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Nitrogen is one of the most critical nutrients affecting cell growth and biochemical composition of microalgae, ultimately determining the lipid or carbohydrate productivity for biofuels. In order to investigate the effect of nitrogen sources on the cell growth and biochemical composition of the marine microalga Tetraselmis sp., nine different N sources, including NaNO 3 , KNO 3 , NH 4 NO 3 , NH 4 HCO 3 , NH 4 Cl, CH 3 COONH 4 , urea, glycine, and yeast extract were compared at the given concentration of 8.82 mM. Higher biomass concentration was achieved under organic nitrogen sources, such as yeast extract (2.23 g L-1) and glycine (1.62 g L-1), compared to nitrate-(1.45 g L-1) or ammonium-N (0.98 g L-1). All ammonium sources showed an inhibition of cell growth, but accumulated higher lipids, showing a maximum content of 28.3% in ammonium bicarbonate. When Tetraselmis sp. was cultivated using yeast extract, the highest lipid productivity of 36.0 mg L-1 d-1 was achieved, followed by glycine 21.5 mg L-1 d-1 and nitrate 19.9 mg L-1 d-1. Ammonium bicarbonate resulted in the lowest lipid productivity of 14.4 mg L-1 d-1. The major fatty acids in Tetraselmis sp. were palmitic, oleic, linoleic and linolenic acids, regardless of the nutritional compositions, indicating the suitability of this species for biodiesel production.

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