title: Degradation of 2,4,6-trichlorophenol (2,4,6-TCP) by co-immobilization of anaerobic and aerobic microbial communities in an upflow reactor under air-limited conditions.
abstract: The co-immobilization and the culture of anaerobic and aerobic communities was tested for the mineralization of 2,4,6-trichlorophenol (2,4,6-TCP). At first, the anaerobic microorganisms (aggregated into granules) were cultivated in an upflow anaerobic sludge blanket (UASB) reactor, in a continuous mode, with glucose, propionate, acetate (COD loading rate = 0.5-2.0 g COD/l per day, ratio 1:1:1) and 2,4,6-TCP (2,4,6-TCP loading rate = 25-278 micromol/l per day) as substrates. 2,4,6-TCP was degraded into 2,4-DCP and 4-CP, but it was not mineralized because of the low degradation rates of 4-CP. Furthermore, the highest loading rates of 2,4,6-TCP (>126 micromol/l per day) caused the inhibition of the strains degrading the propionate. The granules were therefore tested in association with the aerobic community. They were immobilized in kappa-carrageenan/gelatin [2% (w/w) of each polymer] gel beads and cultivated in a reactor, on their own (to test the influence of the gel), and then with the aerobic community, under anaerobic and air-limited conditions, respectively. The results showed that (1) the gel did not influence the activity of the granules, (2) the anaerobic and aerobic communities could be easily co-immobilized in gel beads and cultivated in a reactor, (3) the mineralization of 2,4,6-TCP (2,4,6-TCP loading rate = 10-506 micromol/l per day), its intermediates of degradation and the other substrates [glucose + acetate + propionate (ratio 1:1:1) = COD loading rate = 500 mg COD/l per day] could be obtained under air-limited conditions if the culture parameters were strictly controlled [airflow = 36-48 vvd (volume of air/volume of liquid in the reactor per day), pH value at around 7.5]. Finally, the gel did not retain its structure during the whole culture (263 days) in the air-limited reactor, but the anaerobic and aerobic communities retained their activities and worked together for the mineralization.
authors.affiliation: Département de Génie Chimique, Université de Technologie de Compiègne, France.
authors.forename: H
authors.initials: H
authors.lastname: Gardin
authors.forename: J M
authors.initials: JM
authors.lastname: Lebeault
authors.forename: A
authors.initials: A
authors.lastname: Pauss
mesh_terms: D001420:Bacteria, Aerobic / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism*; D001421:Bacteria, Anaerobic / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism*; D001673:Biodegradation, Environmental; D019149:Bioreactors; D001709:Biotechnology / Q000379:methods*; D018914:Cells, Immobilized; D002733:Chlorophenols / Q000378:metabolism*; D003470:Culture Media; D017753:Ecosystem; D010084:Oxidation-Reduction
chemical_list: D002733:Chlorophenols; D003470:Culture Media; C024564:2,4,6-trichlorophenol