Enriched microbial communities for ammonium and nitrite removal from recirculating aquaculture systems

Area of Science:

• Environmental microbiology
• Aquaculture science
• Biotechnology

Background:

• Aquaculture systems require efficient removal of ammonium and nitrite to maintain water quality.
• Traditional biofilters often face limitations in nitrogenous waste removal efficiency, especially under varying temperatures.
• Ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) are key players in nitrification processes.

Purpose of the Study:

• To enrich and select high-performance microbial communities for enhanced ammonium and nitrite removal in aquaculture biofilters.
• To evaluate the impact of temperature adaptation on the activity and gene expression of AOB and NOB.
• To identify microbial species responsible for superior nitrification performance and ensure the absence of pathogens.

Main Methods:

• Enrichment of AOB and NOB from diverse environmental water samples.
• Selection and temperature adaptation (9°C, 15°C, 25°C, 30°C) of microbial communities.
• Measurement of nitrification gene expression (AMO, NXR) and 16s rRNA sequencing for species identification.
• Assessment of ammonium and nitrite removal efficiency and pathogen screening.

Main Results:

• Microbial communities dominated by Nitrosomonas oligotropha and Nitrobacter winogradskyi exhibited the highest ammonium and nitrite removal rates across all tested temperatures.
• These selected communities showed significantly higher expression of ammonia monooxygenase (AMO) and nitrite oxidoreductase (NXR) genes.
• A notable improvement of 288% in ammonium removal and 181% in nitrite removal was achieved at 9°C compared to commonly used communities.
• No pathogenic bacteria were detected in the enriched microbial communities.

Conclusions:

• Enriched microbial communities, particularly those containing Nitrosomonas oligotropha and Nitrobacter winogradskyi, offer superior nitrification performance for aquaculture biofilters.
• These findings demonstrate a significant potential for improving water quality in recirculating aquaculture systems (RAS) through targeted microbiome selection and enrichment.
• The developed microbial consortia provide a robust solution for efficient nitrogen waste management, even under suboptimal temperature conditions.