Optimum pH Research Articles

A Target to Combat Antibiotic Resistance: Biochemical and Biophysical Characterization of 3-Dehydroquinate Dehydratase from Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is associated with the acquisition of nosocomial infections, community-acquired infections, and infections related to livestock animals. In the pursuit of molecular targets in the development process of antibacterial drugs, enzymes within the shikimate pathway, such as 3-dehydroquinate dehydratase (DHQD), are regarded as promising targets. Therefore, through biochemical and biophysical techniques, in the present work, the characterization of DHQD from MRSA (SaDHQD) was performed. The kinetic results showed that the enzyme had a Vmax of 107 μmol/min/mg, a Km of 54 μM, a kcat of 48 s−1, and a catalytic efficiency of 0.9 μM−1 s−1. Within the biochemical parameters, the enzyme presented an optimal temperature of 55 °C and was thermostable at temperatures from 10 to 20 °C, being completely inactivated at 60 °C in 10 min. Furthermore, SaDHQD showed an optimal pH of 8.0 and was inactivated at pH 4.0 and 12.0. Moreover, the activity of the enzyme was affected by the presence of ions, surfactants, and chelating agents. The thermodynamic data showed that the rate of inactivation of the enzyme was a temperature-dependent process. Furthermore, the enthalpy change, entropy change, and Gibbs free energy change of inactivation were positive and practically constant, which suggested that the inactivation of SaDHQD by temperature was driven principally by enthalpic contributions. These results provide, for the first time, valuable information that contributes to the knowledge of this enzyme and will be useful in the search of SaDHQD inhibitors that can serve as leads to design a new drug against MRSA to combat antibiotic resistance.

Biological Characteristics, Pathogenicity, and Sensitivity to Fungicides of Four Species of Lasiodiplodia on Avocado Fruits

This study focuses on four species of Lasiodiplodia (L. euphorbiaceicola, L. mahajangana, L. theobromae, and L. pseudotheobromae), which are associated with avocado stem end rot (SER) in Hainan, China. The factors affecting the growth of Lasiodiplodia, pathogenicity to avocado and other tropical fruits, and sensitivity to 12 fungicides, were tested. All Lasiodiplodia spp. isolates were grown between 10 °C and 40 °C, with optimal growth temperature ranging from 28 to 30 °C; the lethal temperature ranged from 51 to 53 °C for 10 min. Optimal growth pH ranged from 5 to 6. The most suitable medium was PDA, the preferred carbon sources were D–fructose and soluble starch, and the preferred nitrogen sources were yeast and beef extract. All Lasiodiplodia spp. isolates were highly pathogenic to avocado fruit. In addition, their pathogenicity to six tropical fruits (banana guava, mango, papaya, pitaya, and soursop) was evaluated, and the results reveal that all four species of Lasiodiplodia are able to infect these fruits to various degrees of severity. The pathogenicity of both L. theobromae and L. pseudotheobromae was the highest among all the species tested. All Lasiodiplodia spp. isolates were highly susceptible to the fungicides fludioxonil, carbendazim, thiophanate–methyl, tetramycin, iprodione, tebuconazole, prochloraz, and imazalil, which are good candidates for controlling avocado SER. The results of the present study provide important information on the biological characteristics of these four species of Lasiodiplodia and provide a basis for the management of SER in avocado.

Carbon mineralization potential and nutrient dynamics in soils under vegetation types and soil depths at Luot mountain

