Break oily water emulsion during petroleum enhancing production processes using green approach for the synthesis of SnCuO@FeO nanocomposite from microorganisms.

The aim of this work was to synthesize a green nanoparticle SnCuO@FeO nanocomposite core-shell to break oily water emulsions during petroleum-enhancing production processes as an alternative to chemical and physical processes. In this study, eight bacterial isolates (MHB1-MHB8) have been isolated from tree leaves, giant reeds, and soil samples. The investigation involved testing bacterial isolates for their ability to make FeO nanoparticles and choosing the best producers. The selected isolate (MHB5) was identified by amplification and sequencing of the 16S rRNA gene as Bacillus paramycoides strain OQ878685. MHB5 produced the FeO nanoparticles with the smallest particle size (78.7 nm) using DLS. XRD, FTIR, and TEM were used to characterize the biosynthesized nanoparticles. The jar experiment used SnCuO@FeO with different ratios of Sn to CuO (1:1, 2:1, and 3:1) to study the effect of oil concentration, retention time, and temperature. The most effective performance was observed with a 1:1 ratio of Sn to CuO, achieving an 85% separation efficiency at a concentration of 5 mg/L, for a duration of 5 min, and at a temperature of 373 K. Analysis using kinetic models indicates that the adsorption process can be accurately described by both the pseudo-first-order and pseudo-second-order models. This suggests that the adsorption mechanism likely involves a combination of film diffusion and intraparticle diffusion. Regarding the adsorption isotherm, the Langmuir model provides a strong fit for the data, while the D-R model indicates that physical interactions primarily govern the adsorption mechanism. Thermodynamic analysis reveals a ∆H value of 18.62 kJ/mol, indicating an exothermic adsorption process. This suggests that the adsorption is a favorable process, as energy is released during the process. Finally, the synthesized green SnCuO@FeO nanocomposite has potential for use in advanced applications in the oil and gas industry to help the industry meet regulatory compliance, lower operation costs, reduce environmental impact, and enhance production efficiency.

Organic Supplementation of Vaccinium corymbosum Micropropagation Media.

The best Vaccinium corymbosum plant growth under in vitro conditions can be achieved by using the right composition and pH of the medium. For the initial phase of in vitro culture, a combination of cytokinins-mostly zeatin-can usually be used. Organic supplementation of the medium enables the use of a replacement for the expensive natural cytokinin used in micropropagation of highbush blueberry. This chapter describes the experiments with silicon Hydroplus™ Actisil (Si), coconut water (CW), and different pH (5.0; 5.5, and 6.0) as a stress factor. The addition of 200 mg dm-3 silicon solution and 15% coconut water strongly stimulated highbush blueberry plant growth in vitro. Moreover, silicon solution benefits the negative effects of higher pH of the medium used for micropropagation of V. corymbosum. Maximum vegetative development of blueberry explants was obtained at pH 5.

Comprehensive assessment of copper's effect on marine organisms under ocean acidification and warming in the 21st century.

Copper (Cu) has sparked widespread global concern as one of the most hazardous metals to aquatic animals. Ocean acidification (OA) and warming (OW) are expected to alter copper's bioavailability based on pH and temperature-sensitive effects; research on their effects on copper on marine organisms is still in its infancy. Therefore, under representative concentration pathways (RCP) 2.6, 4.5, and 8.5, we used the multiple linear regression-water quality criteria (MLR-WQC) method to assess the effects of OA and OW on the ecological risk posed by copper in the Ocean of East China (OEC), which includes the Bohai Sea, Yellow Sea, and East China Sea. The results showed that there was a positive correlation between temperature and copper toxicity, while there was a negative correlation between pH and copper toxicity. The short-term water quality criteria (WQC) values were 1.53, 1.41, 1.30 and 1.13 µg·L-1, while the long-term WQC values were 0.58, 0.48, 0.40 and 0.29 µg·L-1 for 2020, 2099-RCP2.6, 2099-RCP4.5 and 2099-RCP8.5, respectively. Cu in the OEC poses a moderate ecological risk. Under the current copper exposure situation, strict intervention (RCP2.6) only increases the ecological risk of copper exposure by 20 %, and no intervention (RCP8.5) will increase the ecological risk of copper exposure by nearly double. The results indicate that intervention on carbon emissions can slow down the rate at which OA and OW worsen the damage copper poses to marine creatures. This study can provide valuable information for a comprehensive understanding of the combined impacts of climate change and copper on marine organisms.

