AUTHOR=Farahin Abd Wahab , Natrah Ikhsan , Nagao Norio , Yusoff Fatimah Md. , Shariff Mohamed , Banerjee Sanjoy , Katayama Tomoyo , Nakakuni Masatoshi , Koyama Mitsuhiko , Nakasaki Kiyohiko , Toda Tatsuki 

TITLE=Tolerance of Tetraselmis tetrathele to High Ammonium Nitrogen and Its Effect on Growth Rate, Carotenoid, and Fatty Acids Productivity

JOURNAL=Frontiers in Bioengineering and Biotechnology

VOLUME=9

YEAR=2021

URL=https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2021.568776

DOI=10.3389/fbioe.2021.568776

ISSN=2296-4185

ABSTRACT=<p>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 <italic>Tetraselmis tetrathele</italic> to high ammonium nitrogen concentrations and its effects on growth rate, photosynthetic efficiency (<italic>F</italic><sub><italic>v</italic></sub><italic>/F</italic><sub><italic>m</italic></sub>), pigment contents (chlorophyll <italic>a</italic>, lutein, neoxanthin, and β-carotene), and fatty acids production. Experiments were performed at different ammonium nitrogen concentrations (0.31–0.87 gL<sup>−1</sup>) for 6 days under a light source with an intensity of 300 μmol photons m<sup>−2</sup> s<sup>−1</sup> and nitrate-nitrogen source as the experimental control. The findings indicated no apparent enhancement of photosynthetic efficiency (<italic>F</italic><sub>v</sub>/<italic>F</italic><sub>m</sub>) at high levels of ammonium nitrogen (<inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>NH</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>-N) for <italic>T. tetrathele</italic> within 24 h. However, after 24 h, the photosynthetic efficiency of <italic>T. tetrathele</italic> increased significantly (<italic>p</italic> &lt; 0.05) in high concentration of <inline-formula><mml:math id="M2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>NH</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>-N. Chlorophyll <italic>a</italic> content in <italic>T. tetrathele</italic> grown in all of the different <inline-formula><mml:math id="M3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>NH</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>-N levels increased significantly compared to nitrate-nitrogen (NO<sub>3</sub>-N) treatment (<italic>p</italic> &lt; 0.05); which supported that this microalgal could grow even in high level of <inline-formula><mml:math id="M4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mtext>NH</mml:mtext></mml:mrow><mml:mrow><mml:mn>4</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>-N concentrations. The findings also indicated that <italic>T. tetrathele</italic> is highly resistant to high ammonium nitrogen which suggests <italic>T. tetrathele</italic> to be used in the aquaculture industry for bioremediation purpose to remove ammonium nitrogen, thus reducing the production cost while improving the water quality.</p>