An acclimatized mixed microbial culture,predominantly Pseudomonas sp.,was enriched from a sewage treatment plant,and its potential to simultaneously degrade mixtures of phenol and m-cresol was investigated during its ...An acclimatized mixed microbial culture,predominantly Pseudomonas sp.,was enriched from a sewage treatment plant,and its potential to simultaneously degrade mixtures of phenol and m-cresol was investigated during its growth in batch shake flasks.A 22 full factorial design with the two substrates at two different levels and different initial concentration ranges(low and high),was employed to carry out the biodegradation experiments.The substrates phenol and m-cresol were completely utilized within 21 h when ...展开更多
Because the lack of detailed study of biological decolorization in high salt dye wastewater, it is still difficult to evaluate the biological treatment on high-salinity dye wastewater. The experiments were carried out...Because the lack of detailed study of biological decolorization in high salt dye wastewater, it is still difficult to evaluate the biological treatment on high-salinity dye wastewater. The experiments were carried out to study the salt-tolerant bacteria, which is useful in the treatment of high-salinity colored wastewater. Simulated wastewater containing 5-150 g/L salt (NaCI) and 50-2000 mg/L Reactive Brilliant Red K-2BP was treated with three salt-tolerant mixed cultures (CAS, TAS, DSAS), which were under a gradually acclimated procedure. With the increase of concentrations of salt and dye, the decolorization became low. The abilities of decolorization of dyes wastewater by three mixed cultures (CAS, TAS, DSAS) were studied, CAS and DSAS mixed cultures showed more active for the treatment of high-salinity colored wastewater than TAS mixed cultures. The results suggested that there might be a simple process for the high salt wastewater treatment, which could be incorporated into conventional activated sludge plants.展开更多
Enhanced UV-B(280-320 nm) radiation resulting from ozone depletion is one of global environmental problems. Not only marine organisms but also marine ecosystems can be affected by enhanced UV-B radiation. The effects ...Enhanced UV-B(280-320 nm) radiation resulting from ozone depletion is one of global environmental problems. Not only marine organisms but also marine ecosystems can be affected by enhanced UV-B radiation. The effects of UV-B radiation on interaction of macro-algae and micro-algae were investigated using Ulva pertusa Kjellman and Alexandrium tamarense as the materials in this study. The results demonstrated that UV-B radiation could inhibit the growth of Ulva pertusa and Alexandrium tamarense when they were both mono-cultured, and the growth inhibition of algae was more significant with increasing doses of UV-B radiation. Alexandrium tamarense could inhibit the growth of Ulva pertusa in mixed culture, and the growth inhibition was more significant when increasing the initial cell density. However, Ulva pertusa could inhibit the growth of Alexandrium tamarense in early phase and stimulate the growth in latter phase when they were grown in mixed culture. Lower initial cell density(10~2 cell/ml) of Alexandrium tamarense could inhibit the growth of Ulva pertusa under UV-B radiation treatment,however, with the initial cell density increasing(10~3 and 10~4 cell/ml), the growth of Ulva pertusa was stimulated under lower dose of UV-B radiation and inhibited under higher dose of UV-B radiation by Alexandrium tamarense. Compared with that in mixed culture, Ulva pertusa showed more positive inhibition to the growth of Alexandrium tamarense under UV-B radiation treatment.展开更多
To determine the efficacy of chalcopyrite bioleaching using pure cultures of Thiobacillus ferrooxidans or Thiobacillus thiooxidans and a mixed culture composed of Thiobacillus ferrooxidans and Thiobacillus thiooxidans...To determine the efficacy of chalcopyrite bioleaching using pure cultures of Thiobacillus ferrooxidans or Thiobacillus thiooxidans and a mixed culture composed of Thiobacillus ferrooxidans and Thiobacillus thiooxidans, experiments were carried out in shake flasks with [Fe^2+] 4 g·L^-1 and S 1 g·L^-1 at pH=1.80, 130 r/min and 30℃. The tests showed that the copper extraction in a mixed culture composed of Thiobacillusferrooxidans and Thiobacillus thiooxidans is higher than that in a pure culture. On the other hand, an important potential of Thiobacillus thiooxidans to leaching chalcopyrite was indicated. Thiobacillus thiooxidans can prevent jarosites accumulating on the substrate and allow further copper to dissolute through the action of ferric ion. The selection of the suitable pH in a leaching solution would be significant. Thiobacillus thiooxidans and Thiobacillus ferrooxidans play an important role in the bioleaching process. Finally, the mechanism and the reason for iron precipitation were also discussed in detail.展开更多
BACKGROUND: Cultures from multiple portions of umbilical cord blood mesenchymal stem cells have been shown to undergo more rapid proliferation and attachment than single portions. OBJECTIVE: To observe growth of bas...BACKGROUND: Cultures from multiple portions of umbilical cord blood mesenchymal stem cells have been shown to undergo more rapid proliferation and attachment than single portions. OBJECTIVE: To observe growth of basic fibroblast growth factor (bFGF)-induced cultures of human amnion-derived mesenchymal stem cells (AMSCs) and differentiation into neuronal-like cells. DESIGN, TIME AND SETTING: Comparative observation. The study was performed at the Laboratory of Microbiology and Immunology, Basic Medical School of Zhengzhou University from January to May 2008. METHODS: Amnia from full-term, uterine-incision delivery were donated by 12 healthy women. AMSCs were obtained by cell separation and culture techniques, and were passaged and induced by bFGF. From the third passage, a total of 1 mLAMSCs, at a density of 1.0 × 10^4/mL, was separately harvested from six samples, which served as group A. A total of 1 mL AMSCs, at a density of 1.0 × 10^4/mL, was harvested separately from the remaining six samples, which served a group B. A total of 0.5 mL from the six samples of group A and 0.5 mL from the six samples of grot, B were combined to form group C. MAIN OUTCOME MEASURES: Differences in cell quantity among the three groups were compare by cell quantification and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) analysis. Expression of a glial cell marker, neuron-specific enolase, and nestin was detected in the three groups by immunocytochemistry. RESULTS: Cell quantification and MTT analysis of live cells, as well as AMSC absorbance, were significantly greater in group C compared with groups A and B at 18 days of culture (P 〈 0.05), anc no significant difference was observed between groups A and B. Glial fibrillary acidic protein, neuron-specific enolase, and nestin were expressed in all groups following bFGF induction. CONCLUSION: Mixed AMSC cultures promoted proliferation, and bFGF-induced AMSCs differentiated into neuronal-like cells.展开更多
