Showing papers on "Chemostat published in 1988"
TL;DR: This initial rate approach, in contrast with steady state analysis of chemostat cultures, approximates steady state behavior, since the rates were measured over brief time intervals and at low cell concentrations (< 50,000 cells/mL).
Abstract: The lack of quantitative descriptions of mammalian culture kinetics limits the ability to optimally design and control cell culture bioreactors. This limitation is ad dressed by developing mathematical equations relating the initial growth rate and the antibody productivity of the hybridoma cell line, CRL-1606, to its environmental state. This initial rate approach, in contrast with steady state analysis of chemostat cultures, approximates steady state behavior, since the rates were measured over brief time intervals and at low cell concentrations (< 50,000 cells/mL). The advantage of this approach is that it is much faster than the chemostat approach.
An equation for the growth rate was developed that superimpoed Monod equations in serum and glutamine with “noncompetitive” -type inhibition constants were inversely proportional to the lactate and ammonium concentrations. The Monod constant is critical for relating initial, low cell level culture states to other states.
Lactate was found to be the only environmental parameter that significantly inhibited antifibronectin monoclonal antibody production by the CRL-1606 hybridimas. Volumetric productivity was strictly related to culture viability, which was observed to decline at growth rates below 0.02h−1. Lactate was also found to significantly inhibit ammonium production.
183 citations
TL;DR: From these experiments, the influence of biofilm diffusion limitation on reaction kinetics and criteria for stable biofilm formation on sand particles were obtained.
Abstract: Naphthalene-2-sulfonate was degraded by submerse growing Pseudomonads in a chemostat culture. The kinetic parameters for the Monod equation, including Pirts maintenance energy, were calculated from these experiments regarding naphthalene-2-sulfonate as substrate and oxygene as cosubstrate. By immobilizing the bacteria on sand particles, the degradation of naphthalene-2-sulfonate was carried out in a specialy designed three-phase airlift-loop reactor in a completely fluidized state. From these experiments, the influence of biofilm diffusion limitation on reaction kinetics and criteria for stable biofilm formation on sand particles were obtained.
66 citations
TL;DR: The relation between the kinetic parameters of glucose transport and the physiology of Candida utilis CBS 621 was studied in chemostat cultures, where the transport parameters were dependent on the growth rate of the yeast.
Abstract: SUMMARY: The relation between the kinetic parameters of glucose transport and the physiology of Candida utilis CBS 621 was studied in chemostat cultures. In glucose-limited cultures the transport parameters were dependent on the growth rate of the yeast. Three different transport systems were found which differed by an order of magnitude in their affinity constants, namely a high-affinity (K
m 25 μM), a medium-affinity (K
m 190 μM), and a low-affinity uptake system (K
m 2000 μM). Cells growing at a dilution rate of 0.45 h-1 or less had the high- and medium-affinity uptake systems. At a dilution rate of 0.52 h-1 the high-affinity system was absent and both the medium-and low-affinity systems were present. At a dilution rate close to μmax (0.57 h-1) only the low-affinity system was detected. The in situ contribution of each of the transport systems to glucose consumption in glucose-limited cultures was estimated on the basis of their kinetic parameters (K
m and V
max) and the residual glucose concentration in these cultures. The sum of the calculated rates of transport corresponded to the in situ rate of glucose consumption by the cultures as determined from the yield constant and the dilution rate. The dependence of the transport parameters on the growth rate and hence on the environmental sugar concentration was also evident in cells grown under nitrogen limitation. In contrast to carbon-limited cells, nitrogen-limited cultures growing at D = 0.15 h-1 did not exhibit the high-affinity glucose uptake system, whereas the medium- and low-affinity systems were present.
64 citations
TL;DR: It is found that such a mixed culture can coexist in a chemostat only if there is a range of substrate concentrations where the plasmid-bearing cells grow at a specific rate which is larger than the specific growth rate of the plasmsid-free cells.
