The nano-/microscale UiO-66-NH2 metal–organic framework (MOF) materials were successfully prepared with a uniform size of about 350–400 nm and structurally characterized. Soybean epoxide hydrolase (SEH), a useful hydrolase for synthesis of valuable vicinal diols, was for the first time efficiently immobilized onto the prepared UiO-66-NH2 MOF. The resulting novel nano-/microbiocatalyst SEH@UiO-66-NH2 manifested high SEH loading (87.3 mg/g) and enzyme activity recovery (88.0%). The novel SEH@UiO-66-NH2 greatly surpassed the free SEH with resepct to pH stability, thermostability, and tolerance to organic solvents. SEH@UiO-66-NH2 retained more than 17.6 U activity after 2 h of incubation at 45 °C, whereas free SEH maintained around 10.1 U activity under the same conditions. After storage at 4 °C for 4 weeks, the prepared SEH@UiO-66-NH2 still retained around 97.5% of its initial activity. The significant enhancements resulted from the increase of structural rigidity of SEH@UiO-66-NH2, which was demonstrated by the secondary structure analysis of the enzyme. The optimun pH and tempearture of SEH@UiO-66-NH2 were significantly superior to the corresponding levels of its free counterpart. Also, SEH@UiO-66-NH2 manifested markedly enhanced enzyme–substrate affinity and catalytic efficiency compared to free SEH, as supported by a lower apparent Km value (6.5 vs 19.2 mM) and an increased V max/K m value (8.0 × 10–3 vs 5.8 × 10–3 min–1), respectively. Furthermore, the as-prepared SEH@UiO-66-NH2, for the first time, was successfully applied as an efficient biocatalyst for the asymmetric hydrolysis of 1,2-epoxyoctane to (R)-1,2-octanediol in a novel deep eutectic solvent (DES) with a yield of around 41.4% and a product e.e. value of 81.2%. Remarkably, the nano-/microscale UiO-66-NH2 MOFs as novel enzyme support materials are promising for enzyme immobilization, and the prepared SEH@UiO-66-NH2 exhibited great potential for efficient biosynthesis of enantipure (R)-1,2-octanediol.

Magnetic nanocrystalline cellulose (MNCC), a novel bio-based nanocomposite, was prepared via a simple co-precipitation-cross-linking technique and structurally characterized. Papain (PA) was successfully immobilized onto the MNCC. The resulting nano-biocatalyst PA@MNCC showed high PA loading (333 mg/g) and enzyme activity recovery (more than 80%). The stabilities of PA@MNCC was greatly superior to that of its free counterpart. Also, PA@MNCC manifested markedly enhanced solvent tolerance. The secondary structure study of the enzyme proved that these enhancements were attributed to the increase of structure rigidity of PA@MNCC. The observed optimum pH and temperature of PA@MNCC were significantly higher than the corresponding levels of free PA. A kinetic study demonstrated that PA@MNCC had a increase in enzyme-substrate affinity.Furthermore, the as-prepared PA@MNCC was successfully used as an efficient biocatalyst for the synthesis of N-(benzyloxycarbonyl)-alanyl-glutamine (Z-Ala-Gln) dipeptide in deep eutectic solvent (DES), choline chloride (ChCl):Urea(1:2), with a high yield (about 71.5%), which, to our knowledge, was greatly higher than that reported previously. Besides, the novel PA@MNCC was easily recycled from the reaction medium by magnetic forces. Obviously, MNCC is a promising and competitive enzyme carrier and the as-prepared nano-biocatalyst PA@MNCC exhibited great potential for efficient biosynthesis of dipeptide.

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Magnetic cellulose nanocrystals (MCNCs) were prepared and used as an enzyme support for immobilization of Pseudomonas cepacialipase (PCL). PCL was successfully immobilized onto MCNCs (PCL@MCNC) by a precipitation-cross-linking method. The resulting PCL@MCNC with a nanoscale size had high enzyme loading (82.2 mg enzyme/g) and activity recovery (95.9%). Compared with free PCL, PCL@MCNC exhibited significantly enhanced stability and solvent tolerance, due to the increase of enzyme structure rigidity. The observable optimum pH and temperature for PCL@MCNC were higher than those of free PCL. PCL@MCNC manifested relatively higher enzyme-substrate affinity and catalytic efficiency. Moreover, PCL@MCNC was capable of effectively catalyzing asymmetric hydrolysis of ketoprofenethyl ester with high yield of 43.4% and product e.e. of 83.5%. Besides, immobilization allowed PCL@MCNC reuse for at least 6 consecutive cycles retaining over 66% of its initial activity. PCL@MCNC was readily recycled by magnetic forces. Remarkably, the as-prepared nanobiocatalyst PCL@MCNC is promising for biocatalysis.

Preparation of a novel magnetic cellulose nanocrystal via a simple co-precipitation-electrostatic-self-assembly technique and its efficient use for enzyme immobilization.