Direct Analysis and Profiling of Intact Triglycerides in Microalgal Oil by UHPLC-MS

Oleagenous (oil-bearing) microalgae have been reported to be a potential feedstock for biodiesel production. These microorganisms are usually cultivated in large ponds, then harvested and extracted for their oils (mainly triglycerides). The extracted oils are then made to undergo a "trans-esterification"reaction with methanol in order to obtain a mixture of methyl esters (collectively known as "biodiesel"). The screening of microalgae that can be potentially cultivated as biodiesel feedstocks usually involves a determination of how much oil the algae can produce, and what type of triglycerides are present in the oil.

The common method of triglyceride analysis is to break-down the triglycerides into their component fatty acids and then "derivatize" the fatty acids into their corresponding methyl esters for injection into a gas chromatograph. However, according to the researchers from the National Research Council of Canada, GC (gaschromatographic) detection of fatty acid methyl esters (FAME) in the oil samples "offers fragmentation data of fatty acid identification", and no information is provided regarding the intact lipids. Consequently, "GC analysis could be misleading if relying solely on the fatty acid profile for strain selection in biofuels applications." An alternative method for the direct measurement of intact lipids was attempted using Ultra High Pressure Liquid Chromatography-Mass Spectrometry (UHPLC-MS). They tested the method using six different types of algal strains for possible use in biofuel applications: Botryococcus braunii, Nannochloropsis gaditana, Neochloris oleoabundans, Phaeodactyl umtricornutum, Porphyridium aerugineum,and Scenedesmus obliquus.

The following are some highlights of the study: (1) the procedure allowed the identification of more than 100 unique triglycerides from the six algal strains, (2) the "most comprehensive [triglyceride] profile" with a high abundance of oleic acid were from Botryococcus braunii and Scenedesmusobliquus. The complete paper is published in the journal, Analytical and Bioanalytical Chemistry (URL above).