Applications of Alginate in the Fields of Research Medicine, Industry and Agriculture

Abstract

Alginate is a linear and anionic polysaccharide mainly extracted from brown algae and certain species of bacteria. This natural polymer is composed of guluronic acid and mannuronic acid units. Alginate belongs to a group of compounds that is generally considered a safe substance by the Food and Drug Administration, and due to its abundance, cheapness, and suitable biological properties, such as biocompatibility, non-toxicity, and the ability to gel easily in the fields of research, agriculture, industry, and medicine have been taken into consideration. The most important industrial applications of alginates as natural polymer materials are in line with their stabilizing properties, increasing viscosity, gelling, and ability to retain water. Due to the lack of alginate lyase enzyme (alginate-destroying enzyme) in the body of some animals, including humans, this polymer can be used in the preparation of wound dressings, drug carriers, tissue engineering scaffolds for skin, cartilage, bone, liver, and heart tissue. Alginate is also used in agriculture to coat seeds, fruits, and stem tips. The focus of the present chapter is on recent research advances in the applications of alginate from the industry and agriculture to the biomedical field.

1. Introduction

In the last decade, a lot of research has been experienced to discover naturally derived products with unique attributes and a high degree of application compatibility. The most all-purpose and influential derivatives are seaweed-and-bacterial polysaccharides, utilized in the food, pharmaceutical, and agricultural industries. These compounds have been approved in most countries of the world due to their rheological properties, suitable compatibility, and biodegradability. Seaweed-and-bacterial polysaccharides have lower calories due to their fiber-like state. They are usually used as a supplement to stabilize and adjust food consistency, such as cooked foods, jelly, mayonnaise, etc. Also, algal and bacterial polysaccharides do not have a damaging effect on the health of the human body due to their lack of toxicity and proper compatibility, therefore; they are used in the medical and pharmaceutical fields. Being biodegradable and compatible with the environment of Seaweed-and-bacterial polysaccharides has made them usable in different fields of agriculture [1, 2].

Alginate is a polysaccharide produced by marine algae, such as “Macrocystis pyrifera,” “Ascophyllum nodosum,” and “Sargassum sinicola” (Fucophyceae, formerly Phaeophyceae), mainly “Laminaria” (L. hyperborea, L. digitate, L. japonica), and other species like “Ascophyllum nodossum” and “Macropyriafery,” and bacteria, such as “Pseudomonas aeruginosa” and “Azotobacter sp.”, and because of its remarkable properties, it has been used in different sectors [3].

Alginate is the main polysaccharide in the cell wall and intercellular area of seaweed (in the case of bacteria and exopolysaccharide (EPS), which is secreted by bacteria into the surrounding environment and is made of α-L-Glucuronic (G) and β-1.4-D-Manoronic (M) acids. The ratio of these constituent units determines the physical characteristics of Alginates. For example, alginates with a high percentage of M blocks have a higher viscosity, and those with a high proportion of G blocks have a higher property to make a gel. Alginate is a mixture of calcium, magnesium, potassium, and sodium salts in the cell wall of seaweed and bacteria (Figure 1). The Alginate extraction process is a multi-step procedure based on converting the insoluble mixture of Alginic acid salts into a soluble salt (Alginate) [4].

Figure 1.

(a) Adding compounds such as sodium to the building block, and (b) the arrangement and composition of the monomer has an effect on the property and application of alginate.

Alginates are a group of compounds considered safe by the Food and Drug Administration (FDA). It was first used as an additive in the food industry; then, it was used in other parts, such as medicine, agriculture, and industry. Alginate can be transmuted into semi-solid or solid structures, such as sol or gel and used as stabilizers, emulsifiers, and carriers in the food and pharmaceutical industries. Specifications, such as cheapness, ease, safety, and compatibility have enabled the use of alginate for various industrial usages, exceptionally in the food industry. Coatings and films of Alginate are used in many packaged food products, such as drinks, milk powder, and instant teas. It is also used as a drug delivery system in the medical and pharmaceutical industry for products like vitamins and cold and dizziness drugs [5, 6].

