Elemental mercury (Hg0) removal from coal syngas using magnetic tea-biochar: Experimental and theoretical insights

Mercury is ranked 3^rd as a global pollutant because of its long persistence in the environment. Approximately 65% of its anthropogenic emission (Hg⁰) to the atmosphere is from coal-thermal power plants. Thus, the Hg⁰ emission control from coal-thermal power plants is inevitable. Therefore, multiple sorbent materials were synthesized using a one-step pyrolysis method to capture the Hg⁰ from simulated coal syngas. Results showed, the Hg⁰ removal performance of the sorbents increased by the citric acid/ultrasonic application. T5CUF_0.3 demonstrated the highest Hg⁰ capturing performance with an adsorption capacity of 106.81 µg/g within 60 min at 200 °C under complex simulated syngas mixture (20% CO, 20% H₂, 10 ppmV HCl, 6% H₂O, and 400 ppmV H₂S). The Hg⁰ removal mechanism was proposed, revealing that the chemisorption governs the Hg⁰ removal process. Besides, the active Hg⁰ removal performance is attributed to the high dispersion of valence Fe₃O₄ and lattice oxygen (α) contents over the T5CUF_0.3 surface. In addition, the temperature programmed desorption (TPD) and XPS analysis confirmed that H₂S/HCl gases generate active sites over the sorbent surface, facilitating high Hg⁰ adsorption from syngas. This work represented a facile and practical pathway for utilizing cheap and eco-friendly tea waste to control the Hg⁰ emission.

Competitive removal mechanism to simultaneously incarcerate bisphenol A, triclosan and 4-tert-octylphenol within beta-cyclodextrin crosslinked citric acid used for encapsulation in polypropylene membrane protected-micro-solid-phase extraction

Endocrine disrupting compounds (EDCs) are extensively found in the environment and severely impacting human health. In addressing this issue, the beta-cyclodextrin crosslinked citric acid (BCD-CA) had been previously employed in membrane-protected micro-solid phase extraction for sequestering EDCs from water medium; and the findings revealed that BCD-CA possessed a selectivity property. On that account, the potential of BCD-CA towards competitive adsorption of selected EDCs was investigated in terms of adsorption mechanism and selectivity property. Factors that affected the removal efficiencies such as sample pH, sorbent dosage, contact time and initial concentration were evaluated. The characterization results revealed that the carbon percentage of BCD-CA had increased by 2.04%, while the hydrogen percentage had reduced by 1.83%, signifying the successful crosslinking of BCD-CA. Besides, the amount of active BCD was calculated to be 3.2 × 10^-7 mol, while the amount of carboxyl group was 2.48 × 10^-5 mol per 4 mg of BCD-CA. Moreover, BCD-CA was stable in an aqueous medium with the zeta potential obtained at -36.5 mV and had a high-water retention capacity (∼150%). The competitive adsorption mechanism by BCD-CA with EDCs followed the pseudo-second-order kinetics and Freundlich isotherm, suggesting that the adsorption process was dominated by chemisorption on the heterogeneous surface of the adsorbent. Thermodynamic results revealed that adsorption of 4-tert-octylphenol had the most negative ΔG value, indicating most favorable to be adsorbed by BCD-CA as opposed to triclosan and bisphenol A, which was coherent with the apparent formation constant results. These unique properties manifested the practicality of BCD-CA as a selective adsorbent to detect and remove EDCs from the water medium.

Examining the Effect of Organic Acids on Inactivation of Hepatitis E Virus

ABSTRACT

Infection with hepatitis E virus genotype 3 (HEV-3) is an emerging cause of illness in developed countries. In North America and Europe, HEV-3 has been increasingly detected in swine, and exposure to pigs and pork products is considered the primary source of infection. We have previously demonstrated the prevalence of the HEV-3 genome in commercial pork products in Canada. In this study, we investigated the application of citric acid and acetic acid to inactivate HEV-3 on food and on food contact surfaces. For this purpose, plastic, stainless steel, and pork pâté surfaces were inoculated with HEV-3 and were treated with acetic acid or citric acid at 1, 3, or 5%. The infectivity of posttreatment viral particles was determined by cell culture. A greater than 2-log reduction in viral infectivity was observed on plastic and stainless steel treated with the organic acids, but the treatment was less effective on HEV infectivity on pork pâté (average reductions of 0.47 log citric acid and 0.63 log acetic acid). Therefore, we conclude that citric acid and acetic acid have potential application to control HEV-3 on food contact surfaces but are not suitable for food.

HIGHLIGHTS

Potential mechanisms contributing to the high cadmium removal efficiency from contaminated soil by using effective microorganisms as novel electrolyte in electrokinetic remediation applications

In this study, we tested the ability of a solution of effective microorganisms (EM) to remove cadmium from soil. Experimental results revealed that EM had an overall cadmium removal efficiency of 90.5% after 7 days of electrokinetic (EK) treatment. During EK treatment, EM exhibited a low initial pH of 3.6 and a high conductivity of 7.0 mS/m; therefore, they reduced the pH of the anode after an electric field was applied. EM had a surface tension of 50.3 dyne/cm and exhibited biosurfactant property in the EK experiments. The cadmium removal efficiency of EM in soil was compared with that of tap water, citric acid, and ethylenediaminetetraacetic acid (EDTA). The results revealed that after 7 days of EK treatment, EM had a higher cadmium removal efficiency than did citric acid (72.3%), EDTA (75.4%), and tap water (21.7%). This result can be partly attributed to the biosurfactant property of EM, which enables them to penetrate deeply into the soil matrix and thus dissolve a high quantity of pollutants. Overall, the results of this study indicate that EM can serve as an economic and efficient biosurfactant for removing cadmium from soil in EK applications.

Arsenic inhibits citric acid accumulation via downregulating vacuolar proton pump gene expression in citrus fruits

Citric acid content is a critical quality determinant in citrus (Citrus spp.) fruits. Although arsenic (As) can effectively reduce citric acid content to improve citrus fruit quality, it can have adverse environmental effects. The discovery of nontoxic substitutes is hampered by the incomplete elucidation of the underlying mechanisms of As action in citrus fruits. Metabolic, transcriptomic, and physiological analyses were employed to investigate As action on citric acid accumulation to discover the mechanisms of As action in citrus. The enzyme activity related to citrate biosynthesis was not inhibited and the content of the involved metabolites was not reduced in As-treated fruits. However, the proton pump genes CitPH5 and CitPH1 control the vacuolar citric acid accumulation and transcription factor genes CitTT8 and CitMYB5, which regulate CitPH5 and CitPH1, were downregulated. The oxidative stress-response genes were upregulated in As-treated fruits. The reactive oxygen species (ROS) treatment also downregulated CitTT8 and CitMYB5 in juice cells. The mitochondrial ROS production rate increased in As-treated fruits. As^III was more potent in stimulating isolated mitochondria to overproduce ROS compared to As^V. Our results indicate that the As inhibition of citric acid accumulation may be primarily due to the transcriptional downregulation of CitPH5, CitPH1, CitTT8, and CitMYB5. As-induced oxidative stress signaling may operate upstream to downregulate these acid regulator genes. Mitochondrial thiol proteins may be the principal targets of As action in citrus fruits.

Enhanced remediation of surface-bound hexavalent chromium in soils using the acidic and alkaline fronts of electrokinetic technology

In the subsurface environment, highly toxic hexavalent chromium (Cr(VI)) control and remediation are essential to avoid further ecological impacts and reduce environmental risks. This paper investigated the enhanced Cr(VI) electrokinetic removal in the soil through the approaching cathode method. Besides, a novel four-step sequential fractionation method was used to reflect the strength of Cr(VI) binding to the soil. The approaching cathode enhanced the electrokinetic delivery of surface-bound Cr(VI) by advancing the alkaline front for Cr(VI) desorption and improving the electric potential flattening of the soil layers. Desorption of Cr(VI) by the alkaline front involved converting the inner-sphere complexes form of Cr(VI) to a weakly adsorbed form susceptible to ionic strength. In addition, the acidic front provided a favorable environment for the photochemical reduction of Cr(VI) by soil species or the added citrate as the electron donors. Improving the potential distribution could regulate the energy consumption of individual soil layers and efficiently operate the electrokinetic transfer of pollutants. The work results have significant scientific and practical significance for applying the in-situ electrokinetic technique in subsurface pollution control.

