Peroxide Degradation Research Articles

Investigation of the Influence of Copovidone Properties and Hot-Melt Extrusion Process on Level of Impurities, In Vitro Release, and Stability of an Amorphous Solid Dispersion Product.

Hot-melt extrusion (HME) is a widely used method for creating amorphous solid dispersions (ASDs) of poorly soluble drug substances, where the drug is molecularly dispersed in a solid polymer matrix. This study examines the impact of three different copovidone excipients, their reactive impurity levels, HME barrel temperature, and the distribution of colloidal silicon dioxide (SiO2) on impurity levels, stability, and drug release of ASDs and their tablets. Initial peroxide levels were higher in Kollidon VA 64 (KVA64) and Plasdone S630 (PS630) compared to Plasdone S630 Ultra (PS630U), leading to greater oxidative degradation of the drug in fresh ASD tablets. However, stability testing (50 °C, closed container, 50 °C/30% RH, open conditions) showed lower oxidative degradation impurities in ASD tablets prepared at higher barrel temperatures, likely due to greater peroxide degradation. Plasdone S630 is suitable for ASDs with drugs prone to oxidative degradation, while standard purity grades may benefit drugs susceptible to free radical degradation, as they generate fewer free radicals post-HME. ASD tablets exhibited greater physical stability than milled extrudate samples, likely due to reduced exposure to stability conditions within the tablet matrix. Including SiO2 in the extrudate composition resulted in greater physical stability of the ASD system in the tablet; however, it negatively affected chemical stability, promoting greater oxidative degradation and hydroxylation of the drug substance. No impact of the distribution of SiO2 on drug release was observed. The study also confirmed the congruent release of copovidone, the drug substance, and Tween 80 using flow NMR coupled with in-line UV/vis. This research highlights the critical roles of peroxide levels and SiO2 in influencing the dissolution and physical and chemical stability of ASDs. The findings provide valuable insights for developing stable and effective pharmaceutical formulations, emphasizing the importance of controlling reactive impurities and excipient characteristics in ASD products prepared by using HME.

Photocatalytic performance of CuO NPs: An experimental approach for process parameter optimization for Rh B dye

Optimization of process parameters for photocatalytic activity measurement of CuO nanoparticles (NPs) was the focus of this study. CuO NPs were prepared following chemical co-precipitation method and characterized using X-ray diffraction (XRD), ultraviolet visible (UV–vis) spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FTIR). Subsequent studies concentrated on optimizing pH of Rhodamine B (Rh B) dye, catalyst doses, and concentration of hydrogen peroxide (H2O2) for effective photocatalytic degradation. This optimization process was intended to properly investigate the photocatalytic activity of CuO NPs using Rh B dye (5 ppm), a frequently encountered organic pollutant. After 180 min of UV irradiation at optimized condition (pH 10, 0.3125 mg/mL NPs, 9000 ppm H2O2) a degradation rate of 60 percent was recorded. These findings maximized the degradation efficiency of CuO NPs to exploit as a potential photocatalyst.

Unveiling the kinetics and mechanism of sulfide-modified zero-valent iron activated hydrogen peroxide for phenol degradation

In this study, sulfide-modified zero-valent iron (S-ZVI) synthesized by a two-step process with optimal S/Fe ratio of 0.056 was used to activate hydrogen peroxide (H2O2) to degrade phenol, and the kinetics and reaction mechanism of phenol degradation were investigated under different conditions. Phenol degradation kinetics in S-ZVI/H2O2 system was characterized by an initial lag phase followed by a rapid reaction period, which was accurately described by Logistic regression model, deviating from conventional pseudo-first-order and pseudo-second-order models. Over 80 % of phenol degradation occurred via liquid-phase reactions, predominantly driven by hydroxyl radicals (•OH). The consumption of H2O2 and the removal of total organic carbon (TOC) were both significantly correlated with the total dissolved iron content, underscoring the importance of iron dissolution. The S-ZVI/H2O2 system outperformed other activated H2O2 systems, with a 41.71 %, 35.89 %, and 44.02 % increase in H2O2 utilization efficiency for TOC removal compared to FeSO4, ZVI, and ZVI(H+), respectively. Sulfide-modification of ZVI significantly promoted the sustained release of dissolved iron with a higher proportion of Fe2+, which was identified as a key factor in enhancing H2O2 utilization efficiency. Our findings provide new insight into a better description of the pollutant removal kinetics process in the S-ZVI/H2O2 system and the synergistic effects between S-ZVI and H2O2 for organic pollutant degradation.

