Evaluation of Binary Solvent Mixtures for Efficient Monoacylglycerol Production by Continuous Enzymatic Glycerolysis

Abstract

This study was aimed at evaluating different binary solvent mixtures for efficient industrial monoacylglycerol (MAG) production by enzymatic glycerolysis. Of all investigated cases, the binary mixture of tert-butanol:tert-pentanol (TB:TP) 80:20 vol % was the most suitable organic medium for continuous enzymatic glycerolysis, ensuring high MAG formation in a short time, reasonable solvent price, and easy handling during distillation/condensation processing. A minimum solvent dosage of 44-54 wt % of the reaction mixture was necessary to achieve high MAG yields of 47-56 wt %, within 20 min. The melting and boiling points of the TB:TP mixture were estimated to be 7 and 85 degrees C, respectively, using thermodynamic models. These predictions were in good agreement with experimentally determined values. In spite of the high reaction efficiency in the binary TB:TP system, the mixture of glycerol and sunflower oil (containing 97.1% triacylglycerol) yielded surprisingly a liquid/liquid phase split behavior even at high temperatures (>80 degrees C). This in contrast to thermodynamic model calculations suggested full miscibility in all proportions. These findings suggest that enhanced reaction efficiency in organic solvent also depends upon aspects other than the system homogeneity such as reduced viscosity, reduced mass transfer limitations, and the accessibility of the substrate to the active site of the enzyme.

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

“…For decades, attempts have been made to develop a compatible system by simply mixing conventional solvents, or to adjust the hydrophobic-hydrophilic properties of media through conventional solvent engineering, particularly for changing equilibrium shift toward the desired products (Damstrup et al, 2006;Endó n et al, 2001). However, the manipulation space for property tuning using simple molecular solvents is very limited due to either their limited numbers or types of solvation interactions possible with dissolved molecules (Anderson et al, 2002).…”

“…Figure 1 summarizes the typical time courses of lipasecatalyzed glycerolysis of triolein in the ILs with varied cation substituents and differing anions, corresponding to the moiety details listed in Table I. Generally, conversion of oils and percentage of desired product (denoting the specificity of a multi-step reaction) are used as indexes to characterize a glycerolysis reaction (Damstrup et al, 2006;Sonntag, 1982). The particularity of evolution profile pertaining to a reaction can sometimes serve as a fingerprint to authenticate the reaction system.…”

Liquid–liquid equilibria for systems glycerol+sardine oil+tert-alcohols

“…Based on the different values of the dielectric constant for the two tert-alcohols studied in this work, it seems reasonable that tie lines for the tertbutanol system present positive slope since glycerol present a high value of the dielectric constant (ε glycerol, 25ºC = 42.5), specially when comparing this value with the dielectric constant of fish oil (ε fish oil, 25ºC = 2.76) [21]. The differences observed in the log P for tertbutanol and tert-pentanol (log P tert-butanol = 0.35 and log P tert-pentanol = 0.89) could also support the different slope observed in the tie lines [5].…”

Computer-aided solvent screening for biocatalysis

“…One could therefore argue that the alcohol group should be excluded from the basis sets, in order to have no primary and secondary alcohols included. However, in group contribution based CAMD, that would also exclude tertiary alcohols -a frequent biocatalytic medium [14,41,44]. Therefore, the alcohol group is retained.…”

“…In spite of this, computer-aided solvent selection methods seem not to have penetrated the biocatalysis community yet. In fact, biocatalytic reaction media are mostly selected based on past experience and 'mix-and-test' experiments [14,15,16]. Progress in modeling enzymatic solutions will undoubtedly continue, but achieving reliable prediction without measured data is unlikely.…”