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International Journal on Algae

ISSN Print: 1521-9429
ISSN Online: 1940-4328

International Journal on Algae

DOI: 10.1615/InterJAlgae.v20.i1.80
pages 85-104

Growth Optimization of the Green Alga Scenedesmus sp. for Biodiesel Production using Response Surface Methodology

F. Malekahmadi
Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
R. A. Khavari-Nejad
Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran
N. Soltani
Department of Petroleum Microbiology, Research Institute of Applied Science, ACECR, Tehran, Iran; Research Institute of Environment and Sustainable Development, DOE, Tehran, Iran
F. Najafi
Department of Plant Sciences, Faculty of Biological Sciences, Khwarizmi University, Tehran, Iran
T. Nejadsattari
Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran

ABSTRACT

Biodiesel is becoming an increasingly attractive fuel due to its environmental benefits and the fact that it is made of renewable resources. Microalgae are a promising alternative source of oil for biodiesel production. In the study, the effects of temperature (25 to 45 °C), nitrogen concentration (0.25-1.5 g·L-1), and pH (5 to 8) on cell growth, lipid accumulation, pigment content, photosynthesis rate, and antioxidant enzymes activities of Scenedesmus sp. were determined. The results indicated that antioxidant enzyme activities increased significantly in comparison to the control at 40 to 45 °C. A significant increase in chlorophyll concentration was found at low pH, nitrate concentration, and temperature. The highest microalgae lipid content (84.86%) was obtained at 30 to 35 °C, pH 5 to 6 and NO3- of 0.875 g·L-1 according to gas chromatography-mass spectrometry (GC-MS) results. On the other hand, the highest yield of fatty acids was achieved at the lowest nitrate concentration, pH 5.5 and 32 °C. In a lipid analysis it was found that palmitic (C16:0) and oleic (C18:1) acids dominantly constituted the algal fatty acids and a much higher content of natural lipid. Lipid production is an important indicator assessing microalga species for biodiesel production. The Chlorophyta, particularly Chlorella vulgaris Beyerinck and Scenedesmus, had the highest growth rates and showed the greatest increase in lipid content in response to nitrogen limitation. Thus Scenedesmus sp. biomass could be used as suitable feedstock for biodiesel production.