Improved Isolation of Microbiologically Produced (2R,3S)-Isocitric Acid by Adsorption on Activated Carbon and Recovery with Methanol

Tailored glutamine modified zinc-terephthalic acid/xanthan gum composite for improved removal of lead ions

Novel zinc-terephthalate/xanthan gum/glutamine (Zn-BDC/X/G) adsorbent was fabricated using ferric ions crosslinking gelation method for effective adsorption of Pb2+ from wastewater. The structure of Zn-BDC/X/G was confirmed using several characterization techniques. Zn-BDC/X/G reveals thermal permanence, advanced textural properties, pHPZC at pH 6.8, and 97 nm as TEM particle size. The maximum adsorption capacity of Zn-BDC/X/G was 271.40 mg/g at 25 °C, pH 5, equilibrium time within 60 min, and dosage 1.5 g/L as calculated from the nonlinear Langmuir model. Nonlinear kinetic and isothermal models have accurately described the adsorption process. The impact of ionic strength in Pb2+ adsorption onto Zn-BDC/X/G at pH 5 appears to be a decrease of removal % by 19 when compared with 1.5 mol/L of KCl. Thermodynamic analysis for Pb2+ adsorption onto Zn-BDC/X/G was endothermic, high randomness at solid-liquid boundary, and spontaneous physisorption process. The best eluent for removing Pb2+ from the surface of Zn-BDC/X/G is HNO3, which provides the highest desorption efficiency percent (99%). Zn-BDC/X/G composite could be reusable with a slight decrease in the removal efficiency by only 3% after eight application cycles. The above results show that Zn-BDC/X/G bio-nanocomposite is a promising, sustainable, and eco-friendly material.

Epichlorohydrin/triethylamine modified psyllium as a highly efficient adsorbent for selective adsorption of anionic dyes

To develop new green sustainable adsorbents, herein, psyllium, a polysaccharide, was transformed into a cationic material by introducing a quaternary ammonium group in its structure through a two-step process. Psyllium was epoxidized with epichlorohydrin to epoxy propyl form (EPsy) and the resulting material was reacted with triethylamine to obtain a quaternized psyllium, TPsy. TPsy demonstrates selective elimination of anionic dyes (CR and MO). The maximum % adsorption (Pr) of 93.94 %, and 94.44 % were reported for MO and CR (anionic dyes) respectively within 70 min. The strong adsorption of MO and CR can be attributed to electrostatic attraction and hydrogen bonding. The adsorption process adhered to the pseudo-second-order kinetics indicating chemisorption and Langmuir isotherm suggesting monolayer adsorption, exhibiting a maximum adsorption capacity (qm) of 223.71 mg/g for MO and 260.41 mg/g for CR. TPsy is regenerable even after twelve adsorption-desorption cycles with cumulative q of 903.97 mg/g and 932.83 mg/g for MO and CR respectively. Our study introduces a novel approach by reversing the surface charge of psyllium (anionic, PZC = 2.25) through quaternization to TPsy (cationic, PZC = 6.23), which significantly enhances its efficiency as an anionic dye adsorbent.

Experimental and theoretical insights into the adsorption mechanism of methylene blue on the (002) WO3 surface

This work investigates the efficiency of green-synthesized WO3 nanoflakes for the removal of methylene blue dye. The synthesis of WO3 nanoflakes using Hyphaene thebaica fruit extract results in a material with a specific surface area of 13 m2/g and an average pore size of 19.3 nm. A combined theoretical and experimental study exhibits a complete understanding of the MB adsorption mechanism onto WO3 nanoflakes. Adsorption studies revealed a maximum methylene blue adsorption capacity of 78.14 mg/g. The pseudo-second-order model was the best to describe the adsorption kinetics with a correlation coefficient (R2) of 0.99, suggesting chemisorption. The intra-particle diffusion study supported a two-stage process involving surface adsorption and intra-particle diffusion. Molecular dynamic simulations confirmes the electrostatic attraction mechanism between MB and the (002) WO3 surface, with the most favorable adsorption energy calculated as -0.68 eV. The electrokinetic study confirmed that the WO3 nanoflakes have a strongly negative zeta potential of -31.5 mV and a uniform particle size of around 510 nm. The analysis of adsorption isotherms exhibits a complex adsorption mechanism between WO3 and MB, involving both electrostatic attraction and physical adsorption. The WO3 nanoflakes maintained 90% of their adsorption efficiency after five cycles, according to the reusability tests.

Environmental pH and compound structure affect the activity of short-chain carboxylic acids against planktonic growth, biofilm formation, and eradication of the food pathogen Salmonella enterica

Short-chain carboxylic acids (SCCAs) that are naturally produced by microbial fermentation play an essential role in delaying microbial spoilage. SCCAs are structurally diverse, but only a few of them are routinely used in food biopreservation. This study investigated the effects of environmental pH and intrinsic properties of 21 structurally different SCCAs on the antimicrobial and antibiofilm activity against Salmonella enterica. Inhibition of SCCA toward planktonic and biofilm growth of S. enterica was higher in an acidic environment (pH 4.5) that is common in fermented products, and for SCCA that possessed both a high acid dissociation strength (pKa) (>4.0) and a positive hydrophobicity [octanol/water partition coefficient (log Kow)]. Crotonic and caproic acids were identified as SCCAs with potential as biopreservatives even at near-neutral pH. SCCA with hydrophilic groups such as lactic acid did not inhibit S. enterica at concentrations up to 50 mM, while SCCA with benzene or methyl groups or a double bond prevented S. enterica growth and biofilm formation. Stimulation of biofilm formation was observed for formic, acetic, and propionic acid close to the minimum inhibitory concentration to reduce 50% of cell density (MIC50) of planktonic cells, and for citric and isocitric acid with an MIC50 of ≥50 mM. The presence of low concentrations of formic and propionic acids during biofilm formation conferred protection during eradication possibly due to a pre-adaptation effect, yet two consecutive acid treatments were successful in eradicating biofilms if the first acid treatment was two- to threefold of the MIC50.IMPORTANCEThis study provides a systematic comparison on the antimicrobial and antibiofilm activity of more than 20 structurally different SCCAs against a common food pathogen. We tested the antimicrobial activity at controlled pH and identified the structure-dependent antimicrobial effects of SCCA without the confounding influence of acidification. The combined effect of pKa and log Kow was identified as an important feature that should be considered when deciding for a specific SCCA in the application as antimicrobial. Our results imply that additional phenomena such as the use of SCCA as substrate and cellular pre-adaption effects have to be taken into consideration. We finally present a two-step treatment as an efficient approach to eradicate biofilms, which can be applied for the disinfection of contact surfaces and manufacturing equipment. Results obtained here can serve as guidelines for application of SCCA to avoid the growth of food pathogens and/or to develop biopreserved food systems.

