Size Exclusion Chromatography System Research Articles

Overview of 37 Tear Substitutes in Europe Based on Various Physicochemical Parameters.

Dry eye disease (DED) is one of the most prevalent eye conditions worldwide, with artificial tears serving as a primary treatment option. Despite their wide availability on the European market, there is a lack of established classifications based on their physicochemical properties. The aim of our study was therefore (i) to develop an analytical method that measures the concentration and the molecular weight (MW) of the hyaluronic acid (HA) in commercialized products, and (ii) to propose an overview based on their various physicochemical parameters. The intrinsic viscosity and MW of the HA, as well as osmolarity, pH, rheological profile, and viscosity, were measured or determined. A specific method was developed to measure the average intrinsic viscosity and HA content using a liquid size-exclusion chromatography system. The MW was determined using the Mark-Houwink equation. Thirty-seven products commercialized in Europe were analyzed, with 21 of them containing HA. The HA MW was lowest (300kDa) for Thealose®, Thealoz Duo® Gel, and Hyabak®, and highest (1300kDa) for Vismed® Multi, Vismed® Gel, and Neovis® Gel. The pH values varied between 5.94 for Treovis® and 8.06 for Systane® Ultra. Osmolarity ranged between 148 mOsm/L and 325 mOsm/L for Neovis® and Treovis®, respectively. Viscosity was highly variable, ranging from 0.38 mPas·s for Hylolipid® to 337.47 mPas·s for Thealoz® Duo Gel. Finally, rheological profile analysis revealed different shear-thinning behaviors. While the perfect eye drop does not exist, a multitude of options are available to choose from. This study improves our understanding of the major tear substitutes available on the European market based on several physicochemical properties. A better understanding and awareness of these parameters is crucial in order to offer the best treatment for patients with DED.

A Sacrificial Linker in Biodegradable Polyesters for Accelerated Photoinduced Degradation, Monitored by Continuous Atline SEC Analysis.

Polymeric materials that undergo photoinduced degradation have wide application in fields such as controlled release. Most methods for photoinduced degradation rely on the UV or near-UV region of the electromagnetic spectrum; however, use of the deeply penetrating and benign wavelengths of visible light offers a multitude of advantages. Here we report a lactone monomer for ring-opening copolymerizations to introduce a sacrificial linker into a polymer backbone which can be cleaved by reactive oxygen species which are produced by a photocatalyst under visible light irradiation. We find that copolymers of this material readily degrade under visible light. We followed polymer degradation using a continuous flow size exclusion chromatography system, the components of which are described herein.

Upgraded D22 SEC-SANS setup dedicated to the biology community.

Described here is the current status of the upgraded in situ size-exclusion chromatography (SEC) system implemented with the D22 small-angle neutron scattering (SANS) instrument at the Institut Laue-Langevin. Since its initial proof of principle in 2016, this SEC-SANS arrangement has been continuously requested by the user community, leading to the design of an upgraded version. A detailed description of the setup and its control is provided, and a few examples of protein structural investigations are presented, which will highlight the various possibilities and limitations of the setup to optimize experimental success.

Decoupling Optical Response and Photochemical Formation of Singlet Oxygen in Size Isolated Fractions of Ozonated Dissolved Organic Matter.

The complex effects of ozonation on the photophysical and size-based properties of dissolved organic matter (DOM) were investigated using two DOM isolates, Suwannee River Fulvic Acid (SRFA) and Pony Lake Fulvic Acid (PLFA). A size exclusion chromatography system paired with absorbance, fluorescence, and total organic carbon detection was used to determine the fluorescence quantum yield (Φf) as a function of the apparent molecular weight (AMW). Size-based fractions of each isolate were collected and irradiated to measure singlet oxygen (1O2) quantum yield (Φ1O2). Φf decreased with ozonation in low AMW fractions, while increasing in high AMW fractions. Φ1O2 increased with ozone dose in low AMW fractions from ∼2 to ∼7% and ∼3 to ∼11% for PLFA and SRFA, respectively, indicating that these are the most photoreactive fractions of DOM. Decreases in Φf and concomitant increases in Φ1O2 in low AMW fractions indicated that chemical transformations occurred, likely including the conversion of phenols to quinones, particularly in SRFA. Results further suggest that the photoactive and fluorescent fractions of DOM are likely independent pools of chromophores from different AMW fractions. In PLFA, a linear response in Φ1O2, specific UV absorbance at wavelength 254 nm (SUVA254), and Φf with ozonation indicated the equal distribution of ozone-reactive moieties.

