EFFECT OF SIMPLE SHEAR-FLOW ON PHOTOSYNTHESIS RATE AND MORPHOLOGY OF MICROALGAE

The convective motion of micro algal suspension gives an advantageous effect on the photosynthetic rate in the bioreactor, however, the natu re of convective effect on the photosynthesis has not been fully under stood. The propose of this study concerns the nature of photosynthetic rate in a well-defined hydrodynamic shear flow of Spirulina platensis suspension, generated in a double rotating coaxial cylinders. The dou ble rotating coaxial cylinders was installed in the incubator chamber with the controlled illumination intensity and temperature. Two kind o f experiments, short and long term experiments, were performed to eval uate the direct effect of shear flow on the photosynthetic rate. The s hort term experiment indicates that the simple shear flow enables to a ugment the photosynthesis of Spirulina suspension and simultaneously c auses the cell destruction due to the excessive shear stress. The long term experiment for 100 hours reveals that the growth rate and the mo rphology of Spirulina is sensitive to the external fluid mechanical st imulus. The long term application of mechanical stress on the algae ma y result in the adaptation of the photosynthetic function and morpholo gy.