Nanomaterials Supported Enzymes: Environmental Applications for Depollution of Aquatic Environments

WARNING : The light-emitting molecular structures responsible for the chemiluminescence and fluorescence phenomena are not necessarily the same!

Recently, development of smart materials for immobilization of enzyme draws a significant attention in frontier research due to their applications in a wide range of catalytic reactions in several industries. Although numerous supports have already been developed in the past years for enzyme immobilization, challenges still exist to design a material with superior enticing properties like green synthesis approach, high enzyme loading and efficient immobilization process. Here, we have reported an efficient method to immobilize Candida rugosa lipase (CRL) in Zn‐(NH 2 ‐BDC) metal‐organic frameworks (MOFs) via physical adsorption. The main objective of this work is to develop a material for enzyme immobilization that can immobilize enzyme during the synthesis of support. Here, a single step procedure offers both the synthesis of support and enzyme immobilization process. After successful immobilization, it is observed from the systematic characterization that the CRL is loaded 280 mg/g of Zn‐(NH 2 ‐BDC) MOFs during the crystal growth. The immobilized CRL demonstrates promising stability and catalytic activity in the ester hydrolysis. Most importantly, the immobilized CRL retains 79% of its initial activities after 10 times reuse. Our study highlights to develop an elegant material for effective enzyme immobilization.

Thiol Treatment Creates Selective Palladium Catalysts for Semihydrogenation of Internal Alkynes

Molecular catalysts are attracting interest as drivers of redox reactions for sustainable applications. Through systematic molecular design, they could be engineered to have high selectivity and activity towards a multitude of catalytic reactions. However, as long as they are used in homogeneous setups, they will suffer from inconvenient energy supply, inefficient charge transport and difficulty in separation from reaction products. To be relevant for industrial applications, molecular catalysts must be bound to solid materials in direct contact with the energy source. In this regard, conducting polymers are particularly interesting, as they provide a straightforward means of both surface immobilization and charge transport. In this work, we synthesize and characterize three different metalloporphyrin-functionalized conducting polymers and apply them to catalysis of the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR). We show that incorporation of porphyrins into conducting polymers is a reliable immobilization method, that the properties of both the porphyrin units and the polymer backbone are preserved in all systems, and that the polymers provide efficient charge transport to and from the catalytic centers. Nevertheless, we also find that the polymers are negatively affected by intermediates formed during the HER and the ORR. We conclude that the choice of immobilization method has a large impact on the quality of the molecular catalyst, and that the effect of the catalytic cycle on the immobilization matrix must be considered in the molecular design process.

Immobilization process is to optimize the operational performance of an enzyme for industrial applications.So far different matrices have been described in the literature to improve the performance of the immobilized enzymes.With the advent of nanotechnology, the nanomaterials because of their unique physico-chemical properties constitute novel and interesting matrices for enzyme immobilization.The nanomaterials possess ideal characteristics to equilibrate principal factors which determine biocatalysts efficiency, including specific surface area, mass transfer resistance and effective enzyme loading.This review presents the current scenario and techniques in enzyme immobilization.An overview of the main methods used to combine proteins/enzymes with nanoparticles is given in the study.The advantages and disadvantages of nanoparticles as immobilization matrix are also discussed.

BackgroundImmobilization of enzymes onto different carriers increases enzyme’s stability and reusability within biotechnological and pharmaceutical applications. However, some immobilization techniques are associated with loss of enzymatic specificity and/or activity. Possible reasons for this loss are mass transport limitations or structural changes. For this reason an immobilization method must be selected depending on immobilisate’s demands. In this work different immobilization media were compared towards the synthetic and hydrolytic activities of immobilized trypsin as model enzyme on magnetic micro-particles.ResultsPorcine trypsin immobilization was carried out in organic and aqueous media with magnetic microparticles. The immobilization conditions in organic solvent were optimized for a peptide synthesis reaction. The highest carrier activity was achieved at 1 % of water (v/v) in dioxane. The resulting immobilizate could be used over ten cycles with activity retention of 90 % in peptide synthesis reaction in 80 % (v/v) ethanol and in hydrolysis reaction with activity retention of 87 % in buffered aqueous solution. Further, the optimized method was applied in peptide synthesis and hydrolysis reactions in comparison to an aqueous immobilization method varying the protein input. The dioxane immobilization method showed a higher activity coupling yield by factor 2 in peptide synthesis with a maximum activity coupling yield of 19.2 % compared to aqueous immobilization. The hydrolysis activity coupling yield displayed a maximum value of 20.4 % in dioxane immobilization method while the aqueous method achieved a maximum value of 38.5 %. Comparing the specific activity yields of the tested immobilization methods revealed maximum values of 5.2 % and 100 % in peptide synthesis and 33.3 % and 87.5 % in hydrolysis reaction for the dioxane and aqueous method, respectively.ConclusionsBy immobilizing trypsin in dioxane, a beneficial effect on the synthetic trypsin activity resilience compared to aqueous immobilization medium was shown. The results indicate a substantial potential of the micro-aqueous organic protease immobilization method for preservation of enzymatic activity during enzyme coupling step. These results may be of substantial interest for enzymatic peptide synthesis reactions at mild conditions with high selectivity in industrial drug production.

