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  • 1
    Electronic Resource
    Electronic Resource
    Cinétique de dégradation des hydrocarbures par Candida lipolytica (1972)
    Springer
    Archives of microbiology 88 (1972), S. 97-109 
    Details
    ISSN: 1432-072X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Le mécanisme d'assimilation des hydrocarbures par une levure, Candida lipolytica est étudié au moyen de l'analyse cinétique de la croissance du microorganisme et de la disparition du substrat hydrocarboné. Les hydrocarbures utilisés sont des n-paraffines. On ajoute au milieu soit un seul hydrocarbure (n-tetradécane ou n-hexadécane), soit un mélange binaire (n-dodécane et n-heptadécane), soit un mélange complexe (du n-undécane au n-octadécane). Contrairement à d'autres auteurs, nous pensons qu'il est peu probable que l'essentiel de la réaction s'effectue par contact des gouttes de substrat et des microorganismes puisque l'on observe des retards d'assimilation de certains hydrocarbures: ceux de faible poids moléculaire (les plus solubles) sont assimilés plus rapidement. Il semble donc que l'assimilation se fasse en grande partie à partir d'hydrocarbures préablement solubilisés.
    Notes: Summary The mechanism of hydrocarbon uptake by a yeast, Candida lipolytica has been studied by means of the kinetic analysis of micro-organism growth and substrate assimilation. Hydrocarbons used as only source of carbon are normal alkanes either pure (n-tetradecane or n-hexadecane) or in mixture of two paraffins (n-dodecane and n-heptadecane) or eight paraffins (n-undecane to n-octadecane). In these last cases delays in n-alkanes consumption are observed. They show that the most soluble substrates (lower molecular weight) are first consumed. In opposition to other authors we think that there is little probability for main reaction occurring by direct contact between drops and micro-organisms. The evidence indicates that n-alkanes are mainly utilized in the dissolved state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00424763
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  • 2
    Electronic Resource
    Electronic Resource
    Influence of pH, lactose and lactic acid on the growth of Streptococcus cremoris: a kinetic study (1988)
    Springer
    Applied microbiology and biotechnology 28 (1988), S. 340-344 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of various culture conditions on growth kinetics of an homofermentative strain of the lactic acid bacterium Streptococcus cremoris were investigated in batch cultures, in order to facilitate the production of this organism as a starter culture for the dairy industry. An optimal pH range of 6.3–6.9 was found and a lactose concentration of 37 g·l-1 was shown to be sufficient to cover the energetic demand for biomass formation, using the recommended medium. The study of the effect of lactic acid concentration on growth kinetics revealed that the end-product was not the sole factor affecting growth. The strain was characterized for its tolerance towards lactic acid and a critical concentration of 70 g·l-1 demonstrated. With the product yield of 0.9 g·g-1 at non-lactose limiting conditions the lactic acid concentration of 33 g·l-1 could not explain the low growth rates obtained, implicating a nutritional limitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00268192
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of various alcoholic supplements on the growth rate of Clostridium acetobutylicum ATCC 824 (1989)
    Springer
    Applied microbiology and biotechnology 31 (1989), S. 179-183 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The inhibitory effect of various alkanols, benzyl alcohol and phenethyl alcohol on the growth rate of Clostridium acetobutylicum ATCC 824 was investigated. Inhibition of cell growth was studied by treating cultures with varied concentrations of alcohols. There was a threshold concentration above which growth inhibition occurred. The degree of inhibition was a linear function of the alcohol concentration used. The natural logarithm of the inhibition constant was shown to be: (1) a linear function of the chain length of the alkanols, (2) a linear function of the natural logarithm of the octanol/water partition coefficient for both aliphatic and cyclic alcohols.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262459
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  • 4
    Electronic Resource
    Electronic Resource
    A tentative physiological model of batch acetonobutylic fermentation (1992)
    Springer
    Applied microbiology and biotechnology 37 (1992), S. 714-717 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A mathematical model of batch acetonobutylic fermentation under glucose limitation is proposed. Making use of available information on the physiology of the process this model correctly predicts the two phases of growth and product formation observed at low extracellular pH, with production of butanol and acetone predominating in the final stage and butyrate and acetate production predominating at more neutral pH. A fair agreement between the prediction and experiments performed in different laboratories at different substrate concentrations and pH was achieved.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00174833
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of various reducing agents on methylotrophic growth and organic acid production of Eubacterium limosum (1989)
    Springer
    Applied microbiology and biotechnology 32 (1989), S. 193-198 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Batch and continuous fermentations of methanol/CO2 by the acidogenic Eubacterium limosum were modified with respect to growth and production of organic acids by the choice of reducing agent. Titanium (III) citrate enhanced the maximum specific growth rate (μmax) and the yield of butyrate at the expense of acetate, whilst Na2S was toxic but able to provoke homobutyric fermentations. In general, the lower the redox potential prior to inoculation the higher the CO2 consumption though not to the detriment of butyrate synthesis. It would seen likely that the redox potential of the culture medium plays a role in either maintaining a high level of reduced co-enzymes and/or altering the relative contribution of the proton (ΔpH) and ionic (Δψ) gradients to the proton motive force, in such a way that butyrate production is favoured.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00165887
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  • 6
    Electronic Resource
    Electronic Resource
    Lipid production by an unsaturated fatty acid auxotroph of the oleaginous yeast Apiotrichum curvatum grown in single-stage continuous culture (1993)
    Springer
