biostudies-literatureLee HBiological and Environmental Research359-367https://www.ebi.ac.uk/biostudies/studies/S-EPMC12930504biostudies-literatureUnknown15(2)Cyanobacterial production of a biofertilizer shows promise as an environmentally benign alternative to conventional nitrogen fertilizers, reducing environmental and energy burdens through light-driven nitrogen and carbon fixation. One route to realizing the potential for a nitrogen-rich, slow-releasing biofertilizer involves the genetic engineering of cyanobacteria to produce guanidine. Recent advances have demonstrated enzymatic guanidine production in cyanobacteria, but an understanding of cyanobacterial guanidine metabolism is still limited. This Perspective highlights strategies and opportunities for cyanobacterial guanidine production in a Design-Build-Test-Learn cycle. Exploring new guanidine-producing enzymes via phylogenetics could expand candidate enzymes, while understanding the ACS synthetic biologyCyanobacterial Biofertilizer Production by Guanidine-Producing Enzymes.PMC12930504DE-SC0024702Schaedig ESebesta JWu CLee HPakrasi HBYu JfalseCyanobacterial Biofertilizer Production by Guanidine-Producing Enzymes.Cyanobacterial production of a biofertilizer shows promise as an environmentally benign alternative to conventional nitrogen fertilizers, reducing environmental and energy burdens through light-driven nitrogen and carbon fixation. One route to realizing the potential for a nitrogen-rich, slow-releasing biofertilizer involves the genetic engineering of cyanobacteria to produce guanidine. Recent advances have demonstrated enzymatic guanidine production in cyanobacteria, but an understanding of cyanobacterial guanidine metabolism is still limited. This Perspective highlights strategies and opportunities for cyanobacterial guanidine production in a Design-Build-Test-Learn cycle. Exploring new guanidine-producing enzymes via phylogenetics could expand candidate enzymes, while understanding the 2026-01-01T00:00:00Z2026 Feb2026-07-09T12:20:28.894Z2026-07-09T11:17:30.265ZS-EPMC129305044166633610.1021/acssynbio.5c00801