Structure and properties of two glucose-based deep eutectic systems

Continued industrialization and increasing environmental problems have highlighted the need to research new eco-friendly solvents, also known as deep eutectic solvents (DESs). To implement these solvents in industrial processes, the knowledge of their molecular organization and thermophysical properties must be enhanced. In this work, two DESs have been characterized: d-glucose:choline chloride:water (GCH) and d-glucose:citric acid:water (GCiH). NMR techniques were used to analyse both the supramolecular structure and the role of water and to calculate the diffusion coefficients. Moreover, seven thermophysical properties at several temperatures were evaluated. As a second aim, the solubility of quercetin was determined. NMR studies showed a stronger supramolecular structure of GCH and a high ratio of β-glucose in both DESs. Based on the thermophysical results, the solvent with choline chloride had the most compact fluid structure. Finally, the solubility of quercetin in the DESs was higher than in water, especially for GCH.

Citric acid modified granular activated carbon for enhanced defluoridation

Excess fluoride (F^-, >1.5 mg F^-/L) in drinking water affects >260 million people across the globe and leads to dental and skeletal fluorosis. In this study, commercially available granular activated carbon (GAC) was modified with 0.3 M citric acid to get citric acid modified GAC (CAGAC). Over 70% of fluoride was removed in the first 60 min by CAGAC, whereas unmodified GAC removed only 30%. There were negligible interferences by co-existing ions (NO₃^-, Cl^-, HCO₃^-, SO₄^2-_, PO₄^3-) and organic matters. Maximum adsorption capacity of CAGAC was two times (1.65 mg/g) that of unmodified GAC (0.88 mg/g). Dubinin-Radushkevich (D-R) isotherm described the experimental data well indicating that ion exchange was involved in fluoride removal. CAGAC worked effectively over a wide range of pH (2-10) even though the point-of-zero-charge (PZC) was 4.89, and so the removal was not controlled by electrostatic interaction alone; surface adsorption and intra-particle diffusion were the rate-determining processes.

Multiscale structural evolution of citrate-triggered intrafibrillar and interfibrillar mineralization in dense collagen gels

The mineralized extracellular matrix of bone is an organic-inorganic nanocomposite consisting primarily of carbonated hydroxyapatite, fibrous type I collagen, noncollagenous proteins, proteoglycans, and diverse biomolecules such as pyrophosphate and citrate. While much is now known about the mineralization-regulating role of pyrophosphate, less is known about the function of citrate. In order to assess the effect of negatively charged citrate on collagen mineralization, citrate-functionalized, bone osteoid-mimicking dense collagen gels were exposed to simulated body fluid for up to 7 days to examine the multiscale evolution of intra- and interfibrillar collagen mineralization. Here, we show by increases in methylene blue staining that the net negative charge of collagen can be substantially augmented through citrate functionalization. Structural and compositional analyses by transmission and scanning electron microscopy (including X-ray microanalysis and electron diffraction), and atomic force microscopy, all demonstrated that citrate-functionalized collagen fibrils underwent extensive intrafibrillar mineralization within 12 h in simulated body fluid. Time-resolved, high-resolution transmission electron microscopy confirmed the temporal evolution of intrafibrillar mineralization of single collagen fibrils. Longer exposure to simulated body fluid resulted in additional interfibrillar mineralization, all through an amorphous-to-crystalline transformation towards apatite (assessed by X-ray diffraction and attenuated total reflection-Fourier-transform infrared spectroscopy). Calcium deposition assays indicated a citrate concentration-dependent temporal increase in mineralization, and micro-computed tomography confirmed that >80 vol% of the collagen in the gels was mineralized by day 7. In conclusion, citrate effectively induces mesoscale intra- and interfibrillar collagen mineralization, a finding that advances our understanding of the role of citrate in mineralized tissues.

Comparison of Effect of pH Modulation on Wound Healing with Topical Application of Citric Acid Versus Superoxide Ions

Background:

Wound healing is a dynamic process involving tissue repair and regeneration. Nonhealing and chronic wounds are a significant health problem that many patients all over the world are suffering from. Proper wound care is hence very important. Wound dressings have undergone continuous and significant changes over the time period. Optimal dressing should ensure a moist wound bed, help drainage, remove debris, and be anti-allergic and without immunogenicity.

Objectives:

The objective of the study is compare the effect of pH modulation on wound healing with topical application of citric acid versus superoxide ions. The aim is to study the efficacy and safety of citric acid versus superoxide ions in the prevention and control of infection and their effect on wound healing in similar wound types.

Materials and Methods:

We conducted randomized, prospective comparative study in a total of 100 patients admitted at Guru Nanak Dev Hospital, attached to Government Medical College, Amritsar. The patients were divided into two groups: Group A where wound management was done using superoxide ions and Group B where citric acid was used. A standard grading was done in terms of a decrease in wound size, an increase in granulation tissue, and a reduction in wound discharge.

Results:

The wounds treated with citric acid showed an average reduction in wound size of 73.43% by the 14^th day as compared to 66.52% in the control group. The difference seen in the average reduction of wound size was statistically significant (P = 0.032). The wounds treated by citric acid application showed an average increase in granulation tissue of 56.66% as compared to 50.87% in the wounds treated by superoxide ions. The average hospital stay in patients of Group B was comparatively less than that of patients in Group A.

Conclusion:

Citric acid is safe and effective in all types of wound management and gives better efficacy and faster response as compared to superoxide ions. Citric acid promotes wound healing by the formation of granulation tissue and fibroblast proliferation.

A WO3/PPy/ACF modified electrode in electrochemical system for simultaneous removal of heavy metal ion Cu2+ and organic acid

Heavy metal ions and organic acids are common pollutants in electroplating wastewater. Effective and economic treatment of such wastewater needs novel technologies. In this study, WO₃/PPy-1/ACF electrode was prepared using a hydrothermal modification method and it has large specific area (788.27 m² g^-1), high areal capacitance (2.58 F cm^-2 under 5 mA cm^-2 charge and discharge) and excellent conductivity. The modified electrode was used in an electrochemical system with activated carbon fiber felt (ACF) as counter electrode. The system simultaneously and successfully removed 97.8 % Cu²⁺ and 80.1 % citric acid (CA) from a simulated electroplating wastewater (typically 100 mg L^-1 Cu²⁺ and 800 mg L^-1 CA) in five- hour optimized operation. The influence of operating parameters (circulating inflow rate, applied voltage and influent pH) on the treatment performance was compared. There is interplay between Cu²⁺ reductive deposition and CA oxidation. The synergetic electrochemical treatment mechanism involves formation of hydrogen peroxide, free radicals, and catalytic effect of Cu species was proposed. This electrochemical system which is low-cost, easy to operate and highly efficient, may be applicable in treating acid-wash or electroplating wastewater, containing heavy-metal ions and organic acids.

Effect of citric acid addition on functional properties of pasteurized liquid whole eggs

The aim of this study was to examine the influence of different concentrations of citric acid (0, 300, 400 and 500 mg/L) on the physical and functional properties of pasteurized liquid whole eggs (LWE) over 4 weeks of storage. The properties tested include pH, conductivity, colour, particle size, rheological, and textural properties, as well as protein solubility, foaming and emulsification. The 4 weeks of storage had a statistically significant (P < 0.05) effect on every tested parameter, while the addition of citric acid had a statistically significant (P < 0.05) effect on pH, conductivity, L^* and b^* values, protein solubility, emulsion activity index, emulsion capacity, emulsion stability, and an increase in foaming and texture parameters, but not on rheological parameters. Citric acid addition and a storage period of 4 weeks resulted in a change of pH and an increase in protein solubility. It also led to a lower foaming capacity and a larger drainage of the system, which causes a lower power (work load) requirement to break formed gels. Apparent viscosity did not change significantly in the samples with citric acid.

Novel multifunctional ion exchangers for metal ions removal in the presence of citric acid

The present study deals with the potential application of Purolite S957 and Diphonix Resin® for the removal of rare earth elements from aqueous liquors as a result of the extraction of spent Ni-MH batteries in the presence of citric acid. The effects of the metal ion and the citric acid ratio, pH, ion exchanger dose, contact time, initial concentration and temperature were studied using the batch technique. The Langmuir and Freundlich adsorption isotherm models were used for the description of the adsorption process. The equilibrium adsorption data were fitted using the pseudo first order, pseudo second order, intraparticle diffusion, Boyd, film diffusion and Dumwald-Wagner models. The maximum adsorption capacity q₀ obtained from the Langmuir isotherm was found to be 46.63 mg/g for Ni(II) and 60.75 mg/g for La(III) on Purolite S957 as well as 46.55 mg/g for Ni(II) and 60.12 mg/g for La(III) on Diphonix Resin®. The kinetics followed the pseudo second order reaction. Based on the Weber-Morris model the adsorption process proved to proceed in two stages. Based on the Boyd model the rate controlling steps were film and intraparticle diffusions. The adsorption process was spontaneous and endothermic in nature. Reusability of ion exchangers in the desorption studies was also evaluated as a sustainable approach. The physicochemical properties of Purolite S957 and Diphonix Resin® were studied using the ASAP analysis, optical and scanning electron microscopy, potentiometric titration, pH_PZC and FT-IR as well as XPS analysis.