In the system of nitric oxide removal from the flue gas by metal chelate absorption, it is an obstacle that ferrous absorbents are easily oxidized by oxygen in the flue gas to ferric counterparts, which are not capabl...In the system of nitric oxide removal from the flue gas by metal chelate absorption, it is an obstacle that ferrous absorbents are easily oxidized by oxygen in the flue gas to ferric counterparts, which are not capable of binding NO. By adding iron metal or electrochemical method, Fe III (EDTA) can be reduced to Fe II (EDTA). However, there are various drawbacks associated with these techniques. The dissimilatory reduction of Fe III (EDTA) with microorganisms in the system of nitric oxide removal by metal chelate absorption was investigated. Ammonium salt instead of nitrate was used as the nitrogen source, as nitrates inhibited the reduction of Fe III due to the competition between the two electron acceptors. Supplemental glucose and lactate stimulated the formation of Fe II more than ethanol as the carbon sources. The microorganisms cultured at 50℃ were not very sensitive to the other experimental temperature, the reduction percentage of Fe III varied little with the temperature range of 30—50℃. Concentrated Na 2CO 3 solution was added to adjust the solution pH to an optimal pH range of 6—7 The overall results revealed that the dissimilatory ferric reducing microorganisms present in the mix culture are probably neutrophilic, moderately thermophilic Fe III reducers.展开更多
The production of polyhydroxyalkanoates(PHA) from wastewaters using microbial mixed cultures(MMC) has been attracting increased interest because of PHA's biodegradability characteristics. Production of PHA by an M...The production of polyhydroxyalkanoates(PHA) from wastewaters using microbial mixed cultures(MMC) has been attracting increased interest because of PHA's biodegradability characteristics. Production of PHA by an MMC enriched with PHA-accumulating bacteria was compared using anaerobically treated and acidified brewery wastewaters under various feeding strategies, namely pulse and batch feed addition. To obtain an enriched MMC, a sequencing batch reactor was inoculated with activated sludge fed with acetate and subjected to aerobic dynamic feeding. The enriched MMC was able to accumulate PHA up to 72.6% of cell dry weight(CDW) with pulse addition of acetate controlled by the dissolved oxygen(DO) concentration in the reactor. In a batch accumulation experiment with acetate,the PHA content achieved(28.5% CDW) was less than that of the pulse feeding strategy with the same amount of acetate(~2000 mg C/L). Using anaerobically treated and acidified brewery wastewater fed in pulses, the maximum PHA accumulated by the enriched MMC was similar for both wastewaters(45% CDW), in spite of the higher volatile fatty acid concentration in acidified brewery wastewater. The pulse feed addition controlled by the DO concentration was difficult to implement for wastewater as compared to acetate because the difference in DO concentration between substrate availability and depletion was low. For the batch addition of acidified wastewater, a slightly lower PHA content(39%CDW) was obtained. These results show that both brewery wastewaters can be utilized for PHA production with a similar maximum PHA storage capacity.展开更多
The production of bio-hydrogen from raw cassava starch via a mixed-culture dark fermentation process was investigated. The production yield of H2 was optimized by adjusting the substrate concentration and the microorg...The production of bio-hydrogen from raw cassava starch via a mixed-culture dark fermentation process was investigated. The production yield of H2 was optimized by adjusting the substrate concentration and the microorganism mixture ratio. A maximum H2 yield of 1.72 mol H2/mol glucose was obtained with a cassava starch concentration of 10 g/L to give a 90% utilization rate. The kinetics of the substrate utilization and of the generation of both hydrogen and volatile fatty acids were also investigated. The substrate utilization follows pseudo first order reaction kinetics, whereas the production of both H2 and the VFAs correlate with the Gompertz equation. These results show that cassava is a good candidate for the production of biohydrogen.展开更多
Transgenic soybean plants overexpressing the Arabidopsis purple acid phosphatase gene AtPAP15 (OXp) or the soybean expansin gene GmEXPB2 (OXe) can improve phosphorous (P) efficiency in pure culture by increasing...Transgenic soybean plants overexpressing the Arabidopsis purple acid phosphatase gene AtPAP15 (OXp) or the soybean expansin gene GmEXPB2 (OXe) can improve phosphorous (P) efficiency in pure culture by increasing Apase secretion or changing root morphology. In this study, soybean‐soybean mixed cultures were employed to il uminate P acquisition among plants in mixed stands of transgenic and wild‐type soybean. Our results showed that transgenic soybean plants were much more competitive, and had greater growth and P uptake than wild‐type soybean in mixed culture in both low P calcareous and acid soils. Furthermore, OXe plants had an advantage in calcareous soils when mixed with OXp, whereas the latter performed much better in acid soils. In soybean‐maize mixed culture, transgenic soybean had no impact on maize growth compared to controls in both acid and calcareous soils with different P conditions. As for soybean in mixed culture, OXp plants had no significant advantages regardless of P availability or soil type, while P efficiency improved in OXe in calcareous soils compared to controls. These results imply that physiological traits could be easily affected by the mixed maize. Transgenic soybean plants with enhanced root traits had more competitive advantages than those with improved root physiology in mixed culture.展开更多
The purpose of this work is to study the co-cultivation of Chlorella sp. and wastewater wild algae under different cultivation conditions (i.e. CO2, light intensity, cultivation time, and inoculation ratio) for enha...The purpose of this work is to study the co-cultivation of Chlorella sp. and wastewater wild algae under different cultivation conditions (i.e. CO2, light intensity, cultivation time, and inoculation ratio) for enhanced algal biomass and lipid productivity in wastewater medium using Response SuHhce Methodology (RSM). The results show that mixed cultures ofd7llorella sp. and wastewater wild algae increase biomass and lipid yield. Additionally, findings indicate that CO2, light intensity and cultivation time significantly affect algal productivity. Furthcnnore, CO2 concentration and light intensity, and CO2 concentration and algal composition, have an interactive effect on biomass productivity. Under dii"ferent cultivation conditions, the response of algal biomass, cell count, and lipid productlvlty ranges from2,5 to 10.2 mg/mL 1.1 × 10 to 8.2 × 10 cells/mL and 1.1 × 10^6 to 6.8 × 10^12 total fluorescent units/mL, respectively× The optimum conditions tbr simt, ltaneot, s biomass and lipid accumulation are 3.6% of CO2 (v/v), 160 μmol/m^2/s of light intensity, 1×6/2.4 of inoculation ratio (wastewater-algae/Chlorella), and 8.3 days of cultivation time. The optimal productivity is 9,8 (g/L) for dry biomass, 8.6 E + 08 (cells/mL) for cell count, and 6.8 E + 12 (Total FL units per mL) fbr lipid yield, achieving up to four times, eight times, and seven times higher productivity compared to non- optimized conditions. Provided is a supportive methodology to improve mixed algal culture for hioenergy feedstock generation and to optimize cultivation conditions in complex wastewater environments. This work is an important step tbrward in the development of sustainable large-scale algae cultivation for cost-efficient generation of biofuel.展开更多
