Importance of Enzyme Formulation for the Activity and Enantioselectivity of Lipases in Organic Solvents

Abstract

5.1 IntroductionLipases are of remarkable practical interest since they have been used in numerous biocatalytic applications, such as kinetic resolution of alcohols and carboxyl esters (both in water and in non -aqueous media) [1] , regioselective acylations of polyhydroxylated compounds, and the preparation of enantiopure amino acids and amides [2,3] . Moreover, lipases are stable in organic solvents, do not require cofactors, possess broad substrate specifi city, and exhibit, in general, a high enantioselectivity. All these features have contributed to make lipases the class of enzyme with the highest number of biocatalytic applications carried out in neat organic solvents.The use of organic solvents is especially advantageous in transforming substrates that are unstable or poorly soluble in water. Furthermore, in the absence of water, the synthesis of ester and amide bonds by hydrolases (mainly lipases and proteases) can be favored over hydrolysis and many side reactions that are water dependent can be prevented. By varying the organic solvent it is also possible to control the substrate specifi city and the regio -and enantioselectivity of a given enzyme. However, although enzymes in organic media show numerous advantages, their catalytic effi ciency is, in most cases, orders of magnitude lower than in aqueous systems. This behavior can be ascribed to different causes such as high saturating substrate concentrations, diffusional limitations, low stabilization of the transition state of the enzyme -substrate intermediate, restricted protein fl exibility, and aggregation and distortions of the enzyme molecules caused by dehydration, which become irreversible in anhydrous solvents [4] .The present chapter briefl y examines and discusses the effects of some additives, namely lyoprotectants (sugars, crown ethers, and methoxypoly(ethylene glycol)), on the activity and enantioselectivity of several lipases. A possible rationale for the increment usually observed when using lyoprotectants, on the basis of conformational data obtained by means of Fourier -transform infrared (FT -IR) spectroscopy is also suggested.

Enhancing the Productivity and Stability of Superoxide Dismutase from Saccharomyces cerevisiae TBRC657 and Its Application as a Free Radical Scavenger

“…Thus, water molecules will be removed from the target protein, forming a more compact structure. Some additives can form a hydrophobic interaction with the target enzyme, leading to reduced movement and also reduced water activity of the enzyme, which causes the formulated enzymes to be more stable in the environment [41][42][43][44]. Thus, these top 3 formulated SODs were selected and further analyzed for their SOD activities and storage stability at 4 • C for 6 months.…”