59 citations
TL;DR: In this paper, the fermentation of xylose by Thermoanaerobacter ethanolicus ATCC 31938 was studied in pH-controlled batch and continuous cultures.
Abstract: The fermentation of xylose by Thermoanaerobacter ethanolicus ATCC 31938 was studied in pH-controlled batch and continuous cultures. In batch culture, a dependency of growth rate, product yield, and product distribution upon xylose concentration was observed. With 27 mM xylose media, an ethanol yield of 1.3 mol ethanol/mol xylose (78% of maximum theoretical yield) was typically obtained. With the same media, xylose-limited growth in continuous culture could be achieved with a volumetric productivity of 0.50 g ethanol/liter h and a yield of 0.42 g ethanol/g xylose (1.37 mol ethanol/mol xylose). With extended operation of the chemostat, variation in xylose uptake and a decline in ethanol yield was seen. Instability with respect to fermentation performance was attributed to a selection for mutant populations with different metabolic characteristics. Ethanol production in these T. ethanolicus systems was compared with xylose-to-ethanol conversions of other organisms. Relative to the other systems, T. ethanolicus offers the advantages of a high ethanol yield at low xylose concentrations in batch culture and of a rapid growth rate. Its disadvantages include a lower ethanol yield at higher xylose concentrations in batch culture and an instability of fermentation characteristics in continuous culture.
53 citations
TL;DR: Studies in conventional batch culture confirmed that the maximum citric acid production rate occurred prior to exhaustion of the growth‐limiting nutrient, i.e., when the growth rate was nonzero, and these findings were applied to a nitrogen‐limited fed batch culture and allowed a productivity increase of 100% when compared with conventionalbatch culture.
Abstract: Studies in conventional batch culture confirmed that the maximum citric acid production rate occurred prior to exhaustion of the growth-limiting nutrient, i.e., when the growth rate was nonzero. The effects of dilution rate and the culture dissolved oxygen tension (DOT) were studied in chemostat culture. Maximum citric acid yield and production rate were observed at low dilution rate (0.017 h(-1)) and high DOT value (90% of saturation). These findings were applied to a nitrogen-limited fed batch culture, and allowed a productivity increase of 100% when compared with conventional batch culture.
44 citations
TL;DR: It is proposed that the oscillatory behavior observed during continuous culture is an inherent characteristic related to the shift from primary to secondary metabolism and precludes the attainment of a true steady state during continuousculture.
Abstract: The concurrent production of acids and solvents and the production of acetone during continuous culture in a product-limited chemostat indicated that the culture contained a mixture of acid- and solvent-producing cells. Periodic oscillations in the yield of end products and the specific growth rate of the culture were ob served during undisturbed continuous culture at a constant dilution rate. The increased specific growth rate was associated with an increased acid yield and an increase in the rate of cell division and the proportion of short rods. The decreased specific growth rate was as sociated with an increase in the solvent yield and a decrease in the rate of cell division, resulting in the production of elongated rods. It is proposed that the oscillatory behavior observed during continuous culture is an inherent characteristic related to the shift from primary to secondary metabolism. A major consequence of the oscillation of the specific rates of growth and division in cultures containing acid- and solvent-producing cells is that it precludes the attainment of a true steady state during continuous culture.
43 citations
TL;DR: Molar growth yields corrected for the substrate costs of product formation were high, indicating a high efficiency of growth, and the energy costs of protein formation are higher than those of biomass formation or protein excretion.