Citric acid enhanced phytoextraction of nickel (Ni) and alleviate Mentha piperita (L.) from Ni-induced physiological and biochemical damages

Phytoremediation is considered one of the well-established and sustainable techniques for the removal of heavy metals and metalloids from contaminated sites. The metal extraction ability of the plants can be enhanced by using suitable organic materials in combination with metal-tolerant plants. This experiment was carried out to investigate the phytoextraction potential of Mentha piperita L. for nickel (Ni) with and without citric acid (CA) amendment in hydroponic experiment. The experiment was performed in controlled glass containers with continuous aeration in complete randomized design (CRD). Juvenile M. piperita plants were treated with different concentrations of Ni (100, 250, and 500 μM) alone and/or combined with CA (5 mM). After harvesting the plants, the morpho-physiological and biochemical attributes as well as Ni concentrations in different tissues of M. piperita plants were measured. Results revealed that Ni stress significantly decreased the plant agronomic traits, photosynthesis in comparison to control. Nickel stress enhanced the antioxidant enzymes activities and caused the production of reactive oxygen species (ROS) in M. piperita. The CA treatment under Ni stress significantly improved the plant morpho-physiological and biochemical characteristics when compared with Ni treatments alone. The results demonstrated that CA enhanced the Ni concentrations in roots, stems, and leaves up to 138.2%, 54.2%, and 38%, respectively, compared to Ni-only-treated plants. The improvement in plant growth with CA under Ni stress indicated that CA is beneficial for Ni phytoextraction by using tolerant plant species. Graphical abstract.

Effects of citric acid on fermentation characteristics and bacterial diversity of Amomum villosum silage

To study the effects of citric acid on fermentation process of Amomum villosum silage, A. villosum was ensiled without or with 1%, 2% citric acid and fermentation parameters and bacterial diversity were analyzed after 3, 7, 14, 30 days ensiling, respectively. Citric acid treated silages had lower dry matter loss (1.83% vs 2.23%), pH (3.84 vs 6.02), ammonia-N (0.33 vs 1.79 g/kg DM) and coliform bacteria number (<2.00 vs 7.27 log₁₀ CFU/g FM) than the control after 30 days ensiling. The relative abundance of lactic acid bacteria, Pediococcus and Lactobacillus increased, whereas undesirable microorganisms like Enterobacter, Escherichia-Shigella and Pantoea decreased in citric acid treated A. villosum silage. These results indicated that quality A. villosum silage could be obtained by citric acid addition.

Disruption and overexpression of 6-phosphofructo-2-kinase influence organic acid production in Aspergillus carbonarius ITEM 5010

Aspergillus carbonarius is an efficient producer of organic acids with great potential for bio-based production of organic acids. In this study, we identified a gene f2kp encoding the enzyme 6-phosphofructo-2-kinase known as an allosteric regulator of the glycolytic flux and investigated its role in the production of organic acid. The strategy was to examine the impact of citric acid and malic acid production by overexpressing and disrupting f2kp, respectively. The overexpressing transformants expressed f2kp at higher level than the wild type, whereas no expression of f2kp was detected in the knockout transformants. Citric acid and malic acid production by the knockout strains decreased sharply along with a significant lower sugar consumption, though the overexpressing transformants produced similar amounts of citric acid and malic acid as the wild type. We conclude that 6-phosphofructo-2-kinase has an important regulatory role for the glycolytic flux and organic acid production in A. carbonarius.

Effects of nano fish bone on gelling properties of tofu gel coagulated by citric acid

Tofu gel was made by using citric acid (0.14%) in combination with varied volumetric ratios (e.g., 0-4%) of nano fish bone (NFB). The gel properties were investigated by colorimetry, penetration tests, scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy. As the volumetric ratio increased from 0 to 3%, the soluble calcium concentrations of soymilk linearly increased from 1.78 to 6.42 mg/mL. Correspondently, yield, moisture and texture values of the tofu gel increased continuously (p < 0.05) while syneresis and whiteness decreased (p < 0.05). Furthermore, ionic bonds, hydrophobic interactions and hydrogen bonds increased by 140%, 40% and 10%, respectively. With the addition of NFB, the α-helices of the soybean proteins changed to β-sheets and random coil structures. Additionally, the tofu gel network became more orderly and denser. The results confirmed that NFB can be utilized as a functional coagulant ingredient to improve the properties of acid-induced tofu gels.

Synergistic bactericidal effect and mechanism of X-ray irradiation and citric acid combination against food-borne pathogens on spinach leaves

In this study, we investigated the antimicrobial activity of the X-ray irradiation and citric acid (CA) combination against Escherichia coli O157:H7 and Listeria monocytogenes on the surface of spinach leaves and elucidated the mechanisms underlying their synergistic interaction. Upon treatment with 0.3 kGy X-ray irradiation and 1% CA combination, the cell counts of E. coli O157:H7 and L. monocytogenes reduced by 4.23 and 3.69 log CFU/mL on spinach leaves, respectively. The synergistic reduction in the cell counts of E. coli O157:H7 and L. monocytogenes by the combination treatment was 0.95 and 1.14 log units, respectively. The X-ray and CA combination exerts its antimicrobial effect by damaging the bacterial cell membrane and enhancing the generation of intracellular reactive oxygen species in the pathogens. The enhanced bactericidal effect of the combination treatment may not be due to the loss of intracellular enzyme activity. We also evaluated the effect of the combination treatment on the quality attributes of spinach leaves. The combination treatment did not result in adverse changes in color and texture of spinach leaves. These results demonstrate the potential of citric acid and X-ray irradiation combination for decontaminating foodborne pathogens on fresh produce.

Changes in Citric Acid Cycle and Nucleoside Metabolism Are Associated with Anthracycline Cardiotoxicity in Patients with Breast Cancer

Anthracyclines and HER2-targeted antibodies are very effective for the treatment of breast cancer, but their use is limited by cardiotoxicity. In this nested case-control study, we assessed the role of intermediary metabolism in 38 women with breast cancer treated with anthracyclines and trastuzumab. Using targeted mass spectrometry to measure 71 metabolites in the plasma, we identified changes in citric acid and aconitic acid that differentiated patients who developed cardiotoxicity from those who did not. In patients with cardiotoxicity, the magnitude of change in citric acid at three months correlated with the change in left ventricular ejection fraction (LVEF) and absolute LVEF at nine months. Patients with cardiotoxicity also demonstrated more pronounced changes in purine and pyrimidine metabolism. Early metabolic changes may therefore provide insight into the mechanisms associated with the development of chemotherapy-associated cardiotoxicity.

Dual-emission carbon dots achieved by luminescence center modulation within one-pot synthesis for a fluorescent ratiometric probe of pH, Hg2+, and glutathione

Dual-emission carbon dots were synthesized by one-pot hydrothermal pyrolysis of citric acid and polyethyleneimine in the presence of rhodamine B at 160 °C for 5 h. The carbon dots have an average diameter of 2.51 nm with rhodamine moiety on their surface. Two emission bands centered at 447 and 581 nm are exhibited in their fluorescence spectra excited at 360 nm, and the former is sensitive while the latter is insensitive to Hg²⁺ and pH. Glutathione (GSH) can recover the fluorescence quenched by Hg²⁺. Therefore, the dual-emission carbon dots were developed as a fluorescent ratiometric probe employing the ratio of the two intensities at 447 and 581 nm (R_I447/I581) as the signal for the determinations of pH, Hg²⁺, and GSH. In the range of 5.0-10.0, a good linear relationship between R_I447/I581 and pH was built with a regression equation of R_I447/I581 = 11.95-0.56 pH (R² = 0.998). In the range from 0.0 to 8.0 μM, an excellent linear relationship between R_I447/I581 and the concentration of Hg²⁺ was obtained with a calibration equation of R_I447/I581 = 6.2317-0.4458c (R² = 0.995) and a limit of detection (LOD) of 0.24 μM. In the range from 1.0 to 10.0 μM, a linear equation, R_I447/I581 = 1.9133-0.4157c (R² = 0.995), was calibrated between R_I447/I581 and the concentration of glutathione with a LOD of 0.27 μM. The recoveries for the determinations of Hg²⁺ and GSH in real samples were in the ranges of 94.6 to 103.8% and 94.3 to 104.2%, respectively. Graphical abstract Dual-emission carbon dots achieved by luminescence center modulation within one-pot synthesis for a fluorescent ratiometric probe of pH, Hg²⁺, and glutathione.

