Two-step Ultrafiltration Process Research Articles

Fractionation of Stevia rebaudiana aqueous extracts via two-step ultrafiltration process: towards rebaudioside a extraction

The consumption of sugar-based foods has generated significant attention when dealing with influence towards chronic diseases, such as obesity diabetes mellitus, cancer, lipid metabolism disorders, among others. The food industry has currently found a profitable market in using reduced-calorie artificial sweeteners to elaborate dietary products. However, many studies have addressed the possibility of harmful effects of the prolonged consumption of artificial sweeteners on human health, e.g. cancer and diabetes. For this reason, industries have been focused on the use of natural sweeteners, such as steviol glycosides (SGs), which have become important into food industry. Herein, we propose an integrated membrane system, implementing two different ultrafiltration membranes (100 and 1 kDa), to separate rebaudioside A (reb A) from aqueous extracts of Stevia rebaudiana. By using this approach, we found out that the UF100 membrane served mostly to remove total solids (∼42%) and carbohydrates (∼41%) from the crude extract, while tight UF1 membrane was able to retain the phenolic compounds (∼98%). Moreover, the integrated membrane system allowed the recovery of reb A (up to 38 mg). Our results demonstrate that such a membrane-based process is a viable alternative for the fractionation and extraction of SGs from Stevia rebaudiana, but also some other high-added valued molecules (such as carbohydrates and polyphenols) can be concurrently recovered.

Purification of Endoxylanase from Bacillus pumilus B20 for Production of Prebiotic Xylooligosaccharide Syrup; An In vitro Study.

Background: The need for more cost-effective compounds is imperative because the demand for prebiotic compounds is ever on the rise. Objective: The focus of this study is the purification of the endoxylanase from Bacillus pumilus B20 and its application in a cost-effective production of the prebiotic xylooligosaccharide (XOS) syrup having a high concentration of oligosaccharides. Materials and Methods: The extracellular endoxylanase was purified using ammonium sulphate fractionation, DEAE anion exchange, and Sephacryl gel filtration chromatography. The enzymatically produced XOS was used in the preparation of XOS syrup adopting the method of ultrafiltration with 10 and 3 kDa molecular weight cut-off (MWCO) membranes. Culture-dependent technique for the bacterial enumeration using selective probiotic microorganisms in an in vitro analysis was employed to confirm the prebiotic nature of XOS syrup. Results: The molecular mass of the purified xylanase (XylB) was found to be approximately 85 kDa with the optimum pH and temperature of 6.5 and 60 °C, respectively. XylB hydrolyzed the xylan and produced short-chain xylooligosaccharides (XOS). At the end of the two-step ultrafiltration process, the hydrolysate was refi ned to form XOS syrup (44.4%) consisting of XOS with a degree of polymerization (DP) between 2 and 5, and >5. Among all the tested probiotic strains, Lactobacillus brevis exhibited maximum growth in the presence of 0.5% XOS syrup with a specific growth rate of 1.2 h-1. Conclusion: Through this study, we have identified a method to produce XOS syrup that can be used as an effective prebiotic supplement for the growth of several probiotic strains. Human gut probiotics was used as a model system for in vitro analysis of prebiotic oligosaccharide XOS, but for further confirmation of the prebiotic activity, in vivo feeding studies using animal models are needed to be carried out.

Micelle size characterization of lipopeptides produced by B. subtilis and their recovery by the two-step ultrafiltration process

The aim of this work was to investigate the lipopeptides aggregation behavior in single and mixed solutions in a wide range of concentrations, in order to optimize their separation and purification following the two-step ultrafiltration process and using large pore size membranes (up to MWCO=300kDa). Micelle size was determined by dynamic light scattering. In single solutions of lipopeptide both surfactin and mycosubtilin formed micelles of different size depending on their concentration, micelles of average diameter=5–105nm for surfactin and 8–18nm for mycosubtilin. However when the lipopeptides were in the same solution they formed mixed micelles of different size (d=8nm) and probably conformation to that formed by the individual lipopeptide, this prevents their separation according to size. These lipopeptides were purified from fermentation culture by the two-step ultrafiltration process using different MWCO membranes ranging from 10 to 300kDa. This led to their effective rejection in the first ultrafiltration step by membranes with MCWO=10–100kDa but poor rejection by the 300KDa membrane. The lipopeptides were recovered at 90% purity (in relation to protein) and with 2.34 enrichment in the permeate of the second ultrafiltration step with the 100KDa membrane upon addition of 75% ethanol.

