Optimization of CO2 Supply for the Intensive Cultivation of Chlorella sorokiniana IPPAS C-1 in the Laboratory and Pilot-Scale Flat-Panel Photobioreactors

Abstract

Microalgae are increasingly being used for capturing carbon dioxide and converting it into valuable metabolites and biologically active compounds on an industrial scale. The efficient production of microalgae biomass requires the optimization of resources, including CO₂. Here, we estimated the productivity of <i>Chlorella sorokiniana</i> IPPAS C-1 depending on CO₂ concentrations and the ventilation coefficient of the gas-air mixture (GAM) in flat-panel photobioreactors (FP-PBRs) at laboratory (5 L) and pilot (18 L) scales. For the laboratory scale, the PBRs operated at 900 µmol quanta m^-2 s^-1 and 35.5 ± 0.5 °C; the optimal CO₂ flow rate was estimated at 3 mL CO₂ per 1 L of suspension per minute, which corresponds to 1.5% CO₂ in the GAM and an aeration rate of 0.2 vvm. These parameters, being scaled up within the pilot PBRs, resulted in a high specific growth rate (µ ≈ 0.1 h^-1) and high specific productivity (P_sp ≈ 1 g dw L^-1 d^-1). The principles of increasing the efficiency of the intensive cultivation of <i>C. sorokiniana</i> IPPAS C-1 are discussed. These principles are relevant for the development of technological regimes for the industrial production of <i>Chlorella</i> in flat-panel PBRs of various sizes.