Solvent-Free Enzymatic Esterification of Free Fatty Acids with Glycerol for Biodiesel Application: Optimized Using the Taguchi Experimental Method

Themes: Conversion

Keywords: Lipidomics


Singh, R.Dien, B.Singh, V. July 31, 2022. “Solvent-Free Enzymatic Esterification of Free Fatty Acids with Glycerol for Biodiesel Application Optimized Using the Taguchi Experimental Method.” Journal of the American Oil Chemists’ Society 99:781-790. DOI: 10.1002/aocs.12633.


S/N ratio plot of esterification reaction process parameters (a) main plot and (b) interaction plot of S/N ratio.

Presence of free fatty acids along with glycerides poses a technical difficulty for biodiesel production. This work used a Taguchi L9 design to optimize the solvent-free enzymatic process to result in the esterification of oleic acid with glycerol. Under optimal conditions the esterification reaction temperature of 60°C, enzyme dose of 5 wt%, glycerol: oleic acid molar ratio of 5:1, and reaction time of 3 h, a 75.235 ± 2.19% conversion of oleic acid to esters was achieved. With the addition of molecular sieves, the conversion increased to 86.73% ± 1.09%. However, using the parameters predicted by Taguchi design (60°C, 5 wt%, 5:1, and 4.5 h), 88.5% ± 1.11% of oleic acid could be converted to esters derivative. Diglycerides were the major product, and the reaction equilibrium was attained after 4 h. The immobilized enzyme could be used up to seven times with only a 10% reduction in the conversion. Thus, the process can efficiently reduce the free fatty acid content of oil to make it suitable for biodiesel production.


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  • Oleic Acid Esterification Time Course and Profile

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