Adsorptive removal of polyphenols from an alfalfa white proteins concentrate: Adsorbent screening, adsorption kinetics and equilibrium study

Enrichment of antioxidant peptide from rice protein hydrolysates via rice husk derived biochar

In this study, rice husk biochar was engineered with abundant iron ion sites to enhance the enrichment of antioxidant peptides from rice protein hydrolysates through metal-chelating interactions. The π-π interactions and metal ion chelation were identified as the primary mechanisms for the enrichment process. Through peptide sequencing, four peptides were identified: LKFL (P1: Leu-Lys-Phe-Leu), QLLF (P2: Gln-Leu-Leu-Phe), WLAYG (P3: Trp-Leu-Ala-Tyr-Gly), and HFCGG (P4: His-Phe-Cys-Gly-Gly). The vitro analysis and molecular docking revealed that peptides P1-P4 possessed remarkable scavenging ability against radicals and Fe2+ chelating ability. Notably, peptide P4 showed radical scavenging activity comparable to glutathione (GSH) against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis-3-ethylbenzthiazoline-6-sulphonate (ABTS) radicals. Cellular experiments further confirmed that peptide P4 effectively protected HepG2 cells from oxidative stress-induced damage. The modified rice husk biochar proved to be an effective means for enriching rice antioxidant peptides from protein hydrolysates.

Effect of the Total Saponins of Bupleurum chinense DC. Water Extracts Following Ultrafiltration Pretreatment on Macroporous Resin Adsorption

Macroporous resin is an efficient separation technology that plays a crucial role in the separation and purification of traditional Chinese medicine (TCM). However, the application of macroporous resins in TCM pharmaceuticals is hindered by serious fouling caused by the complex materials used in TCM. This study examines the impact of ultrafiltration (UF) membrane technology on the macroporous resin adsorption behavior of TCM extracts. In this paper, Bupleurum chinense DC. (B. chinense) water extracts were included as an example to study the effect of UF pretreatment on the macroporous resin adsorption of total saponins. The study results indicated that the adsorption of total saponins constituents from the water extracts of B. chinense on the macroporous resin followed the pseudo-second-order kinetic model and the Langmuir model. The thermodynamic parameters of adsorption, including enthalpy changes and Gibbs free energies, were negative, while entropy changes were positive. These results demonstrated that the total saponin components form a monolayer adsorption layer by spontaneous thermal adsorption on the macroporous resin, and that the adsorption rate is not determined by the rate of intraparticle diffusion. Following treatment with a UF membrane with an average molecular weight cut-off of 50 kDa, the protein, starch, pectin, tannin, and other impurities in the water extracts of B. chinense were reduced, while the total saponin content was retained at 82.32%. The adsorption kinetic model of the saponin constituents on the macroporous resin remained unchanged and was consistent with both the second-order kinetic model and the Langmuir model; the adsorption rate of the second-order kinetic model increased by 1.3 times and in the Langmuir model at 25 °C, the adsorption performance improved by 1.16 times compared to the original extracts. This study revealed that UF technology as a pretreatment method can reduce the fouling of macroporous resin by TCM extracts and improve the adsorption performance of macroporous resin.

Selective recovery of esterase from Trichoderma harzianum through adsorption: Insights on enzymatic catalysis, adsorption isotherms and kinetics

