Solid Ammonium Sulfate Research Articles

Non-evaporative solid phase ammonium sulfate separation from ammonia-stripped sulfuric acid solution by solvent-driven fractional crystallization

Manifold ammonia separation and recovery processes, such as adsorption, ion exchange, air stripping, membrane stripping, and electrochemical stripping, have been developed to harvest ammonia from waste streams. The separated ammonia was mostly stored in sulfuric acid as aqueous ammonium sulfate, an excellent fertilizer supplying nitrogen and sulfur. This aqueous phase of the ammonium sulfate, however, hindered the direct application of the recovered ammonia, due to low purity and large volume. Evaporative crystallization had been employed to promote its value, but its comprehensive obstacles include high operating costs, slow reaction kinetics, and low-purity end-products. We herein employed solvent-driven fractional crystallization (SDFC), also known as antisolvent crystallization, to crystallize recovered ammonia as sulfate salt (i.e., (NH4)2SO4) from the model ammonia-stripped sulfuric acid solution using methanol, ethanol, and acetone without energy-intensive evaporation. At 20 °C, the SDFC technique represented rapid crystallization, which reached equilibrium within only 5 min, and over 80 % of crystallization efficiency when 4-fold of the organic solvents were added. SDFC exclusively produced ammonium sulfate under various ammonium-to-sulfate molar ratios (ASR), whereas the evaporative crystallization produced a substantial amount of an unfavorable product, letovicite (i.e., (NH4)3H(SO4)2) at a low ASR. These features highlight the promise of SDFC as an alternative to the conventional evaporative crystallization. This study demonstrates the SDFC technique to improve the purity and usability of recovered ammonia in an acid stripping solution, thereby improving the potential of existing ammonia recovery technologies and their applicability in the environmental industry.

Nutrient recovery and valorisation from pig slurry liquid fraction with membrane technologies

Livestock slurry has been reported to be a potential secondary raw material as it contains macronutrients ‑nitrogen, phosphorus and potassium-, which could be valorised as high-quality fertilizers if proper separation and concentration of valuable compounds is performed. In this work, pig slurry liquid fraction was assessed for nutrient recovery and valorisation as fertilizer. Some indicators were used to evaluate the performance of proposed train of technologies within the framework of circular economy. As ammonium and potassium species are highly soluble at the whole pH range, a study based on phosphate speciation at pH from 4 to 8 was assessed to improve the macronutrients recovery from the slurry, resulting in two different treatment trains at acidic and alkaline conditions. The acidic treatment system based on centrifugation, microfiltration and forward osmosis was applied to obtain a nutrient-rich liquid organic fertilizer containing 1.3 % N, 1.3 % P2O5 and 1.5 % K2O. The alkaline path of valorisation was composed by centrifugation and stripping by using membrane contactors to produce an organic solid fertilizer −7.7 % N, 8,0 % P2O5 and 2.3 % K2O-, ammonium sulphate solution −1.4 % N- and irrigation water. In terms of circularity indicators, 45.8 % of the initial water content and <50 % of contained nutrients were recovered - 28.3 % N, 43.5 % P2O5 and 46.6 % K2O - in the acidic treatment resulting in 68.68 g fertilizer per kg of treated slurry. 75.1 % of water was recovered as irrigation water and 80.6 % N, 99.9 % P2O5, 83.4 % K2O was valorised in the alkaline treatment, as 219.60 g fertilizer per kg of treated slurry. Treatment paths at acidic and alkaline conditions yield promising results for nutrients recovery and valorisation as the obtained products (nutrient rich organic fertilizer, solid soil amendment and ammonium sulphate solution) fulfil the European Regulation for fertilizers to be potentially used in crop fields.

