2-amino-1-3-4-butanetriol and erythrulose

This work aims to establish microscale methods to rapidly explore bioprocess options that might be used to enhance bioconversion reaction yields: either by shifting unfavourable reaction equilibria or by overcoming substrate and/or product inhibition. As a typical and industrially relevant example of the problems faced we have examined the asymmetric synthesis of (2S,3R)-2-amino-1,3,4-butanetriol from l-erythrulose using the ω-transaminase from Chromobacterium violaceum DSM30191 (CV2025 ω-TAm) and methylbenzylamine as the amino donor. The first process option involves the use of alternative amino donors. The second couples the CV2025 ω-TAm with alcohol dehydrogenase and glucose dehydrogenase for removal of the acetophenone (AP) by-product by in situ conversion to (R)-1-phenylethanol. The final approaches involve physical in-situ product removal methods. Reduced pressure conditions, attained using a 96-well vacuum manifold were used to selectively increase evaporation of the volatile AP while polymeric resins were also utilised for selective adsorption of AP from the bioconversion medium. For the particular reaction studied here the most promising bioprocess options were use of an alternative amino donor, such as isopropylamine, which enabled a 2.8-fold increase in reaction yield, or use of a second enzyme system which achieved a 3.3-fold increase in yield.

Topics: Amino Alcohols; Bacterial Proteins; Chromobacterium; Tetroses; Transaminases

Complex molecules are synthesised via a number of multi-step reactions in living cells. In this work, we describe the development of a continuous flow immobilized enzyme microreactor platform for use in evaluation of multi-step bioconversion pathways demonstrating a de novo transketolase/ω-transaminase-linked asymmetric amino alcohol synthesis. The prototype dual microreactor is based on the reversible attachment of His₆-tagged enzymes via Ni-NTA linkage to two surface derivatised capillaries connected in series. Kinetic parameters established for the model transketolase (TK)-catalysed conversion of lithium-hydroxypyruvate (Li-HPA) and glycolaldehyde (GA) to L-erythrulose using a continuous flow system with online monitoring of reaction output was in good agreement with kinetic parameters determined for TK in stop-flow mode. By coupling the transketolase catalysed chiral ketone forming reaction with the biocatalytic addition of an amine to the TK product using a transaminase (ω-TAm) it is possible to generate chiral amino alcohols from achiral starting compounds. We demonstrated this in a two-step configuration, where the TK reaction was followed by the ω-TAm-catalysed amination of L-erythrulose to synthesise 2-amino-1,3,4-butanetriol (ABT). Synthesis of the ABT product via the dual reaction and the on-line monitoring of each component provided a full profile of the de novo two-step bioconversion and demonstrated the utility of this microreactor system to provide in vitro multi-step pathway evaluation.

Topics: Acetaldehyde; Acetophenones; Amino Alcohols; Bioreactors; Enzymes, Immobilized; Histidine; Kinetics; Microfluidic Analytical Techniques; Models, Biological; Oligopeptides; Pyruvates; Recombinant Fusion Proteins; Stereoisomerism; Tetroses; Transaminases; Transketolase