Carbon Substrates (carbon + substrate)

Distribution by Scientific Domains
Distribution within Life Sciences


Selected Abstracts


Microstructure and Thermal Shock Resistance of Molten Glass-Coated Carbon Materials Fabricated by Interfacial Control

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2006
Masashi Wada
Carbon substrates were coated completely with a molten silicate glass, where the wettability of carbon to glass was improved by infiltration and pyrolysis of perhydropolysilazane. Microstructures of the carbon,glass interface were dependent on Pn2 during coating. Coating at lower Pn2 induced the formation of cristobalite at the carbon,glass interface. When the coating was performed at higher Pn2, the glass and carbon were strongly adhered, without the formation of cristobalite. Coating at higher Pn2 improved the thermal shock resistance of the glass layer, because crack initiation was not induced by the phase transformation of cristobalite during the cooling process. In the case of coating at higher Pn2, an oxynitride glass layer was formed at the glass subsurface by dissolution of N2. A porous glass subsurface layer with uniform spherical micro-pores could be produced by soaking near the glass transition temperature in a steam environment. The porous layer with fine and homogeneous microstructure acts as a thermal shock absorbing layer, so that glass-coated carbon with a porous glass layer has excellent thermal shock resistance in addition to steam oxidation resistance. [source]


Calixarene/Nafion-Modified Bismuth-Film Electrodes for Adsorptive Stripping Voltammetric Determination of Lead

ELECTROANALYSIS, Issue 17-18 2009
Ferenc Torma
Abstract This paper presents an enhanced adsorptive stripping voltammetric procedure (AdSV) for the determination of Pb2+, which relies on the accumulation of the metals at a calixarene-based chemically modified bismuth-film electrode on glassy carbon substrate. Following the accumulation of the target metals at open circuit and a medium exchange, both the square wave anodic stripping detection of the metal ions and the in situ bismuth-film formation was performed simultaneously in a Bi3+ containing supporting electrolyte. The analysis of Pb2+ under optimized conditions resulted in stripping responses with good linearity (in the range 0.05,0.6,,M) and precision (RSD=1.12% at 0.2,,M Pb2+; n=10) and low detection limit (0.02,,g/L at 10,min preconcentration). The determination of Pb2+ (0.4,,M) at 100-fold excess of interfering ions (Cd2+, Cu2+ and Zn2+) yielded well resolved lead signal. The analytical utility of the method elaborated was tested in the analysis of trace Pb2+ in environmental water samples. [source]


Isolation and properties of methanesulfonate-degrading Afipia felis from Antarctica and comparison with other strains of A. felis

ENVIRONMENTAL MICROBIOLOGY, Issue 1 2005
S. Azra Moosvi
Summary Three novel strains of methylotrophic Afipia felis were isolated from several locations on Signy Island, Antarctica, and a fourth from estuary sediment from the River Douro, Portugal. They were identified as strains of the ,-2 proteobacterium A. felis by 16S rRNA gene sequence, analysis., Two, strains, tested, were, shown to contain the fdxA gene, diagnostic for A. felis. All strains grew with methanesulfonate (and two strains with dimethylsulfone) as sole carbon substrate. Growth on methanesulfonate required methanesulfonate monooxygenase (MSAMO), using NADH as the reductant and stimulated by reduced flavin nucleotides and Fe(II). Polymerase chain reaction amplification of DNA from an Antarctic strain showed a typical msmA gene for the ,-hydroxylase of MSAMO, and both Antarctic and Portuguese strains contained mxaF, the methanol dehydrogenase large subunit gene. This is the first report of methanesulfonate-degrading bacteria from the Antarctic and of methylotrophy in Afipia, and the first description of any bacterium able to use both methanesulfonate and dimethylsulfone. In contrast, the type strain of A. felis DSM 7326T was not methylotrophic, but grew in defined mineral medium with a wide range of single simple organic substrates. Free-living Afipia strains occurring widely in the natural environment may be significant as methylotrophs, degrading C1 -sulfur compounds, including the recalcitrant organosulfur compound methanesulfonate. [source]


