Synthesis of a Healthy Sweetener d-Tagatose from Starch Catalyzed by Semiartificial Cell Factories

d-Tagatose is one of the several healthy sweeteners that can be a substitute for sucrose and fructose in our daily life. Whole cell-catalyzed phosphorylation and dephosphorylation previously reported by our group afford a thermodynamic-driven strategy to achieve tagatose production directly from starch with high product yields. Nonetheless, the poor structural stability of cells and difficulty in biocatalyst recycling restrict its practical application. Herein, an efficient and stable semiartificial cell factory (SACF) was developed by constructing an organosilica network (OSN) artificial shell on the cells bearing five thermophilic enzymes to produce tagatose. The OSN artificial shell, the thickness of which can be regulated by changing the tetraethyl silicate concentration, exhibited tunable permeability and superior mechanical strength. In contrast with cells, SACFs showed a relative activity of 99.5% and an extended half-life from 33.3 to 57.8 h. Over 50% of initial activity was retained after 20 reuses. The SACFs can catalyze seven consecutive reactions with tagatose yields of over 40.7% in field applications.

Assessment of Enzyme Functionality at Metal-Organic Framework Interfaces Developed through Molecular Simulations

The catalytic efficiency and unrivaled selectivity with which enzymes convert substrates to products have been tapped for widespread chemical transformations within biomedical technology, biofuel production, gas sensing, and the upgrading of commodity chemicals, just to name a few. However, the feasibility of enzymes implementation is challenged by the lack of reusability and loss of native catalytic activity due to the irreversible biocatalyst denaturation at high temperatures and in the presence of industrial solvents. Enzyme immobilization, a prerequisite for enzyme reusability, offers controllable strategies for increased functional viability of the biocatalyst in a synthetic environment. Herein we used molecular dynamics (MD) simulations and probed the noncovalent interactions between model enzymes of technological interest, i.e., carbonic anhydrase (CA) and myeloperoxidase (MPO), with selected metal-organic frameworks (MOFs; MIL-160 and ZIF-8) of proven industrial implementation. We found that the CA and MPO can bind to MIL-160 at optimal binding energies of 201 and 501 kJ mol^-1, respectively, that are strongly influenced by the increased incidence of hydrogen bonding between enzymes and the frameworks. The free energy of binding of enzymes to ZIF-8, on the other hand, was found to be less strongly influenced by hydrogen bonding networks relative to the occurrence of hydrophobic-hydrophobic interactions that yielded 106 kJ mol^-1 for CA and 201 kJ mol^-1 for MPO.

Efficient resolution of 4-chlormandelic acid enantiomers using lipase@UiO-67(Zr) zirconium-organic frameworks in organic solvent

A new biocatalyst PCL@UiO-67(Zr) was successfully synthesized by immobilized lipases on metal-organic frameworks (MOFs) materials. Compare with free lipases, zirconium foundation organic framework material UiO-67(Zr) modification on immobilized lipases Pseudomonas cepacia lipase (PCL) great boosts their enantioselectivity in the kinetic resolution racemic 4-chloro-mandelic acid (4-ClMA) on the organic solvent. The acquired bio-composite PCL@UiO-67(Zr) was fully characterized by powder X-ray diffraction (PXRD), Fourier transform infrared (FT-IR) spectroscopy, N₂ adsorption-desorption isotherm and aperture distribution map, and scanning electron microscopy (SEM). The catalytic performance of PCL@UiO-67(Zr), such as temperature, reaction time, and lipase quantity, were deeply explored. The experiment results showed resolution racemic 4-ClMA optimum conditions that 20 mmol/L of (R, S)-4-chloromandelic acid, 120 mmol/L vinyl acetate, 30-mg immobilized lipases PCL@UiO-67(Zr), 2 mL of MTBE, 500 rpm, and under the 55°C reaction 18 h. In this optimum conditions, c and ee_p could reach up to 47.6% and 98.7%, respectively.

A novel enhanced enrichment glucose oxidase@ZIF-8 biomimetic strategy with 3-mercaptophenylboronic acid for highly efficient catalysis of glucose

Herein, a glucose oxidase@ZIF-8 composite (3-MPBA/GOx@ZIF-8) with enhanced enrichment was enabled the rapid encapsulation of glucose oxidase (GOx) into microporous zeolitic imidazolate framework-8 (ZIF-8) for the first time. The 3-MPBA/GOx@ZIF-8 not only has improved affinity and catalytic efficiency to the substrate but also can shorten the formation time. The optimum loading amount of GOx on ZIF-8 was determined to be 470 mg/g. The as-prepared 3-MPBA/GOx@ZIF-8 composite maintained the native conformation of the enzyme and showed excellent bioactivity, even in chemical agents or at high temperature. Furthermore, the 3-MPBA/GOx@ZIF-8 showed satisfactory reusability, preserving almost 80.8 % activity after 7 cycles. The Michaelis constant K_m and specificity constant k_cat/K_m of the 3-MPBA/GOx@ZIF-8 were 0.03 ± 0.02 mM and 63.87 ± 1.96 s^-1 mM^-1, respectively, which were superior to corresponding values of free GOx. Therefore, the 3-MPBA/GOx@ZIF-8 displayed high catalytic efficiency, high loading efficiency and enhanced stability. Moreover, a new type of visual colorimetric sensor for screening of the diabetes was realized through the 3-MPBA/GOx@ZIF-8, which provided a new strategy for the analysis field of glucose.

Silica Capsules Templated from Metal-Organic Frameworks for Enzyme Immobilization and Catalysis

Inspired by the unique biological microenvironments of eukaryotic cells, hollow capsules are promising to immobilize enzymes due to their advantages for physical protection and improved activity of enzymes. Herein, we report a facile method to fabricate silica (SiO₂) capsules using zeolitic imidazole framework-8 nanoparticles (ZIF-8 NPs) as templates for enzyme immobilization and catalysis. Enzyme-encapsulated SiO₂ capsules are obtained by encapsulation of enzymes in ZIF-8 NPs and subsequent coating of silica layers, followed by the removal of templates in a mild condition (i.e., ethylenediaminetetraacetic acid (EDTA) solution). The enzyme (i.e., horseradish peroxidase, HRP) activity in SiO₂ capsules is improved more than 15 times compared to that of enzyme-loaded ZIF-8 NPs. Enzymes in SiO₂ capsules maintain a high relative activity after being subjected to high temperature, enzymolysis, and recycling compared to free enzymes. In addition, multienzymes (e.g., glucose oxidase and HRP) can also be coencapsulated within SiO₂ capsules to show a reaction with a high cascade catalytic efficacy. This work provides a versatile strategy for enzyme immobilization and protection with potential applications in biocatalysis.

One-pot surface modification of magnetic nanoparticles using phase-transitioned lysozyme for robust immobilization of enzymes

Enzymes were one-pot immobilized between Fe₃O₄ nanoparticles and a phase-transitioned lysozyme film, providing a new strategy for enzyme immobilization.

Biocatalytic metal–organic framework nanomotors for active water decontamination

Biocatalytic metal–organic framework nanomotors for active removal of heavy metal ions and per- and poly-fluoroalkyl substances in aqueous environments.