Characterization and application of natural Moroccan material for methyl violet 2B dye removal from aqueous solution

In this paper, a natural Moroccan material from the Nador area in the north east of Morocco was studied as an adsorbent to remove methyl violet 2B dye from aqueous solutions. This material has never been studied before in this region, and it will be used in its raw state. It was collected and characterized by X-ray diffraction, FTIR spectroscopy, scanning electron microscopy, X-ray fluorescence, thermal analysis, N2 gas adsorption-desorption, pHPZC, and Brunauer-Emmett-Teller (BET). The studies are realized with a 500-µm grain size and 182m2/g BET surface area. XRD showed the presence of significant peaks belonging to natural zeolite type clinoptilolite-Ca and minor phases. Several parameters were studied such as contact time, adsorbent mass, initial dye concentration, initial pH solution, the particle size of the material, and temperature. Out of the three isotherm models investigated after 60 min of contact time in the experiments, the Langmuir model gave the best fit to the experimental data (R2 = 0.99). The results of kinetic and thermodynamic studies revealed that the adsorption process obeyed pseudo-second-order, spontaneous (ΔG° < 0), endothermic (ΔS° > 0). The adsorption of methyl violet 2B dye is chemisorptions and physisorption. The maximum theoretical adsorption capacity was 30.30 mg·g-1 at 23 °C for a particle diameter of 500 µm. The desorption study shows that the material can be desorbed using solvents. The reuse study indicates that the same amount of natural zeolite can be used several times which makes the process efficient and sustainable. The obtained results indicate that the country of Morocco has natural zeolite among its resources and that it can be used as an efficient adsorbent for the removal of dyes.

Management of trihalomethanes in water by ZnO@kaolinite composite: integrated experimental and modeling studies

The adsorption of trihalomethanes (THMs) from drinking water was investigated in the current study through comparison studies of kaolinite and ZnO@kaolinite nanocomposites. The clay structural network's successful immobilization on the zincite hexagonal structure of ZnO nanoparticles' lattice layers was verified by the SEM/EDX analysis. Under the optimum conditions, the maximum removal of THMs was achieved by kaolinite and ZnO@kaolinite nanocomposites after 60 min. The adsorption performance of the ZnO@kaolinite nanocomposites was greater than that of kaolinite because the former had a larger surface area than the latter. The Freundlich isotherm model best matched the adsorption experimental data, which also reveals the existence of multilayer adsorption on a diverse surface with the greatest correlation (R2 = 0.956 and 0.954, respectively) for both nanoadsorbents using the pseudo-first-order (PFO), pseudo-second-order (PSO), mixed 1, 2-order (MFSO), and intraparticle diffusion (IPD) models. The mechanism by which THMs in drinking water adsorb onto nanoadsorbents was examined. This revealed that both intraparticle and film diffusion were involved in the adsorption process. Kaolinite and ZnO@kaolinite nanocomposites can be used in water treatment to remove THMs due to their great recyclable and reusable properties, even after six cycles.

Unlocking Cd(II) biosorption potential of Candida tropicalis XTA 1874 for sustainable wastewater treatment

Cd(II) is a potentially toxic heavy metal having carcinogenic activity. It is becoming widespread in the soil and groundwater by various natural and anthropological activities. This is inviting its immediate removal. The present study is aimed at developing a Cd(II) resistant strain isolated from contaminated water body and testing its potency in biological remediation of Cd(II) from aqueous environment. The developed resistant strain was characterized by SEM, FESEM, TEM, EDAX, FT-IR, Raman Spectral, XRD and XPS analysis. The results depict considerable morphological changes had taken place on the cell surface and interaction of Cd(II) with the surface exposed functional groups along with intracellular accumulation. Molecular contribution of critical cell wall component has been evaluated. The developed resistant strain had undergone Cd(II) biosorption study by employing adsorption isotherms and kinetic modeling. Langmuir model best fitted the Cd(II) biosorption data compared to the Freundlich one. Cd(II) biosorption by the strain followed a pseudo second order kinetics. The physical parameters affecting biosorption were also optimized by employing response surface methodology using central composite design. The results depict remarkable removal capacity 75.682 ± 0.002% of Cd(II) by the developed resistant strain from contaminated aqueous medium using 500 ppm of Cd(II). Quantitatively, biosorption for Cd(II) by the newly developed resistant strain has been increased significantly (p < 0.0001) from 4.36 ppm (non-resistant strain) to 378.41 ppm (resistant strain). It has also shown quite effective desorption capacity 87.527 ± 0.023% at the first desorption cycle and can be reused effectively as a successful Cd(II) desorbent up to five cycles. The results suggest that the strain has considerable withstanding capacity of Cd(II) stress and can be employed effectively in the Cd(II) bioremediation from wastewater.

