Summary
The pH of the aqueous phase trapped within biocatalyst particles in organic media may be measured using very hydrophobic esters of fluorescein. These remain completely in a pentan-3-one phase, but they ionise there in response to the pH of an equilibrated aqueous phase. They show that the catalyst pH may be significantly shifted from the pre-adjusted value by partitioning of an acidic reactant (N-formyl-tyrosine during chymotrypsin-catalysed esterification) or product (acetic acid during lipase-catalysed ester hydrolysis).
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Valivety, R.H., Rakels, J.L.L., Blanco, R.M. et al. Measurement of pH changes in an inaccessible aqueous phase during biocatalysis in organic media. Biotechnol Lett 12, 475–480 (1990). https://doi.org/10.1007/BF01086338
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DOI: https://doi.org/10.1007/BF01086338