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  • 1
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Acetone-butanol fermentation of the Jerusalem artichoke has been studied as a case for systematic investigation of the industrial optimization of both strain selection and fermentation operation. Hydrolysis of the inulinic oligofructans of the substrate was found necessary for optimal performance but could be achieved with a selected strain using a moderate amount of inulinase added at the beginning of the fermentation. Apart from ammonia, no nutritional supplementation of the medium was found necessary. The marked influence of pH in the fermentation performance prompted a detailed search for a method of controlling pH during fermentation. With an optimized procedure, solvent production of 23–24 g/l were obtained in 36 h. Detailed fermentation balances are presented. An industrial process for ABE production from Jerusalem artichoke or sugar beet has been defined and tested in the pilot plant.
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  • 2
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  The mechanism of phenanthrene transfer to the bacteria during biodegradation by a Pseudomonas strain was investigated using a sensitive respirometric technique (Sapromat equipment) allowing the quasi-continuous acquisition of data on oxygen consumption. Several systems of phenanthrene supply, crystalline solid and solutions in non-water-miscible solvents (silicone oil and 2,2,4,4,6,8,8-heptamethylnonane) were studied. In all cases, analysis of the kinetics of oxygen consumption demonstrated an initial phase of exponential growth with the same specific growth rate. In order to analyze the second phase of growth and phenanthrene degradation, a study of the kinetics of phenanthrene transfer to the aqueous phase was conducted by direct experimentation, with the crystal and silicone oil systems, in abiotic conditions. The data allowed the validation of a model based on phase-transfer laws, describing the variations, with substrate concentrations, of rates of phenanthrene transfer to the aqueous phase. Analysis of the biodegradation curves then showed that exponential growth ended in all cases when the rates of phenanthrene consumption reached the maximal transfer rates. Thereafter, the biodegradation rates closely obeyed, for all systems, the transfer rate values given by the model. These results unambiguously demonstrated that, in the present case, phenanthrene biodegradation required prior transfer to the aqueous phase. With the silicone oil system, which allowed high transfer and biodegradation rates, phenanthrene was directed towards higher metabolite production and lower mineralization, as shown by oxygen consumption and carbon balance determinations.
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  • 3
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Acetone-butanol fermentation of the Jerusalem artichoke has been studied as a case for systematic investigation of the industrial optimization of both strain selection and fermentation operation. Hydrolysis of the inulinic oligofructans of the substrate was found necessary for optimal performance but could be achieved with a selected strain using a moderate amount of inulinase added at the beginning of the fermentation. Apart from ammonia, no nutritional supplementation of the medium was found necessary. The marked influence of pH in the fermentation performance prompted a detailed search for a method of controlling pH during fermentation. With an optimized procedure, solvent production of 23–24 g/l were obtained in 36 h. Detailed fermentation balances are presented. An industrial process for ABE production from Jerusalem artichoke or sugar beet has been defined and tested in the pilot plant.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Two physiological characteristics of butyric fermentation, inhibition by the acids produced, butyrate and acetate, and dependence on the growth rate of the distribution of these acids, prompted a study of butyrate production in a continuous fermentation system with cell recycle by microfiltration. The influence of the main operating parameters, glucose input (feed concentration and dilution rate) and bleed dilution rate on production of acids and biomass was studied. The performance of the system greatly exceeded the results obtained in batch and simple continuous fermentations as a high productivity for butyrate (9.5 g l−1 h−1) was achieved whilst retaining a satisfactory concentration of butyrate (29.7 g l−1) and low acetate production (0.6 g l−1) at a cell biomass concentration of 35 g l−1. Cell growth rate was found to be a critical parameter for performance stability as oscillations in metabolic activity due to inhibition by acids were observed at bleed dilution rates below 0.016 h−1.
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  • 5
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Six bacterial strains capable of using, as sole carbon and energy source, at least one of the following polycyclic aromatic hydrocarbons (PAH), naphthalene, fluorene, phenanthrene, anthracene, fluoranthene and pyrene, were isolated. The interactions between these PAH during their biodegradation were studied in experiments involving PAH pairs, one PAH at least being used as a carbon source. All individual strains were found capable of cometabolic degradation of PAH in a range varying among strains. Inhibition phenomena, sometimes drastic, were often observed but synergistic interactions were also detected. Naphthalene was toxic to all strains not isolated on this compound. Strain associations were found efficient in relieving inhibition phenomena, including the toxic effect of naphthalene. Accumulation of water-soluble metabolites was consistently observed during PAH degradation.