In situ Mixing of Organic Matter Decreases Hydraulic Conductivity of Denitrification Walls in Sand Aquifers

GROUND WATER MONITORING & REMEDIATION, Issue 1 2008
Gregory F. Barkle
In a previous study, a denitrification wall was constructed in a sand aquifer using sawdust as the carbon substrate. Ground water bypassed around this sawdust wall due to reduced hydraulic conductivity. We investigated potential reasons for this by testing two new walls and conducting laboratory studies. The first wall was constructed by mixing aquifer material in situ without substrate addition to investigate the effects of the construction technique (mixed wall). A second, biochip wall, was constructed using coarse wood chips to determine the effect of size of the particles in the amendment on hydraulic conductivity. The aquifer hydraulic conductivity was 35.4 m/d, while in the mixed wall it was 2.8 m/d and in the biochip wall 3.4 m/d. This indicated that the mixing of the aquifer sands below the water table allowed the particles to re-sort themselves into a matrix with a significantly lower hydraulic conductivity than the process that originally formed the aquifer. The addition of a coarser substrate in the biochip wall significantly increased total porosity and decreased bulk density, but hydraulic conductivity remained low compared to the aquifer. Laboratory cores of aquifer sand mixed under dry and wet conditions mimicked the reduction in hydraulic conductivity observed in the field within the mixed wall. The addition of sawdust to the laboratory cores resulted in a significantly higher hydraulic conductivity when mixed dry compared to cores mixed wet. This reduction in the hydraulic conductivity of the sand/sawdust cores mixed under saturated conditions repeated what occurred in the field in the original sawdust wall. This indicated that laboratory investigations can be a useful tool to highlight potential reductions in field hydraulic conductivities that may occur when differing materials are mixed under field conditions. [source]


Bacterial synthesis of poly(hydroxybutyrate- co-hydroxyvalerate) using carbohydrate-rich mahua (Madhuca sp.) flowers

JOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2007
P.K. Anil Kumar
Abstract Aims:, The objective of the present work was to utilize an unrefined natural substrate namely mahua (Madhuca sp.) flowers, as a carbon source for the production of bacterial polyhydroxyalkanoate (PHA) copolymer by Bacillus sp-256. Methods and Results:, In the present work, three bacterial strains were tested for PHA production on mahua flower extract (to impart 20 g l,1 sugar) amongst which, Bacillus sp-256 produced higher concentration of PHA in its biomass (51%) compared with Rhizobium meliloti (31%) or Sphingomonas sp (22%). Biosynthesis of poly(hydroxybutyrate-co-hydroxyvalerate) , P(HB-co-HV) , of 90 : 10 mol% by Bacillus sp-256 was observed by gas chromatographic analysis of the polymer. Major component of the flower is sugars (57% on dry weight basis) and additionally it also contains proteins, vitamins, organic acids and essential oils. The bacterium utilized malic acid present in the substrate as a co-carbon source for the copolymer production. The flowers could be used in the form of aqueous extract or as whole flowers. PHA content of biomass (%) and yield (g l,1) in a 3·0-l stirred tank fermentor after 30 h of fermentation under constant pH (7) and dissolved oxygen content (40%) were 54% and 2·7 g l,1, respectively. Corresponding yields for control fermentation with sucrose as carbon source were 52% and 2·5 g l,1. The polymer was characterized by proton NMR. Conclusions:, Utilization of mahua flowers, a natural substrate for bacterial fermentation aimed at PHA production, had additional advantage, as the sugars and organic acids present in the flowers were metabolized by Bacillus sp-256 to synthesize P(HB-co-HV) copolymer. Significance and Impact of the Study:, Literature reports on utilization of suitable cheaper natural substrate for PHA copolymer production is scanty. Mahua flowers used in the present experiment is a cheaper carbon substrate compared with several commercial substrates and it is rich in main carbon as well as co-carbon sources that can be utilized by bacteria for PHA copolymer production. [source]