The usage of alginate is growing in biotechnology products and has expanded in the medical and pharmaceutical fields. Biocompatibility, degradability, the property of becoming porous hydrogel and high absorption properties of Alginate can lead to its use in different medical applications, such as wound healing, drug delivery, and control of obesity and diabetes. Among other benefits and applications of Alginate, it is used in different parts of agriculture, such as encapsulation to trap plant growth stimulants small bacteria, slow release of microorganisms enclosed in soil, and some enriched protein substances. For these applications, Alginate systems were created, such as liposomes, hydrogels, nanoparticles, capsules, etc. These compounds have better degradability, compatibility, and non-toxic properties, and as a result, their effectiveness will be greater The purpose of continuing this chapter of the book, according to the characteristics of alginate such as biocompatibility, biodegradability, bioadhesion and also limitations, its applications in medical, industrial and agricultural research areas have been discussed [7, 8, 9].

2. Medical applications

Due to some side effects and toxicity, pharmaceutical and medical products made from chemicals have become an inseparable problem of the human health care system. The use of natural polymers in pharmaceuticals and medicine is comparable to synthetic polymers, and they are also widely used in the food and cosmetic industries. Currently, due to the negative impact and undesirable performance of synthetic polymers, they are looking for solutions to replace them [6, 9]. Biopolymers have been intensively studied primarily due to their biocompatibility, biodegradability, and ease of displacement and processing, and they have been used in drug delivery and medical applications. Known natural biopolymers used in pharmaceuticals and other fields are chitosan, carrageenan, ispaghula, acacia, agar, gelatin, guar gum, karaya gum (sterculia gum), and alginate. These natural polymers are used in the pharmaceutical industry as emulsifiers, adjuvants, and adhesives in packaging and in the development of cosmetic products [10, 11]. In the studies conducted on alginates as natural polymers, according to their unique properties and beneficial biological activities, they have been more and more considered attractive compounds in the biomedical and pharmaceutical fields. According to these studies, their use has led to biotechnological developments, such as being suitable as a matrix for 3D tissue cultures, antimicrobial and viral agents, and helping antibiotics, in the treatment of diabetes, obesity, or neurological diseases (Table 1). Sodium and calcium alginates are two natural polymers widely used in pharmaceutical and medical fields and have become common in most countries [12, 13].

Type of application of alginate	Applications
medicine	Improvement of skin inflammations and treatment of wounds, tumors and cancer, participation in the construction of various body tissues, diabetes, treatment of obesity and weight loss, drug transfer and delivery, cell and microbial cultures, antioxidant properties, transfer and storage of probiotics and prebiotics

Table 1.

Applications of alginate in the fields of medicine.

Other usages of alginate and its products in treating diverse diseases, including skin inflammations, tumors, osteoporosis, etc., have increased significantly. One of the applications of alginate in medicine is its use in wound dressing. The sodium alginate present in the dressing reacts with the wound fluid and retains the wound humid, and speeds up the healing process. Also, ions, such as calcium and other compounds can be used in dressings with alginate for faster wound amelioration. Immobilizing nanoparticles is a proper approach to their crucial role as agents against microbial infections without extreme aggregation. Due to its close relevance with the biomedical field, sodium alginate was specially selected to stabilize and bind the synthesized Nano Zink Oxide to cellulose fiber. Also, adding some compounds to alginate dressing, such as silver and some antimicrobial agents, excludes microbial putridity of wounds (Figure 2) [14, 15].

Figure 2.

Application of alginate in wound healing dressing.

Alginate-based hydrogels transfer various angiogenic molecules due to their special characteristics, such as biocompatibility, hydrophilic properties, cheapness, non-toxicity to the body, and accessible shaping properties. This case is used to treat patients with restricted or blocked blood flow [16]. Using alginate hydrogel capsules for tissue engineering applications has increased widely. These hydrogels can transfer inducing factors and needed substances for the repair of bone and cartilage tissues due to the property of adhesion to target tissue ligands, ease of transfer, and maintaining the stability of transfer substances. Alginate-based gels have been used for their ability to regenerate and engineer a variety of tissues, including skeletal muscles, the pancreas, nerves, and the liver. In researchers’ studies, chitosan nanoparticles were produced on liposomes for growth factor delivery [17, 18].

