title: Acetoclastic methanogenic activity measurement by a titration bioassay.
abstract: A titration bioassay, designed to accurately determine the activity of acetoclastic methanogens, is described that also allows evaluation of inhibition due to potential toxicants on the active biomass. The instrument is made of a pH-stat connected to an anaerobic batch reactor. Acetate is blended and mixed with anaerobic sludge in the reactor where a 1:1 N2 and CO2 mixture is sparged at the beginning of each test. As the acetoclastic methanogens consume acetate, the pH increase, and the titration unit adds acetic acid and keeps the pH constant. The rate of titrant addition is directly proportional to the methanogenic activity. A very useful feature of the system is its potential to operate for long periods (days) at constant pH and substrate (acetate) concentration. The theoretical background and principle of operation are described as well as some of the practical problems encountered with the use of the instrument. Estimation of kinetic constants for an anaerobic culture according to the Michaelis-Menten model is presented. Examples of inhibition by inorganics (NaCl) and chlorinated solvents (chloroform) are also given.
authors.affiliation: Department of Hydraulic, Environmental, and Survey Engineering, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy. alberto.rozzi@polimi.it
authors.forename: Alberto
authors.initials: A
authors.lastname: Rozzi
authors.forename: Luca
authors.initials: L
authors.lastname: Castellazzi
authors.forename: Richard E
authors.initials: RE
authors.lastname: Speece
mesh_terms: D000085:Acetates / Q000737:chemistry / Q000378:metabolism*; D000693:Anaerobiosis; D019149:Bioreactors; D002021:Buffers; D002245:Carbon Dioxide / Q000378:metabolism; D002725:Chloroform / Q000494:pharmacology; D019605:Euryarchaeota / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008697:Methane / Q000037:antagonists & inhibitors / Q000378:metabolism*; D012722:Sewage / Q000382:microbiology; D012965:Sodium Chloride / Q000494:pharmacology; D012972:Sodium Hydroxide / Q000378:metabolism; D012996:Solutions; D017186:Titrimetry / Q000295:instrumentation / Q000379:methods
chemical_list: D000085:Acetates; D002021:Buffers; D012722:Sewage; D012996:Solutions; D002245:Carbon Dioxide; D012965:Sodium Chloride; D012972:Sodium Hydroxide; D002725:Chloroform; D008697:Methane