Preparation of core–shell magnetic polydopamine/alginate biocomposite for Candida rugosa lipase immobilization

Self-Assembly-Activated Engineered Magnetic Biohybrids Loaded with Phosphotriesterase for Sustainable Decontamination and Detection of Organophosphorus Pesticides

Phosphotriesterase (PTE) biodegradation of organophosphorus pesticides (OPs) is an efficient and environmentally friendly method. However, the instability and nonreusability of free PTE become the key factors restricting its practical application. In this study, a novel cross-linked magnetic hybrid nanoflower (CLMNF) was prepared. Molecular dynamics (MD) simulations were performed to further investigate the enhanced catalytic efficiency of the enzymes. The recovery rate of enzyme activity was 298% due to the large specific surface area and metal ion activation effect. More importantly, the immobilization scheme greatly improved the stability and reuse performance of the catalyst and simplified the recovery operation. CLMNFs retained 90.32% relative activity after 5 consecutive cycles and maintained 84.8% relative activity after 30 days at 25 °C. It has a good practical application prospect in the degradation and detection of OPs. Consequently, the immobilized enzyme as a biocatalyst has the characteristics of high efficiency, stability, safety, and easy separation, establishing the key step in a biodetoxification system to control organophosphorus contamination in food and the environment.

Spacer arm of ionic liquids facilitated laccase immobilization on magnetic graphene enhancing its stability and catalytic performance

To fulfill the requirements of environmental protection, a magnetically recoverable immobilized laccase has been developed for water pollutant treatment. In order to accomplish this objective, we propose a polydopamine-coated magnetic graphene material that addresses the challenges associated with accumulation caused by electrostatic interactions between graphene and enzyme molecules, which can lead to protein denaturation and inactivation. To achieve this, we present a polydopamine-coated magnetic graphene material that binds to the enzyme molecule through flexible spacer arms formed by ionic liquids. The immobilized laccase exhibited a good protective effect on laccase and showed a high stability and recycling ability. Laccase-ILs-PDA-MGO has a wider pH and temperature range and retains about 80% of its initial activity even after incubation at 50 °C for 2 h, which is 2.2 times more active than free laccase. Furthermore, the laccase-ILs-PDA-MGO exhibited a remarkable removal efficiency of 97.0% and 83.9% toward 2,4-DCP and BPA within 12 h at room temperature. More importantly, laccase-ILs-PDA-MGO can be recovered from the effluent and used multiple times for organic pollutant removal, while maintaining a relative removal efficiency of 80.6% for 2,4-DCP and 81.4% for BPA after undergoing seven cycles. In this study, a strategy for laccase immobilization by utilizing ILs spacer arms to modify GO aims to provide valuable insights into the advancement of efficient enzyme immobilization techniques and the practical application of immobilized enzymes in wastewater treatment.

Mussel-Inspired Polymer-Based Coating Technology for Antifouling and Antibacterial Properties

Zwitterionic coatings provide a promising antifouling strategy against biofouling adhesion. Quaternary ammonium cationic polymers can effectively kill bacteria on the surface, owing to their positive charges. This strategy can avoid the release of toxic biocides, which is highly desirable for constructing coatings for biomedical devices. The present work aims to develop a facile method by covalently grafting zwitterionic and cationic copolymers containing aldehydes to the remaining amine groups of self-polymerized dopamine. Reversible addition-fragmentation chain transfer polymerization was used to copolymerize either zwitterionic 2-methacryloyloxyethyl phosphorylcholine monomer (MPC) or cationic 2-(methacryloyloxy)ethyl trimethylammonium monomer (META) with 4-formyl phenyl methacrylate monomer (FPMA), and the formed copolymers poly(MPC-st-FPMA) and poly(META-st-FPMA) are denoted as MPF and MTF, respectively. MPF and MTF copolymers were then covalently grafted onto the amino groups of polydopamine-coated surfaces. PDA/MPF/MTF-coated surfaces exhibited antibacterial and antifouling properties against S. aureus, E. coli, and bovine serum albumin protein. In addition, they showed excellent viability of normal human lung fibroblast cells MRC-5. We expect the facile surface modification strategy discussed here to be applicable to medical device manufacturing.

