Limits...
The preparation and characterization of a novel sphingan WL from marine Sphingomonas sp. WG

View Article: PubMed Central - PubMed

ABSTRACT

Sphingans, a group of structurally closely related bacterial exopolysaccharides produced by members of the genus Sphingomonas, can be applied in a variety of industries such as food, cement, and personal care applications due to their high viscosity. A high sphingan-producing-bacterium, Sphingomonas sp. WG can secret large quantity of sphingan designated as WL. To enhance the production of WL, a three-stage control strategy was applied and the highest WL production can reach 33.3 g/L. The rheological analysis showed that the aqueous solution of WL had high viscosity, typical shearing-thinning behavior and great stability to high temperature, a wide range of pH (1 to 14), and high salinity. WL was composed principally of carbohydrate with 6.52% O-acyl groups. The carbohydrate portion of WL contained about 13% glucuronic acid and some neutral sugars including mannose, glucose and rhamnose in the molar ratio of 1:2.28:2.12. Partial acid hydrolysis of WL produced a new oligosaccharide WL-1. Structural resolution revealed that WL-1 consisted of α-L-Rha-(1→4)-β-L-Rha-(1→4)-β-D-Glc-(1→3)-α-D-Glc with β-D-Man substituent at the third glucose residue and carboxyl and O-acyl groups. These findings will broaden the applications of this novel sphingan in food, ink, oil and other industries.

No MeSH data available.


Rheological property analysis of crude WL solution.(a) The viscosity of different concentrations of WL solution under different shear rates. (b) The effect of temperature on the viscosity of WL solution of different concentrations (0.2%, 0.6%, and 1.0% (w/v)). (c) The effect of pH (1–14) on the viscosity of 0.8% (w/v) WL solution (25 °C). (d) The effect of different concentrations of NaCl and CaCl2 (0-10%) on the viscosity of 0.8% (w/v) WL solution (25 °C).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5121650&req=5

f3: Rheological property analysis of crude WL solution.(a) The viscosity of different concentrations of WL solution under different shear rates. (b) The effect of temperature on the viscosity of WL solution of different concentrations (0.2%, 0.6%, and 1.0% (w/v)). (c) The effect of pH (1–14) on the viscosity of 0.8% (w/v) WL solution (25 °C). (d) The effect of different concentrations of NaCl and CaCl2 (0-10%) on the viscosity of 0.8% (w/v) WL solution (25 °C).

Mentions: Rheological properties of WL solution were measured. As shown in Fig. 3a, an enhancement of viscosity with WL concentration at the same shear rate was observed. As welan gum and other sphingans2, all WL solutions showed a typical non-Newtonian pseudoplastic behavior or a strong shearing-thinning behavior. The viscosity of all solutions decreased when the shear rate increased and the degree of shear thinning was markedly increased as concentration of WL solution increased. This behavior may be due to the orientation or deformation of macromolecular network in the direction of flow caused by the shearing of EPS solution15. Furthermore, WL solutions exhibited good stability under diverse conditions including high temperature, wide range of pH and high concentration of salts (Fig. 3b–d). The viscosity of WL solutions at different concentrations (0.2%, 0.6% and 1.0%) showed little changes when the temperature increased from 30 °C to 100 °C, indicating that WL had good thermal stability. The viscosity of WL solution maintained at a high level in the range of pH 1–14. Compared with the highest viscosity, the lowest viscosity of WL solution decreased about 13% at pH 1. Generally, the repulsive interactions of anionic groups along the backbone of EPS chain lead to the high viscosity of EPS. However, when salts were added, cations with the opposite charge shielded the charge-charge repulsions, which resulted in a decrease in viscosity and even phase separation1516. Interestingly, our results showed that the salts had minor effect on its viscosity. The viscosity of the WL solution exhibited a little increase when NaCl (2 to 4%) or CaCl2 (2 to 8%) was added to the broth. When supplemented with 2% (w/v) CaCl2, the apparent viscosity of WL solution was increased by 9%. When the concentration of salts further increased, the viscosity decreased slightly and remained 90 and 86% when 10% (w/v) NaCl and CaCl2 was added, respectively. These results showed that the WL was of good salt resistance and this might be caused by the good hydrophilicity of main chain structure of EPS that made the space structure stable even when the charge of the EPS was shielded16.


