Reactive extraction of N-acetylneuraminic acid—Kinetic model and simulation of integrated product removal

Abstract

The reactive extraction of N-acetylneuraminic acid with phenylboronic acid (PBA) and trioctylmethylammoniumchloride (TOMAC) is a new method to recover neuraminic acid from reaction solutions. We describe a kinetic model which is suitable to describe the extraction of pure compounds as well as mixtures of the reactants, which are N-acetyl- d-glucosamine (GlcNAc), N-acetyl- d-mannosamine (ManNAc), sodium pyruvate (Pyr) and neuraminic acid (Neu5Ac). For the extraction a two-step mechanism is assumed and the ion exchange at the interface was determined to be the rate-limiting step. Kinetic measurements were performed in a Lewis-type cell. The first reaction step is included in the model by a parameter σ which describes the extractable amount of carbohydrate. The extraction model is combined with a model describing the enzymatic synthesis of Neu5Ac from GlcNAc to simulate the integration of reaction and extraction. The integrated process was simulated with varying substrate concentrations, carrier concentrations, phase ratios and interfacial area. A batch reaction with concurrent extraction and continuous renewal of the organic phase was developed. Under optimised conditions neuraminic acid is produced with the same space–time yield as without extraction and the product is accumulated in the organic phase, which facilitates further downstream processing. The developed model is feasible to analyse and evaluate integrated product removal as well as separately operated reaction and extraction.