Biodegradation of fluoroquinolone antibiotics by laccase enzyme extracted from spent mushroom waste (SMW) of Pleurotus florida and its immobilization on biochar derived from SMW: a sustainable approach

Abstract

It is crucial to develop urgent and innovative strategies for removing persistent organic micropollutants (OMPs) from soil, groundwater, and surface water. Antibiotics commonly found in contaminated soils and wastewater treatment plant effluents are classified as environmentally persistent pharmaceutical pollutants (EPPPs). These pollutants pose serious ecological threats to non-target species. Since conventional wastewater treatment plants (WWTPs) cannot completely eradicate these pollutants, the excessive use of antibiotics has a negative impact on the environment's ability to regenerate and recover. In recent years, various water bodies such as surface water, tap water, groundwater, common wastewater treatment plants, and rivers persist fluoroquinolone antibiotic residues specifically ciprofloxacin, levofloxacin, and norfloxacin. To address this pressing issue, it is essential to develop alternative, sustainable remediation strategies that can effectively degraded theses pollutants. This study explores an innovative approach to antibiotic bioremediation using spent mushroom waste (SMW), a type of agro-waste. SMW, a byproduct of mushroom cultivation, is rich in ligninolytic enzymes like laccase and peroxidase, which facilitate the biodegradation of complex organic pollutants. The tri-nuclear cluster of copper ions in the laccase enzyme has excellent oxidizing capacity for organic and inorganic compounds. However, its low reduction potential limits its ability to oxidize non- phenolic compounds. To address this limitation, small-sized mediators (both synthetic and natural mediators) are used to bind to the enzyme's active site, reducing steric hindrance. By adjusting the reaction conditions like pH, temperature, and mediator concentration, this study aims to optimize laccase output from Pleurotus florida SMW.