The use of biocatalysis for industrial synthetic chemistry is on the verge of significant growth. Biocatalytic processes can now be carried out in organic solvents as well as aqueous environments, so that apolar organic compounds as well as water-soluble compounds can be modified selectively and efficiently with enzymes and biocatalytically active cells. As the use of biocatalysis for industrial chemical synthesis becomes easier, several chemical companies have begun to increase significantly the number and sophistication of the biocatalytic processes used in their synthesis operations.

Industrial biocatalysis today and tomorrow

Mechanisms of membrane toxicity of hydrocarbons.

Photophysics, photochemistry and solar energy conversion with tris(bipyridyl)ruthenium(II) and its analogues

General rules for the optimization of different biocatalytic systems in various types of media containing organic solvents are derived by combining data from the literature, and the logarithm of the partition coefficient, log P, as a quantitative measure of solvent polarity. (1) Biocatalysis in organic solvents is low in polar solvents having a log P 4. It was found that this correlation between polarity and activity parallels the ability of organic solvents to distort the essential water layer that stabilizes the biocatalysts. (2) Further optimization of biocatalysis in organic solvents is achieved when the polarity of the microenvironment of the biocatalyst (log P(i)) and the continuous organic phase (log P(cph)) is tuned to the polarities of both the substrate (log P(s)) and the product (log P(p)) according to the following rules: |log P(i) - log P(s)| and |log P(cph) - log P(p)| should be minimal and |log P(cph) - log P(s)| and |log P(i) - log P(p)| should be maximal, with the exception that in the case of substrate inhibition log P(i), should be optimized with respect to log P(s) In addition to these simple optimization rules, the future developments of biocatalysis in organic solvents are discussed.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/bit.22209

Rules for optimization of biocatalysis in organic solvents

Enzymatic catalysis in nonaqueous solvents.

20β-Hydroxysteroid dehydrogenase was enclosed in reversed micellar media consisting of cetyltrimethyl-ammonium bromide, hexanol, organic solvent and Hepes buffer. The influence of the composition of these media on the enzymatic reduction of the apolar steroids progesterone and prednisone was investigated by varying the water content, concentration of hexanol and type of organic solvent. By changing the water content and the type of organic solvent, the hexanol to cetyltrimethylammonium bromide ratio in the interphase can be varied. This ratio was determined by phase boundary titrations. It was found that the higher this ratio, the higher the rate of steroid conversion. From variations of the hexanol content it was concluded that the rate of steroid conversion is determined by the hydrophobicity of the steroid relative to the hydrophobicity of the continuous phase and the hydrophobicity of the interphase. The hydrophobicity of the phases was expressed in log P-values. Log P is defined as the logarithm of the partition coefficient in an octanol-water two-phase system. This enabled us to derive the following relations between the hydrophobicity values for the substrate (log Ps), for the interphase (log Pi) and for the continuous phase (log Pcph): |log Pi-log Ps| must be minimal to ensure a high steroid concentration in the interphase and |log Pcph-log Ps| must be large to keep the steroid concentration in the continuous phase low. With these considerations, for any given apolar compound, a medium can be composed that gives optimal enzymatic conversion.

Rules for the regulation of enzyme activity in reserved micelles as illustrated by the conversion of apolar steroids by 20β-hydroxysteroid dehydrogenase

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2883%2980451-7

Enzymatic conversion of apolar compounds in organic media using an NADH-regenerating system and dihydrogen as reductant

Rules for optimization of biocatalysis in organic solvents. Biotechnol Bioeng 1986; 30: 81-7.

Hydrogenase (hydrogen:ferricytochrome c3 oxidoreductase, EC 1.12.2.1) from Desulfovibrio vulgaris was encapsulated in reversed micelles with cetyltrimethylammonium bromide as surfactant and a chloroform/octane mixture as solvent. Reducing equivalents for hydrogenase-catalyzed hydrogen production were provided by vectorial photosensitized electron transfer from a donor (thiophenol) in the organic phase through a surfactant-Ru2+ sensitizer located in the interphase to methyl viologen concentrated in the aqueous core of the reversed micelle. The results show that reversed micelles provide a microenvironment that (i) stabilizes hydrogenase against inactivation and (ii) allows an efficient vectorial photosensitized electron and proton flow from the organic phase to hydrogenase in the aqueous phase.

https://www.pnas.org/content/pnas/79/12/3927.full.pdf

Colja Laane

Papers

Rules for optimization of biocatalysis in organic solvents

Rules for the regulation of enzyme activity in reserved micelles as illustrated by the conversion of apolar steroids by 20β-hydroxysteroid dehydrogenase

Enzymatic conversion of apolar compounds in organic media using an NADH-regenerating system and dihydrogen as reductant

Rules for optimization of biocatalysis in organic solvents. Biotechnol Bioeng 1986; 30: 81-7.

Photosensitized production of hydrogen by hydrogenase in reversed micelles.