Preparation and characterization of copper-Brevibacterium cholesterol oxidase hybrid nanoflowers

From individuals to families: design and application of self-similar chiral nanomaterials

Establishing an intimate relationship between similar individuals is the beginning of self-extension. Various self-similar chiral nanomaterials can be designed using an individual-to-family approach, accomplishing self-extension. This self-similarity facilitates chiral communication, transmission, and amplification of synthons. We focus on describing the marriage of discrete cages to develop self-similar extended frameworks. The advantages of utilizing cage-based frameworks for chiral recognition, enantioseparation, chiral catalysis and sensing are highlighted. To further promote self-extension, fractal chiral nanomaterials with self-similar and iterated architectures have attracted tremendous attention. The beauty of a fractal family tree lies in its ability to capture the complexity and interconnectedness of a family's lineage. As a type of fractal material, nanoflowers possess an overarching importance in chiral amplification due to their large surface-to-volume ratio. This review summarizes the design and application of state-of-the-art self-similar chiral nanomaterials including cage-based extended frameworks, fractal nanomaterials, and nanoflowers. We hope this formation process from individuals to families will inherit and broaden this great chirality.

Development of a novel magnetic metal-organic framework for the immobilization of short-chain dehydrogenase for the asymmetric reduction of pro-chiral ketone

Short-chain dehydrogenase/reductase (SDR) acts as a biocatalyst in the synthesis of chiral alcohols with high optical purity. Herein, we achieved immobilization via crosslinking on novel magnetic metal-organic framework nanoparticles with a three-layer shell structure (Fe3O4@PDA@Cu (PABA)). The results of scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy confirmed the morphology and cross-linking property of immobilized SDR, which was more durable, stable, and reusable and exhibited better kinetic performance than free enzyme. The SDR and glucose dehydrogenase (GDH) were co-immobilized and then used for the asymmetric reduction of COBE and ethyl 2-oxo-4-phenylbutanoate (OPBE). These finding suggest that enzymes immobilized on novel MOF nanoparticles can serve as promising biocatalysts for asymmetric reduction prochiral ketones into chiral alcohols.

Bovine Serum Albumin - Hydroxyapatite Nanoflowers as Potential Local Drug Delivery System of Ciprofloxacin

Introduction

Hybrid nanoflowers are structures consisting of organic (enzymes, proteins, nucleic acids) and inorganic components (mostly metal phosphates) with a flower-like hierarchical structure. Novel hybrid nanoflowers based on bovine serum albumin (BSA) and hydroxyapatite (HA) were obtained and characterized. Study on BSA-HA nanoflowers as potential drug delivery system is reported for the first time.

Methods

Embedding ciprofloxacin in the structure of hybrid nanoflowers was confirmed by ATR-FTIR and thermogravimetric analysis. The inorganic phase of the nanoflowers was determined by X-ray diffraction. UV‒Vis spectroscopy was used to evaluate the release profiles of ciprofloxacin from nanoflowers in buffer solutions at pH 7.4 and 5. The agar disk diffusion method was used to study the antibacterial activity of the synthesized nanoflowers against Staphylococcus aureus and Pseudomonas aeruginosa.

Results

Bovine serum albumin - hydroxyapatite nanoflowers were obtained with diameters of ca. 1-2 µm. The kinetics of ciprofloxacin release from nanoflowers were described by the Korsmeyer-Peppas model. The antibacterial activity of the synthesized nanoflowers was demonstrated against S. aureus and P. aeruginosa, two main pathogens found in osteomyelitis.

Conclusion

The formulated nanoflowers may act as an efficient local antibiotic delivery system. Due to the use of nonhazardous, biodegradable components and benign synthesis, hybrid nanoflowers are very promising drug delivery systems that could be applied in the treatment of skeletal system infections.