Carbon content and other soil properties of near-surface peats before and after peatland restoration.

Peatland restoration usually aims at restarting the peatlands' function to store carbon within peat. The soil properties of the near-surface peat can give a first understanding of this process. Therefore, we sampled pH value, total organic carbon content (TOC), total nitrogen content (TN), C/N ratio as well as dry bulk density (BD), and describe the structure of near-surface peats in six restored fens in North-East Germany before (2002-2004) and after (2019-2021) restoration. Before restoration, the study sites showed peat degradation to various extents in their near-surface peats. pH values remained relatively stable over time. Comparing the degraded peat horizons, TOC increased significantly in four study sites, ranging from 35.7% to 47.8% in 2002-2004 and from 42.5% to 54.0% in 2019-2021. TN varied from 1.5% to 3.5% in 2002-2004 and from 1.8% to 3.2% in 2019-2021, but changes were only significant in one site, showing a slight decrease. In three sites, the increase in C/N ratio was significant, indicating lower nutrient availability. BD ranged from 0.08 to 0.48 g/cm3 in 2002-2004 and from 0.10 to 0.16 g/cm3 in 2019-2021, decreasing significantly in four sites. The structure of the degraded peat horizons changed after restoration to a more homogenous, sludge mass with larger re-aggregates. In three sites, new peat moss peat layers above the degraded soil horizon were present in 2019-2021, with a mean thickness of 6.8 to 36.1 cm. The structure was comparable to typical, slightly decomposed peat moss peat. Our findings suggest that within about 17 years after fen restoration, and thereby a water table rise close to surface, TOC of the near-surface peats increased to values that are typical for undisturbed peatlands. This indicates that restoration can lead to the re-establishment of peatlands as potential carbon sinks, with TOC within the near-surface peat as one key factor in this process. Further, we assume that the decrease in nutrient availability, decrease of BD, and new, undisturbed peat layers can favor the establishment of mire-specific biodiversity and support ecosystem services similar to near-natural mires.

Ambient carbon dioxide concentration correlates with SARS-CoV-2 aerostability and infection risk.

An improved understanding of the underlying physicochemical properties of respiratory aerosol that influence viral infectivity may open new avenues to mitigate the transmission of respiratory diseases such as COVID-19. Previous studies have shown that an increase in the pH of respiratory aerosols following generation due to changes in the gas-particle partitioning of pH buffering bicarbonate ions and carbon dioxide is a significant factor in reducing SARS-CoV-2 infectivity. We show here that a significant increase in SARS-CoV-2 aerostability results from a moderate increase in the atmospheric carbon dioxide concentration (e.g. 800 ppm), an effect that is more marked than that observed for changes in relative humidity. We model the likelihood of COVID-19 transmission on the ambient concentration of CO2, concluding that even this moderate increase in CO2 concentration results in a significant increase in overall risk. These observations confirm the critical importance of ventilation and maintaining low CO2 concentrations in indoor environments for mitigating disease transmission. Moreover, the correlation of increased CO2 concentration with viral aerostability need to be better understood when considering the consequences of increases in ambient CO2 levels in our atmosphere.

A pH-responsive nanoplatform with dual-modality imaging for enhanced cancer phototherapy and diagnosis of lung metastasis.