Lead-contaminated soils with contrasting texture remediated with phosphate: chemical fractionation and chloropyromorphite stability

Pb can be stabilized in soil as Pb-P mineral. The aims of this study were to access the distribution of Pb in organic and mineral fractions of contrasting texture of soil Pb-contaminated and remediated with P and Cl and to evaluate the stability of chloropyromorphite in these soils. A clay loam Oxisol (sandstone) and a clayey Ultisol (basalt) were used in a factorial experiment, with three replications: two soils, two Pb contamination levels, two soil pH values, and four P doses. The Pb concentrations were determined in seven soil phases. Release kinetics of Pb were performed with 0.1 mol L^-1 pH 2.5 citric acid. The transfer of soil Pb to chloropyromorphite was dependent on the level of contamination in the clay loam Oxisol. In the lowest P dose (molar ratios P:Pb 3:5), the main source was the Pb complexed in the organic matter and in the highest P dose (molar ratios P:Pb 12:5) was the Pb adsorbed by inner sphere in gibbsite and kaolinite. The release of Pb in the citric acid was dependent on the texture and mineralogy of the soils. Pb recovery applied to the clay loam Oxisol was around 100% (biphasic kinetic), while for the clayey Ultisol, the recovery ranged from 43 to 52% (single-phase kinetic). Remediation of Pb-contaminated soils with P and Cl is more efficient in clayey and oxidic soils since chloropyromorphite formation is faster and its solubilization is slower, an important combination in environmental terms.

Effect of citric acid on extracellular polymeric substances disruption and cell lysis in the waste activated sludge by pH regulation

This paper investigated the effects of citric acid (CA) on extracellular polymer destruction and cell lysis in sludge at different initial pH by measuring capillary suction time (CST), extracellular polymeric substances (EPS) and intracellular bound water. The results indicated that under CA concentration at 0.05 g/g suspended solids (SS) and initial pH 4, the CST value decreased from 175.5 s to 112.3 s, slime extracellular polymeric substances (S-EPS) and loosely bound EPS (LB-EPS) content respectively to increase from 4.92 to 41.43, 2.27 to 5.49 mg/g volatile suspended solids (Vss), while tightly bound EPS (TB-EPS) content to decrease from 12.35 to 5.01 mg/g (Vss), which suggested CA could disrupt outer EPS effectively. Intracellular bound water content decreased from 1.23 g/g to 0.41 g/g dry solid (DS). As a result, CA could release intracellular bound water effectively, thereby improving sludge dewatering degree.

Pachymic acid protects against cerebral ischemia/reperfusion injury by the PI3K/Akt signaling pathway

Pachymic acid (PA) from medicinal fungus Poria cocos has a variety of pharmacological potentials. However, there are no reports of the effects of PA on cerebral ischemia/reperfusion (I/R) injury. The purpose of this study was to investigate the mechanisms of PA on cerebral I/R injury in rats. The effects of PA on cerebral infarction size, brain water content, neurological symptoms and cerebral blood flow were evaluated. Nissl staining was used to observe the damage of ischemic brain neurons after I/R in rats. Apoptosis of ischemic brain neurons after I/R was observed by TUNEL staining. The effect of PA on the expression of some components of PI3K/Akt was detected by Western blotting. PA significantly increased cerebral blood flow after I/R in rats, reduced infarct volume and brain water content, and downgrade neurological function scores, significantly reduced neuronal damage after I/R in rats, and significantly decreased neuronal apoptosis. The effect of PA on rat I/R can be eliminated by LY294002. In addition, PA significantly up-regulated the protein expression of p-PTEN (Ser380), p-PDK1 (Ser241), p-Akt (Ser473), pc-Raf (Ser259) and p-BAD (Ser136), and down-regulated Cleaved caspase protein expression. LY294002 can reverse the effect of PA on the expression of PI3K / Akt signaling pathway related protein in rats after I/R. PA had obviously neuroprotective effects on brain I/R injury and neuronal apoptosis, and its mechanism may be related to activation of PI3K / Akt signaling pathway.

Increased thermal sensitivity of Listeria monocytogenes in sous-vide salmon by oregano essential oil and citric acid

Inadequate cooking during sous-vide processing may cause foodborne diseases in case the food is contaminated with pathogens such as Listeria monocytogenes. In this study, thermal inactivation of L. monocytogenes in sous-vide processed salmon was investigated. Oregano oil and citric acid were used alone or in combination to determine the probability of increasing the efficiency of heat treatment. Control (C); 0.5% citric acid added (S); 1% oregano essential oil added (O); and citric acid and oregano essential oil combined (OS) groups were prepared. Samples were inoculated with L. monocytogenes, vacuum packed, then sous-vide cooked at 55, 57.5, 60, or 62.5 °C for predetermined times. The D-values of all treated samples were significantly lower than control. The use of oregano oil (O), citric acid (S) and their combination (OS) significantly reduced the time required to inactivate L. monocytogenes. The z-values of L. monocytogenes in C, O, S and OS groups were 5.50, 5.62, 6.54, and 6.92 °C, respectively. It was determined that effective results could be achieved by adding natural antimicrobials to provide safety in sous-vide fish.

The treatment of veterinary antibiotics in swine wastewater by biodegradation and Fenton-like oxidation

Elevated concentrations and potential toxicities of antibiotics in swine wastewater prompt the exploration of effective treatment methods to minimize the amount of antibiotics released to the environment. This study examined the technical and economic feasibility of using combined biodegradation and advanced oxidation processes for swine wastewater treatment. The up-flow anaerobic sludge blanket (UASB) reactor was mainly responsible for conventional organic pollutant removal (i.e., a COD removal rate of 75%). The subsequent sequencing batch reactor (SBR) under a short sludge retention time (SRT) of 3 days removed the biodegradable antibiotics by >95%, and hindered the nitrification process which retained NH₄⁺-N and reduced operational cost (since the treated wastewater was intended to be used as a farm fertilizer). The subsequent Fenton-like oxidation (with the aid of citric acid) achieved an average antibiotic removal efficiency of 74% under optimal reaction conditions: H₂O₂ dosage of 2.9 mM, [Fe²⁺]: [H₂O₂] = 1:3, [CA]: [Fe²⁺] = 1:1, pH 6.0, reaction time of 120 min. The superior treatment efficiency of Fenton-like compared to the conventional Fenton (74% vs 5%) under nearly neutral conditions was attributed to the chelating role of citric acid with Fe²⁺/Fe³⁺, leading to the enhanced Fe²⁺/Fe³⁺ solubility and therefore the promotion of ∙OH formation. This hybrid process of anaerobic and aerobic biodegradation and Fenton-like oxidation should be suitable and cost-effective for the treatment of wastewater with abundant conventional pollutants and persistent emerging trace contaminants.

Disruption or reduced expression of the orotidine-5'-decarboxylase gene pyrG increases citric acid production: a new discovery during recyclable genome editing in Aspergillus niger

Background

Aspergillus niger is a filamentous fungus used for the majority of global citric acid production. Recent developments in genome editing now enable biotechnologists to engineer and optimize A. niger. Currently, however, genetic-leads for maximizing citric acid titers in industrial A. niger isolates is limited.

Results

In this study, we try to engineer two citric acid A. niger production isolates, WT-D and D353, to serve as platform strains for future high-throughput genome engineering. Consequently, we used genome editing to simultaneously disrupt genes encoding the orotidine-5′-decarboxylase (pyrG) and non-homologous end-joining component (kusA) to enable use of the pyrG selection/counter selection system, and to elevate homologous recombination rates, respectively. During routine screening of these pyrG mutant strains, we unexpectedly observed a 2.17-fold increase in citric acid production when compared to the progenitor controls, indicating that inhibition of uridine/pyrimidine synthesis may increase citric acid titers. In order to further test this hypothesis, the pyrG gene was placed under the control of a tetracycline titratable cassette, which confirmed that reduced expression of this gene elevated citric acid titers in both shake flask and bioreactor fermentation. Subsequently, we conducted intracellular metabolomics analysis, which demonstrated that pyrG disruption enhanced the glycolysis flux and significantly improved abundance of citrate and its precursors.

Conclusions

In this study, we deliver two citric acid producing isolates which are amenable to high throughput genetic manipulation due to pyrG/kusA deletion. Strikingly, we demonstrate for the first time that A. niger pyrG is a promising genetic lead for generating citric acid hyper-producing strains. Our data support the hypothesis that uridine/pyrimidine biosynthetic pathway offer future avenues for strain engineering efforts.