Collective peroxide detoxification determines microbial mutation rate plasticity in E. coli.

Mutagenesis is responsive to many environmental factors. Evolution therefore depends on the environment not only for selection but also in determining the variation available in a population. One such environmental dependency is the inverse relationship between mutation rates and population density in many microbial species. Here, we determine the mechanism responsible for this mutation rate plasticity. Using dynamical computational modelling and in culture mutation rate estimation, we show that the negative relationship between mutation rate and population density arises from the collective ability of microbial populations to control concentrations of hydrogen peroxide. We demonstrate a loss of this density-associated mutation rate plasticity (DAMP) when Escherichia coli populations are deficient in the degradation of hydrogen peroxide. We further show that the reduction in mutation rate in denser populations is restored in peroxide degradation-deficient cells by the presence of wild-type cells in a mixed population. Together, these model-guided experiments provide a mechanistic explanation for DAMP, applicable across all domains of life, and frames mutation rate as a dynamic trait shaped by microbial community composition.

Design of Multivariate Biological Metal-Organic Frameworks: Toward Mimicking Active Sites of Enzymes.

Mimicking enzymatic processes carried out by natural enzymes, which are highly efficient biocatalysts with key roles in living organisms, attracts much interest but constitutes a synthetic challenge. Biological metal-organic frameworks (bioMOFs) are potential candidates to be enzyme catalysis mimics, as they offer the possibility to combine biometals and biomolecules into open-framework porous structures capable of simulating the catalytic pockets of enzymes. In this work, we first study the catalase activity of a previously reported bioMOF, derived from the amino acid L-serine, with formula {CaIICuII6[(S,S)-serimox]3(OH)2(H2O)} · 39H2O (1) (serimox = bis[(S)-serine]oxalyl diamide), which is indeed capable to mimic catalase enzymes, in charge of preventing cell oxidative damage by decomposing, efficiently, hydrogen peroxide to water and oxygen (2H2O2 → 2 H2O + O2). With these results in hand, we then prepared a new multivariate bioMOF (MTV-bioMOF) that combines two different types of bioligands derived from L-serine and L-histidine amino acids with formula CaIICuII6[(S,S)-serimox]2[(S,S)-hismox]1(OH)2(H2O)}·27H2O (2) (hismox = bis[(S)-histidine]oxalyl diamide ligand). MTV-bioMOF 2 outperforms 1 degrading hydrogen peroxide, confirming the importance of the amino acid residue from the histidine amino acid acting as a nucleophile in the catalase degradation mechanism. Despite displaying a more modest catalytic behavior than other reported MOF composites, in which the catalase enzyme is immobilized inside the MOF, this work represents the first example of a MOF in which an attempt is made to replicate the active center of the catalase enzyme with its constituent elements and is capable of moderate catalytic activity.

Algae promotes the biogenic oxidation of Mn(II) by accelerated extracellular superoxide production

