Electric‐field‐enhanced selective separation of products of an enzymatic reaction in a membrane micro‐contactor

Abstract

Processes employed in separations of products of enzyme reactions are often driven by diffusion, and their efficiency can be limited. Here, we exploit the effect of a direct current (DC) electric field that intensifies mass transfer through a semipermeable membrane for fast, continuous, and selective separation of electrically charged molecules. Specifically, we separate low‐molecular‐weight reaction products (phenylacetic acid, 6‐aminopenicillanic acid) from the original reaction mixture containing a free enzyme (penicillin acylase). The developed microfluidic dialysis‐membrane contactor allows a stable counter‐current arrangement of the retentate and permeates liquid streams on which DC electric field is perpendicularly applied. The applied electric field significantly accelerates the transport of electrically charged products through the semipermeable membrane yielding high separation efficiencies at short residence times. The residence time of 5 min is sufficient to reach 100% separation yield in the electric field. The same residence time provides only a 50% yield in the diffusion‐controlled experiments. We experimentally demonstrated that a combined microreactor–microextractor with a recycle of the soluble penicillin acylase can continuously produce both the reaction products at high concentrations. The developed membrane‐contactor is a versatile platform allowing to tune its characteristics, such as selectivity given by the membrane, or the type of the retentate phase, for a specific application.

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

“…The highmolecular-weight catalysts or enzymes remain in the retentate, as shown in Figure 5(a). Such systems operate either in ultrafiltration [73] or electrodialysis mode, [79] and a valuable catalyst can also be reused. [80] Such a modular system has been reported by O'Sullivan et al [73] describing a microreactor using free enzyme transketolase as a homogeneous catalyst for the chiral synthesis of L-erythrulose and (3S)-1,3-dihydroxypentan-2-one.…”

“…However, a thin separation membrane with low transport resistance can stabilize a counter-current flow. [79] As such, this is a powerful arrangement for the synthesis of enantiomers because a chiral catalyst can be immobilized directly in the membrane, or the membrane can serve as a chiral sieve.…”

Bioprocess intensification: A route to efficient and sustainable biocatalytic transformations for the future

“…In a recent study, a microextractor driven by electric field has been described for intensified separation of electrically charge product molecules from an enzyme across a membrane, giving fast, continuous, and selective separation of electrically charged molecules [211]. Separation efficiency is doubled from 50% to 100% at short residence time under the electric field, allowing recovery and re-use of enzyme.…”

Let the Biocatalyst Flow

“…75 thus phase separation problems, this obstacle is reduced in microflow reactors. 39,78 Applications of slug flow include various reactions and enzymes, from reactions catalyzed by alcohol-dehydrogenase (ADH), [79][80][81][82] to hydroxynitrile lyase-catalyzed C-C bond formation, 83 a reduction with pentaerythritol tetranitrate reductase, 84 terpene production catalyzed by aristolochene synthase, 77 penicillin acylase-catalyzed antibiotic synthesis, 75,85,86 and lipase-assisted biodiesel production, 87,88 among others.…”

“…Furthermore, the electroosmotic flow through the membrane, which counter-directs the transport of phenylacetic acid, was advantageously used to concentrate the separated product in the acceptor phase. 86 The importance of minimizing stable emulsion formation, typical of the stirred tank batch processing, was highlighted for the enzymatic reduction of hydrophobic ketone in a biphasic methyl tert-butyl ether (MTBE)buffer carried out in a segmented flow formed in a Y-shaped mixer and guided in a poly(fluorenylene ethynylene) (PFE) coil of 0.8 mm diameter, and compared with the batch process. While the conversions in both process operations were similar under comparable conditions, emulsification and precipitation were strongly suppressed when the biocatalytic reactions were carried out in flow mode, significantly simplifying and minimizing the effort required for biphasic biocatalytic reaction systems.…”