XAD-2 Resin Research Articles

Effective removal of methyl orange dye using aliquat 336 impregnated Amberlite XAD-2 resin

Methyl orange (MO) dye was removed using Amberlite XAD-2 resin modified by wet impregnation method with Aliquat-336. The modified resin was characterized by FTIR, FE-SEM, SEM with EDX, and pH of zero charge. Experimental parameters such as time, initial dye concentration, pH, temperature, resin dose and presence of NaCl salt affecting the adsorption rate were studied. 2 g.L −1 of resin was found to be optimum for 20 mg.L −1 MO dye. A maximum of 40.93 mg dye was removed per gram of resin. Langmuir, Freundlich, and Temkin isotherms were used to predict the equilibrium points at four temperatures. Pseudo-second-order fitted the kinetic data ( R 2 = 0.982). The resin could be reused for five successive cycles effectively. Also, the prepared resin was used for the removal of a cationic dye, rhodamine-B and an industrial dye, Pink S8EB.

Extraction chromatography based separation of zirconium(IV) from simulated high-level liquid waste using N,N-di-octyl-2-hydroxyacetamide impregnated amberlite XAD-7 resin

Selective separation of zirconium(IV), from the simulated high-level liquid waste solution containing uranium(VI) and trivalent lanthanides, during reprocessing of fast reactor metal fuel was studied by extraction chromatography using N,N-di-octyl-2-hydroxyacetamide (DOHyA) impregnated on to Amberlite XAD-7 resin. The extraction behavior of Zr(IV), Nd(III) and U(VI) with varying concentrations of nitric acid was explored using a solvent impregnated resin with different compositions of DOHyA in XAD-7 [10, 20, 30, 40 and 50 (w/w) %]. The resin exhibited faster kinetics with more than 99 % recovery of Zr(IV) and with an apparent Langmuir adsorption capacity of ∼54 mg.g−1of Zr(IV) on to the resin phase. Quantitative (> 99%) and selective extraction of Zr(IV) with minimum loading of other trivalents and uranium was observed during column chromatography. Results of the study showed that Zr(IV) can be selectively separated in presence of trivalent lanthanides and U(VI).

Simultaneous preconcentrations of Cu(II), Ni(II), and Pb(II) by SPE using E. profundum loaded onto Amberlite XAD-4

In the present study, we used E. profundum loaded onto Amberlite XAD-4 resin for solid-phase extraction (SPE) of Cu(II), Ni(II), and Pb(II). Some conditions of the SPE procedure, for instance, sample flow rate, pH, eluent type and concentration, the sample volume, amount of E. profundum XAD-4 resin, and the effects of foreign interferences ions are discussed in detail. Surface microstructures of the biosorbent were characterized by FTIR, FE-SEM/EDX before and after loading of metals. The biosorption capacities of E. profundum were determined as 49.83, 57.12, and 64.35 mg g−1 for Pb(II), Cu(II), and Ni(II), respectively. The LOD values were calculated as 0.031 ng mL−1, 0.042 ng mL−1, and 0.043 ng mL−1 for Cu(II), Ni(II), and Pb(II), respectively. The linear range was detected as 0.25–25 ng mL−1. RSD values were lower than 5%. The concentrations of metal ions in water and food samples were measured by ICP-OES.

Release of Leu-Pro-Pro from corn gluten meal by fermentation with a Lactobacillus helveticus strain.

