Enzymes and nanoparticles: Modulation of enzymatic activity via nanoparticles

In situ modulation of enzyme activity via heterogeneous catalysis utilizing solid electroplated cofactors

During product isolation the received bioreceptors often do not exhibit a sufficient biochemical activity due to multistep dissociation and loss of cofactors. However, for bioelectrochemical applications the presence of cofactors is necessary for a successful oxidative or reductive conversion of the substrates to the products. Herein, we show how the immobilization of the required electroplated cofactors in a design of amperometric electrodes can in situ assist the activity of apo-enzymes. Compared to conventional approaches used in enzyme engineering this tailored nanoengineering methodology is superior from economic point of view, labor and time costs, storage conditions, reduced amount of waste and can fill the gap in the development of tuned bioelectrocatalysts.

Silica-based Nanoparticles for Enzyme Immobilization and Delivery

Enzymes play an indispensable role in biosystems, catalyzing a variety of chemical and biochemical reactions with exceptionally high efficiency and selectivity. These features render them uniquely positioned in developing novel catalytic systems and therapeutics. However, their practical application is largely hindered by the vulnerability, low reusability and the inability to overcome the biological barriers of enzymes. Silica-based nanoparticles (SNPs) are a classic family of nanomaterials with tunable physicochemical properties, making them ideal candidates to address the intrinsic shortcomings of natural enzymes. SNPs not only improve the activity and durability of enzymes, but also provide precise spatiotemporal control over their intracellular as well as systemic biodistributions for boosting the catalytic outcome. Herein, the recent progress in SNPs for enzyme immobilization and delivery is summarized. The therapeutic applications, including cancer therapy and bacterial inhibition, are particularly highlighted. Our perspectives in this field, including current challenges and possible future research directions are also provided.

Recent Advances in Nattokinase-Enriched Fermented Soybean Foods: A Review

With the dramatic increase in mortality of cardiovascular diseases (CVDs) caused by thrombus, this has sparked an interest in seeking more effective thrombolytic drugs or dietary nutriments. The dietary consumption of natto, a traditional Bacillus-fermented food (BFF), can reduce the risk of CVDs. Nattokinase (NK), a natural, safe, efficient and cost-effective thrombolytic enzyme, is the most bioactive ingredient in natto. NK has progressively been considered to have potentially beneficial cardiovascular effects. Microbial synthesis is a cost-effective method of producing NK. Bacillus spp. are the main production strains. While microbial synthesis of NK has been thoroughly explored, NK yield, activity and stability are the critical restrictions. Multiple optimization strategies are an attempt to tackle the current problems to meet commercial demands. We focus on the recent advances in NK, including fermented soybean foods, production strains, optimization strategies, extraction and purification, activity maintenance, biological functions, and safety assessment of NK. In addition, this review systematically discussed the challenges and prospects of NK in actual application. Due to the continuous exploration and rapid progress of NK, NK is expected to be a natural future alternative to CVDs.

Interactions of proteins with metal-based nanoparticles from a point of view of analytical chemistry - Challenges and opportunities

Interactions of proteins with nanomaterials draw attention of many research groups interested in fundamental phenomena. However, alongside with valuable information regarding physicochemical aspects of such processes and their mechanisms, they more and more often prove to be useful from a point of view of bioanalytics. Deliberate use of processes based on adsorption of proteins on nanoparticles (or vice versa) allows for a development of new analytical methods and improvement of the existing ones. It also leads to obtaining of nanoparticles of desired properties and functionalities, which can be used as elements of analytical tools for various applications. Due to interactions with nanoparticles, proteins can also gain new functionalities or lose their interfering potential, which from perspective of bioanalytics seems to be very inviting and attractive. In the framework of this article we will discuss the bioanalytical potential of interactions of proteins with a chosen group of nanoparticles, and implementation of so driven processes for biosensing. Moreover, we will show both positive and negative (opportunities and challenges) aspects resulting from the presence of proteins in media/samples containing metal-based nanoparticles or their precursors.

Combined Probe Strategy to Increase the Enzymatic Digestion Rate and Accelerate the Renal Radioactivity Clearance of Peptide Radiotracers

High and sustained renal radioactivity accumulation is a major challenge in peptide-based radionuclide imaging and therapy. However, neutral endopeptidase (NEP)-based enzymatic hydrolysis to release and excrete the radioactive fragments has been proven to be an effective and promising way to reduce renal accumulation. Despite the improvement, the effect is still far from being satisfactory. To further reduce kidney uptake, we studied the relationship between the enzymatic reaction rate and the substrate concentration and came up with a combined probe strategy. Model compounds Boc-MVK-Dde and Boc-MFK-Dde were used for an in vitro enzymatic digestion study. NOTA-Exendin 4 and NOTA-MVK-Exendin 4 were labeled with ⁶⁴Cu for in vivo dose-dependent micro-positron emission tomography (PET) studies. Groups 1 and 2 were injected with 0.2 and 0.8 nmol of ⁶⁴Cu-NOTA-Exendin 4, respectively. Groups 3-6 were injected with 0.2, 0.8, 1.0, and 1.4 nmol of ⁶⁴Cu-NOTA-MVK-Exendin 4, respectively. Groups 7 and 8 were co-injected with 0.2 nmol of ⁶⁴Cu-NOTA-MVK-Exendin 4 and NOTA-MVK-PEG5K (1.3 and 2.6 nmol). The radioactivity uptakes were determined and compared within and among the groups. The in vitro cleavage study for both Boc-MVK-Dde and Boc-MFK-Dde indicated that within a certain concentration range, the enzyme digestion rate increased with increasing substrate concentration. The microPET images showed that the renal clearance could be accelerated significantly by increasing the injection dose of ⁶⁴Cu-NOTA-MVK-Exendin 4, with the kidney uptakes being 60.98, 43.01, and 16.10 % ID/g at 1 h for groups 3, 4 and 5, respectively. Unfortunately, the tumor uptakes were also significantly inhibited as the injected dose of the tracer increased. However, with the co-injection of NOTA-MVK-PEG5K, the renal accumulation was significantly decreased without hampering the tumor uptake. As a result, the tumor-to-kidney ratios were significantly improved, which were 1.93, 3.47, 1.74, and 3.38 times that of group 3 at 1, 4, 24, and 48 h, respectively. The enzymatic reaction rate of NEP is dependent on the concentration of the substrates both in vitro and in vivo. The combined probe strategy developed in this study can dramatically reduce the renal accumulation of a peptide radioligand without affecting the tumor uptake, which shows great potential in peptide-based radiotheranostics.

