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  • 1
    Electronic Resource
    Electronic Resource
    Cultivation of Marine Sponges (1999)
    Springer
    Marine biotechnology 1 (1999), S. 509-532 
    Details
    ISSN: 1436-2236
    Keywords: Key words: Marine sponge biomass, aquaculture, in vitro culture, cell culture, bioreactor design
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract: There is increasing interest in biotechnological production of marine sponge biomass owing to the discovery of many commercially important secondary metabolites in this group of animals. In this article, different approaches to producing sponge biomass are reviewed, and several factors that possibly influence culture success are evaluated. In situ sponge aquacultures, based on old methods for producing commercial bath sponges, are still the easiest and least expensive way to obtain sponge biomass in bulk. However, success of cultivation with this method strongly depends on the unpredictable and often suboptimal natural environment. Hence, a better-defined production system would be desirable. Some progress has been made with culturing sponges in semicontrolled systems, but these still use unfiltered natural seawater. Cultivation of sponges under completely controlled conditions has remained a problem. When designing an in vitro cultivation method, it is important to determine both qualitatively and quantitatively the nutritional demands of the species that is to be cultured. An adequate supply of food seems to be the key to successful sponge culture. Recently, some progress has been made with sponge cell cultures. The advantage of cell cultures is that they are completely controlled and can easily be manipulated for optimal production of the target metabolites. However, this technique is still in its infancy: a continuous cell line has yet to be established. Axenic cultures of sponge aggregates (primmorphs) may provide an alternative to cell culture. Some sponge metabolites are, in fact, produced by endosymbiotic bacteria or algae that live in the sponge tissue. Only a few of these endosymbionts have been cultivated so far. The biotechnology for the production of sponge metabolites needs further development. Research efforts should be continued to enable commercial exploitation of this valuable natural resource in the near future.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00011807
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  • 2
    Electronic Resource
    Electronic Resource
    Performance of growing Nitrosomonas europaea cells immobilized in κ-carrageenan (1989)
    Springer
    Applied microbiology and biotechnology 32 (1989), S. 108-112 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Nitrosomonas europaea cells were immobilized in κ-carrageenan. The performance of the immobilized cells was investigated in an airlift loop reactor under wash-out conditions with respect to freely suspended cells. When fed with solutions of ammonia up to 16 mM, high substrate conversions were accomplished. Sudden increases in ammonium-ion concentration hardly influenced the conversion. Observations made by scanning electron microscopy showed that the immobilized cells were initially growing homogeneously across the beads, but as growth proceeded, a biomass density gradient developed, eventually resulting in a kind of biofilm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00164831
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  • 3
    Electronic Resource
    Electronic Resource
    Scale-up aspects of photobioreactors: effects of mixing-induced light/dark cycles (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 225-237 
    Details
    ISSN: 1573-5176
    Keywords: microalgae ; Chlamydomonas reinhardtii ; Dunaliellatertiolecta ; light/dark cycles ; photobioreactors ; light utilizationefficiency ; biomass yield ; quantum yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The green micro-algae Chlamydomonas reinhardtiiand Dunaliella tertiolecta were cultivated undermedium-duration square-wave light/dark cycles with acycle time of 15 s. These cycles were used to simulatethe light regime experienced by micro-algae inexternally-illuminated (sunlight) air-lift loopbioreactors with internal draft tube. Biomass yieldin relation to light energy was determined as gprotein per mol of photons (400–700 nm). Between 600and 1200 μmol m-2 s-1 the yield at a10/5 s light/dark cycle was equal to the yield atcontinuous illumination. Consequently, provided thatthe liquid circulation time is 15 s, a considerabledark zone seems to be allowed in the interior ofair-lift loop photobioreactors (33% v/v) without lossof light utilization efficiency. However, at a 5/10 slight/dark cycle, corresponding to a 67% v/v darkzone, biomass yield decreased. Furthermore, bothalgae, C. reinhardtii and D. tertiolecta,responded similarly to these cycles with respect tobiomass yield. This was interesting because they werereported to exhibit a different photoacclimationstrategy. Finally, it was demonstrated that D.tertiolecta was much more efficient at low (average)photon flux densities (57–370 μmol m-2s-1) than at high PFDs (〉 600 μmol m-2s-1) and it was shown that D. tertiolectawas cultivated at a sub-optimal temperature (20 °C).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008151526680
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamics of artificially immobilized Nitrosomonas europaea: Effect of biomass decay (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 630-641 
    Details
    ISSN: 0006-3592
    Keywords: nitrification ; immobilized cells ; Nitrosomonas europaea ; substrate limitation ; biomass death ; staining techniques ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The dynamics of growth and death of immobilized Nitrosomonas europaea were studied. For this, the death rate of suspended cells was determined in the absence of ammonium or oxygen by following the loss of respiration activity and by fluorescein-diacetate (FDA)/lissamine-green staining techniques. The death rates obtained (1.06 × 10-6 s-1 or 4.97 × 10-6 s-1 in the absence of oxygen or ammonium, respectively) were incorporated in a dynamic growth model and the effects on the performance of the immobilized-cell process illustrated by model simulations.These model simulations and experimental validation show that if decay of biomass occurs the biomass concentration in the center of the bead decreases. As a result, the systems react slower to changes in substrate concentrations than if all cells remain viable.To show that cells in the center of the bead died, the FDA and lissamine-green staining techniques were adapted for immobilized cells. It was shown that biomass decay occurred, especially in the center of the bead; the amount of cells decreased there, and the remaining cells were all stained with lissamine green indicating cell death. After the substrate availability was decreased, also cells near the surface of the bead lost their viability. The number of viable cells increased again after increasing the substrate concentration as the result of cell multiplication. At low substrate concentrations and low hydraulic retention times, as for example in the treatment of domestic wastewater, the death rate of cells is thus an important parameter for the performance of the immobilized-cell system. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 630-641, 1997.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Relevance of rheological properties of gel beads for their mechanical stability in bioreactors (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 517-529 
