Conversion of Caprylic Acid into Mono-, Di- and Triglycerides Using Immobilized Lipase

Abstract

Monoacylglycerols (MAG), diacylglycerols (DAG) and triacylglycerols (TAG) are emulsifiers widely used in the food, pharmaceutical and cosmetic industries. These molecules can be synthesized using lipase as biocatalyst resulting in more pure and not degraded lipids. The objective of this paper was the esterification of caprylic acid and glycerol, using an immobilized sn-1,3-specific lipase from Rhizomucor miehei (Lipozyme RM IM) as biocatalyst to produce MAG, DAG and TAG. Reactions were carried out in a batch-type reactor at different temperatures and molar ratios of caprylic acid to glycerol. A $2^{2}$ factorial experimental design was chosen to investigate the effects of temperature from 30 to $70 \,^{\circ }\hbox {C}$ and molar ratios of glycerol to caprylic acid ranging between 1:2 and 1:6. The reaction yield was calculated from the remaining free fatty acids in the reaction medium, as determined by titration, and from the amount of caprylins produced, as determined by gas chromatography. Response surface methodology was employed to evaluate the optimal conditions to obtain the highest yield. The chosen reaction parameters yielded an adequate production of MAG, DAG and TAG, and the highest output (88%) was achieved under intermediate temperature/molar ratio ($50\,^{\circ }\hbox {C}$/1:2) conditions. In order to reduce production costs, reuse of lipase was evaluated by running three consecutive batches on a microfiltration-membrane-coupled bioreactor and on a regular bioreactor (no membrane). Results showed the microfiltration-membrane-coupled bioreactor to be more efficient, since there was only a 10% decrease in the initial reaction yield after three consecutive esterification reactions.