Carbon dioxide/methanol conversion cycle based on cascade enzymatic reactions supported on superparamagnetic nanoparticles

Abstract

The conversion of carbon dioxide into important industrial feedstock is a subject of growing interest in modern society. A possible way to achieve this goal is by carrying out the CO 2 /methanol cascade reaction, allowing the recycle of CO 2 using either chemical catalysts or enzymes. Efficient and selective reactions can be performed by enzymes; however, due to their low stability, immobilization protocols are required to improve their performance. The cascade reaction to reduce carbon dioxide into methanol has been explored by the authors, using, sequentially, alcohol dehydrogenase (ADH), formaldehyde dehydrogenase (FalDH), and formate dehydrogenase (FDH), powered by NAD + /NADH and glutamate dehydrogenase (GDH) as the co-enzyme regenerating system. All the enzymes have been immobilized on functionalized magnetite nanoparticles, and their reactions investigated separately in order to establish the best performance conditions. Although the stepwise scheme led to only 2.3% yield of methanol per NADH; in a batch system under CO 2 pressure, the combination of the four immobilized enzymes increased the methanol yield by 64 fold. The studies indicated a successful regeneration of NADH in situ, envisaging a real possibility of using immobilized enzymes to perform the cascade CO 2 -methanol reaction.

Immobilization of Alcohol Dehydrogenase on Titania Nanoparticles To Enhance Enzyme Stability and Remove Substrate Inhibition in the Reaction of Formaldehyde to Methanol

“…This phenomenon can be interpreted as the result of substrate inhibition which is usually observed at high substrate concentration, whereas at low substrate concentration the reaction’s kinetics follows simple Michaelis–Menten behavior . Formaldehyde is a known enzyme inhibitor, and its accumulation in the system has been shown to be detrimental . On the other hand, formaldehyde has an aldehyde group in its structure that can covalently react with imide group of the enzyme which leads to irreversible inhibition.…”

Artificial Multienzyme Scaffolds: Pursuing in Vitro Substrate Channeling with an Overview of Current Progress

“…Plants and other autotrophic organisms employ enzyme cascades to produce sugars and other metabolic components from CO 2 , but carbohydrates such as glucose are not the only products that can be enzymatically synthesized from this precursor. Using an engineered non-natural enzyme pathway, Marques Netto et al were able to produce methanol from CO 2 using four enzymes immobilized on magnetic NPs; this is the converse of the pathway utilized by Liu et al (Figure A), which also employed most of the same enzymes . The conversion process required four enzymes: alcohol dehydrogenase (ADH) from S.…”

“…What is also not appreciated is that many enzymatic pathways can function in a bidirectional manner, as exemplified by the glycolytic enzymes, which can function catabolically in converting glucose to lactate and also in the reverse direction as part of gluconeogenesis. This could allow systems to work in either direction as needed and as driven thermodynamically in a manner analogous to the CO 2 to methanol and converse examples mentioned above. ,, Attaching the enzymes to magnetically susceptible scaffolds in a manner similar to that of Yang et al , who immobilized glucoamylase and α-amylase on ferric oxide powders in chitosan beads, is also quite intriguing. This approach could potentially allow the enzymes to overcome some diffusion limitations or better exploit channeling phenomena by removing back-inhibiting products in the right configuration.…”

Improving the Enzymatic Cascade of Reactions for the Reduction of CO2 to CH3OH in Water: From Enzymes Immobilization Strategies to Cofactor Regeneration and Cofactor Suppression

“…Faradaic efficiencies of around 10%. No NADH but direct electron transfer [ 51 ] PS nanofibrous membrane F ate DH Free enzymes: [Formate] = 0.6 mM Immobilized enzymes: [Formate] = 0.3 mM (53% initial activity retained after 8 cycles) Electrochemical regeneration [ 34 ] Magnetic NPs F ate DH, F ald DH, ADH Stepwise scheme led to only a 2.3% yield of methanol per NADH; batch system under CO 2 pressure, the combination of the four immobilized enzymes increased the methanol yield by 64-fold [ 52 ] ZIF-8 entrapped in PVDF microporous asymmetric membrane F ate DH, F ald DH, ADH Immobilized enzymes without membrane (EMS) = 5 µmol. Immobilized enzymes with membrane (ECMS) = 6 µmol.…”