Soil mineralization is a crucial soil process that improves soil physical properties, enhances carbon sequestration, and provides essential minerals and available nutrients for plant growth. This study was conducted at five vegetation types and soil depths at Luot mountain area, located in VNUF campus, Hanoi city. Samples were incubated in the dark at 25°C and measured at intervals of 1, 2, 5, 10, 15, 25, 35, and 40 days in the laboratory to determine C-CO2 respiration from soils. The study showed that CO2 emissions were highest in topsoils and decreased with deeper soil depths. Mineralized C-CO2 decreased from Shrubs > Acacia + Native species (NS) > Pinus + NS > Native species > Control. CO2 emissions peaked early in the incubation period and then stabilized in the 40-day incubation period. Larger aggregates (≥ 5mm) decreased significantly under most vegetation types, except for Shrubs, where the reduction was minimal. Aggregate size ≥3mm increased post-incubation, notably under Pinus + NS and Native species, with smaller aggregates also increasing slightly. Organic matter content was highest in the topsoil but decreased post-incubation due to microbial C mineralization. There was an increase in soil organic matter at 10-20 cm and 20-40 cm layers after incubation, especially under Shrubs. Available nitrogen slightly increased in soils post-incubation for most vegetation types. Phosphorus content increased post-incubation, peaking under Shrubs, while potassium levels were generally poor but increased during incubation. The study found that C-CO2 mineralization was strongly associated with soil porosity and pH, suggesting that higher porosity and optimal pH enhance mineralization, with organic matter content being crucial for available nutrient cycles in soils.

Insights into structural and proteomic alterations related to pH‐induced changes and protein deamidation in hair

AbstractObjectivesThe hair shaft is often exposed to shampoo and haircare products that have unknown or varying pH levels. These products contain a combination of surfactants and other active ingredients to treat the hair or the scalp. As amphoteric proteins, hair keratins have limited buffering capacity, so variations in pH can have multifaceted impacts on them. However, there is limited knowledge about how pH affects keratins and keratin‐associated proteins (KAPs). Therefore, this study aims to examine the effects of varying pH levels (pH 3–pH 12) on hair structure and analyse consequent alterations in the hair proteome using mass spectrometry‐based proteomics.MethodsA scanning electron microscope was used to examine changes in hair‐shaft morphology due to exposure to various pH levels, while mass spectrometry was employed to analyse protein alterations.ResultsWe found that exposing the hair shaft to varying pH levels led to specific effects on the cuticle, including cuticle lifting at certain pH levels, while proteomics analysis identified alterations in the hair proteome along with significant deamidation of keratins types I and II and KAPs. More pronounced effects were observed at extreme acidic conditions (pH 3) and alkaline conditions (above pH 8) on both hair morphology and hair proteins. pH levels between pH 5 and pH 7 had minimal impact on hair structure and proteins, suggesting that haircare products with pH in this range are ideal for hair‐shaft health. In contrast, alkaline pH levels were found to negatively affect hair.ConclusionsThe structure evaluation and proteomics data emphasize the critical role of pH in hair health. The extreme acidic or alkaline pH impacts the hair structure and hair proteins. The study highlights the optimal pH range for maintaining healthy hair.

Combined approach of nanoemulgel and microneedle pre-treatment as a topical anticellulite therapy

Background and purpose: Cellulite is caused by changes in the metabolism of the fatty tissue beneath the skin. Methylxanthines and retinoids are commonly added to the different anticellulite products. However, their topical permeation into the dermis is limited. Thus, the objective of this research is to formulate a nanoemulgel (NEG) containing a triple therapy of caffeine, aminophylline, and tretinoin as a topical anticellulite product to improve their skin permeation. Furthermore, the influence of microneedles (MNs) as skin pre-treatment on the permeation of the NEG was investigated. Experimental approach: Various nanoemulsion (NE) formulations were prepared using high-energy ultrasonication with different compositions and sonication amplitudes. Several characterisation tests were employed to select the optimum NE formulation. Then, the optimised NE formulation was incorporated with hyaluronic acid to prepare the NEG, which was, in turn, subjected to various evaluations. An ex vivo permeation study using human skin was performed for the NEG compared to a control preparation of plain gel. Additionally, a microneedling pen was applied as a skin pre-treatment at varying lengths prior to NEG application to examine its impact on the NEG’s permeation. Key results: The selected NEG has a homogenous and consistent texture with no coarse particles, a droplet size of 175.8 nm and polydispersity index (PDI) of 0.19, an optimum pH value of 5.28, high drug content of caffeine, aminophylline, and tretinoin (99.35, 98.48 and 98.05 %, respectively), high drug release values of approximately 100 % within 6 hours, appro-priate viscosity, minimum skin irritation, and adequate short-term stability. The ex vivo permeation study showed that caffeine, aminophylline, and tretinoin permeated more and deposited in the skin with higher percentages from the NEG than plain gel. This skin deposition within the dermis was increased by applying the microneedling pen at varying lengths of 0.5, 1, and 2 mm as a skin pre-treatment. Conclusion: This combined approach of NEG formulation containing a triple therapy of caffeine, aminophylline, and tretinoin, along with MNs application, has the potential to serve as a topical anticellulite product, reducing cellulite formation and improving skin appearance.

