The increasing relevance of cascade reactions in biocatalysis has sparked a great interest for enzyme co-immobilization. Enzyme co-immobilization allows access to some kinetic advantages that in some ...instances are necessary to get the desired product, avoiding side-reactions. However, the kinetic effect is very relevant mainly at the initial reaction rates, while it may be less relevant in the whole reaction course, depending on the kinetic parameters of the involved enzymes. This review not only critically discusses the advantages but also the drawbacks of enzymes co-immobilization: immobilization on the same support and surface, under similar conditions, discarding the whole biocatalyst when one of the co-immobilized enzymes is inactivated. We will discuss when co-immobilization is almost compulsory, when the advantages of co-immobilization may not be enough to compensate their problems and when it should be fully discarded. The co-immobilization of cofactors and enzymes bears special interest, as this can open up the opportunity to the building of artificial cells and extremely complex one-pot transformations. Finally, some recent strategies to overcome some the co-immobilization problems will be presented.
•Enzyme co-immobilization raises many problems in biocatalysts design.•Enzyme co-immobilization has some kinetic advantages regarding initial rates.•Enzyme co-immobilization is, in certain cases, necessary.•Co-immobilization of enzymes and cofactors opens up the possibility of building “synthetic cells”.•Some strategies have been developed to solve the problems of enzymes co-immobilization.
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•The immobilization process improves the enzyme stability, reusability, and efficiency.•The immobilization methods and immobilized carriers for laccases are summarized.•The pollutant ...removal mechanisms by immobilized laccases and influencing factors are reviewed.•The relationship among adsorption, enzymatic and pollutant removal are analyzed.•The application of immobilized laccases for water treatment in recent years is showed.
Laccase is a promising biocatalyst for micro-pollutants removal and water purification. However, laccase can only play its significant catalytic role after effective immobilization. The immobilization process improves the laccase stability, in terms of thermal, pH, storage and operation. Furthermore, the reusability of immobilized laccase makes it more advantageous in the practical applications of water purification, in comparison with free laccase. The laccase immobilization is a promising water purification technology. In this review, the immobilization methods and immobilized carriers are summarized. Then, the pollutant removal mechanism by immobilized laccases, and its influencing factors are reviewed. Afterwards, the relationship among carrier adsorption, enzymatic degradation and pollutant removal efficiency are analyzed. Finally, the application of immobilized laccase for water purification in recent years is demonstrated. This review is expected to provide a valuable guideline for enzymatic water purification.
•Enzymatic transesterification process is less energy intensive and robust.•Nano-materials are promising immobilization supports for lipase.•Packed-bed reactors are appropriate for scale-up ...use.•Potential recombinant, whole cell and recombinant whole cell lipases were enlisted.•Genetic engineering is a promising prospect in biodiesel area.
The world demand for fuel as energy sources have arisen the need for generating alternatives such as biofuel. Biodiesel is a renewable fuel used particularly in diesel engines. Currently, biodiesel is mainly produced through transesterification reactions catalyzed by chemical catalysts, which produces higher fatty acid alkyl esters in shorter reaction time. Although extensive investigations on enzymatic transesterification by downstream processing were carried out, enzymatic transesterification has yet to be used in scale-up since commercial lipases are chiefly limited to the cost as well as long reaction time. While numerous lipases were studied and proven to have the high catalytic capacity, still enzymatic reaction requires more investigation. To fill this gap, finding optimal conditions for the reaction such as alcohol and oil choice, water content, reaction time and temperature through proper reaction modelling and simulations as well as the appropriate design and use of reactors for large scale production are crucial issues that need to be accurately addressed. Furthermore, lipase concentration, alternative lipase resources through whole cell technology and genetic engineering, recent immobilizing materials including nanoparticles, and the capacity of enzyme to be reused are important criteria to be neatly investigated. The present work reviews the current biodiesel feedstock, catalysis, general and novel immobilizing materials, bioreactors for enzymatic transesterification, potential lipase resources, intensification technics, and process modelling for enzymatic transesterification.
The crosslink‐enhanced emission effect was first proposed to explore the strong luminescence of nonconjugated polymer dots possessing only either non‐emissive or weakly emissive sub‐luminophores. ...Interesting phenomena in recent research indicate such enhancement caused by extensive crosslinking appears in diverse luminescent polymers with sub‐luminophores (electron‐rich heteroatomic moieties) or luminophores (conjugated π domains). This enhancement can promote the emission from nonluminous to luminous, from weakly luminous to strongly luminous, and even convert the pathway of radiative transitions. The concept of the crosslink‐enhanced emission effect should be updated and extended to an in‐depth spatial effect, such as electron overlap and energy splitting in confined domains by effective crosslinking, more than initial immobilization. This Minireview outlines the development of the crosslink‐enhanced emission effect from the perspective of the detailed classification, inherent mechanism and applicable systems. An outlook on the further exploration and application of this theory are also proposed.