Microbial manganese (Mn) oxidation, predominantly occurs within the anaerobic-aerobic interfaces, plays an important role in environmental pollution remediation. The anaerobic-aerobic transition zones, notably riparian and lakeside zones, are hotspots for algae-bacteria interactions. Here, we adopted a Mn(II)-oxidizing bacterium Pseudomonas sp. QJX-1 to investigate the impact of algae on microbial Mn(II) oxidation and verify the underlying mechanisms. Interestingly, we achieved a remarkable enhancement in bacterial Mn(II)-oxidizing activity within the algae-bacteria co-culture, despite the inability to oxidize Mn(II) for the algae used in this study. In addition, the bacterial density almost remains constant in the presence of algal cells. Therefore, the increased Mn(II) oxidation by QJX-1 in the presence of algae cannot be due to the increased biomass. Within this co-culture system, the Mn(II) oxidation rate surged to an impressive 0.23 mg/L/h, in stark contrast to 0.02 mg/L/h recorded within pure QJX-1 system. The presence of algae could inhibit the Fe-S cluster activity of QJX-1 by the produced active substance in co-culture, and result in the acceleration of extracellular superoxide production due to the impairment of electron transfer functions located in QJX-1 cell membranes. Moreover, elevated peroxidase gene expression and heightened extracellular catalase activity not only expedited Mn(II) ions oxidation but also facilitated conversion of intermediate Mn(III) ions into microbial Mn oxides, achieved through the degradation of hydrogen peroxide. Therefore, the acceleration of extracellular superoxide production and the decomposition of hydrogen peroxide are identified as the principal mechanisms behind the observed enhancement in Mn(II) oxidation within algae-bacteria co-cultures. Our findings highlight the need to consider the effect of algae on microbial Mn(II) oxidation, which plays an important role in the environmental pollution remediation.

Stability Indicating Force Degradation Study of Nintedanib in Bulk and Pharmaceutical Dosage Form

Assay of the nintedanib drug substance can be determined using a newly designed and verified reverse-phase high-performance liquid chromatography (RP-HPLC) method, even when degradation products from forced degradation experiments are present. By using gradient elution, the mobile phase was a mixture of 70% acetonitrile and 30% water by volume. Acid, base, peroxide, thermal, and photolytic degradation were among the stress conditions that the product was subjected to. During the thermal and photolytic breakdown processes, no extra contaminants were detected. Using validation criteria such as specificity, linearity, limit of quantitation (LoQ), accuracy, precision, robustness, and ruggedness, the developed technique was validated in accordance with International Council for Harmonization (ICH) recommendations. At a concentration of 12.4 ng/mL, the LoQ value was attained. The results showed good linearity (r2 > 1.00) across doses ranging from 2 to 10 μg/mL. Verification of recovery was done by adding concentrated solutions of 5, 10, and 15 μg/mL. So, newly developed RP-HPLC technology can separate Nintedanib from its main degradation products, and it can also estimate the drug substance’s concentration.

Antioxidants are ineffective at quenching reactive oxygen species inside bacteria and should not be used to diagnose oxidative stress.

A wide variety of stresses have been proposed to exert killing effects upon bacteria by stimulating the intracellular formation of reactive oxygen species (ROS). A key part of the supporting evidence has often been the ability of antioxidant compounds to protect the cells. In this study, some of the most-used antioxidants-thiourea, glutathione, N-acetylcysteine, and ascorbate-have been examined. Their ability to quench superoxide and hydrogen peroxide was verified invitro, but the rate constants were orders of magnitude too slow for them to have an impact upon superoxide and peroxide concentrations invivo, where these species are already scavenged by highly active enzymes. Indeed, the antioxidants were unable to protect the growth and ROS-sensitive enzymes of E. coli strains experiencing authentic oxidative stress. Similar logic posits that antioxidants cannot substantially quench hydroxyl radicals inside cells, which contain abundant biomolecules that react with them at diffusion-limited rates. Indeed, antioxidants were able to protect cells from DNA damage only if they were applied at concentrations that slow metabolism and growth. This protective effect was apparent even under anoxic conditions, when ROS could not possibly be involved, and it was replicated when growth was similarly slowed by other means. Experimenters should discard the use of antioxidants as a way of detecting intracellular oxidative stress and should revisit conclusions that have been based upon such experiments. The notable exception is that these compounds can effectively degrade hydrogen peroxide from environmental sources before it enters cells.

The role of ferroptosis as a regulator of oxidative stress in the pathogenesis of ischemic stroke.

