Silicon-based material is an important anode material for next-generation lithium-ion batteries.In order to overcome its shortcomings,carbon coating is often employed to improve the electrochemical performance.However...Silicon-based material is an important anode material for next-generation lithium-ion batteries.In order to overcome its shortcomings,carbon coating is often employed to improve the electrochemical performance.However,the carbon source,carbon content,and different contact and mixing schemes between carbon sources and silicon are all complex factors and need to be clarified.In this study,nano-silicon is coated by the chemical vapor deposition method using different carbon sources,such as acetylene,methane,propane,and propylene.Carbon content after coating is designed to stay at the same level to reduce the experimental error.Results show the sample with higher conductivity provides higher cycle performance.Propylene is the best choice of the four carbon sources studied in this work.These results indicate that the selection of the carbon source is an important factor that plays a significant role in electrochemical performance.展开更多
Direct synthesis of high-quality doped graphene on dielectric substrates without transfer is highly desired for simplified device processing in electronic applications.However,graphene synthesis directly on substrates...Direct synthesis of high-quality doped graphene on dielectric substrates without transfer is highly desired for simplified device processing in electronic applications.However,graphene synthesis directly on substrates suitable for device applications,though highly demanded,remains unattainable and challenging.Here,a simple and transfer-free synthesis of high-quality doped graphene on the dielectric substrate has been developed using a thin Cu layer as the top catalyst and polycyclic aromatic hydrocarbons as both carbon precursors and doping sources.N-doped and N,F-co-doped graphene have been achieved using TPB and F16Cu Pc as solid carbon sources,respectively.The growth conditions were systematically optimized and the as-grown doped graphene were well characterized.The growth strategy provides a controllable transfer-free route for high-quality doped graphene synthesis,which will facilitate the practical applications of graphene.展开更多
The Variscan Bohemian Massif in Central Europe,resulting from continent-continent collision,was long considered a potential UHP terrain due to numerous occurrences of high-pressure granulites,eclogites and
The ability of constructed wetlands with different plants in nitrate removal were investigated. The factors promoting the rates of denitrification including organic carbon, nitrate load, plants in wetlands, pH and wat...The ability of constructed wetlands with different plants in nitrate removal were investigated. The factors promoting the rates of denitrification including organic carbon, nitrate load, plants in wetlands, pH and water temperature in field were systematically investigated. The results showed that the additional carbon source (glucose) can remarkably improve the nitrate removal ability of the constructed wetland. It demonstrated that the nitrate removal rate can increase from 20% to more than 50% in summer and from 10% to 30% in winter, when the nitrate concentration was 30-40 rag/L, the retention time was 24 h and 25 mg/L dissolved organic carbon (DOC) was ploughed into the constructed wetland. However, the nitrite in the constructed wetland accumulated a little with the supply of the additional carbon source in summer and winter, and it increased from 0.15 to 2 mg/L in the effluent. It was also found that the abilities of plant in adjusting pH and temperature can result in an increase of denitrification in wetlands. The seasonal change may also impact the denitrification.展开更多
The flocculating activity of a novel bioflocculant MMF1 produced by multiple-microorganism consortia MM1 was investigated. MM1 was composed of strain BAFRT4 identified as Staphylococcus sp. and strain CYGS1 identified...The flocculating activity of a novel bioflocculant MMF1 produced by multiple-microorganism consortia MM1 was investigated. MM1 was composed of strain BAFRT4 identified as Staphylococcus sp. and strain CYGS1 identified as Pseudomonas sp. The flocculating activity of MMF1 isolated from the screening medium was 82.9%, which is remarkably higher than that of the bioflocculant produced by either of the strains under the same condition. Brewery wastewater was also used as the carbon source for MM1, and the cost-effective production medium for MM1 mainly comprised 1.0 L brewery water (chemical oxygen demand (COD) 5000 mg/L), 0.5 g/L urea, 0.5 g/L yeast extract, and 0.2 g/L (NH4)2SO4. The optimal conditions for the production of MMF1 was inoculum size 2%, initial pH 6.0, cultivating temperature 30℃, and shaking speed 160 r/min, under which the flocculating activity of the MMF1 reached 96.8%. Fifteen grams of purified bioflocculant could be recovered from 1.0 L of fermentation broth. MMF1 was identified as a macromolecular substance containing both protein and polysaccharide. It showed good flocculating performance in treating indigotin printing and dyeing wastewater, and the maximal removal efficiencies of COD and chroma were 79.2% and 86.5%, respectively.展开更多
Organic carbon (OC), total nitrogen (TN), and ^210Pb in core sediment were measured to quantify the burial of organic carbon and the relative importance of allochthonous and autochthonous contributions during the ...Organic carbon (OC), total nitrogen (TN), and ^210Pb in core sediment were measured to quantify the burial of organic carbon and the relative importance of allochthonous and autochthonous contributions during the past one hundred years in Jiaozhou Bay, North China. The core sediment was dated using ^210Pb chronology, which is the most promising method for estimation of sedimentation rate on a time scale of 100-150 years. The variation of the burial flux of organic carbon in the past one hundred years can be divided into the following three stages: (1) relatively steady before 1980s; (2) increasing rapidly from the 1980s to a peak in the 1990s, and (3) decreasing from the 1990s to the present. The change is consistent with the amount of solid waste and sewage emptied into the bay. The OC:TN ratio was used to evaluate the source of organic carbon in the Jiaozhou Bay sediment. In the inner bay and bay mouth, the organic carbon was the main contributor from terrestrial sources, whereas only about half of organic carbon was contributed from terrestrial source in the outer bay. In the inner bay, the terrestrial source of organic carbon showed a steady change with an increase in the range of 69%-77% before 1990 to 93% in 2000, and then decreased from 2000 because of the decrease in the terrestrial input. In the bay mouth, the percentage of organic carbon from land reached the highest value with 94% in 1994. In the outer bay, the sediment source maintained steady for the past one hundred years.展开更多