    Details
    ISSN: 0006-3592
    Keywords: immobilized cells ; abrasion ; mechanical stability ; fatigue ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The mechanical stability of biocatalyst particles in bioreactors is of crucial importance for applications of immobilized-cell technology in bioconversions. The common methods for evaluation of the strength of polymer beads (mostly force-to-fracture or tensile tests) are, however, not yet proven to be relevant for the assessment of their mechanical stability in bioreactors. Therefore, we tested fracture properties of gel materials and investigated their relevance for abrasion in bioreactors. Abrasion of gel beads was assumed to be a continuous fracturing of the bead surface. At first, three rheological properties were considered: stress at fracture; strain at fracture; and the total fracture energy. If stress at fracture is the most important property, beads having a similar fracture energy, but a smaller stress at fracture, would abrade faster in a bioreactor than beads with a larger stress at fracture; if fracture energy the determining factor, beads that require less energy to fracture would abrade faster than those having a larger fracture energy for the same fracture stress. To determine this, beads of κ-carrageenan and agar (at two different polymer concentrations) were tested for abrasion in four identical bubble columns under the same operating conditions. Agar beads were expected to abrade faster than those of carrageenan because agar had either a lower stress at fracture or a lower fracture energy. However, no correlation between fracture properties and abrasion rate was found in any of the combinations tested. Carrageenan beads abraded faster than those of agar in all combinations. Furthermore, both the stress and strain at fracture of agar and carrageenan beads decreased during the run and those of carrageenan decreased faster, suggesting that the gels are liable to fatigue in different ways. This hypothesis was confirmed by oscillating experiments in which gel samples were subjected to repeated compressions below their fracture levels. Their resistance to compression clearly decreased with the number of oscillations. Fatigue is probably related to the development of microcracks and microfracture propagation within the material. We concluded that: (a) the use of tests based on bead rupture do not provide relevant information on the mechanical stability of gel beads to abrasion; and (b) abrasion of polymer beads is likely to be related to fatigue of the gel materials. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 517-529, 1997.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
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    Growth of Tetraselmis suecica in a tubular photobioreactor on wastewater from a fish farm (2014)
    Elsevier
    Details
    Publication Date: 2014-11-01
    Print ISSN: 0043-1354
    Electronic ISSN: 1879-2448
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Elsevier
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  • 7
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    Photosynthetic efficiency and oxygen evolution of Chlamydomonas reinhardtii under continuous and flashing light (2012)
    Springer
    Details
    Publication Date: 2012-09-23
    Print ISSN: 0175-7598
    Electronic ISSN: 1432-0614
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Springer
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  • 8
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    Continuous production of Neisseria meningitidis outer membrane vesicles (2019)
    Springer
    Details
    Publication Date: 2019-11-01
    Description: Outer membrane vesicles (OMVs) are nanoparticles secreted by Gram-negative bacteria that can be used for diverse biotechnological applications. Interesting applications have been developed, where OMVs are the basis of drug delivery, enzyme carriers, adjuvants, and vaccines. Historically, OMV research has mainly focused on vaccines. Therefore, current OMV production processes have been based on batch processes. The production of OMVs in batch mode is characterized by relatively low yields and high costs. Transition of OMV production processes from batch to continuous processes could increase the volumetric productivity, reduce the production and capital costs, and result in a higher quality product. Here, we study the continuous production of Neisseria meningitidis OMVs to improve volumetric productivity. Continuous cultivation of N. meningitidis resulted in a steady state with similar high OMV concentrations as are reached in current batch processes. The steady state was reproducible and could be maintained for at least 600 h. The volumetric productivity of a continuous culture reached 4.0 × 1014 OMVs per liter culture per day, based on a dilution rate of 1/day. The tested characteristics of the OMVs did not change during the experiments showing feasibility of a continuous production process for the production of OMVs for any application.
    Print ISSN: 0175-7598
    Electronic ISSN: 1432-0614
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Springer
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  • 9
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    Metabolic characterization of a CHO cell size increase phase in fed-batch cultures (2017)
    Springer
    Details
    Publication Date: 2017-09-26
    Print ISSN: 0175-7598
    Electronic ISSN: 1432-0614
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Springer
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  • 10
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    Dynamics of biomass composition and growth during recovery of nitrogen-starved Chromochloris zofingiensis (2014)
    Springer
    Details
    Publication Date: 2014-11-05
    Print ISSN: 0175-7598
    Electronic ISSN: 1432-0614
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Springer
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