Stoichiometric and kinetic characterisation of Nitrobacter in mixed culture by decoupling the growth and energy generation processes

Abstract

The growth, maintenance and lysis processes of Nitrobacter were characterised. A Nitrobacter culture was enriched in a sequencing batch reactor (SBR). Fluorescent in situ hybridisation showed that Nitrobacter constituted 73% of the bacterial population. Batch tests were carried out to measure the oxygen uptake rate and/or nitrite consumption rate when both nitrite and CO2 were in excess, and in the absence of either of these two substrates. The results obtained, along with the SBR performance data, allowed the determination of the maintenance coefficient and in situ cell lysis rate of Nitrobacter. Nitrobacter spends a significant amount of energy for maintenance, which varies considerably with the specific growth rate. At maximum growth, Nitrobacter consume nitrite at a rate of 0.042 mgN/mgCOD(biomass) . h for maintenance purposes, which increases more than threefold to 0.143 mgN/mgCOD(biomass) . h in the absence of growth. In the SBR, where Nitrobacter grew at 40% of its maximum growth rate, a maintenance coefficient of 0.113 mgN/mgCOD . h was found, resulting in 42% of the total amount of nitrite being consumed for maintenance. The above three maintenance coefficient values obtained at different growth rates appear to support the maintenance model proposed in Pirt (1982). The in situ lysis rate of Nitrobacter was determined to be 0.07/day under aerobic conditions at 22 degrees C and pH 7.3. Further, the maximum specific growth rate of Nitrobacter was estimated to be 0.02/h (0.48/day). The affinity constant of Nitrobacter with respect to nitrite was determined to be 1.50 mgNO2(-)-N/L, independent of the presence or absence of CO2.

Start-up of a nitrification system with automatic control to treat highly concentrated ammonium wastewater: Experimental results and modeling

“…Heterotrophic bacteria were also included to be able to describe the total biomass concentration since it has been shown that enriched nitrifying systems have a relatively high content of heterotrophic bacteria [18,19] and furthermore, the influent of the real system contained some COD. Six soluble compounds were considered (as concentration in the bulk liquid): total ammonia nitrogen (S TAN ), total nitrite nitrogen (S TNN ), nitrate (S NO 3 ), soluble biodegradable organic nitrogen (S ND ), dissolved oxygen (S O ) and readily biodegradable organic matter (S S ).…”

Evaluation on factors influencing the heterotrophic growth on the soluble microbial products of autotrophs

“…Despite of their differences, heterotrophs and autotrophs coexist in activated sludge in wastewater treatment systems used to remove organic and nitrogen simultaneously. Vadivelu et al (2006) enriched a Nitrobacter culture in a sequencing batch reactor (SBR) fed with nitrite as the sole energy source and bicarbonate as the sole carbon source. Fluorescent in situ hybridization (FISH) showed that Nitrobacter constituted 73% of the bacterial population, suggesting that a great amount of heterotrophs were also present in this nitrifying enriched sludge.…”

Carbon Conversion Efficiency and Limits of Productive Bacterial Degradation of Methyl tert -Butyl Ether and Related Compounds

“…There is less agreement in which direction the rate influences m. Pirt (38) introduced a growth-rate-dependent term for increased maintenance at slower growth. Recent experiments with Nitrobacter growing at maximum rates of 0.02 h Ϫ1 , i.e., similar to those observed with MTBE, supported this model (57). Other examples with Nitrobacter indicated a difference in maintenance requirements for cultures grown in a chemostat as opposed to reactors with biomass retention (55).…”