Abstract: Substrate and energy costs of the production of exocellular enzymes from glucose and citrate by B. Iicheniformis S1684 as well as molar growth yields corrected for these costs of product formation were calculated using data from chemostat experiments. The calculations showed that 1.46-1.73 mol glucose and 2.31-2.77 mol citrate are needed for formation and excretion of 1 mol protein. Consequently, the values of the maximal product yield from substrate (Y(psm') g/mol) are 80 < Y(psm) < 95 when product is formed from glucose and 50 < Y(psm) < 60 when product is formed from citrate. The higher substrate costs for product formation from citrate are due to a higher level of CO(2) production during protein formation and a higher substrate requirement for the energy supply of product formation and excretion than when product is formed from glucose. The theoretical ATP requirement for protein synthesis could be determined reasonably well, but the energy costs of protein excretion could not be determined exactly. The energy costs of protein formation are higher than those of biomass formation or protein excretion. Molar growth yields corrected for the substrate costs of product formation were high, indicating a high efficiency of growth.Growth and production parameters were determined as well from experimental data of recycling fermentor experiments using a parameter optimization procedure based on a mathematical model describing biomass growth as a linear function of the substrate consumption rate and the rate of product formation as a linear function of biomass growth rate. The fitting procedure yielded two growth and production domains during glucose limitation. In the first domain the values for the maximal growth yield and maintenance coefficient were in agreement with those found in chemostat experiments at corresponding values of Y(spm). Domain 2 could be described best with linear growth and product formation. In domain 2 the rate of product formation decreased and more substrate became available for biomass formation. As a consequence the specific growth rate increased in the shift from domain 1 to 2. Domain 2 behavior most probably is caused by the rel-status of B. Iicheniformis S1684.
41 citations
TL;DR: A hybrid strain was selected that was more tolerant than any of the highly ethanol-tolerant wine yeast strains at any concentration of ethanol and was able to grow at up to 16% (vol/vol) ethanol, which led to an increase in both the ethanol production rate and the total amount of ethanol produced.
Abstract: Hybrids between naturally occurring wine yeast strains and laboratory strains were formed as a method of increasing genetic variability to improve the ethanol tolerance of yeast strains. The hybrids were subjected to competition experiments under continuous culture controlled by pH with increasing ethanol concentrations over a wide range to select the fastest-growing strain at any concentration of ethanol. The continuous culture system was obtained by controlling the dilution rate of a chemostat connected to a pH-meter. The nutrient pump of the chemostat was switched on and off in response to the pH of the culture, which was thereby kept near a critical value (pHc). Under these conditions, when the medium was supplemented with ethanol, the ethanol concentration of the culture increased with each pulse of dilution. A hybrid strain was selected by this procedure that was more tolerant than any of the highly ethanol-tolerant wine yeast strains at any concentration of ethanol and was able to grow at up to 16% (vol/vol) ethanol. This improvement in ethanol tolerance led to an increase in both the ethanol production rate and the total amount of ethanol produced.
39 citations
TL;DR: The relationship between bacterial cell volume and temperature was examined for field data collected over a 4-year period and through controlled chemostat incubations of aseudomonas sp.
Abstract: The relationship between bacterial cell volume and temperature was examined for field data collected over a 4-year period and through controlled chemostat incubations of aPseudomonas sp. Volumes of planktonic bacteria were found to decrease as water temperature increased. Changes in temperature accounted for 38% of the variation in average cell volume (P<0.001). Average planktobacterial cell volume fell 42% from 0.217μm3 in mid-winter to 0.127μm3 in mid-summer. Similar results were found for the size distribution of epibacterial cells. Controlled chemostat incubations of aPseudomonas sp. indicated that cell volume was significantly affected by temperature, growth rate, and the interaction of temperature and growth rate. The data suggest that a change in cell volume as a result of a change in temperature is an intrinsic property of planktonic bacteria.
38 citations
TL;DR: A pUB110-derived plasmid encoding chloramphenicol resistance, kanamycin resistance and high-temperature alpha-amylase showed a high degree of segregational instability when inserted into Bacillus subtilis in an attempt to obtain stable derivatives.
