Experimental assessment of the performance of two marine coatings to curb biofilm formation of microfoulers

Biofilms formed on submerged marine surfaces play a critical role in the fouling process, causing increased fuel consumption, corrosion, and high maintenance costs. Thus, marine biofouling is a major issue and motivates the development of antifouling coatings. In this study, the performance of two commercial marine coatings, a foul-release silicone-based paint (SilRef) and an epoxy resin (EpoRef), was evaluated regarding their abilities to prevent biofilm formation by Cyanobium sp. and Pseudoalteromonas tunicata (common microfoulers). Biofilms were developed under defined hydrodynamic conditions to simulate marine settings, and the number of biofilm cells, wet weight, and thickness were monitored for 7 weeks. The biofilm structure was analyzed by confocal laser scanning microscopy (CLSM) at the end-point. Results demonstrated that EpoRef surfaces were effective in inhibiting biofilm formation at initial stages (until day 28), while SilRef surfaces showed high efficacy in decreasing biofilm formation during maturation (from day 35 onwards). Wet weight and thickness analysis, as well as CLSM data, indicate that SilRef surfaces were less prone to biofilm formation than EpoRef surfaces. Furthermore, the efficacy of SilRef surfaces may be dependent on the fouling microorganism, while the performance of EpoRef was strongly influenced by a combined effect of surface and microorganism.This research was funded by Base Funding - UIDB/00511/2020 of the Laboratory for Process Engineering, Environment, Biotechnology, and Energy - LEPABE - funded by national funds through the FCT/MCTES (PIDDAC), “CVMAR+i - Industrial Innovation and Marine Biotechnology Valorization” project, funded by INTERREG V Espanha Portugal (POCTEP) (0302_CVMAR_I_1_P), and UIDB/04423/2020 and UIDP/04423/2020 (CIIMAR). The research work was also supported by UIDB/04046/2020 and UIDP/04046/2020 research units grants, Portugal (to BioISI). R.T.-S. thanks the receipt of a junior researcher fellowship from the Project PTDC/BII-BIO/29589/2017 POCI-01-0145-FEDER-029589 funded by FEDER funds through COMPETE2020 - Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (PIDDAC) through FCT/MCTES. L.C.G. thanks the Portuguese Foundation for Science and Technology (FCT) for the financial support of her work contract through the Scientific Employment Stimulus-Individual Call-[CEECIND/01700/2017]. Atomic force microscopy technique was performed at the Biointerface and Nanotechnology i3S Scientific Platform with the assistance of Manuela Brás