A hydrogel consists of a hydrophilic polymeric network composed of polymers and their solvents. It can absorb significant amounts of solvent and keep it within matrices [1]. Polymers undergo conformational changes in response to variations in solvent conditions like ionic strength and temperature, as described by Tanaka [2]. Hydrogels have extensive applications in the food industry due to their safety features and efficient three-dimensional cross-linked structures, such as fat substitutes, package delivery systems, and edible films ^[3][4][5][3,4,5]. Carbohydrates and proteins are frequently used as monomers for developing hydrogels. Combining two or more monomers can result in a hydrogel system with enhanced physicochemical properties compared to a single polymer gel [6]. Polysaccharide-based hydrogels have been the focus of significant interest and investigation because of their favorable bioactivity, biocompatibility, and biodegradability. Research has demonstrated that hydrogels composed of polysaccharide-polysaccharide complexes, which exhibit good compatibility, can form a tightly woven interpenetrating network. This can alter the gelation time, improve water retention, and boost the gel’s strength [7]. Enhanced features have been documented for konjac glucomannan-gellan gum, erythritol-curdlan, konjac glucomannan-curdlan, and gellan-xyloglucan complexes ^{[8][9][10][11]}[8,9,10,11]. Hence, complexes of polysaccharides could enhance gel properties by leveraging synergistic interactions, rendering them a focal point in the development of gel products.

In recent years, microbial polysaccharides have garnered a great deal of interest due to the amazing functions and vast industrial applications they possess and the fact that they can be produced in a sustainable manner across commercial scales. Methods from the fields of system biology and biochemical engineering may be used to further reduce the costs associated with their manufacture [12]. The ingredients that comprise microbial polysaccharides include both carbohydrate and non-carbohydrate components. They are dependent on the genus of the microorganism that produces the microbial polysaccharide to determine the non-carbohydrate ingredient, which may vary from acetate to pyruvate and even succinate in certain cases [13]. When it comes to microbial polysaccharides, sphingans are distinguished by their tetrasaccharide repeating backbone, which is accompanied by a variety of substitutions on the side chain. Depending on factors such as the linkage pattern, the length of the polysaccharide, the intra-molecular connection, and the polymeric cross-linking with molecules in the surrounding area, the individual sphingan is a rheologically distinct entity [14]. There are considerable differences in the chemistry and functional features of the various sphingans, despite the fact that all of the sphingans are generated by different strains of Sphingomonas species [12].

Gellan gum (GG) is an exopolysaccharide secreted outside of the bacterial cell, produced by species from the genus Sphingomonas, and it is soluble in water. In 1978, bacteria that produce gellan were found and isolated by the former Kelco division of Merck & Inc. Company, Rahway, NJ, USA. The bacteria were discovered in lily tissue from a natural pond in Pennsylvania. Initially recognized as a substitute gelling agent for agar in solid culture media to support the growth of different microorganisms due to its ability to withstand high temperatures up to 120 °C, it was introduced as a commercial product under the trademark Gelrite GG. It found applications in the pharmaceutical, cosmetic, and food industries [15]. The composition of GG includes three fundamental units: α-L-rhamnose, β-D-glucose, and β-D-glucuronate, in a ratio of 1:2:1. GG possesses transparency, high tensile strength, and a pleasant taste. It exhibits high stability to temperatures and resistance to acidic enzymes. With a molecular weight of up to 500 KDa, it forms a viscous solution when dissolved in aqueous solutions but remains insoluble in ethanol. This compound maintains stability across a broad pH range of 2–10. GG finds extensive applications in the food industry as a thickening agent, binding agent, stabilizer, emulsifier, and gelling agent [16].

GG is derived from various species of Sphingomonas bacteria, like S. pseudosanguinis and S. yabuuchiae, utilizing fat residues like glycerol as a nutritional medium for these bacteria [15]. Huang and colleagues [16] demonstrated the potential of utilizing corn waste to produce GG from S. paucimobilis bacteria. The production yield achieved a level of 14 g/L in the production medium. Utilizing molasses and cheese whey as the media, fermentation was carried out to produce GG from S. azotifigens bacteria, resulting in a gum with a molecular weight of 890 KDa [17]. GG is utilized in various food industries and is frequently utilized in the production of juices, sweets, beverage powders, jelly, jams, marmalades, vegetable butter (margarine), and yogurt ^[18][19][20][18,19,20]. In 1990, the gum underwent evaluation by the Scientific Committee for Food of the European Union. It received unconditional approval for use in food due to evidence of cytotoxicity. The gum was assigned the symbol E418 and can be used at concentrations of 0.1–1.0% [21].

