Screening and Degradation Mechanism of a Cold-Resistant Nitrobenzene-Degrading Microorganism

A cold-resistant nitrobenzene-degrading strain was screened from river sediment. The strain was identified as Methylobacillus glycogens, which has never been reported to be capable of degrading nitrobenzene. The degradation rates of 900 μg/L nitrobenzene reached respectively 99.3% and 88.6% in 144 h under both aerobic and anaerobic environments (30 mL inoculation volume at 12 ± 0.5 °C and pH7.0 ± 0.1). When aerobically degraded, nitrobenzene was firstly oxidized into o-nitrophenol, which was further oxidized into 1,2-benzenediol, meanwhile releasing NO2-. Then the 1,2-benzenediol was metabolized through either the ortho-cleavage into succinic acid and acetyl-CoA, or meta-cleavage into pyruvic acid and acetaldehyde, as well as other small molecule substances of non-toxicity or low-toxicity, which were finally decomposed into CO2 and H2O. When anaerobically degraded, nitrobenzene was firstly degraded into aniline (C6H5NH2), which was further degraded into 4-amino benzoic acid. The benzoic acid was degraded into benzoyl, which was finally metabolized and decomposed.