**1. Introduction**

Alginate is an anionic polymer that occurs naturally in brown algae (Phaeophyceae), normally present on the cell walls of these organisms.

Alginate is a structural element designated to be the seaweed's main skeletal compound likewise the cellulose function in terrestrial plants, with the gel located in the cell walls and intercellular matrix conferring the mechanical strength and flexibility necessary to withstand the force of the water in which the seaweed grows [1]. Moreover, this function is reflected in the compositional difference of alginates in different seaweeds.

Alginate varies in composition of the algae from 20 to 60% dry matter, but on average brown algae species has 40% alginate. Alginate in brown algae occurs as gels containing sodium, calcium, strontium, magnesium, and barium ions [2].

Alginate is not a compound exclusively of brown algae because there are bacteria that can also produce alginate, but currently all commercial alginate is extracted from algae biomass [3].

Industrial applications of alginate are linked to the gelation, viscosity, and stabilizer properties that alginate attributes to the solutions and products in which it is present. Normally the alginate is a matrix of alginic acid bound cations, such as calcium, sodium, or magnesium. These ions give greater stability to the alginic acid molecule, where the divalent cations give alginate a very rigid conformation and a stable structure unlike the alginate with monovalent cations.

The biotechnological applications of alginate are based on specific effects of the alginate molecule and its variations depending on the covalent bonds with cations, such as calcium, sodium, or magnesium, and this allows for a great number of applications in several variations of the structure and conformation of the alginate molecule.

Alginates are in vogue for specialized knowledge as a pharmaceutical or biomedical ingredient or as compound for advanced biotechnology, and these investigations are turning to a more detailed study of the properties and structure of alginate, leading to points of scientific innovation that, associated with empirical knowledge, will benefit the traditional techniques of alginate exploitation.
