Aldolase catalyzed L-phenylserine synthesis in a slug-flow microfluidic system – Performance and diastereoselectivity studies

Abstract

L-phenylserine was produced by threonine aldolase in slug-flow microfluidic system. Substrate benzaldehyde was continuously supplied from the organic phase. TBME solvent provides mild conditions and high product concentration. MeTHF solvent provides high concentration of L-syn-phenylserine. Toluene provides low value of syn-anti forms ratio in short residence time. a b s t r a c tWe study synthesis of L-phenylserine catalyzed by the enzyme L-threonine aldolase in a slug-flow microfluidic system. Slug-flow arrangement allows for the continuous refilling of sparingly soluble substrate (benzaldehyde) into an aqueous reaction mixture. We identified suitable composition of an organic phase to provide stable slug-flow in a wide range of operational parameters. Solvent screening revealed that tert-butyl methyl ether (TBME) as the organic solvent provides the most friendly environment for L-phenylserine synthesis due to a low degree of enzyme deactivation and high benzaldehyde concentration in the reaction mixture. The effects of substrate concentrations, enzyme concentration, and dimethylsulfoxide (DMSO) concentration on the L-phenylserine concentration in the product stream were examined and proper reaction conditions were identified. Experimental results on the L-phenylserine diastereoselectivity demonstrate that the amount of syn-conformation of L-phenylserine increases with the reaction time. High syn-to anti-concentration ratio is achieved with 2-methyltetrahydrofuran (MeTHF) solvent in a system with long residence time and, finally, low syn-to anticoncentration ratio is provided by toluene environment and short residence time. (J. Čech), v.hessel@tue.nl (V. Hessel), pribylm@vscht.cz (M. Přibyl). Please cite this article as: Čech, J., et al., Aldolase catalyzed L-phenylserine synthesis in a slug-flow microfluidic system -Performance and diastereoselectivity studies. Chem. Eng. Sci. (2016), http://dx.

Continuous Biocatalysis in Environmentally‐Friendly Media: A Triple Synergy for Future Sustainable Processes

“…Another recent example is the synthesis of L‐phenyl‐serine from benzaldehyde and glycine catalyzed by L‐threonine aldolase (L‐TA) in a slug flow microreactor . Since benzaldehyde is poorly soluble in water, the presence of a solvent is required.…”

Application of Threonine Aldolases for the Asymmetric Synthesis of α‐Quaternary α‐Amino Acids

“…At increasing aldehyde concentration, some inactivation of the enzymes was observed, and thus continuous feeding of the acceptor substrate turned out to be advantageous. Alternatively, for tackling substrate inhibition in threonine aldolase catalyzed reactions, slug‐flow microfluidic system could be used . In general, diastereomeric mixtures of amino acid products with moderate excess of the syn ‐isomers were isolated from l ‐TA‐catalyzed reactions.…”

Microreaction and membrane technologies for continuous single-enantiomer production: A review

“…Asymmetric synthesis of value-added chemicals is the main task of catalysis as emphasized in recent reviews. [35,36] Continuous-flow microreactors are used in the organic, [15, enzyme, [16][17][18][19][20][64][65][66][67][68][69][70][71][72][73][74][75][76] or electrochemical [68,77] asymmetric synthesis of various enantiomers or diastereoisomers for various reasons. They have, however, one common characteristic, i.e., a microfluidic platform, which provides scientists with one or more significant advantages over classic laboratory or industrial equipment.…”

“…The most straightforward options are microcapillaries with internal diameters ranging from hundreds of microns to millimeters connected by commercially available PEEK (polyether ether ketone) or steel connectors, among other materials, [17][18][19]38,39,41,[47][48][49][51][52][53][57][58][59][60]66,69] as shown in Figure 1(a). Fluoropolymers, such as PTFE (polytetrafluoroethylene), [18,38,39,49,53,58,66] perfluoroalkoxy polymer, [52] and fluorinated ethylene-propylene, [17] remain the most popular microcapillary materials for their excellent chemical resistance and relatively high melting points. Borosilicate glass [48,69] and fused silica capillaries [19,47,51] are transparent and chemically and thermally resistant.…”