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  • 1
    Electronic Resource
    Electronic Resource
    Soil layer-specific variability in net nitrification and denitrification in an acid coniferous forest (2000)
    Springer
    Biology and fertility of soils 32 (2000), S. 427-434 
    Details
    ISSN: 1432-0789
    Keywords: Keywords Nitrification ; Denitrification ; Forest soil ; Spatial variation ; Nutrient cycling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  High spatial variation in nitrification potentials has been observed in forest soils, but explanations for this variability have remained speculative. In the present study we determined whether sample treatment, sample size, denitrification or small-scale variations in abiotic properties could explain spatial variation in nitrogen transformations in the organic horizon of a pine forest soil. Net nitrate production in homogenates of the organic horizon was extremely variable. Sample size (60–600 cm2) had no significant effect on nitrate production. In homogenised samples no increased nitrogen production was observed compared to intact incubated cores. High small-scale variation in nitrate production was observed in the litter (L) horizon. When this stratified L layer was subdivided, high net nitrate production was observed in moss (LM) and fragmented needles, whereas no net nitrate production was found in intact needles. The addition of acetylene, inhibiting nitrous oxide reductase, led to significant nitrous oxide production in the L layer. Low nitrous oxide production was found in the LM layer and none in the fragmentation layer. These results show that denitrification can explain part of the spatial variation and plays a major role in nitrogen transformations in the L layer. The relatively higher pH and the presence of fungi are suggested as factors responsible for high denitrification rates in the L layer. As a consequence homogenisation of the organic horizon could lead to highly variable nitrate production due to denitrifying activity from the needles being introduced into other layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740000274
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  • 2
    Electronic Resource
    Electronic Resource
    Construction and physiological characterization of glyceraldehyde-3-phosphate dehydrogenase overproducing transformants of Aspergillus nidulans (1991)
    Springer
    Applied microbiology and biotechnology 34 (1991), S. 765-771 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The construction and characterization of glyceraldehyde-3-phosphate-dehydrogenase (GPD) overproducing transformants of Aspergillus nidulans and their behaviour in acetate-limited continuous cultures and glucose-grown batch cultures are described. The A. nidulans acetamidase deletion strain MH1277 was transormed with the homologous gpdA gene on a vector with the homologous acetamidase-gene (amdS) as a selection marker. Transformant Al contains about nine integrated copies of the gpdA gene, and shows a proportional gene-dosage GPD production of about 22% of the total soluble cell protein. Compared to the wild-type MH1277, Al has higher growth yields and reaches higher specific growth rates on both acetate and glucose, which could be due to the key position of GPD in glycolysis and gluconeogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00169347
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  • 3
    Electronic Resource
    Electronic Resource
    The induction of site 3 phosphorylation in heterotrophically grown Paracoccus denitrificans in the chemostat on mannitol plus methanol (1979)
    Springer
    Antonie van Leeuwenhoek 45 (1979), S. 330-331 
    Details
    ISSN: 1572-9699
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418607
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  • 4
    Electronic Resource
    Electronic Resource
    Modeling of microbial substrate conversion, growth and product formation in a recycling fermentor (1986)
    Springer
    Antonie van Leeuwenhoek 52 (1986), S. 325-342 
    Details
    ISSN: 1572-9699
    Keywords: Growth model ; recycling fermentor ; product formation ; protease ; maintenance ; maximal growth yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Paracoccus denitrificans and Bacillus licheniformis were grown in a carbon- and energy source-limited recycling fermentor with 100% biomass feedback. Experimental data for biomass accumulation and product formation as well as rates of carbon dioxide evolution and oxygen consumption were used in a parameter optimization procedure. This procedure was applied on a model which describes biomass growth as a linear function of the substrate consumption rate and the rate of product formation as a linear function of the biomass growth rate. The fitting procedure yielded two growth domains for P. denitrificans. In the first domain the values for the maximal growth yield and the maintenance coefficient were identical to those found in a series of chemostat experiments. The second domain could be described best with linear biomass increase, which is equal to a constant growth yield. Experimental data of a protease producing B. licheniformis also yielded two growth domains via the fitting procedure. Again, in the first domain, maximal growth yield and maintenance requirements were not significantly different from those derived from a series of chemostat experiments. Domain 2 behaviour was different from that observed with P. denitrificans. Product formation halts and more glucose becomes available for biomass formation, and consequently the specific growth rate increases in the shift from domain 1 to 2. It is concluded that for many industrial production processes, it is important to select organisms on the basis of a low maintenance coefficient and a high basic production of the desired product. It seems less important that the maximal production becomes optimized, which is the basis of most selection procedures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00428644
