Temperature affects the oxidation kinetics of co-cultured Nitrobacter winogradskyi and Nitrobacter hamburgensis in nitrite-oxidizing bioreactor

Abstract Nitrobacter is an important chemolithoautotrophic nitrite-oxidizing bacteria and has exhibited potential for the oxidation of nitrite to nitrate in natural and engineered ecosystems. Microbial kinetics of Nitrobacter have been widely reported and are used to model the nitrite oxidation process and optimize the design parameters of the biological processes for wastewater treatment. However, limited information is available about the nitrite oxidation kinetics of the two coexisting Nitrobacter stains, namely the Nitrobacter winogradskyi and the Nitrobacter hamburgensis. The current work mainly focuses on the influence of temperature on the kinetic characteristics of the coexistence of N. winogradskyi and hamburgensis, which were enriched in a lab-scale sequencing batch reactor (SBR) through 419 operating cycles. The results for the kinetic properties of nitrite oxidation of the enrichments within the temperature range of 15–35 °C showed that the maximum specific rate (rmax), half-saturation coefficients (KS), growth-rate constants (μmax), and temperature coefficient (θ) lied within the ranges of 22.91–93.58 mM/g/d, 0.13–2.47 mM, 0.026–0.105 1/d, and 1.038–1.137, respectively. The maximum activity and nitrite affinities of tested microorganisms were sensitive to temperature. Furthermore, the relationships between temperature and normalized kinetic parameters (rmax, μmax, and θ) were developed as: 0.069T − 0.076 (15–30 °C), 0.0057T − 0.062 (15–30 °C), and 5.7 T 40.9 + T + T 2 10.5 (15–35 °C), respectively. Moreover, the capabilities of N. winogradskyi and N. hamburgensis to oxidize nitrite were lost at the temperature of 35 °C and were non-recoverable at temperature of 25 °C. Overall, the findings of the present work can provide available data for future study about the mathematic models of nitrification kinetics and ecological niche differentiation of Nitrobacter species.