Kinetic Model of Photoautotrophic Growth of Chlorella sp. Microalga, Isolated from the Setúbal Lagoon.

In this work, a kinetic expression relating light availability in the culture medium with the rate of microalgal growth is obtained. This expression, which is valid for low illumination conditions, was derived from the reactions that take part in the light-dependent stage of photosynthesis. The kinetic expression obtained is a function of the biomass concentration in the culture, as well as of the local volumetric rate of absorption of photons, and only includes two adjustable parameters. To determine the value of these parameters and to test the validity of the hypotheses made, autotrophic cultures of the Chlorella sp. strain were carried out in a modified BBM medium at three CO2 concentrations in the gas stream, namely 0.034%, 0.34% and 3.4%. Moreover, the local volumetric rate of photon absorption was predicted based on a physical model of the interaction of the radiant energy with the suspended biomass, together with a Monte Carlo simulation algorithm. The proposed intrinsic expression of the biomass growth rate, together with the Monte Carlo radiation field simulator, are key to scale up photobioreactors when operating under low irradiation conditions, independently of the configuration of the reactor and of its light source.