In recent years, numerous attempts have been made to develop a low-cost adsorbent for selectively recovering industrially important products from fermentation broth or complex mixtures. The current study is a novel attempt to selectively adsorb esterase from Trichoderma harzianum using cheap adsorbents like bentonite (BT), activated charcoal (AC), silicon dioxide (SiO2), and titanium dioxide (TiO2). AC had the highest esterase adsorption of 97.58% due to its larger surface area of 594.45 m3/g. SiO2 was found to have the highest selectivity over esterase, with an estimated purification fold of 7.2. Interestingly, the purification fold of 5.5 was found in the BT-extracted fermentation broth. The functional (FT-IR) and morphological analysis (SEM-EDX) were used to characterize the adsorption of esterase. Esterase adsorption on AC, SiO2, and TiO2 was well fitted by Freundlich isotherm, demonstrating multilayer adsorption of esterase. A pseudo-second-order kinetic model was developed for esterase adsorption in various adsorbents. Thermodynamic analysis revealed that adsorption is an endothermic process. AC has the lowest Gibbs free energy of -10.96 kJ/mol, which supports the spontaneous maximum adsorption of both esterase and protein. In the desorption study, the maximum recovery of esterase from TiO2 using sodium chloride was 41.34 %. Unlike other adsorbents, the AC-adsorbed esterase maintained its catalytic activity and stability, implying that it could be used as an immobilization system for commercial applications. According to the kinetic analysis, the overall rate of the reaction was controlled by reaction kinetics rather than external mass transfer resistance, as indicated by the Damkohler number.

Highly Selective Pb(II) Adsorption by DTPA-Functionalized Graphene Oxide/Carboxymethyl Cellulose Aerogel

Graphene oxide (GO) exhibits a strong adsorption capacity for the removal of heavy metal ions from liquids, making it a topic of increasing interest among researchers. However, a significant challenge persists in the preparation of graphene oxide-based adsorbents that possess both high structural stability and excellent adsorption capacity. In this paper, a green and environmentally friendly ternary composite aerogel based on graphene was successfully synthesized. The adsorption capacity of graphene oxide was enhanced through diethylenetriaminepentaacetic acid modification, while the incorporation of composite carboxymethyl cellulose improved the structural stability of the composite aerogel in liquid. The composite aerogel demonstrates robust interactions between its components and features a multiscale porous structure. Adsorption tests conducted with Pb(II) revealed that the GO/DTPA/CMC (GDC) composite aerogel exhibits a favorable adsorption capacity. The study of adsorption kinetics and isotherms indicated that the adsorption process follows the quasi-secondary adsorption model and Freundlich adsorption model, suggesting a chemical multilayer adsorption mechanism, and the maximum adsorption capacity for Pb(II) ions was 521.917 mg/g based on the quasi-quadratic kinetic model fitting. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analyses, performed before and after adsorption, confirmed that the adsorption of Pb(II) primarily occurs through chelation, complexation, proton exchange, and electrostatic interactions between ions and active sites such as hydroxyl and carboxyl groups. This study presents an innovative strategy for simultaneously enhancing the adsorption properties of graphene oxide-based composite aerogels and ensuring solution stability.

Screening of MnO2 with desired facet and its behavior in highly selective adsorption of aqueous Pb (II): Theoretical and experimental studies

In this study, Density Functional Theory (DFT) calculations and experimental methods were used to evaluate MnO₂ with 5 different facets for their selective adsorption of Pb (II) from wastewater containing Cd (II), Cu (II), Pb (II), and Zn (II). The DFT calculations were used to screen the selective adsorption capability of the facets and demonstrated that the MnO₂ (3 1 0) facet has an excellent performance in selective adsorption of Pb (II) among all facets. The validity of DFT calculations was verified by comparing with the experimental results. MnO₂ with different facets was prepared in a controlled manner and the characterizations confirmed that the lattice indices of the fabricated MnO₂ have the desired facets. Adsorption performance experiments illustrated a high adsorption capacity (320.0 mg/g) on the (3 1 0) facet MnO₂. The selectivity of adsorption of Pb (II) was 3-32 times greater than that of the other coexisting ions, i.e., Cd (II), Cu (II), and Zn (II)), which is consistent with results of the DFT calculations. Furthermore, DFT calculations of the adsorption energy, charge density difference, and projected density of states (PDOS) showed that the adsorption of Pb (II) on the MnO₂ (3 1 0) facet is non-activated chemisorption. This study shows that it is feasible to use DFT calculations to quickly screen suitable adsorbents for environmental applications.