Enhancing Eritadenine Production in Submerged Cultures of Shiitake (Lentinula edodes Berk. Pegler) Using Blue LED Light and Activated Charcoal. Revealing Eritadenine's Novel In Vitro Bioherbicidal Activity Against Chrysanthemum morifolium

Eritadenine from shiitake mushroom is a secondary metabolite with hypocholesterolemic, hypotensive and antiparasitic properties, thus promising for pharmaceutical and agricultural applications. Eritadenine is obtained from submerged mycelial cultures of shiitake, but the actual yields remain unsatisfactory to explore potential applications or industrial-scale production. In this study, green and blue LED lights were tested to increase yields of eritadenine in submerged cultures of shiitake. Notably, blue LEDs increased yields by 13-14 times, reaching 165.7 mg/L, compared to darkness (11.2 mg/L) and green light (12.1 mg/L) (p < 0.05, Tukey test). Nitrogen sources yeast extract (YE) and peptone (at 2 g/L) increased eritadenine production. YE promoted 22.6 mg/L, while peptone 18.3 mg/L. The recovery of eritadenine was evaluated using amberlite and activated charcoal (AC) adsorption isotherms. AC demonstrated the highest adsorption rate, with 75 mg of eritadenine per gram of AC, according to the Freundlich isotherm. The desorption rate reached 93.95% at pH 10. The extract obtained from submerged cultures had eritadenine content of 63.31%, corresponding to 87.86% of recovery, according to HPLC analysis. Furthermore, the novel bioherbicidal potential of eritadenine was tested on in vitro Chrysanthemum morifolium plants. The cultures extract containing eritadenine had a detrimental impact on plant development, generating mortality of 100% at 3%, 0.5%, and 0.25%. Moreover, pure eritadenine exhibited a phytotoxic effect similar than glyphosate on leaves, stems and roots. These findings highlight the significant bioherbicidal properties of eritadenine. Further studies are needed to understand the biosynthetic pathway of eritadenine and its bioherbicidal properties on weeds and illicit crops.

Fabrication of peptide-encapsulated sodium alginate hydrogel for selective gallium adsorption

Peptides are recognized as promising adsorbents in metal selective recovery. In this study, the designed gallium-binding peptide H6GaBP was immobilized by the polysaccharide polymer sodium alginate (SA) for gallium recovery. The synthesized H6GaBP@SA microspheres exhibited a maximum adsorption capacity of 127.4 mg/g and demonstrated high selectivity for gallium at lower pH values. The adsorption process aligned well with the pseudo-second-order equation and Langmuir model. To elucidate the adsorption mechanism, a comprehensive characterization including molecular docking, scanning electron microscope coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetry analysis (TGA), were conducted. These analyses revealed that gallium ions were initially adsorbed through electrostatic interaction by H6GaBP@SA, followed by a cation exchange reaction between Ga(OH)2+ and Ca2+, as well as coordination between gallium and histidine residues on the peptide. Moreover, the H6GaBP@SA exhibited improved thermal stability compared to sole sodium alginate microspheres, and the coordination of gallium with peptides can also defer the decomposition rate of the adsorbents. Compared to other adsorbents, the peptide-encapsulated hydrogel microspheres exhibited superior gallium selectivity and improved adsorption capacity, offering an environmentally friendly option for gallium recovery.

Montmorillonite modified Ni/Mg/Al ternary layered double hydroxide nanoflowers with enhanced adsorption features

A hydrothermal technique was employed to synthesize Ni/Mg/Al ternary L.D.H.s modified with montmorillonite (NMA-MMT-LDHs). Many characterization methods, including X-ray diffraction (XRD), scanning electron microscopy (S.E.M.), Fourier transform infrared (FTIR), and Brunauer, Emmett, and Teller (B.E.T.), were used to assess the physiochemical properties of the produced analytes. Congo red and methylene blue were utilized as model dyes to treat textile waste with the synthesized analytes. The batch adsorption model was utilized to conduct the adsorption experiments under varying contact time, adsorbent dosage, and solution pH conditions. A pseudo-second-order kinetics and the Langmuir adsorption model control the adsorption process. The maximum monolayer adsorption capacities of C.R. and M.B. were determined to be 344 and 200 mg/g, respectively. As the quantity of dosage increased from the 0.01-0.04 g, the percent removal efficiency (%) increased from 75 to 87 % for S2-LDH, 84-88 % for S2-MMT, 86-93 % for S3-MMT, and 95-97% for S4-MMT for C.R. dye and 82-85 % for S2-LDH, 83-89 % for S2-MMT, 83-91 % for S3-MMT, and 84-92 % for S4-MMT for M.B. dye. The removal percentage of C.R. dye for adsorbents S2-LDH, S2-MMT, S3-MMT, and S4-MMT were 75 %, 84 %, 86 %, and 95 %, respectively and 82 %, 83 %, 83 %, and 85 %, respectively for the M.B. dye removal. The presence of MMT significantly increases the affinity of Ni/Mg/Al-LDHs (NMA-LDHs), and the designed production technique can be used to produce a variety of compositionally distinct adsorbent materials.