Based on successful experiments, it has been shown that alginate microparticles can easily be transferred to the cellular and subcellular structures in the epithelium of the stomach and intestines and subepithelial areas due to their adhesive properties, increased release time, and small particle sizes. Moreover, they are suitable for mucosal vaccination and drug transfer to the bloodstream. Oral administration of alginate does not stimulate many immune responses, unlike intravenous forms, and alginate has been reported to be non-toxic and biodegradable when given orally. This feature is used in the pharmaceutical industry to enhance drug resistance and hold the properties of molecules in the oral cavity and digestive system. These findings verify the ability of alginate nanoparticles to attach to the intestinal barrier and reach the bloodstream, which was the opposite of other combinations that remained mainly in the intestinal mucosa [19]. Alginate nanoparticles due to their ability to penetrate into the deep mucous layers of the stomach has been used to release amoxicillin in the treatment of Helicobacter pylori infection that settles in the deep mucous layers of the stomach. The transfer of anti-cancer, antimicrobial, and antibiotic drugs is achievable using these properties of alginate nanoparticles. Alginate gels are usually nanoporous, which leads to the fast diffusion of small molecules in the gel, so they are helpful for the delivery of a variety of intravenous drugs with low molecular weight [20, 21].

Probiotics are tiny, live, and active microscopic organisms, and eating them modifies the microbiome of our digestive tract for better health. We call them beneficial intestinal bacteria most of the time. It is good to know that sometimes when the balance of substances is disturbed in body tissues or fluids, or their function will be disturbed, the conditions may change so these beneficial microbes become pathogenic. But these situations rarely occur. Alginate has been employed to encapsulate several species of probiotic microbes. Alginate can be incorporated into the diet as a food favored by beneficial gut bacteria (i.e., prebiotics). This helps increase the number of good gut bacteria and promote digestive system health. Alginate capsules, including minerals, vitamins, antioxidants, enzymes, amino acids, etc., are operated as valuable substances for the health of the body in the pharmaceutical industry. Encapsulation of probiotics and prebiotics with alginate compounds enhances shelf life and increases stability and storage, furthermore; the alginate capsule permits the compounds to be mixed with other food products and used without the risk of losing their valuable properties. Alginate can inhibit peroxidation and radical chain reactions. So, it can be utilized as an antioxidant in all types of lipid foods [22, 23].

Diabetes or blood sugar disease is a complication that occurs when glucose (blood sugar) is too high in the body. Owing to the high preponderance of diabetes in these years, numerous people themselves or those around them are involved in this chronic disease. They are looking for a solution to recover as quickly as possible. Patients with diabetes require to obtain specific doses of insulin to regulate blood sugar and prevent dangerous consequences of glucose fluctuations. Insulin analogs are the first and most essential drugs used today to handle blood sugar in diabetic patients and are usually used by injection. This therapeutic method has been a standard procedure for regulating blood sugar fluctuations in people with diabetes for about a century. Maybe one of the most attractive ways to treat people with diabetes is using insulin capsules with alginate. This report is specifically happy for people who find it difficult to inject drugs. The causality for these failures is the ineptitude of insulin to cross the stomach acid barrier. When insulin enters the stomach as tablets or capsules, stomach acid rapidly breaks down all the insulin and destroys its hormonal properties. But because of the resistance and compatibility of alginate with stomach acid, insulin can be quickly delivered to the digestive system [24, 25].

Dietary fibers or oral fibers are structural polysaccharides that are very resistant to small intestinal enzymes and are entirely or partially fermented in the large intestine. For this reason, they are considered a strong regulator of the human digestive system. As a type of fiber, sodium alginate can absorb water molecules, and by this work, it becomes gelatinous and sticky, which makes food digestion slower. So, the food remains in the stomach longer, and you get hungry later. As a result, it is very beneficial for weight loss. In addition, alginate inhibits some enzymes in the digestive system. This action decreases the absorption of some compounds, including cholesterol and glucose, and results in participation in weight control and loss [26, 27]. The use of alginate gel compositions for cell culture in biomedical studies has increased. These gels can be easily used for cell cultures of mammalian cells. Likewise, the effect of sodium alginate microstructures on the growth of some bacteria like Listeria monocytogenes has been shown [28, 29].