Ferroptosis is a unique form of cell death that was first described in 2012 and plays a significant role in various diseases, including neurodegenerative conditions. It depends on a dysregulation of cellular iron metabolism, which increases free, redox-active, iron that can trigger Fenton reactions, generating hydroxyl radicals that damage cells through oxidative stress and lipid peroxidation. Lipid peroxides, resulting mainly from unsaturated fatty acids, damage cells by disrupting membrane integrity and propagating cell death signals. Moreover, lipid peroxide degradation products can further affect cellular components such as DNA, proteins, and amines. In ischemic stroke, where blood flow to the brain is restricted, there is increased iron absorption, oxidative stress, and compromised blood-brain barrier integrity. Imbalances in iron-transport and -storage proteins increase lipid oxidation and contribute to neuronal damage, thus pointing to the possibility of brain cells, especially neurons, dying from ferroptosis. Here, we review the evidence showing a role of ferroptosis in ischemic stroke, both in recent studies directly assessing this type of cell death, as well as in previous studies showing evidence that can now be revisited with our new knowledge on ferroptosis mechanisms. We also review the efforts made to target ferroptosis in ischemic stroke as a possible treatment to mitigate cellular damage and death.

Metronidazole degradation mechanism by sono-photo-Fenton processes using a spinel ferrite cobalt on activated carbon catalyst

A heterogeneous catalyst was prepared by anchoring spinel cobalt ferrite nanoparticles on porous activated carbon (SCF@AC). The catalyst was tested to activate hydrogen peroxide (HP) in the Fenton degradation of metronidazole (MTZ). SCF nanoparticles were produced through the co-precipitation of iron and cobalt metal salts in an alkaline condition. Elemental mapping, physico-chemical, morphological, structural, and magnetic properties of the as-fabricated catalyst were analyzed utilizing EDX mapping, FESEM-EDS, TEM, BET, XRD, and VSM techniques. The porous structure of AC enhanced the catalytic activity of SCF by a significant decrease in the agglomeration of SCF nanoparticles. The effectiveness of SCF@AC in Fenton degradation improved substantially when UV light and ultrasound (US) irradiations were induced, most likely due to the strong synergistic effect between the catalyst and these irradiation sources. The photo-Fenton system was more efficient than the Fenton, sono-, and sono-photo-Fenton processes eliminating both MTZ and TOC. It was found that AC not only dispersed SCF nanoparticles and improved the stability of the catalyst, but also provided a high adsorption capacity of MTZ, resulting in a faster degradation. After 60 min of the photo-Fenton reaction, the elimination efficiencies of MTZ (30 mg L−1) and TOC were 97 and 42.1% under optimum operational conditions (pH = 3.0, HP = 4.0 mM, SCF@AC = 0.3 g L−1, and UV = 6 W). SCF@AC showed excellent stability with low leaching of metal ions during the reaction. Radical and non-radical (O2•–, HO•, and 1O2 species), alongside adsorption and photocatalysis mechanisms, were responsible for MTZ decontamination over the SCF@AC/HP/UV system. A comprehensive study on the HP activation mechanism and MTZ degradation pathway was obtained through scavenging tests. The findings demonstrate that SCF@AC is an effective, reusable, and environmentally sustainable catalyst for advanced oxidation processes that can effectively remove organic pollutants from wastewater. This study offers valuable insights into the feasibility of employing SCF@AC catalysts in Fenton-based processes for the degradation of MTZ.

Se site targeted-two circles antioxidant in GPx4–like catalytic peroxide degradation by polyphenols (−)-epigallocatechin gallate and genistein using SERS

A Se site targeted-two circles antioxidant of polyphenols EGCG and genistein in glutathione peroxidase 4 (GPx4)–like catalytic peroxide H2O2 and cumene hydroperoxide degradation was demonstrated by surface-enhanced Raman scattering (SERS). Se atom's active center is presenting a ‘low-oxidation’ and a ‘high-oxidation’ catalytic cycle. The former is oxidized to selenenic acid (SeO−) with a Raman bond at 619/ 610 cm−1 assigned to the νO − Se by the hydroperoxide substrate at 544/ 551 cm−1 assigned to ωHSeC decreased. Under oxidative stress, the enzyme shifted to ‘high-oxidation’ catalytic cycle, in which GPx4 shuttles between R-SeO− and R-SeOO− with a Raman intensity of bond at 840/ 860 cm−1 assigned to νOSe. EGCG could act as a reducing agent both in H2O2 and Cu-OOH degradation, while, genistein can only reduce Cu-OOH, because it binds more readily to the selenium site in GPx4 than EGCG with a closer proximity, therefore may affect its simultaneous binding to coenzymes.