The production of polyhydroxyalkanoates (PHAs) with a high fraction of 3-hydroxyvalerate (3HV) and 3-hydroxy-2-methylvalerate (3H2/MV) from mixed culture enriched by valerate-dominant hydrolysate was evaluated i...The production of polyhydroxyalkanoates (PHAs) with a high fraction of 3-hydroxyvalerate (3HV) and 3-hydroxy-2-methylvalerate (3H2/MV) from mixed culture enriched by valerate-dominant hydrolysate was evaluated in this study. After long-term enrichment, the culture showed strong ability to synthesize 3HV and 3H2MV, even with acetate-dominant substrate. The ultilization of single or mixed iso-/n-valerate by the enriched culture showed that the mixture of iso-valerate and n-valerate was more efficient substrate than any single in tenaas of balancing microbial growth and PHAs synthesis. Besides, through comparing the kinetics and stoichiometry of the tests supplying valerate and propionate, the enriched culture with equivalent valerate and propionate (1 : 1 molar ratio) exhibited superior PHAs production performances to pure valerate or propionate, attaining more than 70 tool% of 3HVand 3H2MV. The above findings reveal that valerate-dominant hydrolysate is a kind of suitable substrate to enrich PHAs producing culture with great capability to synthesize 3HV and 3H2MV monomers, thus improving product properties than pure poly(3-hydroxybutyrate) (P3HB); also 3HV and 3H2MV production behaviors can be regulated by the type of odd-carbon VFAs in the substrate.展开更多
Four sequence batch reactors(SBRs) fed by fermented sugar cane wastewater were continuously operated under the aerobic dynamic feeding(ADF) mode with different configurations of sludge retention time(SRT), carbo...Four sequence batch reactors(SBRs) fed by fermented sugar cane wastewater were continuously operated under the aerobic dynamic feeding(ADF) mode with different configurations of sludge retention time(SRT), carbon and initial biomass concentrations to enrich polyhydroxyalkanoate(PHA) accumulating mixed microbial cultures(MMCs) from municipal activated sludge.The stability of SBRs was investigated besides the enrichment performance. The microbial community structures of the enriched MMCs were analyzed using terminal restriction fragment length polymorphism(T-RFLP). The optimum operating conditions for the enrichment process were: SRT of 5 days, carbon concentration of 2.52 g COD/L and initial biomass concentration of3.65 g/L. The best enrichment performance in terms of both operating stability and PHA storage ability of enriched cultures(with the maximum PHA content and PHA storage yield(YPHA/S) of61.26% and 0.68 mg COD/mg COD, respectively) was achieved under this condition. Effects of the SRT, carbon concentration and initial biomass concentration on the PHA accumulating MMCs selection process were discussed respectively. A new model including the segmentation of the enrichment process and the effects of SRT on each phase was proposed.展开更多
Two chromium removal experiments were performed in bioreactors with and without a magnetic field under the same conditions.The release of the chromium present in the biomass was tested in two experiments one with the ...Two chromium removal experiments were performed in bioreactors with and without a magnetic field under the same conditions.The release of the chromium present in the biomass was tested in two experiments one with the initial pH of the medium and one with pH 4.0.The objective was to remove Cr(Ⅵ)and total Cr from the effluent,this was carried out by placing biological treatments of synthetic effluent contaminated with 100 mg/L of Cr(Ⅵ)in a bioreactor with neodymium magnets that applied a magnetic field(intensity85.4 mT)to the mixed culture.The removal of Cr(Ⅵ)was approximately 100.0%for the bioreactor with a magnetic field and 93,3%for the bioreactor without a magnetic field for9 hr of recirculation of the synthetic effluent by the bioreactor.The removal of total Cr was61.6%and 48.4%,with and without a magnetic field,respectively;for 24 hr.The desorption of Cr(VI)in the synthetic effluent was 0.05 mg/L,which is below the limit established by Brazilian legislation(0.1 mg/L)for the discharge of effluent containing Cr(Ⅵ)into bodies of water.The results obtained for the removal of chromium in synthetic effluent suggested that there was no significant influence on the viable cell count of the mixed culture.The desorption of Cr(Ⅵ)in synthetic effluent after bioadsorption of chromium by the mixed culture in the process of removal of chromium in bioreactors with and without a magnetic field was not significant in either of the experiments with different initial pHs.展开更多
The effect of aeration conditions and pH control on the progress and efficiency of beet molasses vinasse biodegradation was investigated during four batch processes at 38°C with the mixed microbial culture compos...The effect of aeration conditions and pH control on the progress and efficiency of beet molasses vinasse biodegradation was investigated during four batch processes at 38°C with the mixed microbial culture composed of Bifidobacterium,Lactobacillus,Lactococcus,Streptococcus,Bacillus,Rhodopseudomonas,and Saccharomyces.The four processes were carried out in a shake flask with no pH control,an aerobic bioreactor without mixing with no pH control,and a stirred-tank reactor (STR) with aeration with and without pH control,respectively.All experiments were started with an initial pH 8.0.The highest efficiency of biodegradation was achieved through the processes conducted in the STR,where betaine (an organic pollutant occurring in beet molasses in very large quantities) was completely degraded by the microorganisms.The process with no pH control carried out in the STR produced the highest reduction in the following pollution measures:organic matter expressed as chemical oxygen demand determined by the dichromatic method + theoretical COD of betaine (COD sum,85.5%),total organic carbon (TOC,78.8%) and five-day biological oxygen demand (BOD 5,98.6%).The process conditions applied in the shake flask experiments,as well as those used in the aerobic bioreactor without mixing,failed to provide complete betaine assimilation.As a consequence,reduction in COD sum,TOC and BOD 5 was approximately half that obtained with STR.展开更多
This study focuses on identifying the factors under which mixed microbial seeds assist bio-chemical denitrification when Scrap Iron Filings(SIF)are used as electron donors and adsorbents in low C/N ratio waters.Batch ...This study focuses on identifying the factors under which mixed microbial seeds assist bio-chemical denitrification when Scrap Iron Filings(SIF)are used as electron donors and adsorbents in low C/N ratio waters.Batch studies were conducted in abiotic and biotic reactors containing fresh and aged SIF under different dissolved oxygen concentrations with NO_(3)^(-)−N and/or PO_(4)^(3−)influent(s)and their nitrate/phosphate removal and by-product formations were studied.Batch reactors were seeded with a homogenized mixed microbial inoculum procured from natural sludges which were enriched over 6 months under denitrifying conditions in the presence of SIF.Results indicated that when influent containing 40 mg/L of NO_(3)^(-)−N was treated with 5 g SIF,79.9%nitrate reduction was observed in 8 days abiotically and 100%removal was accomplished in 20 days when the reactor was seeded.Both abiotic and seeded reactors removed more than 92%PO_(4)^(3−)under high DO conditions in 12 days.Abiotic and biochemical removal of NO_(3)^(-)−N and abiotic removal of PO_(4)^(3−)were higher under independent NO_(3)^(-)−N/PO_(4)^(3−)loading,while 99%PO_(4)^(3−)was removed biochemically under combined NO_(3)^(-)−N and PO_(4)^(3−)loading.This study furthers the understandings of nitrate and phosphate removal in Zero Valent Iron(ZVI)assisted mixed microbial systems to encourage the application of SIF-supported bio-chemical processes in the simultaneous removals of these pollutants.展开更多