R2R3-MYB transcription factor FaMYB5 is involved in citric acid metabolism in strawberry fruits

The citrate content of strawberry fruits affects their organoleptic quality. However, little is known about the transcriptional regulatory mechanisms of citric acid metabolism in strawberry fruits. In this study, the R2R3-MYB transcription factor FaMYB5 was identified and placed in the R2R3-MYB subfamily. FaMYB5 is found in the nucleus and shows tissue- and stage-specific expression levels. Citric acid content was positively correlated with FaMYB5 transcript levels. Upregulated FaMYB5 increased citric acid accumulation in transient FaMYB5-overexpressing strawberry fruits, whereas transient RNA silencing of FaMYB5 in strawberry fruits resulted in a reduction of citric acid content. The role of FaMYB5 was verified using stable transgenic NC89 tobacco. Furthermore, a yeast one-hybrid assay revealed that FaMYB5 influences citric acid accumulation by binding to the FaACO (aconitase), FaGAD (glutamate decarboxylase), and FaCS2 (citrate synthase) promoters. Dual-luciferase assays were used to demonstrate that FaMYB5 could activate FaCS2 expression and repress the transcription levels of FaACO and FaGAD. This study identified important roles of FaMYB5 in the regulation of citric acid metabolism and provided a potential target for improving strawberry fruit taste in horticultural crops.

Simultaneous saccharification and citric acid production from paper wastewater pretreated banana pseudostem: Optimization of fermentation medium formulation and kinetic assessment

This study optimized the simultaneous saccharification and citric acid (CA) production from banana pseudostem (BP). Thereafter, kinetic assessment of Aspergillus brasiliensis growth and CA production were determined for the optimum conditions using fresh water (SSF_optimizedFW) or dairy wastewater (SSF_DWW) and compared to Sabouraud Dextrose Emmon's medium modified with BP (SSF_SDEmodified). The optimized conditions gave a CA concentration of 14.408 g/L. Kinetic assessment revealed the same maximum specific growth rates (μ_max) (0.05 h^-1) for all three bioprocesses, while the SSF_SDEmodified process resulted in the highest maximum potential CA concentration (P_m) (13.991 g/L) in comparison to the SSF_DWW (P_m = 13.095 g/L) and SSF_optimizedFW (P_m = 12.967 g/L) systems. Findings from this study facilitates the implementation of waste-based lignocellulosic bioprocesses that may eradicate the use of expensive pretreatment chemicals, fermentation medium constituents, and resources, in keeping with the water, energy and food nexus towards developing a circular bioeconomy.

Biosolids-based activated carbon for enhanced copper removal from citric-acid-rich aqueous media

In this study, we employed batch experiments to assess the effects of citric acid on the Cu(II) removal efficiencies of seven biosolids-based adsorbents. The adsorbents used were dried biosolids (BS), biosolids biochar (BSBC), biosolids-based activated carbon (SBAC), nitric-acid-modified BSBC (BSBC-HNO₃) and SBAC (SBAC-HNO₃), and amine-modified BSBC (BSBC-NH₂) and SBAC (SBAC-NH₂). However, with 100 mM citric acid in 1 mM Cu(II) solution, only SBAC showed an increase in Cu(II) removal efficiency (64.0-93.5%). Therefore, we used SBAC for further optimisation of the adsorption process. The kinetics data, optimally described by the pseudo-second-order model, indicated that bulk Cu(II) adsorption occurred within 10 min. The highest Cu(II) removal was at pH 3, with the estimated maximum Cu(II) adsorption capacity of SBAC increasing from 0.14 to 0.30 mmol/g, with 100 mM citric acid present. This result clearly indicated the positive effect of citric acid on Cu(II) adsorption. With citric acid present, the Freundlich model optimally fitted the adsorption isotherm data, suggesting adsorption of Cu(II) in multilayers. Further investigation of Cu(II) adsorption in a sequential setup proved that SBAC could lower the residual Cu(II) in the solution to below the discharge limit (0.05 mM) in 1 h. Overall, the production of activated carbon from BS has been proven an efficient Cu(II) adsorbent for Cu-citric-acid-rich aqueous media as a simulation of real wastewaters/leachates, as well as achieving waste-to-resources goals. This is the first study to identify an adsorbent (SBAC) with increased Cu(II) adsorption capacity in the presence of excess citric acid.

Identification of chitin synthase activator in Aspergillus niger and its application in citric acid fermentation

The biosynthesis of citric acid (CA) using Aspergillus niger as a carrier is influenced by mycelium morphology, which is determined by the expression level of morphology-related genes. As a key component of the fungal cell wall, chitin content has an important effect on morphogenesis, and to investigate the effects of this on fermentation performance, we used RNA interference to knockdown chitin synthase C (CHSC) and chitin synthase activator (CHS3) to obtain the single-gene mutant strains A. niger chs3 and chsC and the double mutant A. niger chs3C. We found that the CA fermentation performance of the two single mutants was significantly better than that of the double mutant. The mutant A. niger chs3-4 exhibited CA production potential compared to that of the parent strain in scale-up fermentation; we determined certain characteristics of CA high-yielding strain fermentation pellets. In addition, when chsC alone was silenced, there was very little change in chs3 mRNA levels, whereas those of chsC were significantly reduced when only chs3 was silenced. As this may be because of a synergistic effect between chsC and chs3, and we speculated that the latent activation target of CHS3 is CHSC, our results confirmed this hypothesis. This study is the first application of a separation and combination silence strategy of chitin synthase and chitin synthase activator in the morphology of A. niger CA fermentation. Furthermore, it provides new insights into the method for the morphological study of A. niger fermentation and the interaction of homologous genes. KEY POINTS: • The function of chitin synthase C (chsC) and chitin synthase activator (chs3) is tightly interrelated. • Mycelial morphology was optimized by knockdown of CHS3, resulting in the overproduction of citric acid. • The separation and combination silence strategies are promising tools for the interaction of homologous housekeeping genes.

Effect of citric acid erosion on enamel and dentin and possible protection by a novel bioactive borate adhesive system

OBJECTIVES

This study examined the ability of a borate adhesive to protect enamel/dentin surfaces from acidic erosion and its effect on the shear bond strength (SBS) of enamel/dentin to resin composite.

MATERIALS AND METHODS

180 human enamel/dentin specimens were utilized. Enamel buccal surfaces were etched with phosphoric-acid then divided into: (EBG) borate glass adhesive group; (ERS) resin-adhesive system group; (EF) fluoride gel 1.23% group, and enamel control (EC) group; followed by bonding to orthodontic-buttons. The dentin specimens were conditioned by EDTA (Ethylene-diamine-tetra-acetic acid) and divided into: (DBG) borate glass resin, (DRS) resin adhesive; (DDA) group had a dentin-desensitizing agent VivaSens (VivaDent, Liechtenstein) and (DC) control group. The treated enamel/dentin specimens had their SBS to composite. The enamel/dentin specimens were exposed to 1% citric acid (18 min). Enamel/dentin specimens were examined by (SEM/EDS) scanning-electron-microscope equipped with electron-dispersive-spectroscopy and (FTIR/ATR). Analysis-of-Variance (ANOVA) was used to compare the SBS and Wilcoxon-signed-rank test was used to compare the enamel/dentin areas protected by the applied agents before/after erosion (p = 0.05).

RESULTS

There was no significance difference in SBS among all groups except for (DDA) group that showed significant decrease p < 0.05. (EBG) and (DBG) groups were the only groups significantly protected enamel and dentin from erosion p < 0.05. FTIR/ATR showed that erosion altered the chemical structure of (DRS), (DDA), and (DC) groups but did not affect the other enamel/dentin groups. Degree of conversion of the borate-adhesive system was acceptable.

CONCLUSION

The Borate adhesive system released calcium and phosphate compounds that decreased the erosive activity of the citric acid resulting in protecting simulated dentin-hypersensitive areas and enamel from erosion without affecting the SBS to resin-composite.

CLINICAL SIGNIFICANCE

A Borate adhesive system can be adopted as a therapeutic agent in a fully integrated program for protecting dentin-hypersensitive areas and in enamel next to orthodontic fixed appliances.

Cytocompatibility and antimicrobial activity of a novel endodontic irrigant combining citric acid and chlorhexidine

OBJECTIVES

This study aimed to evaluate the antibacterial ability and cytocompatibility of a new irrigant solution for endodontic treatment composed of 10% citric acid (CA) and 1% chlorhexidine (CHX).

METHODS

Thirty-five extracted single-canal human teeth were selected and de-crowned. Canal systems (n = 7/group) were infected with Enterococcus faecalis for 4 weeks and subject to irrigation with 1% CHX; 10% CA; irrigating solution 10% CA associated with 1% CHX (CACHX); 2.5% NaOCl or sterile water (control). Microbiological samples were collected immediately and 18 h after irrigation (enriched samples). The canals were filled with culture medium post irrigation to verify the bacterial presence/absence qualitatively and quantitatively through colony counting (log₁₀ CFU/mL). A multiparametric assay was performed after exposure of human periodontal ligament fibroblasts (HPdLF) to the test solutions. The Kruskal-Wallis test with Dunn´s post-test and Fisher's exact test were employed at the 95% confidence level to compare differences among groups.