OPTIMIZATION OF LIQUIDSOAP FORMULATION

The quality of liquid soap for washing hands depends on its chemical composition, and it is evaluated by the physicochemical and functional characteristics of that product. The aim of the work is to prepare different series of liquid soap formulations by varying the concentrations of anionic and amphoteric surfactantsand sodium chloride, and to optimize the formulation. The effects of the optimization were evaluated based on the results of the analysis of the physico-chemical parameters of the prepared formulations, such as density, viscosity, surface tension and critical concentration of micelles. As amphoteric and anionic surfactant concentrations in liquid soap increase, density and viscosity values increase. The value of the surface tension decreases with the increase in the concentration of the surfactants present, with the amphoteric surfactant making a greater contribution to the decrease. Regardless of certain advantages that the anionic surfactant shows in relation to the amphoteric one, the best characteristics of the liquid soap are shown by the formulation thatcontains a combination of both used surfactants. The addition of NaCl to the liquid soap formulation has multiple significance, but also a different effect on the physical and chemical characteristics at lower and higher concentrations. Functional and some physico-chemical characteristics of liquid hand washing soap depend on the pH value of the formulation. As the pH value increases, the surface tension and CMC increase to certain values, so pH=5.5 is taken as the optimal pH value of liquid soap, as a compromise between the values of the measured characteristics and the pH value of human skin. This research showed that the formulation containing 5.4w/w%anionic surfactant, 1w/w%amphoteric surfactant and 4w/w% NaCl represents the optimal liquid soap formulation. KEYWORDS:liquid soap; content of liquid soap; surfactants; electrolyte in liquid soap; characteristics of liquid soap; optimization of formulation

Stability of immobilized L-arginine deiminase from Penicillium chrysogenum and evaluation of its anticancer activity

The aim of the present work was to immobilize L-arginine deiminase on suitable supports such as chitosan, alginate, and silica gel to study its stability. Additionally, the study aims to investigate the anticancer effects of the free purified enzyme on hepatocellular carcinoma (Hep-G2) and breast cancer (MCF-7) cell lines. L-arginine deiminase (ADI: EC 3.5.3.6) was immobilized on chitosan, Ca-alginate, and silica gel, with immobilization efficiencies of 89.0%, 72.8%, and 66.5%, respectively. The optimal immobilization time for the highest efficiency was 4 h. Increasing the concentration of glutaraldehyde improved the immobilization efficiency of ADI on chitosan. The chitosan-immobilized ADI retained about 45% of its activity after 8 cycles. The optimal pH values were 6 for the free purified ADI and 7 for the chitosan-immobilized ADI. The optimal temperature increased from 40 °C for the free enzyme to 45 °C after immobilization. The activation energies for the free and chitosan-immobilized enzymes were 71.335 kJ/mol and 64.011 kJ/mol, respectively. The Km values for the free and chitosan-immobilized ADI were 0.76 mM and 0.77 mM, respectively, while the Vmax values were 80.0 U/mg protein for the free ADI and 71.4 U/mg protein for the chitosan-immobilized ADI. After 30 days of storage at 4 °C, the residual activities were 40% for the free purified ADI and 84% for the chitosan-immobilized ADI. At 25 °C, the residual activities were 10% for the free ADI and 75% for the chitosan-immobilized ADI. The chitosan-immobilized ADI exhibited significantly higher stability against proteases such as pepsin and trypsin compared to the free enzyme. The purified ADI also demonstrated enhanced potential anticancer effects and significant cytotoxicity against the Hep-G2 and MCF-7 tumor cell lines compared to doxorubicin. These findings suggest that purified ADI has potential as an anticancer agent, though further in-depth studies are required.

