Graphene Oxide Co-deposition on Polymer Membrane for Reactive Separation in Enzyme Membrane Reactor

Abstract

Combination of enzymatic catalysis and membrane technology is advantageous in biotechnology processes. To this regard, a simple technique to immobilize the enzyme in the membrane support via reverse filtration will be applied. Alcohol dehydrogenase (ADH) (EC 1.1.1.1) was chosen as the enzyme to be immobilized on the commercial ultrafiltration membrane in this study. ADH catalyzed formaldehyde (CHOH) to methanol (CH3OH) and simultaneously oxidized nicotinamide adenine dinucleotide (NADH) to NAD+. An integrated, hydrophilic graphene oxide-based polymer membrane was used as a support to immobilize the enzyme. The objective of the study is to assess the performance of the biocatalytic membrane reactor when graphene oxide (GO) nanoparticles is co-deposited together with ADH enzyme within the polyethersulfone (PES) membrane in terms of its membrane permeability, hydrophilicity, enzyme loading, reaction conversion and biocatalytic productivity. The results showed that the membrane permeability increased with the addition of GO which indicating improved membrane hydrophilicity. Enzyme loading is highest for PES/GO 0.1 membrane at 79 %. The reaction conversion for all the membranes recorded between 60 % to 84 %, however the PES/GO membranes showed to be higher than the pristine membrane. The enrichment of GO improved the activity of ADH in 5 cycles. The cumulative biocatalytic productivity of PES/GO membranes in 5 consecutive cycles were higher with 455.4 µmol CH3OH/mgADH·h and 390.5 µmol CH3OH/mgADH·h respectively in comparison to only 359.5 µmol CH3OH/mgADH·h for pristine membrane. The synergy between enzyme catalysis and membrane filtration is beneficial because it allows for both enzyme immobilization and simultaneous product separation.