Synthesis of thermo-sensitive copolymer with affinity butyl ligand and its application in lipase purification

In this study, thermo-sensitive N-alkyl substituted polyacrylamide polymer P_NNB was synthesized by using N-hydroxymethyl acrylamide(NHAM), N-isopropyl acrylamide (NIPA) and butyl acrylate (BA) as monomers, and its low critical solution temperature (LCST) was controlled to be 28 °C. The recovery of the thermo-sensitive polymer was over 98%. Butanol as a hydrophobic ligand was covalently attached onto polymer P_NNB and butyl ligand density was 80 μmol g^?1 polymer. The affinity polymer was used for purification of lipase from crude material. Optimized condition was pH 7.0, 35 °C adsorption temperature, 120 min adsorption time and 0.5 mg ml^?1 initial concentration of lipase. The adsorption isotherm accords with a typical Langmuir isotherm. The maximum adsorption capacity (Q_m) of the affinity polymer for lipase was 24.8 mg g^?1polymer. The affinity copolymer could be recycled by temperature-inducing precipitation and there was only about 6% loss of adsorption capacity after five recyclings. Specific activity of lipase was improved from 14 IU mg^?1 to 506 IU mg^?1 protein, and its recovery achieved 82%. The affinity polymer is suitable for the purification of target proteins from the crude material with large volume and dilute solution.     

Continuous Cr(VI) removal by Scenedesmus incrassatulus in an airlift photobioreactor

Cr(VI) removal by Scenedesmus incrassatulus was characterized in a continuous culture system using a split-cylinder internal-loop airlift photobioreactor fed continuously with a synthetic effluent containing 1.0 mg Cr(VI) l^?1 at dilution rate (D) of 0.3 d^?1. At steady state, there was a small increase (6%) on the dry biomass (DB) concentration of Cr(VI)-treated cultures compared with the control culture. 1.0 mg Cr(VI) l^?1 reduced the photosynthetic pigments content and altered the cellular morphology, the gain in dry weight was not affected. At steady state, Cr(VI) removal efficiency was 43.5 ± 1.0% and Cr(VI) uptake was 1.7 ± 0.1 mg Cr(VI) g^?1 DB. The system reached a specific metal removal rate of 458 μg Cr(VI) g^?1 DB d^?1, and a volumetric removal rate of 132 μg Cr(VI) l^?1 d^?1.     

Separation of lactobacilli bacteriocins from fermented broths using membranes

Current separation, isolation and purification techniques to obtain highly potent purified lactobacilli and lactococci bacteriocins include chemical precipitation, separation employing solvents and chromatographic techniques. These methods are arduous, costly, with limited scalability, offering low bacteriocin yields (<20%). To address these challenges, the alternatives of ultrafiltration and nanofiltration, as separation methods were tested. Three promising bacteriocin producing strains, Lactobacillus casei NCIMB 11970, Lactobacillus plantarum NCIMB 8014 and Lactococcus lactis NCIMB 8586 were selected to investigate the applicability and feasibility of the method.To facilitate separation, the microorganisms were grown on specially developed low molecular weight medium (LMWM) mainly containing nutritive sources up to 4 kDa molecular weight. Bacterial cells were removed by centrifugation. The clarified broths were filtered using 4 and 1 kDa MWCO. Bacteriocin activity was determined by an antimicrobial activity test using nisin, which has an inhibitory effect on the growth of susceptible microorganisms. Recovery yields using filtration were found to range between 53 and 68%, a high recovery performance.The bacteriocin activity of crude extracts of all the three lactobacilli were between 95 and 105 IU ml^?1. When the substances were separated using ultrafiltration membrane (4 kDa MWCO) their activity was enhanced to 145–150 IU ml^?1, achieving a total potency yield of 44–53%. Further enhancement of yields up to 36% was attained employing nanofiltration (1 kDa MWCO) membranes with an activity increased up to 200 IU ml^?1.Bacteriocin isolation from crude extracts using filtration was found to be effective, offering high recovery yields, optimising their activity as well as presenting a realistic option towards the formulation of these as commercially available antibacterial agents.     

