# Optimisation of Alginate Extraction and Characterisation of Polysaccharides from Brown Seaweed from the Portuguese Coast

## TL;DR

This study explores sustainable alginate extraction from brown seaweed found along the Portuguese coast, achieving high yields with an eco-friendly method.

## Contribution

The paper introduces an optimized, environmentally friendly two-step extraction method for sodium alginate from local brown seaweed species.

## Key findings

- The optimized extraction process achieved yields above 20% of high-purity sodium alginate.
- The extracted alginate showed comparable quality to commercial sodium alginate.
- The method reduces environmental impact by using a simplified, solvent-reduced protocol.

## Abstract

Alginate is a widely used and versatile biopolymer with an ever-expanding range of applications in the pharmaceutical and biomedical industries. This highlights the importance of developing sustainable and renewable production sources. Conventional extraction methods, although effective, are often energy-intensive and rely on harsh chemicals. In this context, brown algae are a promising alternative due to their abundance and renewability. This study investigated the potential of Saccorhiza polyschides and Sargassum muticum as sources of sodium alginate (SA), thus optimising an extraction process that combines acid treatment with an alkaline step. The extracted biopolymers were characterised using FTIR, H-NMR, STA, SEM/EDX, viscosity measurements, dynamic light scattering, and spectrophotometric assays of residual polyphenols and proteins. The optimised extraction conditions produced yields above 20% of high-purity alginate. When compared with commercial SA, the extracted materials showed comparable quality while relying on a simplified, solvent-reduced protocol that improves process efficiency and reduces the environmental impact. These results demonstrate that S. polyschides and S. muticum are promising, locally available sources of high-quality sodium alginate, and that industrially relevant yields (>20%) can be achieved through an environmentally conscious two-step extraction process.