Adsorption properties and mechanisms of novel biomaterials from banyan aerial roots via simple modification for ciprofloxacin removal

The study investigated ciprofloxacin (CIP) adsorption capacity of the novel biomaterials prepared from banyan aerial roots by simple thermochemical modification. Pretreated banyan aerial root fibers were modified with a green reagent citric acid (1 M) at 90, 120 and 150 °C, which enhanced the fiber adsorption capacity revealed by characterization and adsorption tests. Several characterization methods were applied to exploring the surface morphologies and physicochemical properties of unmodified banyan aerial roots (UBARs) and modified banyan aerial roots (T-MBARs, T stands for the modification temperature). Based on SEM images and N₂ adsorption/desorption isotherms, the modification resulted in decrease of the specific surface area owing to cellulose molecular linking. In that case, the improved CIP adsorption of MBARs might be attributed to the larger carboxyl quantity and stronger electronegativity manifested via FTIR spectra and zeta potential analysis. Through the adsorption experiments, the optimal pH value of 8 and the suitable absorbent dosage of 0.03 g were obtained. The simulation results showed that the Freundlich model can fit the adsorption thermodynamic data quite well, while the kinetic data was simulated preferably by the pseudo-second-order kinetic equation signifying the chemical adsorption process, and the intra-particle diffusion was involved in the adsorption consisted of three stages. The findings of batch experiments under diverse operations represented that MBARs purified aqueous CIP better than UBARs, closely related to the superior electronegativity. Both characterization and adsorption studies illustrated the dominant role of electrostatic interaction during CIP removal, accompanied by hydrogen bonding and diffusion interaction besides. The present work suggested that MBAR fibers could possess a promising application to ciprofloxacin potent removal from aqueous solutions.

Effect of citric acid and vermi-wash on growth and metal accumulation of Sorghum bicolor cultivated in lead and nickel contaminated soil

The aim of the present study is to assess the influence of vermi-wash (VW) and citric acid (CA) on Sorghum bicolor growth and phytoaccumulation of lead (Pb) and nickel (Ni) contaminated soil. The biomass of the S. bicolor has been enhanced by the addition of VW (24 and 26%) and CA (11 and 9%) in Pb and Ni contaminated soil, respectively. The VW treatment showed enhanced shoot and root lengths and chlorophyll concentrations compared to CA. The shoot anatomic structure showed an accumulation of Pb and Ni were positively impacted by the amendment of VW and CA. In addition, VW treatment showed enhanced antioxidant enzymes activity (140, 125 and 152 U/mg of CAT, SOD and POD). Further, the plants grown in Pb contaminated soil treated with VW showed enhanced Rubisco activity of 1.49 U/ml, whereas, CA treatment showed 1.23 U/ml of Rubisco. It has been observed that the VW showed as a potential chelator as well as plant beneficial formulation for the enhanced phyto-remediation of Pb and Ni.

Efficacy of citric acid and sodium hypochlorite as disinfectants against Mycoplasma bovis

Mycoplasma bovis, a cattle pathogen of major economic importance across the globe, causes a range of diseases, including pneumonia and mastitis. Because of the limited options for effective treatment of these diseases, prevention and control are preferred to diagnosis and treatment. In this study, the efficacies of citric acid and sodium hypochlorite as disinfectants against M. bovis were tested using a modification of a standardised method for assessing the efficacy of disinfectants against bacteria. A citric acid concentration of 0.5 % was found to be an effective disinfectant, reducing infectivity by close to 10⁶ fold, while sodium hypochlorite at 1% was found to have similar efficacy to 0.5 % citric acid. A 0.04 % concentration of sodium hypochlorite was effective against M. bovis only in the absence of any organic material. Under these conditions, 0.25 % citric acid found to have similar efficacy. These findings indicate that 0.5 % citric acid or 1 % sodium hypochlorite are likely to be effective disinfectants for M. bovis under field conditions and 0.04 % sodium hypochlorite or 0.25 % citric acid are likely to be effective following removal of organic material.

In silico evolution of Aspergillus niger organic acid production suggests strategies for switching acid output

BACKGROUND

The fungus Aspergillus niger is an important industrial organism for citric acid fermentation; one of the most efficient biotechnological processes. Previously we introduced a dynamic model that captures this process in the industrially relevant batch fermentation setting, providing a more accurate predictive platform to guide targeted engineering. In this article we exploit this dynamic modelling framework, coupled with a robust genetic algorithm for the in silico evolution of A. niger organic acid production, to provide solutions to complex evolutionary goals involving a multiplicity of targets and beyond the reach of simple Boolean gene deletions. We base this work on the latest metabolic models of the parent citric acid producing strain ATCC1015 dedicated to organic acid production with the required exhaustive genomic coverage needed to perform exploratory in silico evolution.

RESULTS

With the use of our informed evolutionary framework, we demonstrate targeted changes that induce a complete switch of acid output from citric to numerous different commercially valuable target organic acids including succinic acid. We highlight the key changes in flux patterns that occur in each case, suggesting potentially valuable targets for engineering. We also show that optimum acid productivity is achieved through a balance of organic acid and biomass production, requiring finely tuned flux constraints that give a growth rate optimal for productivity.

CONCLUSIONS

This study shows how a genome-scale metabolic model can be integrated with dynamic modelling and metaheuristic algorithms to provide solutions to complex metabolic engineering goals of industrial importance. This framework for in silico guided engineering, based on the dynamic batch growth relevant to industrial processes, offers considerable potential for future endeavours focused on the engineering of organisms to produce valuable products.

Preparation of bio-eco based cellulose nanomaterials from used disposal paper cups through citric acid hydrolysis

The Used Disposal Paper Cups (UDPCs) have become a concern to the solid waste management sector as scientists triggered the problems in recent years, to proceed forward in developing the process for this issue. Based on this concern, the present study emphasizes on the isolation of a novel bio-eco based Cellulose NanoCrystals (CNCs) from UDPCs through citric acid hydrolysis. The effect of acid concentration on microstructure and yield of CNCs are highlighted. The optimized yield (55 wt.%) has an appearance of rod-like structure with a width of 13.7 ± 0.6 nm which results due to 76 wt.% of acid hydrolyzed CNCs. The colloidal stability, crystallinity index, presence of functional groups and elemental composition in CNCs (76 wt.%) were identified by employing zeta potential, XRD, conductometric test and FTIR techniques. Finally, the thermal stability of CNCs (76 wt.%) was investigated by thermo-gravimetric analysis.

Polycaprolactone microcapsules containing citric acid and naringin for plant growth and sustainable agriculture: physico-chemical properties and release behavior

Plant growth promoting rhizobacteria (PGPR) is an alternative to chemical fertilizers for sustainable, environment friendly agriculture. There is a need to develop strategies to potentiate the interaction between rhizobacteria and plants. Flavonoids and organic acids (components of root exudates) play specific beneficial roles as carbon sources and signal molecules in the plant - rhizobacteria interactions. The goal of this work is to encapsulate signal molecules, namely citric acid and naringin, an organic acid and a flavonoid, respectively, by a biodegradable polymer, polycaprolactone (PCL), in order to maintain the stability and activity of those signal molecules and enable their slow or controlled release over a selected period of time, according to the needs of the plants. This approach is expected to potentiate food crops, namely peanut crop, in adverse environmental conditions (water deficit), by promoting the beneficial interaction between the peanut plant (A. hypogaea) and rhizobacteria. The microcapsules (MCs) are obtained by an emulsion process combined with solvent evaporation technique and are characterized by scanning electron microscopy, thermogravimetry and Fourier transformed infrared spectroscopy. The kinetics of in vitro release of encapsulated molecules, in a period where the uptake of the compound in plants can occur, is studied. The encapsulation synthesis parameters that lead to the best encapsulation process yield and efficiency, as well as to the best final performance in terms of release, are identified. The effect of pH and molecular weight of PCL is found to mediate the release properties of the molecules for different types of soil. PCL 45000 Mw dissolved at 16% in dichloromethane leads to an encapsulation efficiency of 75% and the resulting MCs containing naringin exhibit a slow release profile for 30 days, unmodified by pH, enabling their use in soils of different characteristics. This research makes possible the manufacturing of smart materials for sustainable agriculture practices.

Efficacy of Zea mays L. for the management of marble effluent contaminated soil under citric acid amendment; morpho-physiological and biochemical response

The adverse industrial activities discharged contaminated wastewater directly into the water bodies that contain toxic substances such as heavy metals. The contours use of marble industrial effluents may affect the fertility of soil and crop growth. The present study was conducted to investigate the toxic effects of marble industrial effluents (M.E) on Zea mays L under the exogenous application of citric acid (CA) with different combinations such as marble industrial effluent (0, 30%, 60%, 100%) diluted with distilled water and CA (10 mM). The results showed significant decrease in the growth of Zea mays with increasing concentration of marble industrial effluent. The maximum reduction in plant height, root length, number of leaves, leaf area and fresh and dry biomass was observed at the application of 100% M.E as compared to control. Similar to growth conditions the photosynthetic machinery and the activities of antioxidant enzymes (Superoxide dismutase (SOD), Peroxidases (POD), Catalases (CAT), Ascorbate peroxidase (APX)) was also decreased with increasing concentration of M.E. The application of CA significantly alleviated the M.E induced toxic effect on Zea mays and ameliorated the growth, biomass, photosynthesis and antioxidant enzymes activities by reducing the production of reactive oxygen species. The C.A application also enhanced the heavy metal content such as chromium (Cr), cadmium (Cd), Zinc (Zn) in different parts of Zea mays. The results concluded that the Zea mays tolerant varieties can be a potential candidate for the M.E irrigated soil and might be suitable for the phyto-extraction of Cr, Cd and Zn.

