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Effects of solvent, water activity and temperature on lipase and hydroxynitrile lyase enantioselectivity

In English

Författare

Summary, in English

The influence of the reaction conditions on the enantioselectivity of reactions catalysed by lipases or hydroxynitrile leases (HNLs) in organic solvents was investigated. The lipases catalysed kinetic resolution of chiral secondary alcohol, or chiral carboxylic acids and the HNLs catalysed asymmetric addition of hydrogen cyanide to aldehydes. The temperature effects on enantioselectivity, were studied in detail. From measurements of the enantiomeric ratio (C) at different temperatures the activation parameters DeltaDeltaH(#) and DeltaDeltaS(#) were determined. In the lipase-catalysed reactions the enthalpic and entropic effects on E always counteracted, while in a few of the HNL-catalysed reactions, DeltaDeltaH(#) and DeltaDeltaS(#) had opposite sign, and therefore the effects cooperated to give high E values (-RTInE = DeltaDeltaG(#) = DeltaDeltaH(#) - TDeltaDeltaS(#)). In all the HNL-catalysed reactions and most of the lipase-catalysed ones, the enantioselectivity increased with decreasing reaction temperature. However, in one of the lipase-catalysed reactions, the enantioselectivity decreased with decreasing temperature. The theoretical background of these observations wars discussed. In the HNL-catalysed reactions, the enantioselectivity increased with increasing water content up to water saturation, while in the lipase-catalysed reactions the opposite trend was found in one case and in the others no significant effect was observed. Solvent mixtures of diisopropylether and hexane were used to obtain solvents with different log P values. The log P value of the solvent did not influence the enantioselectivity in the HNL-catalysed reactions. while the enantioselectivity increased with increasing log P value in two of the lipase-catalysed reactions. The reaction temperature was shown to be a very useful way to influence enzyme selectivity and the effects obtained could be rationalised. The influence of the reaction medium (solvent and water activity) is much more difficult to rationalise and predict. (C) 2002 Elsevier Science Inc. All rights reserved.

Publiceringsår

2002

Språk

Engelska

Sidor

916-923

Publikation/Tidskrift/Serie

Enzyme and Microbial Technology

Volym

30

Issue

7

Dokumenttyp

Artikel i tidskrift

Förlag

Elsevier

Ämne

  • Industrial Biotechnology

Nyckelord

  • temperature
  • hydroxynitrile lyase
  • enantioselectivity
  • lipase
  • water
  • activity
  • organic solvent

Status

Published

ISBN/ISSN/Övrigt

  • ISSN: 0141-0229