Weight-average Molecular Mass Research Articles

Ring-ring equilibration (RRE) of cyclic poly(L-lactide)s by means of cyclic tin catalysts

With 2,2-dibutyl-2-stanna-1,3-dithiolane (DSTL) and 2-stanna-1,3-dioxa-4,5,6,7-dibenzoxepane (SnBiPh) as catalysts ring-expansion polymerizations (REP) were performed either in 2 M solution using three different solvents and two different temperatures or in bulk at 140 and 120 °C. A kinetically controlled rapid REP up to weight average molecular masses (Mẃs) above 300 000 was followed by a slower degradation of the molecular masses at 140 °C, but not at 120 °C Furthermore, a low molecular mass cyclic poly(L-lactide) (cPLA) with a Mn around 16 000 was prepared by polymerization in dilute solution and used as starting material for ring-ring equilibration at 140 °C in 2 M solutions. Again, a decrease of the molecular mass was detectable, suggesting that the equilibrium Mn is below 5 000. The degradation of the molecular masses via RRE was surprisingly more effective in solid cyclic PLA than in solution, and a specific transesterification mechanism involving loops on the surface of crystallites is proposed. This degradation favored the formation of extended-ring crystallites, which were detectable by a “saw-tooth pattern” in their MALDI mass spectra.

Synthesis of pyrene and pyrrole-appended fluorescent turn-off sensor toward Cr(VI) detection: Chemical oxidative and electrochemical polymerization of carboxamide

A carboxylic amide compound containing pyrrole and pyrene groups, referred to as PP, was synthesized and characterized for its structural, optical, and electrochemical properties. Upon excitation with 320 nm light, PP displayed blue emission at 387 nm, which was found to be quenched due to chelate formation in the presence of Cr(VI). Conducted competition experiments involving chloride salts of Ag+, Al3+, Cd2+, Co2+, Cr3+, Fe3+, Hg2+, K+, Mn2+, Ni2+, Pb2+, Sn2+, and Zn2+ demonstrated the notable selectivity of compoundPP towards Cr(VI)ions. This selectivity was evidenced by a pronounced turn-off fluorescent effect, attributed to a chelation-enhanced quenching (CHEQ) mechanism by the formation of 1:2 chelation between Cr(VI) and the ligand PP. Moreover, addition of EDTA toPP– Cr(VI)chelation recovered the fluorescence offering receptorPPas a reversible sensor. The PP probe demonstrated remarkable selectivity in detection Cr(VI)ions among various metallic ions, displaying a limit of detection (LOD) value of 0.106 µM. Chemical oxidative and electropolymerization methods were employed to synthesize two distinct polymers, namely Poly(PP)-O and Poly(PP)-E, respectively. The electropolymerization of PP was carried out in 0.1 M TBAF6P serving as a supporting electrolyte solution, while oxidative polymerization was conducted in the presence of FeCl3. Mass average molecular weight of the oxidative polymerization product was 5200 Da, as determined by GPC analysis. Thermal characterization was performed via TG-DTA-DTG curves. The electropolymerization product of PP coated on the ITO surface was further characterized by SEM.

Fractionation of Arctic Brown Algae (Fucus vesiculosus) Biomass Using 1-Butyl-3-methylimidazolium-Based Ionic Liquids.

Arctic brown algae are considered a promising industrial-scale source of bioactive sub-stances as polysaccharides, polyphenols, and low-molecular secondary metabolites. Conventional technologies for their processing are focused mainly on the isolation of polysaccharides and involve the use of hazardous solvents. In the present study a "green" approach to the fractionation of brown algae biomass based on the dissolution in ionic liquids (ILs) with 1-butil-3-methylimidazolium (bmim) cation with further sequential precipitation of polysaccharides and polyphenols with acetone and water, respectively, is proposed. The effects of IL cation nature, temperature, and treatment duration on the dissolution of bladderwrack (Fucus vesiculosus), yields of the fractions, and their chemical composition were studied involving FTIR and NMR spectroscopy, as well as size-exclusion chromatography and monosaccharide analysis. It was shown that the use of bmim acetate ensures almost complete dissolution of plant material after 24 h treatment at 150 °C and separate isolation of the polysaccharide mixture (alginates, cellulose, and fucoidan) and polyphenols (phlorotannins) with the yields of ~40 and ~10%, respectively. The near-quantitative extraction of polyphenolic fraction with the weight-average molecular mass of 10-20 kDa can be achieved even under mild conditions (80-100 °C). Efficient isolation of polysaccharides requires harsh conditions. Higher temperatures contribute to an increase in fucoidan content in the polysaccharide fraction.