Preparation and investigation of novel endopeptidase-exopeptidase co-immobilized nanoflowers with improved cascade hydrolysis

Enzymatic hydrolysis is a promising approach for protein and food processing. However, the efficiency of this approach is constrained by the self-hydrolysis, self-agglomeration of free enzymes and the limited applicability resulted from enzymes' selectivityt. Here, novel organic-inorganic hybrid nanoflowers (AY-10@AXH-HNFs) were prepared by coordinating Cu2+ with both endopeptidase of PROTIN SD-AY10 and exopeptidase of Prote AXH. The results indicate that the AY-10@AXH-HNFs exhibited 4.1 and 9.6 times higher catalytic activity than free Prote AXH and PROTIN SD-AY10, respectively, for the enzymatic hydrolysis of N-benzoyl-L-arginine ethyl ester (BAEE). The kinetic parameters of Km, Vmax and Kcat/Km by AY-10@AXH-HNFs were determined to be 0.6 mg/mL, 6.8 mL·min/mg and 6.1 mL/(min·mg), respectively, surpassing the values obtained from free endopeptidase and exopeptidase. Furthermore, the ability of AY-10@AXH-HNFs to retain 41 % of their initial catalytic activity after undergoing 5 cycles of repeated use confirmed their stability and reusability. This study introduces a novel approach of co-immobilizing endopeptidase and exopeptidase on nanoflowers, resulting in significantly enhanced stability and reusability of the protease in catalytic applications.

Hierarchically-structured laccase@Ni3(PO4)2 hybrid nanoflowers for antibiotic degradation: Application in real wastewater effluent and toxicity evaluation

Laccase@Ni₃(PO₄)₂ hybrid nanoflowers (HNFs) were prepared by the anisotropic growth of biomineralized nickel phosphate. The immobilization yield was 77.5 ± 3.6 %, and the immobilized enzyme retained 50 % of its initial activity after 18 reusability cycles. The immobilized and free enzymes lost 80 % of their activity after 18 and 6 h incubation in municipal wastewater effluent (MWWE), respectively. The increase in α-helix content (8 %) following immobilization led to a more rigid enzyme structure, potentially contributing to its improved stability. The removal of ciprofloxacin from MWWE by laccase@Ni₃(PO₄)₂·HNFs/p-coumaric acid oxidation system was optimized using a Box-Behnken design. Under the optimized conditions [initial laccase activity (0.05 U mL^-1), the concentration of p-coumaric acid (2.9 mM), and treatment time (4.9 h)], the biocatalyst removed 90 % of ciprofloxacin (10 mg L^-1) from MWWE. The toxicity of ciprofloxacin against some G⁺ and G^- bacteria was reduced by 35-70 %, depending on their strain. The EC₅₀ of ciprofloxacin for the alga Raphidocelis subcapitata reduced from 3.08 to 1.07 mg L^-1 (p-value <0.05) after the bioremoval. Also, the acute and chronic toxicity of identified biodegradation products was lower than ciprofloxacin at three trophic levels, as predicted by ECOSAR software.

Practical and Rapid Membrane-Based Biosensor for Phenol Using Copper/Calcium-Enzyme Hybrid Nanoflowers

Phenol, a pollutant frequently found in chemical industries effluents, is highly toxic even in low concentrations. This study reports a green, simple, and rapid method for qualitative phenol biosensing using horseradish peroxidase (HRP) hybrid nanoflowers made with copper (Cu²⁺-hNF) or calcium (Ca²⁺-hNF) ions. The enzyme was immobilized through protein-inorganic self-assembly into hybrid structures and subsequently supported onto a polyvinylidene fluoride (PVDF) membrane. SEM, EDS, FTIR, and XRD techniques sustained the effective enzyme encapsulation into hybrid structures. The protein concentration in the structures was 0.25 mg.mL^-1 for both ions. The best temperature and pH were 60 °C and 7.4, respectively, for both hybrids and the free enzyme, suggesting that the immobilization did not affect the optimal conditions of the free HRP. Thermal stability from 25 to 70 °C and pH stability from 4.0 to 9.0 of the hybrids were also determined. Finally, using copper and calcium hybrids, both biosensors produced onto a PVDF membrane could detect phenol in concentrations ranging from 0.72 to 24.00 µmol.mL^-1 in 1 min. In contrast, control biosensors produced with free enzyme have not presented a visible color change in the same conditions. The findings suggest a promising application of the developed biosensors in functional phenol detection.

