Molecular Weight Distribution Analysis Research Articles

Treatment of landfill leachate using electrochemically assisted UV/chlorine process: Effect of operating conditions, molecular weight distribution and fluorescence EEM-PARAFAC analysis

Leachate, a highly polluted wastewater, is generated from landfill containing complex compositions which have great impact on the environment. The advanced treatment of biochemically treated landfill leachate using electrochemically assisted UV/chlorine process (UEC) in a flow reactor was investigated. The effects of pH and current density on COD and NH3-N removal by UEC process were evaluated. At the pH value of 5.0, current density of 60mA/cm2, the removal efficiencies for COD and NH3-N were observed as 77% and 87%, respectively. The electrochemical process alone (EC) could obtain relatively high NH3-N removal but very low COD removal, compared with which, the UEC process significantly promoted the removal efficiency of COD while that of NH3-N increased to a very limited extent. Most of NH3-N was converted into N2 and little nitrogen compounds and chloramines were remained in the leachate after 8h treatment. Moreover, the variations of active chlorine and chloride ions were monitored in the EC and UEC systems, and a possible mechanism was proposed for the UEC process. The in situ electro-generated active chlorine and photo-generated radical species should be responsible for the efficient degradation of landfill leachate. The total energy consumption and current efficiency were 216.5 (kWh/kg COD) and 17.5%, respectively, for 8h treatment. In addition, the molecular weight (MW) percentage distribution analysis and PARAFAC analysis of excitation emission matrix (EEM) fluorescence spectroscopy indicated that the organic matters in the leachate were significantly degraded into the fractions with small molecular weight.

Isolation and characterization of fish scale collagen from tilapia (Oreochromis sp.) by a novel extrusion–hydro-extraction process

Collagen is highly valued both as a food additive and a functional food ingredient. It is generally extracted by treatments with acid or alkali, enzyme, and microorganisms. However these methods are generally batch type, time-, energy-, reactant-, and cost-consuming. Extrusion is widely used in the food industry, and offers many advantages, such as ease of operation, continuous production, high yield, and little waste. In this study, we developed a novel extrusion–hydro-extraction (EHE) process for extraction of collagen from tilapia fish scale. Extruded scale samples had a 2–3times higher protein extraction yield than that of non-extruded scale samples. All extracts contained hydroxyproline (61–73 residues/1000 residues) and hydroxylysine (5–6 residues/1000 residues) and were identified as type-I collagens by FTIR, SDS–PAGE, and molecular weight distribution analyses. The physicochemical studies revealed that extracted collagens could have promising applications in the food, medical, and cosmetic industries.

Molecular weight distributions in cotton-dyeing textile wastewaters

Many different chemicals are used in the textile industry, with its effluent being a major pollution source if not treated properly. High-strength textile wastewater requires an environmentally friendly, cost-effective and highly efficient treatment before being discharged into the environment. The goal of this study is to determine the appropriate treatment alternatives of high-strength textile wastewater based on the pollution strength and molecular weight distribution (MWD) analyses of pollutants from a cotton-dyeing textile mill. Sequential filtrations through microfiltration and ultrafiltration membranes were conducted separately on wastewater samples from dying, bleaching and mixed processes. According to MWD analyses, half of the total organic carbon, chemical oxygen demand (COD) and biochemical oxygen demand (BOD5) found in the wastewater which came from the bleaching and mixed processes were less than 1 kDa, while 56% of the COD and BOD5 found in the wastewater from dyeing was between 100 and 1 kDa. Moreover, the total kjeldahl nitrogen content of the bleached and dyed wastewaters was mostly higher than 1 kDa. Furthermore, UV254 absorbance in the mixed, bleaching and dyeing treatments was <1 kDa with ratios of 61, 49 and 25%, respectively. According to the Specific Ultraviolet Absorption values, the organic contents of all of these processes were hydrophilic. Experimental results indicated that biological and physical methods are more appropriate than chemical methods for treating the effluents of cotton-dyeing.

