Solvent effects on biocatalysis in organic systems: Equilibrium position and rates of lipase catalyzed esterification

Abstract

Porcine pancreatic lipase immobilized on celite particles has been employed as a catalyst for the esterification of dodecanol and decanoic acid in a predominantly organic system. Solvent influence on the equilibrium position and on the catalyst activity has been studied using 20 solvents, including aliphatic and aromatic hydrocarbons, ethers, ketones, nitro- and halogenated hydrocarbons, and esters. The equilibrium constant for esterification correlates well with the solubility of water in the organic solvent, which in turn shows a good relationship with a function of Guttman's donor number and the electron pair acceptance index number of the solvent. This may be rationalized in terms of the requirements for solvation of water and of the reactants. The catalyst activity, measured as the initial rate of the esterification reaction, is best correlated as a function of both n-octanol-water partition coefficient (log P) and either the electron pair acceptance index or the polarizability.

Modeling the effect of free water on enzyme activity in immobilized lipase-catalyzed reactions in organic solvents

“…The influence of the solvent on catalytic activity may be explained by its ability to affect water-enzyme interactions and also its ability to penetrate into the essential layer of water that stabilizes the enzyme. Water is not displaced from the enzyme by the solvent because water saturated solvents also influence catalytic activity [11]. The key parameter relating to non-polar solvents that best fits the catalytic activity, is the logarithm of the octanol-water partition coefficient (log P) [11][12][13].…”

“…Water is not displaced from the enzyme by the solvent because water saturated solvents also influence catalytic activity [11]. The key parameter relating to non-polar solvents that best fits the catalytic activity, is the logarithm of the octanol-water partition coefficient (log P) [11][12][13]. This parameter is a measure of the behavior of separated molecules of the solvent dissolved in water and therefore is a good measure of the ability of the solvent to penetrate into the enzyme-bound aqueous layer.…”

Biocatalysis in non-conventional media: Medium engineering aspects (Technical Report)

“…LgPoctanol is thus not always a good parameter to predict the toxic effects of solvents in enzymic reactions and in some cases other parameters of solvents polarity, such as the Dimroth-Reichardt parameter b ( 3 0 ) (VazquezDuhalt et al, 1993), predict enzyme activity better. LgPoctanol in combination with either electron-pair-acceptance index or polarizability of the solvent has been used successfully to correlate the initial rate of a porcine pancreatic lipase-catalysed esterification reaction (Valivety et al, 1991). In this approach direct polar interactions between the solvent and the enzyme (or the relatively polar phase around the enzyme) are accounted for.…”

Computer-aided solvent screening for biocatalysis

“…The application of this classical thermodynamic approach to biocatalytic reactions has been discussed by several investigators [33,34,39]. Calculations have been described by Shen et al [40] and later by Stamatis et al [39].…”

“…Extraction based (biphasic) systems seem most suited for reactions with hydrophobic products [33,34,35]. Laane et al [9] generalized the validity of the correlations between free-and immobilized cell activities and log P to enzymatic reactions in (nearly) anhydrous organic media, based on data of Zaks and Klibanov [36].…”