Improvement in the Environmental Stability of Haloalkane Dehalogenase with Self-Assembly Directed Nano-Hybrid with Iron Phosphate

Haloalkane dehalogenase (DhaA) catalyzes the hydrolysis of halogenated compounds through the cleavage of carbon halogen bonds. However, the low activity, poor environmental stability, and difficult recycling of free DhaA greatly increases the economic cost of practical application. Inspired by the organic–inorganic hybrid system, an iron-based hybrid nanocomposite biocatalyst FeHN@DhaA is successfully constructed to enhance its environmental tolerability. A series of characterization methods demonstrate that the synthesized enzyme–metal iron complexes exhibit granular nanostructures with good crystallinity. Under optimized conditions, the activity recovery and the effective encapsulation yield of FeHN@DhaA are 138.54% and 87.21%, respectively. Moreover, it not only exhibits excellent immobilized enzymatic properties but also reveals better tolerance to extreme acid, and is alkali compared with the free DhaA. In addition, the immobilized enzyme FeHN@DhaA can be easily recovered and has a satisfactory reusability, retaining 57.8% of relative activity after five reaction cycles. The results of this study might present an alternative immobilized DhaA-based clean biotechnology for the decontamination of organochlorine pollutants.

Instantaneous synthesis and full characterization of organic-inorganic laccase-cobalt phosphate hybrid nanoflowers

A novel approach termed the "concentrated method" was developed for the instant fabrication of laccase@Co₃(PO₄)₂•hybrid nanoflowers (HNFs). The constructed HNFs were obtained by optimizing the concentration of cobalt chloride and phosphate buffer to reach the highest activity recovery. The incorporation of 30 mM CoCl₂ and 160 mM phosphate buffer (pH 7.4) resulted in a fast anisotropic growth of the nanomaterials. The purposed method did not involve harsh conditions and prolonged incubation of precursors, as the most reported approaches for the synthesis of HNFs. The catalytic efficiency of the immobilized and free laccase was 460 and 400 M⁻¹S⁻¹, respectively. Also, the enzymatic activity of the prepared biocatalyst was 113% of the free enzyme (0.5 U mL⁻¹). The stability of the synthesized HNFs was enhanced by 400% at pH 6.5–9.5 and the elevated temperatures. The activity of laccase@Co₃(PO₄)₂•HNFs declined to 50% of the initial value after 10 reusability cycles, indicating successful immobilization of the enzyme. Structural studies revealed a 32% increase in the α-helix content after hybridization with cobalt phosphate, which improved the activity and stability of the immobilized laccase. Furthermore, the fabricated HNFs exhibited a considerable ability to remove moxifloxacin as an emerging pollutant. The antibiotic (10 mg L⁻¹) was removed by 24% and 75% after 24 h through adsorption and biodegradation, respectively. This study introduces a new method for synthesizing HNFs, which could be used for the fabrication of efficient biocatalysts, biosensors, and adsorbents for industrial, biomedical, and environmental applications.

Nanoflowers: A New Approach of Enzyme Immobilization

Enzymes are biocatalysts known for versatility, selectivity, and brand operating conditions compared to chemical catalysts. However, there are limitations to their large-scale application, such as the high costs of enzymes and their low stability under extreme reaction conditions. Immobilization techniques can efficiently solve these problems; nevertheless, most current methods lead to a significant loss of enzymatic activity and require several steps of activation and functionalization of the supports. In this context, a new form of immobilization has been studied: forming organic-inorganic hybrids between metal phosphates as inorganic parts and enzymes as organic parts. Compared to traditional immobilization methods, the advantages of these nanomaterials are high surface area, simplicity of synthesis, high stability, and catalytic activity. The current study presents an overview of organic-inorganic hybrid nanoflowers and their applications in enzymatic catalysis.