PC/SAN 블렌드의 계면장력에 미치는 저분자량 성분의 영향

PC와 SAN 사이의 계면장력 및 친화도에 미치는 저분자량 성분의 영향을 알아보기 위하여 용매 추출법으로 각 고분자에서 저분자량 성분을 추출하였다. GPC(gel permeation chromatography)로 분자량 분포를 확인한 결과, 각 고분자의 저분자량 성분은 용매 추출법에 의해 효과적으로 제거된 것을 확인하였다. 저분자량 성분이 제거된 고분자를 이용하여 계면장력 및 형태학 분석 결과, 저분자량 성분이 제거된 PC와 SAN은 계면장력이 높아졌고 친화도가 떨어진 것을 확인할 수 있었다. 즉 저분자량 성분이 두 고분자 사이에 상용화제와 같은 역할을 하는 것을 알 수 있었다. 두 고분자 중 SAN의 저분자량 성분이 PC의 저분자량 성분보다 상용화 효과에 더 많이 기여하는 것을 확인하였고, 이로서 PC/ABS 제조 시 저분자량 성분이 많이 포함된 SAN을 사용하는 것이 더 유리하다는 것을 알 수 있었다. Low molecular weight species were extracted from PC and SAN by a solvent extraction method in order to investigate the effect of low molecular weight species on interfacial tension and affinity between PC and SAN. From the analysis of molecular weight distribution by the GPC, it was confirmed that the low molecular weight species were effectively eliminated by the solvent extraction. Interfacial tension measurements and morphological observation were carried out with the PC and SAN of which the low molecular weight species were extracted. Interfacial tension was increased and the infinity was decreased for the extracted PC and SAN pair. This result implied that the low molecular weight species play a role as a compatibilizer between two polymers. Among two polymers, low molecular weight SAN contributes more in the compatibilization. Thus, it is favorable to use SAN containing a larger amount of low molecular weight species in fabrication of PC/ABS blend.

Effect of Sub- and Super-critical Water Treatment on Physicochemical Properties of Porcine Skin.

Super- and sub-critical water treatments have been of interest as novel methods for protein hydrolysis. In the present study, we studied the effect of sub-critical water (Sub-H2O, 300℃, 80 bar) treatment as well as super-critical water (Super-H2O, 400℃, 280 bar) treatment on the physicochemical properties of porcine skin (PS), which has abundant collagen. Porcine skin was subjected to pre-thermal treatment by immersion in water at 70℃, and then treated with sub- or super-critical water. Physicochemical properties of the hydrolysates, such as molecular weight distribution, free amino acid content, amino acid profile, pH, color, and water content were determined. For the molecular weight distribution analysis, 1 kDa hydrolyzed porcine skin (H-PS) was produced by Super-H2O or Sub-H2O treatment. The free amino acid content was 57.18 mM and 30.13 mM after Sub-H2O and Super-H2O treatment, respectively. Determination of amino acid profile revealed that the content of Glu (22.5%) and Pro (30%) was higher after Super-H2O treatment than after Sub-H2O treatment, whereas the content of Gly (28%) and Ala (13.1%) was higher after Sub-H2O treatment. Super-H2O or Sub-H2O treatment affected the pH of PS, which changed from 7.29 (Raw) to 9.22 (after Sub-H2O treatment) and 9.49 (after Super-H2O treatment). Taken together, these results showed that Sub-H2O treatment was slightly more effective for hydrolysis than Super-H2O was. However, both Sub-H2O and Super-H2O treatments were effective processing methods for hydrolysis of PS collagen in a short time and can be regarded as a green chemistry technology.

Production of Bioactive Peptides from Soybean Meal by Solid State Fermentation with Lactic Acid Bacteria and Protease

In this study, soybean meal was first solid state fermented with different strains of Lactic Acid Bacteria (LAB). Among the strains used, <em>Lactobacillus plantarum</em> Lp6 was selected for further studies because of its highest Degree of Hydrolysis (DH) of protein (2.49±0.08%) in soybean meal after 72 h fermentation. Soybean meal fermented with <em>L. plantarum</em> Lp6 can also improve its DPPH radical scavenging and Angiotensin Converting Enzyme (ACE) inhibitory activities. The addition of protease into soybean meal during the fermentation resulted in lowered IC₅₀ of DPPH radical scavenging and ACE inhibitory activities, indicating more bioactive peptides were produced during fermentation. Molecular weight distribution analysis revealed the Extracts from Fermented Soybean Meal (EFSM) was mainly composed of oligopeptides. These results indicated that soybean meal fermented with <em>L. plantarum</em> Lp6 and protease could be an easy and cheap method to produce functional food.