To address the limitations of traditional photothermal therapy (PTT)/ photodynamic therapy (PDT) and real-time cancer metastasis detection, a pH-responsive nanoplatform (NP) with dual-modality imaging capability was rationally designed. Herein, 1 H,1 H-undecafluorohexylamine (PFC), served as both an oxygen carrier and a 19F magnetic resonance imaging (MRI) probe, and photosensitizer indocyanine green (ICG) were grafted onto the pH-responsive peptide hexahistidine (H6) to form H6-PFC-ICG (HPI). Subsequently, the heat shock protein 90 inhibitor, gambogic acid (GA), was incorporated into hyaluronic acid (HA) modified HPI (HHPI), yielding the ultimate HHPI@GA NPs. Upon self-assembly, HHPI@GA NPs passively accumulated in tumor tissues, facilitating oxygen release and HA-mediated cell uptake. Once phagocytosed by lysosomes, protonation of H6 was triggered due to the low pH, resulting in the release of GA. With near-infrared laser irradiation, GA-mediated decreased HSP90 expression and PFC-mediated increased ROS generation amplified the PTT/PDT effect of HHPI@GA, leading to excellent in vitro and in vivo anticancer efficacies. Additionally, the fluorescence and 19F MRI dual-imaging capabilities of HHPI@GA NPs enabled effective real-time primary cancer and lung metastasis monitoring. This work offers a novel approach for enhanced cancer phototherapy, as well as precise cancer diagnosis.

Microbiome-derived acidity protects against microbial invasion in Drosophila.

Microbial invasions underlie host-microbe interactions resulting in pathogenesis and probiotic colonization. In this study, we explore the effects of the microbiome on microbial invasion in Drosophila melanogaster. We demonstrate that gut microbes Lactiplantibacillus plantarum and Acetobacter tropicalis improve survival and lead to a reduction in microbial burden during infection. Using a microbial interaction assay, we report that L. plantarum inhibits the growth of invasive bacteria, while A. tropicalis reduces this inhibition. We further show that inhibition by L. plantarum is linked to its ability to acidify its environment via lactic acid production by lactate dehydrogenase, while A. tropicalis diminishes the inhibition by quenching acids. We propose that acid from the microbiome is a gatekeeper to microbial invasions, as only microbes capable of tolerating acidic environments can colonize the host. The methods and findings described herein will add to the growing breadth of tools to study microbe-microbe interactions in broad contexts.

High Charge Density in Peptide Dendrimers is Required to Destabilize Membranes: Insights into Endosome Evasion.

Peptide dendrimers are a type of branched, symmetric, and topologically well-defined molecule that have already been used as delivery systems for nucleic acid transfection. Several of the most promising sequences showed high efficiency in many key steps of transfection, namely, binding siRNA, entering cells, and evading the endosome. However, small changes to the peptide dendrimers, such as in the hydrophobic core, the amino acid chirality, or the total available charges, led to significantly different experimental results with unclear mechanistic insights. In this work, we built a computational model of several of those peptide dendrimers (MH18, MH13, and MH47) and some of their variants to study the molecular details of the structure and function of these molecules. We performed CpHMD simulations in the aqueous phase and in interaction with a lipid bilayer to assess how conformation and protonation are affected by pH in different environments. We found that while the different peptide dendrimer sequences lead to no substantial structural differences in the aqueous phase, the total charge and, more importantly, the total charge density are key for the capacity of the dendrimer to interact and destabilize the membrane. These dendrimers become highly charged when the pH changes from 7.5 to 4.5, and the presence of a high charge density, which is decreased for MH47 that has four fewer titratable lysines, is essential to trigger membrane destabilization. These findings are in excellent agreement with the experimental data and help us to understand the high efficiency of some dendrimers and why the dendrimer MH47 is unable to complete the transfection process. This evidence provides further understanding of the mode of action of these peptide dendrimers and will be pivotal for the future design of new sequences with improved transfection capabilities.

