Spirulina platensis is a unique photosynthetic cyanobacterium that is used as a commercial feed for animals and a dietary supplement for humans. S. platensis has significant auto-flotation activity due to its gas vesicles. The natural flotation activity of these cells provides an effective method for harvesting of Spirulina biomass. The present research found that hydrodynamic pressure, light level and bicarbonate concentration affected the natural flotation of S. platensis. In particular, auto-flotation increased as light level decreased (5.5-times greater at no supplemental light than at 300 μ㏖ photons/㎡/s), as bicarbonate level increased (5-times higher at 0.6 than 0.2 M) and as hydrodynamic pressure decreased (indicated by depth of the culture). These results should be considered when designing photobioreactors for direct harvesting by auto-flotation.

Abstract
Introduction
Materials and Methods
    1. Cultivation of Spirulina platensi
    2. Measurement of auto-flotation
    3. Measurement of dry cell weight
Results and Discussion
    1. Effect of PPFD on auto-flotation
    2. Effect of bicarbonate concentration on auto-flotation
    3. Effect of photobioreactor geometry on auto-flotation
References

• Chang-Su Lee(Division of Applied Life Sciences (BK21 plus), Gyeongsang National University)
• Do-Wook Woo(Department of Food Science & Technology and Institute of Agriculture & Life Science, Gyeongsang National University)
• Jong-Hee Kwon(Division of Applied Life Sciences (BK21 plus), Gyeongsang National University/Department of Food Science & Technology and Institute of Agriculture & Life Science, Gyeongsang National University) Corresponding author