Isolation of lactoferrin from bovine colostrum by ultrafiltration coupled with strong cation exchange chromatography on a production scale

Lactoferrin (LF) was isolated from bovine colostrum by ultrafiltration and then purified with a fast flow strong cation exchange chromatography system in a production scale. A two-step ultrafiltration process was performed with membranes of nominal molecular weight cut-offs of 100 kDa for ultrafiltration (UF) step 1 (UF-1) and 10 kDa in the UF step 2 (UF-2). The UF-1 process was performed at fixed transmembrane pressure (TMP), tangential flow velocity and temperature equivalent to 200 kPa, 5 m/s, and 25 °C, respectively. The optimum operating parameters for the UF-2 were a tangential flow velocity of 4 m/s, limiting TMP of 150 kPa, and an operating temperature of 50 °C. The predicted permeate flux based on a resistance mathematical model was not significantly ( p > 0.05) different from those of the actual experiment. The LF concentrated in the UF-2 retentate reached a purity of 30.88% (w/w) and a recovery of 94.04%. A stepwise procedure for purification of the crude LF was conducted using a preparative-scale strong cation exchange chromatography. The LF eluted with 1.0 M NaCl aqueous buffer showed a single band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) with a molecular weight of 80,400 Da. The purity and the recovery of the final LF product were 94.20% and 82.46%, respectively. The process developed in this work is a significant improvement over the commercial practice for the fractionation of LF from bovine colostrum.

Recovery and purification of surfactin from fermentation broth by a two-step ultrafiltration process

Surfactin is a bacterial lipopeptide produced by Bacillus subtilis and it is a powerful surfactant, having also antiviral, antibacterial and antitumor properties. The recovery and purification of surfactin from complex fermentation broths is a major obstacle to its commercialization; therefore, two-step membrane filtration processes were evaluated using centrifugal and stirred cell devices while the mechanisms of separation were investigated by particle size and surface charge measurements. In a first step of ultrafiltration (UF-1), surfactin was retained effectively by membranes at above its critical micelle concentration (CMC); subsequently in UF-2, the retentate micelles were disrupted by addition of 50% (v/v) methanol solution to allow recovery of surfactin in the permeate. Main protein contaminants were effectively retained by the membrane in UF-2. Ultrafiltration was carried out either using centrifugal devices with 30 and 10 kDa MWCO regenerated cellulose membranes, or a stirred cell device with 10 kDa MWCO polyethersulfone (PES) and regenerated cellulose (RC) membranes. Total rejection of surfactin was consistently observed in UF-1, while in UF-2 PES membranes had the lowest rejection coefficient of 0.08 ± 0.04. It was found that disruption of surfactin micelles, aggregation of protein contaminants and electrostatic interactions in UF-2 can further improve the selectivity of the membrane based purification technique.

Purification of lysozyme using ultrafiltration.

This article examines the separation of lysozyme from chicken egg white by ultrafiltration with 25 kDa and 50 kDa MWCO polysulfone membranes. The effects of pH, system hydrodynamics, feed concentration, and transmembrane pressure on permeate flux, lysozyme transmission, purification factor, and productivity have been discussed. With both types of membranes, higher permeate flux and lysozyme transmission were observed at higher pH. Higher lysozyme purity was generally obtained with the 25 kDa MWCO membrane. Purity of lysozyme decreased when the feed concentration was increased. With the 50 kDa MWCO membrane permeate flux, productivity and the purity of lysozyme were found to increase with increase in transmembrane pressure. The possibility of using a two-step ultrafiltration process for achieving high productivity along with high purity of lysozyme was also investigated.

Efficient molecular mass fractionation of leukocyte extract by membrane separation

The unique choice of a pair of membranes for a two-step ultrafiltration process of a leukocyte extract allowed to obtain from it an almost homogenous active product. This choice was based on the chromatographic analysis of the permeates after ultrafiltration of the extract using the polyamide hollow fibers VPU-15 (cut-off 15 kDa) and VPU-5 (cut-off 5 kDa) and a flat-sheet membrane produced from cellulose acetate UAM-150 (cut-off 5 kDa). The elution profiles of the permeates of the VPU-5 and UAM-150 membranes showed less outer similarity than the permeates of the VPU-5 and VPU-15 membranes: the hollow fibers VPU-5 and VPU-15 let through the same fractions, except for one more highly molecular fraction, according to the differences in the nominal selectivity of the membranes. The discovered similarity of the fractional composition of the permeates, which reflects the resemblance of the macro and microstructure of the membranes determined the pair of membranes (VPU-15 and VPU-5) which allowed for a successful molecular mass separation.