Direct measurement of aerosol pH in individual malonic acid and citric acid droplets under different relative humidity conditions via Raman spectroscopy

Acidity of aerosol particles plays important roles in atmospheric chemistry, in turn, impacting climate system and public health. Current knowledge of acidity in atmosphere aerosols remains fairly scarce largely because of difficulty in direct measurement. On the other hand, indirect methods for estimating aerosol pH are often inconsistent with pH values predicted by thermodynamic models. Recently, a direct Raman spectroscopy method has been reported to determine pH values of acid-conjugate base equilibria systems based on Raman intensity of distinct characteristic peaks of conjugate acid-base pair. Nevertheless, for pure carboxylic acid aerosol particles, such as malonic acid (MA), characteristic peak of its conjugate base cannot be clearly observed in Raman spectra owing to small K_a value (weak acid dissociation constant), which leads to little dissociation of weak acid and low concentration of its conjugated base. As a result, pH of carboxylic acid particles cannot be directly determined by calibrating concentrations of acid and its conjugated base using the above-mentioned method. To address such an issue, we demonstrate a new approach for determining pH values of malonic acid (MA) and citric acid (CA) droplets under different relative humidity (RH) based on calibration curves. We measure Raman intensity ratios of acid solutions at different concentrations and their pH values to establish a calibration curve, and then using the intensity ratio of MA and CA droplets under different RH to determine aerosol particle pH based on calibration curves. Results have shown that aerosol pH of MA droplet decreases with a decreasing RH and pH values ranges from 1.03 to -0.12, when RH value is reduced from 90% to 26%, in good agreement with model prediction values. In addition, we also, for the first time, report pH values of CA droplets under different RH conditions and its pH values range from 1.13 to -0.74 when RH is reduced from 91% to 28%.

Citric acid enhances Ce uptake and accumulation in rice seedlings exposed to CeO2 nanoparticles and iron plaque attenuates the enhancement

To assess the role of citric acid, as a typical low-molecular-weight organic acid from root exudates, on cerium (Ce) uptake, accumulation and translocation in rice seedlings (Oryza sativa L.) exposed to two CeO₂ nanoparticles (NPs) (14 nm and 25 nm). A hydroponic experiment was performed under two citric acid levels (0.01 and 0.04 mmol L^-1) combined with iron plaque presence. Citric acid significantly enhanced surface-Ce, root-Ce and shoot-Ce accumulation, irrespective of NPs size and iron plaque presence. The increased surface-Ce was associated with the promoted interactive attraction between NPs and root surface, and the enhanced NPs dissolution. Surface-Ce (containing crystalline and amorphous fractions of iron plaque) accumulation increased with the increase of citric acid concentrations. However, the enhancement influence of 0.01 mmol L^-1 citric acid on root-Ce, shoot-Ce accumulations, rice-Ce distribution and TF_root-shoot was more remarkable than citric acid (0.04 mmol L^-1), which suggested higher food security risk for human health with environment-level citric acid. Iron plaque presence attenuated the enhancement effect of citric acid on rice-Ce accumulation and distribution (containing surface-Ce, root-Ce and shoot-Ce) due to the reduced attractive interaction between NPs and root surface from the effect of Fe²⁺ being dissolved by iron plaque. Above effect of citric acid and iron plaque was more remarkable in 25 nm NP than 14 nm NP.

The effects of external Mn2+ concentration on hyphal morphology and citric acid production are mediated primarily by the NRAMP-family transporter DmtA in Aspergillus niger

Background

Citric acid, a commodity product of industrial biotechnology, is produced by fermentation of the filamentous fungus Aspergillus niger. A requirement for high-yield citric acid production is keeping the concentration of Mn²⁺ ions in the medium at or below 5 µg L⁻¹. Understanding manganese metabolism in A. niger is therefore of critical importance to citric acid production. To this end, we investigated transport of Mn²⁺ ions in A. niger NRRL2270.

Results

we identified an A. niger gene (dmtA; NRRL3_07789), predicted to encode a transmembrane protein, with high sequence identity to the yeast manganese transporters Smf1p and Smf2p. Deletion of dmtA in A. niger eliminated the intake of Mn²⁺ at low (5 µg L⁻¹) external Mn²⁺ concentration, and reduced the intake of Mn²⁺ at high (> 100 µg L⁻¹) external Mn²⁺ concentration. Compared to the parent strain, overexpression of dmtA increased Mn²⁺ intake at both low and high external Mn²⁺ concentrations. Cultivation of the parent strain under Mn²⁺ ions limitation conditions (5 µg L⁻¹) reduced germination and led to the formation of stubby, swollen hyphae that formed compact pellets. Deletion of dmtA caused defects in germination and hyphal morphology even in the presence of 100 µg L⁻¹ Mn²⁺, while overexpression of dmtA led to enhanced germination and normal hyphal morphology at limiting Mn²⁺ concentration. Growth of both the parent and the deletion strains under citric acid producing conditions resulted in molar yields (Y_p/s) of citric acid of > 0.8, although the deletion strain produced ~ 30% less biomass. This yield was reduced only by 20% in the presence of 100 µg L⁻¹ Mn²⁺, whereas production by the parent strain was reduced by 60%. The Y_p/s of the overexpressing strain was 17% of that of the parent strain, irrespective of the concentrations of external Mn²⁺.

Conclusions

Our results demonstrate that dmtA is physiologically important in the transport of Mn²⁺ ions in A. niger, and manipulation of its expression modulates citric acid overflow.

Synthesis, characterization and application of crosslinked alginate as green packaging material

Plastic films for food wrapping, packing are widely used due to their special properties. These fossil fuel derived films are associated with long degradation time, toxicity and environmental pollution. Pineapple waste, sea weed can be very good renewable, alternative carbon sources to produce edible films. These edible films can be consumed by lower animals thereby overcoming the disposal problems of accumulating waste plastic and hence reducing pollution. In the present study, crosslinked polymers are prepared from pectin (P)/sodium alginate (SA) through crosslinking with bio-based acids such as citric acid (CA) and tartaric acid (TA). Pectin was extracted from waste pineapple shell and sodium alginate extracted from seaweed. The crosslinked films were characterized by using various analytical techniques such as FT-IR, thermogravimetry, and scanning electron microscopy (SEM). Mice feed study (testing of edibility), plant growth substrate and vermicomposting of these films was studied. Finally a suitable application of these newly prepared polymeric films has been evaluated as wrapping material on food products such as chocolate and Indian vegetable puff to enhance the shelf life of food.

Effects of root exudates on the activation and remediation of cadmium ion in contaminated soils

To screen out plants with hyperaccumulation of heavy metals and explore the effects of root exudates on the phytoremediation in contaminated soils. The germination rates of five plants including Lolium perenne L. (L. perenne), Sorghum sudanense (Piper) Stapf. (S. sudanense), Pennisetum alopecuroides (L.) Spreng. (P. alopecuroides), Medicago sativa L. (M. sativa), and Trifolium repens L. (T. repens) in different concentrations of cadmium ion solution (0-100 mg/kg) were determined. The growth adaptability of these five plants under conditions of contaminated soils with the above cadmium ion concentrations was also evaluated. S. sudanense and P. alopecuroides had higher germination rates and better growth than the three other plants and were selected as the latter experimental varieties. The activation amounts of cadmium ion in soils were measured using AAS in the presence of three types of root secretions (citric acid, glycine, and maltose) with different concentrations (10-500 mmol/L). The activation amounts decrease in the following order: citric acid > glycine > maltose. The effect of these three root exudates on the removal of cadmium-contaminated soils in combination with S. sudanense and P. alopecuroides was also tested. For S. sudanense and P. alopecuroides, the maximum biomass and removal rate reaches the maximum at 100 mmol/L of citric acid. Conversely, low concentrations (approximately 10-50 mmol/L) of glycine and maltose are more effective for plant growth and phytoremediation. The addition of citric acid at 100 mmol/L and approximately 10-50 mmol/L of glycine and maltose can effectively promote the transfer of cadmium ion from roots to leaves and the accumulation of cadmium ion in leaves.