A Study on the Lateral Channel of Scytalidium Catalase

Catalases are antioxidant enzymes. Their main function is to convert hydrogen peroxide, one of the reactive oxygen species, into water and oxygen. A bifunctional catalase enzyme from Scytalidium thermophilum, which belongs to the monofunctional catalase family, exhibits oxidase activity in the absence of hydrogen peroxide without the need for a cofactor. It is able to oxidize a variety of ortho- and para-diphenolic compounds, but the oxidase activity is very low (~ 10,000-fold) compared to its main activity in peroxide degradation. In this study, an attempt was made to improve the oxidase activity of catalase for its industrial utilization. For this purpose, the residues located in the lateral channel (H214, D224, and K248), which are thought to play an important role in the access of oxidase substances to the active site, were selected and converted into an amino acid with a smaller side chain -Ala- by site-directed mutagenesis. The changes in the catalytic efficiency of the variants were evaluated by spectrophotometric analysis. The results showed that oxidase activity was increased two- to threefold in all variants, while some exhibited decreased catalase activity. The D224A variant gave the best results as it showed approximately 2-fold increase in oxidase activity without loss of catalase activity (about 92% of the wild-type catalase activity was retained). Thus, a protein variant with improved properties was successfully produced.

Plasma electrolytic formation and characterization of MnWO4/WO3 film heterostructures

MnWO4/WO3 p-n heterojunction films were fabricated using a one-step method consisting of the plasma electrolytic oxidation (PEO) of titanium in homogeneous electrolytes containing paratungstate ions and stable water-soluble EDTA-chelated manganese. The influences of the formation current density and W:Mn molar ratio of the electrolyte, which was varied from 1:2 to 2:1, on the composition, morphology, and optical and photocatalytic properties of the resulting coatings were studied. X-ray diffraction analysis, scanning electron microscopy, energy dispersive X-ray analysis, Raman spectroscopy, and ultraviolet diffuse reflectance spectroscopy were used to characterize the formed composites. Regardless of the W:Mn ratio of the electrolyte, the coatings contained crystalline t-WO3 and m-MnWO4. Depending on the formation conditions, the optical band gap energies of the composites varied from 2.63 to 3.01 eV. The largest absorption red shift and lowest band gap energy were observed in the film composite formed in an electrolyte with W:Mn = 2:1, at a current density of 0.2 A cm−2. Composites obtained in electrolytes with W:Mn ratios of 2:1 and 1:1 exhibited photocatalytic activity in the degradation of rhodamine C and methyl orange dyes in the presence of 10 mmol L–1 H2O2 under ultraviolet and visible light irradiation. The role of hydrogen peroxide in this dye degradation on PEO-coated composites under light irradiation is discussed.

Peroxidase like activity of Prussian blue nanoparticles and visible light mediated catalytic degradation of methylene blue dye