Polyhydroxyalkanoates(PHAs)are the polymers of hydroxyalkanoates that accumulate as carbon/energy or reducing-power storage material in various microorganisms.PHAs have attracted considerable attention as biodegradabl...Polyhydroxyalkanoates(PHAs)are the polymers of hydroxyalkanoates that accumulate as carbon/energy or reducing-power storage material in various microorganisms.PHAs have attracted considerable attention as biodegradable substitutes for conventional polymers.Until now,however,industrial production of PHAs has encountered only limited success.The main barrier to the replacement of synthetic plastics by PHAs has been the higher cost.The use of mixed cultures and renewable sources obtained from waste organic carbon can substantially decrease the cost of PHA and increase their market potential.This work reviews two main methods of PHA production by mixed cultures,anaerobic-aerobic processing and aerobic transient feeding processing,and analyzed the metabolic and effective factors.展开更多
Two acetate-fed sequencing batch reactors (SBR) were operated under an aerobic dynamic feeding (ADF) model (SBR#2) and with anaerobic phase before aerobic phase (SBR#1) to select mixed cultures with a high pol...Two acetate-fed sequencing batch reactors (SBR) were operated under an aerobic dynamic feeding (ADF) model (SBR#2) and with anaerobic phase before aerobic phase (SBR#1) to select mixed cultures with a high polyhydroxyalkanoates (PHA) storage response. Although kinetic selection based on storage response should bring about a predominance of floc-formers, a bulking sludge with storage response comparable to well-settled sludge was steadily established. An anaerobic phase was introduced before the aerobic phase in the ADF model to improve the sludge settleability (SBR #1), however, due to the consequent increased feast/famine ratio, the performance of SBR #1, in terms of both the maximum PHB (polyhydroxybutyrate) cell content and APHB, was lower than that of SBR #2. SBR #2 gradually reached a steady state while SBR #1 failed suddenly after 50 days of operation. The maximum specific substrate uptake rate and storage rate for the selected bulking sludge were 0.4 Cmol Ae/(Cmol X.hr) and 0.18 Cmol Ac/(Cmol PHB.hr), respectively, resulting a yield of 0.45 Cmol PHB/(Cmol Ae) in SBR #2 in the culture enrichment phase. A maximum PHB content of 53% of total suspended solids and PHB storage rate of 1.36 Cmol Ac/(Cmol PHB.hr) was achieved at 10.2 hr in batch accumulation tests under nitrogen starvation. The results indicated that it was feasible to utilize filamentous bacteria to accumulate PHA with a rate comparable to well-settled sludge, Furthermore, the lower dissolved oxygen demand of filamentous bacteria would save energy required for aeration in the culture enrichment stage.展开更多
In the two-step vitamin C fermentation process, its precursor 2-keto-L-gulonic acid was synthesized from L-sorbose by mixed culture of Gluconobacter oxydans and Bacillus megaterium. The interaction between Gluconobact...In the two-step vitamin C fermentation process, its precursor 2-keto-L-gulonic acid was synthesized from L-sorbose by mixed culture of Gluconobacter oxydans and Bacillus megaterium. The interaction between Gluconobacter oxydans and Bacillus megaterium remains unclear and it is a challenge to mathematically model the mixed growth of these two strains. The Monod-type equations were previously proposed to describe the coupled growth of Gluconobacter oxydans and Bacillus megaterium. However, in this study, we modeled the interaction of these two strains in a macroscopic view by introducing the population theory. Taking account of the fact that the density or concentration of Gluconobacter oxydans or Bacillus megaterium was hardly to measure accurately in the mixed culture broth, the data of concentrations of the substrate and product were used to indirectly investigate the relation between these two strains. Three batch experiments were used to validate our model. And according to the values of identified parameters, the type of interaction between Gluconobacter oxydans and Bacillus megaterium was concluded to be predation, where Gluconobacter oxydans was predator, and Bacillus megaterium was prey.展开更多
A continuous fluidized bed bioreactor (FBBR) with nylon support particles was used to treat synthetic sulfide wastewater at different hydraulic retention time of 25, 50 and 75 min and upflow velocity of 14, 17 and 2...A continuous fluidized bed bioreactor (FBBR) with nylon support particles was used to treat synthetic sulfide wastewater at different hydraulic retention time of 25, 50 and 75 min and upflow velocity of 14, 17 and 20 m/hr. The effects of upflow velocity, hydraulic retention time and reactor operation time on sulfide oxidation rate were studied using statistical model. Mixed culture obtained from the activated sludge, taken from tannery effluent treatment plant, was used as a source for microorganisms. The diameter and density of the nylon particles were 2-3 mm and 1140 kg/m3, respectively. Experiments were carried out in the reactor at a temperature of (30 ± 2)°C, at a fixed bed height of 16 cm after the formation of biofilm on the surface of support particles. Biofilm thickness reached (42 ± 3) μm after 15 days from reactor start-up. The sulfide oxidation, sulfate and sulfur formation is examined at all hydraulic retention times and upflow velocities. The results indicated that almost 90%-92% sulfide oxidation was achieved at all hydraulic retention times. Statistical model could explain 94% of the variability and analysis of variance showed that upflow velocity and hydraulic retention time slightly affected the sulfide oxidation rate. The highest sulfide oxidation of 92% with 70% sulfur was obtained at hydraulic retention time of 75 min and upflow velocity of 14 m/hr.展开更多
The main approach to reduce graft rejection has been focused on the development of immunosuppressive agents at present.Although these strategies have reportedly reduced graft rejection,there has been a reciprocal incr...The main approach to reduce graft rejection has been focused on the development of immunosuppressive agents at present.Although these strategies have reportedly reduced graft rejection,there has been a reciprocal increase in more severe immunosuppression and lethal infections,as well as severe side effects.Blockade of costimulatory T cell response has been proved as one of useful strategies to reduce graft rejection.Furthermore, it has been shown that infusion of dendritic cells(DCs)with a potent negative regulatory ability for T cells could prolong allograft survival.In this study mouse DCs(mDCs)were transfected with the recombinant plasmid pcDNA3.0 containing mouse inducible costimulator-Ig(mICOS-Ig) cDNA by electroporation.The transient expression of mICOS-Ig in mDC could be detected by ELISA and SDS-PAGE.Mouse ICOS-Ig fusion protein expressed in mDC and mICOS-Ig gene-modified mDC could inhibit lymphocyte proliferation in mixed lymphocyte culture(MLC)in vitro.Furthermore,mICOS-Ig gene-modified mDC could inhibit lymphocyte proliferation in recipient mice.These results suggested that mICOS-Ig gene-modified mDC exerted inhibitory effects on T cells,and might be suitable for treatment or prevention of graft rejection and immunopathologic diseases.Cellular & Molecular Immunology.2004;1(2):153-157.展开更多
文摘An acclimatized mixed microbial culture,predominantly Pseudomonas sp.,was enriched from a sewage treatment plant,and its potential to simultaneously degrade mixtures of phenol and m-cresol was investigated during its growth in batch shake flasks.A 22 full factorial design with the two substrates at two different levels and different initial concentration ranges(low and high),was employed to carry out the biodegradation experiments.The substrates phenol and m-cresol were completely utilized within 21 h when ...
