The roles of Methylobacterium organophilum and Sphingomonas melonis for accelerating N-methyl pyrrolidone (NMP) biodegradation
Yongyi Gao, Ting Chen, Yifan Hou, Ruiyun Xue, Rui Liu, Fu Chen, Yongming Zhang, Bruce E. Rittmann
Abstract
Although N -methyl pyrrolidone (NMP) is biodegradable, normal activated sludge exhibits poor NMP biodegradation unless it is acclimated with NMP for an extended time. In this work, glucose-acclimated biomass (GAB) was acclimated with NMP for over two months to obtain NMP-acclimated biomass (NAB). NAB was superior to GAB for NMP biodegradation, and this correlated to higher abundances of the genera Mycobacterium , Amaricoccus , and Thauera in NAB. However, when GAB was bioaugmented with Methylobacterium organophilum or Sphingomonas melonis , which were isolated from NAB based on their growth on NAB, the bioaugmented GAB immediately showed rapid biodegradation of NMP. M. organophilum was superior to S. melonis for accelerating NMP biodegradation, and the acceleration of NMP biodegradation was proportional to the mass of M. organophilum or S. melonis added. A key finding was that the limiting step for NMP mineralization was biodegradation of monomethylamine , an NMP-biodegradation intermediate that also is inhibitory. Bioaugmenting M. organophilum or S. melonis accelerated NMP biodegradation by enhancing monomethylamine removal, with M. organophilum being superior to S. melonis . The documented rapid impact of bioaugmentation can make it especially valuable in response to an input of a toxicant.