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  • 1
    Electronic Resource
    Electronic Resource
    One carbon metabolism in methanogenic bacteria (1978)
    Springer
    Archives of microbiology 119 (1978), S. 49-57 
    Details
    ISSN: 1432-072X
    Keywords: C1 metabolism ; Methanogenesis ; Methylotrophy ; Methanosarcina Chemolithotrophy ; Autotrophy ; Growth yields ; Dehydrogenase ; Archaebacteria
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two strains of Methanosarcina (M. Barkeri strain MS, isolated from sewage sludge, and strain UBS, isolated from lake sediments) were found to have similar cellular properties and to have DNA base compositions of 44 mol percent guanosine plus cytosine. Strain MS was selected for further studies of its one-carbon metabolism. M. barkeri grew autotrophically via H2 oxidation/CO2 reduction. The optimum temperature for growth and methanogenesis was 37°C. H2 oxidation proceeded via an F420-dependent NADP+-linked hydrogenase. A maximum specific activity of hydrogenase in cell-free extracts, using methyl viologen as electron acceptor, was 6.0 μmol min · mg protein at 37°C and the optimum pH (9.0). M. barkeri also fermented methanol andmethylamine as sole energy sources for growth. Cell yields during growth on H2/CO2 and on methanol were 6.4 and 7.2 mg cell dry weight per mmol CH4 formed, respectively. During mixotrophic growth on H2/CO2 plus methanol, most methane was derived from methanol rather than from CO2. Similar activities of hydrogenase were observed in cell-free extracts from H2/CO2-grown and methanol-grown cells. Methanol oxidation apparently proceeded via carrierbound intermediates, as no methylotrophy-type of methanol dehydrogenase activity was observed in cell-free extracts. During growth on methanol/CO2, up to 48% of the cell carbon was derived from methanol indicating that equivalent amounts of cell carbon were derived from CO2 and from an organic intermediate more reduced than CO2. Cell-free extracts lacked activity for key cell carbon synthesis enzymes of the Calvin cycle, serine path, or hexulose path.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00407927
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  • 2
    Electronic Resource
    Electronic Resource
    Cellulolytic and physiological properties of Clostridium thermocellum (1977)
    Springer
    Archives of microbiology 114 (1977), S. 1-7 
    Details
    ISSN: 1432-072X
    Keywords: Thermophilic ; Anaerobic cellulolytic bacteria ; Clostridium thermocellum ; Cellular growth properties ; Cellulose degradation ; Cellulase (exoglucanase and endoglucanase) production ; Cellulase properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three strains of Clostridium thermocellum obtained from various sources were found to have nearly identical deoxyribonucleic acid guanosine plus cytosine contents that ranged from 38.1–39.5 mole-%. All strain examined fermented only cellulose and cellulose derivatives, but not glucose, or xylose or other sugars. The principal cellulose fermentation products were ethanol, lactate, acetate, hydrogen and carbon dioxide. Growth of C. thermocellum on cellulose resulted in the production of extracellular cellulase that was non-oxygen labile, was thermally stable at 70° C for 45 min and adsorbed strongly on cellulose. Production of cellulase during fermentation correlated linearly with growth and cellulose degradation. Both the yield and specific activity of crude cellulase varied considerably with the specific growth substrates. Highest cellulase yield was obtained when grown on native cellulose, α-cellulose and low degree of polymerization cellulose but not carboxymethylcellulose or other carbohydrate sources. Cellulase activity was not detected when cells were grown on cellobiose. Crude extracellular protein preparations lacked proteolytic and cellobiase activity. The pH and temperafure optima for endoglucanase activity were 5.2 and 65° C, respectively, while that of the exoglucanase activity were 5.4 and 64° C, respectively. The specific activity at 60° c for exoglucanase and endoglucanase of crude cellulase obtained from cells grown on cellulose (MN 300) was 3.6 μmoles reducing sugar equivalents released per h (unit)/mg of protein and 1.5 μmole reducing sugar equivalent released per min (unit)/mg of protein, respectively. The yield of endoglucanase was 125 units per g of cellulose MN 300 degraded and that of exoglucanase was 300 units per g of cellulose MN 300 degraded. Glucose and cellobiose were the hydrolytic end products of crude cellulase action on cellulose, cellotraose and cellotriose in vitro.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00429622