Catalytic roles, immobilization and management of recalcitrant environmental pollutants by laccases: Significance in sustainable green chemistry

We are facing a high risk of exposure to emerging contaminants and increasing environmental pollution with the concomitant growth of industries. Persistence of these pollutants is a major concern to the ecosystem. Laccases, also known as "green catalysts" are multi-copper oxidases which offers an eco-friendly solution for the degradation of these hazardous pollutants to less or non-toxic compounds. Although various other biological methods exist for the treatment of pollutants, the fact that laccases catalyze the oxidation of broad range of substrates in the presence of molecular oxygen without any additional cofactor and releases water as the by-product makes them exceptional. They have a good possibility of utilization in various industries, especially for the purpose of bioremediation. Besides this, they have also been used in medical/health care, food industry, bio-bleaching, wine stabilization, organic synthesis and biosensors. This review covers the catalytic behaviour of laccases, their immobilization strategies, potential applications in bioremediation of recalcitrant environmental pollutants and their engineering. It provides a comprehensive summary of most factors to consider while working with laccases in an industrial setting. It compares the benefits and drawbacks of the current techniques. Immobilization and mediators, two of the most significant aspects in working with laccases, have been meticulously discussed.

Immobilization of the Aspartate Ammonia-Lyase from Pseudomonas fluorescens R124 on Magnetic Nanoparticles: Characterization and Kinetics

Aspartate ammonia-lyases (AALs) catalyze the non-oxidative elimination of ammonia from l-aspartate to give fumarate and ammonia. In this work the AAL coding gene from Pseudomonas fluorescens R124 was identified, isolated, and cloned into the pET-15b expression vector and expressed in E. coli. The purified enzyme (PfAAL) showed optimal activity at pH 8.8, Michaelis-Menten kinetics in the ammonia elimination from l-aspartate, and no strong dependence on divalent metal ions for its activity. The purified PfAAL was covalently immobilized on epoxy-functionalized magnetic nanoparticles (MNP), and effective kinetics of the immobilized PfAAL-MNP was compared to the native solution form. Glycerol addition significantly enhanced the storability of PfAAL-MNP. Inhibiting effect of the growing viscosity (modulated by addition of glycerol or glucose) on the enzymatic activity was observed for the native and immobilized form of PfAAL, as previously described for other free enzymes. The storage stability and recyclability of PfAAL-MNP is promising for further biocatalytic applications.

Compositional analysis and physicochemical evaluation of date palm (Phoenix dactylifera L.) mucilage for medicinal purposes

Objectives

Date palm (Phoenix dactylifera) mucilage obtained from its dried fruits was evaluated to check the proximate composition and physicochemical properties.

Methods

Commercially available date palm mucilage was precipitated using ethanol. Both (crude and purified) mucilage samples were subjected for proximate, physiochemical, biochemical and antioxidant activity using standard experimental protocols. Elemental analysis of crude date palm mucilage was also performed using LIBS.

Results

Ethanol was used to purify the mucilage (58.4% yield). Proximate analysis was carried out on crude and purified mucilages showing crude fat, crude protein, crude fiber, total carbohydrates, nitrogen free extract and total energy in purified mucilage were more than the crude mucilage. Moisture and ash contents were found more in crude mucilage than the purified mucilage. Laser introduced breakdown spectroscopy (LIBS) detected Zn, Mg, Mn, K, Na, Cu, Fe and Ca metals as components of mucilage. Biochemical profiling indicated that crude and purified mucilage have proteins, protease, superoxide dismutase, catalase, peroxidase, amylase, ascorbate peroxidase, free amino acids, total soluble sugars, reducing sugars, non-reducing sugars, total anthocyanin, free anthocyanin, total flavonoid contents and total phenolic contents.

Conclusion

The study shows that date palm mucilage could be potentially used as pharmaceutical and medicinal ingredient due to presence of bioactive compounds and its physicochemical properties.

Nanosized porous artificial enzyme as a pH-sensitive doxorubicin delivery system for joint enzymatic and chemotherapy towards tumor treatment

A porous spherical artificial nanozyme (HF-900) prepared via pyrolysis of a porous organic polymer was used as drug carrier for efficient loading and highly selective pH-responsive delivery of doxorubicin (DOX) for the tumor joint nanotherapy.

