Biodegradation of polyurethane plastic monomer 4,4′-methylenedianiline by Rhodococcus sp. YXP8

The 4,4′-methylenedianiline (MDA) is an important precursor in the production of polyurethane plastic. The environmental release of MDA poses a threat to plants, animals, and humans. Microorganisms exert an important role in degrading xenobiotic compounds. However, only several MDA-degrading microbes are reported, and the molecular mechanism of MDA degradation remains unclear. In this work, a Gram-positive MDA-degrading bacterium Rhodococcus sp. YXP8 was first obtained from the surface of polyurethane waste. This strain could degrade 20 mg·L⁻¹ MDA at 30 °C and pH 7.0 within 4 days and showed good degradation ability (>70 %) within a wide pH range from 5.0 to 10.0. The results of liquid chromatograph-tandem mass spectrometer analysis indicate that strain YXP8 transformed MDA to two final products of 4-aminophenylacetic acid and (Z)-3-amino-2-hydroxypenta-2,4-dienoic acid. The catabolic pathway of MDA in bacteria was demonstrated for the first time. Strain YXP8 could efficiently remediate MDA-contaminated natural water, eliminating its risk to aquatic organisms. Taken together, this work presents a bacterium with potential for biological treatment of MDA pollutants and for mining genetic determinants of MDA degradation.