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  • 6
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The mechanism of phenanthrene transfer to the bacteria during biodegradation by aPseudomonas strain was investigated using a sensitive respirometric technique (Sapromat equipment) allowing the quasi-continuous acquisition of data on oxygen consumption. Several systems of phenanthrene supply, crystalline solid and solutions in non-water-miscible solvents (silicone oil and 2,2,4,4,6,8,8-heptamethylnonane) were studied. In all cases, analysis of the kinetics of oxygen consumption demonstrated an initial phase of exponential growth with the same specific growth rate. In order to analyze the second phase of growth and phenanthrene degradation, a study of the kinetics of phenanthrene transfer to the aqueous phase was conducted by direct experimentation, with the crystal and silicone oil systems, in abiotic conditions. The data allowed the validation of a model based on phase-transfer laws, describing the variations, with substrate concentrations, of rates of phenanthrene transfer to the aqueous phase. Analysis of the biodegradation curves then showed that exponential growth ended in all cases when the rates of phenanthrene consumption reached the maximal transfer rates. Thereafter, the biodegradation rates closely obeyed, for all systems, the transfer rate values given by the model. These results unambiguously demonstrated that, in the present case, phenanthrene biodegradation required prior transfer to the aqueous phase. With the silicone oil system, which allowed high transfer and biodegradation rates, phenanthrene was directed towards higher metabolite production and lower mineralization, as shown by oxygen consumption and carbon balance determinations.
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  • 7
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Sophorose lipid production by Candida bombicola is a two-step process where sophorose lipids are mainly produced after a first stage of growth, ending because of nitrogen limitation. The influence of the following parameters was individually studied for both the stages of growth and of product formation with respect to final sophorose lipid production performance: pH, temperature and carbon source. Glucose and rapeseed ethyl esters were supplied individually or as a dual carbon source. The lipidic substrate was added by continuous feeding. It was found that supplying both carbon sources during the production step was crucial for obtaining a high production performance ranging from 250 g l−1 to 300 g l−1 or more. Controlling the feeding of rapeseed ethyl esters to avoid inhibition by fatty acids was essential for a successful scale-up of the fermentation on the industrial scale. The conditions of substrate feeding markedly affected the composition of the mixture of sophorose lipids produced, namely the extent of acetylation of the sophorose moieties and distribution of the acidic and lactonic forms. The results suggest that the physiological role of sophorose lipid production is related to the regulation of energy metabolism.
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  • 8
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The biodegradability under aerobic conditions of volatile hydrocarbons (4–6 carbons) contained in gasoline and consisting of n-alkanes, iso-alkanes, cycloalkanes and alkenes, was investigated. Activated sludge was used as the reference microflora. The biodegradation test involved the degradation of the volatile fraction of gasoline in closed flasks under optimal conditions. The kinetics of biodegradation was monitored by CO2 production. Final degradation was determined by gas chromatographic analysis of all measurable hydrocarbons (12 compounds) in the mixture after sampling the headspace of the flasks. The degradation of individual hydrocarbons was also studied with the same methodology. When incubated individually, all hydrocarbons used as carbon sources, except 2,2-dimethylbutane and 2,3-dimethylbutane, were completely consumed in 30 days or less with different velocities and initial lag periods. When incubated together as constituents of the light gasoline fraction, all hydrocarbons were metabolised, often with higher velocities than for individual compounds. Cometabolism was involved in the degradation of dimethyl isoalkanes.
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  • 9
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Enzymatic production of L-tryptophan has been studied in a system containing Escherichia coli cells (induced for tryptophanase) entrapped in a polyacrylamide gel, indole and excess pyruvate and ammonia. The influence of pH, substrate concentration and temperature on L-tryptophan production, in batch and flow reactor conditions, was investigated. In flow reactor conditions, inhibition of the reaction by indole resulted in a multi steady-state pattern characteristic of substrate inhibited reactions. Any increase in flow rate at indole concentrations higher than 17 mM resulted in a dramatic decrease in the conversion rate of indole to tryptophan. A device for the practical production of L-tryptophan, which involves feeding a limiting concentration of indole to a reactor, adsorption of the synthetized tryptophan and recycling of excess pyruvate and ammonium ions was tested.
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  • 10
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The β-fructofuranosidase activities of a strain of Clostridium acetobutylicum, selected for its capacity to grow on inulinic substrates, were investigated. When grown on inulin, this strain produced extracellular and intracellular β-fructofuranosidases, both of which hydrolysed inulin (inulinase activity) and sucrose (invertase activity). Inulinase activity was higher than invertase activity in the extracellular preparation, the opposite being observed for the cellular preparation. The effects of pH and temperature, substrate specificity and the kinetic constants for inulin and sucrose were studied on both preparations, as well as induction by inulin and repression by glucose and fructose of inulinase and invertase activities. The overall results were consistent with the existence of a least one inulinase, (EC 3.2.1.7), mainly but not entirely released in the extracellular medium, and an invertase (3.2.1.26) localized within the cell. Time course hydrolysis experiments of dalhia inulin and Jerusalem artichoke inulofructans by extracellular inulinase showed that this preparation had a remarkably high specificity for hydrolysis of long chain inulofructans.
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