Chemical Analysis and Antibacterial-Antibiofilm Properties of Waste Biomass of the Invasive Alga Species Rugulopteryx okamurae in Morocco

Since 2017, the invasive brown alga Rugulopteryx okamurae has posed significant biological, ecological, and socio-economic challenges in Morocco due to its rapid proliferation and biomass accumulation. This study investigates its antimicrobial and antibiofilm properties, along with its chemical composition. Methanol, chloroform, and ethyl acetate (EtOAc) extracts were evaluated for antibacterial activity against six human pathogens, including clinical and reference strains of Escherichia coli and Staphylococcus aureus. Fourier-transform infrared spectroscopy (FT-IR) analysis identified functional groups such as hydroxyl (O–H), carbonyl (C=O), and polysaccharides—indicative of the presence of bioactive compounds. Gas chromatography-mass spectrometry (GC-MS) revealed several key components: oleic acid butyl ester in the EtOAc extract, methyl tetradecanoate in the chloroform extract, and pentadecanoic acid methyl ester in the methanolic extract. Antibacterial potential was assessed using microdilution and growth curve assays, with minimal inhibitory concentrations (MICs) and minimal bactericidal concentrations (MBCs) ranging from 3.12 to 50mg/ mL. Growth curve analysis showed a bacteriostatic effect, demonstrated by extension of the lag phase and suppression of bacterial growth rates. Among the extracts, the EtOAc extract exhibited the highest antibiofilm activity, reducing biofilm formation by 73% in E. coli (clinical strain TT-23) and 70% in S. aureus (clinical strain 70). These findings suggest that R. okamurae harbors bioactive compounds with significant antibacterial and antibiofilm potential, offering not only a means to mitigate the ecological impacts of this invasive species but also promising applications in antimicrobial agent development.