Recent Advances in Dopamine-Based Membrane Surface Modification and Its Membrane Distillation Applications

Surface modification of membranes is essential for improving flux and resistance to contamination for membranes. This is of great significance for membrane distillation, which relies on the vapor pressure difference across the membrane as the driving force. In recent years, biomimetic mussel-inspired substances have become the research hotspots. Among them, dopamine serves as surface modifiers that would achieve highly desirable and effective membrane applications owing to their unique physicochemical properties, such as universal adhesion, enhanced hydrophilicity, tunable reducibility, and excellent thermal conductivity. The incorporation of a hydrophilic layer, along with the utilization of photothermal properties and post-functionalization capabilities in modified membranes, effectively addresses challenges such as low flux, contamination susceptibility, and temperature polarization during membrane distillation. However, to the best of our knowledge, there is still a lack of comprehensive and in-depth discussions. Therefore, this paper systematically compiles the modification method of dopamine on the membrane surface and summarizes its application and mechanism in membrane distillation for the first time. It is believed that this paper would provide a reference for dopamine-assisted membrane separation during production, and further promote its practical application.

Co-immobilization of electron mediator and laccase onto dialdehyde starch cross-linked magnetic chitosan nanomaterials for organic pollutants’ removal

In this study, an amino-functionalized ionic liquid-modified magnetic chitosan (MACS-NIL) containing 2,2-diamine-di-3-ethylbenzothiazolin-6-sulfonic acid (ABTS) was used as a carrier, and dialdehyde starch (DAS) was used as a cross-linking agent to covalently immobilize laccase (MACS-NIL-DAS-lac), which realized the co-immobilization of laccase and ABTS. The carrier was characterized by Fourier infrared transform spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray diffraction analysis, electron paramagnetic resonance, etc. The immobilization efficiency and activity retention of MACS-NIL-DAS-lac could reach 76.7% and 69.8%, respectively. At the same time, its pH stability, thermal stability, and storage stability had been significantly improved. In the organic pollutant removal performance test, the removal rate of 2,4-dichlorophenol (10 mg/L) by MACS-NIL-DAS-lac (1 U) could reach 100% within 6 h, and the removal efficiency could still reach 88.6% after six catalytic runs. In addition, MACS-NIL-DAS-lac also showed excellent degradation ability for other conventional phenolic pollutants and polycyclic aromatic hydrocarbons. The research results showed that MACS-NIL-DAS fabricated by the combination inorganic material, organic biomacromolecules, ionic liquid, and electron mediator could be used as a novel carrier for laccase immobilization and the immobilized laccase showed excellent removal efficiency for organic pollutants.

Lipase-polydopamine magnetic hydrogel microspheres for the synthesis of octenyl succinic anhydride starch

Octenyl succinic anhydride (OSA) starch is an important edible additive in the food field, and its synthesis method has attracted much attention. Lipase as a biocatalyst can improve the synthesis efficiency of OSA starch, and significantly inhibit the occurrence of side reactions. However, free lipase has not been widely applied in the synthesis of OSA starch due to the difficulty of separation from starch and poor reusability. In this work, a promising strategy for the synthesis of OSA starch catalyzed by lipase immobilized on polydopamine magnetic hydrogel microspheres (PMHM) is reported. The prepared lipase-polydopamine magnetic hydrogel microspheres (L-PMHM) can be uniformly dispersed in starch slurry, which is conducive to the full contact between lipase and starch. L-PMHM (Km =2.6276 μmol/mL) exhibits better affinity to the substrate than free lipase (Km = 3.4301 μmol/mL). Compared with the OSA starch catalyzed by free lipase (DS = 0.0176), the degree of substitution of OSA starch catalyzed by L-PMHM is up to 0.0277 in a short reaction time. In cyclic catalysis, L-PHMM can remain about 48 % of their original activity after 20 reuses and can be quickly separated from the product. These results suggest that L-PMHM has great potential as a biocatalyst for the efficient synthesis of OSA starch.

A robust biocatalyst based on laccase immobilized superparamagnetic Fe3O4@SiO2-NH2 nanoparticles and its application for degradation of chlorophenols