Strong links: Polymers containing luminophores or sub‐luminophores may display enhanced emission upon crosslinking by covalent, supramolecular, and ionic bonding, and by through‐space interactions in confined domains. In this Minireview the theoretical background is discussed and numerous examples are provided, which may guide researchers in crosslinkage techniques to improve luminescent systems.
In the past 35 years, DNA nanotechnology has grown to a highly innovative and vibrant field of research at the interface of chemistry, materials science, biotechnology, and nanotechnology. Herein, a ...short summary of the state of research in various subdisciplines of DNA nanotechnology, ranging from pure “structural DNA nanotechnology” over protein–DNA assemblies, nanoparticle‐based DNA materials, and DNA polymers to DNA surface technology is given. The survey shows that these subdisciplines are growing ever closer together and suggests that this integration is essential in order to initiate the next phase of development. With the increasing implementation of machine‐based approaches in microfluidics, robotics, and data‐driven science, DNA‐material systems will emerge that could be suitable for applications in sensor technology, photonics, as interfaces between technical systems and living organisms, or for biomimetic fabrication processes.
DNA nanotechnology is on its way to creating integrated functional systems for material research, life sciences, and high‐end technology. The current state of various subdisciplines of DNA nanotechnology is summarized, ranging from “structural DNA nanotechnology” over protein‐ and nanoparticle‐modified DNA assemblies, to DNA polymers and DNA surface technology, respectively.
Enzyme immobilization is an established method for the enhancement of enzyme stability and reusability, two factors that are of great importance for industrial biocatalytic applications. ...Immobilization can be achieved by different methods and on a variety of carrier materials, both organic and inorganic. Inorganic materials provide the advantage of high stability and long service life which, together with the prolonged service life of the immobilized enzyme, can benefit the process economy. However, enzyme immobilization and increased stability often come at the cost of decreased enzyme activity. The main challenges involved in the design of an efficient immobilized enzyme system is to obtain both retention of high enzyme activity, enhanced stability and reusability, which is a complicated task, given the many variables involved, and the large numbers of methods and materials available. Simultaneously, new carrier materials and morphologies are constantly being developed. An investigation of enzyme immobilization systems on inorganic materials, with special emphasis on inorganic membranes, has been conducted in order to evaluate the effects of the immobilization system on the enzyme properties upon immobilization, i.e., activity, stability and reusability. The material properties of the enzyme carriers (particles and membranes) and their effects on the success of immobilization are described here. Furthermore, the reuse of inorganic membranes as enzyme carriers has been investigated and the reported examples show high ability of regeneration. To the best of our knowledge, this is the first review on enzyme immobilization focusing on the three fundamental aspects to consider when dealing with the topic: catalytic properties, enzyme leakage and reusability. Abbreviations: β‐Gal: β‐d‐galactosidase; ADH: alcohol dehydrogenase; AFM: atomic force microscopy; APTES: 3‐aminopropyltriethoxysilane; APTMS: 3‐aminopropyltrimethoxysilane; BPA: bisphenol A; BSA: bovine serum albumin; CA: carbonic anhydrase; CALB: Candida antartica lipase B; CD: circular dichroism; CDI: carbonyldiimidazole; CLEA: cross‐linked enzyme aggregates; CLSM: confocal laser scanning microscopy; CNT: carbon nanotube; CPG: controlled pore glass; CRL: Candida rugosa lipase; DMeDMOS: dimethyldimethoxysilane; DRIFT: diffuse reflectance Fourier transform infrared; E2: 17β‐estradiol; EDC: N‐(3‐dimethylaminopropyl)‐N′‐ethylcarbodiimide hydrochloride; EDS: electron dispersive spectroscopy; FDH: formate dehydrogenase; FESEM: field emission scanning microscopy; FT‐IR: Fourier transform infrared spectroscopy; GA: glutaraldehyde; GCSZn: coal fly ashes glass‐ceramic zinc sulfate; GOD: glucose oxidase; GPS: 3‐(glycidyloxypropyl)trimethoxysilane; HDMI: hexamethylene diisocyanate; HRP: horseradish peroxidase; IEP: isoelectric point; IPTES: (3‐isocyanatopropyl)triethoxysilane; IR: infrared spectroscopy; LbL: layer‐by‐layer: MCP: metallic ceramic powder; MeTEOS: methyltriethoxysilane; MF: microfiltration; MML: Mucor miehei lipase; MNP: magnetic nanoparticle; MPTMS: 3‐mercaptopropyltrimethoxysilane; NHS: N‐hydroxysuccinimidyl; PAH: poly(allylamine hydrochloride); PEI: polyethyleneimine; PEG: polyethylene glycol; PES: polyether sulfone; PM‐IRRAS: polarization modulation infrared reflection absorption spectroscopy; pNPA: para‐nitrophenyl acetate; pNPP: para‐nitrophenyl palmitate; PSS: polystyrene sulfonate; PTMS: phenyltrimethoxysilane; ROL: Rhizopus oryzae lipase; SCAD: Saccharomyces cerevisiae alcohol dehydrogenase; SDS: sodium dodecyl sulfate; SDS‐2: sodium dodecyl sulfonate; SEM: scanning electron microscopy; TEM: transmission electron microscopy; TEOS: tetraethoxysilane; TGA: thermogravimetric analysis; TLL: Thermomyces lanuginosa lipase; TMP: transmembrane pressure; TTIP: titanium tetraisoproxide; TVL: Trametes versicolor laccase; UF: ultrafiltration; VTMS: vinyltrimethylsilane
Three‐dimensional metal carbide MXene/reduced graphene oxide hybrid nanosheets are prepared and applied as a cathode host material for lithium–sulfur batteries. The composite cathodes are obtained ...through a facile and effective two‐step liquid‐phase impregnation method. Owing to the unique 3 D layer structure and functional 2 D surfaces of MXene and reduced graphene oxide nanosheets for effective trapping of sulfur and lithium polysulfides, the MXene/reduced graphene oxide/sulfur composite cathodes deliver a high initial capacity of 1144.2 mAh g−1 at 0.5 C and a high level of capacity retention of 878.4 mAh g−1 after 300 cycles. It is demonstrated that hybrid metal carbide MXene/reduced graphene oxide nanosheets could be a promising cathode host material for lithium–sulfur batteries.