Treatment with Supercritical CO2 Reduces Off-Flavour of White Alfalfa Protein Concentrate

White alfalfa protein concentrate from alfalfa (Medicago sativa) is a promising substitute for milk and egg protein due to its functionality. However, it contains many unwanted flavours that limits the amount that can be added to a food without affecting its taste negatively. In this paper, we have demonstrated a simple method for the extraction of white alfalfa protein concentrate followed by a treatment with supercritical CO2. Two concentrates were produced at lab scale and pilot scale, with yields of 0.012 g (lab scale) and 0.08 g (pilot scale), of protein per g of total protein introduced into the process. The solubility of the protein produced at lab scale and pilot scale was approximately 30% and 15%, respectively. By treating the protein concentrate at 220 bar and 45 °C for 75 min with supercritical CO2, off-flavours were lowered. The treatment did not decrease the digestibility or alter the functionality of white alfalfa protein concentrate when it was used to substitute egg in chocolate muffins and egg white in meringues.

Preparation of Mn/Ti-modified zeolite and its performance for removing iron and manganese

Excessive iron and manganese presented in groundwater sources may cause harm to human health that needs to be solved urgently. This research aims to develop high-performance Mn/Ti-modified zeolites using sol-gel method and hydrothermal synthesis method to remove Fe2+ and Mn2+ simultaneously. The preparation parameters were optimized by response surface methodology, and the results confirmed that the optimal preparation conditions were as follows: mass ratio of MnO2-TiO2/zeolite = 1, hydrothermal temperature = 200°C, and calcination temperature = 500°C. The results of batch adsorption experiments showed that the best removal rate of Fe2+ and Mn2+ by modified zeolite materials which was prepared under the optimum conditions reached 96.8% and 94.4%, respectively, at which the saturated adsorption capacity was 2.80 mg/g and 1.86 mg/g. Through the adsorption kinetics, thermodynamics, internal diffusion, and isothermal adsorption analyses, it is confirmed that the adsorption process of Fe2+ and Mn2+ by the modified zeolite is mainly chemical adsorption. The results of the Weber-Morris internal diffusion model prove that internal diffusion is not the only step that controls the adsorption process. In addition, combined with the characterization of the composite-modified zeolite and the adsorption experimental study, it shows that there is an autocatalytic reaction in the adsorption process.

Combination of Medium- and High-Pressure Liquid Chromatography for Isolation of L-tryptophan (Q-marker) from Medicago sativa Extract

Medicago sativa (alfalfa) is a widely used animal feed. However, its quality has been difficult to control due to the lack of appropriate marker compounds. Therefore, it is very necessary to select an appropriate quality marker (Q-marker) to control its quality. In this study, medium-pressure liquid chromatography and high-pressure liquid chromatography were employed to effectively prepare the separation of the Q-marker (L-tryptophan) from Medicago sativa. Firstly, using MCI GEL® CHP20P as the stationary phase, 2.5 g of the target fraction Fr3 was enriched from crude Medicago sativa extract (2.9 kg) by medium-pressure liquid chromatography. Secondly, Sephadex LH-20 was used to further separate Fr3 fractions, and the Fr34 fraction (358.3 mg) was enriched after 14 repetitions. Lastly, using the ReproSil-Pur C18 AQ preparative column, 63.4 mg of L-tryptophan was obtained by high-pressure liquid chromatography, and the purity was above 95%. The results showed that medium-pressure liquid chromatography (MCI GEL® CHP20P and Sephadex LH-20) combined with high-pressure liquid chromatography (ReproSil-Pur C18 AQ) could be used to effectively prepare the Q-marker from natural products with satisfactory purity.