To investigate the microbial communities of microorganisms cultivated under different carbon sources, three sequencing batch reactors were operated. They were supplied with sewage, glucose and sodium acetate as carbon...To investigate the microbial communities of microorganisms cultivated under different carbon sources, three sequencing batch reactors were operated. They were supplied with sewage, glucose and sodium acetate as carbon sources respectively and showed high phosphorus removal performance. The results of denaturing gradient gel electrophoresis(DGGE) of polymerase chain reaction-amplified(PCR) 16S rDNA fragments demonstrated that β-protebacteria, Actinomyces sp. and γ-protebacteria only exited in 1# reactor. The microbiological diversity of 1# reactor exceeded the other two reactors. Flavobacterium, Bacillales, Actinomyces, Actinobacteridae and uncultured bacteria(AF527584, AF502204, AY592749, AB076862, AJ619051, AF495454 and AY133070) could be detected in the biological phosphorus removal reactors.展开更多
Effect of added carbon source and nitrate concentration on the denitrifying phosphorus removal by DPB sludge was systematically studied using batch experiments, at the same time the variation of ORP was investigated. ...Effect of added carbon source and nitrate concentration on the denitrifying phosphorus removal by DPB sludge was systematically studied using batch experiments, at the same time the variation of ORP was investigated. Results showed that the denitrifying and phosphorus uptake rate in anoxic phase increased with the high initial anaerobic carbon source addition. However once the initial COD concentration reached a certain level, which was in excess to the PHB saturation of poly-P bacteria, residual COD carried over to anoxic phase inhibited the subsequent denitrifying phosphorus uptake. Simultaneously, phosphate uptake continued until all nitrate was removed, following a slow endogenous release of phosphate. High nitrate concentration in anoxic phase increased the initial denitrifying phosphorus rate. Once the nitrate was exhausted, phosphate uptake changed to release. Moreover, the time of this turning point occurred later with the higher nitrate addition. On the other hand, through on-line monitoring the variation of the ORP with different initial COD concentration, it was found ORP could be used as a control parameter for phosphorus release, but it is impossible to utilize ORP for controlling the denitrificaion and anoxic phosphorus uptake operations.展开更多
Acetate, ethanol, and hydrolysed rice were used as external carbon sources in an ammonium removal process employing immobilised bacteria. The influence of the carbon source on the occurrence of free cells and total ni...Acetate, ethanol, and hydrolysed rice were used as external carbon sources in an ammonium removal process employing immobilised bacteria. The influence of the carbon source on the occurrence of free cells and total nitrogen removal efficiency was examined at C/N ratios of 1.5 (low), 2.5 (medium), and 3.5 (high). At the low C/N ratio, no free cells were found in the reactors and the use of acetate as the carbon source resulted in the highest total nitrogen removal efficiency, followed by ethanol and hydrolysed rice. The occurrence of free cells in reactors fed with acetate and ethanol led to a negligible increase in the total nitrogen removal efficiency with increasing C/N ratio. The results suggest that acetate is the most appropriate carbon source for nitrogen removal and that the number of free cells should be minimized to achieve the highest efficiency during long-term operation.展开更多
Biofilms are a constant concern in the food industry;understanding the effect of environmental conditions on biofilm formation is essential to develop effective control strategies.Therefore,this study was conducted to...Biofilms are a constant concern in the food industry;understanding the effect of environmental conditions on biofilm formation is essential to develop effective control strategies.Therefore,this study was conducted to investigate biofilms formation by Staphylococcus epidermidis under various conditions.Biofilms were cultured in nutrient broth containing different carbon source concentrations(0–10 mg/mL)on polystyrene surfaces for 32 h of incubation at 37℃or 55℃,with quantification and enumeration at 8,16,24 and 32 h.S.epidermidis developed biofilms under all tested conditions;achieved the highest yield of biofilm biomass at 2.5 mg/mL for all carbon sources at 37℃.The highest efficiency of extracellular polymeric substance(EPS)molecule production occurred under glucose availability in the growth environment,with a higher yield of biomass and a significantly smaller number of metabolically active cells than under other tested conditions.A condensed ball-shaped structure was observed under the lactose condition.Meanwhile,biofilms in the presence of maltose showed mainly opaque thick rich colonies,while a compact multilayered-shaped structure was exhibited under both glucose and sucrose conditions.These results contribute to a better understanding of the biofilm formation by S.epidermidis in order to reduce contamination and recontamination in the food industry.展开更多
The aim of this research work was to isolate microbes from soil, to investigate their potential use as effective bioremediation tools for trichloroethylene—a potent environmental pollutant. The isolate showing good g...The aim of this research work was to isolate microbes from soil, to investigate their potential use as effective bioremediation tools for trichloroethylene—a potent environmental pollutant. The isolate showing good growth in presence of TCE was named PM102. Microbiological characterisation of the PM102 isolate showed that it was a gram negative rod. Detailed structure was revealed by scanning electron microscopy. pH and temperature optima, salt tolerance and optimum TCE concentration for growth of PM102 were determined. The ability of this bacterium to degrade TCE was studied in acidic and neutral pH by biochemical test and chloride release. Five TCE inducible bands were detected in the protein profile of the isolate as studied by SDS PAGE. A major TCE inducible band of 51.61 kDa was excised from the gel and injected into rabbit to raise specific antibody. The bacterium was identified as Stenotrophomonas maltophilia PM102 by 16S rDNA amplification and sequencing. The 16S rRNA gene sequence has been deposited in the NCBI GenBank with accession number JQ797560. This genus has not been described previously as being capable of TCE degradation. We report for the first time a Stenotrophomonas sp. that grows on TCE as the sole carbon source.展开更多
