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.

The colonization characteristics of bacterial communities on microplastics or plastic debris (PD) have generated great concern in recent years. However, the influence of environmental factors and polymer types on the formation of bacterial communities on PD in estuarine areas is less studied. To gain additional insights, five types of PD (polyvinyl chloride, polypropylene, polyethylene, polystyrene, and polyurethane) were exposed for three-time periods (two weeks, four weeks, and six weeks) in the Haihe Estuary. 16S rRNA gene sequencing was used to identify the bacterial communities on PD, in seawater, and in sediment samples. The results indicate that the average growth rate of a biofilm is affected by nutrients (total nitrogen and total phosphorus) and salinity. Furthermore, salinity is the primary factor affecting bacterial diversity of the colonies on PD. In addition, genera of bacteria show selectivity toward the PD polymer type and tend to colonize their preferred substrate. Compared with seawater and sediment, PD could be carriers for enrichment of Vibrio in the estuarine environment with salinity ≥26 (± 2‰), which might increase the ecological risk of PD in marine environments.

Recent progress in nanotechnology has provided high-performance nanomaterials for enzyme immobilization. Nanobiocatalysts combining enzymes and nanocarriers are drawing increasing attention because of their high catalytic performance, enhanced stabilities, improved enzyme-substrate affinities, and reusabilities. Many studies have been performed to investigate the efficient use of cellulose nanocrystals, polydopamine-based nanomaterials, and synthetic polymer nanogels for enzyme immobilization. Various nanobiocatalysts are highlighted in this review, with the emphasis on the design, preparation, properties, and potential applications of nanoscale enzyme carriers and nanobiocatalysts.

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