Angiotensin-converting enzyme (ACE) inhibitory peptides are potential alternatives to the synthetic ACE inhibitory drugs, but the in vivo antihypertensive effects of most of them have not been confirmed. The tripeptide Leu-Pro-Pro (LPP) is one of the few peptides that have been proved clinically effective in reducing the blood pressure of hypertensive patients and casein is currently its major source. LPP is contained in multiple fractions of zein, and corn gluten meal (CGM) is hence a potential new source of LPP. For this purpose, CGM was fermented with a Lactobacillus helveticus strain and the medium composition was optimized; the decoloration of the resultant hydrolysate was investigated as well. LPP could be successfully released from CGM by fermentation with the strain Lactobacillus helveticus CICC 22536. The highest LPP content and protein recovery of 561 mg kg-1 and 14.92% occurred in the medium containing 20 g L-1 glucose, 15 g L-1 beef extract, 60 g L-1 CGM, 10 g L-1 CaCO3 , 0.5 g L-1 NaCl, and inoculation amount 6%. The supplementation of Flavourzyme® further improved the two parameters to 662 mg kg-1 and 36.94%, respectively. The permeate of the hydrolysate after ultrafiltration through a 5 kDa membrane could be effectively decolored by the macroporous resin XAD-16 without notable protein loss, and its LPP content was further boosted to 743 mg kg-1 . CGM is a potential new source of LPP and its ultrafiltered and decolored hydrolysate could be used to develop new antihypertensive functional foods. © 2021 Society of Chemical Industry.

New Strategies for the Simple and Sensitive Voltammetric Direct Quantification of Se(IV) in Environmental Waters Employing Bismuth Film Modified Glassy Carbon Electrode and Amberlite Resin.

An analytical procedure regarding the determination of selenium(IV) by anodic stripping voltammetry exploiting the in situ plated bismuth film electrode is described. Since organics are commonly present in untreated natural water samples, the use of Amberlite XAD-7 resin turns out to be quite important to avoid problems such as the adsorption of these compounds on the working electrode. The optimum circumstances for the detection of selenium in water using differential pulse voltammetry techniques were found to be as follows: 0.1 mol L−1 acetic acid, 1.9 × 10−5 mol L−1 Bi(III), 0.1 g Amberlite XAD-7 resin, and successive potentials of −1.6 V for 5 s and −0.4 V for 60 s, during which the in situ formation of the bismuth film on glassy carbon and the accumulation of selenium took place. The current of the anodic peak varies linearly with the selenium concentration ranging from 3 × 10−9 mol L−1 to 3 × 10−6 mol L−1 (r = 0.9995), with a detection limit of 8 × 10−10 mol L−1. The proposed procedure was used for Se(IV) determination in certified reference materials and natural water samples, and acceptable results and recoveries were obtained.

Adsorption of 5-Hydroxymethylfurfural, Levulinic Acid, Formic Acid, and Glucose Using Polymeric Resins Modified with Different Functional Groups.

5-hydroxymethylfurfural (5-HMF) is a promising high value-added platform chemical, which can be produced from glucose, fructose, or lignocellulosic biomass via catalysis technology. However, the effective separation of 5-HMF from aqueous solution and actual biomass hydrolysate is still challenging because 5-HMF can be further rehydrated into levulinic acid (LA) and formic acid (FA) under acidic conditions. Herein, the adsorption behavior of glucose and 5-HMF and its follow-up products (LA and FA) from aqueous solutions onto polymeric adsorbents modified with various functional groups (XAD-4, XAD7HP, and XAD761 resins) was systematically investigated. The results showed that XAD761 resin exhibited the highest adsorption selectivity (α5-HMF/glucose = 42.42 ± 5.84, α5-HMF/FA = 18.41 ± 0.50, and α5-HMF/LA = 3.01 ± 0.10) and capacity for 5-HMF (106 mg g–1 wet resin). The adsorption equilibrium was better fitted by the Freundlich isotherm model at the studied range of 5-HMF concentrations. The thermodynamic study and activation energy also revealed that the adsorption process of XAD761 resin for 5-HMF was spontaneous, exothermic, and physical. The kinetic regression results revealed that the kinetic data of 5-HMF was accurately followed by the pseudo-second-order kinetic model. In conclusion, the present study revealed that the potential of phenol formaldehyde resin with hydroxyl groups could be used as an adsorbent for aldehyde organic compounds.