RESULTS

All tested solutions were cytocompatible with human periodontal ligament fibroblasts. No difference was observed on antibacterial activity between 1% CHX, 10% CA, CACHX and 2.5% NaOCl (p > 0.05). Eighteen hours after irrigation, CACHX samples were the only that did not present E. faecalis in the root canal system.

CONCLUSIONS

The demonstrated good in vitro biocompatibility and elimination of E. faecalis suggest a potential use of 10% CA associated with 1% CHX as a solution for microbiological control during endodontic treatment.

CLINICAL RELEVANCE

Irrigants play an essential role during endodontic therapy. This irrigating solution, based on the association of 10% citric acid with 1% chlorhexidine, seems viable for clinical procedures.

Photoluminescence mechanisms of red-emissive carbon dots derived from non-conjugated molecules

Red-emissive carbon dots (R-CDs) have been widely studied because of their potential application in tissue imaging and optoelectronic devices. At present, most R-CDs are synthesized by using aromatic precursors, but the synthesis of R-CDs from non-aromatic precursors is challenging, and the emission mechanism remains unclear. Herein, different R-CDs were rationally synthesized using citric acid (CA), a prototype non-aromatic precursor, with the assistance of ammonia. Their structural evolution and optical mechanism were investigated. The addition of NH₃·H₂O played a key role in the synthesis of CA-based R-CDs, which shifted the emission wavelength of CA-based CDs from 423 to 667 nm. Mass spectrometry (MS) analysis indicated that the amino groups served as N dopants and promoted the formation of localized conjugated domains through an intermolecular amide ring, thereby inducing a significant emission redshift. The red-emissive mechanism of CDs was further confirmed by control experiments using other CA-like molecules (e.g., aconitic acid, tartaric acid, aspartic acid, malic acid, and maleic acid) as precursors. MS, nuclear magnetic resonance characterization, and computational modeling revealed that the main carbon chain length of CA-like precursors tailored the cyclization mode, leading to hexatomic, pentatomic, unstable three/four-membered ring systems or cyclization failure. Among these systems, the hexatomic ring led to the largest emission redshift (244 nm, known for CA-based CDs). This work determined the origin of red emission in CA-based CDs, which would guide research on the controlled synthesis of R-CDs from other non-aromatic precursors.

Effect of organic acids on the morphology and particle size of titanium dioxide (E171) in processed food

TiO₂ (E171) is widely used in processed food as a coloring agent. However, growing concerns about the potential health effects of TiO₂ nanoparticles (< 100 nm) have necessitated the need for monitoring the size distribution and cytotoxic properties of food additive TiO₂ present in commercial food. In this study, we employed magnetic separation method to extract food additive TiO₂ from 100 commercial foods. The extracted TiO₂ had a mean particle diameter of 121-143 nm along with the fraction in nanoscale (< 100 nm) ranging from 7.5% to 35.7%, where certain types of food, such as candy and jelly, were shown to contain smaller TiO₂ with higher fraction of nanoscale particles. Assuming that the low pH of the products with high content of organic acid is responsible for the smaller TiO₂, the effect of three organic acids, such as acetic acid, ascorbic acid, and citric acid, on the physicochemical property of TiO₂ was investigated. The citric acid was shown to reduce the size of TiO₂ along with the generation of fragmented nanoparticles with a size of around 20 nm, whereas the effect of acetic acid and ascorbic acid was negligible. Although TiO₂ treated with citric acid did not exhibit short-term cytotoxicity, this study suggests the importance of fully assessing the potential long-term health effect of food additive TiO₂ whose physicochemical properties were altered in processed food.

Microbe-citric acid assisted phytoremediation of chromium by castor bean (Ricinus communis L.)

Chromium is one of the highly toxic heavy metals to plant growth and development especially hexavalent chromium (Cr+6) due to its readily available nature and mobility into the environment. The chelating agents and hyperaccumulator plant can contribute to remediating the heavy metals from the contaminated medium. This study was conducted to analyze the role of citric acid and chromium resistant bacteria in castor bean to remediate Cr+6 from the polluted soil. The soil was spiked with different levels of citric acid (0, 2.5, 5 mM) and chromium (0, 10, 20 mg kg-1). The ripened plants were harvested and analyzed for growth parameters, chlorophyll contents, gas exchange parameters, oxidative stress markers, antioxidant enzymes activities and chromium accumulation in different parts of plants. The high concentration of chromium 20 mg kg-1 drastically reduced the plant growth, decreased photosynthetic rate and increased oxidative stress. The application of CA improved the plant growth even at the highest concentration of chromium which was further boosted by the combined application of CA and chromium resistant bacteria. However, the performance of staphylococcus aureus was found significantly better than Bacillus subtilis due to its better ability to tolerate chromium toxicity even at high concentrations. The findings proved that castor bean has excellent potential to tolerate high chromium concentrations and can be effectively used to remediate metals contaminated soil. Further, CA and metal resistant bacteria can significantly enhance the phytoremediation potential of castor bean and other hyperaccumulator plants. The bacteria assisted phytoremediation coupled with the chelating agent can be a practical approach to remediate the metals contaminating soils.

Effects of Corn Straw and Citric Acid on Removal of PAHs in Contaminated Soil Related to Changing of Bacterial Community and Functional Gene Expression

Root exudates can stimulate microbial degradation in rhizosphere, but it is unclear whether the rhizodegradation of polycyclic aromatic hydrocarbons (PAHs) occurs in corn straw-amended soil. Either citric acid or corn straw was added into PAHs-contaminated soil to investigate their effect on the removal of PAHs. Either corn straw (Y) or combined application of corn straw and citric acid (YN100) significantly (p < 0.05) enhanced the removal of soil PAHs by 8.43% and 18.62%, respectively. Both Y and YN100 treatments obviously increased the abundance of PAHs degraders and the potential hosts of PAH-ring hydroxylating dioxygenase (PAH-RHDα) genes. Interestingly, the copies of PAH-RHDα Gram-negative bacteria genes under YN100 treatment was significantly (p < 0.05) higher than those under Y treatment. The present results indicated that combined application of corn straw and citric acid could efficiently enhance the removal of PAHs in soil, mainly via increasing the relative abundances of PAH-degrading bacteria and the expression of PAH-RHDα genes in contaminated soil.

Antibiofilm activity of the biosurfactant and organic acids against foodborne pathogens at different temperatures, times of contact, and concentrations

Biofilm formation has been suggested to play a significant role in the survival of pathogens in food production. Interest in evaluating alternative products of natural origin for disinfectant use has increased. However, there is a lack of information regarding the effects of biosurfactants and organic acids on Salmonella enterica serotype Enteritidis, Escherichia coli, and Campylobacter jejuni biofilms, mainly considering temperatures found in environments of poultry processing, as well as simulating the contact times used for disinfection. The aim of this study was to evaluate the antibiofilm activity of rhamnolipid, malic acid, and citric acid on the adhesion of S. Enteritidis, E. coli, and C. jejuni on polystyrene surfaces at different temperatures (4, 12, and 25 °C), compound concentrations, and times of contact (5 and 10 min), and to analyze the potential use of these compounds to disrupt formed biofilms. All three compounds exhibited antibiofilm activity under all analyzed conditions, both in the prevention and removal of formed biofilms. Contact time was less important than temperature and concentration. The antibiofilm activity of the compounds also varied according to the pathogens involved. In the food industry, compound selection must consider the temperature found in each stage of product processing and the target pathogens to be controlled.

Citric acid-mediated green synthesis of selenium nanoparticles: antioxidant, antimicrobial, and anticoagulant potential applications

Using microwave technique in the presence of citric acid, selenium nanoparticles (SeNPs) were fabricated. The morphological characteristics revealed that the spherical SeNPs with diameters ranging from 10.5 to 20 nm aggregated spherical shapes with sizes ranging from 0.67 to 0.83 mm. Moreover, the antioxidant efficacy was assessed by the DPPH radical scavenging test, which depicted that green-prepared nanoparticle at a 106.3 mg/mL dosage had the maximum scavenging capacity (301.1 ± 11.42 mg/g). Otherwise, with nanoparticle concentrations of 500 mg/ml, in vitro cell viability of SeNPs through human breast cancer MCF-7 cell lines was reduced to 61.2 ± 2.2% after 1 day of exposure. The antibacterial activity was tested against G-negative Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli), G-positive bacteria Bacillus subtilis (B. subtilis), and Staphylococcus aureus (S. aureus), which demonstrated that SeNPs had little activity against S. aureus. Still, it had the highest activity against E. coli, with a zone of inhibition (ZOI) of 25.2 ± 1.5 mm compared to 16.0 ± 0.6 mm for the standard antibiotic. Most notably, biogenic SeNPs have anticoagulant activities using activated partial thromboplastin time (aPTT) assessment. Based on previous findings, SeNPs can be used in medical aid and their cell viability, antioxidant, anticoagulant, and effects on bacteria.