Early childhood caries (ECC) is a considerable pediatric and public health problem worldwide. Preceding studies have focused primarily on bacterial diversity at the taxonomic level. Although these studies have provi...Early childhood caries (ECC) is a considerable pediatric and public health problem worldwide. Preceding studies have focused primarily on bacterial diversity at the taxonomic level. Although these studies have provided significant information regarding the connection between dental caries and oral micmbiomes, further comprehension of this microbial community's ecological relevance is limited. This study identified the carbon source metabolic differences in dental plaque between children with and without ECC. We compared the microbial community functional diversity in 18 caries-free subjects with 18 severe ECC patients based on sole carbon source usage using a Biolog assay. The anaerobic microbial community in the ECC patients displayed greater metabolic activity than that of the control group. Specific carbon source metabolism differed significantly between the two groups. Subjects from the two groups were well distinguished by cluster and principal component analyses based on discriminative carbon sources. Our results implied that the microbial functional diversity between the ECC patients and healthy subjects differed significantly. In addition, the Biolog assay furthered our understanding of oral microbiomes as a composite of functional abilities, thus enabling us to identify the ecologically relevant functional differences among oral microbial communities.展开更多
Phytopathogenic fungi are heterotrophic organisms that excrete a complex array of enzymes for digestion of plant host tissues. Regulation and coordination of extracellular enzyme production, according to growth condit...Phytopathogenic fungi are heterotrophic organisms that excrete a complex array of enzymes for digestion of plant host tissues. Regulation and coordination of extracellular enzyme production, according to growth conditions and fungus nutritional needs, may be controlled by conserved eukaryotic signaling elements such as G-protein subunits and mitogen-activated protein kinase (MAPK). These pathways are known to mediate a complex set of responses in fungi involved in development, reproduction and pathogenicity. Here, we used a series of mutants, deficient in G-protein α (cga1) or/and β subunits or in MAPK, to test their contribution to the ability of Cochliobolus heterostrophus to utilize different carbon sources. In saprophytic culture, the G-protein α subunit mutant strains had WT levels of cellulase, pectinase and protease degradation activities, but it grew significantly slower on minimal medium containing maltose. This weakened ability implies an essential role of the CGA1 signaling in some poor nutritional environments. Remarkably, the MAPK null mutant failed to achieve the WT (and cga1) growth rate on cellulose as a sole carbon and did not grow at all for the first seven days of culture. An enzymatic activity test revealed that this strain significantly reduced cellulose extracellular degradation activity when grew on this medium. Deficiency in the MAPK encoding gene also led to reduced ability to grow on pectin, protein sources and maltose as a sole carbon. The evidence presented indicates a significant and nutrient-specific role of the G-protein and MAPK pathways in mediating growth of this fungus in different environments.展开更多
Heterotrophic culture of microalgae to develop methods of increasing biomass productivity and storage lipids has brought new insight to commercial biodiesel production.To understand the relationship between heterotrop...Heterotrophic culture of microalgae to develop methods of increasing biomass productivity and storage lipids has brought new insight to commercial biodiesel production.To understand the relationship between heterotrophy and lipid production,the effects of carbon sources on the growth and lipid accumulation of Chlorella sorokiniana GXNN01 was studied.The alga exhibited an increased growth rate in response to the addition of carbon sources,which reached the stationary phase after 48 h at 30°C.In addition,glucose and NaAc had a significant effect on the lipid accumulation during the early-stationary phase.Specifically,the lipid content was 0.237±0.026 g g-1 cell dry weight and 0.272±0.041 g L-1 when glucose was used as the carbon source,whereas the lipid content reached 0.287±0.018 g g-1 cell dry weight and 0.288±0.008 g L-1 when NaAc was used as the carbon source.The neutral lipid content was found to first decrease and then increase over time during the growth phase.A glucose concentration of 20 mmol L-1 gave the maximal lipid yield and the optimum harvest time was the early-stationary phase.展开更多
Rhodobacter sphaeroides is a purple non-sulfur bacterium that belongs to the α-3 subdivision of Proteobacteria. R. sphaeroides is a model bacterial species because of its complex genome structure and expanded metabol...Rhodobacter sphaeroides is a purple non-sulfur bacterium that belongs to the α-3 subdivision of Proteobacteria. R. sphaeroides is a model bacterial species because of its complex genome structure and expanded metabolic capabilities. The genome of R. sphaeroides consists of two circular chromosomes and five endogenous plasmids. It has the ability to grow under a wide variety of environmental conditions. It grows aerobically (~20% O2), semi-aerobically (~2% O2), and photosynthetically (under anaerobic condition plus light). It has been previously shown that many bacterial species utilize a number of alternate carbon sources for their optimal growth under a variety of growth conditions. We hypothesize that different or an additional carbon source in the minimal medium differentially affects the bacterial growth under dark-aerobic conditions. The bacterial growth kinetics and the number of cells in the bacterial culture were analyzed by measuring the optical density (OD at 600 nm) and the colony forming units (CFUs) at regular intervals of bacterial cultures. Results reveal that sodium succinate is the preferred sole carbon source for the optimal growth of R. sphaeroides. The results of growth kinetics and CFUs together concluded that from the tested carbon sources, sodium succinate is the best single carbon source in the minimal media for the optimal growth of R. sphaeroides. Interestingly, cell culture grown in SIS supplemented with sodium acetate exhibits a prolonged lag phase with the lowest ODs and CFUs that later switches to the growth-burst phase support previously discovered similar phenomenon of the growth-rate switch in the presence of acetate metabolism. Future work will utilize the aerobically grown R. sphaeroides’ cells as a biocatalyst to deplete the oxygen levels from natural gas streams and industrial gas pipelines.展开更多
