Fig. 5. Comparison of the biodiesel yield between the direct transesterification process and the two step (oil-extraction and transesterification) process of biodiesel conversion. TSBP: biodiesel production using a two-step (oil-extraction and transesterification) process. The transesterification was performed under the following conditions: amount of oil-hexane solution, 12 mL; hexane solution-to-methanol (with 0.5 wt% NaOH) ratio, 6:1; temperature, 45 C; mixing speed, 600 rpm; reaction time, 15 min. DT01: biodiesel production using a direct trans-esterification process was performed under the following conditions: weight of microalgae cake, 2 g; amount of methanol, 12 mL; temperature, 45 C; hexane-to-methanol (with 0.25 wt% NaOH) ratio, 3:1 ; mixing speed, 600 rpm, reaction time,15 min. DT02: biodiesel production using a direct transesterification process performed under the following conditions: weight of microalgae cake, 2 g; amount of methanol, 12 mL; temperature, 45 C; hexane-to-methanol (with 0.5 wt% NaOH) ratio, 3:1; mixing speed, 600 rpm; reaction time, 15 min. DT03: biodiesel production using a direct transesterification process performed under the following conditions: weight of microalgae cake of 2 g, the amount of methanol, 12 mL, the temperature of 45 C, hexane-to-methanol (with 0.5 wt% NaOH) ratio of 3:2 , and the mixing speed of 600 rpm; reaction time, 15 min. DT04: biodiesel production using a direct transesterification process performed under the following conditions: weight of microalgae cake, 2 g; amount of methanol, 12 mL; temperature, 45 C; hexane-to-methanol (with 0.5 wt% NaOH) ratio, 3:3 ; mixing speed, 600 rpm; reaction time, 15 min.