Effect of NPK Fertilizer Concentration on Growth and Lipid Accumulation of Picochlorum sp.
Microalgae are known as a major object for second generation biofuels and functional foods due to high lipid content accumulated in cells under different nutrient media. Picochlorum is a small, unicellular, fast growing green microalgae capable of producing high intracellular lipids. Recent studies indicated that Picochlorum accumulated higher lipid content with high percentage of polyunsaturated fatty acids such as arachidonic (AA), eicopentaenoic (EPA), and docosahexaenic (DHA) acid. However, nutrient sources with low cost, especially nitrogen and phosphorus were used to increase biomass and lipid content in Picochlorum cells to increase higher productivity in industrial culture. In this study, a low cost comercial fertilizer, NPK was used as a sourse of nitrogen and phosphorus to attain higher biomass and intracelluclar lipid content of Picochlorum. Picochlorum was cultivated in MD4 medium at different NPK fertilizer concentrations, ranging from 0.05 g/l to 1.0 g/l. The results indicated that various concentrations of NPK fertilizer has signficantly impacted on the growth, photosynthetic pigment compositions, as well as lipid content and profile of the organism. At NPK concentration of 0.1 g/l, the growth of Picochlorum cells was highest with specific growth rate (μ = 0.156 day-1) and cell density (69.5 x 106 cells/ml) after 27 days of cultivation. In addition, higher chlorophyll and carotene content were obtained in cultures grown in MD4 medium containing 0.1 – 0.15 g/L fertilizer. Lipid content per volume of Picochlorum increased, however lipid content per cells was the highest under NPK nutrient starvation after 12 day of cultivation (8.031 pg/cell of day 27). Growth of Picochlorum sp. was inhibited and significantly at fertilizer concentrations of above 0.5 g/L. Therefore, MD4 medium containing 0.1 – 0.15 g/L of NPK fertilizer concentration can be used at Picochlorum growth phase and the condition of NPK starvation can be used as a stress factor for lipid accumulation of Picochlorum cells.
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