Contents lists available at ScienceDirect Agricultural Water Management journal homepage: www.elsevier.com/locate/agwat Ability of marine cyanobacterium Synechococcus sp. VDW to remove ammonium from brackish aquaculture wastewater Piroonporn Srimongkol a , Nuttha Thongchul b,c , Saranya Phunpruch d,e , Aphichart Karnchanatat b,c, ⁎ a Program in Biotechnology, Faculty of Science, Chulalongkorn University, 254 Phayathai Road, Wangmai, Pathumwan, Bangkok 10330, Thailand b Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, 254 Phayathai Road, Wangmai, Pathumwan, Bangkok, Thailand c Research Unit in Bioconversion/Bioseparation for Value-Added Chemical Production, Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, 254 Phayathai Road, Wangmai, Pathumwan, Bangkok, Thailand d Department of Biology, Faculty of Science, King Mongkut’s Institute of Technology, Chalongkrung Road, Ladkrabang, Bangkok, 10520, Thailand e Bioenergy Research Unit, Faculty of Science, King Mongkut’s Institute of Technology, Chalongkrung Road, Ladkrabang, Bangkok, 10520, Thailand ARTICLE INFO Keywords: Ammonium assimilation Glutamine synthetase Glutamate synthase Glutamate dehydrogenase Gene expression Synechococcus sp. VDW ABSTRACT Nitrogen-rich wastewater is a major problem for the aquaculture industry. To investigate whether algae could be used to remove ammonium from brackish shrimp aquaculture wastewater, marine cyanobacterium Synechococcus sp. VDW was cultured in BG11 medium supplemented with Turks Island salt solution and different concentrations of NH 4 Cl (1.0–40.0 mg L -1 ) for 18 days. The cell density of the Synechococcus sp. VDW cultures increased in medium containing between 1 and 10 mg L -1 of NH 4 Cl, while ammonium concentrations greater than 20.0 mg L -1 had a negative effect on growth. Glutamine synthetase and glutamate synthase activities were also examined, and were found to increase with cell density. Meanwhile, glutamate dehydrogenase activity increased in response to high NH 4 Cl concentrations (20.0–40.0 mg L -1 ). The cellular response to ammonium excess was confirmed by measuring gene expression levels using quantitative PCR. Expression of both glnA and gltB was down-regulated compared with the control, while that of gdhA was up-regulated. At an initial con- centration of 1–10 mg L -1 , 98–100% of the ammonium was removed by day 6 of cultivation. Therefore, these findings suggest that Synechococcus sp. VDW can remove ammonium from contaminated brackish water, and may be helpful for improving the quality of aquaculture wastewater. 1. Introduction Thailand is one of the top 15 producers in the aquaculture industry worldwide, and is the largest exporter of crustaceans in South-East Asia (FAO, 2014). A significant problem associated with the growing aqua- culture industry is the high quantity of nitrogenous waste that is produced during protein metabolism by the animals, and from the decomposition of nutrients in the aquaculture ponds. Ammonium levels in aquaculture ef- fluent can vary widely, even in aquaculture source waters. However, le- vels are generally in the range of approximately 1–10 mg L -1 (Chiu-Mei et al., 2016; Gustavo et al., 2006). Ammonium contamination from un- treatedwater causes both environmental and health issues, including eu- trophication and toxic effects on aquatic life (Li et al., 2007). Coastal shrimp farming, producing brackish water effluent, often contributes to the eutrophication of receiving waters (Dierberg and Kiattisimkul, 1996; Paez-Osuna et al., 1998). Elevated concentrations of environmental am- monia have been reported to affect growth, molting, oxygen consump- tion, and reproduction of Penaeus (prawn) species (Chen et al., 1988; Chen and Kou, 1992; Chen and Lin, 1992). Wastewater treatment is essential for enhancing the sustainable aquaculture industry and reducing marine pollution. Various efforts, such as air stripping, chemical precipitation, adsorption, and biological treatment, have been applied to remove ammonium from different types of wastewater (Sarioglu, 2005). Currently, one established tool used in public sewage treatment facilities is biological treatment, which is used for activated sludge. However, this technique requires me- chanical ventilation providing a significant volume of oxygen. It also costs 45–75% of the total energy requisite for a plant (Oilgae, 2010). Besides, waste-activated sludge matching the quantity of wastewater treated is the main derivative of this approach. Thus, considerable https://doi.org/10.1016/j.agwat.2018.09.006 Received 15 March 2017; Received in revised form 19 August 2018; Accepted 2 September 2018 ⁎ Corresponding author at: Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, 254 Phayathai Road, Wangmai, Pathumwan, Bangkok, Thailand. E-mail address: Aphichart.K@chula.ac.th (A. Karnchanatat). Agricultural Water Management 212 (2019) 155–161 Available online 10 September 2018 0378-3774/ © 2018 Elsevier B.V. All rights reserved. T