Chiral Polyol Synthesis Catalyzed by a Thermostable Transketolase Immobilized on Layered Double Hydroxides in Ionic liquids

Abstract

In this work we set out to study the activity of a thermostable Transketolase (TK) from Geobacillus stearothermophilus (TKgst) in an ionic liquid as cosolvent, which has never been investigated before with this enzyme. 1‐Butyl‐3‐methylimidazolium chloride ([BMIm][Cl]) in the range 30–50 % in water maintained the total activity of TKgst and increased the reaction rate in the presence of pentoses as acceptor substrates, particularly d‐ribose. To improve the synthetic process, TKgst was immobilized on an inorganic support, layered double hydroxides (LDHs), with excellent immobilization yield and catalytic activity using a simple, eco‐compatible, efficient coprecipitation procedure. The biohybrid MgAl@TKgst was tested in 30 % [BMIm][Cl] for the synthesis of a rare, very costly commercially available sugar, d‐sedoheptulose, which was obtained in one step from d‐ribose with an isolated yield of 82 %. This biohybrid was reusable over four cycles with no loss of enzymatic activity. The particular activity of free and immobilized TKgst in [BMIm][Cl] holds promise to extend the applications of TKgst in other ionic liquids and unusual media in biocatalysis.

Convergent in situ Generation of Both Transketolase Substrates via Transaminase and Aldolase Reactions for Sequential One‐Pot, Three‐Step Cascade Synthesis of Ketoses

“…The absolute configurations of 4 – 6 were further confirmed by comparing their optical rotations with those reported in the literature. These characterization data confirmed that the three TK gst ‐catalyzed reactions each led to a single ketose with the expected l ‐ erythro (3 S ,4 S ) configuration, consistent with the stereoselectivity observed with other aldehyde acceptors by TK gst catalysis at elevated temperatures …”

Chemoenzymatic Access to Chiral Tetrols Produced by Thiamine Diphosphate Dependent Benzaldehyde Lyase

“…BAL is able to produce highly enantioenriched 2‐hydroxy ketones in high chemical yield, however mostly of lipophilic character , . We envisaged the synthesis of polyols, usually a domain of aldolases and transketolases, by employing BAL in carboligase reactions. Accordingly, we reasoned that 2,2‐dimethyl‐1,3‐dioxolane‐4‐carbaldehyde (glyceraldehyde acetonide, 3 ) should be suitable for an enzyme‐catalyzed access to tetrols.…”

Droplet millifluidics for kinetic study of transketolase

“…1). The millifluidic technology applied to TK-catalysed carbon-carbon bond formation reactions is of fundamental utility [13][14][15] in optimizing the reaction conditions. Several assay formats have been developed to probe the substrate tolerance of TK by measuring the remaining substrate or product formed.…”

“…We showed that TK gst activity was stable for 16 h in the aqueous solution containing 30%-50% [BMIm][Cl] enhancing TK gst activity towards pentoses, particularly D-ribose. 13 …”