Competitive and cooperative adsorption analysis for dye removal from multicomponent system using Prosopis juliflora activated carbon

In this study, performance evaluation of two adsorbents synthesized using invasive weed, i.e., Prosopis juliflora, was chemically activated using hydrochloric acid (HPJ) and sodium hydroxide (NPJ). The synthesized adsorbents HPJ and NPJ were subjected to SEM, EDX, XRD, FTIR, and porosimetry analysis for characterization and applied for adsorptive removal of rhodamine B (RB) and methyl orange (MO) dyes from monocomponent (MO/RB) and multicomponent (MO + RB) systems in batch mode. Meanwhile, the effect of operational parameters such as contact time, HPJ and NPJ dosage, MO/RB concentration, and [Formula: see text] on sorption of MO/RB dyes was investigated. The adsorption data was modeled through various kinetic and equilibrium models. On the other hand, the multi-dye sorption system was modeled using Langmuir competitive isotherm. Furthermore, the effect of presence of one dye on sorption of other and vice versa, i.e., competitive (antagonistic) and cooperative (synergistic) nature of sorption process, was investigated. From the results, it was observed that pseudo-second-order kinetic and Langmuir isotherm models best fit the adsorption kinetic and equilibrium data for sorption of MO and RB dyes using both HPJ and NPJ as adsorbents. Langmuir's maximum sorption ability (qm) of HPJ for sorption of MO and RB dyes was observed to be 12.77 mg/g and 9.95 mg/g, respectively, from the monocomponent system. On the other hand, qm of NPJ for sorption of MO and RB dyes was observed to be 10.51 mg/g and 8.69 mg/g, respectively. Langmuir's sorption ability (qm) was slightly higher in the MO + RB mixture in contrast to MO/RB. As a result, the sorption of MO/RB dyes from the MO + RB system showed synergistic nature. In conclusion, the HPJ and NPJ could be effectively used as sorbents for sorption of dyes from effluents.

KMnO4-oxidized whole pine needle based adsorbent for selective and efficient removal of cationic dyes

In the present study, we report the chemical modification of the dried and fallen pine needles (PNs) via a simple protocol using KMnO4 oxidation. The oxidized PNs (OPNs) were evaluated as adsorbents using some cationic and anionic dyes. The successful synthesis of OPNs adsorbent was characterized by various techniques to ascertain its structural attributes. The adsorbent showed selectivity for the cationic dyes with 96.11% removal (Pr) for malachite green (MG) and 89.68% Pr for methylene blue (MB) in 120 min. Kinetic models namely, pseudo-first order, pseudo-second order, and Elovich were applied to have insight into adsorption. Additionally, three adsorption isotherms, i.e., Langmuir, Freundlich, and Temkin were also applied. The dye adsorption followed a pseudo-second-order kinetic model with R2 > 0.99912 for MG and R2 > 0.9998 for MB. The adsorbent followed the Langmuir model with a maximum adsorption capacity (qm) of 223.2 mg/g and 156.9 mg/g for MG and MB, respectively. Furthermore, the OPNs showed remarkable regeneration and recyclability up to nine adsorption-desorption cycles with appreciable adsorption for both the dyes. The use of OPNs as an adsorbent for the removal of dyes from wastewater, therefore, provides an ecologically benign, low-cost, and sustainable solution.

Porous Hierarchical Ni/Mg/Al Layered Double Hydroxide for Adsorption of Methyl Orange from Aqueous Solution

A basic urea technique was successfully used to synthesize Mg/Al-Layered double hydroxides (Mg/Al LDHs), which were then calcined at 400 °C to form Mg/Al-Layered double oxides (Mg/Al LDOs). To reconstruct LDHs, Mg/Al LDOs were fabricated with different feeding ratios of Ni by the co-precipitation method. After synthesis, the Ni/Mg/Al-layered double hydroxides (NMA-LDHs) with 20% and 30% Ni (S1 and S2) were roasted at 400 °C and transformed into corresponding Ni/Mg/Al-layered double oxides (NMA-LDOs) (S1a and S2b, respectively). The physiochemical properties of synthesized samples were also evaluated by various characterization techniques, such as X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared (FTIR), and Brunauer, Emmett, and Teller (BET). The adsorption behavior of methyl orange (MO) onto the synthesized samples was evaluated in batch adsorption mode under varying conditions of contact time, adsorbent quantity, and solution pH. As the dosage amount increased from 0.01-0.04 g, the removal percentage of MO dye also increased from 83% to 90% for S1, 84% to 92% for S1a, 77% to 87% for S2, and 93% to 98% for S2b, respectively. For all of the samples, the adsorption kinetics were well described by the pseudo-second-order kinetic model. The equilibrium adsorption data were well fitted to both Langmuir and Freundlich models for methyl orange (MO). Finally, three adsorption-desorption cycles show that NMA-LDHs and NMA-LDOs have greater adsorption and reusability performance for MO dye, signifying that the design and fabrication strategy can facilitate the application of the natural hydrotalcite material in water remediation.

Sphagnum perichaetiale Hampe biomass as a novel, green, and low-cost biosorbent in the adsorption of toxic crystal violet dye

In this study, the Sphagnum perichaetiale Hampe biomass was collected, characterized, and used as a biosorbent in the removal of crystal violet from water. The chemical and morphological results suggest that even after minimal experimental procedures, the biomass presented interesting properties regarding the adsorption of contaminants. Results of adsorption showed that the pH was not a relevant parameter and the best adsorbent dosage was 0.26 g L^-1. The kinetic results presented an initial fast step and the equilibrium was reached after 180 min. For the equilibrium data, the best adjustment occurred for the Sips model, reaching a maximum adsorption capacity of 271.05 mg g^-1 and the removal percentage obtained in the maximum adsorbent dosage was 97.11%. The thermodynamic studies indicated a reversible process and that the mass-transfer phenomena is governed by the physisorption mechanism. In addition to its great performance as a biosorbent, Sphagnum perichaetiale biomass also presents economic and sustainable benefits, as its production does not require costs with reagents or energy, usually used in chemical and physical activation. The reversible process indicated that the biosorbent could be reused, decreasing the costs related to the treatment of the effluents. Thus, Sphagnum perichaetiale biomass can be considered an efficient low-cost and eco-friendly biosorbent.