Immobilization of GOx Enzyme on SiO2-Coated Ni-Co Ferrite Nanocomposites as Magnetic Support and Their Antimicrobial and Photocatalytic Activities

The present study used a sol-gel auto-combustion approach to make silica (SiO2)-coated Ni-Co ferrite nanocomposites that would be used as a platform for enzyme immobilization. Using glutaraldehyde as a coupling agent, glucose oxidase (GOx) was covalently immobilized on this magnetic substrate. X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), and fourier transform infrared spectroscopy (FTIR) was used to determine the structural analysis and morphology of Ni-Co ferrite/SiO2 nanocomposites. FTIR spectra confirmed the binding of GOx to Ni-Co ferrite/SiO2 nanocomposites, with a loading efficiency of around 85%. At alkaline pH and higher temperature, the immobilized GOx enzyme exhibited increased catalytic activity. After 10 times of reuses, it still had 69% catalytic activity. Overall, the immobilized GOx displayed higher operational stability than the free enzyme under severe circumstances and was easily recovered by magnetic separation. With increased doping concentration of the nanocomposites, the photocatalytic activity was assessed using a degradation process in the presence of methylene blue dye under UV light irradiation, which revealed that the surface area of the nanocomposites with increased doping concentration played a significant role in improving photocatalytic activity. The antibacterial activity of Ni-Co ferrite/SiO2 nanocomposites was assessed using the agar well diffusion method against Escherichia coli, a gram-negative bacteria (ATCC 25922). Consequently, it was revealed that doping of Ni2+ and Co2+ in Fe2O4/SiO2 nanocomposites at varied concentrations improved their antibacterial properties.

Promising strategies to control persistent enemies: Some new technologies to combat biofilm in the food industry-A review

Biofilm is an advanced form of protection that allows bacterial cells to withstand adverse environmental conditions. The complex structure of biofilm results from genetic-related mechanisms besides other factors such as bacterial morphology or substratum properties. Inhibition of biofilm formation of harmful bacteria (spoilage and pathogenic bacteria) is a critical task in the food industry because of the enhanced resistance of biofilm bacteria to stress, such as cleaning and disinfection methods traditionally used in food processing plants, and the increased food safety risks threatening consumer health caused by recurrent contamination and rapid deterioration of food by biofilm cells. Therefore, it is urgent to find methods and strategies for effectively combating bacterial biofilm formation and eradicating mature biofilms. Innovative and promising approaches to control bacteria and their biofilms are emerging. These new approaches range from methods based on natural ingredients to the use of nanoparticles. This literature review aims to describe the efficacy of these strategies and provide an overview of recent promising biofilm control technologies in the food processing sector.

A comparative study based on activity, conformation and computational analysis on the inhibition of human salivary aldehyde dehydrogenase by phthalate plasticizers: Implications in assessing the safety of packaged food items

Phthalate plasticizers are commonly used in various consumer-end products. Human salivary aldehyde dehydrogenase (hsALDH) is a detoxifying enzyme which defends us from the toxic aldehydes. Here, the effect of phthalates [Di-2-ethylhexyl phthalate (DEHP), Diethyl phthalate (DEP) and Dibutyl phthalate (DBP)] on hsALDH has been investigated. These plasticizers inhibited hsALDH, and the IC₅₀ values were 0.48 ± 0.04, 283.20 ± 0.09 and 285.00 ± 0.14 μM for DEHP, DEP and DBP, respectively. DEHP was the most potent inhibitor among the three plasticizers. They exhibited mixed-type linear inhibition with inclination towards competitive-non-competitive inhibition. They induced both tertiary and secondary structural changes in the enzyme. Quenching of intrinsic hsALDH fluorescence in a constant manner was observed with a binding constant (K_b) of 8.91 × 10⁶, 2.80 × 10⁴, and 1.31 × 10⁵ M^-1, for DEHP, DEP and DBP, respectively. Computational analysis showed that these plasticizers bind stably in the proximity of hsALDH catalytic site, reciprocating via non-covalent interactions with some of the amino acids which are evolutionary conserved. Therefore, exposure to these plasticizers inhibits hsALDH which increases the risk of aldehyde induced toxicity, adversely affecting oral health. The study has implications in assessing the safety of packaged food items which utilize phthalates.

Joint effects of carbon nanotubes and copper oxide nanoparticles on fermentation metabolism towards Saccharofermentans acetigenes: Enhancing environmental adaptability and transcriptional expression

In this study, the joint effects of widely used copper oxide nanoparticles (CuO NPs) and multi-walled carbon nanotubes (MWCNTs) on the fermentation metabolism of a model acetogenic bacterium Saccharofermentans acetigenes were investigated and the underlying mechanisms were further explored. The presence of sole CuO NPs or MWCNTs severely inhibited the acetate generation, while their co-existences did not further decrease the acetate yield as expected. Further analysis indicated the joint effects facilitated the enhancement of bacterial stimulus response to the environment and interspecies communication, which improved adaptive capacity to the adverse environment involved in nanomaterials. Meanwhile, the co-existence reduced inhibitory effects of sole nanomaterial on the gene expressions and catalytic activities of key enzymes involved in glycolysis and pyruvate metabolism. Therefore, the joint effects could enhance environmental adaptation of S. acetigenes and transcriptional expressions of key enzymes for acetic acid production-related processes, alleviating the inhibition of CuO NPs to acetate production.

Modulation of laccase catalysed oxidations at the surface of magnetic nanoparticles

We explored the coupling of laccases to magnetic nanoparticles (MNPs) with different surface chemical coating. Two laccase variants offering two opposite and precise orientations of the substrate oxidation site were immobilised onto core-shell MNPs presenting either aliphatic aldehyde, aromatic aldehyde or azide functional groups at the particles surface. Oxidation capabilities of the six-resulting laccase-MNP hybrids were compared on ABTS and coniferyl alcohol. Herein, we show that the original interfaces created differ substantially in their reactivities with an amplitude from 1 to > 4 folds depending on the nature of the substrate. Taking enzyme orientation into account in the design of surface modification represents a way to introduce selectivity in laccase catalysed reactions.

