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1.
This paper attempts to provide insight into the biological ammonium oxidation process applied to high-strength ammonium wastewater treatment. The ammonium oxidation process has been investigated at various ammonium and biomass concentrations. Using the oxygen uptake rate (OUR) method, a proportion of both active ammonium oxidizers (AAO) and nitrite oxidizers to the total suspended solids were separately estimated, and then tested to normalize the ammonium oxidation rate at various ammonium strengths and AAO concentrations. High-ammonium strength showed no significant inhibition to ammonium oxidation due to high-AAO concentration. It was demonstrated that the key factor deciding the specific ammonium oxidation rate was the ratio of ammonium concentration to the active nitrifiers (AN) concentration, but not the sole-variable such as initial ammonium concentration and AN concentration. Contois model was screened to suitably fit the ammonium oxidation kinetics under the high-ammonium loading condition, resulting in a half-saturation constant of 0.028 mg N mg ?1 AAO and a maximum specific ammonium oxidation rate of 3.56 g N g ?1 AAO d ?1. 相似文献
2.
Mass culture of microalgae is a potential alternative to cultivation of terrestrial crops for bioenergy production. However, microalgae require nitrogen fertiliser in quantities much higher than plants, and this has important consequences for the energy balance of these systems. The effect of nitrogen fertiliser supplied to microalgal bubble-column photobioreactor cultures was investigated using different nitrogen sources (nitrate, urea, ammonium) and culture conditions (air, 12% CO 2). In 20 L cultivations, maximum biomass productivity for Chlorella vulgaris cultivated using nitrate and urea was 0.046 and 0.053 g L −1 day −1, respectively. Maximum biomass productivity for Dunaliella tertiolecta cultivated using nitrate, urea and ammonium was 0.033, 0.038 and 0.038 g L −1 day −1, respectively. In intensive bubble-column photobioreactors using 12% CO 2, maximum productivity reached 0.60 and 0.83 g L −1 day −1 for C. vulgaris and D. tertiolecta, respectively. Recycling of nitrogen within the photobioreactor system via algal exudation of nitrogenous compounds and bacterial activity was identified as a potentially important process. The energetic penalty incurred by supply of artificial nitrogen fertilisers, phosphorus, power and CO 2 to microalgal photobioreactors was investigated, although analysis of all energy burdens from biomass production to usable energy carriers was not conducted. After subtraction of the power, nitrogen and phosphorus energy burdens, maximum net energy ratios for C. vulgaris and D. tertiolecta cultivated in bubble columns were 1.82 and 2.10. Assuming CO 2 was also required from a manufactured source, the net energy ratio decreased to 0.09 and 0.11 for C. vulgaris and D. tertiolecta, so that biomass production in this scenario was unsustainable. Although supply of nitrogen is unlikely to be the most energetically costly factor in sparged photobioreactor designs, it is still a very significant penalty. There is a need to optimise both cultivation strategies and recycling of nitrogen in order to improve performance. Data are supported by measurements including biochemical properties (lipid, protein, heating value) and bacterial number by epifluorescence microscopy. 相似文献
3.
Changes of microbial characteristics in a full-scale submerged membrane bioreactor system (capacity, 60,000 m 3 day −1) treating sewage were monitored over the start-up period (96 days). Fluorescence in situ hybridization analysis showed that
the percentages of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (nitrobacter-related population) in total
bacteria counted with DAPI staining increased significantly from 1.9% and 0.9% to 4.5% and 2.8%, corresponding to an increase
of the specific ammonium oxidizing rate (from 0.06 to 0.12 kg N kg −1 mixed liquor suspended solids (MLSS) per day) and the specific nitrate forming rate (from 0.05 to 0.10 kg N kg −1 MLSS day −1). Both the denaturing gradient gel electrophoresis of polymerase chain reaction and clone library results showed that the
AOB was dominated by the genus Nitrosomonas, the diversity of which increased markedly with operational time. Most of the day 2 clones were closely related with the
uncultured Nitrosomonas sp. clone Ninesprings-49S amoA gene (AY356450.1) originated from activated sludge, while the day 96 clone library showed a more diverse distribution characterized
by the appearance of the oligotrophic nitrifiers like the Nitrosomonas oligotropha- and Nitrosomonas ureae-like bacteria, perhaps due to the interception by membrane and the low food-to-microorganisms ratio environment. The above
results show that the membrane bioreactor system was characterized by the increased diversity and percentage of nitrifiers,
which made it possible to achieve a stable and high efficient nitrification. Ammonia-oxidizing archaea with the changing population
structures were also detected, but their roles for ammonia oxidation in the system need further studies. 相似文献
4.