A different approach to estimate air moisture

When comparing dry and humid air densities and trying to understand which one is denser, the right answer not necessarily follows our intuition. This happens in the Environmental Engineering lectures when students are asked: Is dry or humid air denser? To understand the role of water vapor in air, a method to compute the mass mixing ratio, specific humidity and average molecular weight is presented. This set of equations is more precise than the traditional method and clarifies how water vapor influences physical properties such as air density and bulk molecular weight.

Surface Modification of Kraft Lignin by Mechanochemical Processing with Sodium Percarbonate.

In this article, we present a novel one-pot mechanochemical reaction for the surface activation of lignin. The process involves environmentally friendly oxidation with hydrogen peroxide, depolymerization of fractions with high molecular mass, and introduction of new carbonyl functions into the lignin backbone. Kraft lignin was ground with sodium percarbonate and sodium hydroxide in a ball mill at different time intervals. Analyses by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR), size exclusion chromatography (SEC), dynamic vapor sorption (DVS), and small-angle X-ray scattering (SAXS) showed significant improvements. After only 5 min of reaction, there was a 47% reduction in mass-average molecular weight and an increase in carboxyl functionalities. Chemical activation resulted in an approximately 2.8-fold increase in water adsorption. Principal component analysis (PCA) provided further insight into the correlations between IR spectra and SAXS parameters.

Synthesis, photophysical, electrochemical and morphological properties of a novel cross-linked chitosan-based fluorescent polymer: A fluorescence sensor for single-stranded DNA

This report details the first-time use of the perylene-3,4,9,10-tetracarboxylic dianhydride as a cross-linker to synthesize a novel fluorescent, chitosan-based cross-linked polymer (3). The polymer has single-stranded DNA (ssDNA) binding properties that can be used in sensor production for detecting salmon sperm DNA. Chitosan polymer's solubility is poor and restrictedto only acidic media. In contrast, this new fluorescent chitosan polymer was soluble in various organic solvents and aqueous solutions at different pHs. Its absorption, photophysical, electrochemical and morphological properties were investigated in detail. Gel permeation chromatography determined the weight average molecular mass (Mw) of polymer 3 as 21300 g/mol. Seventeen hydrophobic perylene units were determined in the cross-linked network. The energy levels of the highest occupied molecular orbitals and lowest unoccupied molecular orbitals of the new polymer 3 were calculated as −6.24 and −3.96 eV, corresponding to the band gap of 2.28 eV. Fluorescence and ultraviolet spectroscopy techniques were used to study the interaction between ssDNA and polymer 3. The interaction pointed to the intercalative mode, and the cross-linked chitosan can be used as a stable and sensitive platform for ssDNA detection. These results show a new class of organic biopolymers that could yield promising potential in many biomedical applications.

Research on modifying of recycling polyol from waste polyurethane foam by vegetable oil for producing insulation materials

Polyurethane (PU) foam is formed by the condensation of 2 components Polyol and Isocyanate. PU foam waste can be recycled by glycolysis which decomposes the polymer chains into polyol. The recycled polyol can then be used as the material to make new PU foam. However, the recycled Polyol is mixed with unprofitable primary and secondary amines, and it is not suitable for use as a raw material for the production of insulating foam because of its small average molecular weight, high hydroxyl index, etc. In this study, recycled Polyol will be modified with vegetable oil for the purpose of removing the amines mentioned above, creating the product with basic properties like commercial Polyol. Research results show that the regenerated Polyol after modification has the low hydroxyl index of 423.5 mg KOH/g and the viscosity of 4400 mPa.s, which are quite similar to that of commercial Polyol and the mass average molecular weight (2440.6) much higher than regenerated polyol.