Effect of pH and titratable acidity on enamel and dentine erosion

OBJECTIVES

The relative effect of pH and titratable acidity on tooth erosion remains unclear. We determined the effect of both properties on in vivo salivary pH recovery and on enamel and dentine early erosion in situ.

METHODS

Solutions simulating acidic beverages with different pHs (2.5 or 3.5) and titratable acidities (0, 25, or 100 mM citric acid) were tested. In an in vivo study (n = 20 participants), the salivary pH was determined before, during, and up to 2 min after exposure to the tested solutions. In situ, 12 participants exposed enamel and root dentine slabs to the tested solutions simulating a beverage consumption; early erosion was assessed by percentage of surface hardness loss (%SHL). Groups were compared by ANOVA (p < 0.05).

RESULTS

Saliva pH was lower after exposure to solutions at pH 2.5, irrespective of titratable acidity; pH recovery took longer for solutions with higher titratable acidities, irrespective of their pHs. In situ, the highest %SHL was observed for the solution with lower pH and higher titratable acidities. The addition of citric acid increased the %SHL by 2.5-3 times in enamel, and at least 5 times in dentine.

CONCLUSIONS

Both pH and titratable acidity may play a role on the erosive potential of acidic beverages.

CLINICAL RELEVANCE

Acidic beverages with lower pHs promote erosion by an initial acid etching of the surface; those with a higher titratable acidity slow down the salivary pH recovery. Both properties contribute to the overall erosive potential.

A feasible biochar derived from biogas residue and its application in the efficient adsorption of tetracycline from an aqueous solution

The recovery of carbon materials from biogas residue (BR) could efficiently promote the efficient utilization of waste and the preparation of novel materials. In this study, a green and feasible reagent of citric acid was introduced and applied in the modification of biogas residue biochar (BRC). The modified biogas residue biochar (CABRC) showed a superior adsorption ability due to its higher specific surface area (approximately 6 times that of the BRC). Additionally, the adsorption capacities of CABRC and BRC for TC were 58.25 mg/g and 20.77 mg/g, respectively, while the TC adsorption performance of CABRC was 2.8 times that of BRC. The adsorption of TC by both BRC and CABRC was primarily controlled by physical adsorption and chemical adsorption (including pore filling, hydrogen bonding, π-π DEA interaction, and electrostatic interaction). Therefore, CABRC should be considered an environmentally friendly material due to its higher adsorption performance, which could expand its application in wastewater treatment.

Remediation for trace metals in polluted soils by turfgrass assisted with chemical reagents

Trace metal pollution in soils is one of the universal environmental problems in the world. Phytoremediation is a green, safe, ecological, and economic method to achieve continuous reduction of soil pollutants. Turfgrass is a plant with great landscape value and has considerable biomass when used for remediation of trace metal contaminated soil. However, its remediation ability needs to be improved in future application. The combined application of turfgrass, citric acid (CA) and auxin (gibberellin, GA₃) were applied in the phytoremediation of an artificial nutritive soil derived from sludge, and a field scale orthogonal experiment (L₉) was conducted to understand the interaction effect and obtain the optimum phytoremediation. Experimental results showed that the types and cultural patterns of turfgrass mainly determined plant height, root length and trace metal concentration in turfgrass, however CA treatment was prone to increase the aboveground biomass and the concentrations of most trace metals in turfgrasses, especially the concentration of Ni in turfgrass. GA₃ spraying significantly increased the concentration of Cd in turfgrass. The culture patterns of turfgrass played 42.4% influence on acid-extractable Cd, while CA applying had 53.8% influence on the acid-extractable Ni. The annual phytoextraction amount of trace metals based on five mowing a year were proposed to assess the remediation ability of treatments, which of the combination treatment (T3, intercropping Zoysia matrella and Lolium perenne, and applying 400 mg kg^-1 CA and 30 mg kg^-1 GA₃) were 1.6-2.1 times higher CK group. This research provides technical reference for intercropping turfgrass for remediation of trace metals in sludge-derived nutritive soil.

Phytoremediation of uranium-contaminated soil by perennial ryegrass (Lolium perenne L.) enhanced with citric acid application

Perennial ryegrass (Lolium perenne L.) was planted in uranium-contaminated soil mixtures supplemented with different amounts of citric acid to investigate the defense strategies of perennial ryegrass against U and the enhanced mechanism of citric acid on the remediation efficiency in the laboratory. The uranium content in the plant tissues showed that the roots were the predominant tissue for uranium accumulation. In both root and shoot cells, the majority of U was located in the cell wall fraction. Furthermore, antioxidant enzymes were also stimulated when exposed to U stress. These results suggested that perennial ryegrass had evolved defense strategies, such as U sequestration in root tissue, compartmentalization in the cell wall, and antioxidant enzyme systems, to minimize uranium stress. For an enhanced mechanism, the optimal concentration of citric acid was 5 mmol/kg, and the removal efficiency of U in the shoots and roots increased by 47.37% and 30.10%, respectively. The treatment with 5 mmol/kg citric acid had the highest contents of photosynthetic pigment and soluble protein, the highest activity of antioxidant enzymes, and the lowest content of MDA (malondialdehyde) and relative electrical conductivity. Moreover, the TEM (transmission electron microscope) results revealed that after 5 mmol/kg citric acid was added, the cell structure of plant branches partially returned to normal, the number of mitochondria increased, chloroplast surfaces seemed normal, and the cell wall became visible. The damage to the cell ultrastructure of perennial ryegrass was significantly alleviated by treatment with 5 mmol/kg citric acid. All the results above indicated that perennial ryegrass could accumulate uranium with elevated uranium tolerance and enrichment ability with 5 mmol/kg citric acid.

Effects of citric acid on antioxidant system and carbon-nitrogen metabolism of Elymus dahuricus under Cd stress

Exogenous citric acid (CA), which acts as an important intermediate product of the tricarboxylic acid (TCA) cycle, can enhance the TCA cycle activity and activate the branched operation of the TCA cycle, thus providing energy required for resistance to adverse conditions. However, the effects of CA application on TCA cycle-related metabolism under cadmium (Cd) were less reported. To investigate the effects of CA on the Cd tolerance of Dahurian wildrye grass (Elymus dahuricus), the growth, Cd accumulation, antioxidant systems and metabolic pathways of leaves and roots were investigated by a potted soil experiment with Cd (50 mg/kg) and CA (4 mmol/L) treatments. The results showed that Cd stress seriously affected growth and induced the production of reactive oxygen in clover leaves and roots, leading to membrane peroxidation and activation of the antioxidant defense system. Exogenous CA could not only effectively relieve the inhibition of Cd stress on growth and reduce the amount of reactive oxygen by increasing the antioxidant capacities but could also promote an increase in root Cd content. Metabolomic results showed that the application of CA increased the contents of sugars, sugar alcohols, and resistant substances, and promoted the metabolism of amino acids including γ-aminobutyric acid (GABA). These alterations contributed the significant enhancement of the Cd resistance, which may be related to the changes in the TCA cycle activity and the metabolism of the shikimic acid pathway in leaves and roots as well as GABA shunt in roots.

Maximising the bioaccessibility of iron and zinc of a complementary food mix through multiple strategies

The investigation was undertaken to maximise the bioaccessibility of iron and zinc of a complementary food mix by multiple approaches of dephytinisation and addition of organic acids. A wheat, pulse and oilseed protein flour mix was dephytinized by phytase activation and different thermal treatments. As the mineral content of the mix was low, the spray dried mix was fortified with different iron and zinc salts to identify the salt with the highest bioaccessibility in this matrix. Based on the percent bioaccessibility, the mix with sodium iron EDTA and zinc oxide was chosen for fortification. Bioaccessibility was enhanced by the addition of fruit powders and pure organic acids. Fruit powders showed a significant increase, but citric acid at a higher dose was beneficial in enhancing bioaccessible iron. The strategy of dephytinisation followed by fortification and the addition of fruit powders or organic acids is promising in alleviating iron and zinc deficiencies.

