Direct affinity immobilization of recombinant heparinase I fused to maltose binding protein on maltose-coated magnetic nanoparticles

Directed Immobilization of PETase on Mesoporous Silica Enables Sustained Depolymerase Activity in Synthetic Wastewater Conditions

Microplastic accumulation in terrestrial and aquatic environments is a growing environmental challenge. Biodegradation has shown promise as an intervention strategy for reducing the spread of microplastics. The wastewater treatment system is a key intervention point in microplastic biodegradation due to its pivotal role in the water cycle at the interface between human activity and the environmental. However, the best characterized microplastic degradation enzyme, PETase, lacks the stability to perform at scale in wastewater treatment. In this work, we show that genetic fusion of PETase to a silica binding peptide enables directed immobilization of the enzyme onto silica nanoparticles. PETase activity in simulated wastewater conditions is quantified by linear regression from time zero to the time of maximum fluorescence of a fluorescent oxidized product of PETase degradation of PET microfibers. Mesoporous silica is shown to be a superior support material to nonporous silica. The resulting biocatalytic nanomaterial has up to 2.5-fold enhanced stability and 6.2-fold increased activity compared to free enzyme in unbuffered, 40 °C simulated influent (ionic strength ∼15 mM). In unbuffered, 40 °C simulated effluent (ionic strength ∼700 μM), reaction velocity and overall catalytic activity were increased by the biocatalytic material 2.1-fold relative to free PETase. All reactions were performed in 0.2 mL volumes, and enzyme concentrations were normalized across both free and immobilized samples to 9 μg/mL. Site-directed mutagenesis is shown to be a complementary technique to directed immobilization, which may aid in optimization of the biomaterial for wastewater applications. PETase stabilization in application-relevant environments as shown here enables progress toward application of PETase for microplastic biodegradation in wastewater treatment.

Magnetic particles for enzyme immobilization: A versatile support for ligand screening

Enzyme inhibitors represent a substantial fraction of all small molecules currently in clinical use. Therefore, the early stage of drug-discovery process and development efforts are focused on the identification of new enzyme inhibitors through screening assays. The use of immobilized enzymes on solid supports to probe ligand-enzyme interactions have been employed with success not only to identify and characterize but also to isolate new ligands from complex mixtures. Between the available solid supports, magnetic particles have emerged as a promising support for enzyme immobilization due to the high superficial area, easy separation from the reaction medium and versatility. Particularly, the ligand fishing assay has been employed as a very useful tool to rapidly isolate bioactive compounds from complex mixtures, and hence the use of magnetic particles for enzyme immobilization has been widespread. Thus, this review provides a critical overview of the screening assays using immobilized enzymes on magnetic particles between 2006 and 2021.

Immobilization of dihydroflavonol 4-reductase on magnetic Fe3O4–PEI-pMaltose nanomaterials for the synthesis of anthocyanidins

An Fe3O4–PEI-pMaltose-immobilized DFR enzyme was prepared using nano-biotechnology, which can catalyze the synthesis of anthocyanidins in vitro.

Affinity-binding immobilization of D-amino acid oxidase on mesoporous silica by a silica-specific peptide

Enzyme immobilization is widely used for large-scale industrial applications. However, the weak absorption through physical methods limits the recovery ability. Here, affinity-binding immobilization of enzymes was explored using a silica-specific affinity peptide (SAP) as a fusion tag to intensify the binding force between the enzyme and mesoporous silica (MPS) carrier. D-amino acid oxidase (DAAO) of Rhodosporidium toruloides was used as a model enzyme. The optimal screened SAP (LPHWHPHSHLQP) was selected from a M13 phage display peptide library and fused to the C-terminal of DAAO to obtain fused DAAOs with one, two and three SAP tags, respectively. The activity of DAAO-SAP-MPS was superior comparing with DAAO-2SAP-MPS and DAAO-3SAP-MPS; meanwhile DAAO-SAP-MPS shows 36% higher activity than that of DAAO-MPS. Fusion with one SAP improved the thermal stability with a 10% activity increase for immobilized DAAO-SAP-MPS compared to that of DAAO-MPS at 50 °C for 3 h. Moreover, the activity recovery of immobilized DAAO-SAP-MPS was 25% higher in operation stability assessment after six-batch conversions of cephalosporin to glutaryl-7-amino cephalosporanic acid than that of DAAO-MPS.

