Abstract
AbstractPickering emulsion systems have emerged as platforms for the synthesis of organic molecules in biphasic biocatalysis. Herein, the catalytic performance was evaluated for biotransformation using whole cells exemplified for the dehydration of n‐octanaloxime to n‐octanenitrile catalysed by an aldoxime dehydratase (OxdB) overexpressed in E. coli. This study was carried out in Pickering emulsions stabilised solely with silica particles of different hydrophobicity. We correlate, for the first time, the properties of the emulsions with the conversion of the reaction, thus gaining an insight into the impact of the particle wettability and particle concentration. When comparing two emulsions of different type with similar stability and droplet diameter, the oil‐in‐water (o/w) system displayed a higher conversion than the water‐in‐oil (w/o) system, despite the conversion in both cases being higher than that in a “classic” two‐phase system. Furthermore, an increase in particle concentration prior to emulsification resulted in an increase of the interfacial area and hence a higher conversion.
Highlights
Enzymes are efficient biocatalysts that, due to their high chemo, regio- and stereo-selectivity, play an important role in the synthesis of organic molecules under mild and sustainable conditions.[1,2,3] Enzymes are commonly active in water, while at the same time often organic substrates are poorly soluble in aqueous media
In the Pickering emulsion system we suggest that the reaction takes place in the aqueous phase as the enzyme, even if it is confined in a cellular matrix, is highly sensitive to organic solvents
We reported the enzymatic dehydration of n-octanaloxime to n-octanenitrile in Pickering emulsions stabilised with silica particles of different hydrophobicity using E. coli cells with OxdB enzyme
Summary
Despite the fraction of coalesced oil being higher and the average droplet diameter is about 10 times larger in the former emulsion, the conversion measured is almost 10 % higher This could indicate that silica particles of different hydrophobicity might interact in a different way with the E. coli cells and this could influence the conversion of the reaction. The conversions measured in the organic phases separated from the emulsions prepared with silica particles of different hydrophobicity are shown in Figure S9(b) (empty circles). Angewandte Chemie International Edition published by Wiley-VCH GmbH www.angewandte.org 1455
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