Guanidine (CH5N3) is a nitrogen-rich compound, containing 71.1% of nitrogen by mass. It has a variety of applications such as slow-release fertilizer, propellant, precursor to pharmaceuticals and antimicrobial materials. Conventional chemical synthesis of guanidine through the Frank-Caro process consumes fossil fuels, is energy-intensive and environmentally-damaging, which is neither economical nor sustainable. Herein, a de novo guanidine biosynthesis cycle (GBC) was designed and demonstrated utilizing CO2, ammonium and H2O as the sole carbon, nitrogen and hydrogen sources. The ATP and NAD(P)H used to drive the GBC were generated from renewable solar energy via photosynthesis in an engineered cyanobacterium Synechocystis sp. PCC 6803. Up to 586.5 mg L-1 (9.9 mM) guanidine was produced after seven days of photoautotrophic cultivation, with an average productivity of 83.8 mg L-1 day-1. More importantly, guanidine was directly biosynthesized from CO2, N2 and H2O in an engineered N2-fixing cyanobacterium Anabaena sp. PCC 7120 under N2-fixing conditions. For the first time, guanidine has been synthesized directly from all renewable resources such as CO2, H2O, N2 and sunlight, without involving toxic intermediates.

Photosynthetic production of nitrogen-rich compound guanidine

2019 Spring National Meeting

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