Biodegradation of propanil by Acinetobacter baumannii DT in a biofilm-batch reactor and effects of butachlor on the degradation process

Degradation of butachlor and propanil by Pseudomonas sp. strain But2 and Acinetobacter baumannii strain DT

Herbicides have been extensively used globally, resulting in severe environmental pollution. Novel butachlor-degrading Pseudomonas sp. strain But2 isolated from soil can degrade butachlor regardless of the concentration and grows without a lag phase. Specific degradation was increased at 0.01-0.1 mM, and did not change significantly at higher concentrations. During degradation, 2-chloro-N-(2,6-diethylphenyl) acetamide, 2,6-diethylaniline, and 1,3-diethylbenzene were formed, which indicated that deamination occurred. Moreover, Pseudomonas sp. strains could tolerate propanil at up to 0.8 mM. The mixed bacterial culture of Pseudomonas sp. But2 and Acinetobacter baumannii DT (a propanil-degrading bacterial strain) showed highly effective biodegradation of both butachlor and propanil in liquid media and soil. For example, under treatment with the mixed culture, the half-lives of propanil and butachlor were 1 and 5 days, respectively, whereas those for the control were 3 and 15 days. The adjuvants present in herbicides reduced degradation in liquid media, but did not influence herbicide removal from the soil. The results showed that the mixed bacteria culture is a good candidate for the removal of butachlor and propanil from contaminated soils.

Anaerobic Degradation of Propanil in Soil and Sediment Using Mixed Bacterial Culture

The widespread use of the herbicide, propanil, causes severe environmental problems. In this study, the effects of propanil on the bacterial community in a sediment slurry were determined. Moreover, the degradation of the herbicide by pure and mixed cultures was first conducted under anaerobic conditions. The results showed that propanil caused significant changes in the bacterial community under anaerobic conditions. Four bacterial strains, i.e., Geobacter sp. Pr-1, Paracoccus denitrificans Pr-2, Pseudomonas sp. Pr-3, and Rhodococcus sp. Pr-4, isolated from the an enrichment sediment slurry were the first pure cultures that degraded propanil and 3,4-dichloroaniline (3,4-DCA) under anaerobic conditions. Some individual isolates showed the slow degradation of propanil and 3,4-DCA, but the mixture of the four strains increased the degradation rates of both compounds. The mixed culture of these isolates transformed more than 90% of propanil within 10 days in liquid media with the amendment of dextrose, glucose, or acetate. The determination of degradation pathway showed that propanil was transformed to 3,4-DCA and some other products before degrading completely. This study provides valuable information on the effects of propanil on the bacterial community and the synergistic degradation of propanil under anaerobic conditions.