Aerobic Anaerobic Conditions Research Articles

Development of stable denitrifying cultures during repeated aerobic-anaerobic transient periods

The influence of repeated alternating aerobic-anaerobic growth conditions on the development of stable denitrification activity was studied with continuous cultures of Paracoccus denitrificans and with activated sludge. Denitrification activity was determined by measuring the formation of intermediates and by analysis of mRNAs for the individual dentrification enzymes. Primarily, the length of the anaerobic period influenced the synthesis of the denitrification enzymes of P. denitrificans. When the anaerobic period was 24 h, the cultures reached stable denitrification activity within the first anaerobic phase. Then, dinitrogen was the only denitrification product released. In contrast, when the anaerobic periods were short (1.5 h), P. denitrificans was not able to completely synthesize a stable denitrifying enzyme system within the course of the experiment, and a semi-steady state was reached. Nitrite accumulated in the medium as the predominant denitrification product. The transient characteristics of the activated sludge during the repeated aerobic-anaerobic conditions were similar to those observed with P. denitrificans. This finding indicates that information on the induction process of denitrification in P. denitrificans can be used reasonably well to assess induction of denitrifying activity in more complex systems. Finally, the usefulness of the application of mRNA probes are discussed.

PHOSPHORUS RETENTION AND RELEASE CHARACTERISTICS OF SEWAGE-IMPACTED WETLAND SEDIMENTS

Sediment deposited in traps positioned along a sewage-impacted wetland receiving phosphorus (P)-retaining reactants from natural wetland water was fractionated into different particle sizes, and the amount of P retained in these particle sizes was investigated. Subsamples of the sediments collected from different sites along the wetland system were also equilibrated with water at different water:sediment ratios and equilibration periods to investigate the extent of P released from these sediments under aerobic and anaerobic conditions. Results obtained showed that most of P deposited in sediments is in fine fractions (<16 µm), particularly in sediments collected from confluence sites where water inflow from the natural wetland provides P-retaining reactants and from sites immediately below these confluence sites (postconfluence sites). The extent of P release from sediments depended on the aerobic-anaerobic conditions of the sediments, equilibration period, water:sediment ratio and the position of sites within the wetland. The rate of P released from sediments associated with an increase in equilibration period tended to be higher under aerobic than anaerobic conditions. Water:sediment ratio was found to be a more important factor in controlling the release of P from sediments under anaerobic than aerobic conditions. The amount of P released from the confluence and postconfluence sites was higher than that from other sites over a range of equilibration periods and water:sediment ratios under aerobic and anaerobic conditions.

Phosphorus removal in fluidized bed biological reactor (FBBR)

The biological phosphorus removal in fluidized bed biological reactor (FBBR) has been investigated. The feasibility of excess phosphorus uptake, assured by exposition of biomass to anaerobic-aerobic conditions, has been demonstrated on a bench-scale biofilm reactor working as sequencing batch reactor (SBR) and the limiting parameters have been established. Although the reactor worked effectively, it took several weeks for both acclimatization of biomass and selection of a biofilm rich in poly-P-bacteria. The highest phosphate uptake rates have been observed when strict anaerobic conditions were reached during the anaerobic phase. Using a fluidized bed, a thin biofilm, characterized by high surface/volume ratio and hence highly disposed toward substrate uptake, has been obtained and the overall phosphorus abatement, referred to the biomass present in the reactor, proved particularly effective.

Phosphorus release-storage reaction and organic substrate behavior in biological phosphorus removal

