Efficient degradation of the organic UV filter benzophenone-3 by Sphingomonas wittichii strain BP14P isolated from WWTP sludge

Abstract

Benzophenone-3 (BP3) is a widely used organic UV filter present in many environmental compartments. One way BP3 is released into the environment is through effluents from wastewater treatment plants (WWTPs). These plants are possible sources for degradation activity and WWTP sludge may potentially degrade BP3. Our goal was to identify any BP3 degrading microorganism(s) in WWTP sludge and to investigate whether the degradation was co-metabolic. Initial WWTP sludge microcosms spiked with BP3 showed 100% degradation after 20 days. Multiple transfers of these microcosms, while maintaining a strong selective pressure for BP3 degradation capabilities, resulted in the dominance of one bacterial strain. This strain was identified as Sphingomonas wittichii BP14P and was subsequently isolated. It was shown to degrade BP3 in a growth dependent manner. Strain BP14P utilized BP3 as the sole energy and carbon source and completely degraded BP3 after 7 days in minimal media. We tested the capability of BP14P to degrade nine other UV filters, but the degradation ability seemed to be restricted to BP3. However, whether this specificity is due to the lack of degradation genes, cellular transport or low bioavailability of the other UV filters remained unclear. The efficient degradation of BP3 by a group of bacteria well known for their potential for xenobiotic degradation is an important step forward for a complete risk assessment of the long-term environmental impact of BP3.