title: Biological treatment of propanil and 3,4-dichloroaniline: kinetic and microbiological characterisation.
abstract: Propanil (3,4-dichloropropionanilide) is a widely used herbicide, applied worldwide in rice paddies. Propanil is primarily transformed in nature to 3,4-dichloroaniline (DCA), which is more slowly biodegradable. Both compounds have adverse health and ecotoxicity effects. This work investigated the microbial ecology and kinetics of propanil-degrading enrichments obtained from soil in a sequencing batch reactor (SBR) operated with different feeding strategies, aiming at the enhanced biological removal of propanil and DCA from contaminated waters. During SBR operation with a dump feeding strategy, a high propanil concentration led to DCA accumulation, which was only fully degraded after 5 days, likely due to DCA inhibition. For this reason, the operational mode was changed to fed-batch operation with lower initial propanil concentrations, which resulted in faster propanil and DCA biodegradation. Thus a fed-batch operation seems more appropriate for the acclimatisation of an effective propanil- and DCA-degrading population. The changes in performance were accompanied by a shift in the microbial population structure, as determined by DGGE of the 16S rRNA gene, particularly after a feed of DCA as the sole carbon source. Isolates obtained from the acclimatised population included members of the genera Enterococcus and Rhodococcus, as well as Brevundimonas, which displayed >90% propanil biodegradation efficiency.
authors.affiliation: REQUIMTE/CQFB, Chemistry Department, FCT, Universidade Nova de Lisboa (UNL), 2829-516 Caparica, Portugal.
authors.forename: G
authors.initials: G
authors.lastname: Carvalho
authors.forename: R
authors.initials: R
authors.lastname: Marques
authors.forename: A R
authors.initials: AR
authors.lastname: Lopes
authors.forename: C
authors.initials: C
authors.lastname: Faria
authors.forename: J P
authors.initials: JP
authors.lastname: Noronha
authors.forename: A
authors.initials: A
authors.lastname: Oehmen
authors.forename: O C
authors.initials: OC
authors.lastname: Nunes
authors.forename: M A M
authors.initials: MA
authors.lastname: Reis
mesh_terms: D000814:Aniline Compounds / Q000302:isolation & purification*; D001419:Bacteria / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification / Q000378:metabolism*; D001673:Biodegradation, Environmental; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology; D058645:Denaturing Gradient Gel Electrophoresis; D007700:Kinetics; D010802:Phylogeny; D025341:Principal Component Analysis; D011411:Propanil / Q000302:isolation & purification*
chemical_list: D000814:Aniline Compounds; C014464:3,4-dichloroaniline; D011411:Propanil