Контроль качества молекулярно-массового распределения полисахаридов с помощью эксклюзионной хроматографии с детектором многоуглового лазерного светорассеяния

Показано, что контроль качества лекарственных средств на основе гидроксиэтилированного крахмала можно проводить с помощью абсолютного метода анализа молекулярно-массового распределения — эксклюзионной хроматографии с детектором многоуглового лазерного светорассеяния. В работе приведены результаты, необходимые для обоснования включения описанной методики в отечественные нормативные документы на гидроксиэтилированный крахмал.

Composition and structure of organosolv lignins from four eucalypt species

Lignins were extracted from different species using organosolv process (ethanol/water). Obtained organosolv lignins were characterised by various methods to determine their composition, structure and functional groups with the purpose of evaluating their potential use for obtaining value-added compounds. The purity of organosolv lignins was determined. The total phenols content and the antioxidant power were analysed in order to know the reactivity of lignins. The ratio S/G was determined by nitrobenzene oxidation. In addition, molecular weight distribution, infrared spectroscopy and thermo gravimetrical analysis were carried out in order to determine the physical and chemical properties of organosolv lignins. Obtained organosolv lignins have very high purity and low sugar and inorganic contamination. All organosolv lignins samples have high polydispersity, and lignin from grey ironbark wood had the highest molecular weight average. Among the organosolv lignins, lemon-scented gum showed the highest average value of S/G ratio and the lowest average value of total phenols.

The effect of solids retention times on the characterization of extracellular polymeric substances and soluble microbial products in a submerged membrane bioreactor.

In this study, the effect of solids retention times (SRTs) on extracellular polymeric substances (EPS) and soluble microbial products (SMPs) were investigated in a membrane bioreactor (MBR) at SRTs of 10, 5 and 3 days. The results showed that more carbohydrates and proteins were accumulated at short SRT, which can due to the higher biomass activity in the reactor. The molecular weight (MW) distribution analysis suggested that macromolecules (MW>30 kDa) and small molecules (MW<1 kDa) were the dominant fraction of EPS and SMP, respectively. The reactor at shorter SRT had more small molecules and less macromolecules of carbohydrates. The MW distribution of total organic carbon (TOC) suggested that other organic moieties were exuded by microbes into the solution. The shorter SRT had more undefined microbial by-product-like substances and different O − H bonds in hydroxyl functional groups.

English

The enzymatic hydrolysate of freshwater clam (Corbicula fluminea) extract was prepared using commercially available proteases. The antioxidant activity of the hydrolysate was evaluated by reducing power and 2,2&rsquo;-azinobis-3-ethylbenzothiazoline-6-sulfonic acid free radical decolorization assays. The hydrolysate, especially its fraction purified by gel filtration, had a good antioxidant activity. The Trolox equivalent antioxidant capacity of the fraction with the highest radical scavenging ability reached 158.04 &plusmn; 2.43 &mu;g/mg, which was sevenfold higher than that of the original hydrolysate. Molecular weight distribution analysis revealed that peptides over 1000 Da in the hydrolysate had better abilities to donate electrons, whereas peptides below 1000 Da more effectively eliminated radicals. Therefore, peptides from freshwater clam extract could be employed as potential natural antioxidants, performing their activities via different mechanisms. Key words: Antioxidant peptides, freshwater clam extract, enzymatic hydrolysate, molecular weight distribution.

SEDFIT-MSTAR: molecular weight and molecular weight distribution analysis of polymers by sedimentation equilibrium in the ultracentrifuge.

Sedimentation equilibrium (analytical ultracentrifugation) is one of the most inherently suitable methods for the determination of average molecular weights and molecular weight distributions of polymers, because of its absolute basis (no conformation assumptions) and inherent fractionation ability (without the need for columns or membranes and associated assumptions over inertness). With modern instrumentation it is also possible to run up to 21 samples simultaneously in a single run. Its application has been severely hampered because of difficulties in terms of baseline determination (incorporating estimation of the concentration at the air/solution meniscus) and complexity of the analysis procedures. We describe a new method for baseline determination based on a smart-smoothing principle and built into the highly popular platform SEDFIT for the analysis of the sedimentation behavior of natural and synthetic polymer materials. The SEDFIT-MSTAR procedure - which takes only a few minutes to perform - is tested with four synthetic data sets (including a significantly non-ideal system), a naturally occurring protein (human IgG1) and two naturally occurring carbohydrate polymers (pullulan and λ-carrageenan) in terms of (i) weight average molecular weight for the whole distribution of species in the sample (ii) the variation in "point" average molecular weight with local concentration in the ultracentrifuge cell and (iii) molecular weight distribution.

