Light scattering influence in cyanobacteria suspensions inside a photobioreactor

Abstract

The application of biotechnology is increasing in areas such as agriculture, biochemistry or biomedicine. Growing bacteria or algae could be beneficial for supplying fuel, drugs, food or oxygen, among other products. An adequate knowledge of biological processes is becoming essential to estimate and control products production. Cyanobacteria are particularly appropriate for producing oxygen and biomass, by consuming mainly carbon dioxide and light irradiation. These capacities could be employed to provide human subsistence in adverse environments, as basic breathing and food needs would be satisfied. Cyanobacteria growing is carried out in bioreactors. As light irradiation is quite relevant for their behavior, photobioreactors are needed. Photobioreactors are designed to supply and control the amounts of elements they need, in order to maximize growth. The adequate design of photobioreactors greatly influences production throughput. This design includes, on the optical side, optical illumination and optical measurement of cyanobacteria growth. The influence of optical scattering is fundamental for maximizing cyanobacteria growing, as long as for adequately measure this growth. In this work, optical scattering in cyanobacteria suspensions is analyzed. Optical properties of cyanobacteria and its relationship with concentration is taken into account. Several types of cyanobacteria are considered. The influence of different beam spatial profiles and irradiances is studied by a Monte Carlo approach. The results would allow the consideration of the influence of optical scattering in the detected optical signal employed for growth monitoring, as a function of cyanobacteria type and optical beam parameters.