A Dynamic Defect Generation Strategy for Efficient Enzyme Immobilization in Robust Metal-Organic Frameworks for Catalytic Hydrolysis and Chiral Resolution.

Enzyme immobilization has been demonstrated to be a favorable protocol for promoting the industrialization of bioactive molecules, but still with formidable challenge. Addressing this challenge, we create a dynamic defect generation strategy for enzyme immobilization by using the dissociation equilibrium of metal-organic frameworks (MOFs) mediated by enzymes. Enzymes can act as "macro ligands" to generate competitive coordination against original ligands, along with the release of metal clusters of MOFs to generate defects, hence promoting the gradual transport of enzymes from the surface to inside. Various enzymes can be efficiently immobilized in MOFs to afford composites with good enzymatic activities, protective performances and exceptional reusabilities. Moreover, multienzyme bioreactors capable of efficient cascade reactions can also be generated. This study provides new opportunities to construct highly efficient biocatalysts incorporating different types of enzymes.

Green and Scalable Fabrication of High-Performance Biocatalysts Using Covalent Organic Frameworks as Enzyme Carriers.

Enzyme immobilization is essential to the commercial viability of various critical large-scale biocatalytic processes. However, challenges remain for the immobilization systems, such as difficulties in loading large enzymes, enzyme leaching, and limitations for large-scale fabrication. Herein, we describe a green and scalable strategy to prepare high-performance biocatalysts through in situ assembly of enzymes with covalent organic frameworks (COFs) under ambient conditions (aqueous solution and room temperature). The obtained biocatalysts have exceptional reusability and stability and serve as efficient biocatalysts for important industrial reactions that cannot be efficiently catalyzed by free enzymes or traditional enzyme immobilization systems. Notably, this versatile enzyme immobilization platform is applicable to various COFs and enzymes. The reactions in an aqueous solution occurred within a short timeframe (ca. 10-30 min) and could be scaled up readily (ca. 2.3 g per reaction).

Investigation of the presence of Ochrobactrum spp. and Brucella spp. in Haemaphysalis longicornis.

Ticks are common vectors of human and animal diseases. Ochrobactrum spp. belong to the Brucellaceae family and have recently been recognized as emerging human pathogens. The ability of Haemaphysalis longicornis ticks to carry Ochrobactrum spp. remains uncertain. During June and July 2018, 686 ticks were collected from 11 sites in Pingdingshan Henan province in central China. We extracted 169 DNA samples for Brucellaceae 16S rRNA nested PCR and sequenced them in order to identify Ochrobactrum spp. The data sequences were aligned with NCBI BLAST program and phylogenetic tree was constructed using Mega 5.0. Twenty samples were sequenced successfully out of a total forty-one positive for Brucellaceae. Thirteen DNA samples were identical to O. intermedium (99.85 %-100.00 %) and 3 were identical to O. cicer (99.85 %-100.00 %) (15 collected from host and one from vegetation). Four DNA samples (3 collected from host and one from vegetation) had 99.83-100 % B. melitensis identity. This study adds to the growing body of evidence that shows Ochrobactrum spp. are present in H. longicornis. Ochrobactrum spp. and Brucella spp. are phenotypically and genetically closely related pathogens. Our finding highlights the importance of gene sequencing and phylogenetic analysis to differentiate between Ochrobactrum spp. and Brucella spp. in the research and potentially clinical setting. Future work is required to investigate the transmission potential of Ochrobactrum spp. by H. longicornis.