Controlled cultivation of marine macroalgal biomass such as Ulva species, notably Ulva lactuca, is currently studied for production of biofuels or functional food ingredients. In a eutrophic environment, this macrophyte
is exposed to varying types of nutrient supply, including different and fluctuating levels of nitrogen sources. Our understanding
of the influences of this varying condition on the uptake and growth responses of U. lactuca is limited. In this present work, we examined the growth response of U. lactuca exposed to different sources of nitrogen (NH 4+; NO 3−; and the combination NH 4NO 3) by using photo-scanning technology for monitoring the growth kinetics of U. lactuca. The images revealed differential increases of the surface area of U. lactuca disks with time in response to different N-nutrient enrichments. The results showed a favorable growth response to ammonium
as the nitrogen source. The NH 4Cl and NaNO 3 rich media (50 μM of N) accelerated U. lactuca growth to a maximum specific growth rate of 16.4 ± 0.18% day −1 and 9.4 ± 0.72% day −1, respectively. The highest biomass production rate obtained was 22.5 ± 0.24 mg DW m −2·day −1. The presence of ammonium apparently discriminated the nitrate uptake by U. lactuca when exposed to NH 4NO 3. Apart from showing the significant differential growth response of U. lactuca to different nitrogen sources, the work exhibits the applicability of a photo-scanning approach for acquiring precise quantitative
growth data for U. lactuca as exemplified by assessment of the growth response to two different N-sources. 相似文献
5.
Abies faxoniana is a key species in reforestation processes in the southeast of the Qinghai-Tibetan Plateau of China. The changes in growth,
photosynthesis and nutrient status of A. faxoniana seedlings exposed to enhanced ultraviolet-B (UV-B), nitrogen supply and their combination were investigated. The experimental
design included two levels of UV-B treatments (ambient UV-B, 11.02 KJ m −2 day −1; enhanced UV-B, 14.33 KJ m −2 day −1) and two nitrogen levels (0; 20 g N m −2). The results indicated that: (1) enhanced UV-B significantly caused a marked decline in growth parameters, net photosynthetic
rate (Pn), photosynthetic pigments and F
v/ F
m, (2) supplemental nitrogen supply increased the accumulation of total biomass, Pn, photosynthetic pigments and F
v/ F
m under ambient UV-B, whereas supplemental nitrogen supply reduced Pn, and not affect biomass under enhanced UV-B, (3) enhanced
UV-B or nitrogen supply changed the concentration of nutrient elements of various organs. 相似文献
6.
The growth, biofiltering efficiency and uptake rates of Ulva clathrata were studied in a series of outdoor tanks, receiving waste water directly from a shrimp ( Litopenaeus vannamei) aquaculture pond, under constant aeration and two different water regimes: (1) continuous flow, with 1 volume exchange a
day (VE day -1) and (2) static regime, with 1 VE after 4 days. Water temperature, salinity, pH, dissolved inorganic nitrogen (DIN), phosphate
(PO 4), chlorophyll- a (chl- a), total suspended solids (TSS), macroalgal biomass (fresh weight) and tissue nutrient assimilation were monitored over 12 days.
