**10. Conclusions**

Algae are considered a major source of alginate. Since their alginate content and properties are varying, first, the amount to be used should be decided. According to this decision, algae species and the time for growing and harvesting of them must be taken into attention. After that, depending on the area of use, the extraction method should be determined in order to obtain the highest yield of alginate from algal biomass. Now, it is ready to be utilized in different types of sectors. For example, immobilized microalgae networks are open to novel applications. Environmental monitoring and algae-based biosensors comprise one of the promising topics for future developments. Rather than classical bead or thin-film fabrication methods, novel biofabrication techniques can be adapted for algae immobilization, which can help to design customized geometries. Also, as a result of the ability to combine with two different cations to form gel, alginate-contained products show significant elasticity. Unfortunately, algal alginate may contain some impurities like heavy metals, polyphenols, proteins, and endotoxins. In the food industry, low levels of them can be acceptable. But before they are used in cosmetic and pharmaceutic industries, they have to be removed using some purification methods. Alginate NPs have properties such as being biocompatible, nontoxic, and biodegradable. They are safe and preparation of the alginate NPs is easy and so this makes them a potential carrier for drug delivery systems. They can be applied to various drug-delivery systems. Alginate NPs are FDA approved as a food additive and has great mucoadhesive properties, which can make them a potential candidate for drug delivery through the oral route. In agriculture, chitosan/alginate NPs are used mostly for targeted and systemic delivery of agrochemicals, and it has a great potential for prolonged availability and low load of the molecules. Agricultural technology and increase of the fertilizers and pesticides unfortunately made a negative contribution to environment. However, NPs, especially "green NPs," made agriculture more sustainable by using lower doses and slower release of the molecules. Increased awareness of the environmental problems comes with an unavoidable sustainability in all fields, and green NPs are good for environment because their application in agriculture is safe, and also their productions are considered sustainable. However, there are certain limitations to the industrial application of alginate. The most important of these limitations is the exponentially increasing cost with growing scale. For example, coagulants currently used for wastewater treatment are relatively cheaper than algal alginate. However, traditional coagulation processes may require extra costly processes such as pH adjustment or alkalinity addition. Today, in studies about algal alginate, it is possible to increase the efficiency of the system and reduce the cost of coagulation with alginate by using their better and more suitable quality versions.
