Lipid Fatty Acid Methyl Ester Research Articles

Comparison of solvent mixtures for pressurized solvent extraction of soil fatty acid biomarkers

The extraction and transesterification of soil lipids into fatty acid methyl esters (FAMEs) is a useful technique for studying soil microbial communities. The objective of this study was to find the best solvent mixture to extract soil lipids with a pressurized solvent extractor system. Four solvent mixtures were selected for testing: chloroform:methanol:phosphate buffer (1:2:0.8, v/v/v), chloroform:methanol (1:2, v/v), hexane:2-propanol (3:2, v/v) and acetone. Soils were from agricultural fields and had a wide range of clay, organic matter and microbial biomass contents. Total lipid fatty acid methyl esters (TL-FAMEs) were the extractable soil lipids identified and quantified with gas chromatography and flame ionization detection. Concentrations of TL-FAMEs ranged from 57.3 to 542.2 n mole g −1 soil (dry weight basis). The highest concentrations of TL-FAMEs were extracted with chloroform:methanol:buffer or chloroform:methanol mixtures than with the hexane:2-propanol or acetone solvents. The concentrations of TL-FAMEs in chemical groups, including saturated, branched, mono- and poly-unsaturated and hydroxy fatty acids were assessed, and biological groups (soil bacteria, mycorrhizal fungi, saprophytic fungi and higher plants) was distinguished. The extraction efficiency for the chemical and biological groups followed the general trend of: chloroform:methanol:buffer ≥ chloroform:methanol > hexane:2-propanol = acetone. Discriminant analysis revealed differences in TL-FAME profiles based on the solvent mixture and the soil type. Although solvent mixtures containing chloroform and methanol were the most efficient for extracting lipids from the agricultural soils in this study, soil properties and the lipid groups to be studied should be considered when selecting a solvent mixture. According to our knowledge, this is the first report of soil lipid extraction with hexane:2-propanol or acetone in a pressurized solvent extraction system.

Lipids and carbohydrates in symbiotic and aposymbiotic Crithidia oncopelti and Blastocrithidia culicis

1. 1. Normal and aposymbiotic Crithidia oncopelti and Blastocrithidia culicis were compared as to neutral and polar lipid, total lipid, total lipid fatty acid, mono- and polysaccharide compositions using thin-layer (TLC) and gas-liquid (GLC) chromatography and cellulose acetate electrophoresis. 2. 2. Blastocrithidia possessed a major neutral lipid, lacking in Crithidia, with a TLC mobility similar to that of a monoglyceride. GLC of total lipid fatty acid methyl esters revealed that a major (20:4) components of Blastocrithidia was lacking in Crithidia. 3. 3. Blastocrithidia displayed one more toluidine blue-stainable glycosaminoglycan, separable by cellulose acetate electrophoresis, than did Crithidia. 4. 4. GLC of alditol acetate derivatives of monosaccharides revealed relatively more fucose than manose in whole-cell and protein fractions, but not in lipid, in normal compared to aposymbiotic Crithidia. 5. 5. Differences in carbohydrate composition may help explain the differential susceptibility of normal and aposymbiotic flagellates to agglutination by lectins which recognize fucosyl or mannosyl linkages.