Ulva clathrata was highly efficient in removing the main inorganic nutrients from effluent water, stripping 70–82% of the total ammonium
nitrogen (TAN) and 50% PO 4 within 15 h. Reductions in control tanks were much lower (Tukey HSD, P < 0.05). After 3 days, the mean uptake rates by the seaweed biomass under continuous flow were 3.09 mg DIN g DW day −1 (383 mg DIN m −2 day −1) and 0.13 mg PO 4 g DW day −1 (99 mg PO 4 m −2 day −1), being significantly higher than in the static regime (Tukey HSD, P < 0.05). The chl- a decreased in seaweed tanks, suggesting that U. clathrata inhibited phytoplankton growth. Correlations between the cumulative values of DIN removed from the water and total nitrogen
assimilated into the seaweed biomass ( r = 0.7 and 0.8, P < 0.05), suggest that nutrient removal by U. clathrata dominated over other processes such as phytoplankton and bacterial assimilation, ammonia volatilization and nutrient precipitation. 相似文献
7.
The present study investigated the effect of nitrogen source (NH 4+; NO 3−) at different concentrations on the accumulation of biomass and secondary metabolites in adventitious root cultures of Hypericum perforatum L. Cultures were initiated in shake flasks by using half-strength Murashige and Skoog (MS) medium with B5 vitamins, 1.0 mg l −1 indole-3-butyric acid, 0.1 mg l −1 kinetin, 3% ( w/v) sucrose, and different ratios of ammonium and nitrate (0:30, 5:25, 10:20, 15:15, 20:10, 25:5, and 30:0 mM, using NH 4Cl and KNO 3). The cultures were maintained in darkness. The medium supplemented with 5:25 (mM) NH 4+/NO 3− resulted in the optimum accumulation of biomass and total phenols and flavonoids. The antioxidant potential of a methanolic
extract, measured as the 1, 1-diphenyl-2-picrylhydrazyl and 2, 2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) radical
scavenging activities, of H. perforatum adventitious roots showed that antioxidant activity was high from root extracts that were grown on higher concentrations
of NO 3− nitrogen (15, 20, and 25 mM). Further, assessment of hydrogen peroxide (H 2O 2) and malondialdehyde content of the root extracts revealed that cultures supplemented with higher levels of NO 3− nitrogen (15–30 mM) were under oxidative stress, which boosted the levels of secondary metabolites in the adventitious roots.
These results suggest that optimal adventitious root biomass could be achieved with the supplementation of cultures with 5:25
ratios of MS nitrogen sources. 相似文献
8.
The co-culture system of denitrifying anaerobic methane oxidation (DAMO) and anaerobic ammonium oxidation (Anammox) has a potential application in wastewater treatment plant. This study explored the effects of permutation and combination of nitrate, nitrite, and ammonium on the culture enrichment from freshwater sediments. The co-existence of NO3
−, NO2
−, and NH4
+ shortened the enrichment time from 75 to 30 days and achieved a total nitrogen removal rate of 106.5 mg/L/day on day 132. Even though ammonium addition led to Anammox bacteria increase and a higher nitrogen removal rate, DAMO bacteria still dominated in different reactors with the highest proportion of 64.7% and the maximum abundance was 3.07 ± 0.25 × 108 copies/L (increased by five orders of magnitude) in the nitrite reactor. DAMO bacteria showed greater diversity in the nitrate reactor, and one was similar to M. oxyfera; DAMO bacteria in the nitrite reactor were relatively unified and similar to M. sinica. Interestingly, no DAMO archaea were found in the nitrate reactor. This study will improve the understanding of the impact of nitrogen source on DAMO and Anammox co-culture enrichment. 相似文献
9.
