Whole-cell Systems and Enzymes other than Lipases in Ionic Liquids

Whole-cell Systems and Enzymes other than Lipases in Ionic Liquids 

In 1984, Magnuson et al. (Entry 1) investigated the influence of ethylammoni-um/water mixtures on enzyme activity and stability [29]. At low [H3NEt][N03] concentrations, an increased activity of alkaline phosphatase was found. The same ionic liquid was used by Flowers and co-workers, who found improved protein refolding after denaturation (Entry 2) [30]. 

The recovery of n-butanol from a fermentation broth in a similar way has been investigated by in situ extraction with [BMIM][PF(3] (Entry 5) [33]. 

In the first publication describing the preparative use of an enzymatic reaction in ionic liquids, Erbeldinger et al. reported the use of the protease thermolysin for the synthesis of the dipeptide Z-aspartame (Entry 6) [34]. The reaction rates were comparable to those found in conventional organic solvents such as ethyl acetate. Additionally, the enzyme stability was increased in the ionic liquid. The ionic liquid was recycled several times after the removal of non-converted substrates by extraction with water and product precipitation. Recycling of the enzyme has not been reported. It should be noted, however, that according to the log P concept described in the previous section, ethyl acetate - with a value of 0.68 - may interfere with the pro- 

Iborra and co-workers (Entry 8) examined the transesterification of N-acetyl-i-tyrosine ethyl ester in different ionic liquids and compared their stabilizing effect relative to that found with 1-propanol as solvent [36]. Despite the fact that the enzyme activity in the ionic liquids tested reached only 10 to 50 % of the value in 1-propanol, the increased stability resulted in higher final product concentrations. Fixed water contents were used in both studies. 

Entry Biocatalyst Ionic liquid Reaction system Ref. 

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Table 8.3-1 Whole-cell systems and enzymes other than lipases in ionic liquids. 

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