文摘Because the lack of detailed study of biological decolorization in high salt dye wastewater, it is still difficult to evaluate the biological treatment on high-salinity dye wastewater. The experiments were carried out to study the salt-tolerant bacteria, which is useful in the treatment of high-salinity colored wastewater. Simulated wastewater containing 5-150 g/L salt (NaCI) and 50-2000 mg/L Reactive Brilliant Red K-2BP was treated with three salt-tolerant mixed cultures (CAS, TAS, DSAS), which were under a gradually acclimated procedure. With the increase of concentrations of salt and dye, the decolorization became low. The abilities of decolorization of dyes wastewater by three mixed cultures (CAS, TAS, DSAS) were studied, CAS and DSAS mixed cultures showed more active for the treatment of high-salinity colored wastewater than TAS mixed cultures. The results suggested that there might be a simple process for the high salt wastewater treatment, which could be incorporated into conventional activated sludge plants.
文摘Enhanced UV-B(280-320 nm) radiation resulting from ozone depletion is one of global environmental problems. Not only marine organisms but also marine ecosystems can be affected by enhanced UV-B radiation. The effects of UV-B radiation on interaction of macro-algae and micro-algae were investigated using Ulva pertusa Kjellman and Alexandrium tamarense as the materials in this study. The results demonstrated that UV-B radiation could inhibit the growth of Ulva pertusa and Alexandrium tamarense when they were both mono-cultured, and the growth inhibition of algae was more significant with increasing doses of UV-B radiation. Alexandrium tamarense could inhibit the growth of Ulva pertusa in mixed culture, and the growth inhibition was more significant when increasing the initial cell density. However, Ulva pertusa could inhibit the growth of Alexandrium tamarense in early phase and stimulate the growth in latter phase when they were grown in mixed culture. Lower initial cell density(10~2 cell/ml) of Alexandrium tamarense could inhibit the growth of Ulva pertusa under UV-B radiation treatment,however, with the initial cell density increasing(10~3 and 10~4 cell/ml), the growth of Ulva pertusa was stimulated under lower dose of UV-B radiation and inhibited under higher dose of UV-B radiation by Alexandrium tamarense. Compared with that in mixed culture, Ulva pertusa showed more positive inhibition to the growth of Alexandrium tamarense under UV-B radiation treatment.
文摘To determine the efficacy of chalcopyrite bioleaching using pure cultures of Thiobacillus ferrooxidans or Thiobacillus thiooxidans and a mixed culture composed of Thiobacillus ferrooxidans and Thiobacillus thiooxidans, experiments were carried out in shake flasks with [Fe^2+] 4 g·L^-1 and S 1 g·L^-1 at pH=1.80, 130 r/min and 30℃. The tests showed that the copper extraction in a mixed culture composed of Thiobacillusferrooxidans and Thiobacillus thiooxidans is higher than that in a pure culture. On the other hand, an important potential of Thiobacillus thiooxidans to leaching chalcopyrite was indicated. Thiobacillus thiooxidans can prevent jarosites accumulating on the substrate and allow further copper to dissolute through the action of ferric ion. The selection of the suitable pH in a leaching solution would be significant. Thiobacillus thiooxidans and Thiobacillus ferrooxidans play an important role in the bioleaching process. Finally, the mechanism and the reason for iron precipitation were also discussed in detail.
基金the Medical Science and Technology Innovation Talent Project of Henan Province,No. 2005018the Jiangsu Public Technology Service Platform of Infrastructure Development,No. SBM200810039
文摘BACKGROUND: Cultures from multiple portions of umbilical cord blood mesenchymal stem cells have been shown to undergo more rapid proliferation and attachment than single portions. OBJECTIVE: To observe growth of basic fibroblast growth factor (bFGF)-induced cultures of human amnion-derived mesenchymal stem cells (AMSCs) and differentiation into neuronal-like cells. DESIGN, TIME AND SETTING: Comparative observation. The study was performed at the Laboratory of Microbiology and Immunology, Basic Medical School of Zhengzhou University from January to May 2008. METHODS: Amnia from full-term, uterine-incision delivery were donated by 12 healthy women. AMSCs were obtained by cell separation and culture techniques, and were passaged and induced by bFGF. From the third passage, a total of 1 mLAMSCs, at a density of 1.0 × 10^4/mL, was separately harvested from six samples, which served as group A. A total of 1 mL AMSCs, at a density of 1.0 × 10^4/mL, was harvested separately from the remaining six samples, which served a group B. A total of 0.5 mL from the six samples of group A and 0.5 mL from the six samples of grot, B were combined to form group C. MAIN OUTCOME MEASURES: Differences in cell quantity among the three groups were compare by cell quantification and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) analysis. Expression of a glial cell marker, neuron-specific enolase, and nestin was detected in the three groups by immunocytochemistry. RESULTS: Cell quantification and MTT analysis of live cells, as well as AMSC absorbance, were significantly greater in group C compared with groups A and B at 18 days of culture (P 〈 0.05), anc no significant difference was observed between groups A and B. Glial fibrillary acidic protein, neuron-specific enolase, and nestin were expressed in all groups following bFGF induction. CONCLUSION: Mixed AMSC cultures promoted proliferation, and bFGF-induced AMSCs differentiated into neuronal-like cells.