Nitrogen-Rich Molybdenum Nitride with Intrinsic CD39 Nucleotidase Activity.

CD39 is one of the important nucleotidases to adjust extracellular adenosine triphosphate (ATP) and adenosine diphosphate (ADP) concentration. However, the enzyme mimics to simulate the activity of CD39 still remains to be explored. Herein nitrogen-rich molybdenum nitride (Mo5N6) nanosheets are explored to possess CD39-like activity, which are able to catalyze the hydrolysis of the high-energy phosphate bonds (HEPBs) in ATP and ADP but not the common phosphate bonds in adenosine monophosphate (AMP). The catalytic hydrolysis of the phosphate bond over Mo5N6-700 nanosheets is first investigated using para-nitrophenyl phosphate as the model substrate and then the CD39-like activity is further explored and verified by 31p NMR spectroscopy. Mo4+ on the surface of Mo5N6-700 nanosheets are the catalytic active sites. Using ATP as the model substrate, the Km and Vmax values of CD39-like activity at optimal pH 9.0 are 3.2µmol L-1 and 18.5µmol L-1 h-1, respectively. The CD39-like activity of Mo5N6-700 nanosheets enabled the down-regulation of intracellular ATP concentration to a larger degree for cancer cells than normal cells, which makes Mo5N6-700 nanosheets a potential therapeutic reagent for cancers.

Nitrilase GiNIT from Gibberella intermedia Efficiently Degrades Nitriles Derived from Rapeseed Meal Glucosinolate

Rapeseed meal is severely restricted in its utilization as unconventional animal feed due to anti-nutritive compounds, such as glucosinolate, that are degraded to toxic nitriles such as 3-butenenitrile and 4-pentenenitrile in animals. Few studies on nitrilases that can degrade glucosinolate-derived nitriles have been reported thus far. In the present study, a nitrilase gene GiNIT from Gibberella intermedia was over-expressed in Escherichia coli and the purified recombinant nitrilase rGiNIT showed specific activities of 134.48 U/mg and 122.16 U/mg when using 3-butenenitrile and 4-pentenenitrile as substrates at the optimal pH, 7.5, and temperature, 45 °C, which is the highest reported in the literature. The conversion of 3-butenenitrile and 4-pentenenitrile by rGiNIT reached 81.89% and 80.23% after hydrolysis for 15 min and 300 min, respectively. Site-directed mutagenesis and molecular docking analysis revealed that the catalytic ability of rGiNIT depended on the substrate binding pocket comprising 13 key amino acid residues. These results provide a potential enzyme resource for rapeseed meal detoxification and theoretical guidance for protein engineering.

The diagnostic role of Lactobacillus spp. as representatives of the normal microbiome of the lower urogenital tract

Currently, scientific knowledge about various Lactobacillus species, which are representatives of the resident flora of the vagina, is actively expanding. We know, lactobacilli are an integral part of the female genital tract. Currently, about 20 different types of lactobacilli are known. Most of the lactobacilli already studied contribute to maintaining vaginal health by providing protection from pathogenic microorganisms, the development of dysbiosis, pregnancy complications, including premature birth. The protective function is provided primarily by the formation of Dand L-forms of lactic acid, which maintains an optimal acidic pH, from the glycogen of the vaginal epithelium. Lactobacillus spp. also prevent adhesion and invasion of pathogens into epithelial cells, synthesize bacteriocins, and inhibit the release of proinflammatory cytokines. However, to date, there is already evidence that not all representatives of lactobacilli have a positive effect on the health of the female body. Thus, patients with the CSTIII morphotype, dominated by L. iners, are especially predisposed to the development of vaginal dysbiosis, and the dominance of L. acidophilus in patients is probably associated with infertility. Currently, there is no reliable evidence of the positive and/or negative effects of many lactobacilli on the female body, and existing studies on a number of bacteria are limited and contradictory. In this regard, it is relevant to further study the characteristics and properties of Lactobacillus spp., colonizing the vagina, for a more accurate understanding of the role of lactobacilli in the vagina and the application of the knowledge gained in clinical practice for the treatment and prevention of various disorders of the normal vaginal microbiome.

