title: Effect of herbicide adjuvants on the biodegradation rate of the methylthiotriazine herbicide prometryn.
abstract: A microbial community, selected by its ability to degrade triazinic herbicides was acclimatized by successive transfers in batch cultures. Initially, its ability to degrade prometryn, was evaluated using free cells or cells attached to fragments of a porous support. As carbon, nitrogen and sulfur sources, prometryn, (98.8 % purity), or Gesagard, a herbicide formulation containing 44.5 % prometryn and 65.5 % of adjuvants, were used. In batch cultures, a considerable delay in the degradation of prometryn, presumptively caused by the elevated concentration of inhibitory adjuvants, occurred. When pure prometryn was used, volumetric removal rates remarkably higher than those obtained with the herbicide formulation were estimated by fitting the raw experimental data to sigmoidal decay models, and differentiating them. When the microbial consortium was immobilized in a continuously operated biofilm reactor, the negative effect of adjuvants on the rate and removal efficiency of prometryn could not be detected. Using the herbicide formulation, the consortium showed volumetric removal rates greater than 20 g m(-3) h(-1), with prometryn removal efficiencies of 100 %. The predominant bacterial strains isolated from the microbial consortium were Microbacterium sp., Enterobacter sp., Acinetobacter sp., and Flavobacterium sp. Finally, by comparison of the prometryn removal rates with others reported in the literature, it can be concluded that the use of microbial consortia immobilized in a biofilm reactor operated in continuous regime offer better results than batch cultures of pure microbial strains.
authors.affiliation: Departamento de Ingeniería Bioquímica, Escuela Nacional de Ciencias Biológicas, IPN., Prol. Carpio y Plan de Ayala, Col. Santo Tomás, 11340, Mexico, DF, México.
authors.forename: José Fernando
authors.initials: JF
authors.lastname: Pérez-Bárcena
authors.forename: Deifilia
authors.initials: D
authors.lastname: Ahuatzi-Chacón
authors.forename: Karla Lizzette
authors.initials: KL
authors.lastname: Castillo-Martínez
authors.forename: Nora
authors.initials: N
authors.lastname: Ruiz-Ordaz
authors.forename: Juvencio
authors.initials: J
authors.lastname: Galíndez-Mayer
authors.forename: Cleotilde
authors.initials: C
authors.lastname: Juárez-Ramírez
authors.forename: Oswaldo
authors.initials: O
authors.lastname: Ramos-Monroy
mesh_terms: D000192:Actinomycetales / Q000378:metabolism; D001673:Biodegradation, Environmental; D018441:Biofilms / Q000254:growth & development*; D019149:Bioreactors; D018914:Cells, Immobilized; D004754:Enterobacter / Q000378:metabolism; D005417:Flavobacterium / Q000378:metabolism; D006540:Herbicides / Q000378:metabolism*; D007700:Kinetics; D059013:Microbial Consortia / Q000502:physiology*; D015233:Models, Statistical; D011400:Prometryne / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D006540:Herbicides; D014874:Water Pollutants, Chemical; D011400:Prometryne