Hybrid cultivation is a method that combines different growth stages in two types of photobioreactors, closed and open (Brennan and Owende, 2010). The hybrid culture system is designed to utilize the good qualities of both types of reactors. In the case of open and closed reactors, the first stage of the cultivation occurs in the closed photobioreactor, where the con­ditions are controlled to minimize contamination of other microorganisms and to promote continuous cell division.

In the second stage of production the cells are exposed to a nutritional stress, increasing the synthesis of a specific metabolite, such as lipids, proteins or polymers. The second stage is ideal for open ponds (Brennan and Owende, 2010). The a-shaped reactor is another type of hybrid system, developed by Lee et al. (1995). In this reactor, the culture is lifted 5 meters by air to a receiver tank, and culture flows down an inclined PVC tube (at an angle of 25° to the horizontal) to reach another set of air-riser tubes, and the process is repeated for the next set of tubes.