Coupling attached cultivation with CO2 absorption-microalgae conversion system for efficient bio-integrated carbon capture and utilization

An integrated photobioreactor for the simultaneous carbon capture and utilization was developed by coupling non-immersed attached cultivation with CO2 absorption-microalgae conversion (CAMC) system. Polyester porous cotton, mixed cellulose ester (MCE) membrane and Chlorella L166 were screened as the optimal candidates. Compared with traditional suspended cultivation, attached cultivation significantly increased the biomass and carbon fixation capacity of the CAMC system by 326.63% and 371.21%, respectively. Effective bioconversion into value-added products such as pigments and organic components, especially carbon flow tends to be directed towards lipid synthesis. Higher key enzyme activities, ATP and NADPH levels synergistically provide catalysis, substrates, energy and reducing power for carbon fixation. Although uncommon in microalgae, the C4-dicarboxylic acid cycle (C4) and crassulacean acid metabolism (CAM) pathways were partially activated under attached cultivation, which serve as adaptive CO2 concentrating mechanism (CCM) under low CO2, high light and water stress.