Activated sludge process has been widely used to remove phosphorus and nitrogen from wastewater. However,the nitrogen and phosphorus removal is sometimes unsatisfactory due to the low influent COD.Another problem with...Activated sludge process has been widely used to remove phosphorus and nitrogen from wastewater. However,the nitrogen and phosphorus removal is sometimes unsatisfactory due to the low influent COD.Another problem with the activated sludge process is that large amount of waste activated sludge is produced,which needs further treatment.In this study,the waste activated sludge alkaline fermentation liquid was used as the main carbon source for phosphorus and nitrogen removal under anaerobic followed by alternating aerobic-anoxic conditions,and the results were compared with those using acetic acid as the carbon source.The use of alkaline fermentation liquid not only affected the transformations of phosphorus,nitrogen,intracellular polyhydroxyalkanoates and glycogen, but also led to higher removal efficiencies for phosphorus and nitrogen compared with acetic acid.It was observed that ammonium was completely removed with either alkaline fermentation liquid or acetic acid as the carbon source. However,the former resulted in higher removal efficiencies for phosphorus(95%)and nitrogen(82%),while the latter showed lower ones(87%and 74%,respectively).The presence of a large amount of propionic acid in the alkaline fermentation liquid was one possible reason for its higher phosphorus removal efficiency.Exogenous instead of endogenous denitrification was the main pathway for nitrogen removal with the alkaline fermentation liquid as the carbon source,which was responsible for its higher nitrogen removal efficiency.It seems that the alkaline fermentation liquid can replace acetic acid as the carbon source for phosphorus and nitrogen removal in anaerobic fol- lowed by alternating aerobic-anoxic sequencing batch reactor.展开更多
The effects of different carbon sources(sugars) on the production and molecular properties of exopolysaccharides(EPS) were evaluated in the mycelial liquid culture of a medicinal fungus Cordyceps sinensis Cs-HK1. Gala...The effects of different carbon sources(sugars) on the production and molecular properties of exopolysaccharides(EPS) were evaluated in the mycelial liquid culture of a medicinal fungus Cordyceps sinensis Cs-HK1. Galactose or mannose was used(at 5 g·L^(-1)) as a secondary carbon source with glucose(35 g·L^(-1)) at the mass ratio of 1:7. Mannose was consumed notably since the first day of culture, but galactose was not even after glucose was exhausted.The volumetric yield of EPS in culture was increased slightly with the addition of galactose and decreased with mannose. The monosaccharide composition of EPS was also different, e.g., on day 8, the glucose contents of EPS were 76%with the addition of mannose, 59% with galactose, compared with 62% with glucose only. The molecular weight distribution of EPS was also affected by the secondary carbon source, being generally lower compared with that with glucose only. The results suggested that the addition of galactose improved the total yield of EPS in culture while mannose can improve the yield of glucan constituent of EPS.展开更多
9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide( DOPO)-based flame retardant( DOPO-DOPC) which contains carbon source was used to improve the flame retardancy of poly( ethylene terephthalate)( PET) fabrics. The pr...9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide( DOPO)-based flame retardant( DOPO-DOPC) which contains carbon source was used to improve the flame retardancy of poly( ethylene terephthalate)( PET) fabrics. The prepared DOPODOPC dispersion was applied onto PET fabrics via two kinds of processes,thermosol process and exhaustion process,and in the later using it alone or together with disperse dyes. The flame retardancy of PET fabrics was determined by limiting oxygen index( LOI) and vertical burning test. The results showed that DOPODOPC could obviously improve the flame retardancy of PET fabrics.The PET fabric treated by 60 g/L DOPO-DOPC dispersion via exhaustion process achieved an LOI value of 32. 3%,for example.The flame retardancy and dyeing performances showed that DOPODOPC dispersion could be used together with a part of disperse dyes in one bath. The thermal stability of DOPO-DOPC and the treated PET fabrics were investigated by thermogravimetric analysis( TGA). And the flame retardant mechanism of DOPO-DOPC treated PET fabrics was further investigated by pyrolysis-gas chromatography/mass spectrometry( Py-GC/MS), Fourier transform infrared spectroscopy( FTIR) and scanning electron microscopy( SEM).展开更多
基金Project supported by Beijing Natural Science Foundation(Grant No.2182065)the National Natural Science Foundation of China(Grant No.11922202)。
文摘Silicon-based material is an important anode material for next-generation lithium-ion batteries.In order to overcome its shortcomings,carbon coating is often employed to improve the electrochemical performance.However,the carbon source,carbon content,and different contact and mixing schemes between carbon sources and silicon are all complex factors and need to be clarified.In this study,nano-silicon is coated by the chemical vapor deposition method using different carbon sources,such as acetylene,methane,propane,and propylene.Carbon content after coating is designed to stay at the same level to reduce the experimental error.Results show the sample with higher conductivity provides higher cycle performance.Propylene is the best choice of the four carbon sources studied in this work.These results indicate that the selection of the carbon source is an important factor that plays a significant role in electrochemical performance.