FeBTC MOF‐Derived Fe3O4@C Nanocomposite: Controlled Synthesis and Application as Potential Adsorbent for Rhodamine Dye Elimination From Wastewater

ABSTRACTThis study explores the controlled synthesis of a novel Fe3O4@C magnetic nanocomposite derived from FeBTC metal–organic framework (MOF) and its application as an efficient adsorbent for the removal of rhodamine dye from wastewater. The FeBTC MOF was first synthesized and then thermally decomposed in a controlled oxygen atmosphere at 375°C (1 h) to form the Fe3O4@C nanocomposite with a magnetic Fe3O4 core embedded in a porous carbon matrix. A comprehensive characterization of the nanocomposite was performed using x‐ray diffraction (XRD), transmission electron microscopy (TEM), and x‐ray photoelectron spectroscopy (XPS) to confirm the successful formation and to evaluate its structural and morphological properties. The morphological investigation revealed that the particles of Fe3O4 had a spherical shape with diameter of 10–15 nm. The carbon coating appeared as a thin amorphous layer surrounding the Fe3O4 nanoparticles. The adsorption capacity of Fe3O4@C for rhodamine B (RhB) dye was assessed under various conditions, including different pH values, contact times, initial dye concentrations, and temperatures. Complete dye removal was attained in 45 min using 50 mg of the nanocomposite and 50 mL of 5.0 ppm RhB at the optimum pH of 9.1. Under the same experimental conditions, the highest adsorption capacity of 13.0 mg/g was obtained, but using 15.0 mg of the nanocomposite. Fe3O4@C nanocomposite exhibits high adsorption efficiency, with a maximum removal capacity of 100%, which is clearly superior to many conventional adsorbents. This performance can be attributed to the synergistic effects of the magnetic Fe3O4 and the large surface area of the carbon matrix. Kinetic models were employed to understand the adsorption mechanism. The adsorption kinetics followed a pseudo‐second‐order model. The reusability of the adsorbent was tested over multiple cycles and showed a minimal loss of performance (drops to 93.0% after five removal cycles). The study demonstrates that the Fe3O4@C nanocomposite is a promising candidate for the effective removal of organic dyes from wastewater, offering potential benefits for environmental remediation and sustainable water management.

Cationic waste hemp fibers-based membrane: Case study of anionic pollutants removal through environmentally friendly processes

In this study, waste hemp fibers were transformed into cationically modified lignocellulosic adsorbent through a three-step process. First, a delignification/defibrillation pretreatment was performed, followed by quaternization of fibers using the synthesized ionic liquid chlorocholine chloride-urea (CCC-U). Pressure-assisted cross-linking of modified fibres, using a citric acid, produced new membrane (CCC-UHM). The removal of anionic dyes (Acid Yellow 36 (AY36), Congo Red (CR), Acid Green 25 (AG25), and Acid Blue 92 (AB92)), and oxyanions (As(V) and Cr(VI)) was tested in batch and column system. The structural characteristics and chemical properties of the syntesised materials were investigated by SEM, FTIR, Raman, XPS, XRD, specific density, porosity and point of zero charges analysis. The endothermic and spontaneous equilibration of the system resulted in high capacity (qm), i.e., 302.9 mg g−1 (AY36), 456.8 mg g−1 (CR), 812.8 mg g−1 (AG25), 587.6 mg g−1 (AB92), 107.9 mg g−1 (As(V)), and 67.84 mg g−1 (Cr(VI)) at 25 °C, using the Langmuir model. The optimum pH for the adsorption process was 7. The multi-cycle adsorption/desorption process was followed by either decolorization, using laccase from M. thermophile expressed in Aspergillus oryzae (Novozym 51,003® laccase) immobilized on amino-modified fibers as biocatalyst, or photocatalytic degradation, in the presence of zinc oxide. The high decolorization efficiency (96%) observed for AG25 and AB92 underscores the considerable potential of laccase immobilized preparations as sustainable and eco-friendly approach for treating dye-contaminated wastewater. Photodegradation process provided low environmental threat of processed water, and biodegradabilty of exhausted membrane confirmed the circularity of the developed technology with implemented principles of sustainability.