Nitrate removal and greenhouse gas production in a stream-bed denitrifying bioreactor

Denitrifying bioreactors are currently being tested as an option for treating nitrate (NO₃^?) contamination in groundwater and surface waters. However, a possible side effect of this technology is the production of greenhouse gases (GHG) including nitrous oxide (N₂O) and methane (CH₄). This study examines NO₃^? removal and GHG production in a stream-bed denitrifying bioreactor currently operating in Southern Ontario, Canada. The reactor contains organic carbon material (pine woodchips) intended to promote denitrification. Over a 1 year period, monthly averaged removal of influent (stream water) NO₃^? ranged from 18 to 100% (0.3–2.5 mg N L^?1). Concomitantly, reactor dissolved N₂O and CH₄ production, averaged 6.4 μg N L^?1 (2.4 mg N m^?2 d^?1), and 974 μg C L^?1 (297 mg C m^?2 d^?1) respectively, where production is calculated as the difference between inflow and effluent concentrations. Gas bubbles entrapped in sediments overlying the reactor had a composition ranging from 19 to 64% CH₄, 1 to 6% CO₂, and 0.5 to 2 ppmv N₂O; however, gas bubble emission rates were not quantified in this study. Dissolved N₂O production rates from the bioreactor were similar to emission rates reported for some agricultural croplands (e.g. 0.1–15 mg N m^?2 d^?1) and remained less than the highest rates observed in some N-polluted streams and rivers (e.g. 110 mg N m^?2 d^?1, Grand R., ON). Dissolved N₂O production represented only a small fraction (0.6%) of the observed NO₃^? removal over the monitoring period. Dissolved CH₄ production during summer months (up to 1236 mg C m^?2 d^?1), was higher than reported for some rivers and reservoirs (e.g. 6–66 mg C m^?2 d^?1) but remained lower than rates reported for some wastewater treatment facilities (e.g. sewage treatment plants and constructed wetlands, 19,500–38,000 mg C m^?2 d^?1).     

Nitrate removal rates in woodchip media of varying age

A variety of low-cost carbonaceous solids have been successfully tested in bioreactors designed for nitrate treatment. In many agricultural and wastewater settings, however, such reactors may be practical only if they are maintenance free for a number of years after installation. Although field installations have demonstrated consistent treatment over multi-year timeframes, the ability to accurately quantify slowly declining reaction rates in field settings is problematic because of variations in reactor flow rates, ambient temperatures and influent chemistry. In this study, laboratory column tests were undertaken on four samples of coarse wood particle media (woodchips), two that were fresh and two that had been in continuous operation in subsurface denitrifying bioreactors for periods of 2 and 7 years respectively. Four experimental runs were undertaken at increasing influent NO₃-N concentrations of from 3.1 to 48.8 mg N L^?1. Nitrate mass removal rates remained relatively constant and did not systematically increase in successive runs at higher NO₃ concentrations indicating that NO₃ was not the rate-limiting substrate at these concentrations. Thus, zero-order reaction kinetics were used to model the attenuation reaction (presumably denitrification). The 7-year-old media had a mean NO₃-N removal rate of 9.1 mg N L^?1 d^?1 (6.4 g N m^?3 media d^?1), which remained within 75% of the rate for the 2-year-old media (12.1 mg N L^?1 d^?1 or 8.5 g N m^?3 media d^?11) and within 40–59% of the rate for the fresh chips (15.4–23.0 mg N L^?1 d^?1 or 10.8–16.1 g N m^?3 media d^?1). Results support field experience indicating that woodchips loose about 50% of their reactivity during their first year of operation as soluble organic compounds are leached out, but then relatively stable rates persist for a considerable number of years thereafter.     

Inhibitory effects of taurine and oat fiber on intestinal endotoxin release in rats

Numerous studies have demonstrated that endotoxin plays an important role in the development and progression of hepatic cirrhosis. However, there is no effective remedy for the prevention and treatment of intestinal endotoxemia. Taurine has been reported to have beneficial effects on endotoxemia. Oats have been shown to absorb intestinal toxins and increase excretion of intestinal toxins. The present study was to investigate whether a combination of taurine and oat has an additive inhibitory effect on endotoxin release in a rat liver ischemia/reperfusion model. Our results showed that the combination of taurine (300 mg kg^?1 d^?1) and oat fiber (15 g kg^?1 d^?1) significantly reduced endotoxin levels in the portal vein by 36.3% when compared to the control group (0.168 ± 0.035 Eu/ml in the treatment group vs 0.264 ± 0.058 Eu/ml in the control group, P < 0.01). The treatment of taurine (300 mg kg^?1 d^?1) and oat fiber (15 g kg^?1 d^?1) induced 21.5% and 18.4% reduction in endotoxin levels, respectively, when compared to the control group (P < 0.05). We conclude that the combination of taurine and oat fiber achieved an additive inhibitory effect on intestinal endotoxin release, which might be an effective approach for the treatment of intestinal endotoxemia.     