3. Industrial applications

Alginate has various applications in industries, such as thickener, emulsifier, and stabilizer, increasing the viscosity of gels, water preservation, transfer of drugs and biomolecules, and edible films and coatings. A variety of alginates are accessible in the market according to the distribution of M and G blocks, molecular weight, purity, and composition. The Food Standards Agency has approved the “E numbers” to alginates for usage as food additives, and has allowed a variety of sodium, ammonium, potassium, and calcium salts as well as alginic acid esters and propylene glycol alginate. These compounds are used in the food industry depending on different degrees of concentration and viscosity. Sodium alginate is the most common alginate extracted from seaweed. In various countries and on diverse scales, sodium alginate is used in the biotechnology industry as a gelling agent and colloidal stabilizer. Alginate has low solubility in liquids and high viscosity, and it has attracted the attention of some industries (Table 2) [30].

Type of application of alginate	Applications
industry	Edible films and coatings, stabilization and gelling of food, food additives, storage and transfer of pharmaceuticals, helping to separate minerals, helping to remove heavy metals in industrial wastewater, battery industry, cellulose membranes, textile industry, helping In the construction of fuel cells

Table 2.

Applications of alginate in the fields of industry.

Today, environmental pollution caused by the disposal of waste packaging materials, specifically artificial synthetic polymers with a long-life cycle in nature, is regarded as one of the most important concerns at the global level. One of the ways to decrease the volume of packaging waste is to use bio-polymers in packaging. In recent decades, special and increasing attention has been paid to edible films and coatings that have the feature of biodegradability as appropriate and promising alternatives to synthetic polymers. The use of edible biopolymers for preparing films and coatings for food protection has a long history in the packaging industry and has attracted many researchers’ attention [31, 32, 33].

Among the significant benefits of edible films are antimicrobial and antioxidant properties. The cheapness of alginate, water-binding capacity, thickening, and emulsifying properties have made it essential in various industries for food and pharmaceutical packaging. Alginate films or nanocapsules gained from them also help to create natural products more attractive, such as additives, colors, and preservatives. Alginate edible coatings consist of a thin layer on the product’s surface, and their commercial applications face limitations. Of course, many experimental studies have been performed on food coating applications. In industrial dimensions, by spraying on irregular surfaces and vacuum tanks, it is possible to prevent microbial pollution and loss of food taste. The alginate-based edible film is constituted on the surface of food products by methods, such as dipping, coating, extrusion, casting, spraying, and brushing and can be used. The most common production method for food films is the casting method. For this purpose, a mixture of alginates with deionized water, softener, and other ingredients is used, and then it is stirred on a hot plate and poured on the surface. Silicone foils are used because of their ability to form thin layers and low adhesion, and Teflon sheets are used due to their high adhesion. Alginate is commonly used to extend the shelf life of food. Some compounds, such as essential oils, pureed fruits, natural extracts, and vegetables, are combined with alginate. Alginate films decrease spoilage and food waste and reduce foodborne illnesses. To expand the storage time and dissuade spoilage of food, such as mushrooms, tomatoes, turkey fillets, shrimp, meat, chicken thighs, cheese, etc., alginate compounds and coatings are used too. In the meat packaging industry, structures, such as calcium alginate are utilized as a replacement for natural coatings, such as the coating of fermented sausages. Techniques, such as immersion, spraying, or brushing are used for direct coatings on the surface of food, such as vegetables, meat, and fruits, but indirect coatings are for the surface of packaging materials [5, 34, 35, 36, 37].

Properties, such as gelling and thickening of alginate are used in food, such as animal food, sauce, ice cream topping, syrup, etc. The use of propylene glycol alginate in a very small portion creates a soft texture as well as the production of frozen crystals and furnishes a favorable feeling in the ice cream production process. Another use of alginate in the food industry is to stabilize fruit drinks. The use of alginate in all kinds of sauces is also common [30, 38].

