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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Biotechnology letters 10 (1988), S. 695-698 
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The pH and serum dependence of the glutamine decomposition rate constant, Kgln, in Dulbecco's Modified Eagle's Medium, DMEM, was determined. The findings indicate that Kgln increases with increase in pH and fetal calf serum (FCS) concentration in DMEM. At a constant pH of 7.25, Kgln increases from 5.7×10−4 to 13.2×10−4 h−1 as FCS content of the medium increases from 0.0 to 10.0 (% v/v). Moreover, at a constant FCS of 10 (% v/v), Kgln increases from 11.5×10−4 to 33.6×10−4 h−1 as pH of the medium increases from 7.2 to 7.6.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Glycolic acid ; Helianthus ; Photosynthesis ; Photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Attached leaves of sunflower (Helianthus annuus L.) were exposed to 14CO2 during steady-state photosynthesis for 2 to 30 min in 345 μl/l CO2 and 21% O2 at 29° C and a light intensity of 1300 μE m-2s-1. Glycolic acid was extracted with water and diethyl ether, and was determined in the aqueous residue by high-pressure liquid column chromatography. The relative specific radioactivity of the glycolic acid synthesized during photosynthesis reached about 100% after 30 min of photosynthesis and was almost equal to that of the CO2 evolved during photorespiration, their ratio at all times being nearly one. These results provide strong in-vivo evidence that the glycolic acid is the substrate for CO2 evolved by sunflower leaves in light.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-6776
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of CO2 removal by continuous sparging of N2 in batch cultures ofZymomonas mobilis (ATCC10988) was examined. N2 sparging considerably reduces lag times in batch cultures, possibly because of continuous removal of CO2 from the culture media. Ventilation of CO2 from culture media results in an increase of about 15% in the average specific growth rate and about 12% in the cell-mass yield with no noticeable trend in the average specific glucose uptake and ethanol production rates. The overall ethanol yield on glucose, however, decreases slightly by 5%. Analysis of ventilated experiments show that the CO2 production is directly coupled with the ethanol formation but not necessarily with the cell-mass production, indicating a decoupling of growth from ethanol production. Further, comparison of ventilated and non-ventilated experiments rules out the possibility of CO2 accumulation in the culture media as a factor responsible for increasing growth inhibition and decoupling of growth from ethanol fermentation at increasing initial glucose concentrations in batch cultures.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Biotechnology techniques 1 (1987), S. 19-24 
    ISSN: 1573-6784
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The efficacy of a modified turbidostat scheme for control of a continuous fermentor supporting substrate - inhibited growth of a methylotroph, L3, was experimentally examined. The control was based on continuous measure of optical density of fermentation broth. The experimental results illustrate the feasibility of the control scheme for effective startup as well as stabilization of a continuous fermentor under the influence of a load disturbance.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 344-354 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: On-line measurement of the important state variables in fermentations, particularly cell mass concentration, remains a difficult problem. However, a number of secondary or environmental variables can be measured conventionally and on-line, such as pH, and CO2 and O2 in the exhaust gas. Stephanopoulos and San (1984) have developed a modeling approach, based on species balances, that provides relations between the environmental and important state variables. Using such a model, the important state variables can be estimated in principle from more easily accessible on-line measurements.In this article, a new adaptive estimator is developed, incorporating as its basis an underlying nonlinear model so as to utilize the best possible a priori process knowledge. Base addition rate and CO2 offgas concentration are measured on-line and periodically. Cell mass measurements are incorporated infrequently and even at irregular sampling periods, thus providing a very flexible scheme. Only a single adapted parameter is required to match the model to the plant operating characteristics. This simple but rigorous model form results in an estimator that is easy to implement and to tune and which exhibits long-term robustness due to its multirate feedback structure. Experimental results from a laboratory-scale continuous fermentor show that such a cell mass estimation scheme yields excellent performance both open-loop (without control) and as a part of conventional and nonlinear adaptive control approaches.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 26 (1984), S. 1352-1363 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The growth dynamics of a methanol utilizing bacterium, L3, in batch bioreactors were experimentally investigated. Formaldehyde, a key intermediate of methanol oxidation, is indicated to have a significant role in the complex batch growth behavior of L3. The intricate batch growth dynamics of many microorganisms can be elegantly characterized by examining the specific rates of exchange of nutrients and products between the cells and the cellular environment. Following such an analysis, the batch growth of L3 on methanol was characterized by the presence of unbalanced and balanced growth phases. The nature and significance of nutrient and product concentration profiles or semilog-arithmic profiles of nutrient and product exchange rates during balanced and unbalanced growth phases are also outlined.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 31 (1988), S. 770-782 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Batch fermentations of glucose to ethanol by Z. Mobilis.(ATCC 10988) were examined in several semidefined nutrient media. The measurement of acid produced by the microorganism was used to study its transient fermentation characteristics. Limitation of nitrogen source in the semidefined medium of Rogers and coworkers2 was found to limit the growth of this microorganism in the late stages of batch fermentations, when the initial glucose concentration was 75 g/L and higher. The microorganism exhibits a preference for inorganic nitrogen over preformed organic nitrogen provided by yeast extract. The microbial growth occurs exponentially in the presence of ammonium sulfate and yeast extract. However, in the absence of ammonium sulfate, the growth occurs in a linear fashion. The “linear” growth phase is characterized by poor cell-mass yields, and during this phase, growth and ethanol production are decoupled. An improved semi-defined growth medium is established which supports better growth rate and cellular yield, without affecting the ethanol yield.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 104-114 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two novel, nitrogen-limited and oxygen-limited, perturbed transient experiments were performed to examine the presence of active transport of methanol and study the effect on methanol uptake by a methanol-utilizing bacterium, L3, in a batch bioreactor. Transient limitations of both ammonium ions and O2 in batch cultures were found to cause methanol leakages out of the cells, suggesting the presence of an active transport of methanol in L3. Such experimental results were used to indirectly estimate the intracellular levels of methanol during a batch growth of L3. The results of our analysis indicate that the intracellular methanol level is high and show an increasing trend during the unbalanced phase, but falls to a constant low level in the balanced phase of a typical batch growth8 of L3. A simple modelling analysis suggests that a four-parameter “pump-and-extrusion” model could be used to adequately describe the transport of methanol between the extra cellular and intracellular phases of batch cultures of L3.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 115-125 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An algorithm for operating a fed-batch fermentor at an optimum specific fermentation rate is proposed. It does not require on-line measurement of nutrient concentration in the culture medium. An on-line estimate of the specific fermentation rate is sufficient for implementation of this scheme. The algorithm is model independent and works well even with poor estimates of the product yields and the specific fermentation rate. Results of a detailed simulation study are presented for a simple case of optimization of cell-mass production in a fed-batch fermentor. The results clearly demonstrate the efficacy of this algorithm under a wide range of fermentation situations.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 265-272 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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