Production and biochemical characterization of partially purified cellulase-free, thermo-acidophilic endoxylanase from Lysinibacillus fusiformis strain TB7 using kolanut husk as feedstock

Xylanases have become very important enzymes in many industrial processes for the valorization of xylan-rich lignocellulosic wastes. Here, some physicochemical and kinetic properties of a purified endoxylanase produced on kolanut husk-based medium by Lysinibacillus fusiformis are presented. The crude enzyme solution was first subjected to precipitation with solid ammonium sulphate and further purified on DEAE-Sephadex A-50 anion-exchange and Sephadex G-100 gel filtration columns chromatography prior to biochemical characterization. The purified endoxylanase was 21 kDa as determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and was thermostable, exhibiting optimum activity at 60 °C and pH 5.0. The Km and Vmax were respectively estimated to be 29.5 mg/ml and 125 μmol/min/ml using Birchwood xylan as substrate. Activity of the enzyme was enhanced by Na+, Ca2+, Mn2+, Mg2+ and K+ at concentration of 5 mM but inhibited by Hg2+, Cu2+, Pb2+, Fe3+, EDTA, SDS and Urea. The purified endoxylanase showed high hydrolytic activity on Birchwood xylan and kolanut husk but extremely poor or no activity on carboxymethyl cellulose, starch or pectin. This L. fusiformis strain TB7 endoxylanase has desirable properties useful for biotechnological applications in laundry, fuels, feeds, paper and pulp industries.

Economic optimization of hollow fiber membrane contactors for ammonia nitrogen recovery from anaerobic digestion effluents

This study presents the optimization and economic analysis of the membrane contactors to recover ammonia nitrogen from anaerobic effluents. The effects of ammonia nitrogen concentrations and alkalinity of the anaerobic effluents on the operating cost and total recovery cost were investigated, and the optimization of wastewater flowrate and pH was carried out.The sensitivity analysis revealed that the wastewater pH was the dominant parameter of the operating cost, followed by the percentage Am-n recovery and wastewater flowrate. The increase of anaerobic effluent’s alkalinity reduced the optimized wastewater pH and flow rate. The total operating recovery cost, including the production cost of solid ammonium sulfate, was found to be in the range of 0.16–0.31 USD/ kg·ammonium sulfate for the Am-n and alkalinity concentrations of 100–700 mg/L and 400–2800 mg/L as CaCO3, respectively, which are much lower than those of the conventional vacuum thermal stripping/acid absorption technique. The total costs, considering the capital investment of the membrane contactor’s unit, were also determined, and found to be 0.242–0.741 USD/kg·ammonium sulfate in the investigated range of anaerobic effluents

Valorization of bio-fertilizer from anaerobic digestate through ammonia stripping process: A practical and sustainable approach towards circular economy

Anaerobic digestion is a technology, which converts biological wastes into biogas and biogas digestates (DIG); the latter is considered the main challenge for biogas producers. Recently, nutrient recovery technology from these DIG for bio-fertilizers production as an alternative for traditional chemical fertilizers is receiving increasing attention. This study aims to use two different biofertilizers based on DIG using ammonia striping technique which are liquid bio-based ammonium sulfate (BAS-L) and solid bio-based ammonium sulfate (BAS-S) fertilizers, besides the raw DIG and the conventional urea compound fertilizer (UCF) is used as a chemical fertilizer for comparison to produce solanaceous plants (eggplant). The agronomic effectiveness and economics of using these fertilizers are listed, and the results indicated that the eggplant yields using UCF and BAS-L were 62.65 tons/ha and 63.42 tons/ha, respectively, representing 24.5 % and 27.9 % higher than BAS-S and DIG, respectively. The agronomic efficiency (AEN) and the apparent recovery efficiency (AREN) of BAS-L fertilizer were the highest, reaching 44.8 kg DM/kg N and 7.9 %, respectively, which were significantly higher than the corresponding values of BAS-S and DIG. Furthermore, the economic benefits of various fertilizer applications were estimated and compared. The results showed that the theoretical net revenue of BAS-L fertilizer was 86065.03 $/ha, while BAS-S fertilizer and UCF were lower than BAS-L (56.7 % and 48.5 %, respectively), and the theoretical net revenue of direct application of DIG was 36958.95 $/ha. Therefore, BAS-L fertilizer has the best comprehensive fertilizer effect and economic benefits.