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  • 5
    Electronic Resource
    Electronic Resource
    Simultaneous NH3 oxidation and N2 production at reduced O2 tensions by sewage sludge subcultured with chemolithotrophic medium (1995)
    Springer
    Biodegradation 6 (1995), S. 339-349 
    Details
    ISSN: 1572-9729
    Keywords: chemolithotrophic nitrification ; denitrification ; oxygen limitation ; activated sludge ; wastewater treatment ; recycling reactor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The ammonia oxidation rate by sewage sludge was determined as a function of the dissolved oxygen tension. Samples of sludge were taken from a domestic waste water treatment pilot plant in which sludge was completely retained by membrane filtration. The samples were subcultured chemolithotrophically in recycling reactors. The gas supplied was a mixture of pure argon and oxygen. The K O2 for ammonia oxidation was estimated to be 0.97 (±0.16) kPa dissolved oxygen. Together with ammonia oxidation and oxygen consumption, dinitrogen gas was produced. So, aerobic denitrification occurred. At dissolved oxygen tensions of 1.25 kPa and higher, the dinitrogen production rate (per N-mole) equalled 20% of the ammonia oxidation rate. This proportion was even 58% at 0.3 kPa dissolved oxygen. At 0.15 kPa dissolved oxygen, however, nitrification hardly proceeded, while dinitrogen production soon stopped. Most likely, a nitrifier concomitantly oxidized ammonia and reduced nitrite to dinitrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00695264
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  • 6
    Electronic Resource
    Electronic Resource
    Consequences of phosphoglycerate kinase overproduction for the growth and physiology of Saccharomyces cerevisiae (1990)
    Springer
    Applied microbiology and biotechnology 32 (1990), S. 577-587 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The physiological consequences of overproduction of the homologous glycolytic enzyme 3-phosphoglycerate kinase (PGK), integrated in 80 PGK1 gene copies in the genome of Saccharomyces cerevisiae are described. This multiple integration and the strong PGK overproduction (maximum 47% of the total soluble cell protein) do not affect the maximal specific growth rate, but cause 40% reduction of the molar growth yield, compared with that of the wild-type host. The extra energy that is needed for protein overproduction is mainly provided by extra fermentation (respirofermentative growth), but respiration is also elevated compared with the reference strains. The increase in the specific oxygen uptake rate indicates that the respiratory capacity of the yeasts is higher than that in the wild-type host, in which the limited capacity of respiration is generally supposed to be at its maximal level at the critical dilution rate, and is thus responsible for the switch to respirofermentative growth. In a medium PGK1 gene copy integrant (about 25 copies), overproduction of 10%–12% PGK has a stimulating effect on the growth yield and energy efficiency. In these cells the growth benefits of overproduction of the glycolytic enzyme are higher than the disadvantages of extra protein synthesis. The overproduction of PGK has also consequences for the glucose affinity of the yeasts: In the more overproducing strain the K s is increased, compared to its reference strains. Elimination of strong overproducing cells from a glucose-limited chemostat culture is caused by two factors: (a) the excision of the PGK genes from the genome, which is of minor importance for wash-out, but the induction process for this overall decline of overproduction, and (b) the physiological selection process for less overproducing cells, caused by differences in affinity for glucose, most obvious at µ ≈ 1/2µmax. However in batch culture and in a chemostat at low specific growth rates, all the overproducing strains show high genetic stability and constantly provide high PGK quantities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00173731
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  • 7
    Electronic Resource
    Electronic Resource
    Growth behaviour and glucoamylase production by Aspergillus niger N402 and a glucoamylase overproducing transformant in recycling culture without a nitrogen source (1995)
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 109-116 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract When wild-type Aspergillus niger N402 and a glucoamylase-overproducing transformant were grown in recycling culture without a nitrogen source, hyphal tip extension and glucoamylase production still occurred, but overproduction of glucoamylase by the transformant strain stopped. The mycelium retained a low metabolic activity. Light micrographs of mycelial samples showed that some hyphae were broken at their tip and partially empty, while after continuing recycling fermentation for more than 500 h many small and empty pieces of broken mycelium could be found. A model has been developed to calculate the mycelial growth and death rates. The mycelial death rate just exceeded the mycelial growth rate and as a consequence the amount of biomass in the fermentor vessel slightly decreased. It is concluded that the cytoplasmic contents of broken mycelial threads were released into the medium and acted as a nitrogen source for the growing parts of the mycelium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170631
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  • 8
    Electronic Resource
    Electronic Resource
    Growth behaviour and glucoamylase production by Aspergillus niger N402 and a glucoamylase overproducing transformant in recycling culture without a nitrogen source (1995)