Occurrence, effect, and fate of residual microplastics in anaerobic digestion of waste activated sludge: A state-of-the-art review

The plastic products have large consumption over last decades, resulting in a serious microplastics (MPs) pollution. Specially, the main removal way of MPs from wastewater is to transfer MPs from liquid to solid phase, leading to its enrichment in waste activated sludge (WAS). Anaerobic digestion has been served as the most potential technique to achieve both resource recovery and sludge reduction, herein this review provides current information on occurrence, effect, and fate of MPs in anaerobic digestion of WAS. The effects of MPs on WAS anaerobic digestion are greatly related to forms, particles sizes, contents, compositions and leachates of MPs. Also, the presence of MPs not only can change the effects of other pollutants on anaerobic digestion of WAS, but also can affect the fates of them. Besides, the future perspectives focused on the fate, effect and final removal of MPs during WAS anaerobic digestion process are outlined.

Magnetic Metal Organic Framework Immobilized Laccase for Wastewater Decolorization

The laccase enzyme was successfully immobilized over a magnetic amino-functionalized metal–organic framework Fe3O4-NH2@MIL-101(Cr). Different techniques were used for the characterization of the synthesized materials. The Fe3O4-NH2@MIL-101(Cr) laccase showed excellent resistance to high temperatures and low pH levels with a high immobilization capacity and large activity recovery, due to the combination of covalent binding and adsorption advantages. The long-term storage of immobilized laccase for 28 days indicated a retention of 88% of its initial activity, due to the high stability of the immobilized system. Furthermore, a residual activity of 49% was observed at 85 °C. The immobilized laccase was effectively used for the biodegradation of Reactive Black 5 (RB) and Alizarin Red S (AR) dyes in water. The factors affecting the RB and AR degradation using the immobilized laccase (dye concentration, temperature and pH) were investigated to determine the optimum treatment conditions. The optimum conditions for dye removal were a 5 mg/L dye concentration, temperature of 25 °C, and a pH of 4. At the optimum conditions, the biodegradation and sorption-synergistic mechanism of the Fe3O4-NH2@MIL-101(Cr) laccase system caused the total removal of AR and 81% of the RB. Interestingly, the reusability study of this immobilized enzyme up to five cycles indicated the ability to reuse it several times for water treatment.

Magnetically Agitated Nanoparticle-Based Batch Reactors for Biocatalysis with Immobilized Aspartate Ammonia-Lyase

In this study, we investigated the influence of different modes of magnetic mixing on effective enzyme activity of aspartate ammonia-lyase from Pseudomonas fluorescens immobilized onto epoxy-functionalized magnetic nanoparticles by covalent binding (AAL-MNP). The effective specific enzyme activity of AAL-MNPs in traditional shake vial method was compared to the specific activity of the MNP-based biocatalyst in two devices designed for magnetic agitation. The first device agitated the AAL-MNPs by moving two permanent magnets at two opposite sides of a vial in x-axis direction (being perpendicular to the y-axis of the vial); the second device unsettled the MNP biocatalyst by rotating the two permanent magnets around the y-axis of the vial. In a traditional shake vial, the substrate and biocatalyst move in the same direction with the same pattern. In magnetic agitation modes, the MNPs responded differently to the external magnetic field of two permanent magnets. In the axial agitation mode, MNPs formed a moving cloud inside the vial, whereas in the rotating agitation mode, they formed a ring. Especially, the rotating agitation of the MNPs generated small fluid flow inside the vial enabling the mixing of the reaction mixture, leading to enhanced effective activity of AAL-MNPs compared to shake vial agitation.

Designing of Nanomaterials-Based Enzymatic Biosensors: Synthesis, Properties, and Applications

Among the many biological entities employed in the development of biosensors, enzymes have attracted the most attention. Nanotechnology has been fostering excellent prospects in the development of enzymatic biosensors, since enzyme immobilization onto conductive nanostructures can improve characteristics that are crucial in biosensor transduction, such as surface-to-volume ratio, signal response, selectivity, sensitivity, conductivity, and biocatalytic activity, among others. These and other advantages of nanomaterial-based enzymatic biosensors are discussed in this work via the compilation of several reports on their applications in different industrial segments. To provide detailed insights into the state of the art of this technology, all the relevant concepts around the topic are discussed, including the properties of enzymes, the mechanisms involved in their immobilization, and the application of different enzyme-derived biosensors and nanomaterials. Finally, there is a discussion around the pressing challenges in this technology, which will be useful for guiding the development of future research in the area.

Photocatalytic, Bactericidal and Molecular Docking Analysis of Annealed Tin Oxide Nanostructures

Nanosized tin oxide was fabricated with a simple and cost-effective precipitation technique and was analyzed by performing x-ray powder diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, high-resolution transmission electron (HR-TEM) microscopy, energy-dispersive x-ray (EDX) and UV-Vis spectroscopy. The XRD results revealed that tin oxide particles possessed typical orthorhombic structure and exhibited improved crystallinity with annealing. Calcination at 250 °C produced predominantly orthorhombic SnO which transformed to SnO₂ at higher temperatures of 500 and 750 °C. HRTEM and FESEM images showed existence of agglomeration within the particles of tin oxide. The absorption was found to increase up to a certain annealing temperature followed by a decrease, which was recorded via UV-Vis spectroscopy. The effect of annealing temperature on dye decomposition behavior of synthesized photocatalysts was studied. It was noted that annealing temperature affects the size of synthesized particles, band gap width and photoactivity of tin oxide. The sample prepared at 500 °C followed first-order kinetics and exhibited maximum photocatalytic reactivity toward methylene blue. The experimental results obtained from the present study indicate that SnO₂ is a promising and beneficial catalyst to remove contaminants from wastewater and environment. The antimicrobial evaluation of SnO annealed at 500 °C against selected targets such as E. coli and S. aureus depicted significant inhibition zones in comparison with 250 and 750 °C samples. Furthermore, molecular docking predictions of SnO₂ nanoparticles (NPs) were performed against active pocket of β-lactamase and DNA gyrase enzyme belonging to cell wall and nucleic acid biosynthetic pathway, respectively. The fabricated NPs showed good binding score against β-lactamase of both E. coli (- 5.71 kcal/mol) and S. aureus (- 11.83 kcal/mol) alongside DNA gyrase (- 9.57 kcal/mol; E. coli and - 8.61 kcal/mol; S. aureus). These in silico predictions suggested SnO₂ NPs as potential inhibitors for selected protein targets and will facilitate to have a clear understanding of their mechanism of action that may contribute toward new antibiotics discovery.