Immobilized enzymes in inorganic hybrid nanoflowers for biocatalytic and biosensing applications

Enzyme immobilization has been accepted as a powerful technique to solve the drawbacks of free enzymes such as limited activity, stability and recyclability under harsh conditions. Different from the conventional immobilization methods, enzyme immobilization in inorganic hybrid nanoflowers was executed in a biomimetic mineralization manner with the advantages of mild reaction conditions, and thus it was beneficial to obtain ideal biocatalysts with superior characteristics. The key factors influencing the formation of enzyme-based inorganic hybrid nanoflowers were elucidated to obtain a deeper insight into the mechanism for achieving unique morphology and improved properties of immobilized enzymes. To date, immobilized enzymes in inorganic hybrid nanoflowers have been successfully applied in biocatalysis for preparing medical intermediates, biodiesel and biomedical polymers, and solving the environmental or food industrial issues such as the degradation of toxic dyes, pollutants and allergenic proteins. Moreover, they could be used in the development of various biosensors, which provide a promising platform to detect toxic substances in the environment or biomarkers associated with various diseases. We hope that this review will promote the fundamental research and wide applications of immobilized enzymes in inorganic hybrid nanoflowers for expanding biocatalysis and biosensing.

Understanding intricacies of bioinspired organic-inorganic hybrid nanoflowers: A quest to achieve enhanced biomolecules immobilization for biocatalytic, biosensing and bioremediation applications

The immobilization of biomolecules has been a subject of interest for scientists for a long time. The organic-inorganic hybrid nanoflowers are a new class of nanostructures that act as a host platform for the immobilization of such biomolecules. It provides better practical applicability to these functional biomolecules while also providing superior activity and reusability when catalysis is involved. These nanostructures have a versatile and straightforward synthesis process and also exhibit enzyme mimicking activity in many cases. However, this facile synthesis involves many intricacies that require in-depth analysis to fully attain its potential as an immobilization technique. A complete account of all the factors involving the synthesis process optimisation is essential to be studied to make it commercially viable. This paper explores all the different aspects of hybrid nanoflowers which sets them apart from the conventional immobilization techniques while also giving an overview of its wide range of applications in industries.

Immobilization of Phospholipase A1 Using a Protein-Inorganic Hybrid System

In this study, four kinds of phospholipase A1-metal (Al/Co/Cu/Mn) hybrid nanostructures were prepared for enhancing the stability of the free PLA1. The formed hybrid complexes were characterized by scanning electron microscope (SEM), Fourier infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The stability and substrate specificity of immobilized enzymes were subsequently determined. After immobilization, the temperature tolerance of PLA1–metal hybrid nanostructures was enhanced. The relative activity of PLA1–Al/Co/Cu hybrid nanostructures remained above 60% at 50 °C, while that of free enzyme was below 5%. The thermal transition temperature measured by differential scanning calorimetry (DSC) was found to increase from 65.59 °C (free enzyme) to 173.14 °C, 123.67 °C, 96.31 °C, and 114.79 °C, referring to PLA1–Cu/Co/Al/Mn hybrid nanostructures, respectively. Additionally, after a storage for fourteen days at 4 °C, the immobilized enzymes could exhibit approximately 60% of the initial activity, while the free PLA1 was inactivated after four days of storage. In brief, using Co²⁺, Cu²⁺, Al³⁺, and Mn²⁺ as the hybridization materials for immobilization could improve the catalytic properties and stability of the free PLA1, suggesting a promising method for a wider application of PLA1 in many fields such as food, cosmetics, and the pharmaceutical industry.

Evaluating the activity and stability of sonochemically produced hemoglobin-copper hybrid nanoflowers against some metallic ions, organic solvents, and inhibitors