The environmental impact of dyes, particularly those utilized in the pharmaceutical and textile industries, has been a growing concern due to their persistence and potential harm to ecosystems. Methylene Blue (MB) dye is one of the commonly used synthetic dyes known for its adverse effects on the environment. Thus a promising catalyst is required for the effective degradation of MB dye. To effectively degrade MB, we have synthesized Prussian blue nanoparticles (PBNPs) in this work using the co-precipitation technique. These nanoparticles showed the peroxidase like behavior by degrading hydrogen peroxide and generating ROS (reactive oxygen species) under visible light exposure, which oxidized MB leads to its degradation. This degradation process was investigated under various experimental conditions, including pH, catalyst dosage, and peroxide concentration. The results demonstrated that PBNPs exhibited remarkable catalytic activity and completely degrade the MB within 50 min under visible light. The degradation efficiency was found to be pH-dependent and optimum efficiency was found in pH range from 5 to 7. The kinetic studies were shown that this MB degradation process follows the first order kinetic models with the rate constant value 0.038 s−1, suggesting that the degradation process follows Fenton mechanism. The recyclability and stability of the PBNPs as a catalyst were also assessed, which showed that it can be used up to four cycles, demonstrating their potential for practical applications in dye wastewater treatment.

Efficiency of Hydrogen Peroxide and Fenton Reagent for Polycyclic Aromatic Hydrocarbon Degradation in Contaminated Soil: Insights from Experimental and Predictive Modeling

This study investigates the degradation kinetics of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil using hydrogen peroxide (H2O2) and the Fenton process (H2O2/Fe2+). The effect of oxidant concentration and the Fenton molar ratio on PAH decomposition efficiency is examined. Results reveal that increasing H2O2 concentration above 25 mmol/samples leads to a slight increase in the rate constants for both first- and second-order reactions. The Fenton process demonstrates higher efficiency in PAH degradation compared to H2O2 alone, achieving decomposition yields ranging from 84.7% to 99.9%. pH evolution during the oxidation process influences PAH degradation, with alkaline conditions favoring lower elimination rates. Fourier-transform infrared (FTIR) spectroscopy analysis indicates significant elimination of PAHs after treatment, with both oxidants showing comparable efficacy in complete hydrocarbon degradation. The mechanisms of PAH degradation by H2O2 and the Fenton process involve hydroxyl radical formation, with the latter exhibiting greater efficiency due to Fe2+ catalysis. Gaussian process regression (GPR) modeling accurately predicts reduced concentration, with optimized ARD-Exponential kernel function demonstrating superior performance. The Improved Grey Wolf Optimizer algorithm facilitates optimization of reaction conditions, yielding a high degree of agreement between experimental and predicted values. A MATLAB 2022b interface is developed for efficient optimization and prediction of C/C0, a critical parameter in PAH degradation studies. This integrated approach offers insights into optimizing the efficiency of oxidant-based PAH remediation techniques, with potential applications in contaminated soil remediation.

Graphene Oxide Treated by Temperature with Enhancement of Adsorption for Organic Pollutants and Catalytic Degradation with Hydrogen Peroxide

Graphene oxide (GO) has been used in the range of organic pollutants adsorption and degradation. It’s important to improve the performance of GO in the treatment of organic pollutants. Here, we found that the organic pollutants were more efficiently removed in the catalytic degradation of hydrogen peroxide (H2O2) after being pre-adsorbed with GO. The performance of GO in degrading organic pollutants firstly enhanced and then weakened as the treated temperature increases in the air. The adsorption ability of GO for organic pollutants and catalytic activity of H2O2 were highest at 500 ℃, which can be ascribed to the highest oxygen-containing functional groups and the lowest defects on GO after 500 ℃ treatment in the air. This finding will improve the understanding and application of GO in organic pollutants treatment.Graphical

An Investigation on the Effect of N-Hydroxyphthalimde and Supercritical Carbon Dioxide on the Peroxide Degradation of Polypropylene

The peroxide degradation of polypropylene was studied in supercritical carbon dioxide (scCO2) in the presence of a N-hydroxyphthalimide (NHPI). Six levels of NHPI concentration and 6 levels of peroxide concentration were selected and each permutation was tested both with and without scCO2. It was observed that the NHPI would increase degradation at lower peroxide concentrations (<0.1 wt. %), but would suppress degradation at higher peroxide concentrations (>0.2 wt. %). Furthermore, it was discovered that at an NHPI concentration of 3.3 wt. %, the stereo regularity slightly decreased with increasing peroxide concentrations.

