FIGURE 1.

Milestone in developing artificial autotrophy in the last decade. Until 2011, six naturally occurring CO₂ fixation pathways have been identified, some of which were introduced into heterotrophic microorganisms. However, all of biomass was derived from additional multi-carbon compounds, such as glucose. The strong advances in synthetic biology enable the engineering of synthetic CO₂ fixation pathways for improving carbon assimilation efficiency. Since 2016, hemiautotrophy has been successfully constructed by integrating natural or synthetic CO₂ fixation pathways in heterotrophic hosts using organic compound as reducing power and energy source, in which biomass was completely derived from CO₂. In 2019 and 2020, the conversion of heterotrophy to fully autotrophy was realized though integration of natural CO₂ fixation pathways to support cell growth and inorganic compound’s oxidation to provide reducing power and energy.