A mixed-mode reversed-phase/strong-anion-exchange stationary phase: Analyte-retention stability and application in the analysis of nonsteroidal anti-inflammatory drugs.

Mixed-mode reversed-phase/anion-exchange chromatography (RP/AEX) is an effective method for the chromatographic analysis of acidic drugs because it combines reversed-phase chromatography (RP) with anion-exchange chromatography (AEX). However, the result repeatability for the RP/AEX analysis of acidic drugs is frequently compromised by the detrimental effects of residual silanol groups in an RP/AEX stationary phase on peak separation and analyte retention. In this study, an RP/weak-AEX stationary phase with amino anion-exchange groups, Sil-AA, was prepared. Subsequently, an RP/strong-AEX stationary phase, Sil-PBQA, was prepared by replacing the amino groups in Sil-AA with a benzene ring and a benzyl-containing quaternary ammonium salt. The chromatographic behaviors of Sil-PBQA and Sil-AA were compared, and the effect of residual silanol groups on the chromatographic behavior of an RP/AEX stationary phase was evaluated. Residual silanol groups not only caused additional electrostatic interactions for acidic analytes, but also competed with the analytes for the anion-exchange sites in an RP/AEX stationary phase. The effects of different salt-containing mobile-phase systems on the analyte-retention behavior of Sil-PBQA were investigated to develop a method that enhanced the repeatability of the RP/AEX acidic-analyte-analysis results obtained using Sil-PBQA and facilitated the separation of nonsteroidal anti-inflammatory drugs on Sil-PBQA. The ideas presented in this paper can improve the separation of peaks and repeatability of results in the RP/AEX analysis of acidic drugs.

Multiparameter Sensing of Oxygen and pH at Biological Interfaces via Hyperspectral Imaging of Luminescent Sensor Nanoparticles.

Chemical dynamics in biological samples are seldom stand-alone processes but represent the outcome of complicated cascades of interlinked reaction chains. In order to understand these processes and how they correlate, it is important to monitor several parameters simultaneously at high spatial and temporal resolution. Hyperspectral imaging is a promising tool for this, as it provides broad-range spectral information in each pixel, enabling the use of multiple luminescent indicator dyes, while simultaneously providing information on sample structures and optical properties. In this study, we first characterized pH- and O2-sensitive indicator dyes incorporated in different polymer matrices as optical sensor nanoparticles to provide a library for (hyperspectral) chemical imaging. We then demonstrate the successful combination of a pH-sensitive indicator dye (HPTS(DHA)3), an O2-sensitive indicator dye (PtTPTBPF), and two reference dyes (perylene and TFPP), incorporated in polymer nanoparticles for multiparameter chemical imaging of complex natural samples such as green algal biofilms (Chlorella sorokiniana) and seagrass leaves (Zostera marina) with high background fluorescence. We discuss the system-specific challenges and limitations of our approach and further optimization possibilities. Our study illustrates how multiparameter chemical imaging with hyperspectral read-out can now be applied on natural samples, enabling the alignment of several chemical parameters to sample structures.

Affinity purification/immobilization of poly histidine-tagged proteins by nickel-functionalized porous chitosan membranes.

Although immobilized metal ion affinity chromatography (IMAC) is one of the most effective methods for purifying his-tagged proteins, it has limitations such as expensive commercial resins and non-specific binding of unwanted proteins to the nickel immobilized on the resin. In this study, biocompatible chitosan and porous chitosan membranes as alternative resins were synthesized for protein immobilization and purification, but finally porous chitosan membrane was selected due to its higher porosity and consequently higher nickel adsorption. Once the membrane was functionalized with nickel ions and its metal adsorption confirmed by EDS and ICP methods, it was used to immobilize and purify recombinant ß-NGF as a protein model with his-tag tail in batch-fashion. Protein binding and purification were also approved by FTIR and UV-Vis spectroscopy and SDS-PAGE technique. Our results indicated that the protein of interest could bind to the nickel-functionalized porous chitosan membrane with high efficiency at pH=7. Furthermore, for protein purification, the pH value of 6 and an imidazole concentration of 750 mM were suggested for the final elution buffer. In conclusion, nickel-functionalized porous chitosan membrane could be a suitable alternative to IMAC for low cost and specific protein immobilization and purification.