基金supported by Natural Science Foundation of China(NSFC)(Grant No.91333112U1432249)+1 种基金the Priority Academic Program Development of Jiangsu Higher Education Institutionssupported by Collaborative Innovation Center of Suzhou Nano Science&Technology and sponsored by Qing Lan Project
文摘Direct synthesis of high-quality doped graphene on dielectric substrates without transfer is highly desired for simplified device processing in electronic applications.However,graphene synthesis directly on substrates suitable for device applications,though highly demanded,remains unattainable and challenging.Here,a simple and transfer-free synthesis of high-quality doped graphene on the dielectric substrate has been developed using a thin Cu layer as the top catalyst and polycyclic aromatic hydrocarbons as both carbon precursors and doping sources.N-doped and N,F-co-doped graphene have been achieved using TPB and F16Cu Pc as solid carbon sources,respectively.The growth conditions were systematically optimized and the as-grown doped graphene were well characterized.The growth strategy provides a controllable transfer-free route for high-quality doped graphene synthesis,which will facilitate the practical applications of graphene.
文摘The Variscan Bohemian Massif in Central Europe,resulting from continent-continent collision,was long considered a potential UHP terrain due to numerous occurrences of high-pressure granulites,eclogites and
基金supported by the National Key Technologies R&D Program of China (No. 2007BAC22B02)
文摘The ability of constructed wetlands with different plants in nitrate removal were investigated. The factors promoting the rates of denitrification including organic carbon, nitrate load, plants in wetlands, pH and water temperature in field were systematically investigated. The results showed that the additional carbon source (glucose) can remarkably improve the nitrate removal ability of the constructed wetland. It demonstrated that the nitrate removal rate can increase from 20% to more than 50% in summer and from 10% to 30% in winter, when the nitrate concentration was 30-40 rag/L, the retention time was 24 h and 25 mg/L dissolved organic carbon (DOC) was ploughed into the constructed wetland. However, the nitrite in the constructed wetland accumulated a little with the supply of the additional carbon source in summer and winter, and it increased from 0.15 to 2 mg/L in the effluent. It was also found that the abilities of plant in adjusting pH and temperature can result in an increase of denitrification in wetlands. The seasonal change may also impact the denitrification.
基金Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education(No.20050247016)the Program forNew Century Excellent Talents in University(NCET-05-0387).
文摘The flocculating activity of a novel bioflocculant MMF1 produced by multiple-microorganism consortia MM1 was investigated. MM1 was composed of strain BAFRT4 identified as Staphylococcus sp. and strain CYGS1 identified as Pseudomonas sp. The flocculating activity of MMF1 isolated from the screening medium was 82.9%, which is remarkably higher than that of the bioflocculant produced by either of the strains under the same condition. Brewery wastewater was also used as the carbon source for MM1, and the cost-effective production medium for MM1 mainly comprised 1.0 L brewery water (chemical oxygen demand (COD) 5000 mg/L), 0.5 g/L urea, 0.5 g/L yeast extract, and 0.2 g/L (NH4)2SO4. The optimal conditions for the production of MMF1 was inoculum size 2%, initial pH 6.0, cultivating temperature 30℃, and shaking speed 160 r/min, under which the flocculating activity of the MMF1 reached 96.8%. Fifteen grams of purified bioflocculant could be recovered from 1.0 L of fermentation broth. MMF1 was identified as a macromolecular substance containing both protein and polysaccharide. It showed good flocculating performance in treating indigotin printing and dyeing wastewater, and the maximal removal efficiencies of COD and chroma were 79.2% and 86.5%, respectively.