The preparation and characterization of a novel sphingan WL from marine Sphingomonas sp. WG
Rheological property analysis of crude WL solution.(a) The viscosity of different concentrations of WL solution under different shear rates. (b) The effect of temperature on the viscosity of WL solution of different concentrations (0.2%, 0.6%, and 1.0% (w/v)). (c) The effect of pH (1–14) on the viscosity of 0.8% (w/v) WL solution (25 °C). (d) The effect of different concentrations of NaCl and CaCl2 (0-10%) on the viscosity of 0.8% (w/v) WL solution (25 °C).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121650&req=5

f3: Rheological property analysis of crude WL solution.(a) The viscosity of different concentrations of WL solution under different shear rates. (b) The effect of temperature on the viscosity of WL solution of different concentrations (0.2%, 0.6%, and 1.0% (w/v)). (c) The effect of pH (1–14) on the viscosity of 0.8% (w/v) WL solution (25 °C). (d) The effect of different concentrations of NaCl and CaCl2 (0-10%) on the viscosity of 0.8% (w/v) WL solution (25 °C).
Mentions: Rheological properties of WL solution were measured. As shown in Fig. 3a, an enhancement of viscosity with WL concentration at the same shear rate was observed. As welan gum and other sphingans2, all WL solutions showed a typical non-Newtonian pseudoplastic behavior or a strong shearing-thinning behavior. The viscosity of all solutions decreased when the shear rate increased and the degree of shear thinning was markedly increased as concentration of WL solution increased. This behavior may be due to the orientation or deformation of macromolecular network in the direction of flow caused by the shearing of EPS solution15. Furthermore, WL solutions exhibited good stability under diverse conditions including high temperature, wide range of pH and high concentration of salts (Fig. 3b–d). The viscosity of WL solutions at different concentrations (0.2%, 0.6% and 1.0%) showed little changes when the temperature increased from 30 °C to 100 °C, indicating that WL had good thermal stability. The viscosity of WL solution maintained at a high level in the range of pH 1–14. Compared with the highest viscosity, the lowest viscosity of WL solution decreased about 13% at pH 1. Generally, the repulsive interactions of anionic groups along the backbone of EPS chain lead to the high viscosity of EPS. However, when salts were added, cations with the opposite charge shielded the charge-charge repulsions, which resulted in a decrease in viscosity and even phase separation1516. Interestingly, our results showed that the salts had minor effect on its viscosity. The viscosity of the WL solution exhibited a little increase when NaCl (2 to 4%) or CaCl2 (2 to 8%) was added to the broth. When supplemented with 2% (w/v) CaCl2, the apparent viscosity of WL solution was increased by 9%. When the concentration of salts further increased, the viscosity decreased slightly and remained 90 and 86% when 10% (w/v) NaCl and CaCl2 was added, respectively. These results showed that the WL was of good salt resistance and this might be caused by the good hydrophilicity of main chain structure of EPS that made the space structure stable even when the charge of the EPS was shielded16.

View Article: PubMed Central - PubMed

ABSTRACT

Sphingans, a group of structurally closely related bacterial exopolysaccharides produced by members of the genus Sphingomonas, can be applied in a variety of industries such as food, cement, and personal care applications due to their high viscosity. A high sphingan-producing-bacterium, Sphingomonas sp. WG can secret large quantity of sphingan designated as WL. To enhance the production of WL, a three-stage control strategy was applied and the highest WL production can reach 33.3 g/L. The rheological analysis showed that the aqueous solution of WL had high viscosity, typical shearing-thinning behavior and great stability to high temperature, a wide range of pH (1 to 14), and high salinity. WL was composed principally of carbohydrate with 6.52% O-acyl groups. The carbohydrate portion of WL contained about 13% glucuronic acid and some neutral sugars including mannose, glucose and rhamnose in the molar ratio of 1:2.28:2.12. Partial acid hydrolysis of WL produced a new oligosaccharide WL-1. Structural resolution revealed that WL-1 consisted of α-L-Rha-(1→4)-β-L-Rha-(1→4)-β-D-Glc-(1→3)-α-D-Glc with β-D-Man substituent at the third glucose residue and carboxyl and O-acyl groups. These findings will broaden the applications of this novel sphingan in food, ink, oil and other industries.

No MeSH data available.