Bioreactors with immobilized lipases: state of the art.

Although protein function is thought to depend on flexibility, precisely how the dynamics of the molecule and its environment contribute to catalytic mechanisms is unclear. We review experimental and computational work relating to enzyme dynamics and function, including the role of solvent. The evidence suggests that fast motions on the 100 ps timescale, and any motions coupled to these, are not required for enzyme function. Proteins where the function is electron transfer, proton tunneling, or ligand binding may have different dynamical dependencies from those for enzymes, and enzymes with large turnover numbers may have different dynamical dependencies from those that turn over more slowly. The timescale differences between the fastest anharmonic fluctuations and the barrier-crossing rate point to the need to develop methods to resolve the range of motions present in enzymes on different time- and lengthscales.

The role of dynamics in enzyme activity

This review analyzes the role of cutinases in nature and their potential biotechnological applications. The cloning and expression of a fungal cutinase, Fusarium solani f. pisi, in Escherichia coli and Saccharomyces cerevisiae hosts are described. The three-dimensional structure of this cutinase is also analyzed and its function as a lipase is discussed and compared with other lipases. The biocatalytic applications of cutinase are described taking into account the preparation of different cutinase forms and the media in which the different types of reactions have been performed, namely hydrolysis, esterification, transesterification, and resolution of racemic mixtures. The stability of cutinase preparations is discussed and, in particular, the cutinase stability in anionic reversed micelles is analyzed considering the role of hexanol as a substrate, a cosurfactant, and a stabilizer. Process development, based on the operation of cutinase reactors, is also reviewed.

Cutinase: from molecular level to bioprocess development.

Enzymatic reactions in nonaqueous solvents offer new possibilities for the biotechnological production of many useful chemicals using reactions that are not feasible in aqueous media. In the recent years, the use of enzymes in nonaqueous media has found applications in organic synthesis, chiral synthesis or resolution, modification of fats and oils, synthesis of sugar-based polymers, etc. The use of lipases in esterification reactions to produce industrially important products such as emulsifiers, surfactants, wax esters, chiral molecules, biopolymers, modified fats and oils, structured lipids, and flavor esters is well documented. The interest in using lipases as biotechnological vectors for performing various reactions in both macro- and microaqueous systems has picked up tremendously during the last decade. This review covers important features of lipases and lipase-catalyzed esterification reactions including the kinetics and stability of lipases, and modeling aspects.

Lipases and lipase-catalyzed esterification reactions in nonaqueous media

Supercritical fluids are materials above their critical point that represent a unique class of nonaqueous media for biocatalysis and bioseparation. The inherent gas-like low viscosities and high diffusi vities of supercritical fluids increase the rates of mass transfer of substrates to enzyme. Conversely, the liquid-like densities of supercritical fluids result in higher solubilizing power than those observed for gases. Unlike the behavior of gases and liquids, the physical properties of a supercritical fluid can be adjusted over a wide range by a relatively small change in pressure or temperature. In a supercritical fluid, the careful regulation of the density enables reactant and product solubility to be controlled, thus simplifying downstream separations. The extraction power of supercritical carbon dioxide has been used extensively in both the chemical and food industries.The use of supercritical fluids as a dispersent for biocatalysis was first described in 1985, and there is now a growing tr...

Enzyme Activity in Supercritical Fluids

Many products which are useful in the fine chemical, flavor, and petrochemical industries are insoluble in an aqueous phase. An obvious solution is the use of organic solvents for the solubilization of such com- poUnds~~.l~,11.~9-21 However, even if the organic solvents truly solubilize these products, they may act as dena- turants for biocatalyst a~tivity.~ Intermediate possibili- ties can be sought, such as the use of mixed aqueous- organic media, emulsions, or microemulsions.’3-’s This article describes the use of a new, original tech- nology based on the implementation of a continuous gas-solid bioreactor, in which the biocatalyst (used as a lyophilized powder) is the solid phase and the substrates are gaseous. The temperature of reactor operation depends on the particular enzymes and substrates. This type of biore- actor presents many advantages: It is a continuous reactor; substrates continuously en- ter the reactor and products continuously leave the reactor. The substrates are pure; there is no addition

https://onlinelibrary.wiley.com/doi/pdf/10.1002/bit.260390415

Firooze Parvaresh

Papers

Gas phase transesterification reactions catalyzed by lipolytic enzymes