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  • 3
    Electronic Resource
    Electronic Resource
    Acetate metabolism inMethanosarcina barkeri (1978)
    Springer
    Archives of microbiology 119 (1978), S. 175-182 
    Details
    ISSN: 1432-072X
    Keywords: Methanogenesis ; Methylotrophy ; Methanosarcina ; Archaebacteria ; Acetate ; Anaerobes ; Methanogens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Methanosarcina barkeri was grown by acetate fermentation in complex medium (N2 gas phase). The molar growth yield was 1.6–1.9 g cells/mol methane formed. Under these conditions 63–82% of the methane produced byMethanosarcina strains was derived from the methyl carbon of acetate, indicating that some methane was derived from other media components. Growth was not demonstrated in complex media lacking acetate or mineral acetate medium containing acetate but lacking H2/CO2, methanol, or trypticase and yeast extract. Acetate metabolism byM. barkeri strain MS was further exmined in mineral acetate medium containing H2/CO2 and/or methanol, but lacking cysteine. Under these conditions, more methane was derived from the methyl carbon of acetate than from the carboxyl carbon. Methanogenesis from the methyl group increased with increasing acetate concentration. The methyl carbon contributed up to 42% of the methane formed with H2/CO2 and up to 5% with methanol. Methanol stimulated the oxidation of the methyl group of acetate to CO2. The average rates of methane formation from acetate were 1.3 nomol/min ·ml/culture (0.04mg2 cell dry weight) in defined media (gas phase H2/CO2) and complex media (gas phase N2). Acetate contributed up to 60% of cell carbon formed under the growth conditions examined. Similar quantities of cell carbon were derived from the methyl and carboxyl carbons of acetate, suggesting incorporation of this compound as a two-carbon unit. Incorporated acetate was not preferentially localized in lipid material, as 70% of the incorporated acetate was found in the wall and protein cell fractions. Acetate catabolism was stimulated by pregrowing of cultures in media containing acetate, while acetate anabolism was not influenced. The results are discussed in terms of the differences between the mechanisms of acetate catabolism and anabolism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00964270
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  • 4
    Electronic Resource
    Electronic Resource
    Thermophilic anaerobic fermentation of hemicellulose and hemicellulose-derived aldose sugars by Thermoanaerobacter strain B6A (1985)
    Springer
    Archives of microbiology 143 (1985), S. 130-136 
    Details
    ISSN: 1432-072X
    Keywords: Anaerobic fermentation ; Ethanol ; Hemicellulase ; Hemicellulose ; Monosaccharides ; Thermoanaerobacter ; Thermophilic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The thermophilic, anaerobic fermentation of hemicellulosic subtrates by Thermoanaerobacter strain B6A was investigated using a variety of commercially-available hemicelluloses which had been characterized by physical and chemical analysis. Products of hemicellulose fermentation included ethanol, acetic acid, lactic acid, H2, and CO2 in ratios which varied depending on the hemicellulose used. Both the rate and extent of substrate utilization (as estimated from product formation) varied in the order: unidentified mannan/xyloglucan 〉 xylan 〉 4-O-methylglucuronoxylan 〉 arabinoxylan 〉 type II arabinogalactan=0. Rates of product formation were enhanced up to twofold by autoclaving of substrates,which partially depolymerized the substrates and in some cases altered their composition. Total extent of product formation, however, was similar in autoclaved and non-autoclaved substrates. Hemicellulose fermentations were mediated by one or more constitutive extracellular enzyme activities. Component monosaccharides of hemicelluloses in their natural isomeric configurations supported rapid growth (μmax = 0.3−1.0 h−1), while δunnatural” isomers were not utilized.The wide carbohydrate utilization spectrum of this strain apparently reflects its role as a versatile primary consumer in the hot spring bacterial-algal mat from which it was isolated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00411035