Large-Scale Production of Isocitric Acid Using Yarrowia lipolytica Yeast with Further Down-Stream Purification

Isocitric acid (ICA) refers to a group of promising regulators of energy metabolism which has antistress, antihypoxic, and antioxidant activities. In this paper, we reported a process of ICA production from rapeseed oil using yeast Yarrowia lipolytica VKM Y-2373 in a 500-L fermentor. The producer synthesized 64.1 g/L ICA with a product yield of 0.72 g/g and a productivity 0.54 g/L·h. We also developed an effective purification method, including a cell separation, clarification, concentration, acidification, and crystallization process, which resulted in the formation of the crystals of monopotassium salt of ICA with a purity of 99.0–99.9%. To the best of our knowledge, this is the first report on an ICA production process at an upscaled bioreactor level.

Synthesis of hybrid biosorbent based on 1,2-cyclohexylenedinitrilotetraacetic acid modified crosslinked chitosan and organo-functionalized calcium alginate for adsorptive removal of Cu(II)

The present study is based on the synthesis of a novel hybrid biosorbent using 1,2-cyclohexylenedinitrilotetraacetic acid modified crosslinked chitosan and amino-thiocarbamate moiety functionalized sodium alginate (CDTA-CS/TSC-CA). The fabricated sorbent was employed to investigate the efficient recovery of Cu(II) from aqueous media. CDTA-CS/TSC-CA was characterized using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Analysis confirmed the successful modification of both biopolymers and subsequent loading of Cu(II) ions. CDTA-CS/TSC-CA was casted in the form of hydrogel beads having different CDTA-CS to TSC-CA mass ratios i.e., 10.0-40.0% by mass. The hydrogel beads 4CDTA-CS/TSC-CA with CDTA-CS/TSC-CA mass ratio of 40.0% was found most effective for copper sorption. Equilibrium sorption results showed that initial concentration of copper, medium pH, contact time, sorbent dosage and temperature influenced the sorption capacity (q_e). Rate of sorption data was interpreted using different kinetic models and found best fitted with pseudo second order rate expression (R² ≈ 0.99), illustrating that the rate determining step includes the electron density transfer from sorbent coordination sites to central copper ions. Crank's RIDE equation and Elovich chemisorption model (ECM) revealed the presence of two sorption phases, initially rapid sorption followed by comparatively a slow uptake. Equilibrium sorption data was well depicted by Langmuir model and maximum monolayer adsorption capacity (q_m) was computed as 276.53 mg·g^-1 at 298 K. Standard Gibbs free energy change, ∆G° (-19.99, -20.18 and -20.36 kJ/ mol), standard enthalpy change, ∆H° (-8.95 kJmol) and standard entropy change, ∆S° (0.04 kJ/mol K^-1) values suggested that the adsorption process is spontaneous and exothermic. Hence, 4CDTA-CS/TSC-CA was found efficient biosorbent for copper removal from its dilute effluents.

Recycled mesoporous magnetic composites with high surface area derived from plastic and de-oiled sludge wastes: An empirical comparison on their competitive performance for toxic Cr (VI) removal

The current study focused on the comparative removal of hexavalent chromium using two magnetically modified hybrid adsorbent composites. Their precursor chars were prepared from bio sludge and plastic waste derivatives. The coating of magnetite on the chars' surface was evident from the SEM micrographs. Infusion of magnetite nanoparticles in the native chars aided in the reduction of the composite particles' sizes, thus, forming high surface area composites. Screening of uptake capacities among various blends of char and magnetite were surveyed. Composites of both kinds with a 1:5 ratio of char: iron salts composition answered well. The pH_ZPC and zeta potential values of the composites indicated the neutral charge on the composites' surface. This suggested the need for a highly acidic environment for efficient Cr(VI) removal. Optimum economic conditions for Cr(VI) removal were obtained from the batch studies (solution pH - 1.5; contact time - (a) MPC [magnetic plastic char] - 60 min (b) MBC [magnetic biochar] - 40 min; temperature - 25 °C). The maximum monolayer adsorption capacity of MPC and MBC were found to be 84.67 mg/g and 53.83 mg/g respectively. Isotherm, kinetic and thermodynamic studies revealed the adsorption systems' inclination towards physisorption. From the characterization and modeling results, electrostatic force of attraction and pore filling was anticipated to be the mechanism of adsorption for both MPC and MBC. Thus, in the relative removal studies, MBC was found to compete better than MPC due to its enhanced porosity and surface area.

Effect of Metabolic Regulators and Aeration on Isocitric Acid Synthesis by Yarrowia lipolytica Grown on Ester-Aldehyde Fraction

Isocitric acid (ICA) has found wide application in medicine as a promising compound with powerful antioxidant activity to combat oxidative stress. In the known microbiological processes of ICA production by non-conventional yeast Yarrowia lipolytica, the pure carbon sources are commonly used. ICA can be also synthetized by Y. lipolytica from ester-aldehyde fraction (EAF)-waste of the ethanol production process. A highly effective method of ICA production from EAF based on regulation of key enzymes (aconitate hydratase and isocitrate lyase) by metabolic regulators (iron and itaconic acid) and aeration was developed. It is recommended to cultivate Y. lipolytica VKM Y-2373 under nitrogen deficiency conditions, a high aeration (60% of air saturation), an addition of 15 mM itaconic acid, and 2.4 mg/L iron. Under optimal conditions, Y. lipolytica VKM Y-2373 produced 83 g/L ICA with isocitrate to citrate ratio of 4.1:1 and mass yield of 1.1 g/g. The putative mechanism of ICA overproduction from EAF by Y. lipolytica was suggested.

