Fatty acid production in genetically modified cyanobacteria

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 108; no. 17; pp. 6899 - 6904
• Main Authors: Liu, Xinyao, Sheng, Jie, Curtiss III, Roy
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 26.04.2011; National Acad Sciences
• Subjects: Bacteria; Biodiesel fuels; Biofuels; Biological Sciences; Biomass; Cell culture; Cell density; Cell growth; Cell membranes; Cell walls; Cells; Cultured cells; Cyanobacteria; Escherichia coli Proteins - biosynthesis; Escherichia coli Proteins - genetics; Fatty acids; Fatty Acids - genetics; Fatty Acids - secretion; fuel production; Fuel technology; genes; genetic engineering; Genetics; Lysophospholipase - biosynthesis; Lysophospholipase - genetics; Membranes; Nonesterified fatty acids; Organisms, Genetically Modified - genetics; Organisms, Genetically Modified - metabolism; Overproduction; Periplasmic Proteins - biosynthesis; Periplasmic Proteins - genetics; Photosynthesis; Plants; Proteins; Secretion; stationary phase; sustainable technology; Synechocystis; Synechocystis - enzymology; Synechocystis - genetics; Technology; thioesterase; Thiolester Hydrolases - biosynthesis; Thiolester Hydrolases - genetics
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1103014108

To avoid costly biomass recovery in photosynthetic microbial biofuel production, we genetically modified cyanobacteria to produce and secrete fatty acids. Starting with introducing an acyl-acyl carrier protein thioesterase gene, we made six successive generations of genetic modifications of cyanobacterium Synechocystis sp. PCC6803 wild type (SD100). The fatty acid secretion yield was increased to 197 ± 14 mg/L of culture in one improved strain at a cell density of 1.0 x 10⁹ cells/mL by adding codon-optimized thioesterase genes and weakening polar cell wall layers. Although these strains exhibited damaged cell membranes at low cell densities, they grew more rapidly at high cell densities in late exponential and stationary phase and exhibited less cell damage than cells in wild-type cultures. Our results suggest that fatty acid secreting cyanobacteria are a promising technology for renewable biofuel production.