Synthesis and Characterization of Poly(hydroxy)urethane from Polyols for Beech (Fagus sylvatica) Wood Impregnation

A non-isocyanate route of polyurethane synthesis based on polyol (xylitol, sorbitol, glycerol, and PG3), alkyl carbonate (DMC and DEC), and diamine (HMDA, EDA, and DETA) was conducted for wood impregnation through in-site polymerization. The structure and mass average molecular weight (Mw) of the polyurethanes were analyzed using FTIR, NMR, and SEC. According to the results, polyurethane synthesis by a two-pot method in water brought cyclic carbonate degradation. The distribution of Mw of the polyurethanes showed that the most satisfying polymer (4380 g/mol) was prepared without solvent. Polyurethanes synthesized in methanol have a higher Mw than that in distilled water. In the same solvent, the use of HMDA resulted in a polymer with higher Mw than that of EDA. One-step wood impregnation in a solvent gave unsatisfactory WPG (12.59–19.71%) and LC (50.36–62.80%). However, one-step impregnation without solvent gave a higher WPG (78.39–87.63%) and a lower LC (19.11–21.25%). It is not feasible to be applied industrially. The two-step impregnation gave WPG (14.89-30.73%) and LC (42.22–56.52%). Wood impregnation using methanol or ethanol as the solvent was more recommended than using an aqueous solution. However, the resistance against leaching needs improvement. Keywords: Alkyl carbonate, diamine, polyol, polyurethane, wood impregnation

Remarkable improvement in the storage stability of maltodextrin through 1,4-α-glucan branching enzyme modification

Enzymatic modification is a potential approach to effectively improve the stability of maltodextrin for food and industrial applications. In this study, a 1,4-α-glucan branching enzyme from Rhodothermus obamensis STB05 (Ro-GBE) was used to modify maltodextrin. The transparency of the Ro-GBE-modified maltodextrin prepared under the optimal modification conditions: enzyme dosage of 100 U/g, reacting time of 12 h at 55 °C, and pH of 7.0, was maintained above 90% for over 30 days. In addition, the viscosity stability, retrogradation property, and freeze–thaw stability were significantly improved. Because of the constant value of the dextrose equivalent (DE), increase in α-1,6-glycosidic linkage ratio, and decrease in weight-average molecular mass (Mw), we believed that the glycosidic bond rearrangement played a vital role in the Ro-GBE modification. Moreover, Ro-GBE exhibited high specificity in cleaving long chains with DP ≥ 15 and transferring the released chains as exterior chains to form a short-clustered structure. Pearson correlation analysis revealed that the transparency stability of maltodextrin mainly correlated with the branching degree, while the viscosity stability, retrogradation property, and freeze–thaw stability mainly contributed to the Mw of branched molecules.

Biomechanical Behaviors and Degradation Properties of Multilayered Polymer Scaffolds: The Phase Space Method for Bile Duct Design and Bioengineering.

This article reports the electrospinning technique for the manufacturing of multilayered scaffolds for bile duct tissue engineering based on an inner layer of polycaprolactone (PCL) and an outer layer either of a copolymer of D,L-lactide and glycolide (PLGA) or a copolymer of L-lactide and ε-caprolactone (PLCL). A study of the degradation properties of separate polymers showed that flat PCL samples exhibited the highest resistance to hydrolysis in comparison with PLGA and PLCL. Irrespective of the liquid-phase nature, no significant mass loss of PCL samples was found in 140 days of incubation. The PLCL- and PLGA-based flat samples were more prone to hydrolysis within the same period of time, which was confirmed by the increased loss of mass and a significant reduction of weight-average molecular mass. The study of the mechanical properties of developed multi-layered tubular scaffolds revealed that their strength in the longitudinal and transverse directions was comparable with the values measured for a decellularized bile duct. The strength of three-layered scaffolds declined significantly because of the active degradation of the outer layer made of PLGA. The strength of scaffolds with the PLCL outer layer deteriorated much less with time, both in the axial (p-value = 0.0016) and radial (p-value = 0.0022) directions. A novel method for assessment of the physiological relevance of synthetic scaffolds was developed and named the phase space approach for assessment of physiological relevance. Two-dimensional phase space (elongation modulus and tensile strength) was used for the assessment and visualization of the physiological relevance of scaffolds for bile duct bioengineering. In conclusion, the design of scaffolds for the creation of physiologically relevant tissue-engineered bile ducts should be based not only on biodegradation properties but also on the biomechanical time-related behavior of various compositions of polymers and copolymers.