Redefined ion association constants have consequences for calcium phosphate nucleation and biomineralization.

Calcium orthophosphates (CaPs), as hydroxyapatite (HAP) in bones and teeth are the most important biomineral for humankind. While clusters in CaP nucleation have long been known, their speciation and mechanistic pathways to HAP remain debated. Evidently, mineral nucleation begins with two ions interacting in solution, fundamentally underlying solute clustering. Here, we explore CaP ion association using potentiometric methods and computer simulations. Our results agree with literature association constants for Ca2+ and H2PO4-, and Ca2+ and HPO42-, but not for Ca2+ and PO43- ions, which previously has been strongly overestimated by two orders of magnitude. Our data suggests that the discrepancy is due to a subtle, premature phase separation that can occur at low ion activity products, especially at higher pH. We provide an important revision of long used literature constants, where association of Ca2+ and PO43- actually becomes negligible below pH 9.0, in contrast to previous values. Instead, [CaHPO4]0 dominates the aqueous CaP speciation between pH ~6-10. Consequently, calcium hydrogen phosphate association is critical in cluster-based precipitation in the near-neutral pH regime, e.g., in biomineralization. The revised thermodynamics reveal significant and thus far unexplored multi-anion association in computer simulations, constituting a kinetic trap that further complicates aqueous calcium phosphate speciation.

Bioresorbable, wireless, passive sensors for continuous pH measurements and early detection of gastric leakage.

Continuous monitoring of biomarkers at locations adjacent to targeted internal organs can provide actionable information about postoperative status beyond conventional diagnostic methods. As an example, changes in pH in the intra-abdominal space after gastric surgeries can serve as direct indicators of potentially life-threatening leakage events, in contrast to symptomatic reactions that may delay treatment. Here, we report a bioresorbable, wireless, passive sensor that addresses this clinical need, designed to locally monitor pH for early detection of gastric leakage. A pH-responsive hydrogel serves as a transducer that couples to a mechanically optimized inductor-capacitor circuit for wireless readout. This platform enables real-time monitoring of pH with fast response time (within 1 hour) over a clinically relevant period (up to 7 days) and timely detection of simulated gastric leaks in animal models. These concepts have broad potential applications for temporary sensing of relevant biomarkers during critical risk periods following diverse types of surgeries.

Deciphering the importance of culture pH on CD22 CAR T-cells characteristics.

BACKGROUND: Chimeric antigen receptor (CAR) T-cells have demonstrated significant efficacy in targeting hematological malignancies, and their use continues to expand. Despite substantial efforts spent on the optimization of protocols for CAR T-cell manufacturing, critical parameters of cell culture such as pH or oxygenation are rarely actively monitored during cGMP CAR T-cell generation. A comprehensive understanding of the role that these factors play in manufacturing may help in optimizing patient-specific CAR T-cell therapy with maximum benefits and minimal toxicity. METHODS: This retrospective study examined cell culture supernatants from the manufacture of CAR T-cells for 20 patients with B-cell malignancies enrolled in a phase 1/2 clinical trial of anti-CD22 CAR T-cells. MetaFLEX was used to measure supernatant pH, oxygenation, and metabolites, and a Bio-Plex assay was used to assess protein levels. Correlations were assessed between the pH of cell culture media throughout manufacturing and cell proliferation as well as clinical outcomes. Next-generation sequencing was conducted to examine gene expression profiles of the final CAR T-cell products. RESULTS: A pH level at the lower range of normal at the beginning of the manufacturing process significantly correlated with measures of T-cell expansion and metabolism. Stable or rising pH during the manufacturing process was associated with clinical response, whereas a drop in pH was associated with non-response. CONCLUSIONS: pH has potential to serve as an informative factor in predicting CAR T-cell quality and clinical outcomes. Thus, its active monitoring during manufacturing may ensure a more effective CAR T-cell product.