Solid organic-coated ammonium sulfate particles at high relative humidity in the summertime Arctic atmosphere

SignificancePhysical and chemical properties of individual atmospheric particles determine their climate impacts. Hygroscopic inorganic salt particles mixed with trace amounts of organic material are predicted to be liquid under typical tropospheric conditions in the summertime Arctic. Yet, we unexpectedly observed a significant concentration of solid particles composed of ammonium sulfate with an organic coating under conditions of high relative humidity and low temperature. These particle properties are consistent with marine biogenic-derived new particle formation and growth, with particle collision hypothesized to result in the solid phase. This particle source is predicted to have increasing relevance in the context of declining Arctic sea ice and increasing open water, with impacts on clouds, and therefore climate.

Isolation, partial purification and immobilization of locally sourced tyrosinase on different fiber materials

Tyrosinase has diverse functions in biological systems including melanin synthesis for defense against harmful effects of ultraviolet light. It oxidizes tyrosine especiallyL-3, 4-dihydroxyphenylalanineto L-Dopaquinone. The objective is to isolate, partially purify and immobilize tyrosinase on coconut fiber and palm wood chips using gum Arabic as binder. Yam (Dioscorea rotundata) was used as source of tyrosinase. It was extracted by mashing yam with potassium phosphate buffer (PH 7). The slurry was centrifuged, supernatant decanted and mixed with solid ammonium sulphate [(NH4)2SO4] for partial purification of the enzyme. Its kinetic parameters were determined spectrophotometrically by measuring its activity at varying concentrations of substrate (L-DOPA). Line weaver-bulk double reciprocal plot was plotted to derive Michealis-Menten constant (Km) and maximum velocity (Vmax) while the optimum temperature and PH was determined by varying temperature and PH ranges (5.5-8.5) of reaction system. The immobilized tyrosinase activitywas compared with that of partially purified enzyme. Results showed that, crude enzyme activity was 7.2 micromoles/min, immobilized enzymes activity on coconut fiber was7.7micromoles/min and that on palm wood chip was 11.1micromoles/min. Km and Vmax of partially purified tyrosinase was 33.3mM and 0.016S-1, that of immobilized enzyme on coconut fiber was 28.5mM and 0.020s-1 while that on palm wood chips was 20.8mM and 0.033s-1 respectively. Optimum PH and temperature for partially purified and immobilized enzymes was 6.5 and 550C. Immobilization of yam tyrosinase on palm wood chips increased the activity of partially purified enzyme by 15%. Conclusively, palm wood chip is considered a better support to coconut fiber for immobilization of yam tyrosinase.

Cold Steeping Infusion, a Novel Lectin Extraction Technique for the Isolation, Purification and Partial Characterization of Lectins from the Green Venezuelan Marine Alga Caulerpa serrulata

A lectin from the green Venezuelan marine alga Caulerpa serrulata was extracted with phosphate buffered saline (PBS) using cold steeping infusion (CSI) and by grinding with liquid nitrogen (GLN). The proteins were precipitated using solid ammonium sulfate. Both the crude extracts and ammonium sulfate precipitated proteins were tested for hemagglutinins using native and papain-treated human red blood cell suspensions in isotonic saline solution. Purification of lectins was achieved using affinity chromatography-sugar-epoxy-sepharose 6B and molecular weight was assessed by size exclusion chromatography using Bio-gel® P-100 and SDS-PAGE with 2-mercaptoethanol. IEF-urea 8M was also evaluated. Using CSI it was shown that the marine alga released hemagglutinating compounds into the solutions; the same hemagglutinating compounds were also obtained by GLN. Ammonium sulfate precipitated proteins exhibited agglutinating activity against native and papain-treated human red blood cells. Temperature and EDTA were shown to affect dramatically the lectin activity towards red blood cells. A lectin was purified efficiently and the molecular weight calculated as approximately 78,000 Daltons. The CSI technique demonstrated that the alga could be returned to an active metabolic state by immersion in a simple buffer after having been kept dormant by freezing at −20°C for long periods. It was also shown that the alga was releasing bioactive compounds into the solutions and, therefore, this procedure is being suggested as a good, gentle, non-disruptive extraction technique and we postulate CSI as a possible bioreactor for the continuous production of bioactive compounds from green marine algae.

