Isolation, Identification And Biodegradation Characteristics Of A Nonylphenol Degradating Bacterial Strain

At present, a number of rivers are polluted by Endocrine Disrupting Chemicals (EDCs). Because of their high toxicity, more and more attention has been paid to the problem.Nonylphenol (NP) is one of the representative endocrine disrupting chemicals and persistent toxic pollutants, with obvious estrogenic activity and high bioaccumulation in body. Nonylphenol in water is mainly genereated by the degradation of nonylphenol polyethoxylates, which is widely used as nonionic surfactant in various industries. It was reported that large amount of such surfactant was let into nature, and more and more rivers were polluted by NP, and it has become a big international problem.There were 4, 13 and 17 bacterial strains isolated from activated carbon, which was processed with sand filtered water from Songhua River for long time, pre-oxidized with ozone and ferrate respectively, and it demonstrated that treatment effect of water pre-oxidized with ferrate was better than that of pre-oxidized with ozone.A bacterial strain NP-1, capable of utilizing nonylphenol (NP) as solo carbon source, was isolated using mimeral salt medium (MSM) by adding NP as solo carbon source, and the bacterial strain was from the ozone-activated carbon column. Under conditions of pH 6.0, 30℃, 140r/min, and 2% of inoculum amount, the strain could biodegrade 59% of 1.0 mg/L NP, and the biodegradation reaction fitted well with first-order kinetic model, with a degradation rate constant (k) of 0.0865d^-1) and a half-live (t_1/2) of 8.0d.The bacterial strain was gram-positive, and was bacillus without flagella, and the size was 1.77×0.64μm. The bacterial strain was identified as Rhodococcus-erythropolis with the Sherlock Microbial Identification System (MIS) from the MIDI Corporation.Many factors were studied in shaking flasks, and the optimal conditions for NP biodegradation were at 30℃and pH 6.0. Aerobic degradation rate was inert to the original NP concentration, but was highly enhanced by increased inoculum amount. The aerobic degradation rate for NP was also enhanced by increased level of NH₄⁺, Mn²⁺, Mg²⁺, and NaCl, and by addition of glucose, NaAc, and yeast extract, as well as by reduced level of Ca²⁺, Cu²⁺, Fe²⁺, and phosphate. The combination of NP- with other bacterial strains which were also isolated from activated carbon expressed better biodegradation effectiveness and could adapt to environment more easily.This study isolated a NP biodegradation bacterial strain from activated carbon in the long-running drinking water treatment system for the first time, and explored NP biodegradation principles, and provided some reference for NP removal in water.