Maternal exposure to polycyclic aromatic hydrocarbons in South Texas, evaluation of silicone wristbands as personal passive samplers

BackgroundPrenatal exposure to polycyclic aromatic hydrocarbons (PAHs) is associated with adverse health effects in children. Valid exposure assessment methods with accurate spatial and temporal resolution across pregnancy is a critical need for advancing environmental health studies.ObjectiveThe objective of this study was to quantify maternal PAH exposure in pregnant women residing in McAllen, Texas where the prematurity rate and childhood asthma prevalence rates are high. A secondary objective was to compare PAH levels in silicone wristbands deployed as passive samplers with concentrations measured using standardized active air-sampling techniques.MethodsParticipants carried a backpack that contained air-sampling equipment (i.e., filter and XAD sorbent) and a silicone wristband (i.e., passive sampler) for three nonconsecutive 24-h periods. Filters, XAD tubes, and wristbands were analyzed for PAHs.ResultsThe median level of exposure for the sum of 16 PAHs measured via active sampling over 24 h was 5.54 ng/m3 (filters) and 43.82 ng/m3 (XADs). The median level measured in wristbands (WB) was 586.82 ng/band. Concentrations of the PAH compounds varied across sampling matrix type. Phenanthrene and fluorene were consistently measured for all participants and in all matrix types. Eight additional volatile PAHs were measured in XADs and WBs; the median level of exposure for the sum of these eight PAHs was 342.98 ng/m3 (XADs) and 632.27 ng/band. The silicone wristbands (WB) and XAD sorbents bound 1-methynaphthalyne, 2-methylnaphthalene, biphenyl following similar patterns of detection.SignificanceSince prior studies indicate linkages between PAH exposure and adverse health outcomes in children at the PAH levels detected in our study, further investigation on the associated health effects is needed. Data reflect the ability of silicone wristbands to bind smaller molecular weight, semivolatile PAHs similar to XAD resin. Application of wristbands as passive samplers may be useful in studies evaluating semivolatile PAHs.

Changes in molecular structure of extracellular polymeric substances (EPS) with temperature in relation to sludge macro-physical properties

Extracellular polymeric substances (EPS) are important components of activated sludge, whose content and composition have important effects on the macro-physical properties of sludge. In this study, the response of EPS in sludge to temperature (−40–200 °C) was systematically investigated using XAD resin fractionation, variable-temperature infrared spectra (VTIS) and two-dimensional correlation spectroscopy (2D-COS). The relationships between the molecular structure of EPS and the macro-physical properties (rheological property and dewatering performance) of waste activated sludge (WAS) at varying temperature were also established. During the freezing treatment, the solubilization of biopolymers and destruction of the hydrophilic functional groups (hydroxy, amino and carboxyl) resulted in the production of small organic matters, which enhanced EPS hydrophobicity and reduced electrostatic repulsion of sludge, and subsequent dewaterability improvement. For the hydrothermal treatment, the EPS transformation showed a two-stages reaction including stage I (70–120 °C) and stage II (>120 °C). Stage I (70–120 °C), a plenty of hydrophilic functional groups (hydroxy, amino and carboxyl) in EPS were exposed via the solubilization of biopolymers, which enhanced electrostatic repulsion of sludge and EPS hydrophilicity, and subsequence in deterioration of sludge dewaterability and fluidity. However, at stage II (>120 °C), the high temperature caused hydrolyzation of macromolecular organic matters in completely, in which the secondary structure of the protein was destroyed, causing the peptide chain to unfold. In addition, the reduction of α-helix and β-sheet content and intensified Maillard reaction decreased electrostatic repulsion of sludge, thus resulted in the improvement of sludge dewaterability and fluidity. This study enriched the theoretical basis of the optimal control of sludge treatment based on temperature regulation.