文摘Organic carbon (OC), total nitrogen (TN), and ^210Pb in core sediment were measured to quantify the burial of organic carbon and the relative importance of allochthonous and autochthonous contributions during the past one hundred years in Jiaozhou Bay, North China. The core sediment was dated using ^210Pb chronology, which is the most promising method for estimation of sedimentation rate on a time scale of 100-150 years. The variation of the burial flux of organic carbon in the past one hundred years can be divided into the following three stages: (1) relatively steady before 1980s; (2) increasing rapidly from the 1980s to a peak in the 1990s, and (3) decreasing from the 1990s to the present. The change is consistent with the amount of solid waste and sewage emptied into the bay. The OC:TN ratio was used to evaluate the source of organic carbon in the Jiaozhou Bay sediment. In the inner bay and bay mouth, the organic carbon was the main contributor from terrestrial sources, whereas only about half of organic carbon was contributed from terrestrial source in the outer bay. In the inner bay, the terrestrial source of organic carbon showed a steady change with an increase in the range of 69%-77% before 1990 to 93% in 2000, and then decreased from 2000 because of the decrease in the terrestrial input. In the bay mouth, the percentage of organic carbon from land reached the highest value with 94% in 1994. In the outer bay, the sediment source maintained steady for the past one hundred years.
文摘To investigate the microbial communities of microorganisms cultivated under different carbon sources, three sequencing batch reactors were operated. They were supplied with sewage, glucose and sodium acetate as carbon sources respectively and showed high phosphorus removal performance. The results of denaturing gradient gel electrophoresis(DGGE) of polymerase chain reaction-amplified(PCR) 16S rDNA fragments demonstrated that β-protebacteria, Actinomyces sp. and γ-protebacteria only exited in 1# reactor. The microbiological diversity of 1# reactor exceeded the other two reactors. Flavobacterium, Bacillales, Actinomyces, Actinobacteridae and uncultured bacteria(AF527584, AF502204, AY592749, AB076862, AJ619051, AF495454 and AY133070) could be detected in the biological phosphorus removal reactors.
文摘Effect of added carbon source and nitrate concentration on the denitrifying phosphorus removal by DPB sludge was systematically studied using batch experiments, at the same time the variation of ORP was investigated. Results showed that the denitrifying and phosphorus uptake rate in anoxic phase increased with the high initial anaerobic carbon source addition. However once the initial COD concentration reached a certain level, which was in excess to the PHB saturation of poly-P bacteria, residual COD carried over to anoxic phase inhibited the subsequent denitrifying phosphorus uptake. Simultaneously, phosphate uptake continued until all nitrate was removed, following a slow endogenous release of phosphate. High nitrate concentration in anoxic phase increased the initial denitrifying phosphorus rate. Once the nitrate was exhausted, phosphate uptake changed to release. Moreover, the time of this turning point occurred later with the higher nitrate addition. On the other hand, through on-line monitoring the variation of the ORP with different initial COD concentration, it was found ORP could be used as a control parameter for phosphorus release, but it is impossible to utilize ORP for controlling the denitrificaion and anoxic phosphorus uptake operations.
文摘Acetate, ethanol, and hydrolysed rice were used as external carbon sources in an ammonium removal process employing immobilised bacteria. The influence of the carbon source on the occurrence of free cells and total nitrogen removal efficiency was examined at C/N ratios of 1.5 (low), 2.5 (medium), and 3.5 (high). At the low C/N ratio, no free cells were found in the reactors and the use of acetate as the carbon source resulted in the highest total nitrogen removal efficiency, followed by ethanol and hydrolysed rice. The occurrence of free cells in reactors fed with acetate and ethanol led to a negligible increase in the total nitrogen removal efficiency with increasing C/N ratio. The results suggest that acetate is the most appropriate carbon source for nitrogen removal and that the number of free cells should be minimized to achieve the highest efficiency during long-term operation.
基金This work was financially supported by the National Key Research and Development Program of China(2016YFD0400301)the Key Research and Development Program of Zhejiang Province(2017C02015).
文摘Biofilms are a constant concern in the food industry;understanding the effect of environmental conditions on biofilm formation is essential to develop effective control strategies.Therefore,this study was conducted to investigate biofilms formation by Staphylococcus epidermidis under various conditions.Biofilms were cultured in nutrient broth containing different carbon source concentrations(0–10 mg/mL)on polystyrene surfaces for 32 h of incubation at 37℃or 55℃,with quantification and enumeration at 8,16,24 and 32 h.S.epidermidis developed biofilms under all tested conditions;achieved the highest yield of biofilm biomass at 2.5 mg/mL for all carbon sources at 37℃.The highest efficiency of extracellular polymeric substance(EPS)molecule production occurred under glucose availability in the growth environment,with a higher yield of biomass and a significantly smaller number of metabolically active cells than under other tested conditions.A condensed ball-shaped structure was observed under the lactose condition.Meanwhile,biofilms in the presence of maltose showed mainly opaque thick rich colonies,while a compact multilayered-shaped structure was exhibited under both glucose and sucrose conditions.These results contribute to a better understanding of the biofilm formation by S.epidermidis in order to reduce contamination and recontamination in the food industry.