Change of erosive potential of apple and orange juice at different dilutions

The aim of this in vitro study was to investigate the change of erosive properties of apple and orange juice after dilution with tap water. Apple juice, orange juice and citric acid were assessed for pH and titratable acidity at different aqueous dilutions (100% – pure liquid, 60% – 3 : 2 mixing ratio, and 40% – 2 : 3 mixing ratio respectively). Thus, 72 bovine enamel specimens were distributed to 9 groups (n = 8 specimens per group), followed by 25 minutes of erosion by superfusion with the described test liquids according to group allocation. Erosive substance loss (µm) was determined profilometrically. The different substance losses within a dilution series were tested using the Wilcoxon rank sum test. The significance level was set to p ≤ 0.05. Erosive substance loss [µm] for 100% concentrations (median ± interquartile range) was highest for apple juice (5.7 ± 0.8), followed by citric acid (4.6 ± 0.4) and orange juice (1.5 ± 0.5). The dilution of apple juice (60%: 4.2 ± 0.7; 40%: 3.1 ± 0.5) and citric acid (60%: 3.7 ± 0.9; 40%: 2.8 ± 0.7) with tap water lead to a significant (p < 0.05) reduction of erosive potential in comparison to 100% concentrations. This effect was not consistent for orange juice, where significantly more substance loss was found for pure juice (100%) than for 60% diluted juice (60%: 1.1 ± 0.3, p < 0.05), but no significant difference was found between 100% and 40% (40%: 0.9 ± 0.6, p > 0.05), and 60% and 40%, respectively. In conclusion, dilution of apple juice with tap water led to a significant reduction of its erosive potential. For orange juice, the effect of dilution on the erosive substance loss was only limited.

Citric acid and glycine reduce the uptake and accumulation of Fe2O3 nanoparticles and oxytetracycline in rice seedlings upon individual and combined exposure

Uptake of nanoparticles and antibiotics by plants is root exudates-dependent, however, the underlying influence processes and mechanisms from different root exudates are rarely investigated. A hydroponic experiment was conducted to investigate the accumulation of Fe₂O₃ nanoparticle (NP) and oxytetracycline (OTC) in rice seedlings, in the absence or presence of citric acid or glycine, acting as components of root exudates. Irrespective of individual or combined exposure of Fe₂O₃ NP and OTC, citric acid and glycine both reduced surface-Fe, surface-OTC, root-OTC, shoot-OTC accumulations with dose-effect relationship. Two exudates increased |ζ| values of NP, which weakened the interactive attraction between NP and root surface and then decreased surface-Fe accumulation. Citric acid and glycine binding with OTC in solution decreased surface-OTC accumulation, and further decreased root-OTC and shoot-OTC accumulations. Combined exposure of two pollutants alleviated the reduction effect of citric acid and glycine on surface-Fe/surface-OTC/root-OTC accumulations due to their high accumulations in combined exposure compared to individual exposure. Although citric acid and glycine promoted TF_root-shoot and TF_surface-root of two pollutants, respectively, they always decreased total rice-Fe and rice-OTC accumulations. Therefore, the presence of root exudates decreased the bioaccumulation of Fe₂O₃ NP and OTC in rice upon their individual and combined exposure through changing their environmental behaviors in rhizosphere.

Formula optimization for melanosis-inhibitors of Pacific white shrimp (Litopenaeus vannamei) by response surface methodology

Melanosis is major problem of crustaceans during their rigor mortis storage. This study for the first time was designed to optimize the formula of preservatives to maintain the color feature of Pacific white shrimp using response surface methodology. A three-factors-three-levels Box-Behnken design was applied to evaluate the effect of chitosan, citric acid and l-cysteine on color features (L*, a*, b* and ΔE) of Pacific white shrimp. It was found that the increasing rate of ΔE was retarded by the higher concentrations of chitosan, citric acid and l-cysteine in a certain range. The optimal formula for inhibiting the increase of ΔE was 1.36% chitosan, 0.47% citric acid and 0.31% l-cysteine. Under the optimal pretreated conditions, the predicted ΔE of shrimp after 8 days of storage was 14.59, close to the measured values (14.49). These results indicated that the optimal combined preservatives could retard the decrease of lightness and the aggregation of ΔE and melanosis effectively, and might be a potential application for retarding melanosis and extending shelf life of Pacific white shrimp.

Polyploidy remodels fruit metabolism by modifying carbon source utilization and metabolic flux in Ponkan mandarin (Citrus reticulata Blanco)

The phenotypic variations that follow polyploidization are expected to improve agricultural productivity and efficiency [1]. However, the effect of polyploidization on plant metabolism has rarely been studied. This study evaluated the metabolic alterations that followed autotetraploidization in the fruit of Ponkan mandarin (C. reticulata Blanco) for three consecutive years and explored the underlying changes to the transcriptome. The autotetraploid (4x) Ponkan fruit had higher levels of total acids, ascorbic acid and total phenolic compounds than the diploid (2x). The primary metabolites especially the organic acids tended to accumulate at higher levels in the 4x fruit. Conversely, two major groups of secondary metabolites (i.e. flavonoids and carotenoids) tended to accumulate at lower levels. The expression levels of citric acid biosynthesis-related genes were unaltered in 4x fruit compared to the 2x fruit. Additionally, genes associated with the transport and utilization of citric acid were significantly down-regulated during ripening, which might induce increases in the levels of citric acid in the 4x fruit. Lower levels of flavonoids and carotenoids in the 4x fruit are potentially associated with decreases in the transport and utilization of citric acid, which is an important metabolite. Citric acid contributes to respiration by serving as an intermediated in the tricarboxylic acid cycle (TCA) and also provides carbon for the production of secondary metabolites. This study demonstrates that polyploidization can influence metabolism in plants.

Protective role of citric acid against oxidative stress induced by heavy metals in Caenorhabditis elegans

The adverse effects of heavy metals, such as cadmium, zinc, and copper, occur due to the generation of reactive oxygen species (ROS). The use of Caenorhabditis elegans for the purposes of conservation and biomonitoring is of great interest. In the present study, ROS, malondialdehyde (MDA), and citric acid levels and superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in a model organism were tested to study toxicity. C. elegans was exposed to three different concentrations of cadmium (CdCl₂, 5, 10, 50 μM), zinc (ZnSO₄, 10, 100, 500 μM), and copper (CuSO₄, 10, 100, 500 μM) for 3 days. ROS levels increased by 1.3- to 2.1-fold with increasing metal concentrations. The MDA content increased by approximately 7-, 5-, 2-fold after exposure to high concentrations of cadmium, zinc, and copper, respectively. Furthermore, the citric acid content increased by approximately 3-fold in the cadmium (Cd, 5 μM), zinc (Zn, 10 μM), and copper (Cu, 100 μM) treatment groups compared to that in untreated C. elegans. Therefore, citric acid may play an important role in heavy metal detoxification. Excess citric acid also slightly increased the LC₅₀ by 1.3- to 2.0-fold, basic movements by 1.0- to 1.5-fold, decreased the ROS content by 2.4- to 2.1-fold, the MDA content by 4- to 2-fold, the SOD activity by 9- to 3-fold, the GPx activity by 4.0- to 3.0-fold, and the mRNA expression levels of GPxs by 3.2- to 1.8-fold after metals treatment. And it is most significantly in the alleviation of citric acid to cadmium. This study not only provides information to further understand the effects of heavy metal exposure on ROS, MDA, GPx, SOD, and citric acid in worms but also indicates that supplemental citric acid can protect animals from heavy metal stress and has broad application prospects in decreasing oxidative damage caused by heavy metals.

The determination of the optimum conditions upon the leaching performance of calcined magnesite

The aim of the study is to examine the reaction of calcined magnesite in the citric acid media, and after that it is determination of optimal conditions about the leaching performance of calcined magnesite by an experimental plan of Taguchi Statistical Method with L₁₆ (4⁵). The parameters such as particle size, reaction temperature, acid concentration, solid-liquid ratio and reaction period are tested. In this work, the optimal combination of the parameters that achieves robustness against noise factors is found as: 50 °C, 45 min, -319 μm, 0.125 g/mL, and 2M, respectively. Extraction efficiency of the magnesium from calcined magnesite is 98.86 %.

Cellulose modified by citric acid reinforced polypropylene resin as fillers

The greatest challenge hindering the use of cellulose as a reinforcing filler in polymeric composites is its poor compatibility due to the inherent hydrophilicity of cellulose and the hydrophobic nature of polymeric matrices. To solve this issue, we demonstrate an effective water-based method to render the cellulose surface with high carboxyl content through the esterification of hydroxyl groups with citric acid in a solid phase reaction without the use of noxious solvents. The modified cellulose was then further hydrophobized by grafting magnesium stearate to the surface. Consequently, the flexural properties of PP composites reinforced by the hydrophobized cellulose fillers were greatly improved compared to those of composites containing hydrophilic cellulose and pure PP resin. The surface modification conditions and filler proportions in composites were optimized. Because of the innocuity and cost-efficiency of citric acid, we believe that citric acid-modified cellulose has immense potential as a sustainable and cost-effective reinforcing filler.

Injecting-related health harms and overuse of acidifiers among people who inject heroin and crack cocaine in London: a mixed-methods study

Background

Venous access is a priority for people who inject drugs (PWID). Damage and scarring of peripheral veins can exacerbate health harms, such as skin and soft tissue infections (SSTI), and promote transitions to femoral and subcutaneous injecting. Brown heroin available in Europe requires acidification for injection preparation. In this paper, we present mixed-methods data to explore our hypothesis of a link between overly acidic injection solutions, venous damage and SSTI risk.