Circular bioeconomy: Life cycle assessment of scaled-up cascading production from orange peel waste under current and future electricity mixes

Orange peel waste (OPW) is present in large quantities both locally and globally, which makes them feasible input into the circular bioeconomy. However, due to their antimicrobial and anti-nutritional activity, they are problematic biomass, and proper waste management is yet to be determined. This life cycle assessment (LCA) quantifies the environmental performance of biorefinery producing limonene, citric acid, and animal feed from OPW generated from juice factories. Only previously assessed sustainable technologies were considered (cold press, microwave extraction, solid-state fermentation). The life cycle inventories were refined by a scale-up procedure to reflect industrial production at i) 0.5 t, ii) 100 t, and iii) 1000 t of OPW weekly. The data were translated per functional unit of 1 tonne OPW. Three electricity mixes and both attributional (average) and consequential (marginal) inventories were compared. Results showed that the environmental performance, in particular for climate change, was essentially dependent upon the electricity input, with 4388 CO₂ eq for current electricity mix, 2404 CO₂ eq using renewable, and 594 CO₂ eq using electricity from wind. Business-as-usual scenarios for OPW (incineration and animal feed) showed better performance in most scenarios, representing -150 CO₂ eq (animal feed) and -135 CO₂ eq (incineration) in the climate change. Lower impacts are reached due to avoided impacts of fossil fuel use and conventional feed cultivation. Renewable energy had better environmental performance than the current electricity mix, except for eutrophication, due to digestate spreading associated with biogas use, calling for mitigation action. Our results suggest that stopping the biorefinery processes immediately after the recovery of limonene via solvent-free microwave extraction process, with subsequent use of the dried OPW as animal feed, is the most environmentally performant option. This represents a feasible strategy for the circular bioeconomy and is in line with the updated food waste hierarchy.

Nitrogen modulates strontium uptake and toxicity in Hypericum perforatum plants

Strontium is an unavoidable element occurring in plants due to its abundance in the soil and similarity with calcium. To mimic natural conditions, impacts of additional inorganic (nitrate) or organic (urea and allantoin) nitrogen sources (1 mM of each N form in addition to 3.53 mM N in the basic cultivation solution) or N deficit on strontium-induced changes (100 µM Sr) in the widely used medicinal plant Hypericum perforatum L. were studied. Though various effects of Sr on primary (stimulation of amino acids but depression of most Krebs acids, ascorbic acid and thiols) and secondary metabolites (stimulation of phenols but no change of pseudo/hypericin) or mineral elements were observed (reduction of Ca amount in both shoots and roots), organic N forms often mitigated negative action of Sr or even combined stimulatory impact was observed. Organic N forms also elevated shoot accumulation of Sr while N deficit reduced it. Additional N forms, rather than Sr itself, modulated reactive oxygen species and nitric oxide formation in the root tissue. Germination experiment showed no toxicity of Sr to H. perforatum up to 1 mM Sr and even stimulated accumulation of amino acids and phenols, indicating similar ontogenetic-related responses.

in amelioration of cadmium and chromium toxicity in wheat

Heavy metals contamination in agricultural soil is a major issue having drastic effects on plants and human health. To solve this issue, we have formulated and tested a new approach of fusion of inorganic (citric acid chelate) and organic (Bacillus sp.) amelioration methods for heavy metals. The Bacillus sp. was heavy metal tolerant and showed plant growth-promoting characteristics including phosphate solubilization, siderophore production, hydrogen cyanide production, indole acetic acid production, and 1-Aminocyclopropane-1-carboxylate deaminase production. The analysis of data showed that plants receiving the combined application of citric acid (CA) chelate and Bacillus sp. mitigated heavy metal toxicity. They augmented the biomass production and amount of photosynthetic pigments in plant cells. They suppressed the negative effects of Cadmium (Cd) and Chromium (Cr) on plants' metabolic systems. A considerable increase was also observed in the activity of enzymatic and non-enzymatic antioxidants which reduced the damaging effects of reactive oxygen species and maintained internal structures of cells. The decrease in the content of Cr and Cd in wheat grains by the treatment of CA chelate and Bacillus sp. was 51%, and 27% respectively. The bioaccumulation of metals was also reduced to 49% (Cr) and 57% (Cd). This approach can be tested and applied in field conditions for soils with heavy metals contamination.

Microstructure and properties of thermomechanically processed chitosan citrate-based materials

The traditional solvent casting method for preparing chitosan-based materials has limited productivity relative to the productivity of thermomechanical processing. Consequently, the thermomechanical processing technique was evaluated as a way to increase chitosan production. The role of citric acid (CA) as a destructuring and crosslinking agent during such processing was examined. SEM images revealed robust fibers that were associated with a superior mechanical strength (145%), which were produced after thermomechanical processing of chitosan in the presence of CA. Based on articles reviewed, this is the first time that this structure has been closely observed in the microstructure of chitosan-based materials. FTIR and XRD characterization showed the occurrence of chemical crosslinking and the successful destructuring of chitosan powder by CA during processing. Compared to acetic acid, the use of CA led to the development of materials with a homogeneous morphology and good physicochemical and mechanical properties that are suitable for biomedical applications.

Feasibility of a combined solubilization and eluent drainage system to remove Cd and Cu from agricultural soil

Washing using low-molecular-weight organic acid is an effective and eco-friendly technique to permanently remove heavy metals from soil. There is still lack of evaluation of the application modes and the recovery methods, as well as the variations of heavy metal and nutrients fractions on a pilot-scale during washing. Here, we developed a simple combined solubilization and eluent drainage system in a pilot-scale washing box using industrial grade citric acid with feasible waste eluent treatment method to remove cadmium (Cd) and copper (Cu) from agricultural soil. The removal rates of Cd and Cu after sequential two-stage citric acid-water washing reach up 68.9% and Cu 41.4%, which was 7.5% and 10.0% higher than single citric acid. The removed the heavy metals were mainly in exchangeable and reducible fractions. The heavy metals at different soil depth were dissolved more effectively by citric acid-water washing with wheat straw as underdrain filling material than that of crushed stone. The potential risks of Cd in soils all decreased by approximately 75% from considerable to low risk. The two-stage citric acid-water washing significantly mitigated the effect of soil acidification. The average contents of soil organic matter, available ammonium N-NH₄ and available phosphorus increased by 40.9%, 57.3%, 32.0% after citric acid-water washing under wheat straw filling. The waste eluent can be efficiently recovered by clam powder, which removed 78.7% of Cd and 57.5% of Cu. The regenerated citric acid showed similar removal efficiencies for Cd and Cu compared to the fresh citric acid. These results indicate that the combination of washing, drainage and flocculation can effectively remove Cd and Cu from contaminated agricultural soil and realize the recycling of waste eluent.

The Effect of Anti-Chemokine Oral Drug XC8 on Cough Triggered by The Agonists of TRPA1 But Not TRPV1 Channels in Guinea Pigs

Introduction

Chronic cough heavily affects patients’ quality of life, and there are no effective licensed therapies available. Cough is a complication of severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) infection, asthma, and other diseases. Patients with various diseases have a different profile of tussive responses to diverse cough triggers, thereby suggesting sundry mechanisms of neuronal dysfunctions. Previously, we demonstrated that the small molecule drug XC8 shows a clinical anti-asthmatic effect. The objective of the present study was to investigate the effect of XC8 on cough.

Methods

We studied the antitussive effect of XC8 on cough induced by agonists activating human transient receptor potential (TRP) cation channels TRPA1 or TRPV1 in guinea pigs. We checked the agonistic/antagonistic activity of XC8 on the human cation channels TRPA1, TRPV1, TRPM8, P2X purinoceptor 2 (P2X2), and human acid sensing ion channel 3 (hASIC3) in Fluorescent Imaging Plate Reader (FLIPR) assay.

Results

XC8 demonstrated clear antitussive activity and dose-dependently inhibited cough in guinea pigs induced by citric acid alone (up to 67.1%) or in combination with IFN-γ (up to 76.4%). XC8 suppressed cough reflexes induced by the repeated inhalation of citric acid (up to 80%) or by cinnamaldehyde (up to 60%). No activity of XC8 against cough evoked by capsaicin was revealed. No direct agonistic/antagonistic activity of XC8 on human TRPA1, TRPV1, TRPM8, P2X2, or hASIC3 was detected.

Conclusions

XC8 acts against cough evoked by the activation of TRPA1 (citric acid/cinnamaldehyde) but not TRPV1 (capsaicin) channels. XC8 inhibits the cough reflex and suppresses the cough potentiation by IFN-γ. XC8 might be of significant therapeutic value for patients suffering from chronic cough associated with inflammation.

Colorimetric detection of citric acid as the biomarker for urolithiasis based on sodium dodecylsulfate-AgNPs with a portable CD-spectrometer

Citric acid (CA) has been considered as a biomarker of urolithiasis due to its vital suppression role in urinary stone formation. Most analytical methods for detecting CA are complicated and require expensive equipment. Herein, a colorimetric method based on sodium dodecylsulfate (SDS) modified AgNPs was presented for convenient and portable detection of CA in urine. By detecting the absorption of the solution color, the quantitative detection of CA can be achieved. The pH value of SDS-AgNPs, concentration of Al³⁺ and incubation time were optimized. Under optimal conditions, the method has the detection range of 1-10 mg/L, with a limit of detection (LOD) of 0.21 mg/L. Moreover, a self-developed portable CD(Compact Disk)-spectrometer (CDs) was established for detecting CA with a LOD of 0.49 mg/L featuring high simplicity, low time cost and good portability. This method was also validated with good selectivity to CA. In addition, the artificial urine samples were also detected to verify the capability of the method and CDs. The results validated that the method integrating with the CDs can be a promising platform for citric acid detection that can be further used for early screening and prognostic monitoring of urolithiasis.