Effects of soil pH on the growth, soil nutrient composition, and rhizosphere microbiome of Ageratina adenophora.

Ageratina adenophora is an invasive weed species found in many countries. Methods to control the spread of this weed have been largely unsuccessful. Soil pH is the most important soil factor affecting the availability of nutrients for plant and impacting its growth. Understanding the mechanisms of the influence of soil pH on the growth of A. adenophora may help to develop effective control measures. In this study, we artificially changed the soil pH in pot experiments for A. adenophora. We studied the effects of acidic (pH 5.5), weakly acidic (pH 6.5), neutral (pH 7.2), and alkaline (pH 9.0) soils on the growth, availability of soil nutrients, activity of antioxidant enzymes, levels of redox markers in the leaves, and the structure and diversity of the rhizosphere microbiome. Soil with a pH 7.2 had a higher (47.8%) below-ground height versus soils of pH 5.5 at day 10; plant had a higher (11.3%) above-ground height in pH 7.2 soils than pH 9.0 soils at day 90; no differences in the fresh and dry weights of its above- and belowground parts, plant heights, and root lengths were observed in plants growing in acid, alkaline, or neutral pH soil were observed at day 180. Correspondingly, the antioxidant enzymes SOD (superoxide dismutase), POD (peroxidase), CAT (catalase) and redox markers GSH (glutathione) and MDA (malondialdehyde) were measured in the leaves. Significant differences existed in the activities of CAT and the levels of GSH between those growing in acidic and alkaline soils and those in neutral pH soil at day 90; however, only lower (36.8%) CAT activities in those grown at pH 5.5 than those grown at pH 7.2 were found at day 180. Similarly, significant differences in available P (16.89 vs 3.04 mg Kg-1) and total K (3.67 vs 0.96 mg Kg-1), total P (0.37 vs 0.25 g Kg-1) and total N (0.45 vs 1.09 g Kg-1) concentrations were found between the rhizosphere soils of A. adenophora grown at pH 9.0 and 7.2 at day 90; no such differences were seen at day 180. High throughput analyses of the 16S rRNA and ITS fragments showed that the rhizosphere microbiome diversity and composition under different soil pH conditions changed over 180 days. The rhizosphere microbiomes differed in diversity, phylum, and generic composition and population interactions under acid and alkaline conditions versus those grown in neutral soils. Soil pH had a greater impact on the diversity and composition of the prokaryotic rhizosphere communities than those of the fungal communities. A. adenophora responded successfully to pH stress by changing the diversity and composition of the rhizosphere microbiome to maintain a balanced nutrient supply to support its normal growth. The unusual pH tolerance of A. adenophora may be one crucial reason for its successful invasion. Our results suggest that attempts use soil pH to control its invasion by changing the soil pH (for example, using lime) will fail.

Evaluation of toothpastes for treating root carious lesions - a laboratory-based pilot study.