Production of propionic acid-enriched volatile fatty acids from co-fermentation liquid of sewage sludge and food waste using Propionibacterium acidipropionici

Volatile fatty acids (VFA), derived from sludge fermentation, have been used as one effective carbon source for biological nutrient removal, especially favorable with VFA containing with high levels of propionic acid. In this paper, a new fermentation method was employed to significantly produce the propionic acid-enriched VFA from the co-fermentation liquid of sewage sludge and food waste: including (1) mixing food waste with sludge in the anaerobic digester (the first stage) and (2) separating the mixture, sterilizing the first stage liquid and fermenting it after inoculation with Propionibacterium acidipropionici (the second stage). The effect of the key parameters including pH, the mixing ratio of the food waste and sludge, fermentation time and temperature of the first stage on the propionic acid-enriched VFA production (the second stage) was individually discussed. By the molecular weight distribution analysis, the comparison of the solubilisation and hydrolysis process in difference parameters was fully elaborated. The optimal combination of the parameters was then obtained. Finally, the propionic acid-enriched VFA fermentation was successfully conducted in a semi-continuous reactor using the first stage liquid from the optimal condition.

Production of Angiotensin I Converting Enzyme Inhibitory Peptides from Peanut Meal Fermented with Lactic Acid Bacteria and Facilitated with Protease

The aim of this study was to develop a simpler and cheaper technique using a combination of Lactic Acid Bacteria (LAB) fermentation and protease hydrolysis to accelerate the production of bioactive peptides in peanut meal. Firstly, peanut meal was fermented with a total of 14 LAB strains to assay <em>in vitro</em> Angiotensin I Converting Enzyme (ACE) inhibitory activity and Degree of Hydrolysis (DH). Among the strains used, <em>Lactobacillus plantarum</em> Lp6 was selected for further studies because of its highest ACE inhibitory activity (47.83±4.92%) and DH of protein (2.29±0.51%). The addition of protease during the fermentation could highly improve the soluble protein, DH and ACE inhibitory activity of peanut meal. Molecular weight distribution analysis revealed the Extracts from Fermented Peanut Meal (EFPM) was mainly composed of oligopeptides. The ACE inhibitory activity of EFPM remained stable after pepsin and pancreatin treatments simulating an <em>in vitro</em> gastrointestinal digestion. Furthermore, the EFPM exerted potent antihypertensive effect in Spontaneously Hypertensive Rats (SHR) after oral administrations at a dose of 200 or 500 mg/kg body weight. In conclusion, the peanut meal fermented with <em>L. plantarum</em> Lp6 and facilitated with protease could serve as a useful antihypertensive product in the prevention and treatment of hypertension.

Reduction of disinfection byproduct formation by an oxidative coupling reaction with birnessite

This study investigates the reduction of Disinfection Byproduct (DBP) formation from Natural Organic Matter (NOM) surrogates, resorcinol and phloroglucinol by oxidative coupling reaction induced by birnessite. Birnessite was introduced into an aqueous solution of resorcinol or phloroglucinol under various birnessite dose, pH, and ionic strength. After reaction, a part of the dissolved fraction was characterized by UV/Vis spectroscopy, fluorescence spectroscopy, size exclusion chromatography. Another part was reacted with sodium hypochlorite to investigate the DBP formation and chlorine consumption. Polymerization of resorcinol and phloroglucinol by an oxidative coupling reaction was verified by spectroscopic analysis and molecular weight distribution analysis. Total DBP and chloroform formation from the NOM surrogates greatly decreased after reaction with birnessite. Chloroform formation further decreased when pH and ionic strength remained low during oxidative coupling. Meanwhile, the fraction of chloroacetic acids of total DBPs increased after the coupling of phenolic compounds due to increases in intermediates containing a carbonyl group. This study would contribute to establish a new and efficient alternative for DBPs formation control.

