Characterization of the acylglycerols and resulting biodiesel derived from vegetable oil and microalgae (Thalassiosira pseudonana and Phaeodactylum tricornutum)

Abstract

Algal biofuels are a growing interest worldwide due to their potential in terms of sustainable greenhouse gas displacement and energy production. This article describes a comparative survey of biodiesel production and conversion yields of biodiesel via alkaline transesterification of acylglycerols extracted from the microalgae Thalassiosira pseudonana and Phaeodactylum tricornutum, grown under silicate or nitrate limitation, and that of model vegetable oils: soybean, and rapeseed oil. Acylglycerols were extracted with n-hexane and the total yield per biomass was determined by gravimetric assay. Under our conditions, the total acylglycerol yield from the microalgae studied was 13-18% of total dry weight. The biodiesel samples were analyzed using gas chromatography-flame ionization detector to determine quantitative information of residual glycerol, mono-, di-, and tri-acylglycerol concentrations in the biodiesel. All of the algal-based biodiesel demonstrated less mono-, di-, and tri-acylglycerol concentrations than the vegetable-based biodiesel under identical transesterification conditions. The fatty acid compositions of all the feedstock oils and their resultant biodiesel were also analyzed and reported. Based on the fatty acid methyl ester compositions of our samples we qualitatively assessed the suitability of the algal-derived biodiesel in terms of cetane number (CN), cold-flow properties, and oxidative stability. Biotechnol. Bioeng. 2012;109: 1146-1154. Published 2011. This article is a U.S. Government work and is in the public domain in the USA. This work presents the feasibility of producing biodiesel, at the bench-scale, from extracted algal acylglycerols produced by Phaeodactylum tricornutum and Thalassiosira Pseudonana under targeted environmental conditions. Using GC-FID the authors quantified the residual glycerol, MAGs, DAGs, TAGs, and total free glycerol within the resultant biodiesel. The fatty acid profiles for the feedstock oils and their resultant biodiesel methyl esters are also presented along with a qualitative assessment of the suitability of the diatom-based biodiesel in terms of cetane number (CN), cold-flow properties, and oxidative stability. © 2011.