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1.
Interactions between microbial growth and substrate degradation are important in determining the performance of trickle-bed
bioreactors (TBB), especially when salt is added to reduce biomass formation in order to alleviate media clogging. This study
was aimed at quantifying salinity effects on bacterial growth and substrate degradation, and at acquiring kinetic information
in order to improve the design and operation of TBB. Experiment works began by cultivating a mixed culture in a chemostat
reactor receiving artificial influent containing a mixture of benzene, toluene, and xylene (BTX), followed by using the enrichment
culture to degrade the individual BTX substrates under a particular salinity, which ranged 0–50 g l−1 in batch mode. Then, the measured concentrations of biomass and residual substrate versus time were analyzed with the microbial
kinetics; moreover, the obtained microbial kinetic constants under various salinities were modeled using noncompetitive inhibition
kinetics. For the three substrates the observed bacterial yields appeared to be decreased from 0.51–0.74 to 0.20–0.22 mg mg−1 and the maximum specific rate of substrate utilization,
declined from 0.25–0.42 to 0.07–0.11 h−1, as the salinity increased from 0 to 50 NaCl g l−1. The NaCl acted as noncompetitive inhibitor, where the modeling inhibitions of the coefficients, K
T(S), were 22.7–29.7 g l−1 for substrate degradation and K
T(μ), 13.0–19.0 g l−1, for biomass formation. The calculated ratios for the bacterial maintenance rate, m
S, to
further indicated that the percentage energy spent on maintenance increased from 19–24 to 86–91% as salinity level increased
from 0 to 50 g l−1. These results revealed that the bacterial growth was more inhibited than substrate degradation by the BTX oxidizers under
the tested salinity levels. The findings from this study demonstrate the potential of applying NaCl salt to control excessive
biomass formation in biotrickling filters. 相似文献
2.
Extracellular human granulocyte-macrophage colony stimulating factor (hGM-CSF) expression was studied under the control of
the GAP promoter in recombinant Pichia pastoris in a series of continuous culture runs (dilution rates from 0.025 to 0.2 h−1). The inlet feed concentration was also varied and the steady state biomass concentration increased proportionally demonstrating
efficient substrate utilization and constancy of the biomass yield coefficient (Yx/s) for a given dilution rate. The specific product formation rate (qP) showed a strong correlation with dilution rates demonstrating growth associated product formation of hGM-CSF. The volumetric
product concentration achieved at the highest feed concentration (4×) and a dilution rate of 0.2 h−1 was 82 mg l−1 which was 5-fold higher compared to the continuous culture run with 1× feed concentration at the lowest dilution rate thus
translating to a 40 fold increase in the volumetric productivity. The specific product yield (YP/X) increased slightly from 2 to 2.5 mg g−1, with increasing dilution rates, while it remained fairly invariant, for all feed concentrations demonstrating negligible
product degradation or feed back inhibition. The robust nature of this expression system would make it easily amenable to
scale up for industrial production. 相似文献
3.
Biodegradation of BTEX by a microbial consortium isolated from a closed municipal landfill was studied using respirometric
techniques. The kinetics of biodegradation were estimated from experimental oxygen uptake data using a nonlinear parameter
estimation technique. All of the six compounds were rapidly degraded by the microbial culture and no substrate inhibition
was observed at the concentration levels examined (200 mg L−1 as COD). Microbial growth and contaminant degradation were adequately described by the Monod equation. Considerable differences
were observed in the rates of BTEX biodegradation as seen from the estimates of the kinetic parameters. A three-fold variation
was seen in the values of the maximum specific growth rate, μmax. The highest value of μmax was 0.389 h−1 for p-xylene while o-xylene was characterized by a μmax value of 0.14 h−1, the lowest observed in this study. The half saturation coefficient, K
s, and the yield coefficient, Y, varied between 1.288–4.681 mg L−1 and 0.272–0.645 mg mg−1, respectively. Benzene and o-xylene exhibited higher resistance to biodegradation while toluene and p-xylene were rapidly degraded. Ethylbenzene and m-xylene were degraded at intermediate rates. In biodegradation experiments with a multiple substrate matrix, substrate depletion
was slower than in single substrate experiments, suggesting an inhibitory nature of substrate interaction.
Received 15 February 1998/ Accepted in revised form 5 July 1998 相似文献
4.