Solids hydrolysis and accumulation in a hybrid anaerobic digester-constructed wetlands system

The properties and behaviour of solids retained in a pilot plant constituted of an up-flow anaerobic sludge blanket (UASB) reactor and two constructed wetlands (CWs) were monitored over a 3-year period. The UASB (25.5 m³) was fed with raw municipal wastewater at a flow rate of 61–112 m³ d^?1 and a volumetric loading rate (VLR) of 0.75–1.70 kg TCOD m^?3 d^?1. The CWs (75 m² each) were operated in series and received a fraction (17–20 m³ d^?1) of the UASB effluent. The applied surface loading rates (SLR) were in the range of 3800–8700 g TCOD m^?2 d^?1 (UASB) and 11–15 g BOD₅ m^?2 d^?1 (CWs). The overall system removed 95% TSS, 85% TCOD and 87% BOD₅ on average. For influent VSS, the UASB removed 72.1% and gave a hydrolysis of 63.5%, while the average surplus sludge generation was 8.7%. Over the 3-year period, TSS and VSS accumulated in the CWs at rates of 1.07 and 0.56 kg m^?2 year^?1, respectively. The aerobic biodegradability of the accumulated solids ranged from 23 to 92 mg O₂ g VSS^?1 d^?1 and increased downstream in the CWs. About 59% of the VSS that entered the CWs was removed by hydrolysis, while 24% accumulated on granular media. These low solids accumulation rates were especially remarkable considering the high COD and BOD₅ loading rates applied. The system lay-out appear to be promising in terms of preventing clogging.     

Relationship between microbial activity and microbial community structure in six full-scale anaerobic digesters

High activity levels and balanced anaerobic microbial communities are necessary to attain proper anaerobic digestion performance. Therefore, this work was focused on the kinetic performance and the microbial community structure of six full-scale anaerobic digesters and one lab-scale co-digester. Hydrolytic (0.6–3.5 g COD g^?1 VSS d^?1) and methanogenic (0.01–0.84 g COD g^?1 VSS d^?1) activities depended on the type of biomass, whereas no significant differences were observed among the acidogenic activities (1.5–2.2 g COD g^?1 VSS d^?1). In most cases, the higher the hydrolytic and the methanogenic activity, the higher the Bacteroidetes and Archaea percentages, respectively, in the biomasses. Hydrogenotrophic methanogenic activity was always higher than acetoclastic methanogenic activity, and the highest values were achieved in those biomasses with lower percentages of Methanosaeta. In sum, the combination of molecular tools with activity tests seems to be essential for a better characterization of anaerobic biomasses.     

Nitrate removal and hydraulic performance of organic carbon for use in denitrification beds

Denitrification beds are a cost-effective technology for removing nitrate from point source discharge. To date, field trials and operational beds have primarily used wood media as the carbon source; however, the use of alternative more labile carbon media could provide for increased removal rate, lower installation costs and reduced bed size. While previous laboratory experiments have investigated the potential of alternative carbon sources, these studies were typically of short duration and small scale and did not necessarily provide reliable information for denitrification bed design purposes. To address this issue, we compared nitrate removal, hydraulic and nutrient leaching characteristics of nine different carbon substrates in 0.2 m³ barrels, at 14 and 23.5 °C over a 23-month period. Mean nitrate removal rates for the period 10–23 months were 19.8 and 15 g N m^?3 d^?1 (maize cobs), 7.8 and 10.5 g N m^?3 d^?1 (green waste), 5.8 and 7.8 g N m^?3 d^?1 (wheat straw), 3.0 and 4.9 g N m^?3 d^?1 (softwood), and 3.3 and 4.4 g N m^?3 d^?1 (hardwood) for the 14 and 23.5 °C treatments, respectively. Maize cobs provided a 3–6.5-fold increase in nitrate removal over wood media, without prohibitive decrease in hydraulic conductivity, but had higher rates of nutrient leaching at start-up. Significant difference in removal rate occurred between the 14 and 23.5 °C treatments, with the mean Q₁₀ temperature coefficient = 1.6 for all media types in the period 10–23 months.     