Integration of Aspergillus niger transcriptomic profile with metabolic model identifies potential targets to optimise citric acid production from lignocellulosic hydrolysate

BACKGROUND

Citric acid is typically produced industrially by Aspergillus niger-mediated fermentation of a sucrose-based feedstock, such as molasses. The fungus Aspergillus niger has the potential to utilise lignocellulosic biomass, such as bagasse, for industrial-scale citric acid production, but realising this potential requires strain optimisation. Systems biology can accelerate strain engineering by systematic target identification, facilitated by methods for the integration of omics data into a high-quality metabolic model. In this work, we perform transcriptomic analysis to determine the temporal expression changes during fermentation of bagasse hydrolysate and develop an evolutionary algorithm to integrate the transcriptomic data with the available metabolic model to identify potential targets for strain engineering.

RESULTS

The novel integrated procedure matures our understanding of suboptimal citric acid production and reveals potential targets for strain engineering, including targets consistent with the literature such as the up-regulation of citrate export and pyruvate carboxylase as well as novel targets such as the down-regulation of inorganic diphosphatase.

CONCLUSIONS

In this study, we demonstrate the production of citric acid from lignocellulosic hydrolysate and show how transcriptomic data across multiple timepoints can be coupled with evolutionary and metabolic modelling to identify potential targets for further engineering to maximise productivity from a chosen feedstock. The in silico strategies employed in this study can be applied to other biotechnological goals, assisting efforts to harness the potential of microorganisms for bio-based production of valuable chemicals.

The chemical-microbial release and transformation of arsenic induced by citric acid in paddy soil

Citric acid (CA) is the major exudate of rice roots, yet the effects of CA on arsenic (As) transformation and microbial community in flooded paddy soil have not been clearly elucidated. In this study, microcosms were established by amending CA to As contaminated paddy soils, mimicking the rhizosphere environment. Results showed that 0.5% CA addition significantly enhanced As mobilization after one-hour incubation, increased total As in porewater by about 20-fold. CA addition induced arsenate release into porewater, and subsequently formed ternary complex of As, iron and organic matters, inhibiting further As transformation (including arsenate reduction and arsenite methylation). Furthermore, the results of linear discriminant analysis (LDA) effect size (LEfSe) and network analysis revealed that CA addition significantly enriched bacteria associated with arsenic and iron reductions, such as Clostridium (up to 35-fold) and Desulfitobacterium (up to 4-fold). Our results suggest that CA exhibits robust ability to mobilize As through both chemical and microbial processes, increasing the risk of As accumulation by rice. This study sheds light on our understanding of As mobilization and transformation in rhizosphere soil, potentially providing effective strategies to restrict As accumulation in food crops by screening or cultivating varieties with low CA exuding.

Citric acid assisted hydrothermal pretreatment for the extraction of pectin and xylooligosaccharides production from cocoa pod husks

The main purpose of this work was the development of a new citric acid assisted hydrothermal pretreatment of cocoa pod husks (CPH), which has not yet been exploited for pectin recovery. CPH́s pectin recovery was improved with concomitant production of xylooligosaccharides (XOS) through efficient enzymatic hydrolysis of the solid fraction. A central composite experimental design was planned to analyze the effect of pretreatment conditions. Under optimal conditions at 120 °C, 10 min and 2% w.v^-1, the recovery of pectin accounted for 19.3% of the biomass submitted to pretreatment with 52.2% of methyl esterification degree. Additionally, 51.9 mg.g^-1 of XOS were also produced. The enzymatic conversion efficiency of the cellulosic fraction was 58.9%, leading to a production of 92.4 kg of glucose per ton of CPH. Great perspectives were observed in the implementation of CPH hydrothermal pretreatment for the production of value-added biomolecules under a biorefinery concept.

Rational development and evaluation of novel formulations for urinary health

OBJECTIVE

Urinary tract infections (UTI) among women form a substantial part of medical practice and both patients and medical professionals have an interest in non-antibiotic treatments and preventative measures. This research provides preliminary data on a multi-functional composition, DAPAD, which explored several biologic activities of relevance to UTI.

STUDY DESIGN

This formulation included D-mannose, citric acid, three prebiotic compounds, and extracts of dandelion and astragalus. Studies performed employed 4 bacterial strains that have relevance to UTI including E. coli, Proteus mirabilis, Streptococcus agalactiae and Enterococcus faecalis.

RESULTS

Key findings from in vitro studies included: DAPAD at full- and half-strength inhibited growth of all UTI bacteria. Evidence for D-mannose agglutination of E. coli was demonstrated. D-mannose also showed unexpected effects on bacterial membrane integrity with vital staining and modest growth restriction. We did not demonstrate growth inhibition by dandelion or astragalus extracts but the latter showed diminished cytokine elaboration by bladder epithelial cells.

CONCLUSION

DAPAD is a multifunctional composition that may warrant further development as a UTI treatment or preventive if supported by clinical evaluation.

Filamentous fungal applications in biotechnology: a combined bibliometric and patentometric assessment

BACKGROUND

Processes and products employing filamentous fungi are increasing contributors to biotechnology. These organisms are used as cell factories for the synthesis of platform chemicals, enzymes, acids, foodstuffs and therapeutics. More recent applications include processing biomass into construction or textile materials. These exciting advances raise several interrelated questions regarding the contributions of filamentous fungi to biotechnology. For example, are advances in this discipline a major contributor compared to other organisms, e.g. plants or bacteria? From a geographical perspective, where is this work conducted? Which species are predominantly used? How do biotech companies actually use these organisms?

RESULTS

To glean a snapshot of the state of the discipline, literature (bibliometry) and patent (patentometry) outputs of filamentous fungal applications and the related fields were quantitatively surveyed. How these outputs vary across fungal species, industrial application(s), geographical locations and biotechnological companies were analysed. Results identified (i) fungi as crucial drivers for publications and patents in biotechnology, (ii) enzyme and organic acid production as the main applications, (iii) Aspergillus as the most commonly used genus by biotechnologists, (iv) China, the United States, Brazil, and Europe as the leaders in filamentous fungal science, and (v) the key players in industrial biotechnology.

CONCLUSIONS

This study generated a summary of the status of filamentous fungal applications in biotechnology. Both bibliometric and patentometric data have identified several key trends, breakthroughs and challenges faced by the fungal research community. The analysis suggests that the future is bright for filamentous fungal research worldwide.

Changes in TCA cycle and TCA cycle-related metabolites in plasma upon citric acid administration in rats

Recent studies have reported that plasma levels of tricarboxylic acid (TCA) cycle metabolites and TCA cycle-related metabolite change in patients with chronic fatigue syndrome (CFS) and in healthy humans after exercise. Exogenous dietary citric acid has been reported to alleviate fatigue during daily activities and after exercise. However, it is unknown whether dietary citric acid affects the plasma levels of these metabolites. Therefore, the present study aimed to investigate the effects of exogenously administered citric acid on TCA cycle metabolites and TCA cycle-related metabolites in plasma. Sprague-Dawley rats were divided into control and citric acid groups. We evaluated the effect of exogenous dietary citric acid on the plasma TCA cycle and TCA cycle-related metabolites by metabolome analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS). TCA cycle metabolites, including plasma citrate, cis-aconitate, and isocitrate, were significantly elevated after exogenous administration of citric acid. Anaplerotic amino acids, which are converted to TCA cycle metabolites, such as serine, glycine, tryptophan, lysine, leucine, histidine, glutamine, arginine, isoleucine, methionine, valine, and phenylalanine, also showed significantly elevated levels. Citric acid administration significantly increased the levels of initial TCA cycle metabolites in the plasma. This increase after administration of citric acid was shown to be opposite to the metabolic changes observed in patients with CFS. These results contribute novel insight into the fatigue alleviation mechanism of citric acid.

Property improvement of biodegradable citric acid-crosslinked rice starch films by calcium oxide

Due to several important limitations for packaging applications of starch film such as strength and hydrophilicity, rice starch (Oryza sativa) film was crosslinked with citric acid and modified by different contents of calcium oxide. FTIR spectra showed the evidence of crosslinking by citric acid and the presence of calcium oxide in the modified rice starch films. After the crosslinking, the decrease of degree of crystallinity and swelling including the increase of film smoothness and strain at maximum load were observed. The application of both citric acid and calcium oxide caused greater decrease of swelling, moisture uptake as well as higher stiffness and antibacterial activity than those of the use of only the citric acid. The highest stiffness and antibacterial activity were found for the crosslinked film added by 5 wt% calcium oxide. Moreover, the effect of calcium oxide contents on morphological, thermal and biodegradable properties of the crosslinked films was also investigated.

