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.

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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.

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.