Integration of Coagulation–flocculation(with Natural Coagulant) to Constructed Wetlands for Color Removal from Tequila Vinasses

The aim of this study was to evaluate a natural coagulant, Moringa oleifera seeds (MOC), to reduce the color concentration in treated tequila vinasses (TVs). TV-A was the effluent of horizontal subsurface flow wetlands (HSSFW); TV-B was the effluent of vertical up-flow wetlands (VUFW); and TV-C was the effluent of vertical down-flow constructed wetlands (VDFW). Raw TVs were also with MOC. Jar tests were performed to find the optimal dose and pH value for apparent color (AC) removal. With the optimal dose and pH for each type of TV, tests were performed in triplicate to evaluate the removal of apparent color (AC), true color (TC), turbidity, total suspended solids (TSS), chemical oxygen demand (COD), and electrical conductivity (EC). For TV-A and TV-B, the optimal values were 1 g/L of MOC and pH 8, and the removals were 52%, 43%, 50% and 72% of AC, turbidity, TC, and TSS, respectively. For TV-C, the optimal values were 2.5 g/L and pH 5, with removals of 66%, 73%, and 98% for AC, TC, and TSS, respectively. For TV-D, the MOC had no coagulant effect in any of the experimental conditions evaluated, probably due to the high concentration of turbidity and TSS in the raw vinasses, which prevented the interaction between MOC and melanoidins. Deeper studies are required to understand and evaluate those factors that influence MOC efficiency so that the coagulation–flocculation process can be optimized.

Isolation, identification and optimization for tyrosinase production by banana peel waste for industrial application

The study aimed to isolate, purify and optimise tyrosinase from banana peel waste for industrial use. Tyrosinase was extracted from banana peel using phosphate buffer. Purification initiated with centrifugation followed by ammonium sulphate precipitation. Further purification and characterisation was done through gel filtration. Bradford assay was used to determine the protein concentration. Enzyme activity of each sample was measured using tyrosinase activity assay. The pH and temperature optimisation of tyrosinase were also obtained. Results indicated that fractions obtained through ammonium sulphate precipitation at 70% saturation showed more activity than that of crude extract and 35% saturated fractions. Gel filtration column results showed that fraction number 17 &18 have maximum activity. Tyrosinase showed maximum activity at pH 7.0; 37 °C. Comparison between industrially purified and lab-isolated enzyme showed that both have similar optimum pH and temperature. It can be concluded that banana peel can be a source for synthesis of tyrosinase.

Immobilization and characterization of β-galactosidase from Aspergillus oryzae in polyvinyl alcohol hydrogels.