GG is a food additive that has been utilized for an extended period because of its functional properties. Currently, there is a growing interest in this field because of the advancements in new materials and the enhancement of food systems to improve their rheological properties ^[22][73]. GG was utilized in colloidal aqueous solutions due to its capacity to produce gelatinous substances at low concentrations and establish a network in contrast to other polycarbonates employed in foods (Table 1). Adjusting the gum, like eliminating the acetyl group, led to the production of gelatinous materials with unique physical characteristics, enabling its utilization in various food product models ^[23][74].

In various industries, polygons found in foods are combined with other elements to eliminate certain undesirable characteristics. For instance, GG has low mechanical strength, so when combined with pullulan, it resulted in a product with favorable sensory properties and distinctive rheological characteristics ^[30][76]. In a study by Kanyuck et al. ^[31][77], it was demonstrated that combining GG with maltodextrin resulted in the formation of a robust, intertwined network. This blend was utilized in low-fat items as a substitute for fat while also providing a sensation of satiety. In a study by Sapper et al. ^[32][78], it was found that incorporating thyme oil with GG in creating a film for fruit preservation resulted in the development of an edible composite film. This film extended the preservation period by reducing evaporation and inhibiting the growth of microorganisms.

Recently, it was discovered that GG can act as a stabilizing agent and also preserve volatile oils in coated fruits. It can improve the percentage of ascorbic acid and antioxidant activity, enhance preservation processes, and extend the storage life of highly perishable fruits, ultimately prolonging their stay in the market ^[33][79]. GG is a cost-effective multivitamin that is ideal for use in the production of sweets and jams due to its high crystallinity and its capacity to regulate the product’s moisture. Not only is the gel colorless and has a high melting point but sweets can also be stored at room temperature. Research has shown that the optimal concentration for sweets is 0.3%. Foods with GG can retain their shape and appearance for an extended period due to its water-absorbing properties ^[34][80]. In a study, Kong et al. ^[35][81] discovered that incorporating 0.1% of low-acyl GG into soybean milk yogurt resulted in the development of a stable gel network with increased viscosity, enhanced water retention capacity, and a smoother texture in comparison to the control group. Thus, GG is regarded as a stabilizer. It is appropriate for this product while also enhancing its sensory characteristics. In a study by Mongkontanawat and Khunphutthiraphi ^[36][82], it was found that incorporating 10% GG into sprouted black rice for vegetable yogurt resulted in a soft texture and good sensory appeal. This addition did not impact the moisture, protein, or fat content but also increased the levels of antioxidants and lactic acid bacteria. The study demonstrated significant toxicity toward breast cancer cell lines when compared to yogurt produced from sprouted rice without added GG ^[36][82]. This offers the opportunity to create nourishing and wholesome meals for adults and elderly people.

Edible films developed from GG have become increasingly popular in food-related uses because of their versatility and advantageous characteristics ^[12][37][12,52]. These films are thin layers of material that can be ingested with food, offering different functionalities. An overview of the production and applications of edible films using GG in the food industry is provided in Table 2 and Table 3. Utilizing GG in edible films presents a sustainable and functional method for food-related uses, delivering advantages like decreased waste, enhanced preservation, and improved sensory experiences for consumers ^[12][15][12,15].

^67][68][110,111]. There have been several cutting-edge advancements in the use of GG to develop responsive systems in the field of biomedical applications (Table 5). The latest developments in the use of GG in various biomedical fields demonstrate its ability to advance drug delivery ^{[64][67][68][69]}[107,110,111,112], tissue engineering ^[70][71][113,114], wound healing ^[72][73][115,116], and diagnostics ^[68][74][111,117]. The responsive nature of GG enables the development of specific systems that react to particular physiological signals, enhancing their efficiency and flexibility in different biomedical scenarios.

The plant’s characteristics, its resistance to temperature, and its capacity to expand and be trimmed all play a role in the various functions of GG. Consequently, it has been incorporated into a diverse range of medicinal formulations (Table 4). Aside from being utilized in gene transfers for certain health purposes, it has also been employed to develop ointments to treat dental and ocular conditions ^[53][97]. To explore the gelatinous properties, Bajaj et al. ^[54][43] mixed GG with the antibiotic ciprofloxacin. Ciprofloxacin is an antibiotic that effectively targets both gram-negative and gram-positive aerobic bacteria. According to these results, the mixing process led to a longer duration of medication release in the body, enhancing the medicine’s effectiveness against specific bacteria. Dev et al. [12] showed that a capsule produced with GG consisted of an ionic solution in the presence of water containing calcium ions. This solution formed a three-dimensional network of GG gel by creating intersections in the polymer chain caused by the presence of these ions. This led to the creation of a capsule that could be used to deliver the drug to humans.

