Lipase‐catalyzed esterification of stearic acid with ethanol, and hydrolysis of ethyl stearate, near the critical point in supercritical carbon dioxide

Abstract

The effect of pressure on the lipase-catalyzed reaction in supercritical carbon dioxide (SCCO 2 ) was investigated for the esterification of stearic acid (SA) with ethanol and the hydrolysis of ethyl stearate (ES) near the critical point, ranging from 6 to 20 MPa in pressure and 35 to 60°C in temperature. The esterification rate of SA began to increase near the critical point and kept increasing steadily with an increase in pressure, reflecting the increase in SA solubility in SCCO 2 . The hydrolysis rate of ES showed a maximum at a pressure near the critical point. When the reaction was carried out with an initial overall ES concentration below its solubility limit in SCCO 2 , the maximum pressure shifted along the extended line of the gas-liquid equilibrium in the supercritical region in the pressure-temperature phase plane. This seems to be related to the singular behavior of some properties in SCCO 2 along this line reported in the literature. These results show the importance of pressure, as well as temperature, as a parameter to control enzyme reactions in SCCO 2 .

Supercritical carbon dioxide as solvent in the lipase-catalyzed ethanolysis of fish oil: Kinetic study

“…Similar results for thermal behaviour of Lipozyme RM IM have been reported in the literature for the synthesis of n-octyl oleate in SC-CO 2[16]. Conversion around 80 % was observed in the range 308 15. 333.15 K at 10 MPa, whereas higher temperatures (343.15 and 353.15 K)led to lower conversion (around 65 %) yet slightly higher initial reaction rates, which may indicate that thermal deactivation is not immediate.…”

“…Different results have been found in the literature regarding the effect of pressure on Lipozyme RM IM-catalyzed reactions in SC-CO 2 . For instance, in the study of esterification of stearic acid with ethanol catalyzed by Lipozyme IM in SC-CO 2 in the range from 6 to 20 MPa at 323.15 K, Nakaya et al [15] found an increase in esterification rate with an increase in pressure, but a maximum was found in the hydrolysis rate of the corresponding ethyl stearate. Laudani et al [16] performed a detailed kinetic and thermodynamic study of the esterification of oleic acid with 1-octanol catalyzed by Lipozyme RM IM in dense carbon dioxide.…”

CO2‐Enabled Biomass Fractionation/Depolymerization: A Highly Versatile Pre‐Step for Downstream Processing

“…Both chemical (e.g., acid) and enzymatic (e.g., lipases) approaches have been developed to be efficient for the hydrolysis of triglycerides, which are the major component of oils and fats . In view of the enzyme specificity and high mass transfer rate of Sc‐CO 2 , oils or fats dissolved in Sc‐CO 2 would be favorable for enzymatic hydrolysis, as well as product separation by simple reduction of the system pressure . Numerous lipases are known to be active in Sc‐CO 2 , including for the hydrolysis of bio‐esters .…”

“…[149,150] In view of the enzyme specificity and high mass transfer rate of Sc-CO 2 ,o ils or fats dissolved in Sc-CO 2 would be favorable for enzymatic hydrolysis, as well as product separation by simple reduction of the system pressure. [151][152][153] Numerousl ipases are known to be active in Sc-CO 2 ,i ncluding for the hydrolysis of bio-esters. [154,155] However,t he moisture content directly affects the lipase catalytic activity,w hereby sufficient water is typically required to make lipasesb ehavea se fficient biocatalysts.…”

Plant Products for Pharmacology: Application of Enzymes in Their Transformations

“…An interesting study has been performed with lipase-catalyzed esterification of stearic acid with ethanol, and subsequent hydrolysis of ethyl stearate under the conditions set near to the critical point in supercritical carbon dioxide (p = 6 to 20 MPa, t = 35 to 60 °C) [ 166 ], resulting in an observation of the esterification rate of stearic acid increasing near the critical point and keeping the increase steady with increasing the pressure, and reflecting the increasing solubility of stearic acid in supercritical medium. The hydrolysis rate of ethyl stearate showed its maximum at a pressure near the critical point, and it was dependent on the initial concentration of ethyl stearate in the system.…”