Abstract: SUMMARY: A PUB 110-derived plasmid encoding chloramphenicol resistance, kanamycin resistance and high-temperature α-amylase showed a high degree of segregational instability when inserted into Bacillus subtilis. In an attempt to obtain stable derivatives, the organism was grown in chemostat culture in the presence of chloramphenicol. It was periodically found necessary to increase the concentration of chloramphenicol in the medium feed in order to avoid plasmid loss. Strains were isolated after 19 and 160 generations, which showed high levels of plasmid stability. This characteristic appeared to be genotypic. No detectable difference in plasmid copy number was found between the original and the improved strains. The stability characteristics resided in the host, rather than in the plasmid. Stable isolates possessed elevated MICs for both chloramphenicol and kanamycin. Their maximum specific growth rates were higher than that of the original strain, and similar to that of the plasmid-free parent strain.
TL;DR: The complete lack of autotrophic growth, both in batch and chemostat experiments, together with the absence of even very low amounts of the key enzymes of the Calvin cycle demonstrated that this organism is a typical chemolithoheterotroph.
Abstract: The physiological properties of an organism isolated from a selective chemostat enrichment using acetate and thiosulphate as the limiting substrates, provisionally called Thiobacillus Q, were investigated. Although the organism made up 85% of the community in the enrichment culture, its expected chemolithotrophic nature was not apparent in batch experiments. The growth yield was not enhanced by the addition of thiosulphate to an acetate containing mineral medium, even though up to 50% of the thiosulphate was oxidized. Under acetate limitation in the chemostat, there was a linear increase in yield with thiosulphate addition up to a concentration of 7 mM. Higher thiosulphate concentrations resulted in loss of thiosulphate oxidizing capacity and a decrease in the biomass to the level obtained with acetate alone. This loss may be due to the presence of inhibitory (50–100 μM) levels of sulphite which is probably produced as an intermediate of the biological thiosulphate oxidation. Experiments with sulphide showed that Thiobacillus Q could also use it as an additional energy source. The complete lack of autotrophic growth, both in batch and chemostat experiments, together with the absence of even very low amounts of the key enzymes of the Calvin cycle demonstrated that this organism is a typical chemolithoheterotroph. Although this organism has provisionally been placed in the genus Thiobacillus, standard taxonomic procedures showed a close relationship with Pseudomonas alcaligenes. This study stresses the importance of quantitative chemostat studies in establishing the role of inorganic oxidations in energy metabolism and in the understanding of the role of heterotrophic sulphur oxidation in natural environments.
TL;DR: A simple one-dimensional reaction-diffusion model, which incorporated data on the product-inhibited growth kinetics of free-living cells collected in a product-limited chemostat, satisfactorily predicted product inhibition of immobilized cell growth.
Abstract: Mass transfer-limited removal of metabolic products led to product-inhibited growth of Escherichia coli that was immobilized in a model system. Comparison of the growth kinetics of immobilized and free-living cells revealed no further physiological differences between cells in these two modes of existence beyond those manifested in the local concentrations of substrate and product. Bacteria were retained on a microporous membrane in a dense, planar aggregate and were grown anaerobically on a glucose-based minimal medium. Radioisotope labeling of the immobilized cell mass with 35S was used to determine growth kinetic parameters. Growth rates in the immobilized cell layer were measured by an autoradiographic technique which allowed comparison of the size of the growing region with the rate of cell convection caused by growth. Immobilized cell growth rates and growth yields ranged from near maximal (0.56 h-1 and 39 g of dry cell weight/mol of glucose, respectively) to substantially reduced (0.15 h-1 and 15 g/mol). The depression of these kinetic parameters was attributed to product inhibition arising from mass transfer-limited removal of acidic waste products from the cell mass. A simple one-dimensional reaction-diffusion model, which incorporated data on the product-inhibited growth kinetics of free-living cells collected in a product-limited chemostat, satisfactorily predicted product inhibition of immobilized cell growth.
TL;DR: With a glucose-limited chemostat culture of Bacillus stearothermophilus, increasing the incubation temperature progressively from 45°C to 63°C led to a progressive marked increase in the maintenance rates of glucose and oxygen consumption, and the apparent Yglucosemaxand values did not decrease but actually increased with temperature.