Predation by protozoa plays an important role in activated sludge. In this work, the kinetics for protozoan predation of active bacteria (XH), extracellular polymeric substances (EPS), and intracellular storage products (XSTO) are added into a previously expanded unified model that describes the dynamics of EPS, XSTO, and soluble microbial products (SMP). The new biomass growth–decay–predation model describes the biomass fractions, soluble organic components, and oxygen‐uptake rates considering EPS, XSTO, and predators during dynamic operating conditions in activated sludge. Model calibration using batch experimental data provides the new parameter values for predation processes and insights into mechanisms involving predators. The calibrated value of the maximum specific growth rate for the predators is much slower than for the bacteria, confirming that predators are relatively slow growers. However, the predators and bacteria have similar decay rates and dissolved oxygen affinities. Model testing with results independent of the calibration data shows two things. First, the model and calibrated parameters accurately simulate the independent results when predators are present. Second, eliminating predation by high salinity significantly lowers the OUR, and this is captured by the model. Biotechnol. Bioeng. 2010;105: 1021–1030. © 2009 Wiley Periodicals, Inc. 相似文献
5.
The kinetics of soluble microbial product (SMP) formation under substrate-sufficient conditions appear to exhibit different
patterns from substrate-limited cultures. However, energy spilling-associated SMP formation is not taken into account in the
existing kinetic models and classification of SMP. Based on the concepts of growth yield and energy uncoupling, a kinetic
model describing energy spilling-associated SMP formation in relation to the ratio of initial substrate concentration to initial
biomass concentration (S
0/X
0) was developed for substrate-sufficient batch culture of activated sludge, and was verified by experimental data. The specific
rate of energy spilling-associated SMP formation showed an increasing trend with the S
0/X
0 ratio up to its maximum value. The SMP productivity coefficient (α
p/e) was defined from the model on the basis of energy spilling-associated substrate consumption. Results revealed that less
than 5% of energy spilling-associated substrate consumption was converted into SMP.
Electronic Publication 相似文献
6.
The growth performance of malolactic fermenting bacteria Oenococcus oeni NCIMB 11648 and Lactobacillus brevis X2 was assessed in continuous culture. O. oeni grew at a dilution rate range of 0.007 to 0.052 h−1 in a mixture of 5:6 (g l−1) of glucose/fructose at an optimal pH of 4.5, and L. brevis X2 grew at 0.010 to 0.089 h−1 in 10 g l−1 glucose at an optimal pH of 5.5 in a simple and safe medium. The cell dry weight, substrate uptake and product formation
were monitored, as well as growth kinetics, yield parameters and fermentation balances were also evaluated under pH control
conditions. A comparison of growth characteristics of two strains was made, and this showed significantly different performance.
O. oeni has lower maximum specific growth rate (μmax=0.073 h−1), lower maximum cell productivity (Q
x
max=17.6 mg cell l−1 h−1), lower maximum biomass yield (Y
x/s
max=7.93 g cell mol−1 sugar) and higher maintenance coefficient (m
s=0.45 mmol−1 sugar g−1 cell h−1) as compared with L. brevis X2 (μmax=0.110 h−1; Q
x
max=93.2 g−1 cell mol−1 glucose; Y
x/s
max=22.3 g cell mol−1 glucose; m
s=0.21 mmol−1 glucose g−1 cell h−1). These data suggest a possible more productive strategy for their combined use in maturation of cider and wine. 相似文献
7.
Batch assays are currently used to study the kinetic behavior of microbial growth. However, it has been shown that the outcome
of batch experiments is greatly influenced by the initial ratio of substrate concentration (S
o) to biomass concentration (X
o). Substrate-sufficient batch culture is known to have mechanisms of spilling energy that lead to significant nongrowth-associated
substrate consumption, and the Monod equation is no longer appropriate. By incorporating substrate consumption associated
with energy spilling into the balance of the substrate oxidation reaction, a kinetic model for the observed specific substrate
consumption rate was developed for substrate-sufficient batch culture of activated sludge, and was further verified by experimental
data. It was demonstrated that the specific substrate consumption rate increased with the increase of the S
o/X
o ratio, and the majority of substrate was consumed through energy spilling at high S
o/X
o ratios. It appears that the S
o/X
o ratio is a key parameter in regulating metabolic pathways of microorganisms.