The fact that GG exhibits poor mechanical strength, brittleness, and a low degree of crystallinity when it is combined with pharmaceutical and medicinal ingredients is one of the challenges that is linked with the development of medications utilizing GG. By dividing the GG chains into smaller parts with the help of an oxidizing agent called sodium periodate, a study was carried out with the purpose of finding a solution to this issue. This led to the appearance of hardness in the gel, which in turn led to an increase in the amount of time that the drug was available within the body. Additionally, the use of GG as a binder resulted in an increase in the number of viable bacteria cells ^[61][104]. Silva et al. ^[62][105] observed that GG is an effective carrier biomaterial that also improves cell adhesion. Furthermore, they stated that the polymer was modified by including a peptide that was obtained from fibronectin, which is a glycoprotein that is formed outside of the cell cells. Additionally, in comparison to unmixed GG, this combination resulted in the multiplication of neural stem cells, and the results of this research demonstrated that it was successful in treating damage connected to the spinal cord. GG has been applied in the field of tissue engineering as well. As per research conducted by Vasile et al. ^[63][106], GG hydrogels were utilized as scaffolds for the regeneration of different tissues like bone and cartilage. The hydrogel’s capacity to replicate the extracellular matrix and offer mechanical support to the cells positions it as a prime choice for tissue engineering purposes. Aside from its function in drug delivery and tissue engineering, GG has also been utilized in wound healing. Alharbi et al. ^[64][107] explored the application of GG-based hydrogels in treating chronic wounds. The researchers discovered that the hydrogel supported wound healing by creating a moist environment that helped cells migrate and boosted angiogenesis. Moreover, GG has been investigated for its promise in the realm of regenerative medicine. An investigation conducted by Ghandforoushan et al. ^[65][108] showcased the application of GG hydrogels in transporting stem cells. The hydrogel created an optimal microenvironment for the stem cells, improving their ability to survive and differentiate, ultimately boosting their therapeutic capabilities. Furthermore, GG has been used in creating controlled-release dosage forms. A study conducted by Carrêlo et al. ^[66][109] reported the development of GG-based microparticles for the sustained release of drugs. The microparticles demonstrated a controlled release profile that enabled extended drug release and enhanced therapeutic effectiveness.

GG, a highly versatile hydrocolloid, has been receiving increased interest in the biomedical sector because of its exceptional properties and potential uses in developing responsive systems ^[

Microbial polysaccharides are utilized in cosmetics for their unique physical and chemical properties as well as their biological activities. GG can be utilized in cosmetics due to its ability to enhance viscosity at low concentrations. Polysaccharides like hyaluronic acid, bacterial cellulose, levan, and GG play a crucial role as active ingredients. GG aims to enhance water retention and alter rheological characteristics ^[87][129]. GG is a key component in numerous cosmetics, serving to enhance viscosity and act as a stabilizer for certain emulsions applied to and left on the skin. It has been utilized in concentrations ranging from 0.3% to 0.5%. It can also be utilized in the production of toothpaste at concentrations ranging from 0.025% to 0.25%. These minimal amounts provide durability to the product even at temperatures as high as 60 °C, along with its thin texture and uniformity ^[88][57]. In a study by Iurciuc et al. ^[89][130], it was discovered that GG has positive effects on cosmetics, particularly in hair moisturizing and sun protection products. When GG is applied to the skin, it provides a pleasant sensation to the user. It was combined with xanthan gum to enhance the effectiveness of hair care products, being utilized at a concentration of 0.2%.

GG, derived from bacteria, has been utilized as a substitute for agar in fields for cultivating various microorganisms. It has been introduced to the market as Gelrite because certain microorganisms have specific enzymes that can break down agarose into the compound 3,6-anhydro. L-galactose and D-galactose are indicated in reference ^[90][131]. GG was developed under a different brand name, phyta gel, and is commonly utilized as a replacement for agar in agricultural media. It also helps in solidifying the agricultural media for growing tissue plants ^[91][132]. GG was utilized for the separation of DNA components post-extraction from various sources through electrophoresis. It acts as a gel with pores, enabling the passage of these components ^[92][133].