Abstract: With a glucose-limited chemostat culture of Bacillus stearothermophilus, increasing the incubation temperature progressively from 45°C to 63°C led to a progressive marked increase in the maintenance rates of glucose and oxygen consumption. Hence, at a fixed low dilution rate the yield values with respect to glucose and oxygen decreased substantially with increased temperature. However, the apparent Y
glucose
max
and
$$Y_{{\text{O}}_2 }^{\max } $$
values did not decrease but actually increased with temperature, being highest at 63°C (i.e., close to the maximum growth temperature). With glucose-sufficient cultures growing at a fixed low dilution rate (0.2 h−1) and at their optimum temperature (55°C), glucose and oxygen consumption rates invariably were higher than that of a corresponding glucose-limited culture. Cation (K+ or Mg2+)-limited cultures expressed the highest metabolic rates and with the K+ limited culture this rate was found to be very markedly temperature dependent. As the temperature was increased from 45°C to 63°C the rate of glucose consumption increased 1.8-fold, and that of oxygen consumption by 3.7-fold. The culture pH value also exerted a noticeable effect on the metabolic rate of a glucose-limited culture, particularly at the extremes of pH tolerance (5.5 and 8.5, respectively). A K+-limited culture was less affected with respect to metabolic rate by the culture pH value though the steady state bacterial concentration, and thus the cellular K+ content, changed substantially. These results are discussed in relation to previous findings of the behaviour of this organism in batch culture, and to the behaviour of other thermophilic Bacillus species in chemostat culture.
TL;DR: The growth of Pseudomonas putida cells (ATCC 33015) in batch and continuous cultures on two toxic substrates; toluene and m-toluic acid as sole carbon and energy sources is described.
Abstract: The present study describes the growth of Pseudomonas putida cells (ATCC 33015) in batch and continuous cultures on two toxic substrates; toluene and m-toluic acid as sole carbon and energy sources. In fed-batch cultures on m-toluic acid up to 3.55 g cell dry weight/1 were achieved with a maximal specific growth rate (μmax) of 0.1 h-1. The average cellular yield was 1.42 g cell dry weight/g m-toluic acid utilized. When liquid toluene was added to shake-flask cultures in the presence of 0.7 g/1 m-toluic acid, the average cellular yield obtained was 1.3 g cell dry weight/g toluene utilized and the μmax was 0.13 h-1. Growth on toluene vapour in the presence of 0.7 g/l m-toluic acid in batch cultures resulted in a cellular yield of 1.28 g cell dry weight/g toluene utilized, with growth kinetics almost identical to those with liquid toluene (μmax liquid=0.13 h-1, μmax vapour=0.12 h-1). The maximal biomass concentration was 3.8 g cell dry weight/l, obtained in both cases after 100 h of incubation. Pseudomonas putida was grown in a chemostat initially on 0.7 g/l m-toluic acid and vapour toluene and then in the steady state on toluene as the sole source of carbon and energy. Toluene was added continuously to the culture as vapour with the inflowing airstream. Chemostat cultures could be maintained at steady state for several months on toluene. The maximal biomass concentration obtained in the chemostat culture was 3.2 g cell dry weight/l. The maximum specific growth rate was 0.13 h-1, with a cellular yield of 1.05 g cell dry weight/g toluene utilized. Approximately 70% of the toluene consumed was converted into biomass, and the remainder was converted to CO2 and unidentified byproducts.
TL;DR: The effects of forced square-wave perturbations in the dilution rate on plasmid maintenance and gene expression of a population of Escherichia coli K12 strain carrying the vector plasid pBR322 grown in a chemostat with a non-selective medium were studied.