Selective Uptake of Third-Hand Tobacco Smoke Components to Inorganic and Organic Aerosol Particles.

Third-hand smoke (THS) is an emerging route of exposure to tobacco smoke in the indoor environment. Few studies have investigated the chemical behavior of THS, although initial findings suggest that semivolatile components of THS can partition to indoor aerosol. By exposing single-component particles to THS in an environmental chamber, this study demonstrates a pronounced dependence of THS uptake on aerosol composition. First, it was found that primarily reduced nitrogen compounds (that produced C xH yN z+ ion signal) in THS partitioned strongly to acidic ammoniated sulfate particles, whereas overall THS uptake to more pH-neutral sodium sulfate particles was minimal. Second, THS uptake to pure hydrocarbon particles (squalane) was even greater than to ammoniated sulfate particles with the uptake arising from mainly C xH y compounds. The greater uptake of THS to squalane was mostly driven by the dominant fraction of C xH y compounds in the side stream cigarette smoke aerosol, the composition of which is likely to be broadly similar to THS in these experiments. Third, oxygenated organic particles (sucrose) and solid ammonium sulfate particles showed minimal uptake. These results indicate that particulate THS inhalation exposure will be strongly dependent on the chemical nature of the particles present in the indoor environment.

Peptides extracted from edible mushroom: Lentinus squarrosulus induces apoptosis in human lung cancer cells

Context: Lentinus squarrosulus Mont. (Polyporaceae) is an interesting source of diverse bioactive compounds. Objective: This is the first study of the anticancer activity and underlying mechanism of peptides extracted from Lentinus squarrosuls. Materials and methods: Peptides were isolated from the aqueous extract of L. squarrosulus by employing solid ammonium sulphate precipitation. They were further purified by ion-exchange chromatography on diethylaminoethanol (DEAE)-cellulose and gel filtration chromatography on Sephadex G25. Anticancer activity was investigated in human lung cancer H460, H292 and H23 cells cultured with 0–40 μg/mL of peptide extracts for 24 h. Cell viability and mode of cell death were evaluated by MTT and nuclear staining assay, respectively. Western blotting was used to investigate the alteration of apoptosis-regulating proteins in lung cancer cells treated with peptide extracts (0–20 μg/mL) for 24 h. Results: The cytotoxicity of partially-purified peptide extracts from L. squarrosulus was indicated with IC50 of ∼26.84 ± 2.84, 2.80 ± 2.14 and 18.84 ± 0.30 μg/mL in lung cancer H460, H292 and H23 cells, respectively. The extracts at 20 μg/mL induced apoptosis through the reduction of anti-apoptotic Bcl-2 protein (∼0.5-fold reduction) and up-regulation of BAX (∼4.5-fold induction), a pro-apoptotic protein. Furthermore, L. squarrosulus peptide extracts (20 μg/mL) also decreased the cellular level of death receptor inhibitor c-FLIP (∼0.6-fold reduction). Conclusions and discussion: This study provides the novel anticancer activity and mechanism of L. squarrosulus peptide extracts, which encourage further investigation and development of the extracts for anticancer use.

Improved determination of uracil and dihydrouracil in plasma after a loading oral dose of uracil using high-performance liquid chromatography with photodiode array detection and porous graphitic carbon stationary phase