Correlation between the Activity of Aldehyde Dehydrogenase and Oxidative Stress Markers in the Saliva of Diabetic Patients

BACKGROUND

Reactive aldehydes are involved in diseases associated with oxidative stress, including diabetes. Human salivary aldehyde dehydrogenase (hsALDH) presumably protects us from many toxic ingredient/contaminant aldehydes present in food.

OBJECTIVE

This study aimed to probe the activity of hsALDH in patients with diabetes and than to correlate it with various oxidative stress markers in the saliva.

METHODS

The saliva samples were collected from total 161 diabetic patients from Rajiv Gandhi Centre for Diabetes, Jawaharlal Nehru Medical College (JNMC), AMU, Aligarh, (India). HsALDH activity and markers of oxidative stress [8-hydroxydeoxyguanosine (8-OHDG), malondialdehyde (MDA) and advanced glycation end products (AGEs)] were measured in the saliva samples.

RESULTS

Patients with early stage of diabetes had higher activity of hsALDH when compared with the control group. As the history of diabetes increases, the activity of the enzyme decreases and also higher oxidative stress markers (8-OHDG, MDA and AGEs) are detected in the saliva samples. Negative significant correlation between hsALDH activity and oxidative stress markers were observed (p <0.0001).

CONCLUSION

The activity of hsALDH increases in early stages of diabetes most probably to counter the increased oxidative stress associated with diabetes. However, in later stages of diabetes, the activity of the enzyme decreases, possibly due to its inactivation resulting from glycation.

Chlorpyrifos degradation efficiency of Bacillus sp. laccase immobilized on iron magnetic nanoparticles

The present study explored the immobilization of laccase onto iron magnetic nanoparticles (MNPs) to enhance its enzymatic properties and applications. The immobilization process was optimized using Box-Behnken design (BBD). BBD showed significance towards the quadratic model with experimental data. Maximum laccase activity recovery (99%) of the predicted model was observed at 0.75 mg/mL of laccase concentration, 200 mg/mL of MNPs, 0.3% cross linking with carbodiimide, and 3 h of cross-linking time. The magnetization activity of MNPs (8 emu/g) and the immobilized laccase with MNPs (4 emu/g) was analyzed using vibrating sample magnetometer (VSM). Maximum activity of immobilized laccase was observed at pH 7.0 and 55 °C. The immobilized laccase has greater stability (100 h) and significant chlorpyrifos (pesticide) degradation activity. High-performance liquid chromatography (HPLC) results confirmed the degraded metabolic products of chlorpyrifos. In all, the immobilized laccase was superior to free laccase, showing promising structural and application characteristics.

Recent developments in enzyme immobilization technology for high-throughput processing in food industries

The demand for food and beverage markets has increased as a result of population increase and in view of health awareness. The quality of products from food processing industry has to be improved economically by incorporating greener methodologies that enhances the safety and shelf life via the enzymes application while maintaining the essential nutritional qualities. The utilization of enzymes is rendered more favorable in industrial practices via the modification of their characteristics as attested by studies on enzyme immobilization pertaining to different stages of food and beverage processing; these studies have enhanced the catalytic activity, stability of enzymes and lowered the overall cost. However, the harsh conditions of industrial processes continue to increase the propensity of enzyme destabilization thus shortening their industrial lifespan namely enzyme leaching, recoverability, uncontrollable orientation and the lack of a general procedure. Innovative studies have strived to provide new tools and materials for the development of systems offering new possibilities for industrial applications of enzymes. Herein, an effort has been made to present up-to-date developments on enzyme immobilization and current challenges in the food and beverage industries in terms of enhancing the enzyme stability.

A thermophilic and thermostable xylanase from Caldicoprobacter algeriensis: Recombinant expression, characterization and application in paper biobleaching

A novel xylanase gene xynBCA, encoding a polypeptide of 439 residues (XynBCA), was cloned from Caldicoprobacter algeriensis genome and recombinantly expressed in Escherichia coli BL21(DE3). The amino acid sequence analysis showed that XynBCA belongs to the glycoside hydrolase family 10. The purified recombinant enzyme has a monomeric structure of 52 kDa. It is active and stable in a wide range of pH from 3 to 10 with a maximum activity at 6.5. Interestingly, XynBCA was highly thermoactive with an optimum temperature of 80 °C, thermostable with a half-life of 20 min at 80 °C. The specific activity was 117 U mg^-1, while the K_m and V_max were 1.247 mg ml^-1, and 114.7 μmol min^-1 mg^-1, respectively. The investigation of XynBCA in kraft pulp biobleaching experiments showed effectiveness in releasing reducing sugars and chromophores, with best achievements at 100 U g^-1 of pulp and 1 h of incubation. The comparative molecular modeling studies with the less thermostable Xylanase B from Clostridium stercorarium, revealed extra charged residues at the surface of XynBCA potentially participating in the formation of intermolecular hydrogen bonds with solvent molecules or generating salt bridges, therefore contributing to the higher thermal stability.