The presence of chlorophenols in water and wastewater is considered a serious environmental issue. To eliminate these micropollutants, biodegradation of chlorophenols using enzyme-nanoparticle conjugated biocatalyst, is proposed as an economical and eco-friendly method. Herein, amino-functionalized superparamagnetic Fe₃O₄@SiO₂-NH₂ nanoparticles with core-shell structure were constructed as a promising carrier for immobilization of laccase from Trametes versicolor. Compared with free laccase, Fe₃O₄@SiO₂-NH₂-Laccase displayed remarkable outcomes in all major areas such as temperature and storage stabilities, and tolerance to organic solvents and metal ions. The biocatalytic performance and reusability of Fe₃O₄@SiO₂-NH₂-Laccase were evaluated for the degradation of 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) in repeated cycles. Even after 10 successive reuses, the degradation rate of 2,4-DCP and 2,4,6-TCP were found to be 54.9% and 68.7%, respectively. The influences of solution pH, initial chlorophenol concentration, and temperature on the degradation rate of these two chlorophenols were evaluated. The degradation intermediate products including dimers, trimers, and tetramers of 2,4-DCP and 2,4,6-TCP were identified. Release of chloride ions was observed during the enzymatic degradation of these two chlorophenols. Based on the determination of intermediate products and released chloride ions, the degradation pathway that was involved in dehydrogenation, reactive radical intermediates formation, dechlorination, self-coupling and oligomers/polymers formation was proposed. The toxicity of these two chlorophenols and their intermediates was substantially reduced during the enzymatic degradation. The results of this study might present an alternative clean biotechnology for the remediation of 2,4-DCP and 2,4,6-TCP contaminated water matrices.

Enhancing bio-catalytic performance of lipase immobilized on ionic liquids modified magnetic polydopamine

In this study, imidazolium-based ionic liquid with [tf₂N]^- as the anion was successfully grafted to magnetic polydopamine nanoparticles (MPDA). The prepared materials were well characterized and used as supports for lipase immobilization. The immobilized lipase (PPL-ILs-MPDA) exhibited excellent activity and stability. The specific activity of PPL-ILs-MPDA was 2.15 and 1.49 folds higher than that of free PPL and PPL-MPDA. In addition, after 10 rounds of reuse, the residual activity of PPL-ILs-MPDA was 86.2 % higher than that of PPL-MPDA (75.4 %). Furthermore, the kinetic assay indicated that the affinity between PPL-ILs-MPDA and substrate had increased. Analysis of the secondary structure using circular dichroism was used to explain the mechanism underlying the improvement in the performance of PPL-ILs-MPDA. In addition, the immobilized lipase can be easily separated from the reaction system with a magnet. The observations regarding the development of new supports for lipase immobilization may provide new ideas regarding further studies in this field.

Mussel-inspired hybrid network hydrogel for continuous adhesion in water

The mussel-inspired catechol-based strategy has been widely used in the development of adhesives. However, the properties of the obtained adhesives were still severely limited in a humid environment, particularly in water. In this study, a facile and versatile approach was proposed to prepare an underwater adhesion hydrogel. First, dopamine (DA) was grafted on oxidized carboxymethylcellulose (OCMC) to obtain dopamine-grafted oxidized carboxymethylcellulose (OCMC-DA). Second, the acrylamide (AM) monomer was conjugated with OCMC-DA by a Schiff base reaction, and then polymerized to form an OCMC-DA/PAM hydrogel. The properties of the resulting hydrogel have been fully characterized. The underwater adhesion strength of the hydrogel can reach as high as 86.3 ± 7.2 kPa and reduced to 43 ± 3.4 kPa after being immersed in water for 9 days. More remarkably, we found that the maximal adhesion strength was shown when the G' and G'' of the hydrogel were very close. Moreover, we demonstrated the mechanical properties of our fabricated hydrogel by compressive tests and rheological analysis. The adhesive hydrogel also exhibits excellent biocompatibility.

Structure validation of oxidized poly (2-hydroxyethyl acrylate) with multiple aldehyde groups and its application for collagen modification

The structural characteristic of oxidized poly (2-hydroxyethyl acrylate) (OP) was confirmed by high-performance liquid chromatography, gel permeation chromatography and hydroxylamine hydrochloride titration. The results demonstrated that OP prepared through 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidation of poly (2-hydroxyethyl acrylate) was featured by multiple aldehyde groups on its side chain, with no free formaldehyde produced during the oxidation process. The computational simulation for the electrophilic reactivity of OP molecule showed that the reactivity of the aldehyde groups in OP with the amino groups of collagen was comparable to that of glutaraldehyde. In this study, OP was chosen as a collagen modifier to investigate the modification effects on the secondary structure, aggregation behaviour and thermal stability of collagen. The covalent cross-linking occurred between the aldehyde groups of OP and the amino groups of collagen under alkaline condition. The covalent binding between OP and collagen was strengthened with the increasing reaction pH and OP dosage, and the triple helix of collagen was altered to some degree. Furthermore, OP promoted the intense aggregation of collagen and enhanced the thermal stability of collagen. This work provides guidance for preparing novel collagen modifier with multiple aldehyde groups.