文摘In the system of nitric oxide removal from the flue gas by metal chelate absorption, it is an obstacle that ferrous absorbents are easily oxidized by oxygen in the flue gas to ferric counterparts, which are not capable of binding NO. By adding iron metal or electrochemical method, Fe III (EDTA) can be reduced to Fe II (EDTA). However, there are various drawbacks associated with these techniques. The dissimilatory reduction of Fe III (EDTA) with microorganisms in the system of nitric oxide removal by metal chelate absorption was investigated. Ammonium salt instead of nitrate was used as the nitrogen source, as nitrates inhibited the reduction of Fe III due to the competition between the two electron acceptors. Supplemental glucose and lactate stimulated the formation of Fe II more than ethanol as the carbon sources. The microorganisms cultured at 50℃ were not very sensitive to the other experimental temperature, the reduction percentage of Fe III varied little with the temperature range of 30—50℃. Concentrated Na 2CO 3 solution was added to adjust the solution pH to an optimal pH range of 6—7 The overall results revealed that the dissimilatory ferric reducing microorganisms present in the mix culture are probably neutrophilic, moderately thermophilic Fe III reducers.
基金the DAAD Sandwich Model Scholarships for Master's Students of the IITs and IIMs, 2016/17, who funded the research stay of Mr.Pravesh Tamang in Germany (Personal Ref No: 91635161)
文摘The production of polyhydroxyalkanoates(PHA) from wastewaters using microbial mixed cultures(MMC) has been attracting increased interest because of PHA's biodegradability characteristics. Production of PHA by an MMC enriched with PHA-accumulating bacteria was compared using anaerobically treated and acidified brewery wastewaters under various feeding strategies, namely pulse and batch feed addition. To obtain an enriched MMC, a sequencing batch reactor was inoculated with activated sludge fed with acetate and subjected to aerobic dynamic feeding. The enriched MMC was able to accumulate PHA up to 72.6% of cell dry weight(CDW) with pulse addition of acetate controlled by the dissolved oxygen(DO) concentration in the reactor. In a batch accumulation experiment with acetate,the PHA content achieved(28.5% CDW) was less than that of the pulse feeding strategy with the same amount of acetate(~2000 mg C/L). Using anaerobically treated and acidified brewery wastewater fed in pulses, the maximum PHA accumulated by the enriched MMC was similar for both wastewaters(45% CDW), in spite of the higher volatile fatty acid concentration in acidified brewery wastewater. The pulse feed addition controlled by the DO concentration was difficult to implement for wastewater as compared to acetate because the difference in DO concentration between substrate availability and depletion was low. For the batch addition of acidified wastewater, a slightly lower PHA content(39%CDW) was obtained. These results show that both brewery wastewaters can be utilized for PHA production with a similar maximum PHA storage capacity.
基金The authors express their thanks for the support from the National Natural Science Foundation of China (Grant No. 21525625), the National Basic Research Program of China (973 Program, Grant No. 2014CB745100), the National High Technology Research and Development Program of China (863 Program, Grant No. 2013AA020302).
文摘The production of bio-hydrogen from raw cassava starch via a mixed-culture dark fermentation process was investigated. The production yield of H2 was optimized by adjusting the substrate concentration and the microorganism mixture ratio. A maximum H2 yield of 1.72 mol H2/mol glucose was obtained with a cassava starch concentration of 10 g/L to give a 90% utilization rate. The kinetics of the substrate utilization and of the generation of both hydrogen and volatile fatty acids were also investigated. The substrate utilization follows pseudo first order reaction kinetics, whereas the production of both H2 and the VFAs correlate with the Gompertz equation. These results show that cassava is a good candidate for the production of biohydrogen.
基金supported by National Key Basic Research Special Funds of China (2011CB100301)
文摘Transgenic soybean plants overexpressing the Arabidopsis purple acid phosphatase gene AtPAP15 (OXp) or the soybean expansin gene GmEXPB2 (OXe) can improve phosphorous (P) efficiency in pure culture by increasing Apase secretion or changing root morphology. In this study, soybean‐soybean mixed cultures were employed to il uminate P acquisition among plants in mixed stands of transgenic and wild‐type soybean. Our results showed that transgenic soybean plants were much more competitive, and had greater growth and P uptake than wild‐type soybean in mixed culture in both low P calcareous and acid soils. Furthermore, OXe plants had an advantage in calcareous soils when mixed with OXp, whereas the latter performed much better in acid soils. In soybean‐maize mixed culture, transgenic soybean had no impact on maize growth compared to controls in both acid and calcareous soils with different P conditions. As for soybean in mixed culture, OXp plants had no significant advantages regardless of P availability or soil type, while P efficiency improved in OXe in calcareous soils compared to controls. These results imply that physiological traits could be easily affected by the mixed maize. Transgenic soybean plants with enhanced root traits had more competitive advantages than those with improved root physiology in mixed culture.
文摘The purpose of this work is to study the co-cultivation of Chlorella sp. and wastewater wild algae under different cultivation conditions (i.e. CO2, light intensity, cultivation time, and inoculation ratio) for enhanced algal biomass and lipid productivity in wastewater medium using Response SuHhce Methodology (RSM). The results show that mixed cultures ofd7llorella sp. and wastewater wild algae increase biomass and lipid yield. Additionally, findings indicate that CO2, light intensity and cultivation time significantly affect algal productivity. Furthcnnore, CO2 concentration and light intensity, and CO2 concentration and algal composition, have an interactive effect on biomass productivity. Under dii"ferent cultivation conditions, the response of algal biomass, cell count, and lipid productlvlty ranges from2,5 to 10.2 mg/mL 1.1 × 10 to 8.2 × 10 cells/mL and 1.1 × 10^6 to 6.8 × 10^12 total fluorescent units/mL, respectively× The optimum conditions tbr simt, ltaneot, s biomass and lipid accumulation are 3.6% of CO2 (v/v), 160 μmol/m^2/s of light intensity, 1×6/2.4 of inoculation ratio (wastewater-algae/Chlorella), and 8.3 days of cultivation time. The optimal productivity is 9,8 (g/L) for dry biomass, 8.6 E + 08 (cells/mL) for cell count, and 6.8 E + 12 (Total FL units per mL) fbr lipid yield, achieving up to four times, eight times, and seven times higher productivity compared to non- optimized conditions. Provided is a supportive methodology to improve mixed algal culture for hioenergy feedstock generation and to optimize cultivation conditions in complex wastewater environments. This work is an important step tbrward in the development of sustainable large-scale algae cultivation for cost-efficient generation of biofuel.
