Direct photosynthetic recycling of carbon dioxide to isobutyraldehyde

Global climate change has stimulated efforts to reduce CO2 emissions. One approach to addressing this problem is to recycle CO2 directly into fuels or chemicals using photosynthesis. Here we genetically engineered Synechococcus elongatus PCC7942 to produce isobutyraldehyde and isobutanol directly from CO2 and increased productivity by overexpression of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco). Isobutyraldehyde is a precursor for the synthesis of other chemicals, and isobutanol can be used as a gasoline substitute. The high vapor pressure of isobutyraldehyde allows in situ product recovery and reduces product toxicity. The engineered strain remained active for 8 d and produced isobutyraldehyde at a higher rate than those reported for ethanol(1), hydrogen(2) or lipid(3) production by cyanobacteria or algae. These results underscore the promise of direct bioconversion of CO2 into fuels and chemicals, which bypasses the need for deconstruction of biomass.