One of the main goals of contemporary biotechnology has been the development of novel immobilized enzyme formulations. In the present study, the industrially important β-galactosidase was trapped in a polyvinyl alcohol (PVA) gel to immobilize it. The optimization of immobilization method and characterization of the immobilized enzyme were studied. The results were compared with free enzymes. The results indicate that the optimal temperature range for the enzyme to be at following immobilization is between 40°C and 50°C. At pH 7, the optimal pH, the activity increased, the Vmax value increased from 1.936 to 2.495 Umg‒1, and the Km value decreased from 4.861 to 0.982mM.Depending on how stable the immobilized enzyme when stored, β-galactosidases immobilized on PVA gels showed 52.87% activity at the end of the seventh week and 58.86% activity at the end of the fifth week. Their initial activity subsided after three reuses. The final result was 66%. Therefore, one may argue that it increases the catalytic effect of the enzyme. As a result, it has been found that immobilized β-galactosidase has more potent enzymatic properties than free β-galactosidase, which may make it more advantageous for industrial processes. Further studies could delve deeper into the mechanistic aspects of the immobilization process in an effort to improve optimization and tailor the immobilized enzyme to specific industrial needs.

Synthesis of Dispersed Magnetic Fe3O4 Nanohydrogel Based on Gelatine by Gamma Irradiation for Toxic Heavy Metals Removal

AbstractHeavy metals are among the problematic groups of contaminants. They are discharged from various industries. The wastewater disposed by heavy metals is causing major hazards to the environment. Different hydrogels based on Gelatin (gelt/AAm/EDTA) and nano- (Fe3O4/gelt/AAm/EDTA) were prepared by gamma radiation at 60 KGy and employed for heavy metals elimination. The structure and surface morphology of the manufactured hydrogels were confirmed with FTIR, X-ray, surface area, and SEM. The prepared hydrogels were characterized in terms of their gel content. The swelling properties were studied as a function of time. This research aims to investigate the adsorption properties of diverse hydrogels concerning heavy metal ions, specifically copper, cobalt, and nickel. The impact of key experimental factors, including initial metal concentration, temperature, time, and pH, was inspected via batch adsorption experiments utilizing atomic absorption spectroscopy. It was found that the adsorption of Cu+2‏, Co+2‏ and Ni+2‏ ions is pH-dependent, and the optimal pH for adsorption of Cu+2 is pH 4‏, Co+2 ‏is 5, and Ni+2‏ is 4. The highest metals removal was copper, nickel, and cobalt ions by nano (Fe3O4/gelt/AAm/EDTA) hydrogel with removal percent 98.5% for Cu+2, 96.8%for Ni+2, and 93.9%for Co+2. Graphical Abstract

Enhanced activity of split trehalase biosensors by interspecies domain combineering.

The split trehalase biosensor has potential as a versatile diagnostic technology. Split enzymes are engineered proteins, divided into inactive fragments, which can reassemble and regain activity when brought together by an analyte. The split TreA biosensor requires no sample processing and produces stable signals (in the form of glucose). Split trehalase reagents can function in blood, but periplasmic trehalase of E.coli requires blood acidification for maximal activity. The objective of this study was to obtain split trehalase with near physiological pH optimum. For this purpose, periplasmic trehalases of Cellvibrio spp. with higher activity at neutral pH, were split in analogy with the E. coli TreA into hood and catalytic domains. However, these split trehalases displayed self-complementation due to spontaneous reassembly. In contrast, when catalytic domains of Cellvibrio trehalases were combined with E.coli hood domains, these hybrids displayed conditional complementation capacity when split trehalase fragments fused to immunoglobulin-binding protein G (STIGA) were used to quantify immunoglobulin concentrations. Other hybrid combinations of Cellvibrio spp. had increased activity compared to the cognate pairs, albeit with strong self-complementation. A mutagenesis analysis of residues responsible for self-complementation led to uncoupling of self-complementation from allostery. The Michaelis-Menten kinetics of Cellvibrio enzymes and fragment pairs confirmed improved activity of a mutated hybrid pair of Cellvibrio hood and catalytic domains at physiological pH. In conclusion, the improvements in pH optimum and activity, demonstrated with STIGA, can now be leveraged to enhance other variations of the split trehalase biosensor platform, broadening its utility for testing clinical samples.

