Extraction Methods Used to Separate Lipids from Microbes.

Lipids accumulated inside microbial cells (such as fungi, bacteria, yeast, microalgae, and macroalgae) have to be extracted for production of biodiesel and/or oleochemicals via thermochemical or thermocatalytic processes. Extraction methods for separation as well as quantification of lipids from microbes require organic solvents (such as hexane, methanol, and tetrahydrofuran) and involve multiple unit operations/steps such as thermal treatment (supercritical CO2 extraction), chemical treatment (acid or base, enzymes), mechanical operations (such as sonication and ball beating), liquid-solid separation, liquid-liquid extraction, and gravimetric or chromatographic analysis.

Quantification of Lipid Content in Oleaginous Biomass Using Thermogravimetry.

Laboratory analytical techniques employed for triglyceride quantification in oleaginous biomass (e.g., microalgae and oilseeds) involve multiple steps and typically require use of volatile organic solvents. Here we describe a single-step approach for measurement of triglycerides using thermogravimetry (TG). We have observed that triglycerides undergo complete volatilization over a narrow temperature interval of 370-450 °C, with negligible solid residue under inert atmosphere, whereas other constituents of oleaginous biomass (such as proteins and carbohydrates) primarily degrade below 350 °C. As a result, triglyceride content of biomass can be estimated using TG by determining the mass loss of the sample in the temperature interval of 370-450 °C.

Qualitative Characterization of the Aqueous Fraction from Hydrothermal Liquefaction of Algae Using 2D Gas Chromatography with Time-of-flight Mass Spectrometry.

Two-dimensional gas chromatography coupled with time-of-flight mass spectrometry is a powerful tool for identifying and quantifying chemical components in complex mixtures. It is often used to analyze gasoline, jet fuel, diesel, bio-diesel and the organic fraction of bio-crude/bio-oil. In most of those analyses, the first dimension of separation is non-polar, followed by a polar separation. The aqueous fractions of bio-crude and other aqueous samples from biofuels production have been examined with similar column combinations. However, sample preparation techniques such as derivatization, solvent extraction, and solid-phase extraction were necessary prior to analysis. In this study, aqueous fractions obtained from the hydrothermal liquefaction of algae were characterized by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry without prior sample preparation techniques using a polar separation in the first dimension followed by a non-polar separation in the second. Two-dimensional plots from this analysis were compared with those obtained from the more traditional column configuration. Results from qualitative characterization of the aqueous fractions of algal bio-crude are discussed in detail. The advantages of using a polar separation followed by a non-polar separation for characterization of organics in aqueous samples by two-dimensional gas chromatography coupled with time-of-flight mass spectrometry are highlighted.

Comparative study of pyrolysis of algal biomass from natural lake blooms with lignocellulosic biomass.

Pyrolysis experiments were performed with algal and lignocellulosic feedstocks under similar reactor conditions for comparison of product (bio-oil, gas and bio-char) yields and composition. In spite of major differences in component bio-polymers, feedstock properties relevant to thermo-chemical conversions, such as overall C, H and O-content, C/O and H/C molar ratio as well as calorific values, were found to be similar for algae and lignocellulosic material. Bio-oil yields from algae and some lignocellulosic materials were similar; however, algal bio-oils were compositionally different and contained several N-compounds (most likely from protein degradation). Algal bio-char also had a significantly higher N-content. Overall, our results suggest that it is feasible to convert algal cultures deficient in lipids, such as nuisance algae obtained from natural blooms, into liquid fuels by thermochemical methods. As such, pyrolysis technologies being developed for lignocellulosic biomass may be directly applicable to algal feedstocks as well.