BACKGROUND: Root caries is preventable and can be arrested at any stage of disease development. The aim of this study was to investigate the potential mineral exchange and fluorapatite formation within artificial root carious lesions (ARCLs) using different toothpastes containing 5,000 ppm F, 1,450 ppm F or bioactive glass (BG) with 540 ppm F. MATERIALS AND METHODS: The crowns of each extracted sound tooth were removed. The remaining roots were divided into four parts (n = 12). Each sample was randomly allocated into one of four groups: Group 1 (Deionised water); Group 2 (BG with 540 ppm F); Group 3 (1,450 ppm F) and Group 4 (5,000 ppm F). ARCLs were developed using demineralisation solution (pH 4.8). The samples were then pH-cycled in 13 days using demineralisation solution (6 h) and remineralisation solution (pH 7) (16 h). Standard tooth brushing was carried out twice a day with the assigned toothpaste. X-ray Microtomography (XMT) was performed for each sample at baseline, following ARCL formation and after 13-day pH-cycling. Scanning Electron Microscope (SEM) and 19F Magic angle spinning nuclear magnetic resonance (19F-MAS-NMR) were also performed. RESULTS: XMT results showed that the highest mineral content increase (mean ± SD) was Group 4 (0.09 ± 0.05), whilst the mineral content decreased in Group 1 (-0.08 ± 0.06) after 13-day pH-cycling, however there was evidence of mineral loss within the subsurface for Groups 1, 3 and 4 (p < 0.05). SEM scans showed that mineral contents within the surface of dentine tubules were high in comparison to the subsurface in all toothpaste groups. There was evidence of dentine tubules being either partially or completely occluded in toothpaste groups. 19F-MAS-NMR showed peaks between - 103 and - 104ppm corresponding to fluorapatite formation in Groups 3 and 4. CONCLUSION: Within the limitation of this laboratory-based study, all toothpastes were potentially effective to increase the mineral density of artificial root caries on the surface, however there was evidence of mineral loss within the subsurface for Groups 1, 3 and 4.

Tunable Oxidized-Chitin Hydrogels with Customizable Mechanical Properties by Metal or Hydrogen Ion Exposure.

This study focuses on the optimization of chitin oxidation in C6 to carboxylic acid and its use to obtain a hydrogel with tunable resistance. After the optimization, water-soluble crystalline ß-chitin fibrils (ß-chitOx) with a degree of functionalization of 10% were obtained. Diverse reaction conditions were also tested for α-chitin, which showed a lower reactivity and a slower reaction kinetic. After that, a set of hydrogels was synthesized from ß-chitOx 1 wt.% at pH 9, inducing the gelation by sonication. These hydrogels were exposed to different environments, such as different amounts of Ca2+, Na+ or Mg2+ solutions, buffered environments such as pH 9, PBS, pH 5, and pH 1, and pure water. These hydrogels were characterized using rheology, XRPD, SEM, and FT-IR. The notable feature of these hydrogels is their ability to be strengthened through cation chelation, being metal cations or hydrogen ions, with a five- to tenfold increase in their storage modulus (G'). The ions were theorized to alter the hydrogen-bonding network of the polymer and intercalate in chitin's crystal structure along the a-axis. On the other hand, the hydrogel dissolved at pH 9 and pure water. These bio-based tunable hydrogels represent an intriguing material suitable for biomedical applications.

Association between sleep pattern, salivary cariogenic bacteria and fungi populations, pH and buffering capacity in children: A comparative study.

BACKGROUND: Sleep quality has a significant impact on a child's health and is linked to oral and systemic diseases. It affects the circadian rhythm, which plays a crucial role in regulating the balance of the endocrine and hormonal systems. Current research has focused on exploring its role in the development of caries, which is influenced by inherent oral factors such as the composition of the oral microbiome and pH levels. OBJECTIVES: This study aimed to investigate the relationship between bacterial population, pH, and buffering properties of saliva and sleep patterns in 8- to 12-year-old children. MATERIAL AND METHODS: This cross-sectional study was conducted on 85 elementary school children aged 8-12 years. After obtaining written consent, non-stimulating saliva samples were collected using the spitting method. The participants' sleep pattern information was obtained with the use of the Persian version of the Children's Sleep Habits Questionnaire (CSHQ). Based on the results of the CSHQ, the participants were divided into 2 groups: those with appropriate sleep patterns; and those with inappropriate sleep patterns. The study compared the bacterial population of Streptococcus mutans, Lactobacillus spp. and Candida albicans, as well as the buffering capacity and pH of the saliva between the 2 groups. The statistical analysis employed the χ2 test, the independent samples t-test and Spearman's correlation. RESULTS: The group with inappropriate sleep patterns had significantly lower pH and buffering capacity (p < 0.001) and significantly higher colony counts of Lactobacillus and S. mutans (p < 0.001 and p = 0.012, respectively). There was no association between C. albicans and sleep patterns (p = 0.121). CONCLUSIONS: Inappropriate sleep patterns increase the population of caries-causing bacteria and reduce salivary pH and buffering capacity. This can be a significant factor in the development of dental caries in children aged 8-12 years.