    Applied microbiology and biotechnology 40 (1993), S. 483-488 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract An unsaturated fatty acid auxotroph of the oleaginous yeast Apiotrichum curvatum, named UfaM3, blocked in the conversion of stearic to oleic acid was cultivated in single-stage continuous culture. The influence of consumed carbon to nitrogen ratios (C/N ratios, g g−1) obtained at various dilution rates (D) on fatty acid (FA) accumulation and its profiles were studied. In continuous culture in N-limited medium a maximum FA accumulation of 45.6% (g g−1 of dry biomass) was obtained at an optimal D of 0.049 h−1, recording an efficiency of substrate conversion of 0.48 g g−1 and 0.22 g g−1 for biomass and lipids, respectively. The quality of lipid approached cocoa butter at an optimal C/N ratio of between 20 and 30. The C/N ratio in the incoming medium was 38.5 g g−1 with 30 g l−1 of glucose and both C and N sources were completely consumed at a critical D of ≤ 0.07 h−1. The stability of the mutant was demonstrated in the steady-state conditions of the chemostat with regard to the FA composition of its lipids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00175735
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  • 7
    Electronic Resource
    Electronic Resource
    Survival of alginate-entrapped cells of Azospirillum lipoferum during dehydration and storage in relation to water properties (1993)
    Springer
    Applied microbiology and biotechnology 40 (1993), S. 34-39 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Survival of alginate-entrapped cells of Azospirillum lipoferum was studied during dehydration using a dry air stream and during prolonged storage at various constant water activity values (aw). During the drying operation, the viability loss remained almost constant from the initial water content to 0.35 g water/g dry weight (DW) corresponding to a 98.5% water removal, strongly increased until a water content of 0.25 g/g DW and then stopped until the end of the drying operational (final aw 0.18). A water content of 0.25 g/g DW (aw=0.55) corresponded to the critical point of the moisture sorption isotherm curve from which water became restricted to the dry material. A high drying rate (5 g/g DW per hour) was shown to be more detrimental for cell viability than a low drying rate (1.18 g/g DW per hour). When the product was stored in a closed chamber with a regulated aw (0.23), the number of living cells decreased during a short period (less than 15 days) corresponding to the product aw stabilization, and then remained constant for more than 150 days. In addition, cell survival during storage was not affected by aw values in the range 0–0.55. Above aw=0.55, the higher the aw and the storage duration, the lower the residual survival percentage. The influence of the drying and storage conditions on the cell death rate are discussed with regard to both the mechanisms generally involved in viability loss and the hydration properties of water.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00170425
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  • 8
    Electronic Resource
    Electronic Resource
    Hydrocarbon fermentation: Kinetics of microbial cell growth (1978)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 20 (1978), S. 1723-1734 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Modeling of microbial growth using nonmiscible substrate is studied when kinetics of substrate dissolution is rate limiting. When the substrate concentration is low, the growth rate is described by an analytical relation that can be identified as a Contois relationship. If the substrate concentration is greater than a critical value Scrit, the potentially useful hydrocarbon S* concentration is described by S* = Scrit/(1 + Scrit/S). A relationship was found between Scrit and the biomass concentration X. When X increased, Scrit decreased. The cell growth rate is related to a relation μ = μm[A(X/Scrit)(1 + Scrit/S) + 1]-1. This model describes the evolution of the growth rate when exponential or linear growth occurs, which is related to physico-chemical properties and hydrodynamic fermentation conditions. Experimental data to support the model are presented.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260201104
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of anaerobic microbial culture with high acidogenic activity (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 23 (1981), S. 185-199 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The mixed cultures which were used were isolated from municipal sludge digesters, and the production of organic acids (acetic, propionic, butyric, etc.) from carbohydrates was tested. The behavior of the reference population (culture R) obtained directly from the sewage treatment plant, is compared to that obtained after three months in a plug-flow reactor (Gradostat fermentor) without pH control (culture A) and after six months with pH control (culture B). For culture B, the specific rate of acid production is related to the cell growth rate by (1/X)rp= 17 µ + 1.6 with a maximal acid concentration of 40 g/liter. The batch culture yields are improved from 0.36g/g for the initial culture (R) to 0.72 g/g for culture B after six months in continuous culture, and 0.8 g/g in plug-flow continuous culture. The productivity of organic acids reaches 1.7 g/liter·hr. It is suggested that the acidogenic fermentation, the first step of methanogenesis, is a potential process to produce acetic, propionic, and butyric acids.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260230112
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  • 10
    Electronic Resource
    Electronic Resource
    Modelling ethanol and secondary inhibitions of ethanol fermentation in a multistage reactor (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 32 (1988), S. 271-276 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A kinetic model of ethanol fermentation conducted under a variety of conditions in a continuous four-stage reactor is proposed. The expressions for specific growth and product formation rates are: \documentclass{article}\pagestyle{empty}\begin{document}$$ \mu = \mu _0 {\rm exp( - }k_1 P){\rm (1 - }X/X_1) \\ \nu _P = \nu _0 {\rm exp( - }k_2 P){\rm (1 - }X/X_2) \\ $$\end{document} Parameters were identified by nonlinear programming and shown to fit data correctly for steady states of seven different experiments. The product inhibition constants were of 27 and 84 g/L, respectively. Secondary inhibitions were represented by the linear biomass term. The proposed model gave a better description of phenomena than one which only took ethanol inhibition into account. The same model also fitted batch fermentation data, with only some parameters altering significantly. The use of this model for on-line purposes is discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260320303
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