Modeling of photobioreactors: Application to bubble column simulation

Abstract

Photobioreactors using algae, plant cells, or photosynthetic bacteria have received considerable attention from biochemical engineers. Industry is presently engaged in developing new products and testing a new generation of algal-derived natural products such as natural dyes, polyunsaturated fatty acids and polysaccharides. The present paper is a review of some of the recent findings of the authors in the field. A mathematical representation of the growth of a photosynthetic system in an alternating light-dark regime is presented. This model integrates fluid dynamics and maintenance into the three-state "Photosynthetic Factories" model by Eilers and Peeters. The model was solved analytically and the constants were fitted to experimental data obtained in a thin film tubular reactor. The theoretical prediction that the introduction of light-dark cycles may enhance the growth was confirmed by the experimental results. The model allows predicting the collapse of cultures in photobioreactors either under light-deficit or light-excess conditions, as well as the influence of mixing on these critical phenomena. This paper presents an approach to modeling the kinetics of photosynthetic systems for photobioreactor design. Under conditions of simultaneous occurrence of photoinhibition in one region of the reactor, and photo-limitation in another, it takes into account the movement of the cells from one region to the other. The model was applied to the mathematical modeling of a 13-liter bubble column photobioreactor. Experimental data were satisfactorily fit, using the kinetic data obtained independently in the thin-film experiments. The model was extended to simulate a "farm" of photobioreactors and the results presented defining Ground Productivity, which expresses the rate of biomass production of a farm of relatively small photobioreactors per area of ground required for the installation.