Erythromycin degradation by esterase (EreB) in enzymatic membrane reactors

• Free and immobilized EreB exhibited an effective removal of Erythromycin.
• Effect of pH and temperature on EreB activity.
• Different enzymatic membrane reactor configurations for Erythromycin depletion.
• Good stability of active membranes for erythromycin degradation in an enzymatic membrane reactor.

Erythromycin is an antibiotic considered as a recalcitrant pollutant because it is currently found in treated wastewaters. In addition, traces of antibiotics are a threatening ecological issue as these compounds are biologically active even at very low concentrations (ng L−1). In this work, we studied enzymatic degradation of this antibiotic in model aqueous solutions containing 20 mg L−1 erythromycin. We used as the biocatalyst an EreB esterase obtained from a genetically modified Escherichia coli W3110 strain carrying the EreB overexpression plasmid. Experiments were carried out with different reactor and biocatalyst configurations (free and immobilized by covalent grafting or adsorption). Free enzymes showed very high activity leading to erythromycin depletion. Experiments with the biocatalyst immobilized by adsorption using an enzymatic membrane reactor showed that even if EreB initially lost part of its activity, it was stabilized and able to continuously degrade erythromycin at a rate of 15.8 mg h−1 for 100 h.