Abstract: The effects of forced square-wave perturbations in the dilution rate on plasmid maintenance and gene expression of a population ofEscherichia coli K12 strain carrying the vector plasmid pBR322 grown in a chemostat with a non-selective medium were studied. It was observed that in the control experiments, where the dilution rates were kept constant, the percentage of plasmid-containing cells decreased after a period of time. Eventually, the culture was displaced by the plasmid-free cells. However, when the cells were exposed to forced oscillations in the dilution rate, the reactor culture was able to maintain a mixed population of plasmid-free and plasmid-containing cells for a longer period of time. The above observation seems to be independent of the source of the host cells. That is, the same results were obtained when the plasmid-free cells were generated from the culture itself due to defective partitioning of the plasmids or introduced externally.
TL;DR: Both the Monod equation, and an extended model regarding the interspecies transfer of 5AS, were found to be suitable to describe the relationship between biomass and substrate concentration, depending on the flow rate of continuous culture.
Abstract: The degradation of 6-aminonaphthalene-2-sulphonic acid (6A2NS) by mixed cultures via an interspecies transfer of 5-aminosalicylic acid (5AS) was investigated using a continuous chemostat culture. Two different bacterial communities were employed. Steady-state data were obtained from a multi-species culture only, but not from a defined two-species culture. Experimental data showed the conversion of 6A2NS into 5AS to be rate-determining for degradation. Both the Monod equation, and an extended model regarding the interspecies transfer of 5AS, were found to be suitable to describe the relationship between biomass and substrate concentration, depending on the flow rate of continuous culture. Substrate consumed for endogenous metabolism was considred according to Pirt (1975).
TL;DR: The ability to use O2 as the sole electron acceptor was demonstrated in a chemostat culture with formate as electron donor and succinate as carbon source, indicating the microaerophilic nature of W. recta.
Abstract: The influence of oxygen on growth and fumarate-dependent respiration of Wolinella recta ATCC 33238 was studied in continuous culture. Steady states were obtained with formate-limited cultures grown at a specific growth rate of 0.1 h−1 with different levels of oxygenation. The extent of aeration was regulated by means of a redox control system permitting reproducible cultivation at oxygen levels below the detection limit of conventional lead-silver probes. The ratio of succinate produced to that of formate consumed (Suc/For) decreased from 0.99 in strictly anaerobic cultures to 0.06–0.10 in aerated cultures. The growth yield did not change significantly with increasing redox readings: 4.9–5.2 g cell carbon/mol formate. The ability to use O2 as the sole electron acceptor was demonstrated in a chemostat culture with formate as electron donor and succinate as carbon source. Washed cells from all chemostat cultures comsumed O2 with formate as electron donor at a high rate (2.1–3.7 μmol/min per mg protein) and possessed b- and c-type cytochromes and CO-binding pigments. These results clearly indicated the microaerophilic nature of W. recta.
TL;DR: A mathematical model is described that fitted rather well for both benzene-transport-limited and kinetically limited production conditions, and during prolonged continuous production under carbon-limited conditions, the mutant cells were outcompeted by revertants after about three days.
TL;DR: Observations indicate that there is preferential assimilation of glucose, at the expense of energy from tetrathionate oxidation, during mixotrophy, resulting in an overall “energy saving” that produces enhanced growth yield.
Abstract: Thiobacillus acidophilus can grow in batch and chemostat culture as a heterotroph on glucose, a chemolithoautotroph on tetrathionate and CO2, or as a mixotroph Mixotrophically it obtains energy from the simultaneous oxidation of tetrathionate and glucose, and carbon from both glucose and CO2 Mixotrophic cultures contain lower activities of ribulose 1,5-bisphosphate carboxylase and exhibit lower specific rates of tetrathionate oxidation than do autotrophic cultures Mixotrophic cultures with low concentrations of glucose have growth rates that are intermediate between slow autotrophic growth and fast heterotrophic growth Slightly more glucose-carbon is assimilated by mixotrophic cultures than by heterotrophic ones provided with the same concentrations of glucose Mixotrophic yield in the chemostat is also slightly greater than predicted from autotrophic and heterotrophic yields These observations indicate that there is preferential assimilation of glucose, at the expense of energy from tetrathionate oxidation, during mixotrophy, resulting in an overall “energy saving” that produces enhanced growth yield These observations are relevant to understanding the regulatory behaviour of T acidophilus in its acidic, mineral-leaching habitats
TL;DR: A toxic shock syndrome isolate of Staphylococcus aureus was grown in a chemostat, in a defined synthetic medium of six amino acids, glucose, two vitamins and salts, and steady states were achieved under limiting and replete Mg2+ conditions and at a range of relative specific growth rates.
