Microalgae Synthesize Hydrocarbons from Long-Chain Fatty Acids via a Light-Dependent Pathway.
Microalgae are considered a promising platform for the production of lipid-based biofuels. While oil accumulation pathways are intensively researched, the possible existence of a microalgal pathways converting fatty acids into alka(e)nes has received little attention. Here, we provide evidence that such a pathway occurs in several microalgal species from the green and the red lineages. In Chlamydomonas reinhardtii (Chlorophyceae), a C17 alkene, n-heptadecene, was detected in the cell pellet and the headspace of liquid cultures. The Chlamydomonas alkene was identified as 7-heptadecene, an isomer likely formed by decarboxylation of cis-vaccenic acid. Accordingly, incubation of intact Chlamydomonas cells with per-deuterated D31-16:0 (palmitic) acid yielded D31-18:0 (stearic) acid, D29-18:1 (oleic and cis-vaccenic) acids, and D29-heptadecene. These findings showed that loss of the carboxyl group of a C18 monounsaturated fatty acid lead to heptadecene formation. Amount of 7-heptadecene varied with growth phase and temperature and was strictly dependent on light but was not affected by an inhibitor of photosystem II. Cell fractionation showed that approximately 80% of the alkene is localized in the chloroplast. Heptadecane, pentadecane, as well as 7- and 8-heptadecene were detected in Chlorella variabilis NC64A (Trebouxiophyceae) and several Nannochloropsis species (Eustigmatophyceae). In contrast, Ostreococcus tauri (Mamiellophyceae) and the diatom Phaeodactylum tricornutum produced C21 hexaene, without detectable C15-C19 hydrocarbons. Interestingly, no homologs of known hydrocarbon biosynthesis genes were found in the Nannochloropsis, Chlorella, or Chlamydomonas genomes. This work thus demonstrates that microalgae have the ability to convert C16 and C18 fatty acids into alka(e)nes by a new, light-dependent pathway.
CEA and CNRS and Aix-Marseille Université, Biosciences and Biotechnologies Institute (UMR 7265), Cadarache 13108, France (D.S., B.L., S.C., P.M., B.M., G.G., Y.L.-B., G.P., F.B.); andDepartment of Botany and Department of Chemistry, University of British Columbia, Vancouver V6T 1Z4, Canada (R.J.).
Damien
0000-0003-1149-0757
D
Sorigué
CEA and CNRS and Aix-Marseille Université, Biosciences and Biotechnologies Institute (UMR 7265), Cadarache 13108, France (D.S., B.L., S.C., P.M., B.M., G.G., Y.L.-B., G.P., F.B.); andDepartment of Botany and Department of Chemistry, University of British Columbia, Vancouver V6T 1Z4, Canada (R.J.).
Bertrand
B
Légeret
CEA and CNRS and Aix-Marseille Université, Biosciences and Biotechnologies Institute (UMR 7265), Cadarache 13108, France (D.S., B.L., S.C., P.M., B.M., G.G., Y.L.-B., G.P., F.B.); andDepartment of Botany and Department of Chemistry, University of British Columbia, Vancouver V6T 1Z4, Canada (R.J.).
Stéphan
0000-0002-3000-3355
S
Cuiné
CEA and CNRS and Aix-Marseille Université, Biosciences and Biotechnologies Institute (UMR 7265), Cadarache 13108, France (D.S., B.L., S.C., P.M., B.M., G.G., Y.L.-B., G.P., F.B.); andDepartment of Botany and Department of Chemistry, University of British Columbia, Vancouver V6T 1Z4, Canada (R.J.).
Pablo
0000-0003-2365-4309
P
Morales
CEA and CNRS and Aix-Marseille Université, Biosciences and Biotechnologies Institute (UMR 7265), Cadarache 13108, France (D.S., B.L., S.C., P.M., B.M., G.G., Y.L.-B., G.P., F.B.); andDepartment of Botany and Department of Chemistry, University of British Columbia, Vancouver V6T 1Z4, Canada (R.J.).
Boris
B
Mirabella
CEA and CNRS and Aix-Marseille Université, Biosciences and Biotechnologies Institute (UMR 7265), Cadarache 13108, France (D.S., B.L., S.C., P.M., B.M., G.G., Y.L.-B., G.P., F.B.); andDepartment of Botany and Department of Chemistry, University of British Columbia, Vancouver V6T 1Z4, Canada (R.J.).
Geneviève
G
Guédeney
CEA and CNRS and Aix-Marseille Université, Biosciences and Biotechnologies Institute (UMR 7265), Cadarache 13108, France (D.S., B.L., S.C., P.M., B.M., G.G., Y.L.-B., G.P., F.B.); andDepartment of Botany and Department of Chemistry, University of British Columbia, Vancouver V6T 1Z4, Canada (R.J.).
Yonghua
0000-0003-1064-1816
Y
Li-Beisson
CEA and CNRS and Aix-Marseille Université, Biosciences and Biotechnologies Institute (UMR 7265), Cadarache 13108, France (D.S., B.L., S.C., P.M., B.M., G.G., Y.L.-B., G.P., F.B.); andDepartment of Botany and Department of Chemistry, University of British Columbia, Vancouver V6T 1Z4, Canada (R.J.).
Reinhard
R
Jetter
CEA and CNRS and Aix-Marseille Université, Biosciences and Biotechnologies Institute (UMR 7265), Cadarache 13108, France (D.S., B.L., S.C., P.M., B.M., G.G., Y.L.-B., G.P., F.B.); andDepartment of Botany and Department of Chemistry, University of British Columbia, Vancouver V6T 1Z4, Canada (R.J.).
Gilles
G
Peltier
CEA and CNRS and Aix-Marseille Université, Biosciences and Biotechnologies Institute (UMR 7265), Cadarache 13108, France (D.S., B.L., S.C., P.M., B.M., G.G., Y.L.-B., G.P., F.B.); andDepartment of Botany and Department of Chemistry, University of British Columbia, Vancouver V6T 1Z4, Canada (R.J.) frederic.beisson@cea.fr.
Fred
0000-0001-9995-7387
F
Beisson
D000473:Alkanes / Q000737:chemistry / Q000378:metabolism; D000475:Alkenes / Q000737:chemistry / Q000378:metabolism; D056804:Biofuels; D018533:Biomass; D053898:Biosynthetic Pathways; D016825:Chlamydomonas reinhardtii / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D002708:Chlorella / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D017377:Diatoms / Q000378:metabolism*; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism*; D006838:Hydrocarbons / Q000737:chemistry / Q000378:metabolism*; D008027:Light; D058086:Microalgae; D009829:Oleic Acids / Q000737:chemistry / Q000378:metabolism; D013229:Stearic Acids / Q000737:chemistry / Q000378:metabolism
C473093:8-heptadecene; D000473:Alkanes; D000475:Alkenes; D056804:Biofuels; D005227:Fatty Acids; D006838:Hydrocarbons; D009829:Oleic Acids; D013229:Stearic Acids; C033245:pentadecane; C031183:stearic acid; C065593:cis-vaccenic acid; C016486:heptadecane