Studies showed that iron-rich foods in combination with Alginate are very beneficial. Combining these foods with Alginate increases iron absorption. Modified starch is considered an essential ingredient in food industry applications. Studies show that some physicochemical properties of ordinary corn starch increase in the presence of Alginate [39, 40].

Alginate ratio and monomer composition is effective in some of its physiological and rheological properties. These properties also affect the applications of Alginate, such as thickening, stabilizing, and gelling. Because of its antioxidant properties, such as suitable molecular weight, monomer composition, and branching, Alginate prevents the generation of some harmful substances, such as oxidative compounds and free radicals, in foods and improves the quality of foods. Sodium Alginate extracted from some seaweeds is not sensitive to high temperatures due to the G/M monomer composition ratio, is stable in acidic conditions and has good antioxidant properties and has been used in the food industry [41, 42, 43].

For some probiotic food products, Alginate can be used to encapsulate the species and valuable substances in the digestive system. These tiny coatings protect helpful substances and bacteria during the digestive system and are very useful for delivery. In some chocolates and probiotic products, Alginate is used as a stabilizer, thickener, etc. [23, 44].

Alginate is used in polyelectrolyte membrane fuel cells, such as methanol and biological fuel cells, as well as alkaline-polymer fuel cells. Alginate compounds can also improve methanol permeability and proton conduction in some membranes [45, 46, 47]. The weak stability of antimony during the repeated insertion and unloading process of sodium ions leads to an unwanted application as an anode material in sodium-ion batteries. To solve this problem, Studies have shown that the electrochemical stability of the antimony nanoparticle coating can be enhanced with a carbon layer of sodium Alginate [48].

The limited water resources and the increasing expansion of industrial units, the growth in the production of industrial wastewater, and the pollution of water resources are among the social and economic problems. Wastewater from factories and production centers, such as textile, paper, pharmaceutical, and leather industries problematizes the process of wastewater purification due to the consumption of various chemicals and dyes. Alginate is also used in the purification of industrial wastewater pollution. Heavy metals and other microbial factors from the production and processing of industrial materials enter water and soil environments and cause environmental pollution. Numerous studies have been carried out to treat polluted wastewater using absorption technology and thus remove them. Combinations with Alginates, such as gels, nanoparticles, and microorganisms, can easily absorb and purify heavy metals, toxic compounds, and other industrial pollutants at a meager cost. Microorganisms that can produce Alginate among their compounds can absorb heavy metal ions. Likewise, by using Alginate, they can purify polluted water by changing and transforming polluting compounds. The composition of constructive monomers, as well as branches in the composition of Alginate, boost the removal property of ions and heavy metals. Alginate hydrogel absorption feature can also be used to absorb metals and industrial waste pollution [7, 49, 50]. Features of Alginate gel, like the thickening and stabilizing, is used in some papermaking and textile industries [8, 51].

The Stabilizing and stability properties of alginate can also be used in the production of biotechnology compounds. To perform some production and conversion processes, enzymes and microorganisms are used, which requires their stabilization and stability during the process. Enzymes can be immobilized on alginate as a stable substrate to carry out their process properly and prosper its efficiency. An example of this procedure is the conversion of agricultural trash, such as cellulose into hemicellulose, which stabilizes the cellulase enzyme on the alginate substrate and makes it more efficacious and stable. An example of this procedure is the conversion of agricultural trash, such as cellulose available in hemicellulose. Cellulase enzyme stabilized on the alginate substrate and become more efficacious and stable [52, 53]. Another case is to make capsules and porous enclosures from alginate for the accumulation of producing microorganisms. This feature prevents the distance of microorganisms and causes them to be closely related for better efficiency. Alginate is also employed as an enclosing matrix for drug delivery or some materials in the pharmaceutical and biotechnology industry (Figure 3) [3, 54].

Figure 3.

Enzyme immobilized by alginate is used in industry for some reactions.

Synthetic silver and gold nanoparticles (AuNPs) are widely used due to their colloidal stability and some unique chemical, physical, and biological properties. Gold nanoparticles (AuNPs) can be stabilized with sodium alginate (SA)/chitosan (GC) compounds in aqueous solutions at room temperature. Also, the distribution of different sizes of AuNP gold nanoparticles is obtained according to sodium alginate/chitosan polymer stabilizers [55, 56].

