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The cell growth rate and cellular lipid content of microalgae are affected by the nitrogen levels during cultivation. The growth rate and lipid content of marine microalga Tetraselmis sp. was found to increase under nitrate replete conditions, but not under deplete conditions. Thus, in order to enhance the lipid productivity of Tetraselmis sp., a two-stage culture process utilizing nitrate replete condition was applied. When the cells were cultivated in F/2 medium for five days in the first stage, the obtained lipid content and productivity were 22.4% and 26.7 mg L −1 d −1 , respectively. After second stage of cultivation for a further 36 h under nitrate replete conditions with 8.82 mM NaNO 3 , increased biomass concentration of 1.32 g L −1 and lipid content of 30.5% were obtained, with an enhanced lipid productivity of 47.3 mg L −1 d −1 . [ABSTRACT FROM AUTHOR]

Abstract: The influence of monoethanolamine (MEA) as a CO2 absorbent on photoautotrophic culture of CO2-fixing microalgae was investigated. When 300ppm MEA (4.92mM) was added to blank culture medium, the dissolved inorganic carbon and the molar absorption ratio increased to 51.0mg/L and 0.34 , respectively, which was an almost 6-fold increase in CO2 solubility. When free MEA up to 300mg/L was added to a green alga Scenedesmus sp. culture that was supplied 5% (v/v) CO2 at 0.1vvm, both cell growth rate and final cell density were enhanced compared to when no MEA was added. The cell growth rate reached 288.6mg/L/d, which was equivalent to 539.6mg-CO2/L/d as a CO2-fixation rate and enhancement of about 63.0% compared to not adding MEA. Chlorophyll-a content and nitrate consumption rate increased correspondingly. MEA doses higher than 400mg/L inhibited cell growth, probably due to toxicity of the carbamate intermediate. [Copyright &y& Elsevier]