Nitrate stimulation of N-Methylpyrrolidone biodegradation by Paracoccus pantotrophus: Metabolite mechanism and Genomic characterization

Due to the toxicological nature of N-methylpyrrolidone (NMP), the conventional anaerobic bioprocess is quite ineffective for NMP removal from wastewater. In order to achieve effective NMP biodegradation under anoxic condition, Paracoccus pantotrophus NJUST38 was isolated for the first time. The supplementation of nitrate into anoxic system resulted in complete removal of 5mM NMP by NJUST38 within 11 h compared to 24% in the anaerobic control system in the absence of nitrate. Genome characterization revealed that NMP biodegradation catalyzed by several key enzymes/genes, including N-methylhydantoin amidohydrolase (hyuB), methyltransferase (cobA), 4-aminobutyrate-2-oxoglutarate transaminase (gabT), succinate-semialdehyde dehydrogenase (gabD) and so on. NMP biodegradation pathway was proposed based on several intermediates, where NMP was biodegraded mainly for providing electrons and reducing power to support microbial denitrification through tricarboxylic acid (TCA) cycle. The proposed mechanism should aid our mechanistic understanding of NMP biodegradation by Paracoccus pantotrophus and the development of sustainable bioremediation strategies.