The disadvantage of the conventional protein-inorganic hybrid nanoflower production method is the long incubation period of the synthesis method. This period is not suitable for practical industrial use. Herein, protein-inorganic hybrid nanoflowers were synthesized using hemoglobin and copper ion by fast sonication method for 10 min. The synthesized nanoflowers were characterized via scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fouirer-transform infrared spectroscopy. The activity and stability of the nanoflowers in the presence of different metal ions, organic solvents, inhibitors, and storage conditions were also evaluated by comparing with free hemoglobin. According to obtained results, the optimum pH and temperatures of both hybrid nanoflower and free hemoglobin were pH 5 and 40 °C, respectively. At all pH levels, nanoflower was more stable than free protein and it was also more stable than the free hemoglobin at temperatures ranging between 50 °C and 80 °C. The free protein lost more than half of its activity in the presence of acetone, benzene, and N,N-dimethylformamide, while the hybrid nanoflower retained more than 70% of its activity for 2 h at 40 °C. The hybrid nanoflower activity was essentially increased in the presence of Ca²⁺, Zn²⁺, Fe²⁺, Cu²⁺ and Ni²⁺ (132%, 161%, 175%, 185% and 106%, respectively) at 5 mM concentration. The nanoflower retained more than 85% of its initial activity in the presence of all inhibitors. In addition, it retained all its activity for 3 days under different storage conditions, unlike free hemoglobin. The results demonstrated that new hybrid nanoflowers may be promising in different biotechnological applications such as catalytic biosensors and environmental or industrial catalytic processes.

Enzyme-Loaded Flower-Shaped Nanomaterials: A Versatile Platform with Biosensing, Biocatalytic, and Environmental Promise

As a result of their unique structural and multifunctional characteristics, organic-inorganic hybrid nanoflowers (hNFs), a newly developed class of flower-like, well-structured and well-oriented materials has gained significant attention. The structural attributes along with the surface-engineered functional entities of hNFs, e.g., their size, shape, surface orientation, structural integrity, stability under reactive environments, enzyme stabilizing capability, and organic-inorganic ratio, all significantly contribute to and determine their applications. Although hNFs are still in their infancy and in the early stage of robust development, the recent hike in biotechnology at large and nanotechnology in particular is making hNFs a versatile platform for constructing enzyme-loaded/immobilized structures for different applications. For instance, detection- and sensing-based applications, environmental- and sustainability-based applications, and biocatalytic and biotransformation applications are of supreme interest. Considering the above points, herein we reviewed current advances in multifunctional hNFs, with particular emphasis on (1) critical factors, (2) different metal/non-metal-based synthesizing processes (i.e., (i) copper-based hNFs, (ii) calcium-based hNFs, (iii) manganese-based hNFs, (iv) zinc-based hNFs, (v) cobalt-based hNFs, (vi) iron-based hNFs, (vii) multi-metal-based hNFs, and (viii) non-metal-based hNFs), and (3) their applications. Moreover, the interfacial mechanism involved in hNF development is also discussed considering the following three critical points: (1) the combination of metal ions and organic matter, (2) petal formation, and (3) the generation of hNFs. In summary, the literature given herein could be used to engineer hNFs for multipurpose applications in the biosensing, biocatalysis, and other environmental sectors.

The preparation of bifunctional hybrid nano-flowers and their application in the enzyme-linked immunosorbent assay for Helicobacter pylori detection

As the infection by Helicobacter pylori (H. pylori, HP) remains for a lifetime and may induce diseases such as gastric cancer, it is vital to detect and diagnose it. A new non-invasive indirect enzyme-linked immunosorbent assay (iELISA) method based on nano-flowers (NFs) is very advantageous for the sensitive detection of HP. Furthermore, the established iELISA method based on the organic-inorganic bifunctional hybrid nano-flowers including rabbit polyclonal antibody of HP labeled with peroxidase from horseradish (R-HP-Ab-HRP@Cu2+ NFs) showed linearity with HP at a concentration of 0-105 CFU mL-1 (R2 = 0.9997). Moreover, the limit of detection (LOD) reached 50 CFU mL-1, and not only was the detection sensitivity 20 times higher than that based on rabbit polyclonal antibody of HP labeled with peroxidase from horseradish (R-HP-Ab-HRP) but also the stability of R-HP-Ab-HRP in NFs was improved. In addition, the OD450 nm value was still linearly related to the concentration of HP at a range of 0-105 CFU mL-1 (R2 = 0.9952) with a LOD of 50 CFU mL-1 in an artificial saliva system. This study provided a sensitive, low-cost and convenient method for the non-invasive detection of HP.