文摘The aim of this research work was to isolate microbes from soil, to investigate their potential use as effective bioremediation tools for trichloroethylene—a potent environmental pollutant. The isolate showing good growth in presence of TCE was named PM102. Microbiological characterisation of the PM102 isolate showed that it was a gram negative rod. Detailed structure was revealed by scanning electron microscopy. pH and temperature optima, salt tolerance and optimum TCE concentration for growth of PM102 were determined. The ability of this bacterium to degrade TCE was studied in acidic and neutral pH by biochemical test and chloride release. Five TCE inducible bands were detected in the protein profile of the isolate as studied by SDS PAGE. A major TCE inducible band of 51.61 kDa was excised from the gel and injected into rabbit to raise specific antibody. The bacterium was identified as Stenotrophomonas maltophilia PM102 by 16S rDNA amplification and sequencing. The 16S rRNA gene sequence has been deposited in the NCBI GenBank with accession number JQ797560. This genus has not been described previously as being capable of TCE degradation. We report for the first time a Stenotrophomonas sp. that grows on TCE as the sole carbon source.
基金The National Natural Science Foundation of China(81200762 and 81470769)supported this work
文摘Early childhood caries (ECC) is a considerable pediatric and public health problem worldwide. Preceding studies have focused primarily on bacterial diversity at the taxonomic level. Although these studies have provided significant information regarding the connection between dental caries and oral micmbiomes, further comprehension of this microbial community's ecological relevance is limited. This study identified the carbon source metabolic differences in dental plaque between children with and without ECC. We compared the microbial community functional diversity in 18 caries-free subjects with 18 severe ECC patients based on sole carbon source usage using a Biolog assay. The anaerobic microbial community in the ECC patients displayed greater metabolic activity than that of the control group. Specific carbon source metabolism differed significantly between the two groups. Subjects from the two groups were well distinguished by cluster and principal component analyses based on discriminative carbon sources. Our results implied that the microbial functional diversity between the ECC patients and healthy subjects differed significantly. In addition, the Biolog assay furthered our understanding of oral microbiomes as a composite of functional abilities, thus enabling us to identify the ecologically relevant functional differences among oral microbial communities.
文摘Phytopathogenic fungi are heterotrophic organisms that excrete a complex array of enzymes for digestion of plant host tissues. Regulation and coordination of extracellular enzyme production, according to growth conditions and fungus nutritional needs, may be controlled by conserved eukaryotic signaling elements such as G-protein subunits and mitogen-activated protein kinase (MAPK). These pathways are known to mediate a complex set of responses in fungi involved in development, reproduction and pathogenicity. Here, we used a series of mutants, deficient in G-protein α (cga1) or/and β subunits or in MAPK, to test their contribution to the ability of Cochliobolus heterostrophus to utilize different carbon sources. In saprophytic culture, the G-protein α subunit mutant strains had WT levels of cellulase, pectinase and protease degradation activities, but it grew significantly slower on minimal medium containing maltose. This weakened ability implies an essential role of the CGA1 signaling in some poor nutritional environments. Remarkably, the MAPK null mutant failed to achieve the WT (and cga1) growth rate on cellulose as a sole carbon and did not grow at all for the first seven days of culture. An enzymatic activity test revealed that this strain significantly reduced cellulose extracellular degradation activity when grew on this medium. Deficiency in the MAPK encoding gene also led to reduced ability to grow on pectin, protein sources and maltose as a sole carbon. The evidence presented indicates a significant and nutrient-specific role of the G-protein and MAPK pathways in mediating growth of this fungus in different environments.
基金Supported by the National High Technology Research and Development Program of China (863 Program) (No.2006AA05Z112)the Key Project of Science and Technology for Supporting Tianjin Development (No.2007LS700310)the Knowledge Innovation Project of Chinese Academy of Sciences (No.KGCX2-YW-374-3)
文摘Heterotrophic culture of microalgae to develop methods of increasing biomass productivity and storage lipids has brought new insight to commercial biodiesel production.To understand the relationship between heterotrophy and lipid production,the effects of carbon sources on the growth and lipid accumulation of Chlorella sorokiniana GXNN01 was studied.The alga exhibited an increased growth rate in response to the addition of carbon sources,which reached the stationary phase after 48 h at 30°C.In addition,glucose and NaAc had a significant effect on the lipid accumulation during the early-stationary phase.Specifically,the lipid content was 0.237±0.026 g g-1 cell dry weight and 0.272±0.041 g L-1 when glucose was used as the carbon source,whereas the lipid content reached 0.287±0.018 g g-1 cell dry weight and 0.288±0.008 g L-1 when NaAc was used as the carbon source.The neutral lipid content was found to first decrease and then increase over time during the growth phase.A glucose concentration of 20 mmol L-1 gave the maximal lipid yield and the optimum harvest time was the early-stationary phase.