Seasonal Speciation Study of Heavy Metals Content in Well Water of Some Chicken Farms in Osun State, Southwestern Nigeria

Heavy metals are native to various soils, dusts, air, sediments, water and plant constituent in various means and these relations quantify their mobility and availability. In this manuscript, the seasonal differences in contents of arsenic, cadmium, copper, iron, lead and zinc in well water within the proximity of three main chicken farms in Osun State, were studied to ascertain the ecological impacts of the chicken farming on the well water sources. Water samples taken for eight months were assayed for pH, conductivity, total dissolved solids, alkalinity and speciation of heavy metal contents utilizing standard techniques. A column filled up with Amberlite XAD-16 resin was utilized for the quantification of metals bound to humic substances and free metal ions in the water samples. The samples were assayed for their heavy metal content utilizing Flame Atomic Absorption Spectrophotometer. Quality assurance techniques involved blank determination, recovery analysis and calibration of standards. Descriptive and inferential statistics were used for data interpretations. The content ranges of the metals were: 0.0110–0.0878, 0.0130–0.0900, 0.1124–0.5196, 17.0563-59.4264, 0.021-0.2283 and 3.0420–21.1450 µg/mL for As, Cd, Cu, Fe, Pb and Zn, respectively. With the exception of Cu, the content ranges of all the other metals were present to be exceeded the international standards and acceptable level for drinkable water. The speciation analyzes signified that Fe and Zn were present primarily in the particulate phase, As and Cu were predominant in the humic substances phase, while Cd, Fe, Pb and Zn mainly found in the free metal ions. The free metal ions phase of Cd, Fe, Pb and Zn were found to be bio-available, and thus, could present health risks to humans and poultry bird. The contents found from the control site signified that the chicken farm activities might have impacted the well water with high heavy metal burdens.

First usage of ostracod species (Herpetocypris brevicaudata) carapace as a biosorbent with XAD-4 resin to determine Co(II), Cu(II) and Mn(II) trace metal ions

Powdered ostracod carapace of the species (Herpetocypris brevicaudata), an invertebrate aquatic crustacean, loaded on Amberlite XAD-4 resin, were tested as a biosorbent to determine concentrations of trace metal ions (Cu(II), Co(II), Mn(II)) in water samples prior to UV–VIS spectrophotometric analyses. Effects of sample pH, volume, type and volume of eluent, matrix interference, and flow rate of sample and eluent were examined to investigate optimum biosorption conditions of the trace metal ions.Optimum pH values for Cu(II), Co(II) and Mn(II) were around 10.0. Metals were desorbed with 1 M HCl (recovery, 90–100% and high precision; SD < 5%). Sorption capacity of AXAD-4 resin loaded with H. brevicaudata was 0.71, 0.23 and 0.64 mmol g−1 for Cu(II), Co(II) and Mn(II), respectively.Performances of the new sorbent were evaluated using certified reference material (TMDA-70.2 Ontario Lake Water).

Multicriteria Optimization of Phenolic Compounds Capture from a Sunflower Protein Isolate Production Process by-Product by Adsorption Column and Assessment of Their Antioxidant and Anti-Inflammatory Effects.

The aim of this study was to valorize liquid effluent from the sunflower protein isolate process by extracting phenolic compounds it contains. To do so, XAD7 resin was used. A multicriteria optimization methodology based on design of experiments showed the optimal conditions were adsorption flow rate of 15 BV/h at pH 2.7, a desorption flow rate at 120 BV/h with ethanol/water 50% (v/v). The best trade-off between purity and recovery yields resulted in the production of a fraction containing 76.05% of chlorogenic acid (CGA) whose biological properties were evaluated. DPPH and ABTS tests showed that this fraction had a higher radical scavenging capacity than vitamin C. In vitro assays have shown that this fraction, when used at a concentration corresponding to 50 or 100 µM of CGA, does not present any cytotoxicity on human THP-1 cells differentiated into macrophages. In addition, this fraction when added prior to the inflammatory stimulus (LPS) can reduce tumor necrosis factor-alpha (TNF-α) production by 22%, thereby highlighting its protective properties against future inflammation.

Development of a New Passive Sampling Method for the Measurement of Atmospheric Linear and Cyclic Volatile Methyl Siloxanes.