Preparation of high-strength and high-toughness biomass medical films based on a polydopamine dynamically united calcium alginate/carboxymethyl chitosan dual network

A high-strength and high-toughness biomass medical film was prepared using a polydopamine dynamically united calcium alginate/carboxymethyl chitosan dual network.

Sustainable dialdehyde polysaccharides as versatile building blocks for fabricating functional materials: An overview

Dialdehyde polysaccharide (DAP), containing multiple aldehyde groups, can react with materials having amino groups via Schiff base crosslinking. Besides, it can also react with materials having carbonyl/hydroxyl groups via aldol reactions. Based on these intriguing properties, DAPs can be employed as versatile building blocks to fabricate functional materials used in biomedical field, wastewater treatment, leather manufacture, and electrochemistry field. This review aims to provide an overview of the recent advances in fabricating biomaterials, adsorbents, leather tanning agents, and electrochemical materials based on DAPs. The basic fabricating strategy and principle of these materials and their performances are overall summarized, along with a discussion of associated scalability challenges, technological strategies to overcome them, and the prospect for commercial translations of this versatile material. Blending the versatility of DAP with material science and technological advances can provide a powerful tool to develop more DAP-based functional materials in a scalable way.

Recent Trends in Biomaterials for Immobilization of Lipases for Application in Non-Conventional Media

The utilization of biomaterials as novel carrier materials for lipase immobilization has been investigated by many research groups over recent years. Biomaterials such as agarose, starch, chitin, chitosan, cellulose, and their derivatives have been extensively studied since they are non-toxic materials, can be obtained from a wide range of sources and are easy to modify, due to the high variety of functional groups on their surfaces. However, although many lipases have been immobilized on biomaterials and have shown potential for application in biocatalysis, special features are required when the biocatalyst is used in non-conventional media, for example, in organic solvents, which are required for most reactions in organic synthesis. In this article, we discuss the use of biomaterials for lipase immobilization, highlighting recent developments in the synthesis and functionalization of biomaterials using different methods. Examples of effective strategies designed to result in improved activity and stability and drawbacks of the different immobilization protocols are discussed. Furthermore, the versatility of different biocatalysts for the production of compounds of interest in organic synthesis is also described.

Fabrication of biodegradable auto-fluorescent organosilica nanoparticles with dendritic mesoporous structures for pH/redox-responsive drug release

In this work, disulfide-bridged organic silica (OS) based nanocarriers were constructed for drug release. The broken of SS bonds in Si-O-Si skeleton would improve the degradation of Si-O-Si of OS carriers. The OS carriers have a central-radiated dendritic porous structure and a large specific surface area of 453.80 m²g^-1. The dextrin was selectively oxidized to dialdehyde dextrin (DAD) and then was modified on the surface of OS carriers by Schiff base bonds. Subsequently, cystamine (Cys) was linked with DAD to form DAD/Cys layer (OS-N=C-DAD/Cys) to seal the loaded drug. The DAD/Cys layer display the degradation performance of pH/GSH dual response The obtained OS-N=C-DAD/Cys carriers displayed low premature and the cumulative release was 6.5% under normal physiological conditions within 48 h. The Schiff base (-N=C-) structure in the DAD/Cys layer is also capable of monitoring acid-responsive drug release by fluorescence change. The prepared OS-N=C-DAD/Cys carriers and their degraded products have high biocompatibility.

A self-powered delivery substrate boosts active enzyme delivery in response to human movements

Stimulated drug releases in response to human movements are highly appealing in medical therapy and various daily uses. However, the design of a mechanically responsive substrate that presents high delivery capacities and can also preserve the activities of sensitive molecules such as enzymes is still challenging. Taking advantage of the recent development in effective piezoelectric flexible films and in molecular delivery devices, we propose a composite delivery substrate that preserves enzyme activities and enhances molecular delivery in response to human movements such as finger presses or massages. The substrate is achieved by combining two parts, which are the energy converting unit and the molecular loading and releasing unit. The energy converting unit is a piezoelectric-dielectric flexible composite film that produces enhanced electricity and preserves the electricity longer compared to a pure piezoelectric polymer. The molecular delivery unit is a layer-by-layer multilayer containing mesoporous silica particles that are assembled at pH 9 but used in neutral solutions. The releases of molecules including small molecules, peptides, and proteins are all accelerated in response to finger presses irrespective of the signs or densities of their charges. More importantly, the enzyme CAT preserves its activity after release from the composite substrates, meaning that the CAT-loaded (PAH/MS)n(PAH/DAS)n@rGO-TFB/PVDF-HFP composite substrate holds promise as a self-powered soothing pad that effectively removes residue H2O2.