MOF@MnO2nanocomposites prepared usingin situmethod and recyclable cholesterol oxidase-inorganic hybrid nanoflowers for cholesterol determination

In this work, through thein situgrowth of MnO₂nanosheets on the surface of terbium metal-organic frameworks (Tb-MOFs), MOF@MnO₂nanocomposites are prepared and the fluorescence of Tb-MOFs is quenched significantly by MnO₂. Additionally, the hybrid nanoflowers are self-assembled by cholesterol oxidase (ChOx) and copper phosphate (Cu₃(PO₄)₂·3H₂O). Then a new strategy for cholesterol determination is developed based on MOF@MnO₂nanocomposites and hybrid nanoflowers. Cholesterol is oxidized under the catalysis of hybrid nanoflowers to yield H₂O₂, which further reduces MnO₂nanosheets into Mn²⁺. Hence, the fluorescence recovery of Tb-MOFs is positively correlated to the concentration of cholesterol in the range of 10 to 360μM. The limit of detection (LOD) of cholesterol is 1.57μM. On the other hand, the hierarchical and confined structure of ChOx-inorganic hybrid nanoflowers greatly improve the stability of the enzyme. The activity of hybrid nanoflowers remains at a high level for one week when stored at room temperature. Moreover, the hybrid nanoflowers can be collected by centrifugation and reused. The activity of hybrid nanoflowers can continue at a high level for five cycles of determination. Therefore, it can be concluded that the hybrid nanoflowers are more stable and more economic than free enzymes, and they show a similar sensitivity and specificity to cholesterol compared with free ChOx. Finally, this strategy has been further validated for the determination of cholesterol in serum samples with satisfactory recoveries.

Preparation of efficient, stable, and reusable copper-phosphotriesterase hybrid nanoflowers for biodegradation of organophosphorus pesticides

Phosphotriesterase (PTE) is considered to be a good biodegradation agent for organophosphorus pesticides. However, the instability of the free PTE limits its application. In this study, the free PTE was hybridized with copper ions (Cu²⁺) to enhance its catalytic stability and activity. The acquired particles were freeze-dried after precipitation with PO₄^3- at 4 °C for 72 h. Scanning electron microscopy showed that the Cu-PTE complexes formed flower-like nanoparticles after hybridization. The characteristic peaks of both the enzyme and metal material were revealed by Fourier transform-infrared spectroscopy. X-ray diffraction analysis indicated that PTE was encapsulated in the Cu₃(PO₄)₂·3H₂O based hybrid nanoflowers. Compared with free PTE, the catalytic activity of Cu-PTE hybrid nanoflowers was significantly increased about 2.2 fold. The catalytic efficiency (k_cat/V_max) of Cu-PTE hybrid nanoflowers was 1.76 fold than that of free PTE. The stability of the immobilized PTE under thermal and pH conditions was improved and the tolerance of it to organic solvents was also enhanced. Moreover, the Cu-PTE hybrid nanoflowers still exhibited 72.3 % relative activity after ten consecutive reactions. In general, this is the first time to use copper based hybrid nanoflowers to immobilize PTE, and the immobilized enzyme shows excellent performance on OPs degradation. The Cu-PTE hybrid nanoflowers may have great potential in the biodegradation of organophosphorus compounds in future.

Promote the expression and corrected folding of an extremely stable N-demethylase by promoter reconstruction, native environment simulation and surface design

Thermomicrobium roseum sarcosine oxidase (TrSOX) was a N-demethylase with specific substrate chiral selectivity, outstanding thermostability and environmental resistance. To promote the expression of TrSOX in Bacillus subtilis W600, the HpaII promoter of pMA5 plasmid was replaced by constitutive or inducible promoters. Through orthogonal experiment, the expression process was optimized, B. subtilis W600 cells containing pMA5-Pxyl-trSOX plasmid were cultivated until OD_600nm reached 2.0 and were then induced with 1.6% xylose at 37 °C for 2 h, and the native environment of T. roseum was simulated by heating at 80 °C, with the productivity of TrSOX increased from ~8.3 to ~66.7 μg/g wet cells; and the simulated high temperature was the key switch for the final folding. To reduce the surface hydrophobicity, a S320R mutant was built to form a hydrophilic lid around the entrance of the substrate pocket, and the yield of TrSOX (S320R) was ~163.0 μg/g wet cells, approximately 20 folds as that in the initial expression system. This mutant revealed the similar secondary structure, stability, resistance, chiral substrate selectivity and optimal reaction environment with wild type TrSOX; however, the N-demethylation activities for amino acid derivative substrates were dramatically increased, while those for hydrophobic non-amino acid compounds were repressed.

