High-Density Cultivation Of Spirulina Piatensis In Photobioreactor

Spirulina is a prokaryotes, filamentous blue-green algae in series with a lot of unicellular. They contain rich nutrients extremely, such as unsaturated fatty acids, algal polysaccharides, protein, vitamins and so on. Especially protein content is up to 60%-70%, They have many functions such as anti-cancer, anti-radiation, anti-AIDS, anti-mutagenic, anti-aging, to reduce mercury toxicity.Although has many advantages compared to conventional food, Spirulina production process also has some shortcomings, and the most important point is that the cost of production is higher than that of conventional food, which greatly restricts the industrial production of Spirulina. Therefore, it is particularly significant to reduce production costs of Spirulina. In this paper, a flat plate photobioreactor was designed for high-density cultures of Spirulina platensis, which focuses on the link of high-density, that is to achieve shorter production cycle and to increase greatly the biomass of Spirulina through a variety of means, which is consistent with the starting point of lower production costs.Whether batch cultures in the flasks or high-density cultures in the photobioreactor, the strain of Spirulina was very important. So this paper started with filtrating the best strain. The third strain was determined as the dominant strain through measuring dry weight and checking pollution. A detailed study of the optimization of culture conditions of Spirulina in the flasks was formulated to achieve high-density cultures in the photobioreactor efficiently, which showed that, for the growth of Spirulina, the most suitable temperature was 31-33℃, the most suitable light intensity was 4-5klx, the most suitable pH was 9.0-9.5.In order to promote the growth of Spirulina more efficiently, the effect of glucose on the growth of Spirulina was researched. The biomass of Spirulina significantly improved by adding additional 3g/L carbon source of glucose. In this glucose concentration, the content of chlorophyll a, phycobiliproteins and total lipid in the algal cells were 1.94 times,1.34 times,1.36 times than that of the control groups respectively. Although a certain amount of glucose could promote the growth of Spirulina, it also brought a high concentration of dissolved oxygen, which could lead the occurrence of oxidative duress. In order to avoid the high concentration of oxygen, the effect of six antioxidants:Na2S2O3, Na2SO3, TP, Vc, BHT and TBHQ was studied, the results showed that 2.0g/L Na2SO3 was the best, followed by 3.0g/L Na2S2O3.Finally, to achieve high-density cultures in the 7L flat photobioreactor the multiple experiments were designed. The results showed that the growth of Spirulina platensis could be effected very evidently by the factors of airflow, single-double-sided light source and additional carbon source. The maximum dry weight of 9.14g/L and the average growth rate of 0.695g/(L-day) were obtained, under the suitable cultural conditions that the airflow was from 100L/h to 800L/h with the increasing of the density of Spirulina platensis, adding additional substances were 3.0g/L glucose and 2.0g/L Na2SO3, the use of light source was from single-sided light source at the preliminary culture to double-sided light source at the logarithmic growth phase.