Comparison of bifidobacterial growth-promoting activity of ultrafiltered casein hydrolyzate fractions

Summary - Growth rates and acid production of the most common dairy-related bifidobacteria (Bifidobacterium infantis, B breve and B longum) were determined in the presence of casein hydrolyzates produced by the action of three proteolytic enzymes (alcalase, chymotrypsin and trypsin). Casein hydrolyzates were fractionated with a two-step ultrafiltration process to study the effect of molecular mass of peptides on bifidobacterial growth. The retentate of the second ultrafiltration (nominal molecular eut-off of membranes was 1000 Da) was called mixture of polypeptides (MP) and the permeate fraction which was mainly composed of free amino acids and small peptides was called AA. These hydrolyzate fractions were characterized by a very different concentration of some amino acids (glu, tyr, phe). Among MP and AA casein fractions, trypsin MP fraction at a final concentration of 2% in synthetic medium (Garches medium) exhibited a higher growth-promoting activity on the three bifidobacterial species tested. However, addition of alcalase AA fraction at a final concentration of 1 or 2% repressed the growth and acid production of B breve and B longum.

Growth of Nonproteolytic Lactococcus lactis in Culture Medium Supplemented with Different Casein Hydrolyzates

The growth and lactic acid production of nonproteolytic variants of Lactococcus lactis, three Lactococcus lactis ssp. cremoris strains (E8, Wg2, and HP) and one Lactococcus lactis ssp. lactis strain (1076), were compared with those of their parent strains in Garches medium supplemented with different casein hydrolyzates. Molecular weight distribution and AA composition of casein hydrolyzates were different. Two fractions of alcalase casein hydrolyzates separated and concentrated by a two-step ultrafiltration process were compared with two commercial casein hydrolyzates. Proteinase-negative variants of lactococci exhibited the same specific growth rate and production of lactic acid as proteinase-positive strains in all enriched Garches media. Cell growth was affected by molecular weight distribution of peptides in hydrolyzates, but not by their AA composition. Lactococcus lactis ssp. lactis grew better than L. lactis ssp. cremoris, but its lactic acid production was similar to that of E8 strains. Among L. lactis ssp. cremoris, Wg2 strains grew better in Garches medium supplemented with casein hydrolyzates with molecular weight <2000Da, but growth and lactic acid production of HP strains were better in Garches medium enriched with casein hydrolyzates with molecular weight >2000Da. Different casein hydrolyzate fractions could be used to supplement culture medium and to standardize milk cultures; however, choice of casein hydrolyzates depends on subspecies of lactococci.

Fractionation of casein hydrolysates using polysulfone ultrafiltration hollow fiber membranes

The objective of this study was to characterize the fractionation profile of casein hydrolysates obtained with polysulfone hollow fiber ultrafiltration membranes. The two-step ultrafiltration process developed by Turgeon and Gauthier [J. Food Sci., 55 (1990) 106] was used: a caseinate solution was submitted to proteolysis with chymotrypsin or trypsin, and the reaction mixture (RM) was subsequently ultrafiltered using a 30 kDa (MWCO) hollow-fiber polysulfone membrane. The total hydrolysate permeating from this first step was further fractionated using a 1 kDa (MWCO) membrane, producing the mixture of polypeptides (retentate) and the amino acid fraction (permeate). The effect of enzyme specificity and of membrane retentivitiy on the total composition (total nitrogen, fat, lactose, minerals) and amino acid profile of the fractions was studied. The overall composition of the fractions was not significantly affected by the nature of the enzyme but the degree of hydrolysis and the molecular weight distribution profile analyses showed a marked effect of the enzyme specificity, with trypsin giving a larger proportion of small peptides (< 200 Da) in the mixture of polypeptides. Amino acid profile analyses provided useful information on the phenomena governing the fractionation of amino acids with a polysulfone membrane: (1) the target amino acids of the enzyme are concentrated in the permeate as a result of their presence in all peptides produced by hydrolysis, (2) polar amino acids are retained by the membrane, (3) non-polar amino acids are not selectively rejected by the membrane. Our results suggest that the charge/hydrophobicity balance of the peptides produced is the predominant factor determining the fractionation of casein hydrolysates.

Interfacial and emulsifying properties of whey peptide fractions obtained with a two-step ultrafiltration process

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInterfacial and emulsifying properties of whey peptide fractions obtained with a two-step ultrafiltration processSylvie L. Turgeon, Sylvie F. Gauthier, and Paul PaquinCite this: J. Agric. Food Chem. 1991, 39, 4, 673–676Publication Date (Print):April 1, 1991Publication History Published online1 May 2002Published inissue 1 April 1991https://doi.org/10.1021/jf00004a009RIGHTS & PERMISSIONSArticle Views333Altmetric-Citations74LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts