Structures of ionic liquids dictate the conversion and selectivity of enzymatic glycerolysis: Theoretical characterization by COSMO‐RS

Abstract

Lipase-catalyzed glycerolysis of triolein has been examined using a group of tetraammonium-based ionic liquids (ILs) as media, specifically with functional groups in cation part. The results demonstrated that the reaction evolution and profile specificity of respective IL system could be quantitatively associated with the structural characteristics of the IL by means of quantum chemical and COSMO-RS calculation. Misfit interaction, Van der Waals interaction and chemical potential, etc. derived from COSMO-RS calculation are shown to be effective measures to delineate multiple interactions of ILs and then can be used to understand the effects of ILs on reactions. The hydrophobic substituents in the cation are found to contribute to the increase of triolein solubility and enhancement of initial reaction rate; while strong polar anion and polyethoxyl and free hydroxyl groups in the cation part dictate improved product selectivity through reducing activity coefficients of monoglycerides. Integration of these structures into the same molecule constitutes a promising group of ILs that could produce over 90% monoglyceride with almost 100% triglyceride conversion, as well as bulky productivity, of particular potential for industrial applications. Overall, this work has presented a first attempt to characterize the IL structure-dependency of reaction specificity by associating structural variations of ILs with thermodynamic property changes of resided compounds and subsequent effects on reaction specificity. This might be of general value to help to understand the multiple solvation interaction among IL reaction systems at molecular level and promote the application of IL-mediated reactions to practical interests.

Methods for stabilizing and activating enzymes in ionic liquids—a review

“…4 4 ] than in PF 6 − and BF 4 − based ILs. Xu and co-workers 183,185 utilized the conductorlike screening model for real solvents (COSMS-RS) to derive various parameters (such as misfit, H-bonding and van der Waals interaction energy) to understand the multiple interactions in ILs; the model also provides guidance in designing the structures of cations and anions. 190 The Kragl group 191 found that an IL in the Ammoeng family -Ammoeng 110 ( Fig.…”

Predictions of flavonoid solubility in ionic liquids by COSMO-RS: experimental verification, structural elucidation, and solvation characterization

“…However, those descriptions could not or at least have not been associated with the quantification of the thermodynamic properties of ILs, which is just the need for a practical application 26 . (Fig.…”

Characterization of ionic liquid‐based biocatalytic two‐phase reaction system for production of biodiesel

“…The ionic nature of ILs to strip of the essential water for catalysis action of enzyme has been suggested to be responsible for the lower activity of lipases in IL environment; however, Candida antarctica lipase B is structurally unique that could bind the essential water for catalysis and consequently works well at low water activities. 35 …”

“…For a multistep reaction, examination of the changes of activity coefficients of intermediate and end products in different biphasic systems with reaction evolution might be a good start to probe into the intrinsic reasons accounting for respective reaction specificity. 35 To simplify the simulation of the reaction progress, the following assumptions are established based on the observed characteristics of representative IL reaction system for enzymatic production of biodiesel (typically as in Ammoeng 102; Figure 1A): (1) this prediction is based on 1 mol triolein reacted with 3 mol methanol using 1 mol IL as a medium; (2) this work focuses on the partition coefficients of the end products (glycerol and biodiesel), all other components treated as part (composition) of two phases; (3) the formation of intermediate products (MG and DG) are treated as a steady state that the accumulation of MG and DG is neglected; (4) regarding the mutual solubilities of solvents, oil (TG and/or biodiesel, changing with reaction evolution) concentrations in ILs are estimated by COSMO-RS calculation at an infinite mode; and the solubilities of methanol, glycerol, and ILs in oil phase are omitted; (5) the volumes of oil phase (TG and biodiesel) and IL phase (IL, TG, biodiesel, methanol, and glycerol) are the sum of volume contributions from the compositions. Partition coefficients of biodiesel and glycerol in oil and IL phases (Ammoeng 102 and 120) are thus calculated on the basis of the above assumptions (Figure 2A).…”

“…The solubility of triglycerides in ILs has been suggested being a crucial factor to determine the reaction rate of enzymatic glycerolysis in IL-based systems 35 ; such that, the solubilities of triolein in the evaluated ILs have been predicted by COSMO-RS (Table 3). Clearly, the reaction degrees show a certain correspondence with the oil solubilities in the ILs The plotted measured data in (B) are means AE standard deviations (error bars) of three determinations.…”