An engineered platform based on chitin-affinity immobilization for producing low molecular weight heparin

Using chitin-affinity interaction between triple-functional heparinase I (Hep I) and chitin, an engineered platform was prepared to produce controllable low molecular weight heparin (LMWH). Chitin microspheres with well-defined nanofibrils were fabricated through a "bottom up" pathway. An enhanced soluble protein, ChBD-SUMO-Hep I (CSH-I), was expressed in 3L batch fermentation with a high bioactivity of 2.5×10³ IU/L. Chitin binding domain (ChBD) can specifically bind to chitin in noncovalent way, which leads to the immobilization and purification of enzyme in a single step. The immobilized CSH-I was preferred over its free counterpart due to its higher tolerance to heat and pH, as well as improved shelf-life. The restraint enzyme could be reused up to 8 times to achieve a conversion yield exceeding 90%. By using the bioinspired conjugates, the qualified LMWH fractions were obtained by monitoring the degradation process with an absorbance range of 44.5-68.3 at 232nm.

Regulation of the catalytic behavior of pullulanases chelated onto nickel (II)-modified magnetic nanoparticles

Chelating of pullulanases onto nickel (II)-modified magnetic nanoparticles results in one-step purification and immobilization of pullulanase, and facilitates the commercial application of pullulanase in industrial scale. To improve the catalytic behavior, especially the operational stability, of the nanocatalyst in consecutive batch reactions, we prepared various iminodiacetic acid-modified magnetic nanoparticles differed in surface polarity and spacer length, on which the His6-tagged pullulanases were chelated via nickel ions, and then studied the correlation between the MNPs surface property and the corresponding catalyst behavior. When pullulanases were chelated onto the surface-modified MNPs, the thermostability of all pullulanase derivatives were lower than that of free counterpart, being not relevant to the protein orientation guided by the locality of the His6-tag, but related to the MNPs basal surface polarity and the grafted spacer length. After chelating of pullulanases onto MNPs, there were changes observed in the pH-activity profile and the apparent Michaelis constant toward pullulan. The changing tendencies were mainly dependent on the His6-tagged pullulanase orientation, and the changing extents were tuned by the spacer length. The reusability of pullulanase immobilized by N-terminal His6-tag was higher than that of pullulanase immobilized by C-terminal His6-tag. Moreover, the reusability of the immobilized pullulanase tested increased till grafting polyether amine-400 as spacer-arm, therefore the N-terminal His6-tagged pullulanase chelating MNPs grafted polyether amine-400 gave the best reusability, which retained 60% of initial activity after 18 consecutive cycles with a total reaction time of 9h. Additionally, the correlation analysis of the catalyst behaviors indicated that the reusability was independent from other catalytic properties such as thermostability and substrate affinity. All the results revealed that the catalyst behavior can be mainly controlled by the His6-tagged pullulanase orientation than by the MNPs surface property which can tune the catalyst function.

Recent Advances in Synthesis, Properties and Applications of Magnetic Oxide Nanomaterials

Oxide nanomaterials are in great demand due to their unique physical, chemical and structural properties. The nanostructured materials with desired magnetic properties are the future of power electronics. Unique magnetic properties and excellent biocompatibility of these materials found applications in pharmaceutical field also. For these applications, the synthesis of magnetic oxide nanomaterials with required properties is highly desirable. Till now, various techniques have been evolved for the synthesis of oxide nanomaterials with full control over their shape, size, morphology and magnetic properties. In nanoscale, the magnetic properties are totally different from their bulk counterparts. In this range, each nanoparticle acts as a single magnetic domain and shows fast response to applied magnetic field. This review article discusses the synthesis techniques, properties and the applications of magnetic oxide nanomaterials. Various characterization techniques for magnetic materials have been discussed along with the literature of iron oxide, nickel oxide, and cobalt oxide nanomaterials. The challenges for further development of these materials have also been presented to broaden their rapidly emerging applications.

Bio and nanomaterials based on Fe3O4

During the past few years, nanoparticles have been used for various applications including, but not limited to, protein immobilization, bioseparation, environmental treatment, biomedical and bioengineering usage, and food analysis. Among all types of nanoparticles, superparamagnetic iron oxide nanoparticles, especially Fe₃O₄, have attracted a great deal of attention due to their unique magnetic properties and the ability of being easily chemical modified for improved biocompatibility, dispersibility. This review covers recent advances in the fabrication of functional materials based on Fe₃O₄ nanoparticles together with their possibilities and limitations for application in different fields.