Chemistry Reference
In-Depth Information
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Fig. 6.6
Arrhenius plots for N435-catalysed polyesterification of siloxane-containing monomers;
disiloxane diol (
hollow circles
) and polysiloxane diol (
black-filled circles
)
processed an average of 93 % of the 1-octanol within the allotted time period. Every
batch that was assayed retained in excess of 95 % of its relative activity. Previous
works have reported between 5 and 80 % residual activities for recovered enzymes
[
14
,
21
,
22
].
While it is difficult to account for the different processing parameters that have
been employed, it generally appears that hydrophobic substrates tend to favour
higher residual activity. This is perhaps not surprising given the native environment
in which lipases have evolved to function. Silicones are known to be some of the
most hydrophobic materials, and as such disiloxane polyesters should offer a suit-
able environment for a lipase to function.
6.8
Thermal Tolerance and Repeated
Use of Novozyme-435
In order for biocatalysis to be viable on an industrial scale the catalyst must be cost
efficient, reusable and reliably perform he desired reactions with high selectivity
and turnover. In light of the high residual activity of N435 after prolonged expo-
sure to elevated temperatures it was of interest to determine the long-term thermal