Immobilization of a Novel ESTBAS Esterase from Bacillus altitudinis onto an Epoxy Resin: Characterization and Regioselective Synthesis of Chloramphenicol Palmitate

Novel gene estBAS from Bacillus altitudinis, encoding a 216-amino acid esterase (EstBAS) with a signal peptide (SP), was expressed in Escherichia coli. EstBASΔSP showed the highest activity toward p-nitrophenyl hexanoate at 50 °C and pH 8.0 and had a half-life (T1/2) of 6 h at 50 °C. EstBASΔSP was immobilized onto a novel epoxy resin (Lx-105s) with a high loading of 96 mg/g. Fourier transform infrared (FTIR) spectroscopy showed that EstBASΔSP was successfully immobilized onto Lx-105s. In addition, immobilization improved its enzymatic performance by widening the tolerable ranges of pH and temperature. The optimum temperature of immobilized EstBASΔSP (Lx-EstBASΔSP) was higher, 60 °C, and overall thermostability improved. T1/2 of Lx-EstBASΔSP and free EstBASΔSP at 60 °C was 105 and 28 min, respectively. Lx-EstBASΔSP was used as a biocatalyst to synthesize chloramphenicol palmitate by regioselective modification at the primary hydroxyl group. Conversion efficiency reached 94.7% at 0.15 M substrate concentration after 24 h. Lx-EstBASΔSP was stable and could be reused for seven cycles, after which it retained over 80% of the original activity.

Low-cost mussel inspired poly(Catechol/Polyamine) modified magnetic nanoparticles as a versatile platform for enhanced activity of immobilized enzyme

Owing to dopamine's excellent adhesion ability and easy modification, it has been widely applied for enzyme immobilization, while the high cost of dopamine and low activity recovery of immobilized enzyme highly impede large-scale application of immobilized enzyme. We herein developed a low-cost and ideal activity recovery enzyme immobilization strategy based on magnetic nanoparticles by replacing dopamine with cheap Catechol/tetraethylene pentamine (CPA) binary system and introducing spacer-arms. In brief, CPA was first polymerized and deposited on the surface of magnetic nanoparticles with a modified mussel-inspired method, and the generated poly(CPA) layer was further functionalized with ethylene glycol diglycidyl ether (EGDE) molecules as spacer-arms for enzyme immobilization. Subsequently, lipases as model enzymes were firmly immobilized on the surface of such amino-epoxy functionalized magnetic materials through ion exchange and covalent attachment with 180.6 mg/g support of loading capacity and 69.2% of activity recovery under the optimized conditions. Furthermore, the immobilized lipase exhibited the improved tolerance rang of pH, temperature and storage stability as well as excellent reusability. Most strikingly, the theoretical simulation and secondary structure analysis of immobilized lipase revealed that the biocompatible microenvironment and flexible tethering at interface could effectively improve performance of the immobilized enzyme and stability. Thus, this novel immobilized enzyme strategy will open up a new perspective for the development of enzyme immobilization and lower the cost of immobilized enzyme in large-scale industrial application.

Antibiofilm effect of chlorhexidine-carrier nanosystem based on iron oxide magnetic nanoparticles and chitosan

This study synthesized and characterized a chlorhexidine (CHX)-carrier nanosystem based on iron oxide magnetic nanoparticles (IONPs) and chitosan (CS), and evaluated its antimicrobial effect on mono- and dual-species biofilms of Candida albicans and Streptococcus mutans. CHX was directly solubilized in CS-coated IONPs and maintained under magnetic stirring for obtaining the IONPs-CS-CHX nanosystem. Antimicrobial susceptibility testing for planktonic cells was performed by determining the minimum inhibitory concentration (MIC) of the nanosystem and controls. The effects of the IONPs-CS-CHX nanosystem on the formation of mono- and dual-species biofilms, as well as on pre-formed biofilms were assessed by quantification of total biomass, metabolic activity and colony-forming units. Data were analyzed by the Kruskal-Wallis' test or one-way analysis of variance, followed by the Student-Newman-Keuls' or Holm-Sidak's tests (α = 0.05), respectively. Physico-chemical results confirmed the formation of a nanosystem with a size smaller than 40 nm. The IONPs-CS-CHX nanosystem and free CHX showed similar MIC values for both species analyzed. In general, biofilm quantification assays revealed that the CHX nanosystem at 78 μg/mL promoted similar or superior antibiofilm effects compared to its counterpart at 39 μg/mL and free CHX at 78 μg/mL. These findings highlight the potential of CS-coated IONPs as preventive or therapeutic agents carrying CHX to fight biofilm-associated oral diseases.

