Abstract
Microalgae can use either ammonium or nitrate for its growth and vitality. However, at a certain level of concentration, ammonium nitrogen exhibits toxicity which consequently can inhibit microalgae productivity. Therefore, this study is aimed to investigate the tolerance of Tetraselmis tetrathele to high ammonium nitrogen concentrations and its effects on growth rate, photosynthetic efficiency (Fv/Fm), pigment contents (chlorophyll a, lutein, neoxanthin, and β-carotene), and fatty acids production. Experiments were performed at different ammonium nitrogen concentrations (0.31–0.87 gL−1) for 6 days under a light source with an intensity of 300 μmol photons m−2 s−1 and nitrate-nitrogen source as the experimental control. The findings indicated no apparent enhancement of photosynthetic efficiency (Fv/Fm) at high levels of ammonium nitrogen (-N) for T. tetrathele within 24 h. However, after 24 h, the photosynthetic efficiency of T. tetrathele increased significantly (p < 0.05) in high concentration of -N. Chlorophyll a content in T. tetrathele grown in all of the different -N levels increased significantly compared to nitrate-nitrogen (NO3-N) treatment (p < 0.05); which supported that this microalgal could grow even in high level of -N concentrations. The findings also indicated that T. tetrathele is highly resistant to high ammonium nitrogen which suggests T. tetrathele to be used in the aquaculture industry for bioremediation purpose to remove ammonium nitrogen, thus reducing the production cost while improving the water quality.
Highlights
In recent years, the rising growth and life expectancy of the global population had resulted in increased demand in energy, healthy food, water, drugs, and other resources
Nitrogen is one of the primary essential nutrients required for algal growth and amino acids synthesis which is are the building blocks of proteins, beneficial in the formation of chlorophylls quintessential cellular machinery performing survival tasks, such as photosynthesis, light harvesting, and energy generation in microalgae (Grobbelaar, 2007)
GN1 favored NO−3 where 11-fold significantly enhanced the growth rate compared to NH+4 as a nitrogen source
Summary
The rising growth and life expectancy of the global population had resulted in increased demand in energy, healthy food, water, drugs, and other resources. This has caught the attention of researchers worldwide to study the use of microalgae as a goal toward sustainable development. According to Rahman (2020), there is an increasing demand of microalgaebased products, as the global market for microalgae is projected USD 53.43 billion in the year 2026 as compared to USD 32.60 billion in 2017 These figures show that the microalgae industry is steadily growing and gaining more attention for extensive use in various sectors in the future. Further elucidation of microalgae ammonium nitrogen tolerance is needed, as some previous studies had pointed out that different strains of microalgae require different levels of nitrogen uptake (Raven et al, 1992; Feng et al, 2020)
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