文摘Rhodobacter sphaeroides is a purple non-sulfur bacterium that belongs to the α-3 subdivision of Proteobacteria. R. sphaeroides is a model bacterial species because of its complex genome structure and expanded metabolic capabilities. The genome of R. sphaeroides consists of two circular chromosomes and five endogenous plasmids. It has the ability to grow under a wide variety of environmental conditions. It grows aerobically (~20% O2), semi-aerobically (~2% O2), and photosynthetically (under anaerobic condition plus light). It has been previously shown that many bacterial species utilize a number of alternate carbon sources for their optimal growth under a variety of growth conditions. We hypothesize that different or an additional carbon source in the minimal medium differentially affects the bacterial growth under dark-aerobic conditions. The bacterial growth kinetics and the number of cells in the bacterial culture were analyzed by measuring the optical density (OD at 600 nm) and the colony forming units (CFUs) at regular intervals of bacterial cultures. Results reveal that sodium succinate is the preferred sole carbon source for the optimal growth of R. sphaeroides. The results of growth kinetics and CFUs together concluded that from the tested carbon sources, sodium succinate is the best single carbon source in the minimal media for the optimal growth of R. sphaeroides. Interestingly, cell culture grown in SIS supplemented with sodium acetate exhibits a prolonged lag phase with the lowest ODs and CFUs that later switches to the growth-burst phase support previously discovered similar phenomenon of the growth-rate switch in the presence of acetate metabolism. Future work will utilize the aerobically grown R. sphaeroides’ cells as a biocatalyst to deplete the oxygen levels from natural gas streams and industrial gas pipelines.
基金Supported by the National High Technology Research and Development Program of China(2007AA06Z326)the Programfor New Century Excellent Talents(06-0373)in University
文摘Activated sludge process has been widely used to remove phosphorus and nitrogen from wastewater. However,the nitrogen and phosphorus removal is sometimes unsatisfactory due to the low influent COD.Another problem with the activated sludge process is that large amount of waste activated sludge is produced,which needs further treatment.In this study,the waste activated sludge alkaline fermentation liquid was used as the main carbon source for phosphorus and nitrogen removal under anaerobic followed by alternating aerobic-anoxic conditions,and the results were compared with those using acetic acid as the carbon source.The use of alkaline fermentation liquid not only affected the transformations of phosphorus,nitrogen,intracellular polyhydroxyalkanoates and glycogen, but also led to higher removal efficiencies for phosphorus and nitrogen compared with acetic acid.It was observed that ammonium was completely removed with either alkaline fermentation liquid or acetic acid as the carbon source. However,the former resulted in higher removal efficiencies for phosphorus(95%)and nitrogen(82%),while the latter showed lower ones(87%and 74%,respectively).The presence of a large amount of propionic acid in the alkaline fermentation liquid was one possible reason for its higher phosphorus removal efficiency.Exogenous instead of endogenous denitrification was the main pathway for nitrogen removal with the alkaline fermentation liquid as the carbon source,which was responsible for its higher nitrogen removal efficiency.It seems that the alkaline fermentation liquid can replace acetic acid as the carbon source for phosphorus and nitrogen removal in anaerobic fol- lowed by alternating aerobic-anoxic sequencing batch reactor.
基金Supported by The Hong Kong Polytechnic University internal grants(G-UC14 and G-YBB4)
文摘The effects of different carbon sources(sugars) on the production and molecular properties of exopolysaccharides(EPS) were evaluated in the mycelial liquid culture of a medicinal fungus Cordyceps sinensis Cs-HK1. Galactose or mannose was used(at 5 g·L^(-1)) as a secondary carbon source with glucose(35 g·L^(-1)) at the mass ratio of 1:7. Mannose was consumed notably since the first day of culture, but galactose was not even after glucose was exhausted.The volumetric yield of EPS in culture was increased slightly with the addition of galactose and decreased with mannose. The monosaccharide composition of EPS was also different, e.g., on day 8, the glucose contents of EPS were 76%with the addition of mannose, 59% with galactose, compared with 62% with glucose only. The molecular weight distribution of EPS was also affected by the secondary carbon source, being generally lower compared with that with glucose only. The results suggested that the addition of galactose improved the total yield of EPS in culture while mannose can improve the yield of glucan constituent of EPS.
基金National High Technology Research and Development Program 863 Project,China(No.2013AA06A307)
文摘9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide( DOPO)-based flame retardant( DOPO-DOPC) which contains carbon source was used to improve the flame retardancy of poly( ethylene terephthalate)( PET) fabrics. The prepared DOPODOPC dispersion was applied onto PET fabrics via two kinds of processes,thermosol process and exhaustion process,and in the later using it alone or together with disperse dyes. The flame retardancy of PET fabrics was determined by limiting oxygen index( LOI) and vertical burning test. The results showed that DOPODOPC could obviously improve the flame retardancy of PET fabrics.The PET fabric treated by 60 g/L DOPO-DOPC dispersion via exhaustion process achieved an LOI value of 32. 3%,for example.The flame retardancy and dyeing performances showed that DOPODOPC dispersion could be used together with a part of disperse dyes in one bath. The thermal stability of DOPO-DOPC and the treated PET fabrics were investigated by thermogravimetric analysis( TGA). And the flame retardant mechanism of DOPO-DOPC treated PET fabrics was further investigated by pyrolysis-gas chromatography/mass spectrometry( Py-GC/MS), Fourier transform infrared spectroscopy( FTIR) and scanning electron microscopy( SEM).
基金Supported by the National lqatural Science Foundation of China (31260015), Natural Science Foundation of Qinghai Province (2012-Z-919Q), the Extramural Project from State Key Laboratory for Agrobiotechnology (2012SKLAB06-5) and the Research Funds for Young Project of Qinghal University (2011-QYY-1).