In Situ Transesterification Research Articles

Use of Ultrasound and Co-Solvents to Improve the In-Situ Transesterification of Microalgae Biomass

The conversion of microalgae lipids to biodiesel has been increasingly investigated, with the use of the in-situ transesterification method reported in the literature to lead to improved alkyl ester conversions for this feedstock compared with the use of the conventional two staged oil extraction and transesterification process. To further improve the feasibility of the use of the in-situ method, this paper investigates modifications to reduce the large process methanol requirements, and potentially improve the oil to methyl esters conversion and biodiesel yields. The results obtained showed that use of ultrasound agitation for the in-situ process, as well as combining this stirring regime with co-solvent use (n-pentane and diethyl ether) significantly improved the Chlorella oil to methyl esters conversion with reduced reacting methanol volumes.

Suitability of Soxhlet Extraction to Quantify Microalgal Fatty Acids as Determined by Comparison with In Situ Transesterification

To assess Soxhlet extraction as a method for quantifying fatty acids (FA) of microalgae, crude lipid, FA content from Soxhlet extracts and FA content from in situ transesterification (ISTE) were compared. In most cases, gravimetric lipid content was considerably greater (up to sevenfold) than the FA content of the crude lipid extract. FA content from Soxhlet lipid extraction and ISTE were similar in 12/18 samples, whereas in 6/18 samples, total FA content from Soxhlet extraction was less than the ISTE procedure. Re-extraction of residual biomass from Soxhlet extraction with ISTE liberated a quantity of FA equivalent to this discrepancy. Employing acid hydrolysis before Soxhlet extraction yielded FA content roughly equivalent to ISTE, indicating that acidic conditions of ISTE are responsible for this observed greater recovery of FA. While crude lipid derived from Soxhlet extraction was not a useful proxy for FA content for the species tested, it is effective in most strains at extracting total saponifiable lipid. Lipid class analysis showed the source of FA was primarily polar lipids in most samples (12/18 lipid extracts contained <5% TAG), even in cases where total FA content was high (>15%). This investigation confirms the usefulness of ISTE, reveals limitations of gravimetric methods for projecting biodiesel potential of microalgae, and reinforces the need for intelligent screening using both FA and lipid class analysis.

Fatty acid composition of Edam, Emmental and Gouda cheeses produced in Slovenia in autumn 1997

The aim of our work was to determine fatty acid composition of three different types of cheeses - Edam, Gouda and Emmental, produced in Slovenia in autumn 1997. The analysed Edam and Gouda cheese was produced by three and Emmental cheese by two different producers. All samples were purchased in the local supermarkets twice in the period of three months in autumn 1997. The methyl esters of the fatty acids were prepared by in situ transesterification (ISTE) and determined by gas chromatography. The average total SAT (saturated fatty acids) content was 56.80 wt % (relative percentage for each fatty acid of the total fatty acids) for Emmental cheese, 56.62 wt % for Edam cheese and 57.49 wt % for Gouda cheese. The average total MUFA (monounsaturated fatty acids) content was 34.26 wt % for Emmental cheese, 34.28 wt % for Edam cheese and 33.45 wt % for Gouda cheese. The average total PUFA (polyunsaturated fatty acids) content was 5.30 wt % for Emmental cheese, 5.74% for Edam cheese and 5.64% for Gouda cheese. No great difference was found between three types of cheese concerning the fatty acid profile (wt %).

In Situ Preparation of Fatty Acid Methyl Esters for Analysis of Fatty Acid Composition in Foods

ABSTRACTLipid extraction preceding fatty acid methyl esters (FAME) preparation for gas chromatography is time‐consuming and cumbersome. We omitted the lipid extraction and performed in situ transesterification (ISTE) by heating lipid‐containing foods at 90°for 10 min after adding 0.5N NaOH in methanol for methanolysis and continued heating another 10 min for further methylation after adding 14% BF3 in methanol. FAME prepared by ISTE showed fatty acid composition virtually identical to FAME prepared after lipid extraction from powder, liquid, phospholipid‐rich, and tissue products. Due to its simplicity, speed, and reduced organic solvent usage, ISTE should be useful to determine overall fatty acid composition of foods.