Evaluation of Deep Eutectic Systems as anti-biofouling agents

• Autor(a) principal: Amador, Sandro Ivan Santos
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/163519
• topic: Antifouling; Maritime pollution; Ecotoxicity; Sustainable antifouling coatings; Bioactive compounds; Domínio/Área Científica::Engenharia e Tecnologia::Engenharia Química

Biofouling refers to the colonization of immersed surfaces by living organisms, with nefarious consequences for sea-based industry and the environment, through increased fuel consumption and greenhouse gas emissions and facilitated spread of invasive species. Current antifouling coatings comprise the use of heavy metal oxides like zinc and copper, both known to be toxic for the environment. With a growing pressure for green alternatives, a new idea based on green chemistry is proposed, the use of natural deep eutectic systems (NADES). Several formulations based on bioactive terpenes and fatty acids were produced and two were selected for further trials, menthol:oleic acid (1:1) – M:OL (1:1) - and thymol:oleic acid (1:1) – T:OL (1:1). These were successfully characterized under polarized optical microscopy analysis. They were shown not to affect the tissues of Palaemon varians, and in inert paint, pure compounds and NADES were not toxic for brine shrimp at their highest concentrations. NADES did not affect biofouling related enzymes in more than 50%. Pure terpenes had the highest antimicrobial activity, but NADES were selective in inhibiting biofilm without harming bacteria. Thymol and T:OL (1:1) faired best in inhibiting the QS mechanism and impeding the growth of selected microalgae. All samples showed some toxicity against medusa polyps, but T:OL (1:1) and pure menthol showed capability of inhibiting settlement without death. Ocean trials showed NADES coated plates were less colonized than all other plates despite no weight differences, where T:OL (1:1) presented the lesser number of adhered organisms. Despite the variability in sample bioactivity comparing all assays, NADES, and T:OL (1:1) in specific, presented the best overall antifouling activity with less toxicity, cementing the use of a conjoined multispecies lab and field assay strategy while further indicating the possibility of using NADES as sustainable anti-biofouling agents without compromising the surrounding marine environment.