Efficacy of titanium brush, 915 nm diode laser, citric acid for eradication of Staphylococcus aureus from implant surfaces

BACKGROUND

This study aimed to assess the efficacy of titanium brush, 915 nm diode laser, citric acid and the combination of latter two with titanium brush for decontamination of SLA surface mini-implants.

METHODS

Seventy-five mini-implants contaminated with Staphylococcus aureus (S. aureus) were randomly divided into five experimental groups (n = 12) of titanium brush (TiB), laser, citric acid (CA), brush-laser, and brush-acid, positive [n = 12; chlorhexidine mouthwash (CHX)] and negative [n = 2; phosphate buffered saline (PBS)] control groups and one no-treatment group (n = 1). After counting the colony forming units (CFUs), data were analyzed using the Kruskal-Wallis and Dunn post-hoc tests.

RESULTS

Regardless of the no-treatment and negative control groups, maximum and minimum CFUs were noted in the titanium brush and positive control groups. After CHX, minimum CFUs were noted in brush-acid group followed by brush-laser, laser, and acid groups. Generally, the Kruskal-Wallis test revealed a significant difference between the groups regarding the colony count (P < 0.001). Dunn post-hoc test showed that the difference between the titanium brush and acid-brush group was significant (P < 0.001) while the differences between the brush and laser groups with the brush-laser group were not significant (P > 0.077).

CONCLUSIONS

Combined use of titanium brush and citric acid yielded superior results compared to other groups in reduction of S. aureus on implant surface.

Adulteration of sucrose with citric acid: Effect on reinforcing value, examined using an adjusting-magnitude schedule of reinforcement

According to the Multiplicative Hyperbolic Model (MHM), the value of a reinforcer is an increasing hyperbolic function of its size (q). Recently reported results indicated that dilution of a sucrose solution reduced its reinforcing value by increasing the 'size-sensitivity' parameter of this function and reducing its maximum. The present experiment examined whether adulterating a sucrose solution with citric acid would have a similar effect on the hyperbolic function. Rats were trained under an adjusting-magnitude schedule in which a response on lever B delivered a fixed volume of a sucrose/citric-acid mixture, while a response on lever A delivered a sucrose solution, the volume of which, q_A, was adjusted according to the rats' choices. When B was preferred in a given block of trials, q_A was increased in the following block; when A was preferred, q_A was reduced in the following block. q_B was varied across four phases of the experiment and the corresponding indifference magnitudes of A were measured. The results failed to support the hypothesis that adulteration with citric acid resulted in devaluation of sucrose. An alternative hypothesis derived from MHM, that the value of the mixture reflected the summation of positive (sucrose) and negative (citric acid) values, is discussed.

Warrior's armor: Study on the aging of sulfidated micro-sized zero valent iron in air and its subsequent reactivity for chloramphenicol degradation in different acid systems

In the practical application process, the reactivity and performance of ZVI-based materials when being placed in the air for a few days, weeks or months was worth studying. Most studies on the aging of ZVI were carried out in solution, only considering the reactivity of ZVI in aqueous solution. In this work, we investigated the degradation of chloramphenicol (CAP) in sulfuric acid (SA) and citric acid (CA) systems by sulfidated micro-sized zero-valent iron (S-mZVI) in air with different aging days. The results showed that with the increase of aging days in the air, the degradation effect of S-mZVI on CAP in different acid systems showed a similar trend (first increasing and then decreasing), the removal effect of S-mZVI on CAP reached the best within the aging time of 5-9 days. The degradation path of CAP could be divided into oxidation path and reduction path. The XPS and XRD characterization results of the materials on different aging days indicated that the characteristic peak of Fe₃O₄ was detected on the surface of the materials with the increase of aging days, which may be the reason for changing degradation efficiencies of CAP by S-mZVI for different aging days. In addition, in different systems of SA and CA, the degradation curves of CAP differed. This might be caused by two reasons: (1) CA could adsorb on S-mZVI while SA could not; (2) The initial pH of the CA system played a more significant effect on CAP degradation compared to that of the SA system.

Optimization of citric acid production by Aspergillus niger using two downgraded Algerian date varieties

In the present work, the GHARS and the MECH DEGLA downgraded date varieties were used in a fermentation medium in order to produce citric acid by the Aspergillus niger. The biochemical characteristics of the dates were investigated, along with the chemical and physical characteristics of the solutions of both samples. The analyzed parameters included the moisture and sugar content, the ash residual, the pH values, and the electrical conductivity. The effect of the following fermentation parameters was studied: initial pH, temperature, incubation period, and methanol. For the GHARS and MECH DEGLA date varieties respectively, the ash residual measured at 1.90% and 2.47%. For each date variety, the moisture and total sugars were measured at 11.59% and 85%, for the GHARS, and 12.82% and 80.47% for the MECH DEGLA. Citric acid production using either of the two varieties of dates showed a high yield in a short time. The obtained results showed that the highest production of citric acid by both medium of dates was achieved at the initial pH value of 3.0, temperature 30 °C, and an incubation period of 8 days. Also, the maximum amount of citric acid was produced when both mediums contained 4% of methanol. Both varieties of dates showed a good yield for the citric acid and can be used as a culture medium since they are economic and ensure good growth for the Aspergillus niger.

Bioremediation of hemotoxic and oxidative stress induced by polyethylene microplastic in Clarias gariepinus using lycopene, citric acid, and chlorella

Despite extensive research on the toxic effects of microplastics (MPs), there is no obtainable data on the use of phytobioremediation against MPs toxicity in fish. This study aimed to investigate the protective role of lycopene, citric acid, and chlorella against the toxic effects of MPs in African catfish (Clarias gariepinus) using hematology, biochemical, antioxidants, erythron profiles (poikilocytosis and nuclear abnormalities) and the accumulation of MPs in tissues as biomarkers. Five groups of fish received: normal diet (control); MPs (500 mg/kg diet) (Group 2); MPs (500 mg/kg diet) + lycopene (500 mg/kg diet) (Group 3); MPs (500 mg/kg diet) + citric acid (30 g/kg diet) (Group 4); and MPs (500 mg/kg diet) + chlorella (50 g/kg diet) (Group 5) for 15 days. Group 2 had significantly higher amounts of MPs in the stomach, gills, and feces, electrolyte imbalances (HCO₃, Fe, Na⁺, K⁺, Ca⁺², Cl^-, and anion gap, hematobiochemical alterations, and decreases in the activities of superoxide dismutase, catalase, total antioxidant capacity, and glutathione S-transferases compared to the control group. Additionally, Group 2 had significant increase in the percentage of poikilocytosis, and nuclear abnormalities in RBC's compared to the control group. The co-treatment of MPs-exposed fish with lycopene, citric acid, and chlorella-supplemented diets ameliorated the hematological, biochemical, and erythron profile alterations, but only slightly enhanced the antioxidant activity. Overall, lycopene, citric acid, and chlorella can be recommended as a feed supplement to improve hematobiochemical alterations and oxidative damage induced by MPs toxicity in the African catfish (C. gariepinus).

Effect of smear layer removal agents on the microhardness and roughness of radicular dentin

Purpose

To evaluate the effect of phytic acid (IP6) on the surface roughness and microhardness of human root canal dentin and compare it to other smear layer removal agents.

Materials and methods

Fifty extracted human maxillary incisors were sectioned longitudinally into a total of 100 specimens followed by embedding in auto-polymerizing acrylic resin. The specimens were polished and then randomly divided into five groups (n = 20) according to the test solution used to condition root canal dentin: 17% ethylenediaminetetraacetic acid (EDTA); 10% citric acid (CA); 1% IP6; 37% phosphoric acid (PA); or distilled water (control group). Each specimen was treated with a total volume of 1 ml of each solution for 1 min with agitation. Each group was then divided into two subgroups of 10 specimens each. The specimens of the first subgroup were used to determine microhardness, using Vickers hardness tester, and the specimens of the second subgroup were used to measure surface roughness, using a confocal laser scanning microscope. The results were analyzed statistically using one-way ANOVA and Tukey tests, α = 0.05.

Results

All the tested groups exhibited microhardness and surface roughness values that were statistically significantly different when compared with the control group (P < 0.05). The microhardness value obtained with IP6 was significantly lower when compared to EDTA, CA, and the control group, whereas its roughness value was significantly higher compared to the aforementioned groups. However, there was no significant difference between IP6 and PA (P > 0.05).

