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  • 1990-1994  (3)
  • 1992  (3)
  • 1
    ISSN: 1573-5117
    Keywords: sediment ; ammonium release ; redox conditions ; chlorophyll a derivatives ; bell jar incubations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Sediment-water ammonium fluxes, oxygen uptake and sediment characteristics were studied in an estuarine bay influenced by temporal freshwater discharges. Sediment at seven stations representing a gradient imposed by freshwater inputs was sampled for sediment-water ammonium and oxygen fluxes, chlorophyll a derivative pigments, organic content, porosity and elemental composition (Fe, Mn, Si, Al). Oxygen uptake decreased along the gradient and correlated with total chlorophyll a derivatives indicating the close coupling between aerobic metabolism and short-time sedimentation events. Ammonium release showed a discontinuous pattern of decrease along the gradient and only correlated with the Fe:Mn atomic ratio. Correlation between the structural properties of the sediment (Si:Al atomic ratio, porosity and organic content) and ammonium release was also found (excluding data from the station with the highest ammonium flux). The extent of the influence of metabolism and sediment structure on ammonium release is discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biotechnology letters 14 (1992), S. 1041-1044 
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The influence of pH, temperature, substrate concentration and organic solvents (dimethylformamide, dimethylsulfoxide) on the α-chymotrypsin stability in a water/organic solvent system was studied. The enzyme activity was measured as the dipeptide, AcPheLeuNH2 synthesis and the ester substrate hydrolysis. Enzyme stability was enhanced by lower pH and temperature values and higher substrate concentrations. Dimethylsulfoxide allowed an higher enzyme stability than dimethylformamide. α-Chymotrypsin displayed an higher stability in the water medium when it was compared to the organic system.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-6784
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A novel method to monitor on-line intracellular β-galactosidase activity and biomass simultaneously, using flow injection analysis (FIA), has been developed. The automatic ultrasonic cell disruption and FIA analysis allow the processing of 10 samples/hour with a wide and variable linear working range of β-galactosidase activity and biomass and a maximum relative standard deviation (RSD) of 1.5%. The system has been optimized by monitoring biomass and intracellular β-galactosidase activity inEscherichia coli batch fermentation.
    Type of Medium: Electronic Resource
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