Resource Recycling Utilization of Distillers Grains for Preparing Cationic Quaternary Ammonium—Ammonium Material and Adsorption of Acid Yellow 11

Using distillers grains (DG) as raw material after pre-treatment with sodium hydroxide (NaOH) and modified with cationic etherification agent 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHPTAC), cationic quaternary ammonium distillers grains adsorption material (CDG) was successfully prepared. The optimal adsorption conditions were an adsorption temperature of 25 °C, adsorption time of 180 min, amount of adsorbent at 8.5 g/L, initial dye concentration of 100 mg/L, and pH of dye solution 7.0. The structure of CDG was characterized by FTIR, EDS, SEM, BET, ultraviolet spectrum analysis, and analysis of the zeta potential, while the adsorption mechanism was studied by adsorption kinetics, isotherms, and thermodynamics. The results showed that CHPTAC modified the distillers grains successfully and induced the formation of CDG with a large number of pore structures and good adsorption effect. The highest adsorption yield was above 98%, while after eight rounds of adsorption–desorption experiments, the adsorption rate was 81.80%. The adsorption mechanism showed that the adsorption process of acid yellow 11 (AY11) by CDG conforms to the pseudo-second-order kinetic model, mainly with chemical and physical adsorption such as pore adsorption and electrostatic adsorption. Thermodynamics conforms to the Freundlich isothermal model, and the adsorption process is a spontaneous, endothermic and entropy-increasing process.

Biorefinery of Green Biomass─How to Extract and Evaluate High Quality Leaf Protein for Food?

There is a growing need for protein for both feed and food in order to meet future demands. It is imperative to explore and utilize novel protein sources such as protein from leafy plant material, which contains high amounts of the enzyme ribulose-1,5-biphosphate carboxylase/oxygenase (RuBisCo). Leafy crops such as grasses and legumes can in humid climate produce high protein yields in a sustainable way when compared with many traditional seed protein crops. Despite this, very little RuBisCo is utilized for foods because proteins in the leaf material has a low accessibility to monogastrics. In order to utilize the leaf protein for food purposes, the protein needs to be extracted from the fiber rich leaf matrix. This conversion of green biomass to valuable products has been labeled green biorefinery. The green biorefinery may be tailored to produce different products, but in this Review, the focus is on production of food-grade protein. The existing knowledge on the extraction, purification, and concentration of protein from green biomass is reviewed. Additionally, the quality and potential application of the leaf protein in food products and side streams from the green biorefinery will be discussed along with possible uses of side streams from the protein production.

Protein Fractionation of Green Leaves as an Underutilized Food Source-Protein Yield and the Effect of Process Parameters

Green biomass has potential as a sustainable protein source for human consumption, due to its abundance and favorable properties of its main protein, RuBisCO. Here, protein fractionation outcomes of green leafy biomass from nine crops were evaluated using a standard protocol with three major steps: juicing, thermal precipitation, and acid precipitation. Successful protein fractionation, with a freeze-dried, resolubilized white protein isolate containing RuBisCO as the final fraction, was achieved for seven of the crops, although the amount and quality of the resulting fractions differed considerably between crops. Biomass structure was negatively correlated with successful fractionation of proteins from biomass to green juice. The proteins in carrot and cabbage leaves were strongly associated with particles in the green juice, resulting in unsuccessful fractionation. Differences in thermal stability were correlated with relatedness of the biomass types, e.g., Beta vulgaris varieties showed similar performance in thermal precipitation. The optimal pH values identified for acid precipitation of soluble leaf proteins were lower than the theoretical value for RuBisCO for all biomass types, but with clear differences between biomass types. These findings reveal the challenges in using one standard fractionation protocol for production of food proteins from all types of green biomass and indicate that a general fractionation procedure where parameters are easily adjusted based on biomass type should instead be developed.

Identification and Capture of Phenolic Compounds from a Rapeseed Meal Protein Isolate Production Process By-Product by Macroporous Resin and Valorization Their Antioxidant Properties