A new passive sampling method was developed and characterized to measure atmospheric volatile methyl siloxanes (VMS). The infrastructure of a commercial passive air sampler (PAS) was used along with XAD-2 resin as the adsorbent. Experimental sampling rates (SR) determined using collocated active and passive samplers ranged between 0.0363 (L5) and 0.0561 (D3) m3/day and agreed well with the theoretical ones. VMS uptake was highly linear for eight weeks. The precision of the method was very good (<10%). Compared to the other PASs used for VMS, the new method has several advantages (i.e., the sampler is much smaller, it has commercially available components, and the solvent requirement, equipment needed for extraction, and steps for sample preparation are minimal) while achieving similar or lower method detection limits. The developed method was applied to investigate the spatial distribution and possible sources of atmospheric VMS in the Izmir region. Field sampling covered 42 sites representing different source and land use areas. ΣVMS concentrations ranged between 41.4 and 981 ng/m3. The dominant VMS was D5 followed by D3 and D4. Spatial distributions indicated that the main VMS sources in the area were urban areas, wastewater treatment plants, and landfills where the VMS-containing products are used and disposed.

Identification of the Antidepressant Function of the Edible Mushroom Pleurotus eryngii.

Pleurotus eryngii produces various functional molecules that mediate physiological functions in humans. Recently, we observed that P. eryngii produces molecules that have antidepressant functions. An ethanol extract of the fruiting body of P. eryngii was obtained, and the extract was purified by XAD-16 resin using an open column system. The ethanol eluate was separated by HPLC, and the fraction with an antidepressant function was identified. Using LC-MS, the molecular structure of the HPLC fraction with antidepressant function was identified as that of tryptamine, a functional molecule that is a tryptophan derivative. The antidepressant effect was identified from the ethanol extract, XAD-16 column eluate, and HPLC fraction by a serotonin receptor binding assay and a cell-based binding assay. Furthermore, a forced swimming test (FST) showed that the mice treated with purified fractions of P. eryngii exhibited decreased immobility time compared with nontreated mice. From these results, we suggest that the extract of P. eryngii has an antidepressant function and that it may be employed as an antidepressant health supplement.

Optimizing Micropollutant Removal by Ozonation; Interference of Effluent Organic Matter Fractions

ABSTRACT Ozonation for micropollutant removal from wastewater treatment plant effluent is energy and cost-intensive because of competition between background organic matter and micropollutants. This study aims to elucidate the interference of different organic matter fractions during the ozonation of micropollutants. Wastewater treatment plant effluent was fractionated using membranes and XAD-8 resin. All membrane and resin fractions were spiked with 18 micropollutants (2 µg/L) and ozonated with 0.25, 0.5 and 1 g O3/g TOC. Results show that these fractions differ in their interference with the ozonation of micropollutants. Interference was lower in the smallest size fraction (<1 kDa) than in all other fractions for micropollutants with low and medium ozone reactivity. The hydrophobic neutrals and hydrophilics resin factions showed a high interference for ozonation of micropollutants with medium and high ozone reactivity, respectively. The four parameters that were analyzed (specific UV absorbance at 254 nm, fluorescence, chemical oxygen demand and nitrite) could not elucidate the differences in micropollutant removal. Still, we conclude that understanding the type of organic matter present in the matrix, is essential to optimize micropollutant ozonation and other tertiary micropollutant removal treatments.

An experimental investigation of the acquisition of Nd by authigenic phases of marine sediments