The oxygen-limited autotrophic nitrification/denitrification (OLAND) process comprises one-stage partial nitritation and anammox,
catalyzed by aerobic and anoxic ammonium-oxidizing bacteria (AerAOB and AnAOB), respectively. The goal of this study was to
investigate whether quorum sensing influences anoxic ammonium oxidation in an OLAND biofilm, with AnAOB colonizing 13% of
the biofilm, as determined with fluorescent in situ hybridization (FISH). At high biomass concentrations, the specific anoxic ammonium oxidation rate of the OLAND biofilm significantly
increased with a factor of 1.5 ± 0.2 compared to low biomass concentrations. Supernatant obtained from the biofilm showed
no ammonium-oxidizing activity on itself, but its addition to low OLAND biomass concentrations resulted in a significant activity
increase of the biomass. In the biofilm supernatant, the presence of long-chain acylhomoserine lactones (AHLs) was shown using
the reporter strain Chromobacterium violaceum CV026, and one specific AHL, N-dodecanoyl homoserine lactone (C 12-HSL), was identified via LC-MS/MS. Furthermore, C 12-HSL was detected in an AnAOB-enriched community, but not in an AerAOB-enriched community. Addition of C 12-HSL to low OLAND biomass concentrations resulted in a significantly higher ammonium oxidation rate ( p < 0.05). To our knowledge, this is the first report demonstrating that AHLs enhance the anoxic ammonium oxidation process.
Future work should confirm which species are responsible for the in situ production of C 12-HSL in AnAOB-based applications. 相似文献
10.
Plant–soil interactions have been proposed as a causative mechanism explaining how invasive plant species impact ecosystem
processes. We evaluate whether an invasive plant influences plant and soil-microbe acquisition of nitrogen to elucidate the
mechanistic pathways by which invaders might alter N availability. Using a 15N tracer, we quantify differences in nitrogen uptake and allocation in communities with and without Microstegium vimineum, a shade-tolerant, C 4 grass that is rapidly invading the understories of eastern US deciduous forests. We further investigate if plants or the
microbial biomass exhibit preferences for certain nitrogen forms (glycine, nitrate, and ammonium) to gain insight into nitrogen
partitioning in invaded communities. Understory native plants and M. vimineum took up similar amounts of added nitrogen but allocated it differently, with native plants allocating primarily to roots
and M. vimineum allocating most nitrogen to shoots. Plant nitrogen uptake was higher in invaded communities due primarily to the increase
in understory biomass when M. vimineum was present, but for the microbial biomass, nitrogen uptake did not vary with invasion status. This translated to a significant
reduction ( P < 0.001) in the ratio of microbial biomass to plant biomass nitrogen uptake, which suggests that, although the demand for
nitrogen has intensified, microbes continue to be effective nitrogen competitors. The microbial biomass exhibited a strong
preference for ammonium over glycine and nitrate, regardless of invasion status. By comparison, native plants showed no nitrogen
preferences and M. vimineum preferred inorganic nitrogen species. We interpret our findings as evidence that invasion by M. vimineum leads to changes in the partitioning of nitrogen above and belowground in forest understories, and to decreases in the microbial
biomass, but it does not affect the outcome of plant–microbe–nitrogen interactions, possibly due to functional shifts in the
microbial community as a result of invasion. 相似文献
11.
Batch cultures of the green microalga Chlorella vulgaris and cyanobacterium Planktothrix isothrix and their corresponding co-cultures were grown in municipal wastewater in order to study their growth as well as the nitrogen
(NH 4–N) and phosphorus (PO 43−–P) removal. The cultures were grown under two irradiances of 20 and 60 μmol photons m −2 s −1 in shaken and unshaken conditions. The co-culture of unshaken Chlorella and Planktothrix showed the greatest growth under both irradiances. The monoalgal Planktotrix cultures showed better growth when unshaken than when shaken, whereas Chlorella cultures grew better when mixed, but only at the higher irradiance. The highest percentage of nitrogen removal (up to 80%)
was attained by the unshaken co-cultures of Chlorella and Planktothrix. The amount of nitrogen recycled in the biomass reached up to 85% of that removed. Shaken monoalgal cultures of Chlorella showed phosphorus removal under both irradiances. They completely removed the initial phosphorus concentration (7.47 ± 0.17 mg L −1) within 96 and 48 h under 20 and 60 μmol photons m −2 s −1, respectively. 相似文献
12.