In this study, phenolic compounds from an aqueous protein by-product from rapeseed meal (RSM) were identified by HPLC-DAD and HPLC-ESI-MS, including sinapine, sinapic acid, sinapoyl glucose, and 1,2-di-sinapoyl gentibiose. The main phenolic compound in this by-product was sinapine. We also performed acid hydrolysis to convert sinapine, and sinapic acid derivatives present in the permeate, to sinapic acid. The adsorption of phenolic compounds was investigated using five macroporous resins, including XAD4, XAD7, XAD16, XAD1180, and HP20. Among them, XAD16 showed the highest total phenolic contents adsorption capacities. The adsorption behavior of phenolic compounds was described by pseudo-second-order and Langmuir models. Moreover, thermodynamics tests demonstrated that the adsorption process of phenolic compounds was exothermic and spontaneous. The highest desorption ratio was obtained with 30% (v/v) and 70% (v/v) ethanol for sinapine and sinapic acid, respectively, with a desorption ratio of 63.19 ± 0.03% and 94.68 ± 0.013%. DPPH and ABTS tests revealed that the antioxidant activity of the hydrolyzed fraction was higher than the non-hydrolyzed fraction and higher than the one of vitamin C. Antioxidant tests demonstrated that these phenolic compounds could be used as natural antioxidants, which can be applied in the food industry.

Enhanced removal of Co(II) and Ni(II) from high-salinity aqueous solution using reductive self-assembly of three-dimensional magnetic fungal hyphal/graphene oxide nanofibers

Layer-structured graphene oxide excellent carrier for modifications; however, its poor recoverability and stability preclude its application in wastewater treatment fields. Herein, three-dimensional magnetic fungal hyphal/graphene oxide nanofibers (MFHGs) were assembled by a reductive self-assembly (RSA) strategy for the efficient capture of Co(II) and Ni(II) from high-salinity aqueous solution. The RSA strategy is inexpensive, eco-friendly and easy to scale up. The obtained MFHGs enhanced the dispersity and stability of graphene oxide and exhibited excellent magnetization and large coercivity, leading to satisfactory solid-liquid separation performance and denser sediment. The results of batch removal experiments showed that the maximum removal capacity of MFHGs for Ni(II) and Co(II) was 97.44 and 104.34 mg/g, respectively, in 2 g/L Na₂SO₄ aqueous solution with a pH of 6.0 at 323 K, and the effects of initial pH and ionic strength on Co(II) and Ni(II) removal were explored. Yield residue analysis indicated that the high porosity and oxygen-containing functional groups of MFHGs remarkably improved their Co(II)- and Ni(II)-removal capacities. According to the analysis, hydroxyl groups and amine groups participated in the chemical reaction of Co(II) and Ni(II) removal, and cation-exchange chemical adsorption was dominant during the Co(II)- and Ni(II)-removal process. Based on the attributes of MFHGs, a continuous-flow recycle reactor (CFRR) was proposed for emergency aqueous solution treatment and exhibited satisfactory removal efficiency and regeneration performance. The combination of MFHGs and the proposed CFRR is a promising water treatment strategy for rapid treatment applications.

Suppression of phosphorus release from sediment using lanthanum carbonate as amendment

The performance of lanthanum carbonate (LC) pertaining to the adsorption of phosphate (H_wPO₄^w-3) was investigated, and the possible adsorption mechanism was elucidated. The stabilization of H_wPO₄^w-3 adsorbed to LC was evaluated. The influence of LC addition on the upward transport of phosphorus (P) from sediment to overlying water (OL-W) was studied, and the adsorption performance of H_wPO₄^w-3 on the LC-amended sediment was explored. The results of this work indicated that LC performed well in the elimination of H_wPO₄^w-3 from water in the pH range of 4 to 11, and the commercial and self-prepared LC samples afforded the maximum H_wPO₄^w-3 adsorption capacities of 57.9 and 99.4 mg P/g, respectively, at pH 7. The presence of coexisting species including chloride, bicarbonate, and sulfate had a small influence on the H_wPO₄^w-3 adsorption onto LC. The main H_wPO₄^w-3 adsorption mechanism of LC at pH 7 was the ligand exchange reaction between carbonate and H_wPO₄^w-3 forming the inner-sphere La-phosphate complexation. The self-synthesized LC exhibited much higher H_wPO₄^w-3 adsorption performance than the commercial LC. The overwhelming majority (> 97.0%) of H_wPO₄^w-3 adsorbed to LC primarily existed in the form of muriatic acid-extractable P, which has relatively low re-releasing risk. The addition of LC into sediment could significantly prevent the release of P from the sediment solid into the OL-W, thereby leading to a lower concentration level of reactive soluble P (RSP) in the OL-W compared with no LC treatment. The addition of LC into sediment could greatly improve the H_wPO₄^w-3 uptake ability for the sediment, and the enhancement of H_wPO₄^w-3 adsorption onto the sediment by the added LC increased as the increase of the amendment dosage and the initial H_wPO₄^w-3 concentration. All results suggest that LC could serve as a promising amendment material for the control of sedimentary P release.

