A robust nitrifying community in a bioreactor at 50 °C opens up the path for thermophilic nitrogen removal.

The increasing production of nitrogen-containing fertilizers is crucial to meet the global food demand, yet high losses of reactive nitrogen associated with the food production/consumption chain progressively deteriorate the natural environment. Currently, mesophilic nitrogen-removing microbes eliminate nitrogen from wastewaters. Although thermophilic nitrifiers have been separately enriched from natural environments, no bioreactors are described that couple these processes for the treatment of nitrogen in hot wastewaters.

Empowering a mesophilic inoculum for thermophilic nitrification: Growth mode and temperature pattern as critical proliferation factors for archaeal ammonia oxidizers.

Cost-efficient biological treatment of warm nitrogenous wastewaters requires the development of thermophilic nitrogen removal processes. Only one thermophilic nitrifying bioreactor was described so far, achieving 200 mg N L(-1) d(-1) after more than 300 days of enrichment from compost samples. From the practical point of view in which existing plants would be upgraded, however, a more time-efficient development strategy based on mesophilic nitrifying sludge is preferred.

Nitric oxide preferentially inhibits nitrite oxidizing communities with high affinity for nitrite.

The prerequisite to the development success of the novel mainstream processes partial nitritation/anammox is the out-selection of nitrite oxidizing bacteria (NOB). A recent study suggested that this could be achieved through NO production by ammonium oxidizing bacteria under cyclic oxic-anoxic conditions. Indeed, it is known that among NOB, Nitrobacter species are reversibly inhibited by NO.

Trade-off between mesophilic and thermophilic denitrification: rates vs. sludge production, settleability and stability.

The development of thermophilic nitrogen removal strategies will facilitate sustainable biological treatment of warm nitrogenous wastewaters. Thermophilic denitrification was extensively compared to mesophilic denitrification for the first time in this study. Two sequential batch reactors (SBR) at 34 °C and 55 °C were inoculated with mesophilic activated sludge (26 °C), fed with synthetic influent in a first phase.

Optimized cryopreservation of mixed microbial communities for conserved functionality and diversity.

The use of mixed microbial communities (microbiomes) for biotechnological applications has steadily increased over the past decades. However, these microbiomes are not readily available from public culture collections, hampering their potential for widespread use. The main reason for this lack of availability is the lack of an effective cryopreservation protocol.