The neodymium isotope composition (ɛNd) of authigenic phases in marine sediment is widely used to reconstruct the origin and mixing of water masses of overlying seawater through time. However, at some locations in the modern ocean, the ɛNd of authigenic phases in surface sediment is not consistent with that of local seawater, raising concerns about its current interpretation as a paleotracer of water masses. To further investigate this question, we conducted a laboratory-based incubation experiment with a Mn-oxide phase placed at the sediment–water interface of multicores to assess the extent to which the authigenic phase records seawater ɛNd.Multicores were collected from the Strait of Georgia (SoG), which is a relatively deep coastal waterway with high sedimentation rates, oxygenated surface sediments, and active macrofauna, separating the mainland coast of British Columbia and Vancouver Island. Manganese oxide-coated XAD resin beads were placed at the sediment surface and the cores were incubated for 6 months in a tank filled with SoG seawater spiked with 150Nd. While the ɛNd of the Mn-oxide coated resin (−4.0) was similar to that of SoG seawater used for the incubation (−3.7), the 150Nd/144Nd of the Mn-oxide phase measured after the incubation indicates that, under our experimental conditions, a minimum of 83% of the Nd associated with the Mn-oxide phase is not sourced from seawater, but from pore water. The 150Nd/144Nd ratio of the Mn-oxide resin is necessary to determine the predominant source of Nd to the resin because the ɛNd of SoG pore water (−3.9) is within analytical error of seawater (−3.7). Using field data and constraints from the Nd mass balance during the incubation, we conclude that the similarity of ɛNd in pore water and seawater in the SoG is fortuitous and not a result of a top-down or bottom-up control. Although the setting of our sediments is not directly comparable to open ocean locations, this study raises concerns about the use of ɛNd in paleocirculation studies, and points to the necessity of elucidating the factors controlling local lithogenic dissolution in pore waters as a prerequisite for the correct interpretation of ɛNd in the authigenic phases of marine sediments.

Purification and characterization of a novel bacteriocin from Lactobacillus paracasei ZFM54

Bacteriocins from lactic acid bacteria (LAB) arouse general concern in recent years due to their antimicrobial activities against foodborne pathogenic microorganisms. In this study, a novel bacteriocin named as bacteriocin ZFM54, produced by Lactobacillus paracasei ZFM54 isolated from the feces of newborn infant, was purified by a four-step strategy including macroporous resin XAD-16 adsorption chromatography, cation exchange chromatography, Sephadex G-25 gel filtration chromatography, and reverse-phase high-performance liquid chromatography (RP-HPLC). The molecular weight of bacteriocin ZFM54 was 1143.39 Da, the predicted amino acid sequence was ATTLIPPVFGK. Bacteriocin ZFM54 was highly thermostable, active under the acidic condition, sensitive to trypsin and proteinase K, while insensitive to α-amylase, lysozyme, lipase, and ribonuclease A. The bacteriocin possessed a broad-spectrum inhibition against many foodborne pathogens such as Salmonella typhimurium, Micrococcus luteus and Listeria monocytogenes. The mode of action of bacteriocin ZFM54 was related to the pore formation of cell membrane. We further demonstrated that Lipid II, the molecular target of the prototype lantibiotic Nisin, was not the specific target of this bacteriocin. Together, this new bacteriocin has great potential to be used as a biological preservative in the food industry.

Adsorption of volatile benzene series compounds by surface-modified glass fibers: kinetics, thermodynamic adsorption efficiencies, and mechanisms.

The presence of volatile benzene series compounds (VBSCs) in the environment is continually increasing, with the potential for negative effects on human health. It is therefore important to develop new materials for the adsorption of these compounds using various modification techniques. Glass fibers are a promising adsorbent for VBSCs and offer a number of advantages. In the present work, the surfaces of glass fibers were modified using hydrogen peroxide, a sodium hydroxide solution, or Piranha solution (a mixture of concentrated sulfuric acid and hydrogen peroxide). The adsorption characteristics of the resulting specimens were investigated, employing 10 volatile benzene-based compounds, and the activated glass fibers showed significantly improved adsorption efficiencies. The fibers activated with the Piranha solution were further modified with a triethoxysilyl benzene compound to obtain an aryl-modified material that demonstrated enhanced adsorption of aniline, salicylaldehyde, benzyl alcohol, and xylene relative to that obtained from a combination of polyurethane foam and XAD-2 resin. The adsorption efficiency of benzyl alcohol by these aryl glass fibers was found to be as high as 93% and the adsorption mechanism is believed to be associated with hydrogen bonding and π-π conjugation. This study provides a reliable technique for the quantification of VBSCs and a basis for the evaluation of various adsorption materials.

