Optimization of welan gum extraction and purification using lysozyme and alkaline protease

Welan gum, a natural polysaccharide produced by Sphingomonas sp. ATCC 31555, has attracted considerable attention in the scientific community due to its desirable properties. However, challenges, such as high viscosity, residual bacterial cells, carotenoids, and protein complexation, hinder the widespread application of welan gum. In this study, we established a method for the extraction and purification of welan gum using a synergistic approach with lysozyme and alkaline protease. Lysozyme hydrolysis conditions were optimized by applying response surface methodology, and the best results for bacterial cell removal were achieved at 11 000 U/g, 44 °C, and pH 9 after 3 h of treatment. Subsequently, we evaluated protein hydrolysis through computer simulation and identified alkaline protease as the most suitable enzyme. Through experimental investigations, we found that the optimal conditions for alkaline protease hydrolysis were 7500 U/g, 50 °C, pH 10, and 600 rpm. These conditions resulted in a sugar recovery rate of 76.1%, carotenoid removal rate of 89.5%, bacterial removal rate of 95.2%, and protein removal rate of 87.3% after 3 h of hydrolysis. The purified welan gum exhibited high transparency and purity. Structural characterization and antioxidant activity evaluation revealed that enzymatically purified welan gum has potential application prospects. Our study provides valuable insights into the optimal method for the enzymatic extraction and purification of welan gum. Such a method is conducive to the development of the multiple potential applications of welan gum. KEY POINTS: • A novel process for the synergistic purification of welan gum using lysozyme and alkaline protease was established. • In silico virtual digestion was employed to select the purification enzyme. • Welan gum with high transparency and purity was obtained.

Glycerol-driven adaptive evolution for the production of low-molecular-weight Welan gum: Characterization and activity evaluation

Through adaptive laboratory evolution (ALE) of Sphingomonas sp. ATCC 31555, fermentation for production of low-molecular-weight welan gum (LMW-WG) was performed using glycerol as sole carbon source. During ALE, GPC-MALS analysis revealed a gradual decrease in WG molecular weight with the increase of adaptation cycles, accompanied by changes in solution conformation. LMW-WG was purified and structurally analyzed using GPC-MALS, monosaccharide composition analysis, infrared spectroscopy, NMR analysis, atomic force microscopy, and scanning electron microscopy. Subsequently, LMW-WG obtains hydration, transparency, antioxidant activity, and rheological properties. Finally, an in vitro simulation colon reactor was used to evaluate potential prebiotic properties of LMW-WG as dietary fiber. Compared with WG produced using sucrose as substrate, LMW-WG exhibited a fourfold reduction in molecular weight while maintaining moderate viscosity. Structurally, L-Rha nearly completely replaced L-Man. Furthermore, LMW-WG demonstrated excellent hydration, antioxidant activity, and high transparency. It also exhibited resistance to saliva and gastrointestinal digestion, showcasing a favorable colonization effect on Bifidobacterium, making it a promising symbiotic agent.

Natural gums and their derivatives based hydrogels: in biomedical, environment, agriculture, and food industry

The hydrogels based on natural gums and chemically derivatized natural gums have great interest in pharmaceutical, food, cosmetics, and environmental remediation, due to their: economic viability, sustainability, nontoxicity, biodegradability, and biocompatibility. Since these natural gems are from plants, microorganisms, and seaweeds, they offer a great opportunity to chemically derivatize and modify into novel, innovative biomaterials as scaffolds for tissue engineering and drug delivery. Derivatization improves swelling properties, thereby developing interest in agriculture and separating technologies. This review highlights the work done over the past three and a half decades and the possibility of developing novel materials and technologies in a cost-effective and sustainable manner. This review has compiled various natural gums, their source, chemical composition, and chemically derivatized gums, various methods to synthesize hydrogel, and their applications in biomedical, food and agriculture, textile, cosmetics, water purification, remediation, and separation fields.