Preparation of a Copper Polyphosphate Kinase Hybrid Nanoflower and Its Application in ADP Regeneration from AMP

In this research article, we reported a self-assembly approach to prepare a copper polyphosphate kinase 2 hybrid nanoflower and established a cofactor ADP regeneration system from AMP using the nanoflower. First, the structure of the hybrid nanoflower was confirmed by scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, which indicated the successful loading of the enzyme in the hybrid nanoflower. Moreover, compared to the free enzyme, the hybrid nanoflower exhibited a better performance in ADP production and possessed wider catalytic pH and temperature ranges as well as improved storage stability. The hybrid nanoflower also exhibited well reusability, preserving 71.7% of initial activity after being used for ten cycles. In addition, the phosphorylation of glucose was conducted by utilizing ADP-dependent glucokinase coupled with the ADP regeneration system, in which the hybrid nanoflower was used for regenerating ADP from AMP. It was observed that the ADP regeneration system operated effectively at a very small amount of AMP. Thus, the hybrid nanoflower had great application potential in industrial catalytic processes that were coupled with ADP-dependent enzymes.

Bioleaching of copper from large printed circuit boards for synthesis of organic-inorganic hybrid

The present study described a process for copper (Cu) bioleaching from waste printed circuit boards (PCBs). The 45 (± 0.18) mg/g Cu was found in waste PCBs. Acidiphilium acidophilum (NCIM 5344) (A. acidophilum) and hydrogen peroxide (H₂O₂) were used for two-step Cu bioleaching. A. acidophilum showed growth in 9K medium containing glucose and sulfur. During the growth the bacteria decreased medium pH from 3.5 (± 0.01) to 1.0 (± 0.02) in 10 days. The results showed that it required 2.5 h to leach all of the Cu from single PCB piece using 60 mL culture supernatant + 15 mL H₂O₂ at 60 °C temperature and static condition. The leached Cu was further used to synthesize the organic-inorganic hybrid (OIH). For this study, egg white was used as a polyphenol oxidase (PPO) enzyme source. The morphological, elemental, and structural analysis was carried out using scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). Further the PPO enzyme activity was tested in OIH and crude enzyme (egg white). The egg white showed 0.00014 (± 0.00001) U/mg/min PPO activity while OIH showed 0.005 (± 0.00016) U/mg/min PPO activity. The pH 7 and 30 °C temperature were found to be optimum for PPO enzyme activity. The OIH was applied for phenol degradation. It degraded 95 (± 0.49)% of phenol (5 mM). The efficiency of phenol degradation decreased with an increase in phenol concentration.

Development of Effective Lipase-Hybrid Nanoflowers Enriched with Carbon and Magnetic Nanomaterials for Biocatalytic Transformations

In the present study, hybrid nanoflowers (HNFs) based on copper (II) or manganese (II) ions were prepared by a simple method and used as nanosupports for the development of effective nanobiocatalysts through the immobilization of lipase B from Pseudozyma antarctica. The hybrid nanobiocatalysts were characterized by various techniques including scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray diffraction (XRD), Raman spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The effect of the addition of carbon-based nanomaterials, namely graphene oxide and carbon nanotubes, as well as magnetic nanoparticles such as maghemite, on the structure, catalytic activity, and operational stability of the hybrid nanobiocatalysts was also investigated. In all cases, the addition of nanomaterials during the preparation of HNFs increased the catalytic activity and the operational stability of the immobilized biocatalyst. Lipase-based magnetic nanoflowers were effectively applied for the synthesis of tyrosol esters in non-aqueous media, such as organic solvents, ionic liquids, and environmental friendly deep eutectic solvents. In such media, the immobilized lipase preserved almost 100% of its initial activity after eight successive catalytic cycles, indicating that these hybrid magnetic nanoflowers can be applied for the development of efficient nanobiocatalytic systems.