Direct Conversion of CO to α-Farnesene Using Metabolically Engineered Synechococcus elongatus PCC 7942.

Direct conversion of carbon dioxide (CO) to value-added chemicals by engineering of cyanobacteria has received attention as a sustainable strategy in food and chemical industries. Herein， Synechococcus elongatus PCC 7942， a model cyanobacterium， was engineered to produce α-farnesene from CO. As a result of the lack of farnesene synthase (FS) activity in the wild-type cyanobacterium， we metabolically engineered S. elongatus PCC 7942 to express heterologous FS from either Norway spruce or apple fruit， resulting in detectable peaks of α-farnesene. To enhance α-farnesene production， an optimized methylerythritol phosphate (MEP) pathway was introduced in the farnesene-producing strain to supply farnesyl diphosphate. Subsequent cyanobacterial culture with a dodecane overlay resulted in photosynthetic production of α-farnesene (4.6 ± 0.4 mg/L in 7 days) from CO. To the best of our knowledge， this is the first report of the photosynthetic production of α-farnesene from CO in the unicellular cyanobacterium S. elongatus PCC 7942.