Composite cathodes: Metal carbide MXene/reduced graphene oxide hybrid nanosheets are applied as cathode host materials for lithium–sulfur batteries. With their unique 3 D layer structure and functional 2 D surfaces for the effective trapping of sulfur and lithium polysulfides, the composite cathodes deliver a high initial capacity (1144.2 mAh g−1 at 0.5 C) and excellent capacity retention (878.4 mAh g−1 after 300 cycles), so are promising candidates for application in lithium–sulfur batteries (see figure).
The use of enzymes in industrial processes requires the improvement of their features in many instances. Enzyme immobilization, a requirement to facilitate the recovery and reuse of these ...water-soluble catalysts, is one of the tools that researchers may utilize to improve many of their properties. This review is focused on how enzyme immobilization may improve enzyme stability. Starting from the stabilization effects that an enzyme may experience by the mere fact of being inside a solid particle, we detail other possibilities to stabilize enzymes: generation of favorable enzyme environments, prevention of enzyme subunit dissociation in multimeric enzymes, generation of more stable enzyme conformations, or enzyme rigidification via multipoint covalent attachment. In this last point, we will discuss the features of an “ideal” immobilization protocol to maximize the intensity of the enzyme-support interactions. The most interesting active groups in the support (glutaraldehyde, epoxide, glyoxyl and vinyl sulfone) will be also presented, discussing their main properties and uses. Some instances in which the number of enzyme-support bonds is not directly related to a higher stabilization will be also presented. Finally, the possibility of coupling site-directed mutagenesis or chemical modification to get a more intense multipoint covalent immobilization will be discussed.
•Enzyme immobilization in a porous structure may protect the enzyme from some inactivating causes•Enzyme immobilization may freeze some stable enzyme conformation•Multi-subunit enzyme immobilization may prevent enzyme subunit dissociation•Enzyme immobilization may enhance enzyme stability by generating special environments•Enzyme multipoint covalent attachment should increase enzyme rigidity
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SDS-nClAP was synthesized using SDS within 40.4nm.The SDS-nClAP could effectively transform Pb labile Pb to stable fraction with a maximum increase of 38.3%.The SDS-nClAP could ...reduce the TCLP-leachable Pb from 0.30 to 0mg/L after 45-d treatment.Dissolution-precipitation process may be the main mechanism.
During the past years, efforts have been made to deal with the Pb contaminated sediment in Xiawangang River in Hunan province, China, but it remains a serious problem since the smelting pollutants were accumulated. According to previous studies, phosphate showed an effective ability to transfer labile Pb to pyromorphite (Pb5(PO4)3X, X=F, Cl, Br, OH) but its application was limited by its solubility and deliverability. Hence a new class of nano-chlorapatite was synthesized by using sodium dodecyl sulfate (SDS) as a stabilizer and characterized by TEM, FESEM, DLS, FTIR, and EDAX. Results demonstrated that the SDS stabilized nano-chlorapatite (SDS-nClAP) was in spherical or spheroidal shape with a hydrodynamic diameter of 40.4nm. Experimental data suggested that SDS-nClAP was effective in transforming labile Pb to stable fraction with a maximum increase of 38.3%, also the reduction of TCLP-leachable Pb from 0.30 to 0mg/L after 45-d treatment. The increase of available phosphorus in both SDS-nClAP and ClAP treated sediment samples verified dissolution-precipitation mechanism involved in Pb immobilization. Additionally, the increment of organic matter in 10:1 treated samples was approximately 5-fold than that in 2:1 treated samples, which revealed that the micro-organisms may play an important role in it.
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