Gluconic acid production by Aspergillus terreus

LETTERS IN APPLIED MICROBIOLOGY, Issue 3 2010
C. Dowdells
Abstract Aim:,Aspergillus terreus produces itaconic acid at low pH but lovastatin and other secondary metabolites at higher pH in the fermentation. The utilization of glucose as a carbon substrate was investigated for secondary metabolite production by A. terreus. Methods and Results:, With a starting pH of 6·5, glucose was rapidly metabolized to gluconic acid by the wild-type strain and by transformants harbouring Aspergillus niger genes encoding 6-phosphofructo-1-kinases with superior kinetic and regulatory properties for bioproduction of metabolites from glucose. On exhaustion of the glucose in batch fermentations, the accumulated gluconic acid was utilized as a carbon source. Conclusions:, A novel pathway of glucose catabolism was demonstrated in A. terreus, a species whose wild type is, without any strain development, capable of producing gluconic acid at high molar conversion efficiency (up to 0·7 mol mol,1 glucose consumed). Significance and Impact of the Study:,Aspergillus terreus is a potential novel producer organism for gluconic acid, a compound with many uses as a bulk chemical. With a new knowledge of glucose catabolism by A. terreus, fermentation strategies for secondary metabolite production can be devised with glucose feeding using feedback regulation by pH. [source]


In situ studies of the phylogeny and physiology of filamentous bacteria with attached growth

ENVIRONMENTAL MICROBIOLOGY, Issue 7 2002
Trine Rolighed Thomsen
Summary Among the filamentous bacteria occasionally causing bulking problems in activated sludge treatment plants, three morphotypes with attached microbial growth are common, Eikelboom Type 0041, Type 1851 and Type 1701. A better knowledge of the phylogeny and physiology of these filamentous bacteria is necessary in order to develop control strategies for bulking. In this study we have used a combination of fluorescence in situ hybridization (FISH) and microautoradiography (MAR) to investigate the identity and in situ physiology of the Type 0041-morphotype and its attached bacteria in two wastewater treatment plants. Identification and enumeration of Type 0041 using group-specific 16S rRNA-targeted FISH probes revealed that approximately 15% of the filaments hybridized with a gene probe specific for the TM7 group, a recently recognized major lineage in the bacterial domain. All other filaments morphologically identified as Type 0041 only hybridized to the general bacterial EUB338-probe, indicating that they probably do not belong to commonly isolated bacterial phyla such as the Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes, for which group-specific probes were used. The phylogenetic heterogeneity of Type 0041 again highlights the inadequacy of a morphology-based classification system. Like the filaments, most of the attached microbial cells were not identified beyond their affiliation to the Bacteria using the group-specific FISH probes. However, several different bacterial phyla were represented in the identified fraction suggesting that the attached microorganisms are phylogenetically diverse. The study of the in situ physiology of Type 0041 using MAR-FISH revealed that both the filaments and the attached bacteria on Type 0041 were versatile in the use of organic substrates and electron acceptors. It was observed that all Type 0041 could consume glucose, but none of the filaments were able to consume acetate under any conditions tested, in contrast to some of the attached bacteria. No significant physiological differences were found between TM7,positive and TM7,negative Type 0041 filaments, and only minor differences were observed between the two treatment plants tested. These are the first data on the physiology of the almost entirely uncharacterized TM7 phylum and show that TM7 filamentous bacteria can uptake carbon substrates under aerobic and anaerobic conditions. [source]


Characterization of potential stress responses in ancient Siberian permafrost psychroactive bacteria

FEMS MICROBIOLOGY ECOLOGY, Issue 1 2005
Monica A. Ponder
Abstract Past studies of cold-acclimated bacteria have focused primarily on organisms not capable of sub-zero growth. Siberian permafrost isolates Exiguobacterium sp. 255-15 and Psychrobacter sp. 273-4, which grow at subzero temperatures, were used to study cold-acclimated physiology. Changes in membrane composition and exopolysaccharides were defined as a function of growth at 24, 4 and ,2.5 °C in the presence and absence of 5% NaCl. As expected, there was a decrease in fatty acid saturation and chain length at the colder temperatures and a further decrease in the degree of saturation at higher osmolarity. A shift in carbon source utilization and antibiotic resistance occurred at 4 versus 24 °C growth, perhaps due to changes in the membrane transport. Some carbon substrates were used uniquely at 4 °C and, in general, increased antibiotic sensitivity was observed at 4 °C. All the permafrost strains tested were resistant to long-term freezing (1 year) and were not particularly unique in their UVC tolerance. Most of the tested isolates had moderate ice nucleation activity, and particularly interesting was the fact that the Gram-positive Exiguobacterium showed some soluble ice nucleation activity. In general the features measured suggest that the Siberian organisms have adapted to the conditions of long-term freezing at least for the temperatures of the Kolyma region which are ,10 to ,12 °C where intracellular water is likely not frozen. [source]