High-level production of chitinase by multi-strategy combination optimization in Bacillus licheniformis.

In view of the extensive potential applications of chitinase (ChiA) in various fields such as agriculture, environmental protection, medicine, and biotechnology, the development of a high-yielding strain capable of producing chitinase with enhanced activity holds significant importance. The objective of this study was to utilize the extracellular chitinase from Bacillus thuringiensis as the target, and Bacillus licheniformis as the expression host to achieve heterologous expression of ChiA with enhanced activity. Initially, through structural analysis and molecular dynamics simulation, we identified key amino acids to improve the enzymatic performance of chitinase, and the specific activity of chitinase mutant D116N/E118N was 48% higher than that of the natural enzyme, with concomitant enhancements in thermostability and pH stability. Subsequently, the expression elements of ChiA(D116N/E118N) were screened and modified in Bacillus licheniformis, resulting in extracellular ChiA activity reached 89.31 U/mL. Further efforts involved the successful knockout of extracellular protease genes aprE, bprA and epr, along with the gene clusters involved in the synthesis of by-products such as bacitracin and lichenin from Bacillus licheniformis. This led to the development of a recombinant strain, DW2△abelA, which exhibited a remarkable improvement in chitinase activity, reaching 145.56 U/mL. To further improve chitinase activity, a chitinase expression frame was integrated into the genome of DW2△abelA, resulting in a significant increas to 180.26 U/mL. Optimization of fermentation conditions and medium components further boosted shake flask enzyme activity shake flask enzyme activity, achieving 200.28 U/mL, while scale-up fermentation experiments yielded an impressive enzyme activity of 338.79 U/mL. Through host genetic modification, expression optimization and fermentation optimization, a high-yielding ChiA strain was successfully constructed, which will provide a solid foundation for the extracellular production of ChiA.

Effect of Ba2+ on the biomineralization of Ca2+ and Mg2+ ions induced by Bacillus licheniformis.

The effect of barium ions on the biomineralization of calcium and magnesium ions is often overlooked when utilizing microbial-induced carbonate precipitation technology for removing barium, calcium, and magnesium ions from oilfield wastewater. In this study, Bacillus licheniformis was used to bio-precipitate calcium, magnesium, and barium ions. The effects of barium ions on the physiological and biochemical characteristics of bacteria, as well as the components of extracellular polymers and mineral characteristics, were also studied in systems containing coexisting barium, calcium, and magnesium ions. The results show that the increasing concentrations of barium ions decreased pH, carbonic anhydrase activity, and concentrations of bicarbonate and carbonate ions, while it increased the contents of humic acids, proteins, polysaccharides, and DNA in extracellular polymers in the systems containing all three types of ions. With increasing concentrations of barium ions, the content of magnesium within magnesium-rich calcite and the size of minerals precipitated decreased, while the full width at half maximum of magnesium-rich calcite, the content of O-C=O and N-C=O, and the diversity of protein secondary structures in the minerals increased in systems containing all three coexisting ions. Barium ions does inhibit the precipitation of calcium and magnesium ions, but the immobilized bacteria can mitigate the inhibitory effect. The precipitation ratios of calcium, magnesium, and barium ions reached 81-94%, 68-82%, and 90-97%. This research provides insights into the formation of barium-enriched carbonate minerals and offers improvements for treating oilfield wastewater.