Microalgal cocultivation driven phycoremediation of Congo red: integrated biochemical profiling and LC–MS guided mechanism

Abstract

This study investigates the potential of the Microalgae-Microalgae (MM) cocultivated system as a sustainable phycoremediation strategy for the biodegradation and decolourization of the diazo dye congo red (CR). Decolourization was confirmed by UV–Vis spectrophotometry and FT-IR spectroscopy, with the cocultivated microalgal system achieving a maximum removal efficiency of 100% at a concentration below 20 mg L⁻¹, which gradually decreased with increasing contact time and reached 54% at an initial dye concentration of 100 mg L⁻¹. Beyond this concentration, the removal capacity plateaued. LC–MS analyses enabled the identification of key degradation intermediates, from which a plausible biocatalytic mechanism for CR breakdown was proposed. In addition, the biochemical response of the cocultivated system to CR exposure revealed a biphasic effect, indicating both adaptive metabolic regulation and stress-induced alterations. Overall, the findings demonstrate that the microalgal cocultivation system possesses significant decolourization capability under static conditions and offers a promising, low-energy approach for the remediation of dye-contaminated wastewater.