Monitoring and optimizing the biocatalytic degradation of efavirenz with immobilized Trametes versicolor laccase on Ti2NTx MXene: A lab-scale wastewater treatment plant process
Majahekupheleni Livileyise Malati, Adrian Mark Abrahams, Vongani Chauke, Mathapelo P. Seopela, Langelihle N. Dlamini
Abstract
The study presents efavirenz as a model antiviral drug for enhanced antiviral drug removal from wastewater using a combined activated sludge and biocatalytic degradation. The simulated lab-scale wastewater treatment was set up and monitored according to the OECD 303 A guidelines and connected to a recirculating bioreactor operated at optimal conditions. The biological treatment of efavirenz by the activated sludge was poor, as evidenced by the inadequate efavirenz removal at the end of days 30 and 35, which stood at 20.3% and 30.9% for 5 and 25 ppm spikes, respectively. Alternatively, the combined unit significantly reduced efavirenz concentrations to 38.1% and 40.9% by the end of days 30 and 35, highlighting its potency. The bioreactor contained Trametes versicolor laccase immobilised on Ti2NTx MXene biocatalyst with 256 U/mg laccase activity. The immobilisation resulted in a pH-tolerant biocatalyst which showed improved activity at multiple pH ranges (pH 4, 5.5 and 6.5) and reduced charge transfer resistance confirmed by EIS studies. At optimal conditions, the LC-MS studies showed six degradation fragments after 240 mins at 65% efavirenz degradation. At the same time, 85% degradation was achieved with six degradation fragments in 240 min with the laccase-assisted degradation using azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) as a mediator.