Metabolomics of small extracellular vesicles derived from isocitrate dehydrogenase 1-mutant HCT116 cells collected by semi-automated size exclusion chromatography.

Cancer-derived small extracellular vesicles (sEVs) are multifunctional particles with a lipid bilayer structure that are involved in cancer progression, such as malignant proliferation, distant metastasis, and cancer immunity evasion. The separation protocol used to isolate sEVs is an important process and thus, several have been developed, including ultracentrifugation (UC), size exclusion chromatography (SEC), and affinity purification using antibodies against sEV surface antigens. However, the effects of different separation methods on sEV components have not been adequately examined. Here, we developed a semi-automated system for collecting sEVs by combining SEC and preparative high-performance liquid chromatography and applied it to metabolome analysis. The developed SEC system could recover sEVs more efficiently and non-destructively than UC, suggesting that it is an appropriate recovery method for metabolic analysis and reflects biological conditions. Furthermore, using the developed SEC system, we performed metabolome analysis of sEVs from isocitrate dehydrogenase 1 (IDH)-mutated human colon HCT116 cells, which produce the oncogenic metabolite, 2-hydroxyglutaric acid (2-HG). IDH1-mutated HCT116 cells released significantly more sEVs than wild-type (WT) cells. The metabolomic profiles of IDH1 mutant and WT cells showed distinct differences between the cells and their sEVs. Notably, in IDH mutant cells, large amounts of 2-HG were detected not only in cells, but also in sEVs. These results indicate that the SEC system we developed has wide potential applications in sEVs research.

Branching analysis of β-cyclodextrin-based poly(N-isopropylacrylamide) star polymers using triple detection SEC

For the first time, poly(N-isopropylacrylamide) (PNIPAAm) star polymers with a β-cyclodextrin core are characterized in detail by size-exclusion chromatography (SEC) with triple detection to experimentally verify the number of arms. A combination of a refractive index detector, multi-angle laser light scattering detector, and an online-viscosimeter was used for branching analysis. At first, the SEC system was calibrated and the detector setup was validated using linear polystyrene reference polymers. The applicability of the established triple detection SEC for branching analysis was shown by the analysis of two commercially available polystyrene star polymers. Due to the high molar masses of the star polymers, both the contraction ratio g and g′ could be determined independently, thus allowing the calculation of the viscosity shielding ratio ε. Finally, the branching analysis of the PNIPAAm star polymers could experimentally confirm the assumed arm number of up to 21 arms. Moreover, an increasingly compact molecular structure and the influence of the arm number on the viscosity shielding ratio could be shown.

Application of Quantum Cascade Laser-Infrared Spectroscopy and Chemometrics for In-Line Discrimination of Coeluting Proteins from Preparative Size Exclusion Chromatography.

An external-cavity quantum cascade laser (EC-QCL)-based flow-through mid-infrared (IR) spectrometer was placed in line with a preparative size exclusion chromatography system to demonstrate real-time analysis of protein elutions with strongly overlapping chromatographic peaks. Two different case studies involving three and four model proteins were performed under typical lab-scale purification conditions. The large optical path length (25 μm), high signal-to-noise ratios, and wide spectral coverage (1350 to 1750 cm–1) of the QCL-IR spectrometer allow for robust spectra acquisition across both the amide I and II bands. Chemometric analysis by self-modeling mixture analysis and multivariate curve resolution enabled accurate quantitation and structural fingerprinting across the protein elution transient. The acquired concentration profiles were found to be in excellent agreement with the off-line high-performance liquid chromatography reference analytics performed on the collected effluent fractions. These results demonstrate that QCL-IR detectors can be used effectively for in-line, real-time analysis of protein elutions, providing critical quality attribute data that are typically only accessible through time-consuming and resource-intensive off-line methods.

Conformational Properties of Flaxseed Rhamnogalacturonan-I and Correlation between Primary Structure and Conformation.