Molecular structures of high- and low-methoxy water-soluble polysaccharides derived from peas and their functions for stabilizing milk proteins under acidic conditions

The structural and functional properties of two different pea water-soluble polysaccharides, a high methyl-esterified (HM-SPPS; degree of methyl esterification (DMe): 71.0 %) and low methyl-esterified SPPS (LM-SPPS; DMe: 25.2 %) were investigated. The two extracts did not vary in composition and showed a weight average molecular mass of about 1,000 kDa, as measured by size exclusion chromatography equipped with a multi-angle light scattering detector. Both HM-SPPS and LM-SPPS had similar sugar compositions, with arabinose 42.2–47.1 %, glucose 26.6–31.0 %, and galacturonic acid 17.5–18.0 %, as their main sugars. Their charge varied as a function of pH. The molecular structure was observed by a scanning probe microscope and showed a straight chain structure with small branches. The structure was similar to that already reported for polysaccharides from kidney bean. SPPS molecules interact with acidified milk protein particles at pH < 4.4. There were differences between the two SPPS. LM-SPPS could stabilize a model acidified milk dispersion with minimal aggregation between pH 3.6–4.4, while HM-SPPS showed the presence of bridging flocculation caused by polysaccharide’s entanglements. It was concluded that SPPS stabilizes acidified protein by steric and electrostatic repulsion

The effect of three pectin fractions variation on the browning of different dried apple products

Pectin is an important active polysaccharide in the matrix of dried fruit slices. Its components and structural character not only affect the texture but also impact the color of the dried fruit products. Present work studied the variation of pectin fractions of water-soluble (WSP), trans-cyclohexane-1,2-diaminetetraacetic acid-soluble (CSP), and sodium carbonate-soluble (NSP) from apple slices dried by using freeze-drying (FD), 60 °C hot air drying (HAD60), and 90 °C hot air drying (HAD90), to investigate the correlation of their monosaccharide composition, molecular weight distribution, Fourier transform infrared (FTIR) spectrum and small-angle X-ray scattering (SAXS) intensity plot of pectin fractions with the appearance browning of the apple slices. It was found that thermally process ruptures the cell wall structure and pectin component, leading to 12.57% less yield of WSP, and a maximum of 6.35% more yield of NSP pectin fractions. In FD, HAD60, and HAD90 apple slices, the linearity of WSP decreased but the branching extent of the rhamnogalacturonan I (RG-I) domain of WSP and NSP increased successively. The weight average molecular mass (Mw) and number average molar mass (Mn) of WSP and NSP increased as drying temperature increased, whereas they decreased in CSP. The thermal treatment promoted the dehydration of the pectin and caused higher methyl esterification, inducing the structure of pectin more compact and tighter. Moreover, the pectin structural characteristics of the degree of esterification (DE), the radius of gyration (Rg) value, conformational index ( ν ), and galactose content of three soluble pectin fractions were positively correlated with the a* and b* value of different dried apple slices. • Different drying techniques induce different changes in three pectin fractions. • The change of pectin fractions notably impacts the browning of dried apple slices. • Thermal treatment induced methyl esterification of pectin fractions of dried apple. • Thermal treatment made the structure of pectin much more compact and tighter.

Changes of Ca forms and chelate-soluble pectin in cherry tomatoes treated with ultrasound and calcium lactate

The physicochemical properties, polygalacturonase and pectin methylesterase activity, calcium form, and structure of chelate-soluble pectin (CSP) in cherry tomatoes were studied. The total calcium and CSP contents for calcium with ultrasound assisted treatment (U + Ca) group were the highest at the end of storage. U + Ca improved the calcium content from 0.6486 g/kg to 07198 g/kg, and enhanced the permeation of Ca2+ into cell walls. Compared to control (CK), ultrasound (U) and calcium (Ca) groups, the fruit firmness of U + Ca group maintained at high level throughout the storage process. Soluble solids content of all groups had no significant difference at the end of storage. Titratable acidity of cherry tomatoes in U + Ca group was higher than that in CK and U groups at day 30. According to CSP structure analysis, its main configuration had no obvious change at the end of storage. Atomic force microscopy and weight average molecular mass analyses confirmed that U + Ca delayed the degradation of CSP. Our results indicated that U + Ca has application potential in maintaining the quality of cherry tomatoes during storage.