Iron and zirconium modified luffa fibre as an effective bioadsorbent to remove arsenic from drinking water

Porous luffa plant fibre (LF) was grafted with Fe and Zr, and the ability of the fabricated adsorbents to remove arsenate (As(V)) from water was investigated in batch and column adsorption experiments. The Langmuir adsorption capacity (mg g^-1) at pH 7 of LF was found to be 0.035, which increased to 2.55 and 2.89 after being grafted with Fe (FLF-3) and Zr (ZLF-3), respectively. Grafting with Fe and Zr increased the zeta potential and zero point of charge (ZPC) of LF (from pH 3.9 to 7.4 for Fe grafting and to 7.6 for Zr grafting), due to chemical bonding of the metals, possibly with the hydroxyl and carboxylic groups in LF as indicated in FTIR peaks. Zeta potential and ZPC decreased after As adsorption owing to inner-sphere complexation mechanism of adsorption. The increase of pH from 3 to 10 progressively reduced the adsorbents' adsorption capacity. Co-existing anions weakened the As(V) removal efficiency in the order, PO₄^3- > SiO₃^2- > CO₃^2- > SO₄^2-. Adsorption kinetics data fitted well to the Weber and Morris model, which revealed initial fast and subsequent slow rates of intra-particle As diffusion into the bigger pores and smaller pores, respectively. Column adsorption data fitted well to the Thomas model with the predicted adsorption capacities in the same order as in the batch adsorption experiment (ZLF-3 > FLF-3 > LF).

Removing arsenic from water with an original and modified natural manganese oxide ore: batch kinetic and equilibrium adsorption studies

Arsenic contamination of drinking water is a serious water quality problem in many parts of the world. In this study, a low-cost manganese oxide ore from Vietnam (Vietnamese manganese oxide (VMO)) was firstly evaluated for its performance in arsenate (As(V)) removal from water. This material contains both Mn (25.6%) and Fe (16.1%) mainly in the form of cryptomelane and goethite minerals. At the initial As(V) concentration of 0.5 mg/L, the adsorption capacity of original VMO determined using the Langmuir model was 0.11 mg/g. The modified VMOs produced by coating VMO with iron oxide (Fe^a-VMO) and zirconium oxide (Zr^a-VMO) at 110 °C and 550 °C achieved the highest As(V) adsorption capacity when compared to three other methods of VMO modifications. Langmuir maximum adsorption capacities of Fe^a-VMO and Zr^a-VMO at pH 7.0 were 2.19 mg/g and 1.94 mg/g, respectively, nearly twenty times higher than that of the original VMO. Batch equilibrium adsorption data fitted well to the Langmuir, Freundlich, and Temkin models and batch kinetics adsorption data to pseudo-first order, pseudo-second order, and Elovich models. The increase of pH progressively from 3 to 10 reduced As(V) adsorption with a maximum reduction of 50-60% at pH 10 for both original and modified VMOs. The co-existing oxyanions considerably weakened the As(V) removal efficiency because they competed with As(V) anions. The competition order was PO₄^3- > SiO₃^2- > CO₃^2- > SO₄^2-. The characteristics of the original and modified VMOs evaluated using SEM, FTIR, XRD, XRF, surface area, and zeta potential explained the As(V) adsorption behaviour.

