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

An integrated photobioreactor for 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 biomass yield and carbon fixation capacity by 326.6% and 371.2%, respectively. Carbon flow predominantly shifts toward lipid synthesis during bioconversion. Transcriptomics revealed that adaptive CO2 concentrating mechanism (CCM) such as C4-dicarboxylic acid cycle and crassulacean acid metabolism (CAM) pathways might be partially activated by attached cultivation for carbon fixation. Differentially expressed genes (DEGs) related to C4 and CAM pathways, such as pckA, ppc, ppdK, MDH2, GOT2 and GPT were significantly up-regulated. This study demonstrated efficient bio-integrated carbon capture and utilization through attached cultivation, enhancing bicarbonate assimilation and direct CO2 capture from the atmosphere, while enabling cost-effective conversion in algae-based biorefineries.