containing the isolates. Some water quality parameters (temperature, pH, dissolved oxygen, salinity, ammonium and nitrite) were kept at a safe level and juvenile shrimp grown normally during culture.Conclusion: The observations on the water quality and basic growth parameters of juvenile shrimp in the two treatments, diluted seawater and diluted seawater with commercial microbial products, showed that there were no significant differences between them with p = 0.05. This proves that three isolates have played an important role in shrimp nursery. Keywords: Cupriavidus oxalaticus; Floc; Litopenaeus vanamei; Nitrifying-denitrifying bacteria; Pseudomonas sp.