Study of the degradation of a new PLA braided biomaterial in buffer phosphate saline, basic and acid media, intended for the regeneration of tendons and ligaments

The purpose of this study was to evaluate the effects of hydrolytic degradation on the properties of a PLA hollow braid designed as a new concept of biodegradable prosthesis for the regeneration of tendons and ligaments. The main function of the braided material is to bear mechanical loads while it is being replaced by the newly-generated tissue. The kinetics of braided material degradation is thus an important factor in determining the success of the product. In order to study this mechanism, PLA braid was subjected to a 12-month degradation process at 37 °C in PBS at pH 7.4 (to simulate the human physiological medium) and to accelerated degradation for one month in pH 12 and pH 3 solutions. Degradation of the braid subjected to hydrolysis was evaluated by weight loss, molecular weight distribution, mechanical properties, and calorimetric and morphologic analyses. The weight loss in a basic medium reached 21%, versus no significant change in the other media. Average molecular weight was reduced by approximately 50% in the three media, with loss of mechanical properties in all cases. The morphological changes were more evident in the PLA degraded in the basic medium. The crystallinity of the material increased at the first stages of degradation, regardless of the medium used.

Antioxidant Effect and Water-Holding Capacity of Roselle (&lt;em&gt;Hibiscus sabdariffa L.&lt;/em&gt;) Seed Protein Hydrolysates

The aim of this study was to investigate the effect of <em>in</em>-vitro pepsin and pancreatin digestion of proteins extracted from Roselle seed on the production of bioactive peptides. Defatted Roselle seed flour was used to extract different protein fractions namely globulin, albumin and glutelin. The proteins were digested using pepsin (1 h) followed by pancreatin (1 h) in order to produce hydrolysates with good antioxidant activity. The prepared hydrolysates were as effective as antioxidants in model systems, in scavenging of free radicals and acting as reducing agents. This effect was concentration-dependent and was also influenced by the type of protein fraction. The albumin fraction hydrolysates prepared showed the highest antioxidant activity followed by Glutelin and Globulin hydrolysates respectively (Albumin hydrolysates>Glutelin hydrolysates>Globulin hydrolysates). All of the prepared hydrolysates were also found to be effective in enhancing water-holding capacity and cooking yield in a meat model system. Albumin hydrolysates showed the highest improved meat cooking ability followed by Glutelin and Globulin respectively (Albumin hydrolysates>Glutelin hydrolysates>Globulin hydrolysates). The molecular weight distribution analysis of the hydrolysates was determined and most of the peptides were found between 1000 Da and below. The study findings suggest that Roselle seed protein hydrolysates can be applied as functional food ingredients and that their composition determines their functional properties thus their potential application in the food and feed industries.

Analyses of molecular weight distribution of organic matters with pre-oxidation and PAC–UF pretreatment before seawater reverse osmosis

The water source of Shanghai, China is located in the lower Yantze River close to the estuary of East Sea. Due to the decreasing of upriver water in recent years, the water supply is facing with the challenge of salt tide from East Sea. Before reverse osmosis, powdered activated carbon–ultrafiltration (PAC–UF) pretreatment is employed to remove organic matters and turbidity to prevent the rapid fouling of reverse osmosis membrane. The purpose of this study was to analyze molecular weight (MW) distribution and conversion in oxidation and PAC–UF pretreatment processes and to find out the relationship between dissolved organic carbon (DOC) removal, oxidant dosage and PAC–UF treatment. The results showed that by conventional water treatment, chlorination (Cl2) and potassium permanganate (KMnO4), pre-ozonation can reduce DOC concentration for larger MW fractions (>30 k, 10–30 k, and 3 k–10kDalton (Da.)), however, at the same time, increased smaller MW fraction. PAC adsorption was regarded as the effective way to remove DOC in smaller MW fractions. Quantitative data were statistically explained. In combination of postozonation, PAC–UF can eliminate large amount of DOC in <1 kDa. MW fraction. It is observed that the treatment process has a better effect at removing trihalomethane formation potential (THMFP) than haloacetic acid formation potential (HAAFP), though HAAFP concentration is reduced as well. In finished water, larger MW fraction has higher HAA potential reactivity, and the part with lower than 1 k and 1 k–3 k Da. leads to trihalomethanes (THMs) formation potential. In conclusion, PAC–UF in assistant of pre-oxidation was able to remove majority of organic matters to prevent the rapid fouling of reverse osmosis membrane.

