Abstract—Microalgae are tiny photosynthetic plants. Nowadays, microalgae are being used as nutrient-dense foods and sources of fine chemicals. They have significant amounts of lipid, carotenoids, vitamins, protein, minerals, chlorophyll, and pigments. Oil extraction from algae is a hotly debated topic currently because introducing an efficient method could decrease the process cost. This can determine the sustainability of algae-based foods. Scientific research works show that solvent extraction using chloroform/methanol (2:1) mixture is one of the efficient methods for oil extraction from algal cells, but both methanol and chloroform are toxic solvents, and therefore, the extracted oil will not be suitable for food application. In this paper, the effect of two food grade solvents (hexane and hexane/ isopropanol) on oil extraction yield from microalgae Dunaliella sp. was investigated and the results were compared with chloroform/methanol (2:1) extraction yield. It was observed that the oil extraction yield using hexane, hexane/isopropanol (3:2) and chloroform/methanol (2:1) mixture were 5.4, 13.93, and 17.5 (% w/w, dry basis), respectively. The fatty acid profile derived from GC illustrated that the palmitic (36.62%), oleic (18.62%), and stearic acids (19.08%) form the main portion of fatty acid composition of microalgae Dunalliela sp. oil. It was concluded that, the addition of isopropanol as polar solvent could increase the extraction yield significantly. Isopropanol solves cell wall phospholipids and enhances the release of intercellular lipids, which improves accessing of hexane to fatty acids. Keywords—Fatty acid profile, Microalgae, Oil extraction, Polar solvent. I. INTRODUCTION ICROALGAE are unicellular photosynthetic microorganisms, living in saline or fresh water and they make algal biomass using sunlight, water, and carbon dioxide [1]. In addition, they are useful in bioremediation applications and also used as nitrogen fixing biofertilizers. Microalgae can provide several different types of renewable biofuels. These include methane produced by anaerobic digestion of the algal biomass; biodiesel derived from microalgal oil, and photobiologically produced biohydrogen [2]. In the industry, microalgae have been used as source for a wide variety of food supplements, pharmacological substances, lipids, polymers, toxins, pigments, enzymes, biomass, wastewater treatment, and ‘‘green energy’’. They are also important in aquaculture as a source of nutrients, production of oxygen, consumption of carbon dioxide, and nitrogen-based compounds [3], [4]. A. Zonouzi, Assistant professor, is with the Department of Biosystem Engineering, Iranian Research Organization for Science and Technology (IROST), Tehran, Iran (e-mail: zenozi@irost.ir). Microalgae have been recognized as a promising alternative source for lipid production [5]–[7]. Several species of microalgae can be induced to produce specific lipids and fatty acids through relative simple manipulations of the physical and chemical properties of their culture medium. Microalgae can accumulate substantial amounts of lipids (approximately 5–50% of dry weight). Lipids can be used as a source for biofuels, as building blocks in the chemical industry and edible oils for the food and health market. One of the bottle-necks in this industry is the lack of a modified and efficient method for extraction of lipid from single cells. Therefore, in this study, the effects of extraction time (20-40 minutes) and type of solvent (Hexane, hexane/isopropanol 3:2 and chloroform/methanol 2:1) on lipid extraction yield from Dunalliela sp. strain M 1 were evaluated. II. MATERIALS AND METHODS A. Microalgae Isolate Preparation The isolate of Dunalliela sp. M 1 isolated from Maharloo Lake of Shiraz was used in this research. This isolate was obtained from the microalgae collection of branch for Northwest & West region, Agriculture Biotechnology Research Institute Iran. B. Microalgae Culturing The isolate was inoculated in sterile glass pot with modified Johansson culture (Fig. 1). Dunalliela sp. has maximum growth rate in temperature ranging from 20 ˚C ~ 30 ˚C and the optimum temperature for this isolate is 26 ˚C [8], [9]. Best light intensity for microalgae growth ranging from 2500 ~ 5000 lux. Light was supplied by fluorescent lamps, and light intensity was set to 4000 lux. For aerating and mixing of culture, a Hailea model 420 air pomp was used. Appropriate pH for microalgae culture is ranging from 7~7.5 [10]. CO 2 cylinder was used to control suitable pH. By injecting CO 2 to the culture, the pH was adjusted on 7.5. Fig. 1 Microalgae culturing After eight days in the logarithmic phase, the culture was scaled up to 20 liters in the transparent PET vessel. Ultimately Oil Extraction from Microalgae Dunalliela sp. by Polar and Non-Polar Solvents A. Zonouzi, M. Auli, M. Javanmard Dakheli, M. A. Hejazi M World Academy of Science, Engineering and Technology International Journal of Agricultural and Biosystems Engineering Vol:10, No:10, 2016 642 International Scholarly and Scientific Research & Innovation 10(10) 2016 scholar.waset.org/1307-6892/10005574 International Science Index, Agricultural and Biosystems Engineering Vol:10, No:10, 2016 waset.org/Publication/10005574