Immobilization of Cellulolytic Enzymes in Mesostructured Silica Materials

Mesostructured silica nanoparticles offer a unique opportunity in the field of biocatalysis thanks to their outstanding properties. The tunable pore size in the range of mesopores allows for immobilizing bulky enzyme molecules. The large surface area improves the catalytic efficiency by increasing enzyme loading and finely dispersing the biocatalyst molecules. The easily tunable pore morphology allows for creating a proper environment to host an enzyme. The confining effect of mesopores can improve the enzyme stability and its resistance to extreme pH and temperatures. Benefits also arise from other peculiarities of nanoparticles such as Brownian motion and easy dispersion. Fossil fuel depletion and environmental pollution have led to the need for alternative sustainable and renewable energy sources such as biofuels. In this context, lignocellulosic biomass has been considered as a strategic fuel source. Cellulases are a class of hydrolytic enzymes that convert cellulose into fermentable sugars. This review is intended to survey the immobilization of cellulolytic enzymes (cellulases and β-glucosidase) onto mesoporous silica nanoparticles and their catalytic performance, with the aim to give a contribution to the urgent action required against climate change and its impacts, by biorefineries’ development.

Immobilization of laccase on Sepharose-linked antibody support for decolourization of phenol red

Laccases which are considered as "green tools" in biotechnology have potential to degrade toxic contaminants/synthetic dyes present in industrial effluents. The loss in activity and stability of laccases are key challenges faced in their potential industrial applications. Here, laccase from Trametes versicolor (polypore mushroom) was immobilized on Sepharose-linked antibody support to carry out the decolourization of phenol red. This support was prepared by covalent linking of anti-laccase antibodies to CNBr activated Sepharose at pH 8.5, and then laccase was immobilized on this affinity support at pH 5.0. The amount of laccase immobilized was approximately 33 mg per gram of the affinity support, giving an immobilization yield of 83.4%. The immobilized enzyme displayed an activity of 3.88 U with an effectiveness factor (η) of 0.90. Immobilization of laccase led to significant enhancement in thermal and storage stability. The immobilized enzyme retained 44% of its activity after 10 cycles of continuous use. The decolourization of phenol red dye obtained by immobilized and soluble laccase after 6 h of incubation at 50 °C was 80 and 56%, respectively. Thus, immobilization of laccase on Sepharose-linked antibody support leads to remarkable improvement in its various properties, making it more versatile for industrial applications.

Intrinsic peroxidase-like activity of 4-amino hippuric acid reduced/stabilized gold nanoparticles and its application in the selective determination of mercury and iron in ground water

Herein, we report a method for the synthesis of 4-aminohippuric acid (4-AHA) reduced/stabilized gold nanoparticles and their peroxidase mimicking properties for the colorimetric detection of Fe³⁺ and Hg²⁺. The synthesis of nanoparticles was evidenced by appearance of bright red color and an absorption peak at 518 nm. Transmission electron microscopic (TEM) characterization revealed the nanoparticles to be spherical with average size of about 5.9 ± 1.7 nm. X-ray diffraction (XRD) analysis established highly crystalline nature of the nanoparticles. The synthesized nanoparticles have shown very good peroxidase mimicking property; exhibiting the catalytic oxidation of the chromogen 3,3',5,5'-tetramethyl benzidine (TMB) to a blue color product, in the presence of hydrogen peroxide. The peroxidase mimicking activity of the nanoparticles was found to be selectivity enhanced in the presence of Fe³⁺ and Hg²⁺ while there was no change in the activity in the presence of other concomitant ions. The mechanism studies revealed that the synthesized gold nanoparticles assisted in electron transfer during the catalytic process however the stimulation of peroxidase-like activity in the presence of Fe³⁺ and Hg²⁺ is owed to both generation of hydroxyl radical and accelerated electron transfer. The assay was made selective for iron by the addition of cysteine in acetate buffer; whereas the selective detection of mercury was achieved by carrying out the assay in citrate buffer. The linear ranges for the determination of Fe³⁺ and Hg²⁺ in deionized water were found to be: 5-50 ppb and 5-200 ppb respectively. The limits of quantification (LOQ) for Fe³⁺ and Hg²⁺ were 4.0 and 2.5 ppb respectively. The assay was applied for the determination of Fe³⁺ and Hg²⁺ in drinking and ground water samples. The method holds potential for the on-field screening of these metal ions in real environmental samples.

Arsenic inhibits human salivary aldehyde dehydrogenase: Mechanism and a population-based study

Human salivary aldehyde dehydrogenase (hsALDH) is an important detoxifying enzyme and maintains oral health. Subjects with low hsALDH activity are at a risk of developing oral cancers. Arsenic (As) toxicity causes many health problems in humans. The objective of this population-based study was to correlate As contamination and hence low hsALDH activity with high incidence of cancer cases in Bareilly district of India. Here, it was observed that As inhibited hsALDH (IC₅₀ value: 33.5 ± 2.5 μM), and the mechanism of inhibition was mixed type (in between competitive and non-competitive). Binding of As to hsALDH changed the conformation of the enzyme. A static quenching mechanism was observed between the enzyme and As with a binding constant (K_b) of 9.77 × 10⁴ M^-1. There is one binding site for As on hsALDH molecule. Further, the activity of hsALDH in volunteers living in regions of higher As levels in drinking water (Bahroli and Mirganj village of Bareilly district, India), and those living in region having safe levels of As (Aligarh city, India) was determined. The As level in the saliva samples of the volunteers was determined by inductively coupled plasma mass spectroscopy (ICP-MS). Low hsALDH activity was found in volunteers living in the region of higher As levels. The activity of hsALDH and As concentration in the saliva was found to be negatively correlated (r = - 0.427, p < 0.0001). Therefore, we speculate that the high incidence of cancer cases reported in Bareilly district may be due to higher As contamination.