Changes in the blood redox status of horses subjected to combat training

Combat training of police horses, involving physical activity in the presence of environmental stressors, poses a risk of oxidative stress. This study compared the oxidative imbalance after combat training in horses in the regular police service and in horses that had just been schooled. Blood collection was performed immediately after training and after 16 h rest. The activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), and total antioxidant status (TAS) were determined as the markers of enzymatic antioxidant defence. At the same time, lipid peroxidation (TBARS) and protein carbonylation (Carb) were assessed as oxidation biomarkers. Additionally, oxidative imbalance indexes such as SOD/CAT, SOD/GPx, TBARS/TAS and TBARS/GPx were calculated. Animals during schooling had significantly lower SOD activity in erythrocytes than those experienced. CAT activity in erythrocytes was insignificantly higher immediately after training than during recovery. The SOD/GPx ratio was higher in experienced animals, which may reflect the intra-erythrocyte imbalance between enzymes producing and degrading hydrogen peroxide towards the first one. The concentration of carbonyl groups was significantly higher after the combat training compared to the recovery period in all horses. In inexperienced animals slight increase in TBARS/TAS and TBARS/GPx indexes were observed during the recovery time after exercises, contrary to experienced horses, in which these markers decreased slightly. These results suggest that the oxidative imbalance in inexperienced horses, although less pronounced just after combat training, was more prolonged as compared to horses in regular service.

Quorum sensing signal autoinducer-2 promotes hydrogen peroxide degradation in water by Gram-positive bacteria

Hydrogen peroxide is widely used to remedy bacterial and parasitic infections, but its excessive use will cause severe damage to aquatic animals. Moreover, there is no safe, efficient and low-cost method to degrade residual hydrogen peroxide in water. Here we developed a hydrogen peroxide removal mechanism by which autoinducer-2 (AI-2), a quorum sensing signal molecule that can promote the hydrogen peroxide degradation by Gram-positive bacteria. Here, we investigated the promotion effect of AI-2 on hydrogen peroxide degradation by Deinococcus sp. Y35 and the response of the antioxidant system. We further sought to understand the key mechanism underlying the promotion effect of AI-2 on hydrogen peroxide degradation is that, AI-2 contributed to the resistance of strain Y35 to oxidative stress induced by hydrogen peroxide, and altered membrane permeability of strain Y35 that allowed more hydrogen peroxide to enter bacterial cells and be degraded. Additionally, AI-2 can also encourage multiple Gram-positive bacteria to degrade hydrogen peroxide. Accordingly, our study serves as a reference for the regulation mechanism of the signal molecule AI-2 and provides the development of new strategies for hydrogen peroxide degradation.

Extremophile enzyme activity lab: using catalase from Pyrobaculum calidifontis to highlight temperature sensitivity and thermostable enzyme activity.

There are places on earth that are considered to possess extreme physico-chemical characteristics as they relate to life. Surprisingly, there are microbes that have adapted various strategies that enable them to form robust communities in these environments. The microbes that live in these environments, called extremophiles, are described as being thermophilic, psychrophilic, halophilic, acidophilic, alkaliphilic, barophilic, and so on. Given that extremophiles were not discovered until relatively recently due to a view point that the environments in which they inhabited were not conducive to life, it is reasonable to conclude that the concept of extremophiles may be hard to grasp for students. Herein is described a laboratory exercise adapted from laboratory exercises that use mesophilic catalase enzymes to illustrate the influence of physico-chemical parameters on enzyme activity. Catalase is an enzyme that accelerates the degradation of hydrogen peroxide to water and oxygen gas. In addition to mesophilic catalases, the catalase from Pyrobaculum calidifontis, a hyperthermophile with an optimal growth temperature of 90°C, is used to highlight the adaptation of an enzyme to an extreme environment. A visual comparison of bubble production by the hyperthermophilic and mesophilic enzymes after heating at high temperatures dramatically illustrates differences in thermostability that will likely reinforce concepts that are given in a pre-laboratory lecture that discusses not only the extremophiles themselves but also their applications in biotechnology and possible role in the field of astrobiology.