Conclusions

IP6 and PA showed the lowest microhardness and the highest surface roughness values.

"Turn-on" ratiometric fluorescent probe: Naked-eye detection of acidic pH and citric acid (CA) by using fluorescence spectrum and its application in real food samples and zebrafish

Rapid, accurate and efficient detection of acidic pH and citric acid (CA) changes is of great significance for predicting environmental and food safety problems by fluorescence analysis technique. Herein, a small molecule ratiometric fluorescent probe (BICL) based on benzoindole derivatives is successfully synthesized and characterized and used for quantitatively and qualitatively "turn-on" detection acid pH and CA changes in solution and environment by ultraviolet spectrum and fluorescence emission spectrum. On the one hand, the probe has a good linear relation to acidic pH in the pH range 3.1-4.5 (I₆₀₄/I₅₅₀ = 13.088-2.3878pH, R² = 0.9986). On the other hand, the probe has a good linear relationship in the range of CA concentration of 14.0-23.0 μM (I₆₀₄/I₅₅₀ = 0.5324 [CA]-5.2628, R² = 0.9993) and a low detection limit of 2.967 μM. BICL has a good recovery rate in the range of 114.6 ~ 101.0% and a low relative standard deviation (RSD) (0.0011 ~ 0.0092) in the determination of CA in real samples (water, drinks and fruits), which holds great potential for application in determination of CA in real samples. Importantly, the probe has good blood compatibility, and it has been successfully applied to detect exogenously induced changes in acidic pH and CA in zebrafish with great time-stability by using fluorescence imaging technology, respectively.

Candidates for smart cardiovascular medical device coatings: A comparative study with endothelial and smooth muscle cells

Stent-induced vascular injury is manifested by removal of the endothelium and phenotypic changes in the underlying medial smooth muscle cells layer. This results in pathological vascular remodelling primarily contributed to smooth muscle cell proliferation and leads to vessel re-narrowing; neointimal hyperplasia. Current drug-eluting stents release non-selective anti-proliferative drugs such as paclitaxel from the stent surface that not only inhibit growth of smooth muscle cells but also delay endothelial healing, potentially leading to stent thrombosis. This highlights the need for novel bioactive stent coating candidates with the ability to target key events in the pathogenesis of in-stent restenosis. Citric acid, a molecule with anti-coagulant properties, was investigated against L-ascorbic acid, an antioxidant molecule reported to preferentially promote endothelial growth, and paclitaxel, a typically used anti-proliferative stent coating. Citric acid was found to exhibit growth supporting properties on endothelial cells across a range of concentrations that were significantly better than the model stent coating drug paclitaxel and better than the ascorbic acid which inhibited endothelial proliferation at concentrations ≥100 μg/ml. It was demonstrated that a citric acid-paclitaxel combination treatment significantly improves cell viability in comparison to paclitaxel only treated cells, with endothelial cells exhibiting greater cell recovery over smooth muscle cells. Furthermore, cell treatment with citric acid was found to reduce inflammation in a lipopolysaccharide (LPS)-induced in vitro inflammation model by significantly reducing interleukin 6 expression. Thus, this study demonstrates that citric acid is a promising candidate for use as a coating in stents and other endovascular devices.

Comparative Evaluation of the Effects of Antimicrobial Photodynamic Therapy With an LED and a Laser on the Proliferation of Human Gingival Fibroblasts on the Root Surface: An In Vitro Study

Introduction: This study aimed to compare the effects of root biomodification by citric acid and antimicrobial photodynamic therapy (aPDT) with LED and laser on the proliferation of human gingival fibroblasts (HGFs). Methods: This in vitro experimental study evaluated 60 single-rooted teeth extracted due to periodontal disease. The teeth underwent scaling and root planing (SRP), and then 5 × 5 mm blocks were prepared from the cervical area of the teeth 1 mm apical to the cementoenamel junction. The blocks were divided into 4 groups (n=15 blocks): SRP alone (control), SRP + citric acid, SRP + toluidine blue (TBO) + LED light, and SRP + TBO + laser. HGFs were seeded on the surface of the samples, and the methyl thiazolyl tetrazolium (MTT) assay was performed after 24, 48 and 72 hours. Group comparisons were performed using repeated measures ANOVA, while pairwise comparisons of the time points were performed by an LSD test. Results: Cell proliferation was higher in all experimental groups at 48 and 72 hours, compared with 24 hours (P < 0.05). Cell proliferation was significantly different in the citric acid group at 24 hours (P = 0.016) and 48 hours (P = 0.015), compared with other groups. However, cell proliferation was not significantly different in the aPDT group with LED Photosan and a diode laser at 24 and 48 hours (P > 0.05). Conclusion: aPDT and citric acid can enhance the proliferation of HGFs on dentin blocks. Further studies can pave the way for their future use in the clinical setting.

Remediation of zinc-contaminated soils by using the two-step washing with citric acid and water-soluble chitosan

Remediation of heavy metal contaminated soil with appropriate washing agents is crucial to the decline in the harmfulness of contaminated soil by heavy metals to the environment and human health. In this study, citric acid (CA) and water-soluble chitosan (WSCS) as natural and degradable washing agents were used to remove Zn in the soil by two-step washing method. Results indicated that the two-step washing with CA and WSCS were found to be suitable for the removal of Zn from the contaminated soils, which significantly decreased the total concentration of Zn in the soil. After the remediation process with two-step soil washing, the contents of Zn in different chemical species decreased, especially for the carbonate-bound fraction. Therefore, the two-step soil washing with CA and WSCS was advisable for the remediation of Zn-contaminated soils. The washing mechanism could include the acid dissolution, ion exchange and complexation reaction between zinc ions and functional groups such as hydroxyl, carboxyl, amine and amide groups. This study provided the theoretical support for the exploitation and application of suitable washing agents used for the remediation of contaminated soils by heavy metals.

Efficacy of Lemna minor and Typha latifolia for the treatment of textile industry wastewater in a constructed wetland under citric acid amendment: A lab scale study

Lead (Pb), copper (Cu) and chromium (Cr) are one of the most harmful heavy metals (HMs), entering into the food chain through the irrigation of crops with an industrial effluent. The present study was performed to evaluate the toxic effects of textile effluents and performance of citric acid (CA) on phytoextraction potential of Lemna minor L. and Typha latifolia L. in an artificially designed wetland. Different doses of textile wastewater (0, 25, 50, 75, and 100%) and CA (10 mM) were applied alone and in combination. Plants were harvested and the data was collected regarding agronomic traits, photosynthetic pigments, antioxidant enzymes, reactive oxygen species (ROS), electrolytic leakage (EL) and HMs uptake and accumulation. The results depicted that the concentration and accumulation of Cu, Pb and Cr in different parts of T. latifolia plant was increased with and without CA addition. The maximum concentration of Pb, Cu and Cr increased in leaves by 279, 240 & 171%, in stem by 192, 172 & 154%, and in roots by 224, 183 & 168%, respectively. Similarly, the accumulation of Pb, Cu and Cr increased in leaves by 91, 71 & 36%, in stem by 57, 46 & 36% and in roots by 76, 53 & 45%, respectively in plants treated with 100% textile effluent as compared to the 25% textile effluent treated plants under CA amendment. In L. minor, the concentration of Pb, Cu & Cr increased by 542, 411 and 397% while accumulation increased by 101, 59 & 55% respectively in overall plant biomass.

Adsorption characteristics of citric acid on Fe3O4 (001), (011), and (111) surfaces

Magnetite (001), (011), and (111) surfaces were the focus of our study. Magnetite (001) surface has two different terminations, that is, Fe_tet and 2Fe_oct4O. Magnetite (011) surface has two different terminations, that is, 2Fe_oct4O and 2Fe_tet2Fe_oct4O. Magnetite (111) surface has six different terminations, that is, Fe_tet1, Fe_oct, Fe_tet2, 3Fe_oct, 4O₁, and 4O₂. Comparing surface energies of (001), (011), and (111) surfaces, (001) has the smallest surface energy, and (111) has the largest surface energy except for Fe_oct termination, which means that (001) surface is the easiest to be cleaved, followed by (011) and (111) surfaces. Comparing adsorption energies of citric acid onto (001), (011), and (111) surfaces, (111) has the largest adsorption energies except for Fe_tet2 termination, and (001) has the smallest adsorption energies, which means that (111) surface is the most active for citric acid adsorption, followed by (011) and (001) surfaces. PDOS (partial density of states) of citric acid adsorbed onto (001), (011), and (111) surfaces with different terminations shows that 3d orbital of Fe of magnetite surface does not contribute to the adsorption, and 4s orbital of Fe of magnetite surface and 2s and 2p orbitals of O of citric acid contribute to the adsorption.