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During the scale-up of a chemical process to produce phase II supplies of the chiral compound Lotrafiban, partial racemisation occurred to produce drug substance of unacceptable chiral purity. A new route capable of producing several hundred kilograms of Lotrafiban of high chiral purity had to be rapidly identified and scaled up. The strategy adopted was to employ an enzymic resolution as the final step, thus introducing the chirality under very mild conditions to prevent any racemisation. This was achieved using an immobilised form of the Candida antarctica B lipase in water at 30 °C. The biotransformation was demonstrated to be a robust, reliable, and an economic way to introduce the chirality into the Lotrafiban molecule.

In this article we report on the application of in situ product removal (ISPR) (the concurrent recovery of a product during the product formation process) as a means of improving the productivity of bioconversions. The Escherichia coli transketolase-catalyzed condensation of glycolaldehyde with beta-hydroxypyruvate to yield L-erythrulose (and carbon dioxide) was chosen as a model system. Those ISPR methods based on phenylboronate-diol interactions showed greatest potential for use as a selective means of removing L-erythrulose from the reaction medium. Soluble, insoluble, and immobilized boronates were investigated. Concentrations of free phenylboric acid of 100 mM and above were toxic to transketolase, thus rendering the use of these methods unsuitable for ISPR. However, one of the immobilized phenylboronate resins (Affi-Gel 601) was not toxic to the enzyme, although significant levels of nonspecific binding of both substrates were observed. When ISPR was performed on the model reaction using this resin with substrate feeding, it proceeded to completion.

A range of substituted dinitroaromatic compounds have been reduced using baker's yeast (Saccharamyces cerevisiae), in some cases with very high selectivity. A model is presented to account for the origin of the selectivity together with a possible mechanism for the reduction.

A range of substituted dinitroaromatic compounds have been reduced using baker's yeast (Saccharamyces cerevisiae), in some cases with very high selectivity. A model is presented to account for the origin of the selectivity together with a possible mechanism for the reduction.

It would be impossible within a review of this size to cover in depth all of the numerous facets of immobilized biocatalyst technology. Indeed, whole books are devoted to specific topics such as the analytical uses of immobilized enzymes (Guilbault, 1984) or the principles and applications of immobilized cells (Tampion & Tampion, 1987). It is the intention of this review to try and indicate the breadth of topics within the umbrella of immobilized biocatalyst technology and to provide references allowing anyone interested to research a particular area further.