The Antarctic vascular plant Colobanthus quitensis has developed unique mechanisms to survive in extreme environmental conditions, such as high UV-B radiation and nutrient scarcity. This study evaluated the effects of immersion frequency in a temporary immersion bioreactor (TIB) on biomass growth, phenolic compound accumulation, and flavonoid synthesis. Plants subjected to 24-hour immersion pulses exhibited the highest biomass yield (192.7%), phenylalanine ammonia-lyase (PAL) activity (52 μkats/kg protein), and total phenolic content (TPC; 40 mg GAE/g dry weight). Flavonoids such as neoschaftoside, saponarin, and schaftoside significantly accumulated under these conditions, demonstrating the metabolic shift induced by controlled nutrient deprivation and improved aeration. The findings highlight that intermittent stress optimises secondary metabolite production, providing a sustainable pathway for bioactive compound extraction. These phenolic metabolites have potential applications in agriculture as antifungal agents, in cosmetics for UV-B protection, and functional foods as antioxidants. This study underscores the relevance of TIB systems as scalable and efficient tools for enhancing plant-derived bioactive compounds, contributing to sustainability across various industries.

Keywords: Colobanthus quitensis; Phenolic Compounds; Temporary Immersion Bioreactor; Flavonoids; Bioactive Metabolites;