Production de l`agar-agar à partir des algues marines

Abstract

This study investigates the extraction of agar-agar from two species of red algae, Gelidium sp and Gracilaria spp, harvested from the Algerian coastline. A traditional process involving alkaline pretreatment with 5% NaOH and thermal boiling was applied. Gelidium yielded 60%, while Gracilaria yielded 40%, with better gelling strength observed in Gelidium.However, both crude extracts exhibited lower quality than commercial agar due to the presence of residual proteins, pigments, and salts. Gelling performance was tested on nutrient broth (BN) and potato dextrose agar (PDA), where Gelidium outperformed Gracilaria but required higher concentrations to form firm gels. A microbial fertility test showed moderate bacterial and fungal growth, confirming the media's viability.The yield values may be overestimated due to residual moisture content and lack of proper drying at 105°C. The study recommends further purification using dialysis or enzymatic techniques to enhance gel quality and consistency. Ultimately, this research reveals promising potential for exploiting Algerian marine algal resources to develop a competitive national agar industry, reducing dependence on imports and supporting local bio-industrial applications.