In recent years, enzyme immobilization has been presented as a powerful tool for the improvement of enzyme properties such as stability and reusability. However, the type of support material used ...plays a crucial role in the immobilization process due to the strong effect of these materials on the properties of the produced catalytic system. A large variety of inorganic and organic as well as hybrid and composite materials may be used as stable and efficient supports for biocatalysts. This review provides a general overview of the characteristics and properties of the materials applied for enzyme immobilization. For the purposes of this literature study, support materials are divided into two main groups, called Classic and New materials. The review will be useful in selection of appropriate support materials with tailored properties for the production of highly effective biocatalytic systems for use in various processes.
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•Citric acid functionalized micro-biochars showed enhanced laccase loading.•Covalent immobilization: improved pH, thermal, storage and operational stability.•Citric acid pretreatment ...increased laccase binding up to 20%.•Laccase immobilized micro-biochars nearly removed 100% diclofenac.•About 40% activity was retained even after 5 cycles of applications.
Immobilization of enzymes on the solid supports can improve the stability as well as catalytic properties of enzymes. In this study, biochar derived from various feedstocks were used as immobilization support considering biochars carbon negative as well as sustainable properties. Partially purified (concentrated) crude laccase was covalently immobilized onto pine wood (BC-PW), pig manure (BC-PM) and almond shell (BC-AS) micro-biochars using optimized 5% w/v glutaraldehyde. Moreover, citric acid pretreatment improved the laccase binding capacity of all the micro-biochars and the highest laccase binding of 40.2 ± 1.8 U g−1 was observed with BC-PM in comparison with raw BC-PM (34.1 ± 1.1 U g−1). The enhanced binding of laccase on BC-PM over wood derived biochars was attributed to the higher surface area (46.1 m2 g−1) of BC-PM. Moreover, feedstock selection as well as a method of production influenced the biochar physicochemical properties such as surface area and consequently, different biochars showed various laccase immobilization efficiencies. BC-PW showed better pH, thermal, storage, and operational stability, compared with BC-AS and BC-PM. While applying the laccase bound micro-biochar, complete removal was observed in 2 h under batch mode with 0.5 g of laccase bound BC-PM at an environmentally relevant concentration of 500 µg L−1 in wastewater effluent. About 40% of the laccase activity was retained with all the laccase-bound micro-biochars after 5 cycles of diclofenac treatment.
Lipases are the most widely used enzymes in biocatalysis, and the most utilized method for enzyme immobilization is using hydrophobic supports at low ionic strength. This method allows the one step ...immobilization, purification, stabilization, and hyperactivation of lipases, and that is the main cause of their popularity. This review focuses on these lipase immobilization supports. First, the advantages of these supports for lipase immobilization will be presented and the likeliest immobilization mechanism (interfacial activation on the support surface) will be revised. Then, its main shortcoming will be discussed: enzyme desorption under certain conditions (such as high temperature, presence of cosolvents or detergent molecules). Methods to overcome this problem include physical or chemical crosslinking of the immobilized enzyme molecules or using heterofunctional supports. Thus, supports containing hydrophobic acyl chain plus epoxy, glutaraldehyde, ionic, vinylsulfone or glyoxyl groups have been designed. This prevents enzyme desorption and improved enzyme stability, but it may have some limitations, that will be discussed and some additional solutions will be proposed (e.g., chemical amination of the enzyme to have a full covalent enzyme-support reaction). These immobilized lipases may be subject to unfolding and refolding strategies to reactivate inactivated enzymes. Finally, these biocatalysts have been used in new strategies for enzyme coimmobilization, where the most stable enzyme could be reutilized after desorption of the least stable one after its inactivation.