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  • 5
    Electronic Resource
    Electronic Resource
    Bacterial methanogenesis: Acetate as a methane precursor in pure culture (1975)
    Springer
    Archives of microbiology 104 (1975), S. 129-134 
    Details
    ISSN: 1432-072X
    Keywords: Methane Bacteria ; Methanosarcina barkeri ; Methanobacterium thermoautotrophicum ; Substrates for Methanogenesis ; Acetate Utilization ; Chemolithotrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pure cultures of methanogenic bacteria were shown to utilize acetate as a methanogenic substrate. In the presence of hydrogen, both Methanosarcina barkeri and Methanobacterium thermoautotrophicum rapidly converted acetate to methane. This reaction was shown to be dependent on the concentration of hydrogen and acetate. In the absence of hydrogen, acetate was not fermented by methane bacteria. Both the methyl and carboxyl position of acetate were reduced to methane. More 14C-methane was detected from methyl than carboxyl-labeled acetate. The utilization of acetate by cultures of M. thermoautotrophicum was enhanced by addition of CO2/HCO3 −. Methyl labeled acetate was shown to be incorporated into whole cells and converted to 14CO2 and 14CH4 in the presence of H2 and 25 mM CO2/HCO3 −. The importance of acetate utilization in microbial methanogenesis was discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00447312
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  • 6
    Electronic Resource
    Electronic Resource
    Purification and characterization of phosphoenolpyruvate carboxykinase from the anaerobic ruminal bacterium Ruminococcus flavefaciens (1997)
    Springer
    Archives of microbiology 167 (1997), S. 289-294 
    Details
    ISSN: 1432-072X
    Keywords: Key words Rumen ; Phosphoenolpyruvate ; Phosphoenolpyruvate carboxykinase ; CO2 fixation ; Ruminococcus flavefaciens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Phosphoenolpyruvate (PEP) carboxykinase was purified 42-fold with a 25% yield from cell extracts of Ruminococcus flavefaciens by ammonium sulfate precipitation, preparative isoelectric focusing, and removal of carrier ampholytes by chromatography. The enzyme had a subunit molecular mass of ∼66.3 kDa (determined by mass spectrometry), but was retained by a filter having a 100-kDa nominal molecular mass cutoff. Optimal activity required activation of the enzyme by Mn2+ and stabilization of the nucleotide substrate by Mg2+. GDP was a more effective phosphoryl acceptor than ADP, while IDP was not utilized. Under optimal conditions the measured activity in the direction of PEP carboxylation was 17.2 μmol min–1 (mg enzyme)–1. The apparent K m values for PEP (0.3 mM) and GDP (2.0 mM) were 9- and 14-fold lower than the apparent K m values for the substrates of the back reaction (oxaloacetate and GTP, respectively). The data are consistent with the involvement of PEP carboxykinase as the primary carboxylation enzyme in the fermentation of cellulose to succinate by this bacterium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002030050446
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  • 7
    Electronic Resource
    Electronic Resource
    Production of caproic acid by cocultures of ruminal cellulolytic bacteria and Clostridium kluyveri grown on cellulose and ethanol (1995)
    Springer
    Applied microbiology and biotechnology 44 (1995), S. 507-513 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Ruminal cellulolytic bacteria (Fibrobacter succinogenes S85 or Ruminococcus flavefaciens FD-1) were combined with the non-ruminal bacterium Clostridium kluyveri and grown together on cellulose and ethanol. Succinate and acetate produced by the cellulolytic organisms were converted to butyrate and caproate only when the culture medium was supplemented with ethanol. Ethanol (244 mM) and butyrate (30 mM at pH 6.8) did not inhibit cellulose digestion or product formation by S85 or FD-1; however caproate (30 mM at pH 6.8) was moderately inhibitory to FD-1. Succinate consumption and caproate production were sensitive to culture pH, with more caproic acid being produced when the culture was controlled at a pH near neutrality. In a representative experiment under conditions of controlled pH (at 6.8) 6.0 g cellulose l-1 and 4.4 g ethanol l-1 were converted to 2.6 g butyrate l-1 and 4.6 g caproate l-1. The results suggest that bacteria that efficiently produce low levels of ethanol and acetate or succinate from cellulose should be useful in cocultures for the production of caproic acid, a potentially useful industrial chemical and bio-fuel precursor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050590