High-rate denitrifying sulfide removal process in expanded granular sludge bed reactor

An expanded granular sludge bed (EGSB) reactor was adopted to incubate bio-granules that could simultaneously convert 4.8 kg-S m^?3 d^?1 of sulfide in 97% efficiency; 2.6 kg-N m^?3 d^?1 of nitrate in 92% efficiency; and 2.7 kg-C m^?3 d^?1 acetate in 95% efficiency. Mass balance calculation of sulfur, nitrogen, and carbon over the EGSB reactor confirmed the performance results. This noted reactor performance is much higher than those reported in literature. Stoichiometric relation suggests that the nitrate was reduced to nitrite via autotrophic denitrification pathway, then the formed nitrite was converted via heterotrophic denitrification pathway to N₂.     

Seasonally constant field metabolic rates in free-ranging sugar gliders (Petaurus breviceps)

Sugar gliders, Petaurus breviceps (average body mass: 120 g) like other small wild mammals must cope with seasonal changes in food availability and weather and therefore thermoregulatory and energetic challenges. To determine whether free-ranging sugar gliders, an arboreal marsupial, seasonally adjust their energy expenditure and water use, we quantified field metabolic rates (FMR) and water flux at a seasonal cool-temperate site in eastern Australia. Thirty six male and female sugar gliders were labelled with doubly labelled water for this purpose in spring, summer and autumn. The mean FMR was 159 ± 6 kJ d^? 1 (spring), 155 ± 8 kJ d^? 1 (summer), and 152 ± 20 kJ d^? 1 (autumn) and the mean FMR for the three seasons combined was 158 ± 5 kJ d^? 1 (equivalent to 1.33 kJ g^? 1 d^? 1 or 780 kJ kg^? 0.75 d^? 1). The mean total body water was 83 ± 2 g, equal to 68.5% of body weight. Mean water flux was 29 ± 1 mL day^? 1. Season, ambient temperature or sex did not affect any of the measured and estimated physiological variables, but body mass and total body water differed significantly between sexes and among seasons. Our study is the first to provide evidence for a constant FMR in a small mammal in three different seasons and despite different thermal conditions. This suggests that seasonal changes in climate are compensated for by behavioural and physiological adjustments such as huddling and torpor known to be employed extensively by sugar gliders in the wild.     

Refolding and purification of recombinant human granulocyte colony-stimulating factor using hydrophobic interaction chromatography at a large scale

High level expression of recombinant human granulocyte colony-stimulating factor (rhG-CSF) in Escherichia coli (E. coli) usually forms insoluble and inactive aggregates, i.e. inclusion bodies. In the present work, high performance hydrophobic interaction chromatography (HPHIC) was applied to the refolding of rhG-CSF, which was solubilized by 8.0 mol L^?1 urea from the inclusion bodies. First a laboratorial scale column (10 mm × 20 mm I.D.) was employed to study the refolding process. Several factors, including concentration of ammonium sulfate, pH of the mobile phase and flow rate, were investigated in details. The results indicated that the rhG-CSF produced by E. coli could be successfully refolded with simultaneous purification by using HPHIC. The refolding process was further scaled up by using a large column (50 mm × 200 mm I.D.). 200 mL of rhG-CSF solution solubilized by 8.0 mol L^?1 urea, with a total amount of protein around 1.6 g, could be loaded onto the large column at one time. Under these conditions, the obtained rhG-CSF had a specific activity of 2.3 × 10⁸ IU mg^?1 and a purity of 95.4%, the mass recovery during the purification was 36.9%. This work might have great impact on practical production of rhG-CSF, and it also shed a light on protein refolding using liquid chromatography at large scales.     

Nitrification rates of algal–bacterial biofilms in wastewater stabilization ponds under light and dark conditions