This paper refers to nitrogen removal optimization of an alternating oxidation ditch system through the use of a mathematical
model and pilot testing. The pilot system where measurements have been made has a total volume of 120 m 3 and consists of two ditches operating in four phases during one cycle and performs carbon oxidation, nitrification, denitrification
and settling. The mathematical model consists of one-dimensional mass balance (convection–dispersion) equations based on the
IAWPRC ASM 1 model. After the calibration and verification of the model, simulation system performance was made. Optimization
is achieved by testing operational cycles and phases with different time lengths. The limits of EU directive 91/271 for nitrogen
removal have been used for comparison. The findings show that operational cycles with smaller time lengths can achieve higher
nitrogen removals and that an “equilibrium” between phase time percentages in the whole cycle, for a given inflow, must be
achieved. 相似文献
13.
Toxic at low concentrations, phenol is one of the most common organic pollutants in air and water. In this work, phenol biodegradation
was studied in extreme conditions (80°C, pH = 3.2) in a 2.7 l bioreactor with the thermoacidophilic archaeon Sulfolobus solfataricus 98/2. The strain was first acclimatized to phenol on a mixture of glucose (2000 mg l −1) and phenol (94 mg l −1) at a constant dissolved oxygen concentration of 1.5 mg l −1. After a short lag-phase, only glucose was consumed. Phenol degradation then began while glucose was still present in the
reactor. When glucose was exhausted, phenol was used for respiration and then for biomass build-up. After several batch runs
(phenol < 365 mg l −1), specific growth rate (μ X) was 0.034 ± 0.001 h −1, specific phenol degradation rate (q P) was 57.5 ± 2 mg g −1 h −1, biomass yield (Y X/P) was 52.2 ± 1.1 g mol −1, and oxygen yield factor
( \text Y\textX/\textO 2 ) \left( {{\text{Y}}_{{{\text{X}}/{\text{O}}_{ 2} }} } \right) was 9.2 ± 0.2 g mol −1. A carbon recovery close to 100% suggested that phenol was exclusively transformed into biomass (35%) and CO 2 (65%). Molar phenol oxidation constant
( \text Y\textO 2 /\textP ) \left( {{\text{Y}}_{{{\text{O}}_{ 2} /{\text{P}}}} } \right) was calculated from stoichiometry of phenol oxidation and introducing experimental biomass and CO 2 conversion yields on phenol, leading to values varying between 4.78 and 5.22 mol mol −1. Respiratory quotient was about 0.84 mol mol −1, very close to theoretical value (0.87 mol mol −1). Carbon dioxide production, oxygen demand and redox potential, monitored on-line, were good indicators of growth, substrate
consumption and exhaustion, and can therefore be usefully employed for industrial phenol bioremediation in extreme environments. 相似文献
14.
The impacts of global climatic change on belowground ecological processes of terrestrial ecosystems are still not clear. We
therefore conducted an experiment in the subalpine coniferous forest ecosystem of the eastern edges of the Tibetan Plateau
to study roots of Picea asperata seedlings and rhizosphere soil responses to soil warming and nitrogen availability from April 2007 to December 2008. The
seedlings were subjected to two levels of temperature (ambient; infrared heater warming) and two nitrogen levels (0 or 25 g m −2year −1 N). We used a free air temperature increase from an overhead infrared heater to raise both air and soil temperature by 2.1
and 2.6°C, respectively. The results showed that warming alone significantly increased total biomass, coarse root biomass
and fine root biomass of P. asperata seedlings. Both total biomass and fine root biomass were increased, but coarse root biomass was significantly decreased by
nitrogen fertilization and warming combined with nitrogen fertilization. Warming induced a prominent increase in soil organic
carbon (SOC) and NO 3
−-N of rhizosphere soil, while nitrogen fertilization significantly decreased SOC and NH 4
+-N of rhizosphere soil. The warming, fertilization and warming × N fertilization interaction decreased soil microbial C significantly,
but substantially increased soil microbial N. These results suggest that nitrogen deposition combined with warmer temperatures
under future climatic change possibly will have no effect on fine root production of P. asperata seedlings, but could enhance the nitrification process of their rhizosphere soils in subalpine coniferous forests. 相似文献
15.
