Aerobic nonylphenol degradation and nitro-nonylphenol formation by microbial cultures from sediments

Abstract

Nonylphenol (NP) is an estrogenic pollutant which is widely present in the aquatic environment. Biodegradation of NP can reduce the toxicological risk. In this study, aerobic biodegradation of NP in river sediment was investigated. The sediment used for the microcosm experiments was aged polluted with NP. The biodegradation of NP in the sediment occurred within 8 days with a lag phase of 2 days at 30 degrees C. During the biodegradation, nitro-nonylphenol metabolites were formed, which were further degraded to unknown compounds. The attached nitro-group originated from the ammonium in the medium. Five subsequent transfers were performed from original sediment and yielded a final stable population. In this NP-degrading culture, the microorganisms possibly involved in the biotransformation of NP to nitro-nonylphenol were related to ammonium-oxidizing bacteria. Besides the degradation of NP via nitro-nonylphenol, bacteria related to phenol-degrading species, which degrade phenol via ring cleavage, are abundantly present.

Fig. 1

Molecular structure of a nonylphenol and b ortho-nitro-nonylphenol

Scheme 1

Overview of transfers, dilution series, DNA samples, and clone libraries of samples with 11 μM pure branched nonylphenol (tNP) and linear NP (4-n-NP) crystals

Fig. 2

Degradation of branched NP (tNP) as C/C₀ in fifth-generation transfers from Huerva River sediment, Spain. In triplicate, closed squares A.5, closed circles B.5, closed diamonds C.5, and ex-mark sterile control

Fig. 3

GC-MS chromatogram of tNP and nitro-nonylphenol metabolite, including mass spectra

Fig. 4

Concentration profiles during branched NP (tNP) degradation in a batch system of the sixth-generation transfer. tNP in micromolar (tNP; left Y-axis, closed symbols) and nitro-nonylphenol in k counts (right Y-axis, open symbols). Closed and open squares A.6, closed and open circles B.6

Fig. 5

Denaturing gradient gel electrophoresis of sixth-generation transfers A.6 cultured with 11 μM tNP till t = 15 days and thereafter with 1 mM tNP, B.6 and C.6 incubated with 11 μM tNP, and fourth-generation transfer D.4 incubated with 1 mM tNP at different time intervals

Fig. 6

Principal component analysis scatter plot of DGGE profiles (Fig. 6) of sixth-generation transfers A.6 cultured with 11 μM tNP till t = 15 days and thereafter with 1 mM tNP, B.6 and C.6 incubated with 11 μM tNP, and fourth-generation transfer D.4 incubated with 1 mM tNP at different time intervals