Utilization of CO2 by converting it to useful organic compounds is an important strategy to move toward carbon neutrality and sustainable societies. Biological systems including plants and algae have driven conversion of CO2 to diverse organic compounds using their CO2 assimilation pathways and reducing powers. In this article, metabolic pathways and reactions assimilating CO2 and corresponding enzymes are reviewed. In addition, metabolic systems and the sources of energy and electrons for regenerating reducing powers are revisited. Finally, examples of exploiting native and heterologous metabolisms of bacteria for biological conversion of CO2 to food resources and value-added organic compounds are discussed.