Selective Reduction of Esters to Access Aldehydes Using Fiddler Crab-Type Boranes.

The partial reduction of esters to aldehydes is a fundamentally important transformation for the synthesis of numerous fine chemicals and consumer goods. However, despite the many efforts, limitations have persisted, such as competing overreduction, low reproducibility, use of exigent reaction conditions and hazardous chemicals. Here, we report a novel catalyst family with a unique steric design which promotes the catalytic partial reduction of esters with unprecedented, near-perfect selectivity and efficiency.

Production of ω-hydroxy octanoic acid with Escherichia coli.

The present proof-of-concept study reports the construction of a whole-cell biocatalyst for the de novo production of ω-hydroxy octanoic acid. This was achieved by hijacking the natural fatty acid cycle and subsequent hydroxylation using a specific monooxygenase without the need for the additional feed of alkene-like precursors. For this, we used the model organism Escherichia coli and increased primarily the release of the octanoic acid precursors by overexpressing the plant thioesterase FatB2 from Cuphea hookeriana in a β-oxidation deficient strain, which lead to the production of 2.

Whole-cell microtiter plate screening assay for terminal hydroxylation of fatty acids by P450s.

A readily available galactose oxidase (GOase) variant was used to develop a whole cell screening assay. This endpoint detection system was applied in a proof-of-concept approach by screening a focussed mutant library. This led to the discovery of the thus far most active P450 Marinobacter aquaeolei mutant catalysing the terminal hydroxylation of fatty acids.

Enzyme engineering in the context of novel pathways and products.

In recent years, enzyme engineering was used to fine-tune a diverse set of proteins to realize new biosynthetic pathways and gain access to novel products. However, enzymes in nature do not always meet the required demands in terms of activity, selectivity and stability. In these cases enzyme engineering has been used to improve the enzyme properties, which facilitated the development of tailor-made functional biocatalysts, even beyond their natural capabilities.

Synthesis of 9-oxononanoic acid, a precursor for biopolymers.

Polymers based on renewable resources have become increasingly important. The natural functionalization of fats and oils enables an easy access to interesting monomeric building blocks, which in turn transform the derivative biopolymers into high-performance materials. Unfortunately, interesting building blocks of medium-chain length are difficult to obtain by traditional chemical means.