Application of high density steam flash-explosion in protein extraction of soybean meal

The high density steam flash-explosion (HDSFE) was used to extract protein from soybean meal. Soybean meal samples were treated at 1.3MPa and 1.8MPa for 60s, 120s and 180s, respectively. After HDSFE treatment at 1.8MPa for 180s, the extraction yield of protein was increased from 50.50% to 65.66% compared with untreated soybean meal. The emulsification properties and fat-binding capacity of soy protein isolate (SPI) extracted from soybean meal treated by HDSFE were all improved compared with SPI extracted from untreated soybean meal and white flakes. Molecular weight distribution analysis of SPI showed that after HDSFE treatment the peak with molecular weight about 504kDa and 43.3kDa disappeared and the peak with molecular weight about 669kDa increased indicating protein aggregation. Gel electrophoresis showed that high molecular weight aggregates of protein have been formed by covalent bond.

Foulant analysis of a reverse osmosis membrane used pretreated seawater

This study focused on the characterization of organic and biological foulants on reverse osmosis (RO) membrane and fouled RO membrane characterization with seawater pretreated by submerged membrane hybrid systems (SMHSs). New low pressure membrane based pretreatments namely submerged membrane coagulation hybrid system (SMCHS) and submerged membrane coagulation-adsorption hybrid system (SMCAHS) were investigated. Organic foulants on RO membrane were characterized in terms of molecular weight distribution (MWD), fluorescence and extracellular polymeric substance (EPS) analyses. The organic foulants were mainly composed of high molecular weight matters representing biopolymers in the foulants. The fluorescence excitation–emission matrix (F-EEM) analysis showed that protein-like materials were dominant with samples pretreated by SMHSs. Humic-like materials which have lower aromaticity were also present in the foulant. Biological foulants were investigated in terms of total direct cell (TDC) count, cell viability and biomass activity (adenosine tri-phosphate; ATP). Biological fouling was found to be reduced by organic removal with SMHSs. The fouled membranes were characterized using environmental scanning electron microscopy coupled with energy dispersive spectroscopy, attenuated total reflection-Fourier transform infrared spectrometry, zeta-potential measurement, atomic force microscopy, and contact angle measurement.

Derivatization-free gel permeation chromatography elucidates enzymatic cellulose hydrolysis

BackgroundThe analysis of cellulose molecular weight distributions by gel permeation chromatography (GPC) is a powerful tool to obtain detailed information on enzymatic cellulose hydrolysis, supporting the development of economically viable biorefinery processes. Unfortunately, due to work and time consuming sample preparation, the measurement of cellulose molecular weight distributions has a limited applicability until now.ResultsIn this work we present a new method to analyze cellulose molecular weight distributions that does not require any prior cellulose swelling, activation, or derivatization. The cellulose samples were directly dissolved in dimethylformamide (DMF) containing 10-20% (v/v) 1-ethyl-3-methylimidazolium acetate (EMIM Ac) for 60 minutes, thereby reducing the sample preparation time from several days to a few hours. The samples were filtrated 0.2 μm to avoid column blocking, separated at 0.5 mL/min using hydrophilic separation media and were detected using differential refractive index/multi angle laser light scattering (dRI/MALLS). The applicability of this method was evaluated for the three cellulose types Avicel, α-cellulose and Sigmacell. Afterwards, this method was used to measure the changes in molecular weight distributions during the enzymatic hydrolysis of the different untreated and ionic liquid pretreated cellulose substrates. The molecular weight distributions showed a stronger shift to smaller molecular weights during enzymatic hydrolysis using a commercial cellulase preparation for cellulose with lower crystallinity. This was even more pronounced for ionic liquid-pretreated cellulose.ConclusionsIn conclusion, this strongly simplified GPC method for cellulose molecular weight distribution allowed for the first time to demonstrate the influence of cellulose properties and pretreatment on the mode of enzymatic hydrolysis.