Effect of ultrasonic pretreatments on the characteristics of pectin extracted from Salustiana orange cultivated in Argentina

AbstractThe use of direct and indirect ultrasound pretreatments was evaluated for the extraction of pectin enriched fractions with citric acid (pH 2.3, 85°C) from the albedo and pulp of Salustiana orange. The extractive method that produced the highest yield was the one involving a pretreatment with direct high‐power ultrasound (HPUS) (41 g isolated fraction/100 g albedo CM versus 30 g isolated fraction/ 100 g albedo CM for indirect treatment; 39 g isolated fraction/100 g pulp CM versus 26 g isolated fraction/100 g pulp CM for indirect treatment) and allowed extracting the highest amount of pectin from both albedo and pulp. The major neutral sugars found in all fractions were arabinose, galactose, and rhamnose. Pectins were obtained with weight average molecular masses of 566–729 kDa from the albedo and 663–739 kDa from the pulp. All fractions gelled in the presence of sucrose at acidic pH. Pretreatment with HPUS gave origin to the least elastic gels (albedo: G′ higher than 100 Pa, G″ higher than 20 Pa. Pulp: G′ higher than 70 Pa, G″ higher than 25 Pa), while indirect US produced fractions that formed more elastic gels (albedo: G′ higher than 1000 Pa, G″ higher than 250 Pa. Pulp: G′ higher than 500 Pa, G″ higher than 100 Pa). Ultrasound pretreatments allowed obtaining a variety of pectin enriched fractions with interesting characteristics for food formulation.Practical applicationsPectins are widely used as texture modifiers in the food industry. Commercial pectins are commonly obtained from waste from the citrus juice industry, using mineral acids at high temperatures, producing large amounts of polluting effluents. The study of the use of organic acids in combination with clean technologies such as ultrasound, which allow higher pectin yields to be obtained through less polluting processes, is of great interest as an environmentally friendly alternative. Likewise, it is important to demonstrate that the pectins obtained through such technologies are effectively useful for the industry as texture modifying additives. In this work it is proposed to study the effect of the use of indirect and direct ultrasound as pretreatments in the extraction with citric acid of Salustiana orange pectin.

Structural characterization and immunoregulatory activity of a neutral polysaccharide from the roots of Apocynum venetum L.

The structural characteristics and immunoregulatory activities of neutral heteropolysaccharide (AVRP-N) separated from the roots of Apocynum venetum L. were extensively investigated. The results showed that the weight average molecular mass (Mw) of AVRP-N was 6.430 × 103 Da. Moreover, the backbone is composed of natural acetylated (1 → 4)-β-D-Man and (1 → 5)-α-L-Ara domains. The mannan is composed of →4)-β-D-Manp-(1→, →4)-β-D-Glcp-(1→, and the terminal group α-D-Galp-(1→ attached to →4,6)-β-D-Manp-(1→ at O-6. Araban is composed of →5)-α-L-Araf-(1→; the terminal group α-L-Araf-(1→attached to→2,3,5)-α-L-Araf-(1→ at O-2, O-3 and →3,5)-α-L-Araf-(1→ at O-3. In addition, the senior structure shows that AVRP-N has a triple-helix conformation. Furthermore, AVRP-N exhibited immunomodulatory effects, which could significantly regulate the proliferation of mouse splenic lymphocytes by enhancing the secretion of the cytokines (IFN-γ, IL-2, IL-4, and IL-10). Our results provide new structural and immunoregulatory information for natural polysaccharides derived from Apocynum venetum L.

The impact of varying dextran oxidation levels on the inhibitory activity of a bacteriocin loaded injectable hydrogel

In the design of injectable antimicrobial dextran-alginate hydrogels, the impact of dextran oxidation and its subsequent changes in molecular weight and the incorporation of glycol chitosan on (i) gel mechanical strength and (ii) the inhibitory profile of an encapsulated bacteriocin, nisin A, are explored. As the degree of oxidation increases, the weight average molecular mass of the dextran decreases, resulting in a reduction in elastic modulus of the gels made. Upon encapsulation of the bacteriocin nisin into the gels, varying the dextran mass/oxidation level allowed the antimicrobial activity against S. aureus to be controlled. Gels made with a higher molecular weight (less oxidised) dextran show a higher initial degree of inhibition while those made with a lower molecular weight (more oxidised) dextran exhibit a more sustained inhibition. Incorporating glycol chitosan into gels composed of dextran with higher masses significantly increased their storage modulus and the gels’ initial degree of inhibition.Graphical abstract

