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  • 11
    ISSN: 1573-5176
    Keywords: Quantum yield ; average irradiance ; light absorption ; photobioreactor ; photosynthetic efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth yield of the PUFA-producing marine microalgaIsochrysis galbana ALII-4 grown in a light limited chemostat, was measured under a wide variety of conditions of incident irradiance (I O ) and dilution rates (D). The experiments were conducted under laboratory conditions at 20 °C under continuous light. D ranged from 0.0024 to 0.0410 h−1 at three intensities of Io (820, 1620 and 3270 µmol photon m−2 s−1) close to those found in outdoor cultures. A maximum efficiency Ψ max = 0.616 g mol photon−1 was obtained at I O = 820 µmol photon m−2 s−1 and D = 0.030 h−1 and the maximum capacity of the biomass to metabolize the light harvested was found to be 13.1 µmol photon g−1 s−1. Above this value, a significant drop in the system efficiency was observed. A new approach based in the averaged irradiance is used to assess the photon flux absorbed by the biomass.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 1573-5176
    Keywords: actinometry ; incident photon flux ; photobioreactor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A simple actinometric method was evaluated formeasuring the photosynthetically active incidentphoton flux on outdoor photobioreactors. The method isbased on uranyl sulfate catalyzed photodecompositionof oxalic acid in presence of light. The uranyl–oxalate chemical actinometer absorbs radiation ofwavelengths below 535 nm. In the present work, thephotobioreactor wall material did not transmit lightenergy of wavelengths below 350 nm and the effectiveabsorptivity method was used to evaluate the photonflux between 350–535 nm. The standard solar spectrumof the American Society for Testing and Materials(ASTM) was employed for estimating the ratio betweenthe photosynthetically active radiation (400–700 nm)and the solar radiation in the 350–535 nm range. Thisratio (2.21) was taken to be equal to the quotientbetween the photosynthetically active radiation (PAR)and the incident photon flux on the photobioreactor'ssurface (for the solar radiation between 350–535 nm).PAR measurements with 4π spherical and 2πquantum sensors were used to validate the method.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Journal of applied phycology 12 (2000), S. 355-368 
    ISSN: 1573-5176
    Keywords: light/dark cycles ; microalgae ; Phaeodactylum tricornutum ; photobioreactors, scale-up
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of the light/dark cycle frequency on theproductivity of algal culture at differentday-averaged irradiance conditions was evaluated forPhaeodactylum tricornutum grown in outdoortubular photobioreactors. The photobioreactor scale-upproblem was analyzed by establishing the frequency oflight–dark cycling of cells and ensuring that thecycle frequency remained unchanged on scale-up. Thehydrodynamics and geometry related factors wereidentified for assuring an unchanged light/dark cycle.The light/dark cycle time in two different tubularphotobioreactors was shown to be identical when thelinear culture velocity in the large scale device(U LL) and that in the small scale unit (〉U LS)were related as follows:ULL = \frac f 9/7 \alpha8/7 ULS.Here f is the scale factor (i.e., the ratio oflarge-to-small tube diameters), α is afunction of the illuminated volumes in the tworeactors, and `dark' refers to any zone of the reactorwhere the light intensity is less than the saturationvalue. The above equation was tested in continuouscultures of P. tricornutum in reactors with 0.03 mand 0.06 m diameter tubes, and over the workableculture velocity range of 0.23 to 0.50 m s-1. Thepredicted maximum realistic photobioreactor tubediameter was about 0.10 m for assuring a cultureperformance identical to that in reactors with smaller tubes.
    Type of Medium: Electronic Resource
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  • 14
    ISSN: 1573-6784
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The simultaneous effect of temperature and photon flux density on microalga Chlorella sp. growth was analysed by response surface methodology of two consecutive full factorial designs. Maximum specific growth rate was 0.128 h-1 at 35°C and 2400 μmol photon m-2s-1. A photoinhibition effect was observed at high photon flux densities with temperatures far below the optimum. Temperature was the main factor affecting specific growth rate.
    Type of Medium: Electronic Resource
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