Continuous removal of the model pharmaceutical chloroquine from water using melanin-covered Escherichia coli in a membrane bioreactor.

Abstract

Environmental release and accumulation of pharmaceuticals and personal care products is a global concern in view of increased awareness of ecotoxicological effects. Adsorbent properties make the biopolymer melanin an interesting alternative to remove micropollutants from water. Recently, tyrosinase-surface-displaying Escherichia coli was shown to be an interesting self-replicating production system for melanin-covered cells for batch-wise absorption of the model pharmaceutical chloroquine. This work explores the suitability of these melanin-covered E. coli for the continuous removal of pharmaceuticals from wastewater. A continuous-flow membrane bioreactor containing melanized E. coli cells was used for adsorption of chloroquine from the influent until saturation and subsequent regeneration. At a low loading of cells (10 g/L) and high influent concentration of chloroquine (0.1 mM), chloroquine adsorbed until saturation after 26 ± 2 treated reactor volumes (39 ± 3 L). The average effluent concentration during the first 20 h was 0.0018 mM, corresponding to 98.2% removal. Up to 140 ± 6 mg chloroquine bound per gram of cells following mixed homo- and heterogeneous adsorption kinetics. In situ low-pH regeneration released all chloroquine without apparent capacity loss over three consecutive cycles. This shows the potential of melanized cells for treatment of conventional wastewater or highly concentrated upstream sources such as hospitals or manufacturing sites.