Functional polymeric dialdehyde dextrin network capped mesoporous silica nanoparticles for pH/GSH dual-controlled drug release

Multi-stimulation responsive nanomaterial-based drug delivery systems promise enhanced therapeutic efficacy in cancer therapy. This work examines a smart pH/GSH dual-responsive drug delivery system by using dialdehyde dextrin (DAD) end-capped mesoporous silica nanoparticles (MSNs). Specifically, DAD was applied as a "gatekeeper polymer" agent to seal drug loads inside the mesoporous of MSNs via a pH-sensitive Schiff bond, whereas the formed DAD polymer shells were further cross-linked by GSH-sensitive disulfide bonds. Results revealed that the DAD gatekeeper polymer could tightly close the mesopores of MSNs to control premature drug release under physiological conditions and respond to acidic and GSH conditions to release the trapped drugs. Significantly, fluorescent microscopy observation and cytotoxicity studies indicated that drug-loaded nanoparticles could be rapidly internalized through a passive targeting effect to inhibit cancer growth. Taken together, these polymer-modified pH/GSH dual-responsive MSNs could be used as promising candidates for "on-demand" anticancer drug delivery applications.

Dopamine-assisted co-deposition: An emerging and promising strategy for surface modification

Mussel-inspired chemistry based on polydopamine (PDA) deposition has been developed as a facile and universal method for the surface modification of various materials. However, the inherent shortcomings of PDA coatings still impede their practical applications in the development of functional materials. In this review, we introduce the recent progress in the emerging dopamine-assisted co-deposition as a one-step strategy for functionalizing PDA-based coatings, and improving them in the aspects of deposition rate, morphology uniformity, surface wettability and chemical stability. The co-deposition mechanisms are categorized and discussed according to the interactions of dopamine or PDA with the introduced co-component. We also emphasize the influence of these interactions on the properties of the resultant PDA-based coatings. Meanwhile, we conclude the representative potential applications of those dopamine-assisted co-deposited coatings in material science, especially including separation membranes and biomaterials. Finally, some important issues and perspectives for theoretical study and applications are briefly discussed.

Novel amphiphilic polyvinylpyrrolidone functionalized silicone particles as carrier for low-cost lipase immobilization

The high catalytic activity, specificity and stability of immobilized lipase have been attracting great interest. How to reduce the cost of support materials has always been a hot topic in this field. Herein, for the development of low-cost immobilized lipase, we demonstrate an amphiphilic polyvinylpyrrolidone (PVP) grafted on silicone particle (SP) surface materials (SP-PVP) with a rational design based on interfacial activation and solution polymerization. Meanwhile, hydrophilic pristine SP and hydrophobic polystyrene-corded silicone particles (SP-Pst) were also prepared for lipase immobilization. SP-PVP was characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and thermogravimetry. Our results indicated that the lipase loading amount on the SP-PVP composites was about 215 mg of protein per gram. In the activity assay, the immobilized lipase SP-PVP@CRL exhibited higher catalysis activity and better thermostability and reusability than SP@CRL and SP-Pst@CRL. The immobilized lipase retained more than 54% of its initial activity after 10 times of re-use and approximately trended to a steady rate in the following cycles. By introducing the interesting amphiphilic polymer to this cheap and easily obtained SP surface, the relative performance of the immobilized lipase can be significantly improved, facilitating interactions between the low-cost support materials and lipase.