•Lipases immobilization on hydrophobic supports via interfacial activation is described in this review•This protocol permits the one step immobilization, purification, stabilization and hyperactivation of lipases•Lipases may be released from the support under certain conditions•Intermolecular crosslinking may prevent enzyme release•Heterofunctional supports prevent enzyme release but they have some limitations•There are many ways of taking full advantage of the new heterofunctional supports
Lithium–sulfur (Li–S) batteries are deemed as one of the most promising next-generation energy storage systems. However, their practical application is hindered by existing drawbacks such as poor ...cycling life and low Coulombic efficiency due to the shuttle effect of lithium polysulfides (LiPSs). We herein present an in situ constructed VO2–VN binary host which combines the merits of ultrafast anchoring (VO2) with electronic conducting (VN) to accomplish smooth immobilization–diffusion–conversion of LiPSs. Such synchronous advantages have effectively alleviated the polysulfide shuttling, promoted the redox kinetics, and hence improved the electrochemical performance of Li–S batteries. As a result, the sulfur cathode based on the VO2–VN/graphene host exhibited an impressive rate capability with ∼1105 and 935 mA h g−1 at 1C and 2C, respectively, and maintained long-term cyclability with a low capacity decay of 0.06% per cycle within 800 cycles at 2C. More remarkably, favorable cyclic stability can be attained with a high sulfur loading (13.2 mg cm−2). Even at an elevated temperature (50 °C), the cathodes still delivered superior rate capacity. Our work emphasizes the importance of immobilization–diffusion–conversion of LiPSs toward the rational design of high-load and long-life Li–S batteries.
Enzyme immobilization is essential to the commercial viability of various critical large‐scale biocatalytic processes. However, challenges remain for the immobilization systems, such as difficulties ...in loading large enzymes, enzyme leaching, and limitations for large‐scale fabrication. Herein, we describe a green and scalable strategy to prepare high‐performance biocatalysts through in situ assembly of enzymes with covalent organic frameworks (COFs) under ambient conditions (aqueous solution and room temperature). The obtained biocatalysts have exceptional reusability and stability and serve as efficient biocatalysts for important industrial reactions that cannot be efficiently catalyzed by free enzymes or traditional enzyme immobilization systems. Notably, this versatile enzyme immobilization platform is applicable to various COFs and enzymes. The reactions in an aqueous solution occurred within a short timeframe (ca. 10–30 min) and could be scaled up readily (ca. 2.3 g per reaction).
In situ assembly of enzymes and covalent organic frameworks (COFs) enables the environmentally benign large‐scale fabrication of a new generation of high‐performance biocatalysts. This approach shows how limitations in enzyme immobilization can be overcome and it opens up a new avenue for the scalable fabrication of high‐performance biocatalysts to accelerate enzyme industrialization.
This tutorial review focuses on recent advances in technologies for enzyme immobilisation, enabling their cost-effective use in the bio-based economy and continuous processing in general. The ...application of enzymes, particularly in aqueous media, is generally on a single use, throw-away basis which is neither cost-effective nor compatible with a circular economy concept. This shortcoming can be overcome by immobilising the enzyme as an insoluble recyclable solid, that is as a heterogeneous catalyst.
This tutorial review focuses on recent advances in technologies for enzyme immobilisation, enabling their cost-effective use in the bio-based economy and continuous processing in general.
The discharge of chromium (Cr) contaminated wastewater is creating a serious threat to aquatic environment due to the rapid pace in agricultural and industrial activities. Particularly, the long-term ...exposure of Cr(VI) polluted wastewater to the environment is causing serious harm to human health. Therefore, the treatment of Cr(VI) contaminated wastewater is demanding widespread attention. Regarding this, the bioremediation is being considered as a reliable and feasible option to handle Cr(VI) contaminated wastewater because of having low technical investment and operating costs. However, certain factors such as loss of microorganisms, toxicity to microorganisms and uneven microbial growth cycle in the presence of high concentrations of Cr(VI) are hindering its commercial applications. Regarding this, microbial immobilization technology (MIT) is getting great research interest because it could overcome the shortcomings of bioremediation technology's poor tolerance against Cr. Therefore, this review is the first attempt to emphases recent research developments in the remediation of Cr(VI) contamination via MIT. Starting from the selection of immobilized carrier, the present review is designed to critically discuss the various microbial immobilizing methods i.e., adsorption, embedding, covalent binding and medium interception. Further, the mechanism of Cr(VI) removal by immobilized microorganism has also been explored, precisely. In addition, three kinds of microorganism immobilization devices have been critically examined. Finally, knowledge gaps/key challenges and future perspectives are also discussed that would be helpful for the experts in improving MIT for the remediation of Cr(VI) contamination.