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 109-116 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  When wild-type Aspergillus niger N402 and a glucoamylase-overproducing transformant were grown in recycling culture without a nitrogen source, hyphal tip extension and glucoamylase production still occurred, but overproduction of glucoamylase by the transformant strain stopped. The mycelium retained a low metabolic activity. Light micrographs of mycelial samples showed that some hyphae were broken at their tip and partially empty, while after continuing recycling fermentation for more than 500 h many small and empty pieces of broken mycelium could be found. A model has been developed to calculate the mycelial growth and death rates. The mycelial death rate just exceeded the mycelial growth rate and as a consequence the amount of biomass in the fermentor vessel slightly decreased. It is concluded that the cytoplasmic contents of broken mycelial threads were released into the medium and acted as a nitrogen source for the growing parts of the mycelium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002530050378
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  • 9
    Electronic Resource
    Electronic Resource
    Growth yields and the efficiency of oxidative phosphorylation of Paracoccus denitrificans during two- (carbon) substrate-limited growth (1979)
    Springer
    Archives of microbiology 121 (1979), S. 213-223 
    Details
    ISSN: 1432-072X
    Keywords: Oxidative phosphorylation ; Chemostat culture ; Growth yield ; Mixed substrates ; Ribulose-bisphosphate cycle ; Cytochrome c ; Single cell protein ; Methanol ; Paracoccus denitrificans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Paracoccus denitrificans was grown aerobically during two-(carbon)substrate-limitation on mannitol and methanol in chemostat cultures. Theoretical growth parameters were calculated based on the presence of 2 or 3 sites in the electron-transport chain of Paracoccus denitrificans. Experimental growth parameters determined during two-(carbon)substrate growth were conform to the presence of 3 sites of oxidative phosphorylation, while cells grown only on mannitol possessed 2 sites. The maximum growth yield on adenosine triphosphate (ATP), corrected for maintenance requirements, determined in chemostat experiments in which the methanol concentration is less than 2.11 times the mannitol concentration was 8.6 g of biomass. When the methanol concentration was more than 2.11 times the mannitol concentration the maximum growth yield on adenosine triphosphate decreased due to the more energy consuming process of CO2-assimilation. Cells use methanol only as energy source to increase the amount of mannitol used for assimilation purposes. When the methanol concentration in chemostat experiments was more than 2.11 times the mannitol concentration, all mannitol was used for assimilation and excess energy derived from methanol was used for CO2-assimilation via the ribulose-bisphosphate cycle. The synthesis of ribulosebisphosphate carboxylase was repressed when the methanol concentration in chemostat experiments was less than 2.11 times the mannitol concentration or when Paracoccus denitrificans was grown in batch culture on both methanol and mannitol. When in chemostat experiments the methanol concentration was more than 2.11 times the mannitol concentration ribulose-bisphosphate carboxylase activity could be demonstrated and CO2-assimilation will occur. It is proposed that energy produced in excess activates or derepresses the synthesis of the necessary enzymes of the ribulose-bisphosphate cycle in Paracoccus denitrificans. Consequently growth on any substrate will be carbonas well as energy-limited. When methanol is present in the nutrient cells of Paracoccus denitrificans synthesize a CO-binding type of cytochrome c, which is essential for methanol oxidase activity. The reason for the increase in efficiency of oxidative phosphorylation from 2 to 3 sites is most probably the occurrence of this CO-binding type of cytochrome c in which presence electrons preferentially pass through the a-type cytochrome region of the electron-transport chain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425058
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  • 10
    Electronic Resource
    Electronic Resource
    Energy conservation during nitrate respiration in Paracoccus denitrificans (1977)
    Springer
    Archives of microbiology 112 (1977), S. 17-23 
    Details
    ISSN: 1432-072X
    Keywords: Oxidative phosphorylation ; Proton translocation ; Continuous culture ; Maintenance energy ; Growth yield ; Nitrate respiration ; Paracoccus denitrificans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract P/2e ratios were calculated from anaerobic chemostat cultures of Paracoccus denitrificans with nitrogenous oxides as electron acceptor. P/2e ratios were calculated, using the Y ATP max values determined for aerobic cultures. When succinate was the carbon and energy source the average P/2e values of the sulphate-and succinate-limited cultures with nitrate as electron acceptor were 0.5 and 0.7, respectively, and of the nitrite-limited culture 0.9. With gluconate as carbon and energy source the average P/2e values of the gluconate-limited with nitrate as electron acceptor and nitrate limited cultures were 0.9 and 1.1, respectively. →H+/O ratios measured in cells obtained from sulphate-, succinate, nitrite-, gluconate-and nitratelimited cultures yielded respective average values of 3.4, 4.5, 3.5, 4.8 and 6.2 for endogenous substrates. From our data we conclude that sulphate-and nitritelimitation causes the loss of site I phosphorylation. Nitrite has no influence on the maximum growth yield on ATP. We propose that metabolism in heterotrophically grown cells of Paracoccus dentrificans is regulated on the level of phosphorylation in the site I region of the electron transport chain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00446649
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