The pectic polysaccharides extracted from flaxseed (Linum usitatissiumum L.) mucilage and kernel were characterized as rhamnogalacturonan-I (RG-I). In this study, the conformational characteristics of RG-I fractions from flaxseed mucilage and kernel were investigated, using a Brookhaven multi-angle light scattering instrument (batch mode) and a high-performance size exclusion chromatography (HPSEC) system coupled with Viscotek tetra-detectors (flow mode). The Mw of flaxseed mucilage RG-I (FM-R) was 285 kDa, and the structure-sensitive parameter (ρ) value of FM-R was calculated as 1.3, suggesting that the FM-R molecule had a star-like conformation. The Mw of flaxseed kernel RG-I (FK-R) was 550 kDa, and the structure-sensitive parameter (ρ) values ranged from 0.90 to 1.21, suggesting a sphere to star-like conformation with relatively higher segment density. The correlation between the primary structure and conformation of RG-I was further discussed to better understand the structure–function relationship, which helps the scale-up applications of pectins in food, pharmaceutical, or cosmetic industries.

Transient Chemical Activation of Covalent Bonds for Healing of Kinetically Stable and Multifunctional Organohydrogels

Transient Chemical Activation of Covalent Bonds for Healing of Kinetically Stable and Multifunctional Organohydrogels

Performance of the new biological small- and wide-angle X-ray scattering beamline 13A at the Taiwan Photon Source.

Recent developments in the instrumentation and data analysis of synchrotron small-angle X-ray scattering (SAXS) on biomolecules in solution have made biological SAXS (BioSAXS) a mature and popular tool in structural biology. This article reports on an advanced endstation developed at beamline 13A of the 3.0 GeV Taiwan Photon Source for biological small- and wide-angle X-ray scattering (SAXS-WAXS or SWAXS). The endstation features an in-vacuum SWAXS detection system comprising two mobile area detectors (Eiger X 9M/1M) and an online size-exclusion chromatography system incorporating several optical probes including a UV-Vis absorption spectrometer and refractometer. The instrumentation and automation allow simultaneous SAXS-WAXS data collection and data reduction for high-throughput biomolecular conformation and composition determinations. The performance of the endstation is illustrated with the SWAXS data collected for several model proteins in solution, covering a scattering vector magnitude q across three orders of magnitude. The crystal-model fittings to the data in the q range ∼0.005-2.0 Å-1 indicate high similarity of the solution structures of the proteins to their crystalline forms, except for some subtle hydration-dependent local details. These results open up new horizons of SWAXS in studying correlated local and global structures of biomolecules in solution.

Unraveling the conformational properties of comb-like Poly(propargyl acrylate)-graft-poly(2-ethyl-2-oxazoline) chains in dilute solutions

We report the preparation and conformational property in solution of a library of comb-like poly(propargyl acrylate)-graft-poly(2-ethyl-2-oxazoline) (PPANb-g-PEtOx47-σg) samples with varied grafting densities (σg) ranging from 0 to 0.68. An azido end-functionalized linear poly(2-ethyl-2-oxazoline) (PEtOx-N3) as grafting side chain with a molar mass of 4700 g mol−1 was synthesized by the living cationic ring opening polymerization (CROP) of 2-ethyl-2-oxazoline (EtOx), followed by the sequential post-polymerization azidation modification at the living chain end of PEtOx. Poly(propargyl acrylate) (PPA) as the backbone was prepared by the chemical transformation from the ATRP-made poly(tert-butyl acrylate) (PtBA). Comb-like PPANb-g-PEtOx47-σg samples with different σg were eventually obtained by grafting PEtOx-N3 onto PPA backbone via the copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) reaction under varied [PEtOx-N3]0/[alkyne]0 ratios. Quadruple-detection size-exclusion chromatography (QD-SEC) system was used to extract the molecular parameters of the obtained comb-like polymers, including molar mass (M), viscometric radius (Rη), and intrinsic viscosity ([η]), etc. The comb-like chain showing a scaling-law of Rη ∼ σg0.34 was confirmed in the shortest backbone, which is fairly accordant with our previous results in polystyrene system. In addition, a transition of polymer shape from star-like to comb-like, and further to branched comb-like structure was observed as the backbone length increases. The transition from star-like to comb-like could be attributed to the continuous increase of length-diameter ratio, which would lead to that the comb-like chain changes its molecular feature from isotropic to anisotropic. On the other hand, the transition from comb-like to branched comb-like should be due to the presence of the intermolecular Glasser-Hay coupling side reactions in comb-like polymers.