Immobilization of β-galactosidase on tannic acid stabilized silver nanoparticles: A safer way towards its industrial application

In this study, β-galactosidase has been immobilized on tannic acid stabilized silver nanoparticles (AgNPs). Tannic acid is a phytochemical and it is advantageous to use it as a linker molecule for immobilization because of its antidiarrheal and antimicrobial properties, and very low toxicity. AgNPs with immobilized β-galactosidase were characterized for particle size and catalytic properties. The AgNPs consisted of almost monodispersed particles of average diameter of ∼20 nm. β-galactosidase immobilized on tannic acid stabilized AgNPs (83.6% Immobilization yield) exhibited good activity with a high enzyme to carrier ratio as compared to the previous reports. Immobilization did not affect the optimum pH (pH 4.5) of the enzyme, however it retained greater fraction of activity in both alkaline and acidic pH range. The immobilized enzyme exhibited greater fraction of activity at higher temperatures as compared to the soluble enzyme, and its optimum temperature increased by 5 °C. The immobilized enzyme retained almost 60% of its activity after 10th successive use. The immobilized enzyme hydrolyzed 258 and 474 μM lactose from 1% lactose and from milk lactose, respectively, whereas the soluble enzyme hydrolyzed 235 and 424 μM lactose from 1% lactose and from milk lactose, respectively. Excellent activity and stability of β-galactosidase immobilized on AgNPs provides a cost-effective industrial application of this enzyme. β-galactosidase immobilized on tannic acid stabilized AgNPs are free from toxicity hazards of the linker molecules. Hence, it may find constructive enzyme based applications in food technology.

Structural-Dependent N,O-Donor Imine-Appended Cu(II)/Zn(II) Complexes: Synthesis, Spectral, and in Vitro Pharmacological Assessment

Four mononuclear bioefficient imine-based coordination complexes, [(L ¹ ) ₂ Cu], [(L ¹ ) ₂ Zn], [(L ² )Cu(H ₂ O)], and [(L ² )Zn(H ₂ O)], were synthesized using ligands [L ¹ = 2-(((3-hydroxynaphthalen-2-yl)methylene)amino)-2-methylpropane-1,3-diol and L ² = 4-(1-((1,3-dihydroxy-2-methylpropan-2-yl)imino)ethyl)benzene-1,3-diol]. The formation of the complexes was ascertained by elemental analysis, Fourier transform infrared, ¹H NMR, ¹³C NMR, electrospray ionization-mass spectroscopy, electron paramagnetic resonance, and thermogravimetric analysis. The comparative binding propensity profiles of the above-synthesized complexes with the DNA/human serum albumin (HSA) were investigated via UV absorption, fluorescence, and Förster resonance energy-transfer studies. On the basis of extended conjugation and planarity, L ¹ complexes exhibited superior bioactivity with greater calculated DNA binding constant values, (K _b) 2.9444 × 10³ [(L ¹ ) ₂ Cu] and 2.2693 × 10³ [(L ¹ ) ₂ Zn], as compared to L ² complexes, 1.793 × 10³ [(L ² )Cu(H ₂ O)] and 9.801 × 10² [(L ² )Zn(H ₂ O)]. The competitive displacement assay of complexes was performed by means of fluorogenic dyes (EtBr and Hoechst), which corroborates the occurrence of minor groove binding because of the enhanced displacement activity with Hoechst 33258. The minor groove binding of the [(L ¹ ) ₂ Cu] complex is further confirmed by the molecular docking study. Moreover, the HSA study demonstrated effective static quenching of complexes with substantial K _sv values. The [(L ¹ ) ₂ Cu] complex was found to have pronounced cleavage efficiency as evaluated from sodium dodecyl sulfate polyacrylamide gel electrophoresis electrophoresis. Furthermore, in vitro antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl and superoxide radicals further proclaimed the remarkable bioefficiency of compounds, which make them promising as active chemotherapeutic agents.

Covalent Immobilization of β-Glucosidase into Mesoporous Silica Nanoparticles from Anhydrous Acetone Enhances Its Catalytic Performance

An immobilization protocol of a model enzyme into silica nanoparticles was applied. This protocol exploited the use of the bifunctional molecule triethoxysilylpropylisocyanate (TEPI) for covalent binding through a linker of suitable length. The enzyme β-glucosidase (BG) was anchored onto wrinkled silica nanoparticles (WSNs). BG represents a bottleneck in the conversion of lignocellulosic biomass into biofuels through cellulose hydrolysis and fermentation. The key aspect of the procedure was the use of an organic solvent (anhydrous acetone) in which the enzyme was not soluble. This aimed to restrict its conformational changes and thus preserve its native structure. This approach led to a biocatalyst with improved thermal stability, characterized by high immobilization efficiency and yield. It was found that the apparent KM value was about half of that of the free enzyme. The Vmax was about the same than that of the free enzyme. The biocatalyst showed a high operational stability, losing only 30% of its activity after seven reuses.