Abstract: SUMMARY: A toxic shock syndrome isolate of Staphylococcus aureus was grown in a chemostat, in a defined synthetic medium of six amino acids, glucose, two vitamins and salts. Steady states were achieved under limiting and replete Mg2+ conditions and at a range of relative specific growth rates. The biomass and toxic shock syndrome toxin-1 (TSST-1) were estimated at each condition. Under Mg2- limitation the biomass and TSST-1 production rates were reduced compared to Mg2+ replete conditions. Optimal TSST-1 production occurred at 0.81 relative specific growth rate.
TL;DR: It was concluded that electron transportosphorylation probably occurs both under aerobic and anaerobic conditions, while the high growth yields observed under aerobic conditions are likely to be explained by citric acid cycle activity coupled to electron transport phosphorylation.
Abstract: Actinomyces viscosus is a predominant microorganism in dental plaque. It is, just as the oral Streptococcus spp., a saccharolytic and aero-tolerant organism. We have investigated the effects of oxygen on the growth and metabolism of A. viscosus . To this end A. viscosus Ut 2 was grown in a glucose limited chemostat culture on a chemically defined medium ( D = 0.2 h−1) with exposure to variable amounts of oxygen. The Yglucose increased from 62.5 g · mol−1 under anaerobic conditions to 149 g · mol−1 under aerobic conditions, while, concomitantly, the carbon recovery from acidic fermentation products decreased from 75% to 7%. Addition of [14C]glucose to the chemostat showed that the glucose, which was not converted to acidic fermentation products, was instead converted to carbon dioxide or used for the production of biomass. Under aerobic and anaerobic conditions identical cytochrome spectra, containing only two cytochrome b -type absorption bands, were found. It was concluded that electron transport phosphorylation probably occurs both under aerobic and anaerobic conditions. Anaerobically, fumarate served as the electron acceptor, while the high growth yields observed under aerobic conditions are likely to be explained by citric acid cycle activity coupled to electron transport phosphorylation.
TL;DR: A futile cycle involving carbon dioxide is proposed as a factor contributing to the variable extent of free energy dissipation within this organism.
Abstract: The effects of the partial pressure of carbon dioxide on the growth energetics of Clostridium sporogenes NCIB 8053 grown in chemostat culture were investigated in defined minimal media. Both the ‘maintenance’ requirements and the growth yield coefficients were dependent upon the partial pressure of carbon dioxide in otherwise glucose-limited cultures. Since growth yield coefficients decreased along with the apparent ‘maintenance’ requirements in essential amino acid/fatty acid medium when the partial pressure of carbon dioxide was increased above 0.5 atm, the occurrence of some type of metabolic uncoupling seemed likely. By contrast, when the organism was grown in amino acid complete medium both the maintenance requirements and the growth yield coefficients were increased when the partial pressure of carbon dioxide was raised above 0.5 atm partial pressure of carbon dioxide, suggesting an increased efficiency of growth. A futile cycle involving carbon dioxide is proposed as a factor contributing to the variable extent of free energy dissipation within this organism.
TL;DR: The scum actinomycete Nocardia amarae was grown in batch culture and in chemostat culture on a fructose-peptone-yeast extract substrate and the results are compared with findings of other researches for other sludge bacteria.