The objective of this study was to investigate nitrification rates in algal–bacterial biofilms of waste stabilization ponds (WSP) under different conditions of light, oxygen and pH. Biofilms were grown on wooden plates of 6.0 cm by 8.0 cm by 0.4 cm in a PVC tray continuously fed with synthetic wastewater with initial NH₄-N and Chemical Oxygen Demand (COD) concentrations of 40 mg l^?1 and 100 mg l^?1, respectively, under light intensity of 85–95 μE m^?2 s^?1. Batch activity tests were carried out by exposure of the plates to light conditions as above (to simulate day time), dim light of 1.8–2.2 μE m^?2 s^?1 (to simulate reduced light as in deeper locations in WSP) and dark conditions (to simulate night time). Dissolved oxygen (DO) concentration and pH were controlled. At some experiments, both parameters were kept constant, and at others they were left to vary as in WSP. Results show biofilm nitrification rates of 945–1817 mg-N m^?2 d^?1 and 1124–1615 mg-N m^?2 d^?1 for light and dark experiments. When the minimum DO was 4.1 mg l^?1, the biofilm nitrification rates under light and dark conditions did not differ significantly at 95% confidence. When the minimum DO in the dim light experiment was 3.2 mg l^?1, the nitrification rates under light and dim light conditions were 945 mg-N m^?2 d^?1 and 563 mg-N m^?2 d^?1 and these significantly differed. Further decrease of DO to 1.1 mg l^?1 under dark conditions resulted in more decrease of the nitrification rates to 156 mg-N m^?2 d^?1. It therefore seems that under these experimental conditions, biofilm nitrification rates are significantly reduced at a certain point when bulk water DO is between 3.2 mg l^?1 and 4.1 mg l^?1. As long as bulk water DO under dark is high, light is not important in influencing the process of nitrification.     

Treatment of high-strength wastewater in tropical vertical flow constructed wetlands planted with Typha angustifolia and Cyperus involucratus

The ability of vertical flow (VF) constructed wetland systems to treat high-strength (ca. 300 mg L^?1 of COD and ca. 300 mg L^?1 total-nitrogen) wastewater under tropical climatic conditions was studied during a 5-month period. Nine 0.8-m diameter experimental VF units (depth 0.6 m) were used: three units were planted with Typha angustifolia L., another three units were planted with Cyperus involucratus Rottb and three units were unplanted. Each set of units were operated at hydraulic loading rates (HLRs) of 20, 50 and 80 mm d^?1. Cyperus produced more shoots and biomass than the Typha, which was probably stressed because of lack of water. The high evapotranspirative water loss from the Cyperus systems resulted in higher effluent concentrations of COD and total-P, but the mass removal of COD did not differ significantly between planted and unplanted systems. Average mass removal rates of COD, TKN and total-P at a HLR of 80 mm d^?1 were 17.8, 15.4 and 0.69 g m^?2 d^?1. The first-order removal rate constants at a HLR of 80 mm d^?1 for COD, TKN and total-P were 49.8, 30.1 and 13.5 m year^?1, respectively, which is in the higher range of k-values reported in the literature. The oxygen transfer rates were ca. 80 g m^?2 d^?1 in the planted systems as opposed to ca. 60 g m^?2 d^?1 in the unplanted systems. The number of Nitrosomonas was two to three orders of magnitude higher in the planted systems compared to the unplanted systems. Planted systems thus had significantly higher removal rates of nitrogen and phosphorus, higher oxygen transfer rates, and higher quantities of ammonia-oxidizing bacteria. None of the systems did, however, fully nitrify the wastewater, even at low loading rates. The vertical filters did not provide sufficient contact time between the wastewater and the biofilm on the gravel medium of the filters probably because of the shallow bed depth (0.6 m) and the coarse texture of the gravel. It is concluded that vertical flow constructed wetland systems have a high capacity to treat high-strength wastewater in tropical climates. The gravel and sand matrix of the vertical filter must, however, be designed in a way so that the pulse-loaded wastewater can pass through the filter medium at a speed that will allow the water to drain before the next dose arrives whilst at the same time holding the water back long enough to allow sufficient contact with the biofilm on the filter medium.     

The relationship between the volatile fatty acids supply and the nitrogen retention in growing sheep nourished by total intragastric infusions

Twelve four-month old Suffolk × Small-tail-Han male sheep (live weight 21–26 kg), fitted with rumen and abomasum fistulas and nourished by total intragastric infusions, were used to study the relationship between the volatile fatty acids (VFA) supply and the nitrogen (N) retention in sheep. The animals were randomly divided into four groups and four levels of mixed VFA energy (the molar proportion of acetic acid, propionic acid and butyric acid was 65:25:10), i.e. 333, 378, 423 and 468 kJ kg^?1 W^0.75 d^?1, were infused into the rumen, as treatments I, II, III and IV, respectively. The results showed that the N retention was significantly increased (P < 0.05) with the VFA infusion level. Significant regression relationship was found between the VFA supply (x, g d^?1) and the N retention (y, mg d^?1): y = 2.75x ? 403, r² = 0.86, n = 12, P < 0.01. It was concluded that to get efficient utilization of dietary N and high N retention in sheep, it is necessary to supply enough dietary energy.     