Methods

We present a structured survey (n = 455) and in-depth qualitative interview (n = 31) data generated with PWID in London for the Care & Prevent study. Participants provided life history data and detail on injecting environments and drug preparation practices, including the use of acidifiers. Bivariate and multivariate analyses were conducted using a logistic regression for binary outcomes to explore associations between outcomes and excessive acidifier use. Grounded theory principles informed inductive qualitative analysis. Mixed-methods triangulation was iterative with results comparison informing the direction and questions asked of further analyses.

Results

Of the 455 participants, most (92%) injected heroin and/or crack cocaine, with 84% using citric as their primary acid for drug preparation. Overuse of acidifier was common: of the 418 who provided an estimate, 36% (n = 150) used more than ½ a sachet, with 30% (n = 127) using a whole sachet or more. We found associations between acidifier overuse, femoral injecting and DVT, but not SSTI. Qualitative accounts highlight the role of poor heroin quality, crack cocaine use, information and manufacturing constraints in acidifier overuse. Painful injections and damage to peripheral veins were common and often attributed to the use of citric acid.

Conclusions

To reduce injecting-related injury and associated consequences, it is crucial to understand the interplay of environmental and practice-based risks underpinning venous damage among PWID. Overuse of acidifier is a modifiable risk factor. In the absence of structural supports such as safe injecting facilities or the prescribing of pharmaceutical diamorphine, there is an urgent need to revisit injecting paraphernalia design and distribution in order to alleviate health harms and distress among the most marginalised.

Functional exploration of co-expression networks identifies a nexus for modulating protein and citric acid titres in Aspergillus niger submerged culture

Background

Filamentous fungal cell factories are used to produce numerous proteins, enzymes, and organic acids. Protein secretion and filamentous growth are tightly coupled at the hyphal tip. Additionally, both these processes require ATP and amino acid precursors derived from the citric acid cycle. Despite this interconnection of organic acid production and protein secretion/filamentous growth, few studies in fungi have identified genes which may concomitantly impact all three processes.

Results

We applied a novel screen of a global co-expression network in the cell factory Aspergillus niger to identify candidate genes which may concomitantly impact macromorphology, and protein/organic acid fermentation. This identified genes predicted to encode the Golgi localized ArfA GTPase activating protein (GAP, AgeB), and ArfA guanine nucleotide exchange factors (GEFs SecG and GeaB) to be co-expressed with citric acid cycle genes. Consequently, we used CRISPR-based genome editing to place the titratable Tet-on expression system upstream of ageB, secG, and geaB in A. niger. Functional analysis revealed that ageB and geaB are essential whereas secG was dispensable for early filamentous growth. Next, gene expression was titrated during submerged cultivations under conditions for either protein or organic acid production. ArfA regulators played varied and culture-dependent roles on pellet formation. Notably, ageB or geaB expression levels had major impacts on protein secretion, whereas secG was dispensable. In contrast, reduced expression of each predicted ArfA regulator resulted in an absence of citric acid in growth media. Finally, titrated expression of either GEFs resulted in an increase in oxaloacetic acid concentrations in supernatants.

Conclusion

Our data suggest that the Golgi may play an underappreciated role in modulating organic acid titres during industrial applications, and that this is SecG, GeaB and AgeB dependent in A. niger. These data may lead to novel avenues for strain optimization in filamentous fungi for improved protein and organic acid titres.

New type of green extractant for oil production: Citric acid/citric acid sodium extraction system

Developing green solvents with low toxicity and low energy consumption is an important issue for edible oil production. In this study, a novel extraction system, specifically a citric acid/citric acid sodium mixture, was developed for oil extraction from seed crops. Peanut and pumpkin seeds were used to evaluate extraction efficiency and more than 70% and 57% oils, respectively, were extracted from peanut and pumpkin seeds at 4 °C. After extraction, the oils floated on the surface of the solution and could be separated from the solvent system without evaporation. The extraction of edible oils was achieved without the use of toxic chemicals or energy-intensive equipment. This study provided a green and efficient method, and showed the potential of the proposed citric acid/citric acid sodium extraction system for production of edible oils from natural sources.

Disruption of a putative mitochondrial oxaloacetate shuttle protein in Aspergillus carbonarius results in secretion of malic acid at the expense of citric acid production

BACKGROUND

In filamentous fungi, transport of organic acids across the mitochondrial membrane is facilitated by active transport via shuttle proteins. These transporters may transfer different organic acids across the membrane while taking others the opposite direction. In Aspergillus niger, accumulation of malate in the cytosol can trigger production of citric acid via the exchange of malate and citrate across the mitochondrial membrane. Several mitochondrial organic acid transporters were recently studied in A. niger showing their effects on organic acid production.

RESULTS

In this work, we studied another citric acid producing fungus, Aspergillus carbonarius, and identified by genome-mining a putative mitochondrial transporter MtpA, which was not previously studied, that might be involved in production of citric acid. This gene named mtpA encoding a putative oxaloacetate transport protein was expressed constitutively in A. carbonarius based on transcription analysis. To study its role in organic acid production, we disrupted the gene and analyzed its effects on production of citric acid and other organic acids, such as malic acid. In total, 6 transformants with gene mtpA disrupted were obtained and they showed secretion of malic acid at the expense of citric acid production.

CONCLUSION

A putative oxaloacetate transporter gene which is potentially involved in organic acid production by A. carbonarius was identified and further investigated on its effects on production of citric acid and malic acid. The mtpA knockout strains obtained produced less citric acid and more malic acid than the wild type, in agreement with our original hypothesis. More extensive studies should be conducted in order to further reveal the mechanism of organic acid transport as mediated by the MtpA transporter.

Moth bean starch (Vigna aconitifolia): isolation, characterization, and development of edible/biodegradable films

In the current work, moth bean starch was separated from the moth bean seeds which were cultivated in the semi arid regions of Haryana and Rajasthan, India using alkali treatment technique and characterized. Isolated and purified moth bean starch comprised (12.89-20.37%) amylose, 0.8% protein, 0.4% ash, swelling index and solubility were 10.8-14.7% and 6.4-9.8% respectively. For wrapping application, starch was modified using citric acid as cross linking agent (1-7% w/w of total starch) and film was made using casting method, and investigated the influence of citric acid on the functional properties of the films such as moisture content, solubility, swelling index, water vapor permeability and mechanical property. Significant difference in the functional properties among native and modified moth bean starch films was noticed. Interactions among starch chains due to cross linking in the modified starch films were reported using FTIR spectra. Surface micrographs of both purfied starch granules and films were studied using scanning electron microscopy. From the outcomes, it was exhibited that obtained starch granules has range large to small size with distorted cylinder and oval shapes. While cross linked starch films showed compact, slightly rough and homogeneous surface. Tested modified moth bean starch films containing citric acid (CA) and sorbitol were utilized as wrapping films to improve the shelf life of fresh lemon. Outcomes showed that the film contains 5% CA could be most promising wrapping materials for lemon that enhanced the shelf life of lemon additionally up to 12 days.

[Effects of citric acid on patients with severe burn complicated with acute renal injury treated by continuous renal replacement therapy]