In this study, the ammonia removal efficiency for high ammonia-containing wastewaters was evaluated via partial nitrification.
A nitrifier biocommunity was first enriched in a fill-and-draw batch reactor with a specific ammonium oxidation rate of 0.1 mg NH 4
−-N/mg VSS.h. Partial nitrification was established in a chemostat at a hydraulic retention time (HRT) of 1.15 days, which
was equal to the sludge retention time (SRT). The results showed that the critical HRT (SRT) was 1.0 day for the system. A
maximum specific ammonium oxidation rate was achieved as 0.280 mg NH 4
−-N/mg VSS.h, which is 2.8-fold higher than that obtained in the fill-and-draw reactor, indicating that more adaptive and highly
active ammonium oxidizers were enriched in the chemostat. Dynamic modeling of partial nitrification showed that the maximum
growth rate for ammonium oxidizers was found to be 1.22 day −1. Modeling studies also validated the recovery period as 10 days. 相似文献
16.
Providencia rettgeri strain YL was found to be efficient in heterotrophic nitrogen removal under aerobic conditions. Maximum removal of NH 4
+–N occurred under the conditions of pH 7 and supplemented with glucose as the carbon source. Inorganic ions such as Mg 2+, Mn 2+, and Zn 2+ largely influenced the growth and nitrogen removal efficiency. A quantitative detection of nitrogen gas by gas chromatography
was conducted to evaluate the nitrogen removal by strain YL. From the nitrogen balance during heterotrophic growth with 180 mg/l
of NH 4
+–N, 44.5% of NH 4
+–N was in the form of N 2 and 49.7% was found in biomass, with only a trace amount of either nitrite or nitrate. The utilization of nitrite and nitrate
during the ammonium removal process demonstrated that the nitrogen removal pathway by strain YL was heterotrophic nitrification-aerobic
denitrification. A further enzyme assay of nitrate reductase and nitrite reductase activity under the aerobic condition confirmed
this nitrogen removal pathway. 相似文献
17.
揭示不同恢复阶段热带森林土壤细菌呼吸季节变化及其主控因素,对于探明土壤细菌呼吸对热带森林恢复的响应机制具有重要的科学意义。以西双版纳不同恢复阶段热带森林(白背桐群落、崖豆藤群落和高檐蒲桃群落)为研究对象,运用真菌呼吸抑制法及高通量宏基因组测序技术分别测定土壤细菌呼吸速率和细菌多样性,并采用回归分析及结构方程模型揭示热带森林恢复过程中土壤细菌多样性、pH、土壤碳氮组分变化对土壤细菌呼吸速率的影响特征。结果表明:1)不同恢复阶段热带森林土壤细菌呼吸速率表现为:高檐蒲桃群落((1.51±0.62)CO 2 mg g -1 h -1)显著高于崖豆藤群落((1.16±0.56)CO 2 mg g -1 h -1)和白背桐群落((0.82±0.60)CO 2 mg g -1 h -1)(P<0.05)。2)不同恢复阶段土壤细菌呼吸速率呈显著的单峰型季节变化(P<0.05),最大值均出现在9月:高檐蒲桃群落((... 相似文献
18.