Phosphorus removal and recovery from water and wastewater by the struvite crystallization

The precipitation of phosphorus naturally present in water, in the form of struvite, constitutes an interesting alternative for the phosphate water treatment. In this context, the main objective of the present study is to follow the crystallization of struvite, in a stirred tank, from real phosphated water (wastewater and natural water) at 25°C and at optimum pH 8.5 and to study the effect of environmental conditions on the crystallization stages (nucleation and crystal growth) and the morphology of struvite crystals.Various analytical methods (spectrophotometry, FTIR, SEM and XRD) were used to characterize the solid and liquid phases. In the light of the results obtained in this investigation, it appears that the precipitates formed in all the samples of treated waters were identified as ammonium magnesium phosphate (i.e. struvite). The precipitation of struvite in water allowed a significant elimination of phosphorus (up to 70%). On the other hand, the SEM analysis was able to highlight the presence of large clusters of large struvite crystals up to 146.8µm, as in the case of the precipitation of struvite with wastewater, where the conversion rate was the highest. The supersaturation ratio is the most important factor influencing the crystallization process.

Cloning, Expression, Purification and Enzymatic Characterization of Low-temperature Cholesterol Esterase from Marine Panthenia Agglutinosa

BACKGROUND: The low-temperature cholesterol esterase is primarily used in industries such as papermaking and healthcare. OBJECTIVE: To discover a microorganism with high cholesterol esterase activity and tolerance to low temperatures, leading to the promotion of the sustainable utilization of marine cold-adapted microbial resources and fostering industrial development. MATERIALS AND METHODS: This study isolated a strain producing low-temperature cholesterol esterase from marine samples in the China Bohai Sea. The strain was identified through 16S rDNA sequencing and named Panthenia agglutinosa Y03. The cholesterol esterase gene (PaChe) from P. agglutinosa Y03 was cloned and heterologously expressed in Escherichia coli, and the recombinant enzyme PaChe was purified and characterized. The structure of PaChe was predicted using AlphaFold2, and molecular docking was performed with cholesterol linoleate as the ligand. RESULTS: The enzyme protein has a molecular weight of 56.35 KDa, a theoretical pI of 7.24, lacks a signal peptide, and exhibits structural features of the α/β hydrolase superfamily protein. The concentration of the purified PaChe is 0.5 mg/mL, with a specific activity of 42.7 U/mg. The optimal working temperature is 30 °C, and the enzyme retains activity at 4 °C , demonstrating weaker thermal stability. The optimal pH is 7, and the enzyme maintains over 70% activity at pH 9. Na +, Ca 2+ and Mg 2+ are the primary activators, while Ba 2+, Fe 2+, Mn 2+, Cu 2+ and chemical agents such as SDS as inhibitors, with Cu2+ exhibiting particularly significant inhibitory effects. CONCLUSION: This study establishes the theoretical groundwork for the development and utilization of a novel lowtemperature cholesterol esterase.

Trehalose-6-phosphate phosphatase expression and enzymatic properties of Fusariumgraminearum

This study presents an exhaustive characterization of the enzymatic attributes and structural properties of trehalose-6-phosphate phosphatase (TPP) derived from Fusarium graminearum. Enzyme activity was evaluated through a meticulously designed enzymatic assay. The findings indicate that the molecular weight of the enzyme is approximately 99.8 kDa, with an optimal reaction temperature and pH of 40 °C and 6.5, respectively. Magnesium ions (Mg2+) markedly enhance the enzymatic activity, resulting in a specific activity of 1.795 U/μg. Kinetic analysis revealed a Km value of 0.96 μmol/L and a Vmax of 15.79 μmol/L/min. Subsequent computational analysis elucidated the three-dimensional architecture of the enzyme and identified the binding site for the substrate trehalose-6-phosphate (T6P). T6P was found to form hydrogen bonds with TPP at residues Lys754, Arg720, His665, Glu758, and Asn756. Additionally, hydrophobic interactions were observed between T6P and residues Phe802, Ile610, Asp801, Pro752, and Gly753. The binding energy calculated for the T6P-TPP complex stood at −5.7 kcal/mol.