S-Systems Sensitivity Analysis of the Factors that May Influence Hydrogen Production by Sulfur-Deprived Chlamydomnas reinhardtii

We built a metabolic map of the hydrogen production process by the microalga Chlamydomonas reinhardtii, mathematically modeled this map in the S-systems formalism, then analyzed the effect of variations in the value of different model parameters on the overall response of the system. The mathematical model exhibited behavior similar to that described in literature for photosynthetic algal hydrogen production by sulfur-deprived algal cultures. This behavior consists of an initial phase during which oxygen is transiently generated and then consumed, followed by an anaerobic phase that is characterized by generation of hydrogen. Our analysis of the effect of independent variables on the hydrogen production process mostly agrees with previous work [Horner J, Wolinsky M. A power-law sensitivity analysis of the hydrogen-producing metabolic pathway in Chlamydomonas reinhardtii. Int J Hydrogen Energy 2002;27: 1251-1255]. Moreover, a more detailed study of the effects of parameter modification (rate constants and kinetic order) indicated that genetic engineering of the hydrogenase expression, activity and stability may lead to increased performance of the process.