Himan Abdollazadeh - Sharif University of Technology, Petroleum and Chemical Engineering Department, Tehran, Iran.
Manouchehr Vosoughi - Sharif University of Technology, Petroleum and Chemical Engineering Department, Tehran, Iran.
Iran Alemzadeh - Sharif University of Technology, Petroleum and Chemical Engineering Department, Tehran, Iran.
Amirhossein Habibi - Sharif University of Technology, Petroleum and Chemical Engineering Department, Tehran, Iran.

Study of increasing lipid production from a microalgae Chlorella vulgaris was conducted in a four-column photo-bioreactor, by investigating the two important factors of flow and exertion of a dark phase. The second stage of a conventional photosynthesis process can be done either in presence or absence of light. Exertion of a second dark phase accompanied by aeration rates merely enough to keep the microalga alive and prevent sedimentation, seems to provide the cells with the necessary time to have a more efficient second step of photosynthesis i.e. CO2 stabilization. Furthermore, the decrease in growth rates indicates the higher concentrations of lipid stored in the cells. The flow in the columns enhances the mass transfer rates and results in better light absorption. The results obtained indicate that the procedure introduced here results in a slight increase in the product yield; however this value might show a magnificent impact in large scale operations.

photo-bioreactor, microalgae, photosynthesis