Synthesis and performance evaluation of plastic waste aerogel as sustainable and reusable oil absorbent

Direct utilization of waste polyethylene terephthalate (PET) from the environment to form highly porous aerogel technology for oil absorption is an attractive approach from the view point of green chemistry. However, the oil absorption reaction is limited by low oil absorption capacity and less stability. For now, silica aerogel are used to solve these problem. Our goal is to substitute to these silica aerogel with PET aerogel technology. Herein, we have prepared an environmental waste PET based aerogel with 1.0:0.5 wt% PET, polyvinyl alcohol (PVA), and glutaraldehyde (GA) 0.2% v/v were dispersed in 10 mL DI water, followed by homogenization (30 min), sonication (10 min), and ageing (2 h) at 70 °C. To escape macroscopic cracking, cooling (8 h) at 4 °C was followed by freezing (6 h), freeze drying at -80 °C, and 5 mTorr for 18 h. The hybrid PET aerogel displays excellent performance towards oil absorption. Notably it showed high absorption capacity towards the different oils about 21-40 times its own weight, depending on the viscosity and density of the oil and solvents within 15-35 s, 25 °C, and 2 × 2 cm aerogel size. In addition, the aerogel shows there is no change in structure after several recycles due to high mechanical strength. Furthermore, because of the PET aerogel's high porosity (99.74%) and low density (0.0311 g/cm³), close bonding between PET-PVA occurs. Therefore, aerogel shows hydrophobic nature, good mechanical strength, high thermal stability, arrangement of the interconnected fibrillar pore network offers a high surface to volume ratio, low surface energy, high surface roughness, and more reusability. All these parameters are responsible for high oil absorption.

Mechanism-Based Inactivation of Mycobacterium tuberculosis Isocitrate Lyase 1 by (2R,3S)-2-Hydroxy-3-(nitromethyl)succinic acid

The isocitrate lyase paralogs of Mycobacterium tuberculosis (ICL1 and 2) are essential for mycobacterial persistence and constitute targets for the development of antituberculosis agents. We report that (2R,3S)-2-hydroxy-3-(nitromethyl)succinic acid (5-NIC) undergoes apparent retro-aldol cleavage as catalyzed by ICL1 to produce glyoxylate and 3-nitropropionic acid (3-NP), the latter of which is a covalent-inactivating agent of ICL1. Kinetic analysis of this reaction identified that 5-NIC serves as a robust and efficient mechanism-based inactivator of ICL1 (kinact/KI = (1.3 ± 0.1) × 103 M-1 s-1) with a partition ratio <1. Using enzyme kinetics, mass spectrometry, and X-ray crystallography, we identified that the reaction of the 5-NIC-derived 3-NP with the Cys191 thiolate of ICL1 results in formation of an ICL1-thiohydroxamate adduct as predicted. One aspect of the design of 5-NIC was to lower its overall charge compared to isocitrate to assist with cell permeability. Accordingly, the absence of the third carboxylate group will simplify the synthesis of pro-drug forms of 5-NIC for characterization in cell-infection models of M. tuberculosis.

Prediction of Europium Retention in Perovskite: Potential Candidates for an Engineering Barrier in the Disposal of Radioactive Waste

Perovskites, such as tausonite, are crystalline metal oxides with excellent optical and photocatalytic properties and have also been used successfully in the retention of metals, simulating the isotopes of uranium and plutonium. In this work, different pseudo-order and thermodynamic models were studied to achieve the prediction of the sorption of Eu3+ (chemical analogous for actinides) in tausonite. The effects of gamma irradiation and temperature on the structural characteristics of the material were determined, as an additional step in the evaluation of material as an engineering barrier in the disposal of radioactive waste. The results obtained show that the tausonite is resistant to the gamma irradiation and thermal energy. Likewise, it was possible to determine that europium sorption occurs through an exothermic and spontaneous reaction, as well as through the formation of surface complexes, where Eu3+ ions bind to sites on the tausonite by dipole-dipole interaction. Furthermore, it was shown that the sorption mechanism is influenced by diffusive phenomena, which participate in the formation of surface complexes. Additionally, a new sorption model with respect to pH was proposed, which allowed determining the physical parameter π. The evidence obtained suggests that π is a physical parameter that relates pH to an optimal value and could explain the equilibrium between the surface complexes that tausonite forms with europium. Likewise, the evidence suggests that 50 kg of tausonite would have the capacity to retain at least 26.59 g of alpha-emitting radionuclides, equivalent to a waste package (900 kg) with a maximum activity of 4000 Bq/g.

Isocitric Acid Production from Ethanol Industry Waste by Yarrowia lipolytica

There is ever increasing evidence that isocitric acid can be used as a promising compound with powerful antioxidant activity to combat oxidative stress. This work demonstrates the possibility of using waste product from the alcohol industry (so-called ester-aldehyde fraction) for production of isocitric acid by yeasts. The potential producer of isocitric acid from this fraction, Yarrowia lipolytica VKM Y-2373, was selected by screening of various yeast cultures. The selected strain showed sufficient growth and good acid formation in media with growth-limiting concentrations of nitrogen, sulfur, phosphorus, and magnesium. A shortage of Fe2+ and Ca2+ ions suppressed both Y. lipolytica growth and formation of isocitric acid. The preferential synthesis of isocitric acid can be regulated by changing the nature and concentration of nitrogen source, pH of cultivation medium, and concentration of ester-aldehyde fraction. Experiments in this direction allowed us to obtain 65 g/L isocitric acid with a product yield (YICA) of 0.65 g/g in four days of cultivation.

