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

BACKGROUND:The metal-organic framework (MOF) ZIF-8 has the advantages of a large specific surface area and high stability. A new strategy for the assembly of amino acid dehydrogenase with peptide linker and for improving enzyme immobilization is proposed.RESULTS: Peptide linker enhanced enzyme activity after immobilization by 138.7%, and maintained 81.2% of its initial activity after seven recycles. The stability of PheDH_1D02/ZIF-8 was greatly enhanced at 70-80 °C and pH 10-11. The catalytic efficiency of PheDH_1D02/ZIF-8 was also enhanced compared with PheDH_1C1D/ZIF-8 and two free enzymes.CONCLUSIONS: Metal ions coordinated with the peptide linker and reoriented immobilization of enzyme onto the MOF with high enzyme loading capacity were achieved. The mesoporous structure of PheDH_1D02/ZIF-8 facilitates substrate diffusion. Combining the assembly of peptide linker and MOF immobilization is a simple, economical and efficient method for improving dehydrogenase stability.

Exploring bioelectroanalysis and bioelectrocatalysis in non-aqueous systems are essential for bridging the gap between laboratorial and industrial scale. Bioelectrodes based on carbon nanomaterials, such as carbon nanotubes and graphene, have been designed and fabricated with biocompatible surface functionalities. This review presents recent advances in regulation of a biocompatible microenvironment of enzyme electrodes in non-aqueous systems. We summarize the modification strategies to facilitate electron transfer and promote enrichment of hydrophobic analytes. We focus on the mining and modification for robust oxidoreductases from extremophiles to explore the biosensors in extreme conditions. Challenges and future prospects for bioelectrodes in non-aqueous systems are discussed.

Organic solvent tolerant oxidoreductases are significant for both scientific research and biomanufacturing. However, it is really challenging to obtain oxidoreductases due to the shortages of natural resources and the difficulty to obtained it via protein modification. This review summarizes the recent advances in gene mining and structure-functional study of oxidoreductases from extremophiles for non-aqueous reaction systems. First, new strategies combining genome mining with bioinformatics provide new insights to the discovery and identification of novel extreme oxidoreductases. Second, analysis from the perspectives of amino acid interaction networks explain the organic solvent tolerant mechanism, which regulate the discrete structure-functional properties of extreme oxidoreductases. Third, further study by conservation and co-evolution analysis of extreme oxidoreductases provides new perspectives and strategies for designing robust enzymes for an organic media reaction system. Furthermore, the challenges and opportunities in designing biocatalysis non-aqueous systems are highlighted.

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