Removal Behavior of Protein-like Dissolved Organic Matter During Different Water Treatment Processes in Full-Scale Drinking Water Treatment Plants

Protein-like dissolved organic matter (pDOM), which is ubiquitous in natural waters, is a critical precursor of nitrogenous disinfection byproducts. Recently, the control and elimination of pDOM have been a growing concern during drinking water treatment processes. In this study, a high-performance size exclusion chromatography system coupled with photo-diode array, fluorescence detector, and online organic carbon detector (HPSEC-PDA/FLD/OCD) was used to determine the removal behaviors of different-sized pDOM from two full-scale drinking water treatment plants (DWTPs). Coagulation and activated carbon adsorption were selected for bench-scale experiments to further assess the removal behavior of pDOM during conventional water treatment processes. The results showed that different-sized pDOM fractions exhibited different removal characteristics. Pre-oxidation can effectively remove some tyrosine-like and tryptophan-like components with high MW, and as the oxidization effect was enhanced, more high MW fractions decomposed into low MW ones. Conversely, some aliphatic pDOM fractions in high MW (e.g., aliphatic proteins) were not subject to pre-oxidation removal. The coagulation-sedimentation unit was efficient in removing high MW fractions, specifically tryptophan-like fractions. Additionally, some pDOM components may be released during coagulation. pDOM with low MW and high hydrophobicity were easily removed during activated carbon filtration. However, long-term operation of the activated carbon filter may breed microorganisms, resulting in the partial release of pDOM fractions. Moreover, UV disinfection processes promoted the degradation of low MW pDOM components. Due to the complex water quality and uncontrollable microbial activities, the aforementioned water treatment units did not exhibit a synergistic effect on pDOM removal. In comparison with humic-like substances, pDOM was susceptible to water quality changes, and its removal was limited in the surveyed DWTPs. Therefore, DWTPs must strengthen pDOM monitoring in influent and effluent and adjust the operating parameters of different treatment units in a timely manner. Moreover, the combination of advanced water treatment processes, such as ozone-biological activated carbon process and nanofiltration, should also be considered to strictly control pDOM component removal.

Inhibitory Effects of Pectic Polysaccharide Isolated from Diospyros kaki Leaves on Tumor Cell Angiogenesis via VEGF and MMP-9 Regulation.

Persimmon leaves are an attractive source of phytochemicals with potential health benefits. However, there are only a few reports on the chemical properties and biological activity of the polysaccharide fractions (PLE-I–III) of persimmon leaves. We evaluated the angiogenesis-inhibiting ability of pectic-polysaccharides. The molecular weight of PLEs was determined using a high-performance size-exclusion chromatography system. Tube formation assay of human umbilical vein endothelial cells (HUVECs) was performed using Matrigel-coated 96-well plates. Matrix metalloproteinase (MMP-9), vascular endothelial growth factor (VEGF), PI3K, Akt, and p38 phosphorylation levels were determined using Western blotting; VEGF and MMP-9 transcript levels were measured using SYBR Green qRT-PCR. PLE-I–III significantly inhibited HUVEC tube formation at 12.5 and 25 μg/mL. Among them, PLE-II showed the strongest anti-tube formation activity, and the mRNA/protein expression of angiogenesis-related factors (VEGF/MMP-9) was significantly reduced by PLE-II. PLE-II also suppressed the phosphorylation of PI3K/AKT and p38, JNK, and NF-κB p65 in HUVECs. These results suggest that the polysaccharide PLE-II isolated from persimmon leaves inhibited VEGF and MMP-9 expression in HUVECs via regulation of PI3K/AKT, p38, JNK, and NF-κB p65 signaling pathways.

Moment Equations for Kinetic Study of Intermolecular Interaction by Size Exclusion Chromatography

Abstract New moment equations were developed for size exclusion chromatography (SEC), in which chemical reactions simultaneously take place. It is expected that accurate information about affinity kinetics of intermolecular interactions with no immobilization and no chemical modification of solute and ligand molecules can be obtained from elution peak profiles measured by SEC. Moment equations for the first absolute (μ1A) and second central (μ2C) moment of elution peaks were developed on the basis of the Einstein equation for diffusion and the random walk model in order to analytically determine association (ka) and dissociation (kd) rate constant of intermolecular interactions. They were used to predict chromatographic behavior in hypothetical SEC systems to demonstrate their effectiveness. The influence of some parameters on μ1A and μ2C of elution peaks measured in the SEC systems was quantitatively evaluated. It was indicated that the contributions of axial dispersion and reaction kinetics to μ2C depend on some SEC conditions. It is important to control the SEC conditions so that the reaction kinetics has a predominant contribution to μ2C to determine accurate values of ka and kd. The moment equations are effective for optimizing experimental conditions to accurately analyze intermolecular interactions from kinetic points of view.