文摘The production of polyhydroxyalkanoates (PHAs) with a high fraction of 3-hydroxyvalerate (3HV) and 3-hydroxy-2-methylvalerate (3H2/MV) from mixed culture enriched by valerate-dominant hydrolysate was evaluated in this study. After long-term enrichment, the culture showed strong ability to synthesize 3HV and 3H2MV, even with acetate-dominant substrate. The ultilization of single or mixed iso-/n-valerate by the enriched culture showed that the mixture of iso-valerate and n-valerate was more efficient substrate than any single in tenaas of balancing microbial growth and PHAs synthesis. Besides, through comparing the kinetics and stoichiometry of the tests supplying valerate and propionate, the enriched culture with equivalent valerate and propionate (1 : 1 molar ratio) exhibited superior PHAs production performances to pure valerate or propionate, attaining more than 70 tool% of 3HVand 3H2MV. The above findings reveal that valerate-dominant hydrolysate is a kind of suitable substrate to enrich PHAs producing culture with great capability to synthesize 3HV and 3H2MV monomers, thus improving product properties than pure poly(3-hydroxybutyrate) (P3HB); also 3HV and 3H2MV production behaviors can be regulated by the type of odd-carbon VFAs in the substrate.
基金supported by the National Natural Science Foundation of China(No.51378142)the Program for New Century Excellent Talents in University(No.NCET-12-0156)+1 种基金the Open Project of the State Key Laboratory of Urban Water ResourceEnvironment(Harbin institute of Technology)(No.2015DX10)
文摘Four sequence batch reactors(SBRs) fed by fermented sugar cane wastewater were continuously operated under the aerobic dynamic feeding(ADF) mode with different configurations of sludge retention time(SRT), carbon and initial biomass concentrations to enrich polyhydroxyalkanoate(PHA) accumulating mixed microbial cultures(MMCs) from municipal activated sludge.The stability of SBRs was investigated besides the enrichment performance. The microbial community structures of the enriched MMCs were analyzed using terminal restriction fragment length polymorphism(T-RFLP). The optimum operating conditions for the enrichment process were: SRT of 5 days, carbon concentration of 2.52 g COD/L and initial biomass concentration of3.65 g/L. The best enrichment performance in terms of both operating stability and PHA storage ability of enriched cultures(with the maximum PHA content and PHA storage yield(YPHA/S) of61.26% and 0.68 mg COD/mg COD, respectively) was achieved under this condition. Effects of the SRT, carbon concentration and initial biomass concentration on the PHA accumulating MMCs selection process were discussed respectively. A new model including the segmentation of the enrichment process and the effects of SRT on each phase was proposed.
基金the Federal University of Uberlandia,Faculty of Chemical Engineering,Coordination for the Improvement of Higher Education Personnel(CAPES-Brazil),Foundation for Research of the State of Minas Gerais(CRA-APQ-01407-13FAPEMIG-Brazil)National Council for Scientific and Technological Development(CNPq-Brazil)by the research support
文摘Two chromium removal experiments were performed in bioreactors with and without a magnetic field under the same conditions.The release of the chromium present in the biomass was tested in two experiments one with the initial pH of the medium and one with pH 4.0.The objective was to remove Cr(Ⅵ)and total Cr from the effluent,this was carried out by placing biological treatments of synthetic effluent contaminated with 100 mg/L of Cr(Ⅵ)in a bioreactor with neodymium magnets that applied a magnetic field(intensity85.4 mT)to the mixed culture.The removal of Cr(Ⅵ)was approximately 100.0%for the bioreactor with a magnetic field and 93,3%for the bioreactor without a magnetic field for9 hr of recirculation of the synthetic effluent by the bioreactor.The removal of total Cr was61.6%and 48.4%,with and without a magnetic field,respectively;for 24 hr.The desorption of Cr(VI)in the synthetic effluent was 0.05 mg/L,which is below the limit established by Brazilian legislation(0.1 mg/L)for the discharge of effluent containing Cr(Ⅵ)into bodies of water.The results obtained for the removal of chromium in synthetic effluent suggested that there was no significant influence on the viable cell count of the mixed culture.The desorption of Cr(Ⅵ)in synthetic effluent after bioadsorption of chromium by the mixed culture in the process of removal of chromium in bioreactors with and without a magnetic field was not significant in either of the experiments with different initial pHs.
文摘The effect of aeration conditions and pH control on the progress and efficiency of beet molasses vinasse biodegradation was investigated during four batch processes at 38°C with the mixed microbial culture composed of Bifidobacterium,Lactobacillus,Lactococcus,Streptococcus,Bacillus,Rhodopseudomonas,and Saccharomyces.The four processes were carried out in a shake flask with no pH control,an aerobic bioreactor without mixing with no pH control,and a stirred-tank reactor (STR) with aeration with and without pH control,respectively.All experiments were started with an initial pH 8.0.The highest efficiency of biodegradation was achieved through the processes conducted in the STR,where betaine (an organic pollutant occurring in beet molasses in very large quantities) was completely degraded by the microorganisms.The process with no pH control carried out in the STR produced the highest reduction in the following pollution measures:organic matter expressed as chemical oxygen demand determined by the dichromatic method + theoretical COD of betaine (COD sum,85.5%),total organic carbon (TOC,78.8%) and five-day biological oxygen demand (BOD 5,98.6%).The process conditions applied in the shake flask experiments,as well as those used in the aerobic bioreactor without mixing,failed to provide complete betaine assimilation.As a consequence,reduction in COD sum,TOC and BOD 5 was approximately half that obtained with STR.
基金We are grateful for the project grants supported by the Major Science and Technology Programs for Water Pollution Control and Management of China(Nos.2012ZX07205-001 and 2017ZX7103-007).
文摘This study focuses on identifying the factors under which mixed microbial seeds assist bio-chemical denitrification when Scrap Iron Filings(SIF)are used as electron donors and adsorbents in low C/N ratio waters.Batch studies were conducted in abiotic and biotic reactors containing fresh and aged SIF under different dissolved oxygen concentrations with NO_(3)^(-)−N and/or PO_(4)^(3−)influent(s)and their nitrate/phosphate removal and by-product formations were studied.Batch reactors were seeded with a homogenized mixed microbial inoculum procured from natural sludges which were enriched over 6 months under denitrifying conditions in the presence of SIF.Results indicated that when influent containing 40 mg/L of NO_(3)^(-)−N was treated with 5 g SIF,79.9%nitrate reduction was observed in 8 days abiotically and 100%removal was accomplished in 20 days when the reactor was seeded.Both abiotic and seeded reactors removed more than 92%PO_(4)^(3−)under high DO conditions in 12 days.Abiotic and biochemical removal of NO_(3)^(-)−N and abiotic removal of PO_(4)^(3−)were higher under independent NO_(3)^(-)−N/PO_(4)^(3−)loading,while 99%PO_(4)^(3−)was removed biochemically under combined NO_(3)^(-)−N and PO_(4)^(3−)loading.This study furthers the understandings of nitrate and phosphate removal in Zero Valent Iron(ZVI)assisted mixed microbial systems to encourage the application of SIF-supported bio-chemical processes in the simultaneous removals of these pollutants.