One of the ways to enhance the biodegradability of alginate is to oxidation the adjacent DL groups in the structure of uronic acid rings to aldehyde groups. Alginate oxide (alginate dialdehyde) is used to make biodegradable hydrogels. Also, due to the quick chemical reaction between amine and aldehyde groups, aldehyde alginate is used in the manufacture of chemical hydrogels with Schiff reaction and as biological ink [57, 58].

The water transmission pipeline system, including the drinking water network, sewage water network and circulating water system, is closely related to the safety of the water environment and human health. However, the corrosion of water transmission pipelines has become a great problem in practical applications, which affects both the lifetime of the pipeline and the quality of the water environment. Studies have shown that making a sustainable and environmentally friendly coating using sodium polycarbonate polyethylene/alginate coating is effective for corrosion protection of water transmission lines [59, 60]. There is also a notable concern for membrane fouling in membrane-based desalination technologies, especially in reverse osmosis (RO) membranes for implementing, such technologies. Some studies have found sedimentation using a silica/sodium alginate combination of reverse osmosis membranes to be helpful for seawater desalination [61, 62].

Flotation in the term means buoyancy and is one of the ways of concentration in the industry or increasing the grade of minerals (material enrichment). Today, flotation is undoubtedly the most important and comprehensive approach to mineral separation. Scheelite (CaWO4) is a common mineral and generally occurs in sediments with other minerals, such as calcite (CaCO3) and fluorite (CaF2). Currently, flotation is the most common technique used to isolate scheelite from calcite and fluorite. Research has shown that sodium alginate is effective in the flotation separation of scheelite from calcite and fluorite using sodium oleate as a collector. Sodium alginate has the potential to chelate calcium minerals and then hydrophilic their surface in solution [63, 64].

4. Agricultural applications

The increase in the world’s population has caused an increase in the demand for food. This issue has caused a change from traditional agriculture to advanced agriculture and the use of new methods in the production of crops and livestock, fertilizers or even poisons. Plants are the main and most important renewable resource in the world, which apart from providing human and animal food, also satisfy chemical and industrial needs. New methods in genetic engineering, biotechnology, and biological control of pests and pathogenic agents are used to increase the quantity and quality of products and reduce costs and time. Therefore, we see an increase in the use of these sciences in various agricultural sectors. The ways in which alginate can be used in agriculture include the production of plants resistant to insects, pests and herbicides, the production of plants with high nutritional values and better taste, the production of transgenic animals that have special characteristics, such as high milk production or low-fat meat, creation of animals that act as antibodies, vaccines and drug production factories (Table 3) [4, 65].

Type of application of alginate	Applications
agriculture	Covering and transferring plant growth stimulating bacteria, helping to increase the effect of plant and animal pesticides, transferring strengthening compounds to plants and animals, helping to fix and stabilize effective and useful compounds in plants and animals, helping to increase the germination of seeds Agriculture, increasing the resistance of plants in environmental stress

Table 3.

Applications of alginate in the fields of agriculture.

The use of alginate in encapsulating plant probiotic agents has become very common, particularly for controlling disease agents in agriculture. It is an alternative method to chemical methods for pest control and decreases the negative effects on the environment. Alginate is the best choice for transferring disease-control agents into the plant because of its preservative properties, stability, non-toxicity and minimal interference. Some herbicides can be easily placed in capsules created of alginate nanoparticles. This work accelerates the transfer of the herbicide and also prevents the negative effects on some useful plants. A clear example of this is the use of alginate carriers in the transfer of paraquat toxin (a contact and non-selective herbicide that destroys weeds by penetrating the leaves and green stems of plants) [66, 67].

Biodegradable alginate coatings are used as protection for some plant growth-stimulating bacteria or disease control. These coatings have been used to coat Bacillus bacteria as plant growth stimulants. Due to the environmental dangers of chemical pesticides, alternative solutions, such as biological control agents have been proposed to solve this problem. One of these promising solutions is the use of insecticidal bacteria, such as Bacillus thuringiensis Berliner. For this purpose, the bacteria are placed in a biodegradable alginate coating and sprayed on the plants. After the insects use these capsules, the insects die due to the production of toxic substances by the bacteria [68].