The microalgae Chlorella protothecoides UTEX 25, Chlorella sp. TISTR 8991, and Chlorella sp. TISTR 8990 were compared for use in the production of biomass and lipids under photoautotrophic conditions. Chlorella sp. TISTR 8990 was shown to be potentially suitable for lipid production at 30°C in a culture medium that contained only
inorganic salts. For Chlorella sp. TISTR 8990 in optimal conditions in a stirred tank photobioreactor, the lipid productivity was 2.3 mg L −1 h −1 and after 14 days the biomass contained more than 30% lipids by dry weight. To attain this, the nitrogen was provided as
KNO 3 at an initial concentration of 2.05 g L −1 and chelated ferric iron was added at a concentration of 1.2 × 10 −5 mol L −1 on the ninth day. Under the same conditions in culture tubes (36 mm outer diameter), the biomass productivity was 2.8-fold
greater than in the photobioreactor (0.125 m in diameter), but the lipid productivity was only 1.2-fold higher. Thus, the
average low-light level in the photobioreactor actually increased the biomass specific lipid production compared to the culture
tubes. A light-limited growth model closely agreed with the experimental profiles of biomass production, nitrogen consumption,
and lipid production in the photobioreactor. 相似文献
19.
The extreme acid conditions required for scorodite (FeAsO 4·2H 2O) biomineralization (pH below 1.3) are suboptimal for growth of most thermoacidophilic Archaea. With the objective to develop
a continuous process suitable for biomineral production, this research focuses on growth kinetics of thermoacidophilic Archaea
at low pH conditions. Ferrous iron oxidation rates were determined in batch-cultures at pH 1.3 and a temperature of 75°C for
Acidianus sulfidivorans, Metallosphaera prunea and a mixed Sulfolobus culture. Ferrous iron and CO 2 in air were added as sole energy and carbon source. The highest growth rate (0.066 h −1) was found with the mixed Sulfolobus culture. Therefore, this culture was selected for further experiments. Growth was not stimulated by increase of the CO 2 concentration or by addition of sulphur as an additional energy source. In a CSTR operated at the suboptimal pH of 1.1, the
maximum specific growth rate of the mixed culture was 0.022 h −1, with ferrous iron oxidation rates of 1.5 g L −1 d −1. Compared to pH 1.3, growth rates were strongly reduced but the ferrous iron oxidation rate remained unaffected. Influent
ferrous iron concentrations above 6 g L −1 caused instability of Fe 2+ oxidation, probably due to product (Fe 3+) inhibition. Ferric-containing, nano-sized precipitates of K-jarosite were found on the cell surface. Continuous cultivation
stimulated the formation of an exopolysaccharide-like substance. This indicates that biofilm formation may provide a means
of biomass retention. Our findings showed that stable continuous cultivation of a mixed iron-oxidizing culture is feasible
at the extreme conditions required for continuous biomineral formation. 相似文献
20.
Picea asperata is a dominant species in the subalpine coniferous forests distributed in eastern edges of Tibetan Plateau and upper reaches
of the Yangtze River. The paper mainly identified the short-term influences of experimental warming, nitrogen fertilization,
and their combination on growth and physiological performances of Picea asperata seedlings. These seedlings were subjected to two levels of temperature (ambient; infrared heater warming) and two nitrogen
levels (0; 25 g m −2 a −1 N) for 6 months. We used a free air temperature increase of overhead infrared heater to raise both air and soil temperature
by 2.1 and 2.6°C, respectively. The temperature increment induced an obvious enhancement in biomass accumulation and the maximum
net photosynthetic rate, and decreased AOS and MDA level under ambient nitrogen conditions. Whereas, negative effects of experimental
warming on growth and physiology was observed under nitrogen fertilization condition. On the other hand, nitrogen fertilization
significantly improved plant growth in unwarmed plots, by stimulating total biomass, maximum net photosynthetic rate ( A
max), antioxidant compounds, as well as reducing the content of AOS and MDA. However, in warmed plots, nitrogen addition clearly
decreased A
max, antioxidant compounds, and induced higher accumulation of AOS and MDA. Obviously, the beneficial effects of sole nitrogen
on growth and physiology of Picea asperata seedlings could not be magnified by artificial warming. 相似文献
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