The overlapping network of kinase-substrate interactions provides exquisite specificity in cell signaling pathways, but also presents challenges to our ability to understand the mechanistic basis of biological processes. Efforts to dissect kinase-substrate interactions have been particularly limited by their inherently transient nature. Here, we use a library of FRET sensors to monitor these transient complexes, specifically examining weak interactions between the catalytic domain of protein kinase Cα and 14 substrate peptides. Combining results from this assay platform with those from standard kinase activity assays yields four novel insights into the kinase-substrate interaction. First, preferential binding of non-phosphorylated versus phosphorylated substrates leads to enhanced kinase-specific activity. Second, kinase-specific activity is inversely correlated with substrate binding affinity. Third, high affinity substrates can suppress phosphorylation of their low affinity counterparts. Finally, the substrate-competitive inhibitor bisindolylmaleimide I displaces low affinity substrates more potently leading to substrate selective inhibition of kinase activity. Overall, our approach complements existing structural and biophysical approaches to provide generalizable insights into the regulation of kinase activity.

Immobilization techniques have been popularly used to preserve the operational stability of the enzymes for industrial applications. The three main components of an immobilized enzyme system are the enzyme, the matrix/support, and the technique of immobilization. So far, different supports have been developed to improve the efficiency of the immobilized enzymes. But in the recent decade, nanotechnology has been of considerable research interest in the field of immobilized enzyme carriers. The materials at the nano-scale, due to their unique physicochemical properties, including; specific surface area, mass transfer limitation, and effective enzyme loading, are considered interesting matrices for enzyme immobilization. This review describes techniques employed to immobilize enzymes, and provides an integrated focus on the most common nanoparticles for enzyme conjugation. Additionally, the pros and cons of nanoparticles as immobilization matrices are also discussed. Depending on the type of enzyme and its application, in this review, the researchers are directed to select an appropriate method and support for enzyme immobilization in terms of enzyme stability and functionality.

Obtaining a biodegradable biocatalyst – study on lipase immobilization on spent coffee grounds as potential carriers

Carbonic anhydrase (CA) was previously proposed as a green alternative for biomineralization of carbon dioxide (CO2). However, enzyme's fragile nature when in synthetic environment significantly limits such industrial application. Herein, we hypothesized that CA immobilization onto flexible and hydrated "bridges" that ensure proton-transfer at their interfaces leads to improved activity and kinetic behavior and potentially increases enzyme's feasibility for industrial implementation. Our hypothesis was formulated considering that water plays a key role in the CO2 hydration process and acts as both the reactant as well as the rate-limiting step of the CO2 capture and transformation process. To demonstrate our hypothesis, two types of user-synthesized organic metallic frameworks [metal-organic frameworks (MOFs), one hydrophilic and one hydrophobic] were considered as model supports and their surface characteristics (i.e., charge, shape, curvature, size, etc.) and influence on the immobilized enzyme's behavior were evaluated. Morphology, crystallinity and particle size, and surface area of the model supports were determined by scanning electron microscopy, dynamic light scattering, and nitrogen adsorption/desorption measurements, respectively. Enzyme activity, kinetics, and stability at the supports interfaces were determined using spectroscopical analyses. Analysis showed that enzyme functionality is dependent on the support used in the immobilization process, with the enzyme immobilized onto the hydrophilic support retaining 72% activity of the free CA, when compared with that immobilized onto the hydrophobic one that only retained about 28% activity. Both CA-MOF conjugates showed good storage stability relative to the free enzyme in solution, with CA immobilized at the hydrophilic support also revealing increased thermal stability and retention of almost all original enzyme activity even after heating treatment at 70 °C. In contrast, free CA lost almost half of its original activity when subject to the same conditions. This present work suggests that MOFs tunable hydration conditions allow high enzyme activity and stability retention. Such results are expected to impact CO2 storage and transformation strategies based on CA and potentially increase user-integration of enzyme-based green technologies in mitigating global warming.

Immobilizing and positioning patients for radiotherapy

Study on the activity and stability of urease immobilized onto nanoporous alumina membranes

Activity and stability comparison of immobilized NADH oxidase on multi-walled carbon nanotubes, carbon nanospheres, and single-walled carbon nanotubes

Immobilized lipases have received great attention in food, environment, medicine, and other fields due to their easy separation, high stability (temperature, pH), and high storage properties. After immobilization, lipase transforms from a homogeneous to a heterogeneous state, making it easier to recover from the reaction substrate and achieve recycling, which is in line with the concept of green chemistry and reduces protein contamination in the product. There are various materials for enzyme immobilization, including polysaccharides from natural sources, inorganic compounds, carbon nanotubes, metal-organic framework materials, and so forth. Magnetic immobilization carriers have been widely studied due to their ability to achieve separation by adding a magnetic field. Its immobilization method can be simply divided into two categories: physical action (adsorption, embedding) and chemical binding (covalent, cross-linking). Some studies mainly discuss the immobilization support materials, immobilization methods, and applications of immobilized lipases in food. On this basis, our review also focuses on the changes in crosslinking agents for immobilized lipases, different methods to promote immobilization, new trends in the study of immobilized lipases, and proposes prospects for immobilized lipase research in the food industry.

Biofiltration – the treatment of fluids by microorganisms immobilized into the filter bedding material: a review