Adaptation of the alginate production process for the brown alga Sargassum horridum (Fucales: Sargassaceae)

Abstract

The genus Sargassum is a brown alga which is abundant in México, in the Gulf of California and the Caribbean Sea. The large biomass could be used to production of alginate, a polysaccharide with properties which allow it to form a thick solution or gels for different industries, such as for pharmaceutical and food products. The alginate production process may have some modifications, depending on the type of alga that is used as raw material, reducing water consumption and increasing the alginate yield and quality. In this research, the amount of water and reagents was optimized, reducing the volumes in the production process, based on the volumes used to process the giant kelp Macrocystis pyrifera. Hydration was reduced from 1 : 10 to 1 : 4 (part of alga : volume of chemical), acid pre-extraction from 1 : 10 to 1 : 5, extraction from 1 : 16 to 1 : 10, and dilution from 1 : 55 to 1 : 15; bleaching was improved from very dark brown to pale brown. The main reason that reduction is possible is that Sargassum has a more rigid cell wall than Macrocystis, absorbing less water and producing less viscosity. Although the alginate viscosity is relatively low, some applications require low viscosity solutions. However, the gel strength reached up to 1906 g cm−2, which may compete with other alginates to produce gelling products. To avoid the use of hydrochloric acid and decrease the contamination of wastewater in the process, the acid pre-extraction stage was changed for a neutral pre-cooking stage, resulting in an increase of the alginate yield from 8.3 % to 13.5 %; the viscosity was normally kept low, but the gel strength increased up to 2400 g cm−2.