Crystallization-based downstream processing of ω-transaminase- and amine dehydrogenase-catalyzed reactions

Biocatalytic synthesis is a powerful and frequently chosen method for the production of chiral amines. Unfortunately, these biocatalytic reactions often result in complex mixtures, bearing many components aside from the main product amine such as residual co-substrates, co-products, cofactors and buffer salts. This issue typically requires an additional effort during downstream processing towards the isolation of the desired chiral amine. For instance, transaminase- and amine dehydrogenase-catalyzed reactions, which often use high surpluses of amine or ammonia co-substrates, face complications in removing the residual amine donor or unreacted substrate and salts from the isolated amine products, thus complicating and increasing the costs of the process of product isolation and purification. This study explores the selective removal of chiral amines from model amine transaminase and amine dehydrogenase-catalyzed reactions via a salt-based specific crystallization step. The product amine is precipitated directly in one step from the reaction mixture as a product ammonium salt, which can easily be filtered from the reaction mixture, while the other reactants remain unchanged in solution for potential re-use.</p

How to overcome limitations in biotechnological processes - examples from hydroxynitrile lyase applications

During the last decades, enzymes became very versatile catalysts for a variety of reactions including natural and unnatural compounds. However, many enzyme-catalysed reactions suffer from diverse restrictions because of limitations related to process parameters or the enzyme. The understanding and overcoming of those undesired side effects is therefore mandatory for the implementation of optimal process parameters. To achieve this aim, various methods from molecular biology and reaction engineering can be employed. By focusing on the hydroxynitrile lyase-catalysed synthesis of enantiopure cyanohydrins, we give an overview of strategies to improve commercially utilized enzymes and to suppress non-enzymatic reactions. Particular emphasis is placed on the necessity to combine approaches from different fields, such as enzyme engineering and reaction engineering. Copyright © 2009 Elsevier Ltd All rights reserved. [accessed September 17, 2009