Effect of hydraulic retention time on the treatment of secondary effluent in a subsurface flow constructed wetland

This study evaluates the potential of subsurface flow (SSF) constructed wetlands (CWs) for tertiary treatment of wastewater at four shorter HRTs (1–4 days). The CWs were planted with Typha angustata, which was observed in our earlier study to be more efficient than Phragmites karka and Scirpus littoralis. The CWs comprised four rectangular treatment cells (2.14 m × 0.76 m × 0.61 m) filled with layers of gravel of two different sizes (approximately 2.5 cm and 1.5 cm diameter) to a depth of 0.61 m. The inflow rates of the secondary effluent in the four cells were accordingly fixed at 300 L d^?1, 150 L d^?1, 100 L d^?1 and 75 L d^?1, respectively, for 1, 2, 3 and 4 days HRT. The hydraulic loads ranged between 59.05 mm d^?1 and 236.22 mm d^?1.The wastewater inflow into the CW system as well as the treated effluent were analyzed, using standard methods, at regular intervals for various forms of nitrogen (NH₄-N, NO₃-N and TKN), orthophosphate-P and organic matter (BOD and COD) concentrations over a period of five weeks after the development of a dense stand.The higher HRT of 4 days not only helped maximum removal of all the pollutants but also maintained the stability of the treatment efficiency throughout the monitoring period. For the nutrients (NH₄-N, NO₃-N and TKN), HRT played a more significant role in their removal than in case of organic matter (BOD₃ and COD). More than 90% of NO₃-N and TKN and 100% of NH₄-N were removed from the wastewater at 4 days HRT.At lower HRTs, the mass loading rate was higher with greater fluctuation. However mass reduction efficiency of the T. angustata CW for all forms of nitrogen was >80% with the HRTs of 2, 3 and 4 days.     

Biodegradation of Tapis blended crude oil in marine sediment by a consortium of symbiotic bacteria

Biodegradation rate and the high molecular weight hydrocarbons are among the important concerns for bioremediation of crude oil. Inoculation of a non-oil-degrading bacterium as supplementary bacteria increased oil biodegradation from 57.1% to 63.0% after 10 days of incubation. Both the oil-degrading bacteria and the non-oil-degrading bacteria were isolated from Malaysian marine environment. Based on the 16S rDNA sequences, the oil-degrading bacteria was identified as Pseudomonas pseudoalcaligenes (99% similarity) while the non-oil-degrading bacterium was Erythrobacter citreus (99% similarity). E. citreus does not grow on crude oil enriched medium under present experimental condition but it withstands 5000 mg kg^?1 Tapis blended crude oil in sediment. Under optimal condition, the oil-degrading bacterium; P. pseudoalcaligenes, alone utilized 583.3 ± 3.8 mg kg^?1 (57.1%) at the rate of 3.97 × 10^?10 mg kg^?1 cell^?1 day^?1 Tapis blended crude oil from 1000 mg kg^?1 oil-contaminated sediment. Inoculation of E. citreus as the supplementary bacteria to P. pseudoalcaligenes enhanced biodegradation. The bacterial consortium degraded 675.8 ± 18.5 mg kg^?1 (63.0%) Tapis blended crude oil from the 1000 mg kg^?1 oil-contaminated sediment. Biodegradation rate of the bacterial consortium increased significantly to 4.59 × 10^?10 mg kg^?1 cell^?1 day^?1 (p = 0.02). Improvement of the oil degradation by the bacterial consortium was due to the synergetic reaction among the bacterial inoculants. There are two implications: (1) E. citreus may have a role in removing self-growth-inhibiting compounds of P. pseudoalcaligens. (2) P. pseudoalcaligenes degraded Tapis blended crude oil while E. citreus competes for the partially degraded hydrocarbons by P. pseudoalcaligenes. P. pseudoalcaligenes forced to breakdown more hydrocarbons to sustain its metabolic requirement. The bacterial consortium degraded 78.7% of (C₁₂–C₃₄) total aliphatic hydrocarbons (TAHs) and 74.1% of the 16 USEPA prioritized polycyclic aromatic hydrocarbons.     

