title: Production of squalene in Synechocystis sp. PCC 6803.
abstract: In recent years, there has been an increased interest in the research and development of sustainable alternatives to fossil fuels. Using photosynthetic microorganisms to produce such alternatives is advantageous, since they can achieve direct conversion of carbon dioxide from the atmosphere into the desired product, using sunlight as the energy source. Squalene is a naturally occurring 30-carbon isoprenoid, which has commercial use in cosmetics and in vaccines. If it could be produced sustainably on a large scale, it could also be used instead of petroleum as a raw material for fuels and as feedstock for the chemical industry. The unicellular cyanobacterium Synechocystis PCC 6803 possesses a gene, slr2089, predicted to encode squalene hopene cyclase (Shc), an enzyme converting squalene into hopene, the substrate for forming hopanoids. Through inactivation of slr2089 (shc), we explored the possibility to produce squalene using cyanobacteria. The inactivation led to accumulation of squalene, to a level over 70 times higher than in wild type cells, reaching 0.67 mg OD750(-1) L(-1). We did not observe any significant growth deficiency in the Δshc strain compared to the wild type Synechocystis, even at high light conditions, suggesting that the observed squalene accumulation was not detrimental to growth, and that formation of hopene by Shc is not crucial for growth under normal conditions, nor for high-light stress tolerance. Effects of different light intensities and growth stages on squalene accumulation in the Δshc strain were investigated. We also identified a gene, sll0513, as a putative squalene synthase in Synechocystis, and verified its function by inactivation. In this work, we show that it is possible to use the cyanobacterium Synechocystis to generate squalene, a hydrocarbon of commercial interest and a potential biofuel. We also report the first identification of a squalene hopene cyclase, and the second identification of squalene synthase, in cyanobacteria.
authors.affiliation: Microbial Chemistry, Department of Chemistry, Ångström and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
authors.forename: Elias
authors.initials: E
authors.lastname: Englund
authors.affiliation: Microbial Chemistry, Department of Chemistry, Ångström and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
authors.forename: Bagmi
authors.initials: B
authors.lastname: Pattanaik
authors.affiliation: Analytical Chemistry, Department of Chemistry, BMC and Science for Life Laboratory, Uppsala, Sweden.
authors.forename: Sarojini Jayantha K
authors.initials: SJ
authors.lastname: Ubhayasekera
authors.affiliation: Microbial Chemistry, Department of Chemistry, Ångström and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
authors.forename: Karin
authors.initials: K
authors.lastname: Stensjö
authors.affiliation: Analytical Chemistry, Department of Chemistry, BMC and Science for Life Laboratory, Uppsala, Sweden.
authors.forename: Jonas
authors.initials: J
authors.lastname: Bergquist
authors.affiliation: Microbial Chemistry, Department of Chemistry, Ångström and Science for Life Laboratory, Uppsala University, Uppsala, Sweden.
authors.forename: Pia
authors.initials: P
authors.lastname: Lindberg
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D056804:Biofuels; D002245:Carbon Dioxide / Q000737:chemistry; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D008401:Gas Chromatography-Mass Spectrometry; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D005838:Genotype; D019751:Intramolecular Transferases / Q000737:chemistry / Q000235:genetics; D008027:Light; D012329:RNA, Bacterial / Q000235:genetics; D013185:Squalene / Q000737:chemistry*; D046939:Synechocystis / Q000737:chemistry* / Q000235:genetics; D013729:Terpenes / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D056804:Biofuels; D004269:DNA, Bacterial; D012329:RNA, Bacterial; D013729:Terpenes; D002245:Carbon Dioxide; D013185:Squalene; D019751:Intramolecular Transferases; C066630:squalene-hopene cyclase