Biodegradation of pyrene by a novel strain of Castellaniella sp. under denitrifying condition

Abstract

Pyrene, a four-ring PAHs, is a typical pollutant in coking wastewater, which is difficult to biodegrade in the conventional biological wastewater treatment processes. Biodegradation of pyrene coupled with denitrification process is an effective approach for treating coking wastewater due to simultaneous removal of toxic organic pollutants and nitrate. In this study, a novel strain capable of degrading pyrene was isolated from the activated sludge of a local coking wastewater treatment plant and identified to be Casterllaniella sp. based on 16S rRNA gene sequence analysis. It can degrade pyrene under denitrifying condition. The degradation efficiency of pyrene reached 97.2% when pyrene concentration was 100 mgL−1. According to the analysis of electron transformation process, about 50% of pyrene was degraded using nitrate as electron acceptor. During pyrene degradation process, almost no intermediate products were detected by GC-MS with the detection limit of 0.1 ngL−1 perhaps due to the complete degradation of pyrene. The SDS-PAGE analysis showed that the proportion of 6 proteins increased during pyrene degradation, and 4 proteins could be considered as enzymes involved in pyrene degradation. The analysis of intermediate products and proteins suggested that pyrene degradation under anoxic condition by Castellaniella sp. Pyr2 was different from other aerobic pathways. Furthermore, this strain has potential for the practical application of simultaneous removal of pyrene and nitrate from coking wastewater.