cis-vaccenic-acid and stearic-acid

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.

Topics: Alkanes; Alkenes; Biofuels; Biomass; Biosynthetic Pathways; Chlamydomonas reinhardtii; Chlorella; Chloroplasts; Diatoms; Fatty Acids; Hydrocarbons; Light; Microalgae; Oleic Acids; Stearic Acids

Brisket, chuck, plate, flank, and round subcutaneous fat trim were used to produce ground beef patties then evaluated for color, lipid oxidation, fatty acid composition, volatile chemical compounds and consumer sensory evaluation. Color, TBARS, consumer sensory evaluation, and cook/freezer loss did not differ (P>0.05) among carcass fat locations. Percentage stearic acid was lower (P=0.044) in the ground beef using brisket fat than using the chuck and flank fat. Patties made with brisket fat were higher in cis-vaccenic acid (P=0.016) and the saturated to monounsaturated fatty acid ratio (P=0.018) than all other sources of subcutaneous fat. Butanedione was highest (P=0.013) in patties using flank and plate fat. Ground beef with brisket fat was higher (P=0.003) than all other sources for beefy aroma. Altering the profile of non-polar, triglyceride fatty acids has no effect on sensory flavor or major volatile chemical compounds.

Topics: Animals; Body Fat Distribution; Cattle; Color; Consumer Behavior; Fatty Acids; Fatty Acids, Monounsaturated; Food Storage; Humans; Lipid Peroxidation; Odorants; Oleic Acids; Red Meat; Stearic Acids; Subcutaneous Fat; Taste; Thiobarbituric Acid Reactive Substances; Volatile Organic Compounds

Rhizobium etli is a microsymbiont of plants of the genus Phaseolus. Using mass spectrometry we have identified the lipo-chitin oligosaccharides (LCOs) that are produced by R. etli strain CE3. They are N-acetylglucosamine pentasaccharides of which the non-reducing residue is N-methylated and N-acylated with cis-vaccenic acid (C18:1) or stearic acid (C18:0) and carries a carbamoyl group at C4. The reducing residue is substituted at the C6 position with O-acetylfucose. Analysis of their biological activity on the host plant Phaseolus vulgaris shows that these LCOs can elicit the formation of nodule primordia which develop to the stage where vascular bundles are formed. The formation of complete nodule structures, including an organized vascular tissue, is never observed. Considering the very close resemblance of the R. etli LCO structures to those of R. loti (I. M. López-Lara, J. D. J. van den Berg, J. E. Thomas Oates, J. Glushka, B. J. J. Lugtenberg, H. P. Spaink, Mol Microbiol 15: 627-638, 1995) we tested the ability of R. etli strains to nodulate various Lotus species and of R. loti to nodulate P. vulgaris. The results show that R. etli is indeed able to nodulate Lotus plants. However, several Lotus species are only nodulated when an additional flavonoid independent transcription activator (FITA) nodD gene is provided. Phaseolus plants can also be nodulated by R. loti bacteria, but only when the bacteria contain a FITA nodD gene. Apparently, the type of nod gene inducers secreted by the plants is the major basis for the separation of Phaseolus and Lotus into different cross inoculation groups.

Topics: Acetylglucosamine; Acylation; Carbohydrate Sequence; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Fabaceae; Genes, Bacterial; Lipopolysaccharides; Molecular Sequence Data; Oleic Acids; Plants, Medicinal; Rhizobium; Signal Transduction; Spectrometry, Mass, Fast Atom Bombardment; Stearic Acids; Symbiosis

Topics: Chromatography; Fatty Acids; Lactones; Leuconostoc; Levulinic Acids; Oleic Acids; Palmitic Acid; Research; Stearic Acids

Topics: Adenosine Triphosphate; Animals; Chromatography; Fatty Acids; Liver; Mitochondria; NAD; NADP; Oleic Acid; Oleic Acids; Oxidation-Reduction; Palmitic Acid; Rats; Research; Stearic Acids