Graphene oxide‐based nanomaterials are promising for enzyme immobilization due to the possibilities of functionalizing surface. Polyethylenimine‐grafted graphene oxide was constructed as a novel scaffold for immobilization of formate dehydrogenase. Compared with free formate dehydrogenase and graphene oxide adsorbed formate dehydrogenase, thermostability, storage stability, and reusability of polyethylenimine‐grafted graphene oxide‐formate dehydrogenase were enhanced. Typically, polyethylenimine‐grafted graphene oxide‐formate dehydrogenase remained 47.4% activity after eight times’ repeat reaction. The immobilized capacity of the polyethylenimine‐grafted graphene oxide was 2.4‐folds of that of graphene oxide. Morphological and functional analysis of polyethylenimine‐grafted graphene oxide‐formate dehydrogenase was performed and the assembling mechanism based on multi‐level interactions was studied. Consequently, this practical and facile strategy will likely find applications in biosynthesis, biosensing, and biomedical engineering.

BACKGROUND Dehydrogenases dependent on NAD(P)H are widely applied for biosynthesis of chiral chemicals. However, they are unstable and easy denaturated compared with hydrolases. A new strategy for dehydrogenases immobilization with the advantages of easy operation and high activity recovery should be developed. Biocompatible hybrid materials (GO‐PEI‐M) have been obtained by metal ions coordinated polyethylenimine (PEI) functionalized graphene oxide (GO). RESULTS The immobilized enzyme recovery rates of GO‐PEI‐Mg (magnesium ion coordinated GO‐PEI) and GO‐PEI‐Mn (manganese ion coordinated GO‐PEI). In addition, the stability of GO‐PEI‐Mn‐PheDH (Phenylalanine Dehydrogenase) and GO‐PEI‐Mg‐PheDH was greatly improved, and it maintained 65% and 79% activity, respectively, after seven times reuse. In addition, the stability of GO‐PEI‐Mn‐PheDH (Phenylalanine Dehydrogenase) and GO‐PEI‐Mg‐PheDH was greatly improved. After seven times reuse, GO‐PEI‐Mn‐PheDH and GO‐PEI‐Mn‐PheDH and maintained 65% and 79% activity, respectively. An assembly mechanism was proposed from the perspectives of multi‐level interactions, including hydrogen bonding, electrostatic forces, and coordinated bonds. CONCLUSION GO‐PEI‐Metal ion hybrid materials offer a promising carrier for enzyme immobilization with the advantages of biocompatibility and relatively strong interaction. © 2020 Society of Chemical Industry

Chiral amines are key building blocks for pharmaceuticals. Economic assessment of commercial potential of bioprocesses is needed for guiding research. Biosynthesis of (S)-α-methylbenzylamine (MBA) was selected as case study. For transamination route, transaminase coupled with glucose dehydrogenase and lactate dehydrogenase catalyzed the reaction with NADH (Nicotinamide adenine dinucleotide) regeneration. Amine dehydrogenase coupled with NADH oxidase, which catalyzed the reductive amination process. Comparison of biosynthesis cost by reductive amination and transamination routes was carried out. Economic assessment based on the framework of cost analysis and preliminary process information revealed that cost is greatly dependent on enzyme price. The results indicated that enhancing the activity of amine dehydrogenase by 4–5 folds can drop the unit price of reductive amination to $0.5–0.6/g, which make it competitive with transamination route.

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