title: Implications of volatile fatty acid profile on the metabolic pathway during continuous sulfate reduction.
abstract: Volatile fatty acid (VFA) profile is an important parameter in anaerobic reactors because it enables the assessment of metabolic pathways. Volatile fatty acids were monitored during sulfate reduction in a UASB (upflow anaerobic sludge blanket) reactor treating 2g/L sulfate concentration and with the organic loading increasing from 3.5 kg COD/m(3)d to 5.9 kg COD/m(3)d, for a 1-day residence time. In the absence of recirculation, the best outcome (65% reduction) was noticed with the lowest organic loading (3.55 kg/m(3)d). When recirculation was applied, sulfate reduction yields increased to 89%, corresponding to a sulfate removal rate of 1.94 kg SO(4)(2-)/m(3)d. The reactor performance was discussed in relation to microbial diversity and metabolic pathways. At high organic loading, two metabolic pathways account for lactate degradation: (i) lactate is oxidized to acetate and carbon dioxide by the incomplete-oxidizer SRB (sulfate-reducing bacteria) Desulfomonas, Desulfovibrio, Desulfolobus, Desulfobulbus and Desulfotomaculum spp.; (ii) lactate is converted to acetate by fermenting bacteria such as Clostridium sp. High propionate concentrations imply that there are low sulfate reduction efficiencies.
authors.affiliation: Universidade Federal de Ouro Preto, Campus Morro do Cruzeiro, s.n., Ouro Preto 35400-000, MG, Brazil.
authors.forename: Sueli M
authors.initials: SM
authors.lastname: Bertolino
authors.forename: Isabel C B
authors.initials: IC
authors.lastname: Rodrigues
authors.forename: Renata
authors.initials: R
authors.lastname: Guerra-Sá
authors.forename: Sérgio F
authors.initials: SF
authors.lastname: Aquino
authors.forename: Versiane A
authors.initials: VA
authors.lastname: Leão
mesh_terms: D019149:Bioreactors / Q000382:microbiology; D003901:Desulfovibrio / Q000378:metabolism; D005232:Fatty Acids, Volatile / Q000378:metabolism; D005285:Fermentation / Q000502:physiology*; D019344:Lactic Acid / Q000378:metabolism; D011422:Propionates / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism*
chemical_list: D005232:Fatty Acids, Volatile; D011422:Propionates; D013431:Sulfates; D019344:Lactic Acid