Performance evaluation of surfactant modified kaolin clay in As(III) and As(V) adsorption from groundwater: adsorption kinetics, isotherms and thermodynamics

In this paper surfactant modified kaolin clay for As(III) and As(V) was prepared by intercalating hexadecyltrimethylamonium bromide (HDTMA-Br) cationic surfactant onto the clay interlayers. Batch experiments were used to evaluate the effectiveness of surfactant modified kaolin clay towards As(III) and As(V) removal. The results revealed that adsorption of As(III) and As(V) is optimum at pH range 4–8. The maximum As(III) and As(V) adsorption capacities were found 2.33 and 2.88 mg/g, respectively after 60 min contact time. The data for adsorption of As(III) showed a better fit too pseudo first order model of reaction kinetics while the data for As(V) fitted better to pseudo second order model. The adsorption isotherm data for As(III) and As(V) fitted well to Langmuir model indicating that adsorption of both species occurred on a mono-layered surface. Adsorption thermodynamics model revealed that adsorption of As(III) and As(V) was spontaneous and exothermic. The presence of Mg²⁺ and Ca²⁺ increased As(III) and As(V) adsorption efficiency. The regeneration study showed that synthesized adsorbent can be used for up to 5 times with maximum As(III) and As(V) percentage removal of 54.2% and 62.33%, respectively achieved after 5^th cycle. Surfactant modified kaolin clay mineral showed higher adsorption capacity towards As(III) and As(V) as compared to unmodified kaolin clay mineral and competitive with other adsorbent in the literature. The results obtained from this study revealed that surfactant modified kaolin mineral is a candidate material for arsenic remediation from groundwater.

Optimisation of steam blanching on enzymatic activity, color and protein degradation of alfalfa (Medicago sativa) to improve some quality characteristics of its edible protein

The use of alfalfa protein in human food is limited by its low quality. Response Surface Methodology was employed to optimise the combined effects of different steam blanching conditions on the enzymatic activity, browning and protein degrading which cause undesirable characteristics. The optimum conditions were: steaming time 4.36 min, particle size 23 mm, time from harvesting to steaming 2 h leading to a residual activity of polyphenol oxidase of 1.31% and a completely inactivation of peroxidase. The Browning Index value was 108.3 and the non-protein nitrogen 170.2 (g kg^-1 TN). The browning and protein degradation rates of alfalfa treated under the optimum conditions were much lower than the control alfalfa after 60 days ensiling. This suggests that blanching of fresh whole alfalfa leaves under the optimum conditions was helpful for avoiding the appearance of the dark color and degradation of the extracted protein, improving its quality for human consumption.

Evaluation of the effectiveness and mechanisms of acetaminophen and methylene blue dye adsorption on activated biochar derived from municipal solid wastes

The adsorption potential and governing mechanisms of emerging contaminants, i.e. acetaminophen or acetyl-para-aminophenol (APAP) and methylene blue (MB) dye, on activated carbon derived from municipal solid waste were investigated in this work. Results showed that MB adsorption was significantly more effective, with a maximum removal of 99.9%, than APAP adsorption (%R_max = 63.7%). MB adsorption was found to be unaffected by pH change, while the adsorption capacity of APAP drastically dropped by about 89% when the pH was adjusted from pH 2 to 12. Surface reactions during APAP adsorption was dominated by both physical and chemical interactions, with the kinetic data showing good fit in both pseudo-first order (R² = 0.986-0.997) and pseudo-second order (R²>0.998) models. On the other hand, MB adsorption was best described by the pseudo-second order model, with R²>0.981, denoting that chemisorption controlled the process. Electrostatic attractions and chemical reactions with oxygenated surface functional groups (i.e., -OH and -COOH) govern the adsorption of APAP and MB on the activated biochar. Thermodynamic study showed that APAP and MB adsorption were endothermic with positive ΔH° values of 16.5 and 74.7 kJ mol^-1, respectively. Negative ΔG° values obtained for APAP (-3.7 to -5.1 kJ mol^-1) and MB (-11.4 to -17.1 kJ mol^-1) implied that the adsorption onto the activated biochar was spontaneous and feasible. Overall, the study demonstrates the effectiveness of activated biochar from municipal solid wastes as alternative adsorbent for the removal of acetaminophen and methylene blue dye from contaminated waters.