Abstract
It is generally recognized that the small level of remaining water is critical to the behavior of biocatalysts used in mainly non-aqueous (e.g., organic) media. Most biocatalysts are inactive if fully dehydrated, and the reaction rate is stimulated by increasing hydration, at least at first. The rate of the desired reaction can become slower again if water levels increase too much, particularly when a hydrolytic side reaction becomes significant. The water level will also affect the equilibrium position of reactions in which it is a reactant. Most often, the desired synthesis will be the reversal of a hydrolysis or in competition with a hydrolytic side reaction. In such cases, the equilibrium yield will increase as the water level is reduced. Fuller details of these effects of water can be found in recent reviews of the field ( 1-7 ). Some further examples are found elsewhere in this volume (Chapters 12 and 13).
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References
De Gomez-Puyou, M. T. and Gomez-Puyou, A. (1998) Enzymes in low water systems. Crit. Rev. Biochem. Mol. Biol. 33, 53–89.
Klibanov, A. M. (1997) Why are enzymes less active in organic solvents than in water? Trends Biotechnol. 15, 97–101.
Lortie, R. (1997) Enzyme catalyzed esterification. Biotechnol. Adv. 15, 1–15.
Vermue, M. H. and Tramper, J. (1995) Interrelations of chemistry and biotechnology 5. Biocatalysis in nonconventional media-medium engineering aspects. PureAppl. Chem. 67, 345–373.
Carrea, G, Ottolina, G., and Riva, S (1995) Role of solvents in the control of enzyme selectivity in organic media. Trends Biotechnol. 13, 63–70.
Bell, G., Halling, P. J., Moore, B. D., Partridge, J., and Rees, D. G. (1995) Biocatalyst behaviour in low-water systems. Trends Biotechnol. 13, 468–473.
Koskinen, A. and Klibanov, A. M. (1995) Enzymatic Reactions in Organic Media, Chapman & Hall, Andover.
Halling, P. J. (1994) Thermodynamic predictions for biocatalysis in non-conventional media: theory, tests and recommendations for experimental design and analysis. Enzyme Microb. Technol. 16, 178–206.
Cassells, J. M. and Halling, P. J. (1988) Effect of thermodynamic water activity on thermolysin-catalysed peptide synthesis in organic two-phase systems. Enzyme Microb. Technol. 10, 486–491.
Greenspan, L. (1977) Humidity fixed points of binary saturated aqueous solutions. J. Res. Natl. Bur. Stand. A 81A, 89–96.
Valivety, R. H., Halling, P. J., and Macrae, A. R. (1992) Rhizomucor miehei lipase remains highly active at water activity below 0.0001. FEBS Lett. 301, 258–260.
Bell, G., Janssen, A. M. S., and Halling, P. J. (1997) Water activity fails to predict critical hydration level for enzyme activity in polar organic solvents: interconversion of water concentrations and activities. Enzyme Microb. Technol. 20, 471–477. (Because of printing errors in the calculations appendix of this article, a correct version is given as an appendix in this chapter.)
Parker, M. C., Moore, B. D., and Blacker, A. J. (1995) Measuring enzyme hydration in nonpolar organic-solvents using NMR. Biotechnol. Bioeng. 46, 452–458.
Dolman, M., Halling, P. J., Moore, B. D., and Waldron, S. (1997) How dry are anhydrous enzymes? (Measurement of residual and buried 18-O labelled water molecules using mass spectrometry.) Biopolymers 41, 313–321.
Partridge, J., Halling, P. J., and Moore, B. D. (1998) A practical route to high activity enzyme preparations for synthesis in organic media. J. Chem. Soc. Chem. Commun. 841,842.
Izumoto, E., Fukuda, H., and Nojima, Y. (1992) Feedforward/feedback control of interesterification of fats and oils using a microaqueous bioreactor. Chem. Eng. Sci. 47, 2351–2356.
Goldberg, M., Thomas, D., and Legoy, M.-D. (1990) The control of lipasecatalysed transesterification and esterification reaction rates. Effects of substrate polarity, water activity and water molecules on enzyme activity. Eur. J. Biochem. 190, 603–609.
Goldberg, M., Thomas, D., and Legoy, M.-D. (1990) Water activity as a key parameter of synthesis reactions: the example of lipase in biphasic (liquid/solid) media. Enzyme Microb. Technol. 12, 976–981.
Khan, S. A., Halling, P. J., and Bell, G. (1990) Measurement and control of water activity with an aluminium oxide sensor in organic two-phase reaction systems for enzymic catalysis. Enzyme Microb. Technol. 12, 453–458.
Rosell, C. M., Vaidya, A. M., and Halling, P. J. (1996) Continuous in-situ water activity control for organic phase biocatalysis in a packed bed hollow fiber reactor. Biotechnol. Bioeng. 49, 284–289.
Ujang, Z., Alsharbati, N., and Vaidya, A. M. (1997) Organic-phase enzymatic esterification in a hollow fiber membrane reactor with in situ gas-phase water activity control. Biotechnol. Prog. 13, 39–42.
Napier, P. E., Lacerda, H. M., Rosell, C. M., Valivety, R. H., Vaidya, A. M., and Halling, P. J. (1996) Enhanced organic phase enzymatic esterification with continuous water removal in a controlled air-bleed evacuated-headspace reactor. Biotechnol. Prog. 12, 47–50.
Halling, P. J. (1992) Salt hydrates for water activity control with biocatalysts in organic media. Biotecnol. Technol. 6, 271–276.
Zacharis, E., Omar, I. C., Partridge, J., Robb, D. A., and Halling, P. J. (1997) Selection of salt hydrate pairs for use in water control in enzyme catalysis in organic solvents. Biotechnol. Bioeng. 55, 367–374.
Rosell, C.M. and Vaidya, A. M. (1995) Twin-core packed bed reactors for organic phase enzymatic esterification with water activity control. Appl. Microbiol. Biotechnol. 44, 283–286.
Hessbruegge, B. J. and Vaidya, A. M. (1997) Preparation and characterization of salt hydrates encapsulated in polyamide membranes. J. Membrane Sci. 128, 175–182.
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Bell, G. et al. (2001). Methods for Measurement and Control of Water in Nonaqueous Biocatalysis. In: Vulfson, E.N., Halling, P.J., Holland, H.L. (eds) Enzymes in Nonaqueous Solvents. Methods in Biotechnology, vol 15. Humana Press. https://doi.org/10.1385/1-59259-112-4:105
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DOI: https://doi.org/10.1385/1-59259-112-4:105
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