ObjectivesThe aim of this study was to develop and validate a high-performance liquid chromatographic method for the measurement of plasma concentrations of uracil and dihydrouracil after administration of an oral loading dose of uracil in the context of evaluation of DPD enzyme activity. Design and methodsAnalytes were extracted from 500μL plasma sampler with a mixture of ethyl acetate isopropanol (85:15, v/v) after protein precipitation with solid ammonium sulfate. The extract was inject in the porous graphitic carbon stationary phase, eluted with water and acetonitrile in gradient mode, allowing complete separation of uracil, dihydrouracil and the internal standard (5-fluorouracil). Chromatograms were monitored at 210 and 260nm. ResultsTotal chromatographic run time, including reequilibration, was 30min. The assay was linear in the concentration range of 0.2 to 20μgmL−1. Accuracy was 98.4–105.3%, intra-assay precision was 5.1–12.1% and between-assay precision was of 5.3–10.1%. Analytes were stable in plasma at room temperature up to 6h and for three freeze and thaw cycles. Processed samples are stable up to 12h. ConclusionsThe developed method was fully validated and has significantly reduced running time when compared to previous assay using porous graphitic stationary phase, allowing complete resolution of uracil, dihydrouracil and internal standard. This assay might be suitable to investigate the eventual correlation between concentrations of uracil and dihydrouracil in plasma after an oral loading dose and DPD enzyme activity, with potential contribution to therapeutic drug monitoring.

Modification of Silica Rice Husk Ash to Solid Ammonium Sulphate for Second Generation Biofuels Productions

A new approach has been demonstrated for the synthesis of solid ammonium sulphate attached to silica rice husk ash. The 3-(aminopropyl)triethoxysilane was immobilized onto silica at room temperature to functionalize the silica with ammine end groups (–NH2). The amine group was sulphated with sulphuric acid to produce a novel micro-rod-like shaped acidic catalyst (as seen with TEM) designated RHNH3SO4H (RH = rice husk). The TGA analysis shows that the catalyst is stable at temperatures below 200°C. The acidity measurement of the catalyst indicates that it has Brønsted acid sites. Cellulose extracted from waste of rice husk and cellulose extracted from office paper were hydrolysed to glucose in 6 h, and the glucose was hydrolysed afterwards to other products within 13 h. The catalyst is reusable many times without a significant loss of catalytic activity.

BUL: a novel lectin from Bauhinia ungulata L. seeds with fungistatic and antiproliferative activities

A new galactose-binding lectin, termed BUL, has been purified from seeds of Bauhinia ungulata (Caesalpinoideae) by precipitation with solid ammonium sulfate followed by agarose-lactose affinity chromatography. B. ungulata lectin strongly agglutinated rabbit erythrocytes, both native and treated with proteolytic enzymes, and was inhibited by D-galactose and D-galactose-derived sugars, especially N-acetyl-D-galactosamine. BUL was shown to be a stable glycoprotein, maintaining its hemagglutinating activity after incubation at wide ranges of temperature and pH, but not after incubation with EDTA. By SDS-PAGE analysis under reduced conditions, purified BUL showed an electrophoretic profile consisting of a single band with apparent molecular mass of 30 kDa. BUL showed intrinsic fluorescence typical of folded globular proteins, and circular dichroism spectra of lectin in the native state showed a predominance of β-sheet secondary structure. The N-terminal amino acid sequence of 19 residues showed a high sequential similarity to other galactose-specific lectins from the Bauhinia genus. In addition, BUL showed antifungal activity against phytopathogenic species and showed in vitro antiproliferative activity against the HT-29 cell line of human colon adenocarcinoma in a dose-dependent manner.

Comparison of the Exopeptidase Activity of Fractions from Crude Extracts of Octopus Octopus vulgaris Cuvier Hepatopancreas Using Different Fractionation Methods

This study was performed to identify the optimum fractionation method and conditions to obtain exopeptidase-active fractions from octopus hepatopancreas (HP) crude extracts (CEs) using four techniques: solid ammonium sulfate fractionation, polyethylene glycol (PEG) fractionation, anion exchange chromatography, and gel filtration chromatography. The fractions with the highest total activity toward L-leucine-p-nitroanilide (Leu-pNA) were fraction IV from the ammonium sulfate and PEG fractionation, and fraction II in ion exchange and gel filtration chromatography. The total exoprotease activity of these fractions was highest in fraction IV (4,050.20 U) of ammonium sulfate fractionation, followed by fraction II (3,600.28 U) from gel filtration chromatography, fraction IV (2,861.30 U) from PEG fractionation, and fraction II (2,576.28 U) from ion exchange chromatography. These results suggest that ammonium sulfate fractionation using 60-80% ammonium sulfate was the most efficient method for separating the exoprotease active fractions from CEs of octopus HP.

