Removal of paralytic shellfish toxins from marine aquatic systems.

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The potential of Chitosan-Based composites for adsorption of diarrheic shellfish toxins

Publication . Leal, Joana F.; Amado, Patrícia; P. Lourenço, J.; Lurdes Santos Cristiano, Maria

Okadaic acid (OA) is one of the most potent marine biotoxins, causing diarrheal shellfish poisoning (DSP). The proliferation of microalgae that produce OA and its analogues is frequent, threatening human health and socioeconomic development. Several methods have been tested to remove this biotoxin from aquatic systems, yet none has proven enough efficacy to solve the problem. In this work, we synthesized and characterized low-cost composites and tested their efficacy for OA adsorption in saltwater. For the synthesis of the composites, the following starting materials were considered: chitosan of low and medium molecular weight (CH-LW and CH-MW, respectively), activated carbon (AC), and montmorillonite (MMT). Characterization by vibrational spectroscopy (FTIR), X-ray diffraction (XRD), and microscopy revealed differences in the mode of interaction of CH-LW and CH-MW with AC and MMT, suggesting that the interaction of CH-MW with MMT has mainly occurred on the surface of the clay particles and no sufficient intercalation of CH-MW into the MMT interlayers took place. Among the composites tested (CH-LW/AC, CH-MW/AC, CH-MW/AC/MMT, and CH-MW/MMT), CH-MW/MMT was the one that revealed lower OA adsorption efficiency, given the findings evidenced by the structural characterization. On the contrary, the CH-MW/AC composite revealed the highest average percentage of OA adsorption (53 ± 11%). Although preliminary, the results obtained in this work open up good perspectives for the use of this type of composite material as an adsorbent in the removal of OA from marine environments.

2024-04-21Journal article

Open access

Why are bivalves not detoxified?

Publication . Leal, Joana F.; Cristiano, Maria de Lurdes

Paralytic (PSP), diarrheic (DSP), and amnesic shellfish poisonings are among the most prominent foodborne diseases threatening the food security. Because of the absence of legal methods capable of eliminating these biotoxins, the option is to rely on natural detoxification, compromising the availability of protein-based food and imposing severe socioeconomic impacts. In vivo detoxification methodologies have focused on the use of adsorbents (mainly applied to PSP), some of which are combined with nontoxic algae. Alternative methodologies for DSP have emerged, but they are based on absorption inhibition, which may be unfeasible in real situations. It is thus imperative to optimize existing proposals or develop novel, safe, and cost-effective methods so that the solution is seen as an attractive financial investment.

2024-06Journal article

Open access