Objective: To explore the effects of citric acid on patients with severe burn complicated with acute renal injury treated by continuous renal replacement therapy (CRRT). Methods: Medical records of 83 patients with large area of burn complicated with acute renal injury admitted to intensive care unit (ICU) of our department from January 2015 to December 2018 and meeting the inclusion criteria were analyzed retrospectively. The patients were divided into heparin group [n=43, 25 males and 18 females, aged (35.0±2.5) years] and citric acid group [n=40, 22 males and 18 females, aged (37.0±6.6) years] according to different anticoagulation methods. After admission, routine support treatment and CRRT were performed after being diagnosed with acute renal injury in patients in 2 groups. Patients in heparin group were treated with low molecular weight heparin for anticoagulation with first dosage of 20 U/kg and an increase of 2.5 to 5.0 U per hour, and patients in citric acid group were given citric acid of 0.02 g/mL with dosage of 150~200 mL/h for anticoagulation. The use time of blood filter, recovery time of urine volume, and time of staying in ICU, and platelet count, activated partial thromboplastin time (APTT), prothrombin time (PT), and serum creatinine, urea nitrogen, cystatin C, procalcitonin, C-reactive protein, and neutrophil, leukocyte count, blood sugar, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and heart rate, body temperature, and mean arterial pressure before treatment and post treatment hour (PTH) 24 were recorded. Besides, occurrence of hemorrhage, hypocalcemia, metabolic acidosis, metabolic alkalosis, and death within 28 days post injury were recorded. Data were processed with t test and chi-square test. Results: The use time of blood filter of patients in citric acid group was (28.7±3.2)h, significantly longer than (19.4±2.6) h in heparin group (t=14.139, P<0.01). The recovery time of urine volume and time of staying in ICU of patients in citric acid group were respectively (7.6±0.9) and (9.6±1.3) d, significantly shorter than (9.2±1.5) and (11.2±1.8) d in heparin group (t=5.516, 4.697, P<0.01). Before treatment, there were no statistically significant differences in platelet count, APTT, and PT of patients in 2 groups (t=1.235, 0.515, 1.279, P>0.05). At PTH 24, the platelet count of patients in citric acid group was significantly higher than that in heparin group (t=10.947, P<0.01), and APTT and PT of patients in citric acid group were significantly shorter than those in heparin group (t=7.069, 9.142, P<0.01). Before treatment, there were no statistically significant differences in serum creatinine, urea nitrogen, and cystatin C of patients in 2 groups (t=1.684, 1.878, 1.472, P>0.05). At PTH 24, the serum creatinine, urea nitrogen, and cystatin C of patients in citric acid group were significantly lower than those in heparin group (t=7.778, 9.776, 5.117, P<0.01). Before treatment, there were no statistically significant differences in serum procalcitonin and C-reactive protein of patients in 2 groups (t=1.413, 0.898, P>0.05). At PTH 24, the serum procalcitonin and C-reactive protein of patients in citric acid group were significantly lower than those in heparin group (t=2.635, 2.297, P<0.05). Before treatment, there were no statistically significant differences in neutrophil, leukocyte count, blood sugar, AST, and ALT of patients in 2 groups (t=0.555, 0.816, 0.470, 1.896, 0.982, P>0.05). At PTH 24, the neutrophil, leukocyte count, blood sugar, AST, and ALT of patients in citric acid group were significantly lower than those in heparin group (t=2.054, 3.314, 7.185, 2.151, 3.013, P<0.05 or P<0.01). Before treatment, there were no statistically significant differences in heart rate, body temperature, and mean arterial pressure of patients in 2 groups (t=1.406, 0.474, 0.720, P>0.05). At PTH 24, the heart rate, body temperature, and mean arterial pressure of patients in citric acid group were significantly lower than those in heparin group (t=2.307, 4.498, 2.056, P<0.05 or P<0.01). The incidence of hemorrhage of patients in citric acid group while in hospital was significantly lower than that in heparin group (χ(2)=4.949, P<0.05). There were no statistically significant differences in incidence of hypocalcemia, metabolic acidosis, metabolic alkalosis, and death rate within 28 days post injury of patients in 2 groups while in hospital (χ(2)=3.346, 0.884, 0.297, 0.324, P>0.05). Conclusions: Citric acid has significant anticoagulant effect on patients with large area of burn complicated with acute renal injury treated by CRRT, which can prolong the use time of the blood filter, shorten the recovery time of urine volume and time of staying in ICU, improve renal function indexes, blood biochemical indexes, and inflammation indexes, maintain the stability of internal environment, and reduce the risk of hemorrhage.

Influence of lactic, citric and phosphoric acids on the properties of concentrated lactose solutions

Physicochemical and thermal characteristics of concentrated lactose solutions containing 0.05, 1, or 4% (w/w) of three acids commonly used in the food industry, i.e., lactic, citric, and phosphoric acid, were studied. Properties of both lactose and water were affected by all acids studied. Thermographic analysis showed that interactions between water and acids hindered evaporation of water from most of lactose solutions. This effect was mostly related to the formation of a strong hydration layer around lactose molecules by hydrogen bonds. Acid-induced hydrolysis of lactose into glucose and galactose varied depending on the concentration, hydrolytic power of acids and molecular interactions in the system. The study concluded that the varying physical, chemical, structural and thermal characteristics of lactose as affected by the presence of different acids was mainly due to the manipulation of water-lactose interactions, whereas the hydrolysis of lactose by the acids plays a smaller role.

Comparison of mannitol and citric acid cough provocation tests

RATIONALE

Citric acid has been used as a cough provocation test for decades. However, the methods of administration have not been standardized. Inhaled mannitol is a novel cough provocation test, which has regulatory approval and can be performed utilizing a simple disposable inhaler in a standardized manner.

OBJECTIVE

To compare the mannitol and citric acid cough provocation tests with respect to their ability to identify subjects with chronic cough and their tolerability.

METHODS

Subjects with chronic cough (n = 36) and controls (n = 25) performed provocation tests with mannitol and citric acid. Both tests were video recorded. Cough sensitivity was expressed as coughs-to-dose ratios (CDR) and the cumulative doses to mannitol or concentration to citric acid evoking 5 coughs (C5). Forced expiratory volume in 1 s (FEV₁), visual analogue scales (VAS), test completion rates and the total cough frequencies were analysed.

RESULTS

Mannitol and citric acid CDR both effectively separated those with cough and the control subjects (AUC 0.847 and 0.803, respectively) as did C5 (AUC 0.823 and 0.763, respectively). There was a good correlation between the cough sensitivity provoked by the two stimuli, either expressed as CDR (r = 0.65, p < 0.001) or C5 (r = 0.53, p = 0.001). Both tests were similarly tolerated in terms of VAS, although more patients discontinued the mannitol test early, primarily due to cough.

CONCLUSIONS

Mannitol and citric acid tests correlated well, equally identified subjects with chronic cough and their tolerability was similar. The feasibility issues, strict standardisation and regulatory approval may favour mannitol to be used in clinical cough research.

Esterification of citric acid with locust bean gum

Esterification of citric acid (CA) with locust bean gum (LBG) was prepared by hydrochloric acid (HCl) as a catalyst and UV irradiation (254 nm) as esterification energy. This study aims to determine the best conditions of esterification. Other than that, it is to know the effect of amount HCl and UV irradiation time for the esterification process of CA with LBG. The amounts of HCl are 0.18 and 0.30 M, while the variations of UV irradiation time are 75 and 100 minutes. Polyester (CA-LBG) were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffractometer (XRD), esterification degree, and viscosity. Parameters for determining the best conditions for esterification are esterification degree and viscosity. The best conditions of esterification were obtained by using 0.30 M mL HCl and 100 minutes of UV irradiation time resulted in CA-LBG having a value of esterification degree 9.69 % and viscosity 7.46 cPs. HCl accelerates protonation on the O atoms and the formation of positive C atoms of carbonyl groups of citric acid. The time of UV irradiation gives the longer energy for the bond formation between the positive C atoms of the carbonyl group and the O atoms of the hydroxyl group at C-6 atoms of mannose and galactose.

Combined effects of textural and surface properties of modified ordered mesoporous carbon (OMC) on BTEX adsorption

In this study, we first investigated the effects of textural parameters and surface properties of ordered mesoporous carbon (OMC) for the adsorptive removal of Benzene, Toluene, Ethylbenzene, and Xylene (BTEX) from aqueous solutions. The BET surface area, pore volume, and surface functional groups of OMC played a crucial role in affecting the adsorption performance of BTEX. Boric acid was used to increase the pore size and BET surface area of OMC from 5.94 nm to 6.74 nm and from 1276 m²/g to 1428 m²/g, respectively. Citric acid was used to introduce more oxygen-containing functional groups on the surface of OMC achieving an overall increase of 11.4% of the oxygen content. The batch adsorption experiments were conducted to evaluate the adsorption capacity for OMC and modified towards BTEX and the results showed that modified OMC exhibited a significant improvement for BTEX removal in the following order: Xylenes > Ethylbenzene > Toluene > Benzene. The BTEX adsorption capacities were improved from 8% to 15% with the addition of boric acid compared to the virgin. Surface functionalized using citric acid exhibited the total adsorption capacity of 142 mg/g with an increment of 40.5% compared to virgin OMC.

Citric acid mitigates soybean meal induced inflammatory response and tight junction disruption by altering TLR signal transduction in the intestine of turbot, Scophthalmus maximus L

A 12-week feeding trial was conducted to investigate the effect of citric acid on the involvement of TLRs in the soybean meal induced inflammatory response and tight junction disruption in the distal intestine of juvenile turbot (Scophthalmus maximus L.). Four isonitrogenous and isolipidic practical diets were formulated: fish meal-based diet (FM); 40% fish meal protein in FM replaced with soybean meal protein (SBM); SBM + 1.5% citric acid and SBM + 3% citric acid. Compared to the FM, diet SBM significantly increased the gene expression of TLRs (TLR2, TLR3, TLR5b, TLR9, TLR21, TLR22) and MyD88, as well as TLR related molecules (NF-κB, IRF-3, p38 and JNK), which were remarkably reduced by dietary citric acid. Similarly, citric acid supplementation in SBM markedly depressed gene expression of pro-inflammatory cytokines (TNF-α and IFN-γ) and pore-forming tight junction protein Claudin-7, and enhanced gene expression of the anti-inflammatory cytokine TGF-β1 and TJ proteins related to the decrease in paracellular permeability (Claudin-3, Claudin-4, Occludin, Tricellulin and ZO-1). Compared to the SBM, the concentration of IgM and C4 in serum was significantly reduced by dietary citric acid. In brief, dietary citric acid could synchronously inhibit TLRs-dependent inflammatory response regulated by NF-κB and IRF3, as well as cause TLRs-dependent tight junction disruption modulated by p38 and JNK. Therefore, citric acid could function on mitigating soybean meal induced enteropathy in the distal intestine of juvenile turbot.