Enzymatic Bioreactors: An Electrochemical Perspective

Abstract

Biocatalysts provide a number of advantages such as high selectivity, the ability to operate under mild reaction conditions and availability from renewable resources that are of interest in the development of bioreactors for applications in the pharmaceutical and other sectors. The use of oxidoreductases in biocatalytic reactors is primarily focused on the use of NAD(P)-dependent enzymes, with the recycling of the cofactor occurring via an additional enzymatic system. The use of electrochemically based systems has been limited. This review focuses on the development of electrochemically based biocatalytic reactors. The mechanisms of mediated and direct electron transfer together with methods of immobilising enzymes are briefly reviewed. The use of electrochemically based batch and flow reactors is reviewed in detail with a focus on recent developments in the use of high surface area electrodes, enzyme engineering and enzyme cascades. A future perspective on electrochemically based bioreactors is presented.

Organic Electrosynthesis Towards Sustainability: Fundamentals and Greener Methodologies

“…Furthermore, the implementation of flow cells based on electrolyte solution recirculation represents a very attractive alternative for scale‐up processes that allows automated electrochemical syntheses and permits the integration of electrode reactions with other synthetic or purification steps in a continuous stream [135] . Electrochemical enzymatic bioreactors, based on biocatalysts, can also provide a large number of advantages such as high selectivity, ability to operate under mild reaction conditions or availability from renewable resources [136] …”

Multi-Enzyme Systems in Flow Chemistry

“…Even for capillary-sized vessels, the surface area to volume ratio is smaller than for other microreactors; hence enzyme loading is poorer with a negative impact on the reaction efficiency. Several strategies have been suggested to improve enzyme loading, mostly involving the deposition of nanomaterials on the inner cell wall of the reactor, as recently reviewed [19]. An inner diameter of capillary as small as possible is also advised to minimize diffusion path [18,19].…”

“…Several strategies have been suggested to improve enzyme loading, mostly involving the deposition of nanomaterials on the inner cell wall of the reactor, as recently reviewed [19]. An inner diameter of capillary as small as possible is also advised to minimize diffusion path [18,19]. Wall-coated reactors were used in cascade reactions, such as the two-step conversion of bis(p-nitrophenol)phosphate monosodium salt into p-nitrophenoxide and inorganic phosphate [20,21], and three-step production of resorufin from lactose [21].…”

“…The high surface area to volume ratio also results in shorter diffusion paths when compared with coated-wall reactors. Still, relatively high backpressure is required to achieve the in-tended flow rate [14,19]. The production of (1S,2S)-1-phenylpropane-1,2-diol through an enzymatic cascade involving fusion enzymes benzoylformate decarboxylase and alcohol dehydrogenase separately immobilize on HaloLink TM resin.…”

“…Moreover, the synthesis of monoliths is performed within the channel, thus packing procedures are avoided, although the preparation can be time-consuming and reproducibility is questionable. Monoliths can be silica-or polymeric-based; the former endure organic solvents, but are sensitive to extreme pH whereas the later are not affected by pH, but their pore structure may be affected by organic solvents [14,18,19]. Invertase, glucose oxidase and horseradish peroxidase were immobilized in a polymeric monolith to produce resorufin from sucrose.…”