A comparative study of surface and subsurface flow constructed wetlands for treatment of combined sewer overflows: A greenhouse experiment

The use of surface flow (SFCWs) and subsurface flow constructed wetlands (SFCWs) for the treatment of combined sewer overflows was assessed at pilot scale. Synthetic wastewater was applied in three batches with decreasing concentrations to mimic concentration profiles that are obtained in the field during overflow events. Three simulated combined sewer overflows were applied on each wetland. Composite water samples (60 in total) were taken for a period of 8 days to study the removal of total nitrogen (Ntot), NH₄–N, NO₃–N, total COD (CODtot) and total phosphorus. Redox potential, which was monitored at various locations along the wetlands, was more negative in the SSFCWs. In general, removal occurred faster in the SSFCWs and the final concentrations were lower. The removal of Ntot was only 36.6 ± 3.3% in the SFCWs due to nitrification-limiting conditions. The conditions in the SSFCWs, in contrast, seemed to promote Ntot removal (removal efficiency 96.7 ± 1.9%). The removal of P was hampered in both wetland types by reducing conditions. P that was initially removed was released again from the substrates later on. First-order removal rate constants were derived for the removal of both CODtot (SSFCWs: 1.1 ± 0.3 m d^?1; SFCWs: 0.17 ± 0.06 m d^?1) and Ntot (SSFCWs: 0.4 ± 0.1 m d^?1; SFCWs: 1.7 ± 0.5 m d^?1).     

The influence of light quality on akinete formation and germination in the toxic cyanobacterium Anabaena circinalis

Physiological control of akinete formation and subsequent germination is likely to be important in understanding and predicting how natural populations of cyanobacteria respond to their environment. While previous research has indicated nutrient limitation may be important in akinete formation new results presented here indicate that in the toxic and bloom-forming species Anabaena circinalis there was a profound effect of spectral quality. Under 40 μmol photons m^?2 s^?1 photosynthetically active irradiance (PAR) of predominately red irradiance akinete production was maximal at 2.1 × 10^?4 akinetes vegetative cell^?1 d^?1, some 3000 times greater than the 6.5 × 10^?8 akinetes vegetative cell^?1 d^?1 observed under equivalent PAR but predominately blue light. For cells grown under a range of predominantly red, white and green irradiance even short exposures to blue light reduced akinete formation rates by a factor of ten relative to controls, indicating that exposure to blue light inhibits akinete formation. Germination of akinetes was not influenced by the irradiance under which akinetes were formed: 88 ± 4.1% (mean ± 1 S.D.) of akinetes germinated with no evidence of an effect on germination success due to their production under predominately red, white or green irradiance (germination of akinetes produced under blue light was not tested). Spectral quality had a significant impact on both vegetative cell and germling growth rates. The results indicate a significant reduction in the cellular differentiation of A. circinalis vegetative cells into akinetes that is mediated by blue light. In an ecological context the production of akinetes will be greater in environments with less blue light; potentially including those with slower flow, more stratification, less vertical mixing and more turbidity. The resulting spatial pattern of akinete production is likely to influence the location of akinetes in sediments and the development of subsequent blooms from excysting germlings.     

A key cultivation technology for denitrifying granular sludge

Well-formed denitrifying granular sludge with a biomass concentration of 24.8 gVSS L^?1 and a specific nitrate removal rate of 0.19 gNO₃-N gVSS^?1 d^?1 was obtained in an upflow sludge blanket (USB) reactor by cultivating seeded aerobic flocculent sludge for 6–8 weeks. Regularity phenomena exist in the granulation including flotation of flocculent sludge, formation of fine granules, occurrence of channelling, and formation of mature granular sludge. The granulation is similar to crystal growth, that the non-denitrifying bacteria evolve into the carriers (fine granules), on the surface of which denitrifying bacteria proliferate and develop into mature granular sludge.There are several key parameters that must be considered when developing a good denitrifying granular sludge. First, the proper seed sludge must be chosen (VSS/SS at 0.65–0.75, SRT over 25 days) to accelerate the granulation process. Secondly, any floating sludge should be stirred, and the sludge loading rate should be within the range of 0.05–0.15 gNO₃-N gVSS^?1 d^?1 until fine granules emerge. Additionally, spontaneous gas agitation or interval air-blowing should be used to effectively eliminate channelling; Finally, the sludge loading rate should be less than 0.25 gNO₃-N gVSS^?1 d^?1 until dense, mature granular sludge appears. This study could support and promote the full-scale application of denitrifying granular sludge.