Variability in the origin of carbon substrates for bacterial communities in mangrove sediments

FEMS MICROBIOLOGY ECOLOGY, Issue 2 2004
Steven Bouillon
Abstract Organic carbon in mangrove sediments originates from both local sources (mangroves, microphytobenthos) and tidal inputs (e.g. phytoplankton, seagrass-derived material). The relative inputs of these sources may vary strongly, both within and between different mangrove sites. We combined elemental (TOC/TN) and bulk ,13C analysis on sediment cores from various mangrove sites with ,13C data of bacteria-specific phospholipid fatty acids (PLFA) in order to identify the dominant carbon substrates used by in situ bacterial communities. ,13C values of each of these markers showed a range of 10% or more across the different sites and sampling depths, but generally followed the ,13C trend observed in bulk organic carbon. Several sediment cores show a strong vertical gradient in PLFA ,13C, suggesting a selectivity for algal-derived carbon in the surface layers. Our data demonstrate that the origin of bacterial carbon substrates varies widely across different mangrove sites, and imply that data on mineralization of organic matter cannot be directly incorporated in ecosystem carbon budgets without an estimation of the contribution of various sources. [source]


Nanocomposite Hybrid Molecular Materials for Application in Solid-State Electrochemical Supercapacitors,

ADVANCED FUNCTIONAL MATERIALS, Issue 7 2005
K. Cuentas-Gallegos
Abstract Molecular hybrid materials formed from polyoxometalates dispersed in conducting polymers represent an innovative concept in energy storage. This work reports in detail the first practical realization of electrodes based on these materials for energy storage in electrochemical supercapacitors. The molecular hybrids PAni/H4SiW12O40, PAni/H3PW12O40, and PAni/H3PMo12O40 (PAni: polyaniline) have been prepared electrochemically on platinum or carbon substrates, with PAni/H3PMo12O40 being the prototypical example presenting the best energy-storage performance in the series. This hybrid displays the combined activity of its organic and inorganic components to store and release charge in solid-state electrochemical capacitor cells, leading to a promising value of 120,F,g,1 and good cyclability beyond 1000,cycles. [source]


Key Issues Concerning Biolog Use for Aerobic and Anaerobic Freshwater Bacterial Community-Level Physiological Profiling

INTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2006
Bradley W. Christian
Abstract Bacterial heterotrophy in aquatic ecosystems is important in the overall carbon cycle. Biolog MicroPlates provide information into the metabolic potential of bacteria involved in carbon cycling. Specifically, Biolog EcoPlatesÔ were developed with ecologically relevant carbon substrates to allow investigators to measure carbon substrate utilization patterns and develop community-level physiological profiles from natural bacterial assemblages. However, understanding of the functionality of these plates in freshwater research is limited. We explored several issues of EcoPlate use for freshwater bacterial assemblages including inoculum density, incubation temperature, non-bacterial color development, and substrate selectivity. Each of these has various effects on plate interpretation. We offer suggestions and techniques to resolve these interpretation issues. Lastly we propose a technique to allow EcoPlate use in anaerobic freshwater bacterial studies. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Microbial degradation of the detoxification products of mustard from the Russian chemical weapons stockpile

