Enhancement of biodiesel production from local isolates of microalgae

Ten microalgae isolates were isolated from some ponds and Tigris River in Iraq, and screened for growth and lipid production. The results showed that the isolates Chrococcus dispersus, Anabaena augstumalis and Chlorella vulgaris exhibited higher growth rate and lipid production and reached (0. 95, 1. 9 and 1. 17) g / l, respectively. The selected isolates stimulated by studying the effect of different levels of pH and salinity on growth and lipid production. The results showed higher lipid production by C. vulgaris reached maximum (3.45g/l) at lower pH 6, followed by A. augstumalis (2. 75g / l at pH11) and C. disperses (2. 68 g / l at pH9). The results also showed that lipid production by C. dispersus and A. augstumalis was stimulated by decreasing salinity concentration and reached maximum (2. 94 and 2. 5 g / l), respectively at 0. 4 g/l of NaCl. While, maximum lipid production by C. vulgaris was (1. 72 g / l) obtained at salt concentration of 1g/l. The combined effect of pH and salinity on lipid production studied. Maximum lipid production by C. dispersus (8. 43 g / l) observed at (pH9 + salt 0. 4g/l). In case of C. vulgaris, total lipid production reached 4. 43g / l which obtained at (pH6 + salt 0. 75g / l). While, lipid production in microalgae of A. augstumalis was favored by alkaline condition, and maximum lipid production (4. 42 g / l) observed at (pH11 + salt 0. 75g / l). Higher oil content was observed in C. vulgaris and reached 33. 2 % (0. 332 g of oil / g of dry algal biomass) when the microalgae cultivated at (pH9 + salt 0. 4 g / l). In comparison, to lower oil content (%) observed with A. augstumalis and C. dispersus reached to 16 % and 13. 8 % when the isolates stimulated at (pH11 + salt 0. 4 g / l) and (pH 6 + salt 0.75 g / l), respectively. Analysis of lipid content by GC technique had shown that the lipid content of microalgae C. dispersus contained only stearic acid. While, oil content in C. vulgaris and A. augstumalis contained only stearic acid, but palmtic acid and oleic acid were detected in control and stimulus conditions.