The Cysteine-rich Region of Type VII Collagen Is a Cystine Knot with a New Topology

Collagens are a group of extracellular matrix proteins with essential functions for skin integrity. Anchoring fibrils are made of type VII collagen (Col7) and link different skin layers together: the basal lamina and the underlying connective tissue. Col7 has a central collagenous domain and two noncollagenous domains located at the N and C terminus (NC1 and NC2), respectively. A cysteine-rich region of hitherto unknown function is located at the transition of the NC1 domain to the collagenous domain. A synthetic model peptide of this region was investigated by CD and NMR spectroscopy. The peptide folds into a collagen triple helix, and the cysteine residues form disulfide bridges between the different strands. The eight cystine knot topologies that are characterized by exclusively intermolecular disulfide bridges have been analyzed by molecular modeling. Two cystine knots are energetically preferred; however, all eight disulfide bridge arrangements are essentially possible. This novel cystine knot is present in type IX collagen, too. The conserved motif of the cystine knot is CX3CP. The cystine knot is N-terminal to the collagen triple helix in both collagens and therefore probably impedes unfolding of the collagen triple helix from the N terminus.

Impactor Apparatus for the Study of Particle Rebound: Relative Humidity and Capillary Forces

The effect of relative humidity (RH) on the adhesion of particles colliding with a hard surface was studied for submicron particles of liquid oleic acid, solid ammonium sulfate, and solid polystyrene latex (PSL). For this purpose, a three-arm impactor was designed and constructed. The three arms consisted of one impactor having an uncoated impaction plate (i.e., a rebound arm), one impactor having a viscous-liquid-coated impaction plate (i.e., a capture arm), and one impactor having no impaction plate (i.e., a null arm). The particle number concentrations downstream of each arm were measured by condensation particle counters (CPCs). Data were analyzed to obtain the particle rebound fraction. Use of ambient upstage pressure allowed measurements from 5 to 95% RH at the impaction plate. Particle rebound depended strongly on RH, even for non-hygroscopic PSL particles. The rebound fraction for PSL particles dropped monotonically from nearly unity at 50% RH to 0.4 at 95% RH. For ammonium sulfate, the rebound fr...

BUL: A novel lectin from Bauhinia ungulata L. seeds with fungistatic and antiproliferative activities

A new galactose-binding lectin, termed BUL, has been purified from seeds of Bauhinia ungulata L. (Caesalpinoideae) by precipitation with solid ammonium sulfate followed by agarose–lactose affinity chromatography. B. ungulata lectin strongly agglutinated rabbit erythrocytes, both native and treated with proteolytic enzymes, and was inhibited by d-galactose and d-galactose-derived sugars, especially N-acetyl-d-galactosamine. BUL was shown to be a stable glycoprotein, maintaining its hemagglutinating activity after incubation at wide ranges of temperature and pH, but not after incubation with EDTA. By SDS-PAGE analysis, purified BUL showed an electrophoretic profile consisting of a single band with apparent molecular mass of 30kDa. BUL showed intrinsic fluorescence typical of folded globular proteins, and CD spectra of lectin in the native state showed a predominance of β-sheet secondary structure. The N-terminal amino acid sequence of 19 residues showed a high sequential similarity to other galactose-specific lectins from the Bauhinia genus. In addition, BUL showed antifungal activity against phytopathogenic species and showed in vitro antiproliferative activity against the HT-29 cell line of human colon adenocarcinoma in a dose-dependent manner.