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2005
Inna T Ermakova
Abstract This work was undertaken to examine the possibility of biodegradation of the organic components of the ,reaction masses' (detoxification products) generated by destruction of the chemical warfare agent mustard. The composition of these components was analysed by gas chromatography and mass spectrometry. The major components formed during chemical detoxification were identified as 1,4-perhydrothiazine derivatives. N -(2-Hydroxyethyl)-2-methyl-1,4-perhydrothiazine hydrochloride and N -(2-hydroxyethyl)-3-methyl-1,4-perhydrothiazine hydrochloride were predominant (about 70% of total 1,4-perhydrothiazine derivatives). Pseudomonas putida strains that used some organic components of the mustard reaction masses as carbon sources for growth were isolated and selected. Growth cessation in this medium (with organic carbon still available) was due to the depletion of bioutilisable substrates, primarily monoethanolamine and ethylene glycol (the residual components of the detoxifying mixture). 1,4-Perhydrothiazine derivatives were not used as carbon sources for growth of P putida strain SH1, but their concentration decreased during bacterial growth with monoethanolamine and ethylene glycol as the carbon substrates. It is suggested that 1,4-perhydrothiazines undergo transformation by the microbial cells under these conditions. Copyright © 2005 Society of Chemical Industry [source]


Effective biosynthesis of poly(3-hydoxy- butyrate- co -4-hydroxybutyrate) with high 4-hydroxybutyrate fractions by Wautersia eutropha in the presence of ,-amino acids

POLYMER INTERNATIONAL, Issue 1 2008
Hiroshi Kimura
Abstract BACKGROUND: Biopolymers produced by microbes are in demand as their biodegradable and biocompatible properties make them suitable for disposable products and for potential use as biomaterials for medical applications. The effective microbial production of copolyesters of 3-hydroxybutyrate (3HB) and 4-hydroxybutyrate(4HB) with high molar fractions of 4HB unit by a wild-type Wautersia eutropha H16 was investigated in culture media containing 4-hydroxybutyric acid (4HBA) and different carbon substrates in the presence of various ,-amino acids. RESULTS: The addition of carbon sources such as glucose, fructose and acetic acid to the culture medium containing 4HBA in the presence of ,-amino acids resulted in the production of random poly(3HB- co -4HB) with compositions of up to 77 mol% 4HB unit, but the yields of copolyesters with 60,77 mol% 4HB units were less than 15 wt% of dried cell weights. In contrast, when carbon sources such as propionic acid and butyric acid were used as the co-substrates of 4HBA in the presence of ,-amino acids, poly(3HB- co -4HB) copolyesters with compositions of 72,86 mol% 4HB were produced at maximally 47.2 wt% of dried cell weight (11.3 g L,1) and the molar conversion yield of 4HBA to 4HB fraction in copolyesters was as high as 31.4 mol%. Further, poly(3HB- co -4HB) copolyesters with compositions of 93,96 mol% 4HB were isolated at up to 35.2 wt% of dried cell weights by fractionation of the above copolymers with chloroform/n-hexane. CONCLUSION: The productivity of copolyesters with over 80 mol% 4HB fractions was as high as 0.146 g L,1 h,1 (3.51 g L,1 for 24 h) by flask batch cultivation. Copyright © 2007 Society of Chemical Industry [source]


Effect of carbon source addition on toluene biodegradation by an Escherichia coli DH5, transconjugant harboring the TOL plasmid

BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2010
Kaoru Ikuma
Abstract Horizontal gene transfer (HGT) of plasmids is a naturally occurring phenomenon which could be manipulated for bioremediation applications. Specifically, HGT may prove useful to enhance bioremediation through genetic bioaugmentation. However, because the transfer of a plasmid between donor and recipient cells does not always result in useful functional phenotypes, the conditions under which HGT events result in enhanced degradative capabilities must first be elucidated. The objective of this study was to determine if the addition of alternate carbon substrates could improve toluene degradation in Escherichia coli DH5, transconjugants. The addition of glucose (0.5,5,g/L) and Luria,Bertani (LB) broth (10,100%) resulted in enhanced toluene degradation. On average, the toluene degradation rate increased 14.1 (±2.1)-fold in the presence of glucose while the maximum increase was 18.4 (±1.7)-fold in the presence of 25% LB broth. Gene expression of xyl genes was upregulated in the presence of glucose but not LB broth, which implies different inducing mechanisms by the two types of alternate carbon source. The increased toluene degradation by the addition of glucose or LB broth was persistent over the short-term, suggesting the pulse amendment of an alternative carbon source may be helpful in bioremediation. While the effects of recipient genome GC content and other conditions must still be examined, our results suggest that changes in environmental conditions such as alternate substrate availability may significantly improve the functionality of the transferred phenotypes in HGT and therefore may be an important parameter for genetic bioaugmentation optimization. Biotechnol. Bioeng. 2010;107: 269,277. © 2010 Wiley Periodicals, Inc. [source]


