Kinetic Modeling of Light Limitation and Sulfur Deprivation Effects in the Induction of Hydrogen Production With Chlamydomonas reinhardtii: Part I. Model Development and Parameter Identification

Chlamydomonas reinhardtii is a green microalga capable of turning its metabolism towards H-2 production under specific conditions. However this H-2 Production, narrowly linked to the photosynthetic process, results from complex metabolic reactions highly dependent on the environmental conditions of the cells. A kinetic model has been developed to relate culture evolution from standard photosynthetic growth to H-2 producing cells. It represents transition in sulfur-deprived conditions, known to lead to H-2 production in Chlamydomonas reinhardtii, and the two main processes then induced which are an over-accumulation of intracellular starch and a progressive reduction of PSII activity for anoxia achievement. Because these phenomena are directly linked to the photosynthetic growth, two kinetic models were associated, the first (one) introducing light dependency (Haldane type model associated to a radiative light transfer model), the second (one) making growth a function of available sulfur amount under extra-cellular and intracellular forms (Droop formulation). The model parameters identification was realized front experimental data obtained with especially designed experiments and a sensitivity analysis of the model to its parameters was also conducted. Model behavior was finally studied showing interdependency between light transfer conditions, photosynthetic growth, sulfate uptake, photosynthetic activity and O-2 release, during transition from oxygenic growth to anoxic H, production conditions. Biotechnol. Bioeng. 2009;102: 232-245. (C) 2008 Wiley Periodicals, Inc.