Process Optimization of High-density Cultivating Spirulina platensis in a Flat Photobioreactor

Spirulina is cultivated worldwide, used as a dietary supplement as well as a whole food, and is also available in tablet, flake and powder form. It is significant to improve the production capacity of Spirulina by optimization of production process. A biological reactor has a tank with an interior for growing the biological mass, and application of photobioreactor on high density culture of microalgae has become a hot spot in the domestic and foreign studies. The main economic spirulina is Spirulina platensis and S. maxima, however, S.platensis is the main Spirulina cultured in China. In this study, S. platensis was cultured by triangular flask andflat plate photobioreactor, and different culture conditions(concentration of glucose and antioxidants, and modes of ventilation and illumination) were designed to study the optimization of manufacture process.Results showed that adding glucose, Na2S2O3 and Na2SO3to triangular flasks separately could significantly improve the algae biomass, and its optimal concentration was 3, 3 and 2 g/L, respectively. Under algae culture in flat plate photobioreactor, the biomass of algae was increased significantly with the increase of aeration intensity from 100 to 800 L/h, however, algae biomass improvement was more obvious under the treatment of gradually increasing aeration intensity from 100 L/h to 800 L/h. Algae biomass cultured by single-side light(4500 lx) was obviously more than that cultured by double-side light(9 000 lx), and significantly less than that cultured by first single- side light and then double- side light at algae entering into logarithmic phase. The combination effect of Na2SO3 and glucose on algae biomass was better than that of Na2S2O3 and glucose.Further optimization of the above- mentioned conditions suggested that the algae biomass achieved the peak values under 4 g/L glucose and 3 g/L Na2SO3. Generally, adding glucose, Na2SO3, gradually increasing aeration intensity and illumination mode of the double side light source after the first one side light source increased algae production of S. platensis significantly. Under the condition of comprehensive optimization,the algae average growth rate and biomass production could be as high as 0.85 g DW/(L· d) and 10.02 g DW/L,respectively. Moreover, this photobioreactor had several advantages. That is small power consumption, small occupation area, relatively cheap cost, easy cleaning, simple structure, easy scale cultivation in room, etc. This culture technology can provide the theory basis and the technical method for scale cultivation of Spirulina.