Genome-derived minimal metabolic models for Escherichia coli MG1655 with estimated in vivo respiratory ATP stoichiometry

BIOTECHNOLOGY & BIOENGINEERING, Issue 2 2010
Hilal Taymaz-Nikerel
Abstract Metabolic network models describing growth of Escherichia coli on glucose, glycerol and acetate were derived from a genome scale model of E. coli. One of the uncertainties in the metabolic networks is the exact stoichiometry of energy generating and consuming processes. Accurate estimation of biomass and product yields requires correct information on the ATP stoichiometry. The unknown ATP stoichiometry parameters of the constructed E. coli network were estimated from experimental data of eight different aerobic chemostat experiments carried out with E. coli MG1655, grown at different dilution rates (0.025, 0.05, 0.1, and 0.3,h,1) and on different carbon substrates (glucose, glycerol, and acetate). Proper estimation of the ATP stoichiometry requires proper information on the biomass composition of the organism as well as accurate assessment of net conversion rates under well-defined conditions. For this purpose a growth rate dependent biomass composition was derived, based on measurements and literature data. After incorporation of the growth rate dependent biomass composition in a metabolic network model, an effective P/O ratio of 1.49,±,0.26,mol of ATP/mol of O, KX (growth dependent maintenance) of 0.46,±,0.27,mol of ATP/C-mol of biomass and mATP (growth independent maintenance) of 0.075,±,0.015,mol of ATP/C-mol of biomass/h were estimated using a newly developed Comprehensive Data Reconciliation (CDR) method, assuming that the three energetic parameters were independent of the growth rate and the used substrate. The resulting metabolic network model only requires the specific rate of growth, µ, as an input in order to accurately predict all other fluxes and yields. Biotechnol. Bioeng. 2010;107: 369,381. © 2010 Wiley Periodicals, Inc. [source]


Kinetic characterization of vero cell metabolism in a serum-free batch culture process

BIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010
Emma Petiot
Abstract A global kinetic study of the central metabolism of Vero cells cultivated in a serum-free medium is proposed in the present work. Central metabolism including glycolysis, glutaminolysis, and tricarboxylic acid cycle (TCA) was demonstrated to be saturated by high flow rates of consumption of the two major substrates, glucose, and glutamine. Saturation was reavealed by an accumulation of metabolic intermediates and amino acids, by a high production of lactate needed to balance the redox pathway, and by a low participation of the carbon flow to the TCA cycle supply. Different culture conditions were set up to reduce the central metabolism saturation and to better balance the metabolic flow rates between lactate production and energetic pathways. From these culture conditions, substitutions of glutamine by other carbon sources, which have lower transport rates such as asparagine, or pyruvate in order to shunt the glycolysis pathway, were successful to better balance the central metabolism. As a result, an increase of the cell growth with a concomitant decrease of cell death and a better distribution of the carbon flow between TCA cycle and lactate production occurred. We also demonstrated that glutamine was a major carbon source to supply the TCA cycle in Vero cells and that a reduction of lactate production did not necessary improve the efficiency of the Vero cell metabolism. Thus, to adapt the formulation of the medium to the Vero cell needs, it is important to provide carbon substrates inducing a regulated supply of carbon in the TCA cycle either through the glycolysis or through other pathways such as glutaminolysis. Finally, this study allowed to better understand the Vero cell behavior in serum-free medium which is a valuable help for the implementation of this cell line in serum-free industrial production processes. Biotechnol. Bioeng. 2010;107: 143,153. © 2010 Wiley Periodicals, Inc. [source]