title: Effect of culture residence time on substrate uptake and storage by a pure culture of Thiothrix (CT3 strain) under continuous or batch feeding.
abstract: A pure culture of the filamentous bacterium Thiothrix, strain CT3, was aerobically cultured in a chemostat under continuous acetate feeding at three different culture residence times (RT 6, 12 or 22 d) and the same volumetric organic load rate (OLR 0.12gCOD/L/d). Cells cultured at decreasing RT in the chemostat had an increasing transient response to acetate spikes in batch tests. The maximum specific acetate removal rate increased from 25 to 185mgCOD/gCOD/h, corresponding to a 1.8 to 8.1 fold higher respective steady-state rate in the chemostat. The transient response was mainly due to acetate storage in the form of poly(3-hydroxybutyrate) (PHB), whereas no growth response was observed at any RT. Interestingly, even though the storage rate also decreased as the RT increased, the storage yield increased from 0.41 to 0.50 COD/COD. This finding does not support the traditional view that storage plays a more important role as the transient response increases. The transient response of the steady-state cells was much lower than in cells cultured under periodic feeding (at 6 d RT, from 82 to 247mgCOD/gCOD/h), with the latter cells showing both storage and growth responses. On the other hand, even though steady-state cells had no growth response and their storage rate was also less, steady-state cells showed a higher storage yield than cells cultured under dynamic feeding. This suggests that in Thiothrix strain CT3, the growth response is triggered by periodic feeding, whereas the storage response is a constitutive mechanism, independent from previous acclimation to transient conditions.
authors.affiliation: Department of Chemistry, "Sapienza" University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy. Electronic address: francesco.valentino@uniroma1.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Valentino
authors.affiliation: Department of Chemistry, "Sapienza" University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Beccari
authors.affiliation: Department of Chemistry, "Sapienza" University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Marianna
authors.initials: M
authors.lastname: Villano
authors.affiliation: Water Research Institute (IRSA-CNR), National Research Council, Area della Ricerca Roma 1 Montelibretti, Via Salaria km. 29.300, 00015 Monterotondo (RM), Italy.
authors.forename: Valter
authors.initials: V
authors.lastname: Tandoi
authors.affiliation: Department of Chemistry, "Sapienza" University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy.
authors.forename: Mauro
authors.initials: M
authors.lastname: Majone
mesh_terms: D000085:Acetates / Q000378:metabolism; D057919:Biological Oxygen Demand Analysis; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D001709:Biotechnology; D006885:Hydroxybutyrates / Q000378:metabolism; D007700:Kinetics; D011091:Polyesters / Q000378:metabolism; D053525:Thiothrix / Q000254:growth & development / Q000378:metabolism*; D014865:Waste Disposal, Fluid / Q000379:methods; D062065:Wastewater / Q000382:microbiology; D000094122:Polyhydroxybutyrates
chemical_list: D000085:Acetates; D006885:Hydroxybutyrates; D011091:Polyesters; D062065:Wastewater; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates
keywords: Chemostat; Dynamic response; Organic load rate; PHB storage; Residence time; Thiothrix CT3