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Microalgae Compositional Analysis Laboratory Procedures

NREL develops laboratory analytical procedures (LAPs) for microalgae. These procedures help scientists and analysts understand more about the chemical composition of algae as a feedstock to convert to biofuels.

Human hand holding clear plastic packages of freeze-dried algae.

Example of freeze-dried and vacuum sealed packages of algae biomass. Photo by NREL.

Sample Reference Biomass Materials Available

A sample of a reference biomass material is available upon request for collaborating groups aiming to align data between different procedures or fine-tuning the implementation of the microalgae compositional analysis methods.

Two species of algae—Nannochloropsis and Scenedesmus—were harvested at the Arizona Center for Algae Technology and Innovation at Arizona State University resulting in biomass that was freeze-dried, certified by our team of analytical chemists, and vacuum-packaged for distribution.

Request a sample (as long as supplies last).

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Capabilities

NREL's algal biofuels research team can work with you to analyze the chemical composition of algae as a biomass feedstock.

Procedures

NREL wrote these analytical procedures to help the research community analyze algae.

Summative Mass Analysis of Algal Biomass – Integration of Analytical Procedures

This procedure guides the integration of LAPs to measure algal biomass constituents in an unambiguous manner and ultimately achieve mass balance closure for algal biomass samples. Many of these methods build on years of research in algal biomass analysis.

By combining the appropriate LAPs, the goal is to break the biomass sample into constituents that sum to as close to 100% by weight as possible. Some of these constituents are individual components, such as carbohydrates and lipids as total fatty acids, and some can be groups of compounds, such as extractable lipids.

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Determination of Total Carbohydrates in Algal Biomass

This procedure uses two-step sulfuric acid hydrolysis to hydrolyze the polymeric forms of carbohydrates in algal biomass into monomeric subunits. The monomers are then quantified by either high-performance liquid chromatography (HPLC) or a suitable spectrophotometric method.

An optimized hydrolysis procedure is expected to yield complete hydrolysis of all polymeric structural and storage carbohydrates into monomeric sugars. A range of sequential and optimized inorganic acid hydrolysis conditions with respective hydrolysis liquor collection and analysis should be carried out for algal biomass.

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Determination of Total Lipids as Fatty Acid Methyl Esters

This procedure is based on a whole biomass transesterification of lipids to fatty acid methyl esters (FAME) to represent an accurate reflection of the potential of microalgal biofuels. Lipids are present in many forms and play various roles within an algal cell, from cell membrane phospholipids to energy stored as triacylglycerols. The ability to identify and accurately quantify the fatty acid content of these lipids, as well as free fatty acids, is essential to evaluating fuel potential and establishing a comprehensive compositional analysis of algae.

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Determination of Total Solids and Ash in Algal Biomass

This procedure describes the methods used to determine the amount of moisture or total solids present in a freeze-dried algal biomass sample, as well as the ash content. A traditional convection oven drying procedure is covered for total solids content, and a dry oxidation method at 575°C is covered for ash content.

Algal biomass samples may contain a high and varying percentage of moisture, which can change rapidly when exposed to ambient humidity levels. These samples also may contain varying percentages of ash depending on species and the presence of growth media.

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Determination of Total Sterols in Microalgae by Acid Hydrolysis and Extraction

This procedure covers the determination of total sterols in freeze-dried microalgal biomass. Results are reported as the percent sterol content based on the oven dry weight of the sample. The procedure is based on  NREL’s fatty acid methyl esters LAP for total lipid quantification, making it easy to perform two analyses at once if desired, and saving significant time when compared to other sterol methods.

Because this method is based on an acid-catalyzed transesterification and hydrolysis, free sterols are produced from their complex composition, and analyzed by gas chromatography. This procedure does not produce phytol as another terpenoid-derived product, which is typically formed when a base-catalyzed conversion reaction is used.

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Contact

For more information about these laboratory analytical procedures, contact

Lieve Laurens

Lieve Laurens | 303-384-6196