Multi-component kinetics for the growth of the cyanobacterium synechocystis sp. PCC6803

The growth kinetics of phototrophic microorganisms can be controlled by the light irradiance, the concentration of an inorganic nutrient, or both. A multi-component kinetic model is proposed and tested in novel batch experiments that allow the kinetic parameters for each factor to be estimated independently. For the cyanobacterium Synechocystis sp. PCC6803, the estimated parameters are maximum specific growth rate (μ_max) = 2.8/d, half-maximum-rate light irradiance (K_L) = 11 W/m², half-inhibition-rate light irradiance (K_L,I) = 39 W/m², and half-maximum-rate concentration for inorganic carbon (K_S,Ci) = 0.5 mgC/L, half-maximum-rate concentration for inorganic nitrogen (K_S,Ni) = 1.4 mgN/L, and half-maximum-rate concentration for inorganic phosphorus (KS,Pi) = 0.06 mgP/L. Compared to other phototrophs having μmax estimates, PCC6803 is a fast-growing r-strategist relying on reaction rate. Its half-maximum-rate and half-inhibition rate values identify the ranges of light irradiance and nutrient concentrations that PCC6803 needs to achieve a high specific growth rate to be a sustainable bioenergy source. To gain the advantages of its high maximum specific growth rate, PCC6803 needs to have moderate light illumination (7-62 W/m² for μ_syn ≥ 1/d) and relatively high nutrient concentrations: N_i ≥ 2.3 mgN/L, P_i ≥ 0.1 mgP/L, and C_i ≥ 1.0 mgC/L.