Evaluation of Bookkeeper mass deacidification based on historical book papers

Bookkeeper, the most widely used deacidification process based on MgO particles, was systematically evaluated on two sets of nonvaluable historical paper samples. Established analytical methods, such as pH and alkaline reserve determination, were used, as well as SEM EDS analyses to evaluate the distribution of Mg-rich particles on the paper surface and in the cross-section of the paper. The degradation rate constants of untreated and deacidified paper samples after accelerated thermal degradation were calculated based on weight average molecular mass determination to evaluate the lifetime extension of paper. The efficiency factors determined after accelerated thermal degradation of untreated and treated paper showed that paper lifetime prolongation after Bookkeeper deacidification treatment is highly limited for most of the investigated paper samples. No correlation was found between the alkaline reserve content or the pH and the degradation rate constants of the deacidified paper samples, but the paper degradation rate correlated with the paper samples pH before deacidification treatment. SEM EDS analysis showed that Mg-rich particles remained on the paper surface, which explains the limited effectiveness of the treatment.Graphical abstract

Assessing the Hydrodynamic Effect on the Molecular Parameters of the Isoprene Polymerization Product in the Presence of a Neodymium-Based Catalytic System.

The paper presents findings on the kinetic regularities of polyisoprene production in the presence of neodymium-based catalytic systems for large-scale production processes. A mathematical model has been developed for batch and continuous isoprene polymerization. The study identified dependences of changes in the number-average and mass-average molecular weight of the resulting product on the length of the applied reactor cascade under continuous static operation. The description of the continuous production mode leads to the necessity of analyzing the structure of the flows by means of the distribution functions of the residence time in the reactor, which is the basis for the formation of a block of modules of the hydrodynamic level. A change in the length of the reactor cascade leads to a change in the residence time of particles in the reactor and, consequently, to a change in the hydrodynamic regime. With the help of mathematical modeling tools, the influence of the hydrodynamic regime in the reaction zone on the molecular weight distribution of the resulting product is revealed.

Purification, characterisation and antioxidant properties of a novel polysaccharide from Physalis pubescens L. fruits

SummaryConsidering the medicinal and edible properties of Physalis pubescens L. fruit, the plant has a long history of cultivation in China. In the current study, a novel polysaccharide (PPL‐1) was successfully obtained from P. pubescens fruits using multi‐column techniques. The chemical characterisation of the polysaccharide was achieved by acid hydrolysis, determination of weight average molecular mass, thermogravimetric and Smith degradation analyses, in addition to ultraviolet, Fourier transform infrared spectroscopy, one‐ and two‐dimensional nuclear magnetic resonance spectroscopy. According to the structural analyses, PPL‐1 consisted of rhamnose, arabinose, fructose, mannose and glucose with a relative molar ratio of 0.39:0.12:0.02:0.03:0.44. The average molecular weight of PPL‐1 was 7.3 kDa and it was mainly composed of (1 → 3) and (1 → 6) linkages. PPL‐1 exhibited not only scavenging effects on 2,2‐diphenyl‐1‐picrylhydrazyl and 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) free radicals but also hydrogen peroxide‐induced oxidative stress in SH‐SY5Y cells effectively by decreasing malondialdehyde content and increasing total antioxidant capacity, superoxide dismutase and glutathione peroxidase activity levels.

Purification and characterization of dextranase from Penicillium cyclopium CICC-4022 and its degradation of dextran

A dextranase was purified from Penicillium cyclopium CICC-4022 by ammonium sulfate fractionation and secondary tangential flow filtration, and the enzymatic properties were studied. The purified dextranase was used to regulated the molecular mass and homogeneity of dextran. Weight-average molecular mass (Mw) and polydispersity index (Mw/Mn) of dextran were measured by gel permeation chromatography (GPC) coupled with a triple-detector array (GPC-TDA), which is composed of a multiple-angle light scattering, a viscometer, and a refractive-index detector. The dextranase was purified by 2.24-fold, the recovery rate was 45.84%, the specific activity was 1442.05 U/mg, and the Mw was 77 KDa. Dextranase showed maximum activity at pH of 5.0 and 55 °C. Na+, K+ and NH4+ can effectively improve the dextranase activity, Cu2+ and Pb2+ can strongly inhibit the dextranase activity. Dextranase specifically degraded the α-1,6 glycosidic bonds of dextran. By controlling the dextranase activity, substrate concentration, and time, the specific Mw dextran with good homogeneity was obtained. The structure of dextran was not altered before or after dextranase hydrolysis, but its conformation changed from a spherical chain to a compliant chain. When the Mw of the dextran product was about 5 KDa, it was a compact spherical chain conformation in solution.