Advances in gum-based hydrogels and their environmental applications

Gum-based hydrogels (GBHs) have been widely employed in diverse water purification processes due to their environmental properties, and high absorption capacity. More desired properties of GBHs such as biodegradability, biocompatibility, material cost, simplicity of manufacture, and wide range of uses have converted them into promising materials in water treatment processes. In this review, we explored the application of GBHs to remove pollutants from contaminated waters. Water resources are constantly being contaminated by a variety of harmful effluents such as heavy metals, dyes, and other dangerous substances. A practical way to remove chemical waste from water as a vital component is surface adsorption. Currently, hydrogels, three-dimensional polymeric networks, are quite popular for adsorption. They have more extensive uses in several industries, including biomedicine, water purification, agriculture, sanitary products, and biosensors. This review will help the researcher to understand the research gaps and drawbacks in this field, which will lead to further developments in the future.

Green and Superior Adsorbents Derived from Natural Plant Gums for Removal of Contaminants: A Review

The ubiquitous presence of contaminants in water poses a major threat to the safety of ecosystems and human health, and so more materials or technologies are urgently needed to eliminate pollutants. Polymer materials have shown significant advantages over most other adsorption materials in the decontamination of wastewater by virtue of their relatively high adsorption capacity and fast adsorption rate. In recent years, "green development" has become the focus of global attention, and the environmental friendliness of materials themselves has been concerned. Therefore, natural polymers-derived materials are favored in the purification of wastewater due to their unique advantages of being renewable, low cost and environmentally friendly. Among them, natural plant gums show great potential in the synthesis of environmentally friendly polymer adsorption materials due to their rich sources, diverse structures and properties, as well as their renewable, non-toxic and biocompatible advantages. Natural plant gums can be easily modified by facile derivatization or a graft polymerization reaction to enhance the inherent properties or introduce new functions, thus obtaining new adsorption materials for the efficient purification of wastewater. This paper summarized the research progress on the fabrication of various gums-based adsorbents and their application in the decontamination of different types of pollutants. The general synthesis mechanism of gums-based adsorbents, and the adsorption mechanism of the adsorbent for different types of pollutants were also discussed. This paper was aimed at providing a reference for the design and development of more cost-effective and environmentally friendly water purification materials.

Progress in modifications of 3D graphene-based adsorbents for environmental applications

3D graphene-based materials are promising adsorbents for environmental applications. Furthermore, increasing attention has been paid to the improvement of 3D graphene adsorbents for removing pollutants. In this article, the progress in the modification of 3D graphene materials and their performance for removing pollutants were reviewed. The modification strategies, which were classified as (1) the activation with CO₂ (steam and other oxidants) and (2) the surface functionalization with polymers (metals, and metal oxides), were evaluated. The performances of modified 3D graphene materials were assessed for the removal of waste gases (such as CO₂), refractory organics, and heavy metals. The challenges and future research directions were discussed for the environmental applications of 3D graphene materials.

Ion-imprinted sponge produced by ice template-assisted freeze drying of salecan and graphene oxide nanosheets for highly selective adsorption of mercury (II) ion

As a kind of potential heavy metal absorbent, polysaccharide-based materials are limited by the complicated preparation method and bad selectivity toward targeted ion. Here, a fantastic sponge was produced by combining salecan and graphene oxide (GO) nanosheets via ice template-assisted freeze drying and ion-imprinting technologies. The intense intermolecular interactions between salecan and GO gave the sponge high stability. The swelling, morphology, and mechanical stiffness of the material showed highly dependent on the salecan content. Additionally, the influence of salecan content, pH, initial ion concentration, and contact time on Hg²⁺ adsorption was extensively investigated. Adsorption kinetics and equilibrium isotherms perfectly fitted in the pseudo-second-order and Freundlich models, reflecting the multilayer chemical-adsorption mediated mechanism. Most strikingly, the ion-imprinted sponge exhibited strong selectivity toward Hg²⁺ and outstanding stability with recyclability over usage of five times. These investigations provide the guidance for the construction of promising polysaccharide-based adsorbents for the remediation of Hg²⁺-polluted water.

The effect of pH on the properties of 3D welan gum–graphene oxide composite hydrogels and their excellent adsorption capacity

The effect of pH on welan gum hydrogel for dye adsorption and swelling ratio.