Generation of a pH-blind/pH-sensitive alternating surface on a hydrophobic resin by mussel-inspired chemistry and investigating the effect of surface modification on the adsorption dynamics of some anionic colorants

The effect of a surface modification process known as "mussel-inspired modification" on the adsorption dynamics of hydrophobic adsorbent, namely XAD1180, was studied based on equilibrium adsorption data. In the study, three anionic colorants (i.e., Sunset yellow, SY; Allura red, AR; and Tartrazine, TZ) were used as the model compounds. The role of some experimental parameters, such as pH (4–7), ionic strength (0.01–0.50 mM) and colorant concentration (25–125 mg/L), were investigated to determine optimal conditions leading to the highest adsorption. Equilibrium adsorption data were obtained under optimal conditions by stepwise frontal analysis method (SFA) and modeled on the basis of some common adsorption isotherm models (i.e., Langmuir and Freundlich). The adsorption dynamics of the XAD1180 resin have been found to vary significantly after PD coating. After the PD coating process, it was found that the highly hydrophobic background material, XAD1180, gained a pH-sensitive character, thereby replacing a sharp decrease in the adsorption capacity at pH = 5.0–7.0 with an increase in pH = 4.0. Another dramatic effect of the PD coating was observed with Langmuir monolayer adsorption capacities, so that the PD layer was found to increase the monolayer saturation capacity of the XAD1180 (from 8.0 to 17 µmol/g for SY, from 7.7 to 9.9 µmol/g for AR, and from 5.3 to 9.1 µmol/g for TZ). It was also deduced from the Freundlich isotherm parameter, KF, that there was, in general, a clear increment in the overall effect of adsorption capacity and the average affinity after mussel-inspired surface modification process.

LACCASE ISOLATION FROM SPENT MUSHROOM WASTE (AGARICUS BISPORUS): PARTIAL PURIFICATION, CHARACTERIZATION, IMMOBILIZATION AND BIOTECHNOLOGICAL APPLICATION

Laccase was partially purified from mushroom compost with cheap and simple purification methods. Partially purified laccase was immobilized onto Amberlite XAD-7 resin. Immobilization conditions and textile dye (Direct Green B) decolorization of immobilized enzyme were examined. Laccase was partially purified from mushroom compost with 3.22 purification fold. Immobilization time for laccase was 30 minutes with 97% efficiency. The immobilization yield based on the activity was calculated by about 90%. The immobilization yield was calculated as nearly 95% based on the measurement of protein amount at each stage. Immobilized enzyme preserved its initial activity with an 84% rate even after its tenth use. The free enzyme lost its activity immediately when it was incubated with the dye solution under its optimal conditions (pH 3.0 and 65°C). On the contrary, the immobilized enzyme maintained its initial activity with a 53% rate when incubated with dye solution under its optimal conditions (pH 3.5 and 65°C).

Site formation process and megamammal bone radiocarbon dates in Campo Laborde (Pampas of Argentina): Contribution towards a research methodology

Dating bone collagen has been problematic in the Argentinean Pampas. Many bone samples do not have collagen or have poor preservation giving collagen of questionably quality, in many cases it is contaminated by humic substances. The combination of these factors has produced suspicious results, leading to the proposition of the Holocene survival in the region of the extinct Pleistocene megamammals such as the Megatherium Holocene ages from the Campo Laborde site. However, new dates from the same sample, purified from humates with XAD-2 resin, gave results of ~10,650 14C years BP. In this article, we apply different methodological procedures (chemical, geoarchaeological and taphonomic analysis) in order to reconstruct the formation at the Campo Laborde the site and identify the processes and agents that affected its chronology. The previously obtained Early Holocene ages of megafauna bones resulted from the interrelation of various factors as physical and chemical weathering, humification processes linked to pedogenesis, and diagenetic processes. In sum, they caused the degradation of collagen and the subsequent contamination by fulvic acids from the overlaying soil, which classic pretreatment techniques could not remove. We conclude that the obtained results do not support the Holocene survival of the megafauna in the Pampas.