Preface

Alginate is a natural biopolymer synthesized mainly by brown seaweed but also by microorganisms, also called bacterial alginate. It is a polysaccharide that has similar characteristics to pectin present in plants; however, it is present in the cell walls of brown algae, of the Phaeophyceae class, in a similar format to cellulose microfibrils, arranged in a crystalline arrangement, in addition to being derived from the intercellular matrix of these seaweed.

The most used alginate in industry is sodium alginate, which is extracted through steps involving physicochemical procedures, starting with a treatment of the dry material using formaldehyde, followed by an acid process, after collecting the algae in its marine habitat. After these steps, an alkaline extraction is performed, followed by bleaching, precipitation, and drying.

The applications of alginate currently depend on its characteristics such as low toxicity, anti-inflammation, high absorption, and thickener in food mixtures, in addition to having the ability to accelerate healing in pharmaceutical processes.

Therefore, the polysaccharide is exploited in industries involving food, beverages, fabrics, printing, and pharmaceuticals. An example of its use is in materials from the pharmaceutical and cosmetics industries, which guarantee improved stability and damage control due to external conditions such as temperature and UV light, or even protection in gastric environments if they are for oral use. In the food industry, alginate applications are based on three properties: thickening, gelling, and film forming.

Alginate can also be seen as an additive in packaging to improve the quality of and prevent damage to the coated product, promoting good conservation due to the added attributes, such as antimicrobial and antioxidant action. Another area where alginate is highly used is in agriculture where it functions in improving productivity, treating water, and improving the quality of the crop through uses in seed coatings, fruits, and vegetables that help with growth, in addition to being used in formulations that control the use of agrochemicals.

Due to the versatility of uses of alginate, several new technologies have been developed to create sustainable solutions with lower environmental impact, including self-healing asphalt, bio-ink for 3D printers, flame-retardant materials, and alginatebased bio-composite materials for wastewater treatment. For example, microalgae and cyanobacteria can be immobilized in sodium or calcium alginate beads and used several times without significant loss of cell activity, ensuring the stability of the processes in which they are applied. This technological route has received increasing interest from researchers and scientists in microalgae-based processes for industrial effluent treatment. Microalgae cell immobilization in polymeric alginate matrices can be performed by several methods and can be exploited for the bioremediation of different types of wastewater and contaminants.

In this sense, the chapters in this book provide an in-depth understanding of the applications and future perspectives of alginate, contributing to the consolidation of information about its characterization, properties, synthesis, current uses, and trends.

**Ihana Aguiar Severo, André Bellin Mariano and José Viriato Coelho Vargas** Technology Sector, Postgraduate Program in Materials Science and Engineering (PIPE), and Sustainable Energy Research and Development Center (NPDEAS), Federal University of Paraná (UFPR), Curitiba, PR, Brazil

Section 1 Fundamentals
