To have better control over photobioreactors at various operating conditions, it is necessary to characterize microorganisms’ motion, optimize light distribution, and investigate efficient mixing methods in photobioreactors.
The second chapter of this thesis aims to develop a theoretical model for the calculation of microorganisms’ optical characteristics. Modeling light transfer in photobioreactors needs accurate input data to solve Maxwell’s equations. Here, input data include absorption properties of the microorganism’s pigment, pigment-content measurement, and the details of the shape and size of the microorganism cells. These input data predicted the optical characteristics of microorganism cells with homogeneous, coated, and heterogeneous geometries.
The third chapter reports on experiments that were carried out to investigate the effect of two mixing methods, turbulent stirring and orbitally shaking, on the growth metrics of Synechocystis sp. CPCC 534, and compare them with stationary cultures. The study revealed that stirring Synechocystis cultures can enhance the growth rate, doubling per day, yield, and Chla production in contrast to cultures without any mixing.
In the fourth chapter, the motility of wild-type Synechocystis sp. CPCC 534 was investigated to establish a correlation between the evolution of cell motility and cell growth phases during the complete growth cycle of 78 days. Average cell velocity, mean squared displacement (MSD), diffusion coefficient, and displacement probability density function (PDF) were calculated to assess the dynamics of Synechocystis sp. CPCC 534 during the growth period. The obtained results indicate that the age of microorganisms has a notable influence on different aspects of cell motility. Consequently, this can affect the transport characteristics of active suspension.
In the final chapter of this thesis, we aimed to examine the transport characteristics of active fluids and passive fluids in a bifurcated microchannel with a rectangular cross-section. A PDMS microchannel was designed and fabricated to investigate the behavior of two fluids in the bifurcated microchannel. Finally, our investigation revealed that passive fluids exhibit higher velocity than active fluids. This difference arises due to the minimal movement of active fluids caused by their run-and-tumble motion