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  • 8
    Electronic Resource
    Electronic Resource
    Production of caproic acid by cocultures of ruminal cellulolytic bacteria and Clostridium kluyveri grown on cellulose and ethanol (1995)
    Springer
    Applied microbiology and biotechnology 44 (1995), S. 507-513 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Ruminal cellulolytic bacteria (Fibrobacter succinogenes S85 or Ruminococcus flavefaciens FD-1) were combined with the non-ruminal bacterium Clostridium kluyveri and grown together on cellulose and ethanol. Succinate and acetate produced by the cellulolytic organisms were converted to butyrate and caproate only when the culture medium was supplemented with ethanol. Ethanol (244 mM) and butyrate (30 mM at pH 6.8) did not inhibit cellulose digestion or product formation by S85 or FD-1; however caproate (30 mM at pH 6.8) was moderately inhibitory to FD-1. Succinate consumption and caproate production were sensitive to culture pH, with more caproic acid being produced when the culture was controlled at a pH near neutrality. In a representative experiment under conditions of controlled pH (at 6.8) 6.0 g cellulose 1−1 and 4.4 g ethanol 1−1 were converted to 2.6 g butyrate 1−1 and 4.6 g caproate 1−1. The results suggest that bacteria that efficiently produce low levels of ethanol and acetate or succinate from cellulose should be useful in cocultures for the production of caproic acid, a potentially useful industrial chemical and bio-fuel precursor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169952
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  • 9
    Electronic Resource
    Electronic Resource
    Automated screening of inhibitors of bacterial dissimilatory sulfate reduction (1991)
    Springer
    Applied microbiology and biotechnology 35 (1991), S. 297-300 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary An automated assay system was used to screen inhibitors of sulfide formation by sulfate-reducing bacteria. The system used a Technicon AutoAnalyzer II instrument both as an incubation chamber (to combine bacterial cells, substrates, and test compounds) and as an analyzer of the amount of sulfide formed during incubation. A lactate-limited chemostat was used to provide a reproducible inoculum of Desulfovibrio desulfuricans cells. The assay was useful in detecting even small changes in the rate of sulfate reduction resulting from exposure to inhibitors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00172715
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  • 10
    Electronic Resource
    Electronic Resource
    Effects of chemical treatments and heating on the crystallinity of celluloses and their implications for evaluating the effect of crystallinity on cellulose biodegradation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 48 (1995), S. 169-178 
    Details
    ISSN: 0006-3592
    Keywords: biopdegradation ; cellulose ; crystallinity ; x-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Chemical treatments similar to those routinely used to extract cellulose from plant biomass caused significant increases in the relative crystallinity index (RCI) of Sig-macell 100 (a commercial cellulose of moderate crystallinity), as measured by x-ray powder diffraction in both the reflectance and transmittance modes. In general, the largest increases in RCI were observed following higher (rather than lower) temperature treatments. Substantial increases in crystalliity were also observed upon resuspension in water prior to drying, with higher temperatures again resulting in the greatest increases in RCI. Measurement of the RCIs of wetted Sigmacell 100 samples by acid hydrolysis kinetics revealed that most of the increased crystallinity occurred rapidly upon contact with water. In contrast to Sigmacell 100, a cellulose of higher initial crystallinity (the microcrystalline cellulose Sigmacell 50) showed little change in crystallinity following the above treatments. The results provide a partial explanation for the inconsistent relationships reported between cellulose crystallinity and cellulose biodegradation. © 1995 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260480211
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