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•Remediation of Cr(VI)-contamination via microbial immobilization technique (MIT) have been critically examined.•Applications of composite carrier and modified carrier have been discussed.•Methods of immobilization of microorganisms have been analyzed and elucidated.•Mechanism of Cr removal by immobilized microorganism has been explored from the selection of immobilized microorganism.
The enzymatic processes are increasingly highlights, especially in the synthesis of chemical products with high added value. The enzyme immobilization can improve industrial biocatalytic processes. ...The immobilization of enzymes provides the production of efficient, stable biocatalysts, possibility of reuse and easy purification of the products, when compared to the free enzymes. There is a growing research for more efficient methods of enzyme immobilization. In this context, the choice of support and immobilization strategy can significantly improve the final enzymatic properties. In this review paper, we aimed to discuss the versatility of biocatalysts immobilized enzymes design, focusing on the opportunities and disadvantages for each method presented. They discussed the recent development of enzyme immobilization methods and applications relating the final properties of the produced biocatalysts with the desired goals.
Bioethanol has been identified as the mostly used biofuel worldwide since it significantly contributes to the reduction of crude oil consumption and environmental pollution. It can be produced from ...various types of feedstocks such as sucrose, starch, lignocellulosic and algal biomass through fermentation process by microorganisms. Compared to other types of microoganisms, yeasts especially
is the common microbes employed in ethanol production due to its high ethanol productivity, high ethanol tolerance and ability of fermenting wide range of sugars. However, there are some challenges in yeast fermentation which inhibit ethanol production such as high temperature, high ethanol concentration and the ability to ferment pentose sugars. Various types of yeast strains have been used in fermentation for ethanol production including hybrid, recombinant and wild-type yeasts. Yeasts can directly ferment simple sugars into ethanol while other type of feedstocks must be converted to fermentable sugars before it can be fermented to ethanol. The common processes involves in ethanol production are pretreatment, hydrolysis and fermentation. Production of bioethanol during fermentation depends on several factors such as temperature, sugar concentration, pH, fermentation time, agitation rate, and inoculum size. The efficiency and productivity of ethanol can be enhanced by immobilizing the yeast cells. This review highlights the different types of yeast strains, fermentation process, factors affecting bioethanol production and immobilization of yeasts for better bioethanol production.
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•TiO2 nanoparticles electrosprayed and thermally fixed on PVDF-coated steel mesh.•Thermal fixation at 160°C was optimal for photocatalytic activity.•Immobilized photocatalyst ...effective for degrading organic pollutants in UV light.•High photocatalytic efficacy was retained for 20 consecutive runs.
We have developed a highly reusable photocatalyst based on TiO2 nanoparticles for degrading organic pollutants in water. The particles were immobilized on steel mesh (SM) by a three-step procedure: (1) formation of poly(vinylidene fluoride) (PVDF) binder interface by dip-coating SM (2.5cm×5.0cm), (2) electrospraying of TiO2 nanoparticles dispersed in methanol (Degussa P25, 1mg/mL), and (3) final thermal fixation with a pressure of 100MPa for improved mechanical stability. When the electrosprayed volumes were 10, 20, 30, 40, 50, and 60mL, the TiO2 loading on both sides of the PVDF-coated SM increased from 0.20, 0.43, 0.73, 0.97, 1.10, to 1.60mg respectively. The SM sample loaded with 1.10mg TiO2 (SM-TiO2) was found to be optimal for the photocatalytic oxidation of methylene blue (MB) under UV irradiation, with stable performance for 20 consecutive photocatalytic runs. The SM-TiO2 thermally fixed at 160°C exhibited higher photocatalytic efficacy than those fixed at 180 and 200°C, because at higher temperatures the melted PVDF resin layer (melting point: 165–172°C) entrapped the TiO2 nanoparticles and rendered them photocatalytically inactive. The optimized SM-TiO2 demonstrated good performance on diverse organic pollutants, namely MB, methyl orange, reactive blue 4, sulfamethoxazole, and microcystin-LR, with rate constants of 0.0251, 0.0368, 0.0164, 0.0568, and 0.0725min−1, respectively.
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