Phosphate Adsorption from Aqueous Solution Using Electrospun Cellulose Acetate Nanofiber Membrane Modified with Graphene Oxide/Sodium Dodecyl Sulphate

Eutrophication and water pollution caused by a high concentration of phosphate are two concerning issues that affect water quality worldwide. A novel cellulose-based adsorbent, cellulose acetate/graphene oxide/sodium dodecyl sulphate (CA/GO/SDS), was developed for water treatment. A 13% CA solution in a mixture of acetone:dimethylacetamide (2:1) has been electrospun and complexed with a GO/SDS solution. The field emission scanning electron microscope (FESEM) showed that the CA membrane was pure white, while the CA/GO/SDS membrane was not as white as CA and its colour became darker as the GO content increased. The process of phosphate removal from the solutions was found to be aided by the hydroxyl groups on the surface of the CA modified with GO/SDS, as shown by infrared spectroscopy. An optimization condition for the adsorption process was studied by varying pH, immersion time, and the mass of the membrane. The experimental results from phosphate adsorption showed that CA/GO/SDS had an excellent pH adaptability, with an optimum pH of 7, and maximum removal (>87.0%) was observed with a membrane mass of 0.05 g at an initial concentration of 25 mg L^-1. A kinetic study revealed that 180 min of contact time could adsorb about 87.2% of phosphate onto the CA/GO/SDS membrane. A typical pseudo-second-order kinetic model successfully portrayed the kinetic sorption of phosphate, and the adsorption equilibrium data were well-correlated with the Langmuir adsorption model, suggesting the monolayer coverage of adsorbed molecules.

A comparative study of ceramic nanoparticles synthesized for antibiotic removal: catalysis characterization and photocatalytic performance modeling

The heterogeneous photocatalysis process has been known to provide significant levels of degradation and mineralization of emerging contaminants including antibiotics. For that, nanoparticle CuCr₂O₄ (CCO) ceramics were successfully prepared via sol-gel (SG) and co-precipitation (CP) methods to obtain spinel with desired structural features and properties and also to improve the photocatalytic performances. The CCO crystallite phase was produced at 750 °C all ceramics, disregarding the synthesis route. CCO physical and chemical properties were checked by X-ray diffraction (XRD) with Rietveld refinement, Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), and diffuse reflectance solid (DRS). The XRD patterns demonstrated that the synthesized catalysts displayed a small crystallite size between 17.45 and 26.24 nm for SG and 20.97 and 36.86 nm for the CCO_CP samples. The observation by SEM and TEM of the nanopowders showed a typical morphology with comparable particle sizes for both synthesized routes (20-30 nm). SG agglomeration rates were higher, and particles stick together more efficiently considering the CP method, while the CCO_CP method led to a more significant porosity. Their photocatalytic and adsorption performances were examined for cefaclor (CFC) removal chosen as a target pharmaceutical contaminant in water. The results obtained by the methods differed since nanoparticles prepared by SG led to high photocatalytic activity. In contrast, a high CFC adsorption was observed for those prepared via the CP method, and that agreed with the findings of the characterization analysis. The kinetics of the adsorption process was found to follow the pseudo-second-order rate law. In contrast, the data of the photodegradation process were further found to comply with the Lagergren kinetic law. Nevertheless, the global reaction rate is probably controlled by the intra-particular diffusion of CFC, regardless of the elimination process.

Study on the preparation of the hierarchical porous CX-TiO2 composites and their selective degradation of PHE solubilized in soil washing eluent

A series of CX-TiO₂(Carbon Xerogel- TiO₂) composites with a hierarchical porous structure were obtained through the sol-gel method followed by drying and carbonization, and have been applied to treating solubilizing wastewater containing a high concentration of phenanthrene (PHE). The characterizations demonstrated that the CX-TiO₂ exhibits a hierarchical porous structure, with particles of carbon and P25 being uniformly in the matrix. Removal efficiency of CX-TiO₂ on PHE in soil washing eluent (SWE) were evaluated under ultraviolet (UV) irradiation or dark condition, and P25 was employed as the reference. The results revealed that CX-TiO₂(0.2) had the best removal effect on PHE, with the efficiency as high as 97.8% under UV illumination within 15 h. It demonstrated that in the process of PHE removal by CX-TiO₂ whether it was under UV illumination or not, the adsorption plays a dominant role in the early stage. The kinetic behavior of PHE adsorption was fitted using the pseudo-first-order and pseudo-second-order, and Langmuir model and Freundlich models were applied to describe the PHE adsorption isotherms. The results indicating that it was a chemical adsorption process, which was influenced by the interaction between PHE and CX-TiO₂, and PHE is adsorbed on the interface of CX-TiO₂(0.2) in a single layer form, instead of agglomerating in the admicelle. A possible mechanism of removal of solubilized PHE in SWE was speculated, in which both hierarchical porous structure and appropriate micropores size of CX-TiO₂ were indispensable to the selective adsorption and degradation of PHE. Recycling performance certificated that the selective removal efficiency of PHE could still reach 82.09% after five recycles. Thus the excellent performance testified that the CX-TiO₂ have great potential in treating SWE containing solubilized PAHs.

Effects of Medium Components on Isocitric Acid Production by Yarrowia lipolytica Yeast

The microbiological production of isocitric acid (ICA) is more preferable for its application in medicine and food, because the resulting product contains only the natural isomer—threo-DS. The aim of the present work was to study ICA production by yeast using sunflower oil as carbon source. 30 taxonomically different yeast strains were assessed for their capability for ICA production, and Y. lipolytica VKM Y-2373 was selected as a promising producer. It was found that ICA production required: the limitation of Y. lipolytica growth by nitrogen, phosphorus, sulfur or magnesium, and an addition of iron, activating aconitate hydratase, a key enzyme of isocitrate synthesis. Another regulatory approach capable to shift acid formation to a predominant ICA synthesis is the use of inhibitors (itaconic and oxalic acids), which blocks the conversion of isocitrate at the level of isocitrate lyase. It is recommended to cultivate Y. lipolytica VKM Y-2373 under nitrogen deficiency conditions with addition of 1.5 mg/L iron and 30 mM itaconic acid. Such optimized nutrition medium provides 70.6 g/L ICA with a ratio between ICA and citric acid (CA) equal 4:1, a mass yield (YICA) of 1.25 g/g and volume productivity (QICA) of 1.19 g/L·h.