This paper represents the results of an experimental investigation conducted on the mechanism of biological phosphorus removal. The relationship between phosphorus release-storage reaction, and behavior of extracellular and intracellular organic substrates under anaerobic-aerobic conditions is studied in detail. The results obtained are as follows: (1) the amount of intracellular carbohydrate increases under the presence of extracellular glucose, but decreases when extracellular glucose is depleted in the anaerobic condition. (2) The amount of intracellular poly-β-hydroxybutylate (PHB) gradually increases under the anaerobic condition. The increase in intracellular PHB content appears to be related to the decrease in intracellular carbohydrate content when extracellular glucose is depleted. (3) Rate of phosphorus release under the anaerobic condition is related to the amount of releasable phosphorus in the cells. The observed ratios of postulated “maximum phosphorus storage capacity” to total amount of intracellular phosphorus are similar to those of the low molecular weight polyphosphate fraction in the cells. (4) Release of phosphorus under the anaerobic condition appears to be related to both ingestion of extracellular organic substrates and formation of intracellular PHB. (5) Release of phosphorus under the anaerobic condition appears to be limited once a fixed portion of intracellular phosphorus is released, even if substantial amount of extracellular organic substrate still remains available. (6) The amount of intracellular PHB increases in the subsequent aerobic condition under presence of a sufficient amount of extracellular organic substrate, but the amount decreases when the extracellular organic substrate is depleted. Similarly, the amount of intracellular carbohydrate initially increases, then gradually decreases following the decrease in PHB content. (7) Ingestion rate for phosphorus in the aerobic condition appears to be dependent on unsaturated storage capacity of intracellular phosphorus as well as on the concentration of extracellular phosphorus.

Growth of a facultative anaerobe under oxygen-limiting conditions in pure culture and in co-culture with a sulfate-reducing bacterium

The occurrence and properties were studied of glucose-metabolizing bacteria present in the anaerobic sediment 5–10 cm below the surface of an estuarine tidal mud-flat. Of all these bacteria (10 4 – 10 5 per g wet sediment) 80–90% were facultatively anaerobic species. Chemostat enrichments on glucose under aerobic, oxygen-limited and alternately aerobic-anaerobic conditions also yielded cultures dominated by facultative anaerobes. One of the dominant species, tentatively identified as a Vibrio sp., was studied in more detail under oxygen-limiting conditions. Fermentative and respiratory metabolisms were found to operate simultaneously, and the ratio between the two was regulated by the extent of oxygen limitation. A small fraction of the acetate formed under such growth conditions was shown to be subsequently respired. A co-culture was established of the Vibrio sp. and a sulfate-reducing bacterium ( Desulfovibrio HL21) in an aerated chemostat. The importance of these observations is discussed in relation to the role of facultative anaerobes in anaerobic habitats.

Growth of a facultative anaerobe under oxygen-limiting conditions in pure culture and in co-culture with a sulfate-reducing bacterium

Abstract The occurrence and properties were studied of glucose-metabolizing bacteria present in the anaerobic sediment 5–10 cm below the surface of an estuarine tidal mud-flat. Of all these bacteria (104 – 105 per g wet sediment) 80–90% were facultatively anaerobic species. Chemostat enrichments on glucose under aerobic, oxygen-limited and alternately aerobic-anaerobic conditions also yielded cultures dominated by facultative anaerobes. One of the dominant species, tentatively identified as a Vibrio sp., was studied in more detail under oxygen-limiting conditions. Fermentative and respiratory metabolisms were found to operate simultaneously, and the ratio between the two was regulated by the extent of oxygen limitation. A small fraction of the acetate formed under such growth conditions was shown to be subsequently respired. A co-culture was established of the Vibrio sp. and a sulfate-reducing bacterium (Desulfovibrio HL21) in an aerated chemostat. The importance of these observations is discussed in relation to the role of facultative anaerobes in anaerobic habitats.

Transitional Steady-State Investigations during Aerobic-Anaerobic Transition of Glucose Utilization by Escherichia coli K-12

Transitional steady-state investigations during changes in oxygen tension under aerobic and during aerobic-anaerobic transition conditions were carried out with the aim of finding an indicator system which separates the equilibrium from the non-equilibrium state. Of the parameters used i.e. biomass formation, CO2 production, Q02, NADH oxidase, succinate dehydrogenase, phosphofructokinase, glyceraldehyde-3 phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and 2-oxoglutarate dehydrogenase, only the three enzymes requiring NADH or NADP for their function fulfilled the requirements. Biomass production and CO2 formation were useful only during the aerobic-anaerobic transition period. In each case the response was immediate and the indicator systems demonstrated that a new steady state of oxygen was always obtained after 11 h which, at the specific growth rate used, was equivalent to at least two volume replacements of the growth vessel.