Insight into the potential mechanism of bicarbonate assimilation promoted by mixotrophic in CO₂ absorption and...

CO₂ absorption-microalgae conversion (CAMC) system is a promising carbon capture and utilization technology. However, the use of HCO₃^- as a carbon source often led to a slower growth rate of microalgae, which also limited the application of CAMC system. In this study, the assimilation efficiency of HCO₃^- in CAMC system was improved through mixotrophic, and the potential mechanism was investigated. The HCO₃^- assimilation efficiency and biomass under mixotrophic were 34.79% and 31.76% higher than that of control. Mixotrophic increased chlorophyll and phycocyanin content, which were beneficial to capture more light energy. The content of ATP and NADPH reached 566.86 μmol/g_prot and 672.86 nmol/mg_prot, which increased by 31.83% and 27.67% compared to autotrophic. The activity of carbonic anhydrase and Rubisco increased by 18.52% and 22.08%, respectively. Transcriptome showed that genes related to photosynthetic and respiratory electron transport were up-regulated. The synergy of photophosphorylation and oxidative phosphorylation greatly improved energy metabolism efficiency, thus accelerating the assimilation of HCO₃^-. These results revealed a potential mechanism of promoting the HCO₃^- assimilation under mixotrophic, it also provided a guidance for using CAMC system to serve carbon neutrality.