Optimization of Pleurotus ostreatus as a potent bioremediation agent for the removal of methylene blue dye in wastewater

Abstract

The widespread use of methylene blue (MB) as a cationic thiazine dye in the textile and chemical industries has raised environmental concerns due to its high stability against biodegradation. The persistence of MB in aquatic ecosystems is due to its complex aromatic structure and cationic nature, which make it highly resistant to natural degradation. Its persistence in water has been linked to toxic effects on living organisms and disruption of the ecological balance of aquatic ecosystems. Several methods use white rot fungi and other organisms for dye degradation, therefore becoming a hot topic of research lately. The present study is aimed at identifying the optimum conditions for the growth of Pleurotus ostreatus in terms of pH, temperature, and incubation time for maximum biomass production. The study further investigates the efficacy of the fungus, P. ostreatus , together with laccase-inducing substances such as copper sulfate, tannic acid, ethanol, Tween-80 and gallic acid, for the efficient elimination of the cationic methylene blue dye. The fungus was cultivated with different laccase inducers and varying concentrations of methylene blue dye. The extent of dye removal under different experimental treatments was evaluated based on the degree of dye decolorization. The treatment having P. ostreatus in media along with tannic acid (TA) was the most efficient in methylene blue removal, with rates as high as 99 ± 0.54%. It was also observed that P. ostreatus , along with the other inducer treatments, performed better than the control treatment at lower MB concentrations. This implies that P. ostreatus has the potential of being a reliable biosorbent and bioremediation agent in the process of textile dye removal. Also, compounds such as TA and copper sulfate may then be used to enhance its performance by stimulating its ligninolytic enzyme system.