Heterogeneous ice nucleation on phase-separated organic-sulfate particles: effect of liquid vs. glassy coatings

Abstract. Atmospheric ice nucleation on aerosol particles relevant to cirrus clouds remains one of the least understood processes in the atmosphere. Upper tropospheric aerosols as well as sub-visible cirrus residues are known to be enhanced in both sulfates and organics. The hygroscopic phase transitions of organic-sulfate particles can have an impact on both the cirrus cloud formation mechanism and resulting cloud microphysical properties. In addition to deliquescence and efflorescence, organic-sulfate particles are known to undergo another phase transition known as liquid–liquid phase separation. The ice nucleation properties of particles that have undergone liquid–liquid phase separation are unknown. Here, Raman microscopy coupled with an environmental cell was used to study the low temperature deliquescence, efflorescence, and liquid–liquid phase separation behavior of 2 : 1 mixtures of organic polyols (1,2,6-hexanetriol and 1 : 1 1,2,6-hexanetriol + 2,2,6,6-tetrakis(hydroxymethyl)cyclohexanol) and ammonium sulfate from 240–265 K. Further, the ice nucleation efficiency of these organic-sulfate systems after liquid–liquid phase separation and efflorescence was investigated from 210–235 K. Raman mapping and volume-geometry analysis indicate that these particles contain solid ammonium sulfate cores fully engulfed in organic shells. For the ice nucleation experiments, we find that if the organic coatings are liquid, water vapor diffuses through the shell and ice nucleates on the ammonium sulfate core. In this case, the coatings minimally affect the ice nucleation efficiency of ammonium sulfate. In contrast, if the coatings become semi-solid or glassy, ice instead nucleates on the organic shell. Consistent with recent findings that glasses can be efficient ice nuclei, the phase-separated particles are nearly as efficient at ice nucleation as pure crystalline ammonium sulfate.

Overexpression, Purification, and Biochemical Characterization of the Esterase Est0796 from Lactobacillus plantarum WCFS1

Lactobacillus plantarum is a lactic acid bacterium that is encountered in an extensive range of foods such as fermented dairy products, meat, vegetables, and bakery products. Given the little molecular information available on the lipolytic activity of L. plantarum, the aim of this study was to clone, purify, and biochemically characterize the esterase coded by gene lp_0796 (Est0796). The esterase was cloned in pET28a and purified in two steps, using solid ammonium sulfate and His tag affinity chromatography. The molecular mass of the purified Est0796 was 28.7kDa (by SDS-PAGE) and 26.6kDa (by gel filtration chromatography), pointing to a monomeric structure. Est0796 showed maximum activity at pH 8.0 and 35°C and toward shorter acyl chain lengths (C2-C4). The activity was resistant to organic solvents and cations, suggesting that this esterase may play a role in the fermentation of food products.

Purification and primary structure determination of a galactose-specific lectin from Vatairea guianensis Aublet seeds that exhibits vasorelaxant effect

Vatairea guianensis seeds, a typical plant from the Brazilian Amazon region that belongs to the Dalbergieae tribe, possess a lectin that was isolated by precipitation with solid ammonium sulfate followed by guar gum affinity chromatography. This lectin was named VGL. The V. guianensis lectin strongly agglutinated rabbit erythrocytes and was inhibited by d-galactose and d-galactose-derived sugars, especially N-acetyl-d-galactosamine. VGL has been shown to be a stable protein, maintaining its hemagglutinating activity after incubation at a wide range of temperature and pH values and after incubation with ethylenediamine tetraacetic acid (EDTA). In a sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, the purified VGL exhibited an electrophoretic profile consisting of a major 30–32kDa double band, which is termed the alpha-chain, and two minor components of 18 and 15kDa, which are referred to as the beta- and gamma-chains, respectively. An analysis using electrospray ionization mass spectrometry also indicated that purified VGL contains a mixture of chains with molecular weights of 28,437±2, 14,952±2 and 12,332±2. The complete amino acid sequence of VGL, as determined using tandem mass spectrometry, consists of 239 amino acid residues. VGL is a glycoprotein exhibiting high similarity in primary structure to other lectins from evolutionarily related plants, such as Vatairea macrocarpa lectin and lectins belonging to the Sophoreae tribe. VGL exhibits vasorelaxant activity in contracted rat aortas, an effect that is strictly dependent on the endothelium and involves nitric oxide and the lectin domain.