Rhizosphere bacteria with beneficial effects on plant growth and development are known as plant growth-promoting bacteria (PGPR). This group of bacteria is able to affect plant growth in direct or indirect ways. The direct effect includes the production or release of secondary metabolites, such as regulators or growth hormones and, such substances or facilitating the absorption of nutrients from the plant’s growth environment. But the indirect effect of PGPRs in stimulating plant growth occurs when the harmful effects of one or more pathogens are reduced or completely prevented. Also, these bacteria are used for bioremediation or to improve the efficiency of other bioremediation methods of soils contaminated with heavy metals. The use of alginate capsules has been attention due to characteristics, such as compatibility with the environment, low cost compared to physical and chemical methods, stabilization and stability during transportation, help to improve soil fertility, etc. These bacteria are inserted in the alginate capsule and during the transfer process, soil stresses, and factors, such as pH and soil moisture are maintained and perform their functions in the best way [69, 70]. Alginate capsules containing “Pantoea agglomerans” bacteria have been used as bio fertilizers compatible with the environment as well as controlling some pests [71].

One of the essential uses of alginate in agriculture is the use of encapsulation to transfer beneficial probiotic bacteria into the body of livestock. Transfer of probiotic bacteria into the alginate capsule perform to improve the conditions and survival of these important bacterial species. Food in the digestive system of livestock can be better digested and absorbed in the presence of probiotic bacteria. Prebiotics are food substances that are resistant to digestion in the upper part of the gastrointestinal tract and reach the lower part of the intestine intact. There, with their direct physiological effect, as well as by the specific stimulation of the growth and activity of the probiotic compounds of the gastrointestinal microflora, including Bifidobacterium, they affect the ecosystem of the gastrointestinal system. Alginate is used for the transfer and function of these materials. Alginate is oftentimes used as an ideal substrate for the delivery of probiotics as well as prebiotics due to its good biodegradability and high compatibility with the body, lack of toxicity (Figure 4) [23, 72].

Figure 4.

Using alginate microcapsules to transfer useful bacteria and micronutrients to the plant.

Also, other advantages of using alginate include the slow release of enclosed microorganisms and beneficial substances, low cost, and resistance to stomach acids and enzymes. Another advantage of using alginate is its combination with other useful compounds for the transmission and control of diseases in plants and animals in the agricultural sector. Studies have shown that alginate with chitosan creates a more stable and compatible combination. Also, the controlled release of compounds that are transported, such as various chemical or biological agents, is possible using the combination of alginate and chitosan. A clear example of this is the transfer of beneficial probiotic bacteria, such as Bifidobacterium and Lactobacillus into the livestock body. By combining alginate with gelatin, microcapsules can be produced, which are used to transport some useful bacteria, such as Pseudomonas fluorescens, and this increases the growth rate of potato plants. Also, this bacterium is used to control some diseases, such as dry rot in potatoes [23, 72].

Application of seed strengthening methods in order to eliminate or reduce environmental stress, increase germination percentage and seed yield is of high value. In some studies, it has been shown that the effect of different concentrations of alginate biopolymer as a seed coating is effective on the physiological stages of corn seedling growth under the stress of oil pollution [73].

5. Conclusion

Natural polymers obtained from seaweed and other microorganisms play a very important role in our life as an alternative to synthetic polymers. Natural polymers such as alginate have opened the way for use in various fields of medicine, industry and agriculture due to properties such as biocompatibility, biodegradability, bioadhesion, formation of gels, etc. Biological materials made of alginate are used in the medical field as drug delivery systems, tissue engineering, wound healing aid in dressings, cell cultures. On the other hand, alginate has been used in recent decades due to its potential applications in various industrial fields such as edible coatings in the food industry, helping to treat industrial wastewater, textile industries, papermaking and anti-corrosion coatings. In the field of agriculture, alginate is used to transfer weed poisons, transfer plant growth stimulants, control plant and animal diseases and pests, help increase the germination of plant seeds, etc. The wide variety of current applications of alginate as well as the increasing number of studies in different fields show the potential of this biopolymer for more applications in the future.