Ethyl Butyrate Synthesis Catalyzed by Lipases A and B from Candida antarctica Immobilized onto Magnetic Nanoparticles. Improvement of Biocatalysts' Performance under Ultrasonic Irradiation

The synthesis of ethyl butyrate catalyzed by lipases A (CALA) or B (CALB) from Candida antarctica immobilized onto magnetic nanoparticles (MNP), CALA-MNP and CALB-MNP, respectively, is hereby reported. MNPs were prepared by co-precipitation, functionalized with 3-aminopropyltriethoxysilane, activated with glutaraldehyde, and then used as support to immobilize either CALA or CALB (immobilization yield: 100 ± 1.2% and 57.6 ± 3.8%; biocatalysts activities: 198.3 ± 2.7 U_p-NPB/g and 52.9 ± 1.7 U_p-NPB/g for CALA-MNP and CALB-MNP, respectively). X-ray diffraction and Raman spectroscopy analysis indicated the production of a magnetic nanomaterial with a diameter of 13.0 nm, whereas Fourier-transform infrared spectroscopy indicated functionalization, activation and enzyme immobilization. To determine the optimum conditions for the synthesis, a four-variable Central Composite Design (CCD) (biocatalyst content, molar ratio, temperature and time) was performed. Under optimized conditions (1:1, 45 °C and 6 h), it was possible to achieve 99.2 ± 0.3% of conversion for CALA-MNP (10 mg) and 97.5 ± 0.8% for CALB-MNP (12.5 mg), which retained approximately 80% of their activity after 10 consecutive cycles of esterification. Under ultrasonic irradiation, similar conversions were achieved but at 4 h of incubation, demonstrating the efficiency of ultrasound technology in the enzymatic synthesis of esters.

Green construction of recyclable amino-tannic acid modified magnetic nanoparticles: Application for β-glucosidase immobilization

The β-glucosidase (BGL) enzyme in food industry is great interest due to its role in food conversion to produce functional food products. In this study, the BGL was covalently immobilized onto amino-tannic acid modified Fe₃O₄ magnetic nanoparticles (ATA-Fe₃O₄ MNPs) as biocompatible nanoplatform by modified poly-aldehyde pullulan (PAP) as a cross-linker to enhance the ability and strength of the nanoparticle connection to the enzyme. The properties of support were subsequently characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transformed infrared (FTIR), X-ray diffraction (XRD), and vibrating sample magnetometer (VSM). The highest percentage of loading and immobilization yield was obtained with 0.1 mg enzyme/mL citrate buffer (pH 6, 1 M) enzyme solution, carrier solution of 10 mg ATA-Fe₃O₄/3 mL citrate buffer (pH 6, 1 M), and PAP solution of 20% total reaction system volume. Optimum pH and temperature were found for free (pH 5.0 and temperature 30 °C) and immobilized (pH 6.0 and temperature 40 °C) enzyme. The immobilized BGL maintains its activity to 83% after 10 cycles. Therefore, immobilization of BGL by this method is an efficient procedure to improve the properties of enzyme.

Enzymatic Bioremediation of Organophosphate Compounds-Progress and Remaining Challenges

Organophosphate compounds are ubiquitously employed as agricultural pesticides and maintained as chemical warfare agents by several nations. These compounds are highly toxic, show environmental persistence and accumulation, and contribute to numerous cases of poisoning and death each year. While their use as weapons of mass destruction is rare, these never fully disappear into obscurity as they continue to be tools of fear and control by governments and terrorist organizations. Beyond weaponization, their wide-scale dissemination as agricultural products has led to environmental accumulation and intoxication of soil and water across the globe. Therefore, there is a dire need for rapid and safe agents for environmental bioremediation, personal decontamination, and as therapeutic detoxicants. Organophosphate hydrolyzing enzymes are emerging as appealing targets to satisfy decontamination needs owing to their ability to hydrolyze both pesticides and nerve agents using biologically-derived materials safe for both the environment and the individual. As the release of genetically modified organisms is not widely accepted practice, researchers are exploring alternative strategies of organophosphate bioremediation that focus on cell-free enzyme systems. In this review, we first discuss several of the more prevalent organophosphorus hydrolyzing enzymes along with research and engineering efforts that have led to an enhancement in their activity, substrate tolerance, and stability. In the later half we focus on advances achieved through research focusing on enhancing the catalytic activity and stability of phosphotriesterase, a model organophosphate hydrolase, using various approaches such as nanoparticle display, DNA scaffolding, and outer membrane vesicle encapsulation.

A novel method to engineer proteases for selective enzyme inhibition

In this work, we have proposed a new strategy to expand the function of a protein. By taking a protease as an example, it can be engineered to make up the shortcoming of natural proteases, and thus it can efficiently and selectively hydrolyze a desired protein even in a complex biological fluid.

Laccase immobilization on amino-functionalized magnetic metal organic framework for phenolic compound removal

An amino-functionalized magnetic metal organic framework (MOF), Fe₃O₄-NH₂@MIL-101(Cr), was employed for laccase immobilization for the first time. The immobilized laccase was synthesized by the adsorption and covalent binding method, thus exhibited high activity recovery, large immobilization capacity and good tolerance to low pH and high temperature conditions. The excellent stability enabled the immobilized laccase to retain 89% of its initial activity after storage for 28 days. When the ambient temperature reached 85 °C, the immobilized laccase showed 49.1% residual activity even after 6 h preservation. The stability of laccase in organic solvents such as methanol was also greatly improved. Application of the immobilized laccase for 2,4-dichlorophenol removal was also investigated. The adsorption by Fe₃O₄-NH₂@MIL-101(Cr) contributed to a quick removal in the first hour, and the removal efficiency reached 87% eventually. When the reaction was completed, the immobilized laccase could be separated from the solution by a magnet. The results introduced a novel support for laccase immobilization, and the immobilized laccase had great potential in wastewater treatment.