Recent advances in the characterization and the treatment methods of effluent organic matter

There are many previous review articles are available to summarize either the characterization methods of effluent organic matter (EfOM) or the individual control treatment options. However, there has been no attempt made to compare in parallel the physicochemical treatment options that target the removal of EfOM from biological treatments. This review deals with the recent progress on the characterization of EfOM and the novel technologies developed for EfOM treatment. Based on the publications after 2010, the advantages and the limitations of several popularly used analytical tools are discussed for EfOM characterization, which include UV-visible and fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), size exclusion chromatography (SEC), and Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS). It is a recent trend to combine an SEC system with various types of detectors, because it can successfully track the chemical/functional composition of EfOM, which varies across a continuum of different molecular sizes. FT-ICR-MS is the most powerful tool to detect EfOM at molecular levels. However, it is noted that this method has rarely been utilized to understand the changes of EfOM in pre-treatment or post-treatment systems. Although membrane filtration is still the preferred method to treat EfOM before its discharge due to its high separation selectivity, the minimum requirements for additional chemicals, the ease of scaling up, and the continuous operation, recent advances in ion exchange and advanced oxidation processes are greatly noteworthy. Recent progress in the non-membrane technologies, which are based on novel materials, are expected to enhance the removal efficiency of EfOM and even make it feasible to selectively remove undesirable fractions/compounds from bulk EfOM.

Enhanced Intestinal Immune Response in Mice after Oral Administration of Korea Red Ginseng-Derived Polysaccharide.

(1) Background: The immunostimulatory role of the polysaccharide fraction (KRG-P) of Korea red ginseng (KRG) was studied in cells. However, its immunomodulatory activity is unknown. Therefore, we investigated the chemical properties of KRG-P and its intestinal immune responses in vitro and in vivo. (2) Methods: KRG-P monosaccharide composition and molecular weight were determined using high-performance liquid and size-exclusion chromatography systems. Immunoglobulin A (IgA) and α-defensin-1 transcript levels were measured using a SYBR Green qRT-PCR; defensin-1, Granulocyte-macrophage colony-stimulating factor (GM-CSF), and IgA protein levels were determined using Western blotting and ELISA kits. (3) Results: The molecular weight of KRG-P was estimated to be 106 kDa, and it contained neutral sugar (74.3%), uronic acid (24.6%), and proteins (1%). In vitro studies of intestinal immunomodulatory activity of KRG-P indicated that GM-CSF and IgA levels increased in Peyer’s patch cells to higher levels than those obtained with KRG and induced bone marrow cell proliferation. In in vivo study, oral KRG-P administration to mice upregulated the expression of α-defensin-1 and IgA in the small intestinal tissue and that of secreted IgA in the feces. (4) Conclusions: KRG-P contributed to the modulation of intestinal immunity and maintenance of intestinal homeostasis against intestinal infection.

Characterization of Recovered Polyvinylchloride by Size Exclusion Chromatography and Triple Detectors Technique

Polyvinyl chloride (PVC) is an indispensable compound that accounts for 66% of the water distribution infrastructure and 75% of sanitary sewer pipe applications in the U.S.A. In this study PVC resin was recovered by solvent extraction from a postconsumer PVC pipe. The recovered PVC (PVC-R) was characterized by a multi-detector size exclusion chromatography system eluted with tetrahydrofuran (THF) at 30 °C. The values of the Mark-Houwink-Kuhn-Sakurada (MH) parameters of the PVC-R were obtained by averaging three replicable experiments and the results were comparable with the reported values of pure PVC. The Stockmayer-Fixman plot of the PVC-R in THF had a curved shape which is due to the notorious tendency of the PVC molecules to remain partly associated in supermolecular aggregates even if the PVC is dissolved in a good solvent. As a results, the unperturbed molecular dimension, of the PVC-R was dependent on a function of the excluded volume, z, where the z2 coefficient was not zero. The obtained value of the of PVC-R, having a = 87 kDa and = 1.41, was 8.19 × 10−9 (cgs), comparable with the reported value for pure industrial PVCs in THF, 6.4 kDa < < 650 kDa at 25 °C, 8.17 × 10−9 (cgs) and in benzyl alcohol, an ideal solvent, at 155.4 °C, 40 kDa < < 350 kDa, 8.20 × 10−9 (cgs). The comparison of the results showed that the PVC-R had similar characteristics to the industrial PVC reported in the published literature, and hence can be reused as a resin for the manufacturing of PVC commodities.

