An Integrated Cofactor/Co‐Product Recycling Cascade for the Biosynthesis of Nylon Monomers from Cycloalkylamines

Concept of an Enzymatic Reactive Extraction Centrifuge

Biocatalytic processes often provide an ecological alternative to many chemical processes. However, further improvements in terms of the economic efficiency are required. In order to achieve that, the concept of process integration is a promising option. Applying this within a biocatalytic process, a highly integrated apparatus working as a reactive extraction centrifuge was developed and operated. For this purpose, a commercially available extraction centrifuge was modified to implement a biocatalytic reaction. The novel apparatus was used within a multi-enzyme cascade for the production of a natural flavor and fragrance, namely cinnamic ester. The characterization of the reactive extraction centrifuge and the suitable operation conditions for the inlet streams and the rotational speed for a stable operation were determined. Furthermore, different initial substrate concentrations were applied to prove the reaction. The results provide a successful proof of concept for the novel reactive extraction centrifuge.

Asymmetric Synthesis of N-Substituted 1,2-Amino Alcohols from Simple Aldehydes and Amines by One-Pot Sequential Enzymatic Hydroxymethylation and Asymmetric Reductive Amination

The chiral N-substituted 1,2-amino alcohol motif is found in many natural and synthetic bioactive compounds. In this study, enzymatic asymmetric reductive amination of α-hydroxymethyl ketones with enantiocomplementary imine reductases (IREDs) enabled the synthesis of chiral N-substituted 1,2-amino alcohols with excellent ee values (91-99 %) in moderate to high yields (41-84 %). Furthermore, a one-pot, two-step enzymatic process involving benzaldehyde lyase-catalyzed hydroxymethylation of aldehydes and subsequent asymmetric reductive amination was developed, offering an environmentally friendly and economical way to produce N-substituted 1,2-amino alcohols from readily available simple aldehydes and amines. This methodology was then applied to rapidly access a key synthetic intermediate of anti-malaria and cytotoxic tetrahydroquinoline alkaloids.

Promoter engineering-mediated Tuning of esterase and transaminase expression for the chemoenzymatic synthesis of sitagliptin phosphate at the kilogram-scale

Here, we report a bienzymatic cascade to produce β-amino acids as an intermediate for the synthesis of the leading oral antidiabetic drug, sitagliptin. A whole-cell biotransformation using recombinant Escherichia coli coexpressing a esterase and transaminase were developed, wherein the desired expression level of each enzyme was achieved by promotor engineering. The small-scale reactions (30 ml) performed under optimized conditions at varying amounts of substrate (100-300 mM) resulted in excellent conversions of 82%-95% for the desired product. Finally, a kilogram-scale enzymatic reaction (250 mM substrate, 220 L) was carried out to produce β-amino acid (229 mM). Sitagliptin phosphate was chemically synthesized from β-amino acids with 82% yield and > 99% purity.