Biotransformation pathway, growth inhibition, and biochemical response of Scenedesmus obliquus to brilliant green dye: Implications for bioremediation

Abstract

The potential of live microalgae Scenedesmus obliquus was tested for removing Brilliant green dye (BGD). BGD is a cationic dye that has been widely used as a colouring agent in various sectors, but this dye has been reported in wastewater due to its high solubility in water. Scenedesmus obliquus is one of the most widely employed microalgae species with good bioremediation potential and biochemical composition. This study reports growth inhibition of Scenedesmus obliquus in test runs 5 mg/L (17 %), 10 mg/L (31 %), 25 mg/L (42 %), and 50 mg/L (57 %), and the EC₅₀ value was predicted to be 33.7 mg/L using probit statistical analysis. The removal efficiency decreased from 99 % to 87 % as the BGD concentration increased, and the removal mechanism was reported in the order of biodegradation > bioaccumulation > bioadsorption. The biodegradation potential decreased from 97 % to 84 % at the BGD concentration of 50 mg/L, and the Monod kinetic study revealed that the half-saturation constant increased when the BGD concentration crossed the EC₅₀ value. Protein (498 mg/L) and lipid (728 mg/L) accumulation was highest at 5 mg/L of BDG, implying growth-stimulating effects on microalgae as the growth inhibition is less. These findings highlight Scenedesmus obliquus potential for effective BGD removal below EC₅₀ concentrations with identification of 6 biotransformed products and simultaneous production of value-added biomass.