Engineering Yarrowia lipolytica for the selective and high-level production of isocitric acid through manipulation of mitochondrial dicarboxylate-tricarboxylate carriers

During cultivation under nitrogen starvation, Yarrowia lipolytica produces a mixture of citric acid and isocitric acid whose ratio is mainly determined by the carbon source used. We report that mitochondrial succinate-fumarate carrier YlSfc1 controls isocitric acid efflux from mitochondria. YlSfc1 purified and reconstituted into liposomes transports succinate, fumarate, oxaloacetate, isocitrate and α-ketoglutarate. YlSFC1 overexpression determined the inversion of isocitric acid/citric acid ratio towards isocitric acid, resulting in 33.4 ± 1.9 g/L and 43.3 ± 2.8 g/L of ICA production in test-tube cultivation with glucose and glycerol, respectively. These titers represent a 4.0 and 6.3-fold increase compared to the wild type. YlSFC1 gene expression was repressed in the wild type strain grown in glucose-based medium compared to olive oil medium explaining the reason for the preferred citric acid production during Y. lipolytica growth on carbohydrates. Coexpression of YlSFC1 and adenosine monophosphate deaminase YlAMPD genes together with inactivation of citrate mitochondrial carrier YlYHM2 gene enhanced isocitric acid accumulation up to 41.4 ± 4.1 g/L with an isocitric acid/citric acid ratio of 14.3 in a small-scale cultivation with glucose as a carbon source. During large-scale cultivation with glucose pulse-feeding, the engineered strain produced 136.7 ± 2.5 g/L of ICA with a process selectivity of 88.1%, the highest reported titer and selectivity to date. These results represent the first reported isocitric acid secretion by Y. lipolytica as a main organic acid during cultivation on carbohydrate. Moreover, we demonstrate for the first time that the replacement of one mitochondrial transport system for another can be an efficient tool for switching product accumulation.

Biochar from Agricultural by-Products for the Removal of Lead and Cadmium from Drinking Water

This study reports the adsorption capacity of lead Pb2+ and cadmium Cd2+ of biochar obtained from: peanut shell (BCM), “chonta” pulp (BCH) and corn cob (BZM) calcined at 500, 600 and 700 °C, respectively. The optimal adsorbent dose, pH, maximum adsorption capacity and adsorption kinetics were evaluated. The biochar with the highest Pb2+ and Cd2+ removal capacity is obtained from the peanut shell (BCM) calcined at 565 °C in 45 min. The optimal experimental conditions were: 14 g L−1 (dose of sorbent) and pH between 5 and 7. The sorption experimental data were best fitted to the Freundlich isotherm model. High removal rates were obtained: 95.96% for Pb2+ and 99.05. for Cd2+. The BCH and BZM revealed lower efficiency of Pb2+ and Cd2+ removal than BCM biochar. The results suggest that biochar may be useful for the removal of heavy metals (Pb2+ and Cd2+) from drinking water.

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.

Sugar Alcohols and Organic Acids Synthesis in Yarrowia lipolytica: Where Are We?

Sugar alcohols and organic acids that derive from the metabolism of certain microorganisms have a panoply of applications in agro-food, chemical and pharmaceutical industries. The main challenge in their production is to reach a productivity threshold that allow the process to be profitable. This relies on the construction of efficient cell factories by metabolic engineering and on the development of low-cost production processes by using industrial wastes or cheap and widely available raw materials as feedstock. The non-conventional yeast Yarrowia lipolytica has emerged recently as a potential producer of such metabolites owing its low nutritive requirements, its ability to grow at high cell densities in a bioreactor and ease of genome edition. This review will focus on current knowledge on the synthesis of the most important sugar alcohols and organic acids in Y. lipolytica.

Biosynthesis of isocitric acid in repeated-batch culture and testing of its stress-protective activity

Biosynthesis of Ds(+)-threo-isocitric acid from ethanol in the Yarrowia lipolytica batch and repeated-batch cultures was studied. Repeated-batch cultivation was found to provide for a good biosynthetic efficiency of the producer for as long as 748 h, probably due to maintenance of high activities of enzymes involved in the biosynthesis of isocitric acid. Under optimal repeated-batch cultivation conditions, the producer accumulated 109.6 g/L Ds(+)-threo-isocitric acid with a production rate of 1.346 g/L h. The monopotassium salt of isocitric acid isolated from the culture liquid and purified to 99.9% was found to remove neurointoxication, to restore memory, and to improve the learning of laboratory rats intoxicated with lead and molybdenum salts. Taking into account the fact that the neurotoxic effect of heavy metals is mainly determined by oxidative stress, the aforementioned favorable action of isocitric acid on the intoxicated rats can be explained by its antioxidant activity among other pharmacological effects.

Aseptic production of citric and isocitric acid from crude glycerol by genetically modified Yarrowia lipolytica

The unconventional yeast Yarrowia lipolytica is known for its capacity to produce citric or isocitric acid from glycerol. In this study a reduction of production cost was achieved by using cheap crude glycerol and conducting the production at pH 3 to prevent bacterial contamination. In this study a Y. lipolytica strain overexpressing Gut1 and Gut2 was used. For the modified strain, crude glycerol proved to be an excellent substrate for production of citric/isocitric acids in aseptic conditions, as the final concentration of these compounds reached 75.9 ± 1.8 g L^-1 after 7 days of batch production. Interestingly, the concentration of isocitric acid was 42.5 ± 2.4 g L^-1, which is one of the highest concentrations of isocitric acid obtained from a waste substrate. In summary, these data show that organic acids can be efficiently produced by the yeast Y. lipolytica from crude glycerol without any prior purification in aseptic conditions.