Preparation and Evaluation of Coal Fly Ash/Chitosan Composites as Magnetic Supports for Highly Efficient Cellulase Immobilization and Cellulose Bioconversion

Two magnetic supports with different morphologies and particle sizes were designed and prepared for cellulase immobilization based on chitosan and industrial by-product magnetic coal fly ash (MCFA). One was prepared by coating chitosan onto spherical MCFA particles to form non-porous MCFA@chitosan gel microcomposites (Support I) with a size of several micrometers, and the other was prepared using the suspension method to form porous MCFA/chitosan gel beads (Support II) with a size of several hundred micrometers. Cellulase was covalent binding to the support by glutaraldehyde activation method. The morphology, structure and magnetic property of immobilized cellulase were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and a vibrating-sample magnetometer. The cellulase loading on Support I was 85.8 mg/g with a relatlvely high activity recovery of 76.6%, but the immobilized cellulase exhibited low thermal stability. The cellulase loading on Support II was 76.8 mg/g with a relative low activity recovery of 51.9%, but the immobilized cellulase showed high thermal stability. Cellulase immobilized on Support I had a glucose productivity of 219.8 mg glucose/g CMC and remained 69.9% of the original after 10 cycles; whereas the glucose productivity was 246.4 mg glucose/g CMC and kept 75.5% of its initial value after 10 repeated uses for Support II immobilized cellulase. The results indicate that the two supports can be used as cheap and effective supports to immobilize enzymes.

Degradation of nonylphenol polyethoxylates by functionalized Fe3O4 nanoparticle-immobilized Sphingomonas sp. Y2

In this study, the efficiency of the nonylphenol polyethoxylates (NPEOs)-degrading bacterium Sphingomonas sp. strain Y2 was evaluated, which was immobilized by a novel system composed of polydopamine (PD)-coated Fe₃O₄ iron nanoparticles (IONPs). The PD-IONPs, with a distinct core-shell structure, relatively uniform size, and high saturation magnetization, were prepared for Y2 immobilization. The performance of Y2 was unaffected by this novel immobilization method, exhibiting 79.5% and 99.9% of NPEOs (500ppm) degradation efficiency at day 1 and 2, respectively. Furthermore, separation and recycling were more readily achieved for immobilized cells as compared to free cells. Immobilized cells retained over 70% of the original degradation activity after 6cycles of utilization. These results suggest that Y2-PD-IONPs can be potentially used for NPEOs-contaminated wastewater bioremediation.

CAPSULE

Immobilization of Sphingomonas sp. Y2 by functionalized PD-IONPs with easy separation, recycling utilization and high efficiency.

A polypyrrole–methyl anthranilate functionalized worm-like titanium dioxide nanocomposite as an innovative tool for immobilization of lipase: preparation, activity, stability and molecular docking investigations

Schematic of the novel synthesised nanobioconjugates.

Enzyme Engineering for In Situ Immobilization

Enzymes are used as biocatalysts in a vast range of industrial applications. Immobilization of enzymes to solid supports or their self-assembly into insoluble particles enhances their applicability by strongly improving properties such as stability in changing environments, re-usability and applicability in continuous biocatalytic processes. The possibility of co-immobilizing various functionally related enzymes involved in multistep synthesis, conversion or degradation reactions enables the design of multifunctional biocatalyst with enhanced performance compared to their soluble counterparts. This review provides a brief overview of up-to-date in vitro immobilization strategies while focusing on recent advances in enzyme engineering towards in situ self-assembly into insoluble particles. In situ self-assembly approaches include the bioengineering of bacteria to abundantly form enzymatically active inclusion bodies such as enzyme inclusions or enzyme-coated polyhydroxyalkanoate granules. These one-step production strategies for immobilized enzymes avoid prefabrication of the carrier as well as chemical cross-linking or attachment to a support material while the controlled oriented display strongly enhances the fraction of accessible catalytic sites and hence functional enzymes.

Recent developments in polydopamine: an emerging soft matter for surface modification and biomedical applications

After more than four billion years of evolution, nature has created a large number of fascinating living organisms, which show numerous peculiar structures and wonderful properties. Nature can provide sources of plentiful inspiration for scientists to create various materials and devices with special functions and uses. Since Messersmith proposed the fabrication of multifunctional coatings through mussel-inspired chemistry, this field has attracted considerable attention for its promising and exiciting applications. Polydopamine (PDA), an emerging soft matter, has been demonstrated to be a crucial component in mussel-inspired chemistry. In this review, the recent developments of PDA for mussel-inspired surface modification are summarized and discussed. The biomedical applications of PDA-based materials are also highlighted. We believe that this review can provide important and timely information regarding mussel-inspired chemistry and will be of great interest for scientists in the chemistry, materials, biology, medicine and interdisciplinary fields.