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  • 1
    ISSN: 1476-5535
    Keywords: Keywords: pentachlorophenol; biodegradation; growth physiology; cultivation; Mycobacterium chlorophenolicum PCP-1; Sphingomonas chlorophenolica RA2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The physiological characteristics of growth and pentachlorophenol degradation of the bacteria Sphingomonas chlorophenolica RA2 and Mycobacterium chlorophenolicum PCP-1 were studied quantitatively in liquid culture under various conditions of pH, temperature, pO2, pCO2 and PCP concentration. Concerning their metabolic properties, RA2 and PCP-1 can be regarded as r-strategist and K-strategist, respectively. RA2 showed a higher activity concerning growth and PCP degradation than PCP-1 under optimum conditions. However, PCP-1 performed better under extreme conditions. Maximum growth rates or RA2 and PCP-1 on glucose were 0.21 h−1 and 0.024 h−1 and maximum PCP degradation rates 315 and 40 μmol (g of dry cells)−1 h−1, respectively. Optimized cultivation for RA2 on a technical scale led to the production of 40 g L−1 of cell dry mass within 55 h. The cultivation strategy including pH-controlled ammonium feeding can be used to effectively produce sufficient biomass of both strains for both research and application as inoculants in soil clean-up.
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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 inhibitory effect of ammonia on the growth of the polychlorinated xenobiotic-degrading bacterium Mycobacterium chlorophenolicum was examined. The strain is inhibited by both the ionized and nonionized forms of ammonia. At pH 6.9 50% reduction of the growth rate was observed at 6.8 g l-1 total ammonium. For 23 experiments performed in shake-flask culture at different pH values and ammonium concentrations a growth model based on the extended Monod kinetic fits the data with a deviation of 5.3%. To overcome growth inhibition in bioreactors a pH-controlled feeding strategy was developed for effective cultivation of M. chlorophenolicum at an ammonium level below 0.3 g l-1. The ammonium addition was controlled on-line by the stoichiometric interdependence of ammonium consumption and pH decline. With this on-line control strategy a biomass concentration as high as 26.2 g l-1 can be achieved within less than 1 week of cultivation, compared to a biomass concentration of 15.5 g l-1 in normal batch culture after 2 weeks of cultivation. The yield is also increased from 0.32 g to 0.43 g biomass (g glucose)-1. The strategy developed provides an effective method for the production of biomass of M. chlorophenolicum serving as the inoculum in remediation technologies.
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  • 3
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The inhibitory effect of ammonia on the growth of the polychlorinated xenobiotic-degrading bacterium Mycobacterium chlorophenolicum was examined. The strain is inhibited by both the ionized and nonionized forms of ammonia. At pH 6.9 50% reduction of the growth rate was observed at 6.8 g l−1 total ammonium. For 23 experiments performed in shake-flask culture at different pH values and ammonium concentrations a growth model based on the extended Monod kinetic fits the data with a deviation of 5.3%. To overcome growth inhibition in bioreactors a pH-controlled feeding strategy was developed for effective cultivation of M. chlorophenolicum at an ammonium level below 0.3 g l−1. The ammonium addition was controlled on-line by the stoichiometric interdependence of ammonium consumption and pH decline. With this on-line control strategy a biomass concentration as high as 26.2 g l−1 can be achieved within less than 1 week of cultivation, compared to a biomass concentration of 15.5 g l−1 in normal batch culture after 2 weeks of cultivation. The yield is also increased from 0.32 g to 0.43 g biomass (g glucose)−1. The strategy developed provides an effective method for the production of biomass of M. chlorophenolicum serving as the inoculum in remediation technologies.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 34 (1991), S. 463-468 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The production of 2,3-butanediol by Enterobacter aerogenes DSM 30053 was studied in a cell recycle system with a microfiltration module. Emphasis was put on the influence of oxygen supply, cell residence time, dilution rate, and pH. Under optimal conditions a productivity as high as 14.6 g butanediol + acetoin/l per hour was achieved with a product concentration of 54 g/l and a product yield of 88%. This productivity is three times higher than that of an ordinary continuous culture. The achievable final product concentration of a cell recycle system was limited by the accumulation of the inhibiting by-product acetic acid, which increased very rapidly at low dilution rate. To maximize product concentration a fed-batch fermentation was carried out with stepwise pH adaption at high cell density. A final product concentration of 110 g/l was obtained with a productivity of 5.4 g/l per hour and a yield of 97%.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 42 (1995), S. 688-691 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract A general and simple equation is presented to account for the effect of CO2 absorption and the dissociation of carbonic acid in liquid on the measurement of the CO2 evolution rate (QCO2) of both anaerobic and aerobic continuous cultures. For aerobic cultures the same equation applies to the measurement of the respiratory quotient (RQ). The deviation of QCO2 and RQ, calculated from gas-phase measurements, from their true values can be assessed with two parameters: one accounts for the influence of pH, resulting from dissociation of carbonic acid, the other for the influence of operating conditions. Plots are given to show the influences of culture and operating conditions; they may be used as a guideline for choosing proper operating conditions for a reliable measurement of CO2 evolution rate and RQ value.