High-Throughput Tertiary Amine Deoxygenated Photopolymerizations for Synthesizing Polymer Libraries.

The huge chemical space potential of synthetic polymers means that in many studies only a small parameter range can be realistically synthesized in a short time and hence the “best” formulations may not be optimum. Throughput is traditionally limited by the need for deoxygenation in radical polymerizations, but advances in photopolymerization now provide opportunities for “in-air” polymerizations. Here, we have developed a protocol using liquid handling robots (or multichannel pipettes) with blue light photolysis of reversible addition fragmentation chain transfer agents and tertiary amine deoxygenation to enable the synthesis of polymer libraries in industry-standard 96-well plates with no specialized infrastructure and no degassing step. The roles of solvents and amine deoxygenators are explored to optimize the polymerization, particularly to look at alternatives to dimethyl sulfoxide (DMSO) for hydrophobic monomer (co)polymerization. DMSO is shown to aid the degassing process but is not easy to remove and hence prevents isolation of pure polymers. In contrast, using dioxane in-plate evaporation or precipitation of the tertiary amine allowed isolation of polymers in-plate. This removed all reaction components yielding pure polymers, which is not easily achieved with systems using metal catalysts and secondary reductants, such as ascorbic acid. As an example of the throughput, in just under 40 h, 392 polymers were synthesized and subsequently analyzed direct from plates by a 96-well plate sampling size exclusion chromatography system to demonstrate reproducibility. Due to less efficient degassing in dioxane (compared to DMSO), the molecular weight and dispersity control were limited in some cases (with acrylates giving the lowest dispersities), but the key aim of this system is to access hundreds of polymers quickly and in a format needed to enable testing. This method enables easy exploration of chemical space and development of screening libraries to identify hits for further study using precision polymerization methods.

Extraction and purification of NUDT9 homology domain of human transient receptor potential melastatin 2 channel

To develop methods of extraction and purification of Cterminal NUDT9 homology domain of human transient receptor potential melastatin 2 (TRPM2) channel. After sonication and centrifuge of Escherichia coli strain Rosetta (DE3) which was induced by isopropylthio-β-D-galactoside, GST-NUDT9-H was collected after the binding of supernatant with GST beads and eluted with reduced glutathione. Then the elution buffer containing fusion protein was purified by size exclusion chromatography after concentration and centrifuge. Finally, with the cleavage of thrombin and binding with the GST beads, NUDT9-H with high purity in supernatant was collected. The GST-NUDT9-H fusion protein was stabilized with lysis buffer containing 0.5% n-dodecyl -β-d-maltoside (DDM), and wash buffer containing 0.025% DDM in size-exclusion chromatography system, and finally the NUDT9-H with high purity was obtained after cleaved by thrombin (1 U/2 mg fusion protein) for 24 h. Due to the poor stability of NUDT9-H, it is necessary to add DDM in extraction and purification buffer to stabilize the conformation of NUDT9-H, so as to increase its yields and purity.

Low molecular weight dextran production by Leuconostoc mesenteroides strains: Optimization of a new culture medium and the rheological assessments

Strains belonging to genus Leuoconostoc mesenteroides are able to produce dextran exo-polysaccharide. In this study, MRS broth and milk permeate were used for growth of three strains (NRRL B-512F, NCIB 8023 and NRRL B-512) of L. mesenteroides and the growth rate, dextran production, and its rheological properties were studied. Evaluation of molecular weight by high-performance size exclusion chromatography system showed that dextran produced in milk permeate had a lower molecular weight (<10000 Dalton) compared to the dextran produced in MRS broth (<40000 Dalton). The viscosity of dextran solution (2%) produced in MRS was 0.005–0.01 Pa.s while in the synthetic medium it was <0.005 Pa.s. Also in our study maximum ratio of growth factor and dextran yield belonged to NRRL B-512F, which was subjected to optimization of fermentation condition for dextran production. For optimization, response surface methodology by using sucrose, milk permeate and yeast extract in 5 levels were used. According to experiments, optimum concentrations for sucrose, milk permeate, and yeast extract were found to be 20, 15, and 15 (g/l), respectively.