TL;DR: The microbial kinetic technique developed in this research may increase the attractiveness of batch experiments because the approach is faster and easier than che mostat studies, however, a detailed comparison between radiochemical batch and chemostat methods is needed to fully assess the utility of the new technique.
TL;DR: It is shown that the slope of the line relating catabolism to anabolism varies very little due to variation of the macromolecular cell composition with growth rate, at least under the tested conditions.
TL;DR: The bacterial strain mA3 capable of utilizing 3‐aminophenol as the sole source of carbon, energy and nitrogen for growth was isolated from an enrichment culture and identified as an Arthrobacter species.
Abstract: The bacterial strain mA3 capable of utilizing 3-aminophenol as the sole source of carbon, energy and nitrogen for growth was isolated from an enrichment culture and identified as an Arthrobacter species. Utilization of 0.68 mg/ml 3-aminophenol by batch cultures of this organism was characterized by a specific growth rate (mu) of 0.18 h-1 and a yield coefficient (Y) of 0.60. In chemostat cultures of strain mA3 we determined a critical dilution rate (Dc) of 0.175 h-1 by continuous addition of mineral salt medium with 0.5 mg/ml 3-aminophenol. Evidence was obtained that the degradation of catechol by 3-aminophenol induced as well as non-induced cells follows the beta-ketoadipate pathway. The excess ammonium ions, originating from 3-aminophenol degradation and not needed for assimilation were released into the medium. Cells adapted to 3-aminophenol exhibited a high substrate specificity. Among different aromatic substances tested, only catechol and 3,4-dihydroxybenzoate could serve as a carbon source for growth. The importance of the meta position of the amino group for the first step of hydroxylation is discussed in connection with the substrate specificity of whole mA3 cells.
TL;DR: Pseudostationary experiments (chemostat cultures) revealed a decrease of D R with increasing concentration of starting material interpreted as an inhibition of respiration by the starting material resulting also in a reduction of biomass concentration: glucose uptake was not affected.
TL;DR: Besides polymer production, the cloned bioluminescent Xanthomonas campestris was used for mass transfer rate studies and Oxygen and nutrient mass transfer coefficients were determined by analysis of the luminescence response to induced fluctuations in their concentration.
TL;DR: Control of bacteriochlorophyll, magnesium protoporphyrin monomethyl ester, cytochromes, and coproporphyrine by light was studied with chemostat cultures of Rhodobacter sphaeroides, suggesting that light controls a second step of MgPME conversion whenever too much precursor is available, owing to the low sensitivity of the initial step of control.
Abstract: Control of bacteriochlorophyll (Bchl), magnesium protoporphyrin monomethyl ester (MgPME), cytochromes, and coproporphyrin by light was studied with chemostat cultures of Rhodobacter sphaeroides growing at a constant dilution rate. By increasing the growth-limiting light energy flux from 10 to 55 W/m2, specific Bchl contents decreased from 19.3 to 7.9 nmol/mg of protein. This was strictly proportional to a decrease in the ratio of B800-850 to B875 light-harvesting complexes. MgPME levels increased from 1.5 to 5.3 nmol/mg of protein, while cytochrome as well as coproporphyrin levels stayed constant at 0.46 and 1.95 nmol/mg of protein, respectively. Since in chemostat cultures steady-state levels of a product represent the rate of synthesis, these results infer only slight control of the rate-limiting step of total tetrapyrrol formation by light. In substrate-limited cultures MgPME was accumulated when growth and Bchl formation approached substrate saturation. This suggests that light controls a second step, i.e., MgPME conversion, whenever too much precursor is available, owing to the low sensitivity of the initial step of control. MgPME was preferentially localized in a subcellular fraction with high contents of B875 complexes. A second fraction exhibiting increased contents of B800-850 complexes lacked significant levels of MgPME. These results are discussed in terms of localization of Bchl synthesis in the membrane system of R. sphaeroides.