Mineralization of LCFA associated with anaerobic sludge: Kinetics, enhancement of methanogenic activity, and effect of VFA.
Long-chain fatty acids (LCFA) associated with anaerobic sludge by mechanisms of precipitation, adsorption, or entrapment can be biodegraded to methane. The mineralization kinetics of biomass-associated LCFA were established according to an inhibition model based on Haldane's enzymatic inhibition kinetics. A value around 1,000 mg COD-LCFA..g VSS(-1) was obtained for the optimal specific LCFA content that allowed the maximal mineralization rate. For sludge with specific LCFA contents of 2,838 +/- 63 and 4,571 +/- 257 mg COD-LCFA..g VSS(-1), the specific methanogenic activities in the presence of acetate, butyrate, and H(2)/CO(2) were significantly enhanced after the mineralization of the biomass-associated LCFA. For sludge with a specific LCFA content near the optimal value defined by the kinetic model, the effect of adding VFA to the medium was studied during the mineralization of the biomass-associated LCFA. Different patterns were obtained for each individual substrate. Acetate and butyrate were preferentially consumed by the consortium, but in the case of propionate no evidence of a sequential consumption pattern could be withdrawn. It was concluded that LCFA do not exert a bactericidal neither a permanent toxic effect toward the anaerobic consortia. A discussion is addressed to the relative roles of a reversible inhibitory effect and a transport limitation effect imposed by the LCFA surrounding the cells.
Centro de Engenharia Biológica, Universidade do Minho, 4710-057 Braga, Portugal.
M A
MA
Pereira
D Z
DZ
Sousa
M
M
Mota
M M
MM
Alves
D001421:Bacteria, Anaerobic / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology*; D018929:Cell Culture Techniques / Q000379:methods; D003198:Computer Simulation; D005232:Fatty Acids, Volatile / Q000378:metabolism*; D007700:Kinetics; D008697:Methane / Q000378:metabolism*; D008903:Minerals / Q000378:metabolism*; D008954:Models, Biological; D019301:Oleic Acid / Q000378:metabolism*; D012722:Sewage / Q000382:microbiology*
D005232:Fatty Acids, Volatile; D008903:Minerals; D012722:Sewage; D019301:Oleic Acid; D008697:Methane