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  • 6
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Product formation during anaerobic degradation of glycerol byKlebsiella pneumoniae DSM 2026, under glycerol limitation and glycerol excess in continugius cultures, has been investigated. Major and minor products and by-products as well as gaseous products were measured. The results indicated a positive correlation between specific glycerol uptake and most product formation rates under glycerol limitation. The production of 1,3-propanediol, lactate, formate, acetate, succinate and the by-products of anaerobic glycerol degradation byK. pneumoniae, acetoin and 2,3-butanediol, was favoured by glycerol excess, while hydrogen generation and ethanol formation were best under glycerol limitation. It was also found that under glycerol limitation the rate of hydrogen evolution was generally higher than the CO2 production rate while under excess glycerol the reverse was true. Hence, on the basis of the ratio of the specific rates of evolution of H2 and CO2 (q H 2/q CO 2), it is possible to infer the existence of glycerol limitation. On the basis of the carbon and available electron balances, which are independent of metabolic pathways, the data are consistent. The NADH2 balance, which took into consideration the pathways of product formation, was also tested to check the validity of the assumed pathways and to check critically the consistency of the data. Good balances were also obtained.[
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  • 7
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Product formation during anaerobic degradation of glycerol by Klebsiella pneumoniae DSM 2026, under glycerol limitation and glycerol excess in continuous cultures, has been investigated. Major and minor products and by-products as well as gaseous products were measured. The results indicated a positive correlation between specific glycerol uptake and most product formation rates under glycerol limitation. The production of 1,3-propanediol, lactate, formate, acetate, succinate and the by-products of anaerobic glycerol degradation by K. pneumoniae, acetoin and 2,3-butanediol, was favoured by glycerol excess, while hydrogen generation and ethanol formation were best under glycerol limitation. It was also found that under glycerol limitation the rate of hydrogen evolution was generally higher than the CO2 production rate while under excess glycerol the reverse was true. Hence, on the basis of the ratio of the specific rates of evolution of H2 and CO2 (q H2/q CO2), it is possible to infer the existence of glycerol limitation. On the basis of the carbon and available electron balances, which are independent of metabolic pathways, the data are consistent. The NADH2 balance, which took into consideration the pathways of product formation, was also tested to check the validity of the assumed pathways and to check critically the consistency of the data. Good balances were also obtained.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 42 (1995), S. 688-691 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  A general and simple equation is presented to account for the effect of CO2 absorption and the dissociation of carbonic acid in liquid on the measurement of the CO2 evolution rate (QCO2) of both anaerobic and aerobic continuous cultures. For aerobic cultures the same equation applies to the measurement of the respiratory quotient (RQ). The deviation of QCO2 and RQ, calculated from gas-phase measurements, from their true values can be assessed with two parameters: one accounts for the influence of pH, resulting from dissociation of carbonic acid, the other for the influence of operating conditions. Plots are given to show the influences of culture and operating conditions; they may be used as a guideline for choosing proper operating conditions for a reliable measurement of CO2 evolution rate and RQ value.
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  • 9
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Alginate production by Azotobacter vinelandii was studied in batch and continuous cultures under microaerobic conditions. In batch culture at a pO2 of 2–3% (air saturation) alginate production was enhanced by decreasing the PO3− 4 level in the medium. Alginate yield from biomass (Y P/X) reached the highest value of 0.66 g/g at the lowest phosphate level (100 mg/l), compared to 0.40 g/g and 0.25 g/g at higher phosphate levels (200 mg/l and 400 mg/l, respectively). In contrast, biomass formation behaved differently and the growth yield (Y X/S) decreased with decreasing PO4 3− concentrations. Moreover, the respiratory quotient (RQ) of the culture was dependent on the initial phosphate concentration, especially in the phosphate-limited phase of growth. As the initial phosphate level decreased from 400 mg/l to 100 mg/l, the average RQ value of the culture declined from 1.46 to 0.89. The low RQ value is very close to the theoretical optimum RQ, calculated to be 0.8 on the basis of the stoichiometry of the metabolic pathways for alginate formation from sucrose. This optimum RQ was also confirmed in continuous culture at different dilution rates. Independent of the dilution rate, a pO2 value of 2–5% (air saturation) was found to be optimal for alginate production, the corresponding RQ values being 0.80–0.84. In addition, the molecular mass and composition of alginate were also found to be affected by both phosphate and oxygen concentrations. In conclusion, the RQ appears to be a useful parameter for optimum control of alginate production with this microorganism.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 52 (1999), S. 289-297 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract 1,3-Propanediol (1,3-PD) production by fermentation of glycerol was described in 1881 but little attention was paid to this microbial route for over a century. Glycerol conversion to 1,3-PD can be carried out by Clostridia as well as Enterobacteriaceae. The main intermediate of the oxidative pathway is pyruvate, the further utilization of which produces CO2, H2, acetate, butyrate, ethanol, butanol and 2,3-butanediol. In addition, lactate and succinate are generated. The yield of 1,3-PD per glycerol is determined by the availability of NADH2, which is mainly affected by the product distribution (of the oxidative pathway) and depends first of all on the microorganism used but also on the process conditions (type of fermentation, substrate excess, various inhibitions). In the past decade, research to produce 1,3-PD microbially was considerably expanded as the diol can be used for various polycondensates. In particular, polyesters with useful properties can be manufactured. A prerequisite for making a “green” polyester is a more cost-effective production of 1,3-PD, which, in practical terms, can only be achieved by using an alternative substrate, such as glucose instead of glycerol. Therefore, great efforts are now being made to combine the pathway from glucose to glycerol successfully with the bacterial route from glycerol to 1,3-PD. Thus, 1,3-PD may become the first bulk chemical produced by a genetically engineered microorganism.
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