May 22, 2022

Influence of low-level gelling agents on the dissolution and in-vitro nutrient release study of coconut water-based hydrogel

The purpose of this study was to evaluate the controlled-release properties of nutrients from coconut water-based hydrogel. Hydrogels were prepared at varying proportions of gellan and xanthan gums such that the total weight of the gelling agents for all 11 formulations was 1% (w/w) in coconut water. The formulation of the hydrogel was selected using gravimetric analysis by evaluating the dissolution weight of the hydrogel in simulated gastric fluid and simulated intestinal fluid. Interestingly, hydrogel with 0.7% gellan gum and 0.3% xanthan gum showed the most tolerance towards simulated gastric and intestinal fluids over a 1-h period.
The in-vitro release study was performed in simulated gastric fluid and followed by simulated intestinal fluid for about 2 h. The trend of release profile showed that the hydrogel had the ability to sustain the nutrients release over a period of 1 h. After 75 min, the release trend was static indicated the nutrients was released from the hydrogel. In conclusion, a coconut water-based hydrogel formulated with 0.7% of gellan and 0.3% of xanthan gum has demonstrated its controlled-release property as evidenced by its effectiveness in the sustained release of nutrients over a period of 1 h.

Use of Alternative Gelling Agents Reveals the Role of Rhamnolipids in Pseudomonas aeruginosa Surface Motility

Pseudomonas aeruginosa is a motile bacterium able to exhibit a social surface behaviour known as swarming motility. Swarming requires the polar flagellum of P. aeruginosa as well as the secretion of wetting agents to ease the spread across the surface. However, our knowledge on swarming is limited to observed phenotypes on agar-solidified media. To study the surface behaviour and the impact of wetting agents of P. aeruginosa on other surfaces, we assessed surface motility capabilities of the prototypical strain PA14 on semi-solid media solidified with alternative gelling agents, gellan gum and carrageenan. We found that, on these alternative surfaces, the characteristic dendritic spreading pattern of P. aeruginosa is drastically altered.
One striking feature is the loss of dependence on rhamnolipids to spread effectively on plates solidified with these alternative gelling agents. Indeed, a rhlA-null mutant unable to produce its wetting agents still spreads effectively, albeit in a circular shape on both the gellan gum- and carrageenan-based media. Our data indicate that rhamnolipids do not have such a crucial role in achieving surface colonization of non-agar plates, suggesting a strong dependence on the physical properties of the tested surface. The use of alternative gelling agent provides new means to reveal unknown features of bacterial surface behaviour.

Effects of different gelling agents on the different stages of rice regeneration in two rice cultivars

Plant tissue culture technology offers a solution for meeting the increasing commercial demand on economically important plants such as rice, a widespread dietary staple. However, significant genotype-specific morphogenetic responses constitute a considerable on rice regeneration in plant biotechnology contexts. Aside from genotype dependency, the components of the nutrient media including gelling agents have an important impact on regeneration efficiency. The current study explores the effect of different gelling agents on various stages of rice regeneration in two Egyptian rice cultivars-Sakha104 and Giza178. Media solidified with varying concentrations of a variety of gelling agents (agar, bacto agar, gelrite and phytagel) were tested for their impact on the frequency of callus induction, shoot regeneration and rooting.
The results indicated gellan gum (gelrite and phytagel) was superior to agar products (agar and bacto agar) for callus induction. By contrast, no significant differences were found between different gelling agents for shoot regeneration. Gellan gum and media solidified with bacto agar were found to lead to significantly higher root regeneration than agar. The Sakha104 cultivar showed better responses than Giza 178 for callus induction and similar performance to the Giza 178 cultivar for root regeneration irrespective of the gelling agent. This work provides insights into the impact of different gelling agents on the morphogenetic response of two rice cultivars and can be used to help maximize the frequency of rice regeneration.

Development of Novel Low-Molecular-Mass Oil-gelling Agents: Synthesis and Physical Properties of 1,5-Anhydro-D-glucitol and 1,5-Anhydro-D-mannitol Protected with Saturated Linear Fatty Acids

We have developed a novel low-molecular-mass oil-gelling agent that is electrically neutral, has no nitrogen atoms and consists only of cyclic sugar alcohols and saturated linear fatty acids. The cyclic sugar alcohols were 1,5-anhydro-D-glucitol (1,5-AG) and 1,5-anhydro-D-mannitol (1,5-AM) derived from starch via 1,5-anhydro-D-fructose. Various saturated linear fatty acids with 10 to 18 and 22 carbon atoms were introduced into all the hydroxy groups of 1,5-AG. Various saturated linear fatty acids with 13 to 18 and 22 carbon atoms were introduced into all the hydroxy groups of 1,5-AM. Initially, the gelling ability increased as the carbon number increased, but the gelling ability decreased as the carbon number increased beyond 17 carbons. This trend was similar for both 1,5-AG and 1,5-AM.
A comparison of 1,5-AG and 1,5-AM derivatives revealed that 1,5-AG derivatives had greater gelling abilities for different kinds of oils at the same fatty acid length. Further, it was confirmed by SEM observations that a three-dimensional fibrous structure was formed, and this network structure formed the gel and held the oil. Here, we report the synthesis and characteristics of a novel low-molecular-weight gelling agent and its gelation mechanism.

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Bio-sourced polymers in cosmetic emulsions: a hidden potential of the alginates as thickeners and gelling agents

Objective: The present work aims to investigate the impact of the alginates on the texture properties of cosmetic emulsions. For this purpose, five systems were selected: a classical emulsion without polymer and four emulsions containing polymers, as texture modifiers, at the level of 1%. Two different grades of alginates were chosen: one rich in mannuronic acid and one rich in guluronic acid. The objective was also to evaluate the potential of in-situ gelation during formulation. The guluronic rich sample was gelled to evaluate the effect on the texture properties. Finally, alginates-based systems were compared to the xanthan gum as a bio-sourced polymer reference.
Methods: The sensory profile of the systems was established through a combination of prediction models and sensory analysis. The emulsion residual films obtained with natural polymers, Alginates and Xanthan Gum used as thickeners, as well as with the gelled version, were similar. However, the structural differences between polymers intervene during the characterisation of the sensory properties “before” and “during” application. A multi-scale physicochemical analysis was used to explain these differences.
Results: Due to a controlled formulation process, the use of the polymers did not affect the microstructure of the emulsion which remained similar to the control one. The main impact of the polymers was observed on the macroscopic level: both alginates showed their unique textural signature, different from the classical Xanthan Gum. Due to weak structural differences, mechanical and textural properties were very close between the mannuronic rich and guluronic rich samples, when not gelled, compared to other emulsions. However, the molar mass and the Mannuronic/Guluronic acids ratio were proved to be crucial for the stretching and consistency properties, showing that this structural difference may have an impact when products are handled in traction and compression.
Conclusion: Meanwhile, the viscoelastic properties and the dynamic viscosity were greatly increased for the emulsion containing the gelled version of the alginate when compared to the classical polymers. The emulsion was also more consistent as proved by the textural analysis, pointing at better stability and suspension potential of the gelled emulsion versus the classical one containing the usual natural thickening agents.

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