Enzyme function in organic solvents

Abstract

Enzyme catalysis in organic solvents is being increasingly used for a variety of applications. Of special interest are the cases in which the medium is predominantly non-aqueous and contains little water. A display of enzyme activity, even in anhydrous solvents (water <0.02% by vol.), perhaps reflects that the minimum necessity for water is for forming bonds with polar amino acids on the enzyme surface.The rigidity of enzyme structure at such low water content results in novel substrate specificities, pH memory and the possibility of techniques such as molecular imprinting. Limited data indicates that, while enhanced thermal stability invariably results, the optimum temperature for catalysis may not change. If true in general, this enhanced thermostability would have extremely limited benefits.Medium engineering and biocatalyst engineering are relevant techniques to improve the efficiency and stability of enzymes in such low water systems. Most promising, as part of the latter, is the technique of protein engineering.Finally, this review provides illustrations of applications of such systems in the diverse areas of organic synthesis, analysis and polymer chemistry.For a classical biochemist, it was difficult to visualize enzymes catalyzing reactions in the absence of water, i.e. in non-aqueous media. Addition of organic solvents was done either to precipitate enzymes or to study denaturation. Thus, the study of enzyme action in organic solvents is a comparatively recent aspect of enzymology. Singer (1962) reviewed the status of this area and referred to it as a 'rapidly developing area of biophysical chemistry'. While we have made only limited advances since then in our understanding of biophysical chemistry of non-aqueous enzymology, its biotechnological implications have resulted in an explosive growth of the literature (Linhardt, 1986; Dordick, 1988).

Novel biocatalytic esterification reactions on fatty acids: synthesis of sorbitol 1(6) - monostearate

“…are being used now even though the precursor sugar is not soluble in them. 16 Investigations on these solvents has, however, revealed that as the reaction proceeds, reactants dissolve because of the higher solubility of the ester formed in such non-polar solvents. Similar results were obtained in the present investigation for synthesis of sorbitol 1(6) -monostearate in n-hexane which perhaps is industrially compatible, non-toxic, has a low boiling point and thus can easily be removed from the reaction system.…”

Real-time ESI-MS of Enzymatic Conversion: Impact of Organic Solvents and Multiplexing

“…17 Additionally, for several applications in biotechnology and analytical chemistry, the use of organic solvents offers advantages and enables several new applications in industry, these have been discussed in detail in the literature. 12,18 Another promising approach to studying enzymatic reactions is the development of multiplexed assays with two or more different enzymes and their substrates in one single experiment. This can easily be handled by ESI-MS, as long as the compounds have different m/z ratios.…”

Development of small-size tubular-flow continuous reactors for the analysis of operational stability of enzymes in low-water systems

“…This conclusion holds just as clearly for biocatalytic processes in low-water media (Dordick, 1992;Gupta, 1992;Tramper et al, 1992). However, preliminary experiments to design nonaqueous industrial bioreactors are often made using batch reactors.…”