Seaweeds as a promising resource for blue economy development in Tunisia : current state, opportunities, and challenges

Many western countries show an increased interest in using algae in several sectors such as human food and animal feed, nutraceuticals, cosmetics and pharmaceuticals, agriculture, or bioenergy. Biomass of marine origin, and especially seaweed, is a key element for blue growth and is expected to contribute to the development of the growing European blue economy. Several Research and Development and Research and Innovation Projects result in the establishment of an emerging seaweed aquaculture in the Northern European countries. However, macroalgal cultivation and bioprocessing is still scarce in the Mediterranean area, particularly in Tunisia, where seaweeds are abundant on its coast, they remain little exploited. Ongoing projects from different research institutes focus on biological activities of macroalgae, the extraction of active compounds, and the potential uses as phycocolloids, pigments, lipids, and bioactive metabolites characterization as well as bioproduct enhancement. The results of these investigations demonstrate that macroalgae from the Tunisian coasts are a source of valuable compounds and that they can be used as a natural renewable resource suitable for a large array of industrial applications. Further to this, specific research activities on seaweed cultivation have been conducted particularly for Gracilaria and Ulva. In this paper, we highlight the potential of the seaweed sector in Tunisia in terms of biodiversity, cultivation, and bioprocessing and discuss the challenges in various sectors, i.e., biology, building capacity, technology, or policy, that currently hinder the expansion of a sustainable Tunisian seaweed industry

The Mechanism of Heavy Metal Biosorption on Green Marine Macroalga Enteromorpha linza

The biosorption mechanism of divalent Ni(II), Cd(II), and Pb(II) ions onto calcium treated Entemorpha linza was investigated as a function of pH, contact time, biomass dose, and temperature. The experimental data were evaluated by Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models. The uptake capacity of the tested metal ions was markedly influenced by pH in the range of 2-3.5 and maximum rates were observed at pH 5-5.5. The kinetics of the metal ions adsorption were rather rapid, with 90% of adsorption occurring within 10min. In addition to batch sorption tests, the functional groups on the cell wall matrix of the biomass were revealed by potentiometric titration data and Fourier transform infrared analysis. The relative contribution of the chemical groups involved in metal biosorption such as carboxyl, amino, sulfonate was evaluated to characterize their binding mechanisms using these instrumental techniques. The density of strong and weak acidic functional groups in the biomass was found to be 0.25 and 0.95mmolg(-1) biomass, respectively. In conclusion, the present work showed that the marine algae E. linza could be used as a potentially cost-effective biosorbent for the treatment of complex wastewater containing heavy metals