文摘Polyhydroxyalkanoates(PHAs)are the polymers of hydroxyalkanoates that accumulate as carbon/energy or reducing-power storage material in various microorganisms.PHAs have attracted considerable attention as biodegradable substitutes for conventional polymers.Until now,however,industrial production of PHAs has encountered only limited success.The main barrier to the replacement of synthetic plastics by PHAs has been the higher cost.The use of mixed cultures and renewable sources obtained from waste organic carbon can substantially decrease the cost of PHA and increase their market potential.This work reviews two main methods of PHA production by mixed cultures,anaerobic-aerobic processing and aerobic transient feeding processing,and analyzed the metabolic and effective factors.
基金support of the National Special S&T Project on the Treatment and Control of Water Pollution of China (No. 2008ZX07313-003)the Science Foundation of Harbin (No. 2007RFLXS013)+1 种基金the State Key Lab of Urban Water Resource and Environment at Harbin Institute of Technology (No. 2010DX02)the National Innovation Team supported by the National Science Foundation of China (No. 50821002)
文摘Two acetate-fed sequencing batch reactors (SBR) were operated under an aerobic dynamic feeding (ADF) model (SBR#2) and with anaerobic phase before aerobic phase (SBR#1) to select mixed cultures with a high polyhydroxyalkanoates (PHA) storage response. Although kinetic selection based on storage response should bring about a predominance of floc-formers, a bulking sludge with storage response comparable to well-settled sludge was steadily established. An anaerobic phase was introduced before the aerobic phase in the ADF model to improve the sludge settleability (SBR #1), however, due to the consequent increased feast/famine ratio, the performance of SBR #1, in terms of both the maximum PHB (polyhydroxybutyrate) cell content and APHB, was lower than that of SBR #2. SBR #2 gradually reached a steady state while SBR #1 failed suddenly after 50 days of operation. The maximum specific substrate uptake rate and storage rate for the selected bulking sludge were 0.4 Cmol Ae/(Cmol X.hr) and 0.18 Cmol Ac/(Cmol PHB.hr), respectively, resulting a yield of 0.45 Cmol PHB/(Cmol Ae) in SBR #2 in the culture enrichment phase. A maximum PHB content of 53% of total suspended solids and PHB storage rate of 1.36 Cmol Ac/(Cmol PHB.hr) was achieved at 10.2 hr in batch accumulation tests under nitrogen starvation. The results indicated that it was feasible to utilize filamentous bacteria to accumulate PHA with a rate comparable to well-settled sludge, Furthermore, the lower dissolved oxygen demand of filamentous bacteria would save energy required for aeration in the culture enrichment stage.
基金the National Natural Science Foundation of China(No.60974068)
文摘In the two-step vitamin C fermentation process, its precursor 2-keto-L-gulonic acid was synthesized from L-sorbose by mixed culture of Gluconobacter oxydans and Bacillus megaterium. The interaction between Gluconobacter oxydans and Bacillus megaterium remains unclear and it is a challenge to mathematically model the mixed growth of these two strains. The Monod-type equations were previously proposed to describe the coupled growth of Gluconobacter oxydans and Bacillus megaterium. However, in this study, we modeled the interaction of these two strains in a macroscopic view by introducing the population theory. Taking account of the fact that the density or concentration of Gluconobacter oxydans or Bacillus megaterium was hardly to measure accurately in the mixed culture broth, the data of concentrations of the substrate and product were used to indirectly investigate the relation between these two strains. Three batch experiments were used to validate our model. And according to the values of identified parameters, the type of interaction between Gluconobacter oxydans and Bacillus megaterium was concluded to be predation, where Gluconobacter oxydans was predator, and Bacillus megaterium was prey.
文摘A continuous fluidized bed bioreactor (FBBR) with nylon support particles was used to treat synthetic sulfide wastewater at different hydraulic retention time of 25, 50 and 75 min and upflow velocity of 14, 17 and 20 m/hr. The effects of upflow velocity, hydraulic retention time and reactor operation time on sulfide oxidation rate were studied using statistical model. Mixed culture obtained from the activated sludge, taken from tannery effluent treatment plant, was used as a source for microorganisms. The diameter and density of the nylon particles were 2-3 mm and 1140 kg/m3, respectively. Experiments were carried out in the reactor at a temperature of (30 ± 2)°C, at a fixed bed height of 16 cm after the formation of biofilm on the surface of support particles. Biofilm thickness reached (42 ± 3) μm after 15 days from reactor start-up. The sulfide oxidation, sulfate and sulfur formation is examined at all hydraulic retention times and upflow velocities. The results indicated that almost 90%-92% sulfide oxidation was achieved at all hydraulic retention times. Statistical model could explain 94% of the variability and analysis of variance showed that upflow velocity and hydraulic retention time slightly affected the sulfide oxidation rate. The highest sulfide oxidation of 92% with 70% sulfur was obtained at hydraulic retention time of 75 min and upflow velocity of 14 m/hr.
基金surpported by National Key Basic Research Program of China(No.CB510008)
文摘The main approach to reduce graft rejection has been focused on the development of immunosuppressive agents at present.Although these strategies have reportedly reduced graft rejection,there has been a reciprocal increase in more severe immunosuppression and lethal infections,as well as severe side effects.Blockade of costimulatory T cell response has been proved as one of useful strategies to reduce graft rejection.Furthermore, it has been shown that infusion of dendritic cells(DCs)with a potent negative regulatory ability for T cells could prolong allograft survival.In this study mouse DCs(mDCs)were transfected with the recombinant plasmid pcDNA3.0 containing mouse inducible costimulator-Ig(mICOS-Ig) cDNA by electroporation.The transient expression of mICOS-Ig in mDC could be detected by ELISA and SDS-PAGE.Mouse ICOS-Ig fusion protein expressed in mDC and mICOS-Ig gene-modified mDC could inhibit lymphocyte proliferation in mixed lymphocyte culture(MLC)in vitro.Furthermore,mICOS-Ig gene-modified mDC could inhibit lymphocyte proliferation in recipient mice.These results suggested that mICOS-Ig gene-modified mDC exerted inhibitory effects on T cells,and might be suitable for treatment or prevention of graft rejection and immunopathologic diseases.Cellular & Molecular Immunology.2004;1(2):153-157.