Received: 18 January 1999 / Received revision: 7 May 1999 / Accepted: 28 May 1999 相似文献
8.
In this study, the kinetic behaviors between n-butyl acetate and composite bead were investigated. Both microbial growth rate and biochemical reaction rate would be inhibited with increasing average inlet concentration. The order of the inhibitive effect, which resulted from increased average inlet concentration for four operation temperatures, was 30>35>40>25 °C. Both microbial growth rate and biochemical reaction rate would be enhanced and inhibited with increasing operation temperature in the operation temperature ranges of 25 to 30 and 30 to 40 °C, respectively. The enhancing and inhibitive effects resulting from increased operation temperature were the most pronounced at the average inlet concentration of 200 ppm. The values of maximum reaction rate V
m and half-saturation constant K
s ranged from 0.011 to 0.047 g C h−1 kg−1 packed material and from 19.30 to 62.40 ppm, respectively. The zero-order kinetic with the diffusion rate limitation could be regarded as the most adequate biochemical reaction kinetic model. The values of maximum elimination capacity ranged from 0.51 to 0.20 g C h−1 kg−1 packed material, and the optimal maximum elimination capacity of biofilter occurred at the operation temperature of 30 °C. 相似文献
9.
J R Kastner W J Jones R S Roberts 《Journal of industrial microbiology & biotechnology》1998,20(6):339-343
The kinetics of biomass formation, D-xylose utilization, and mixed substrate utilization were determined in a chemostat using the yeast Candida shehatae. The maximum growth rate of C. shehatae grown aerobically on D-xylose was 0.42 h−1 and the Monod constant, K
s, was 0.06 g L−1. The biomass yield, Y
{X/S}, ranged from 0.40 to 0.50 g g−1 over a dilution rate range of 0.2–0.3 h−1, when C. shehatae was grown on pure D-xylose. Mixtures of D-xylose and glucose (∼1 : 1) were simultaneously utilized over a dilution rate from 0.15 to 0.35 h−1 at pH 3.5 and 4.5, but pH 3.5 reduced μmax and reduced the dilution rate range over which D-xylose was utilized in the presence of glucose. At pH 4.5, μmax was not reduced with the mixed sugar feed and the overall or lumped K
s value was not significantly increased (0.058 g L−1
vs 0.06 g L−1), when compared to a pure D-xylose feed. Kinetic data indicate that C. shehatae is an excellent candidate for chemostat production of value added products from renewable carbon sources, since simultaneous
mixed substrate utilization was observed over a wide range of growth rates on a 1 : 1 mixture of glucose and D-xylose.
Received 21 August 1997/ Accepted in revised form 28 May 1998 相似文献
10.
A mathematical model is developed to describe the growth of multiple microbial species such as heterotrophs and autotrophs
in activated sludge system. Performance of a lab-scale sequencing batch reactor involving storage process is used to evaluate
the model. Results show that the model is appropriate for predicting the fate of major model components, i.e., chemical oxygen
demand, storage polymers (X
STO), volatile suspended solid (VSS), ammonia, and oxygen uptake rate (OUR). The influence of sludge retention time (SRT) on
reactor performance is analyzed by model simulation. The biomass components require different time periods from one to four
times of SRT to reach steady state. At an SRT of 20 days, the active bacteria (autotrophs and heterotrophs) constitute about
57% of the VSS; the remaining biomass is not active. The model established demonstrates its capacity of simulating the reactor
performance and getting insight in autotrophic and heterotrophic growth in complex activated sludge systems. 相似文献
11.
Decolourization of anaerobically digested and polyaluminium chloride treated distillery spentwash was studied in a fungal
stirred tank aerobic reactor without dilution of wastewater. Aspergillus niger isolate IITB-V8 was used as the fungal inoculum. The main objectives of the study were to optimize the stirrer speed for
achieving maximum decolourization and to determine the kinetic parameters. A mathematical model was developed to describe
the batch culture kinetics. Volumetric oxygen transfer coefficient (k
L
a) was obtained using dynamic method. The maximum specific growth rate and growth yield of fungus were determined using Logistic
equation and using Luedeking–Piret equation. 150 rpm was found to be optimum stirrer speed for overall decolourization of
87%. At the optimum stirrer speed, volumetric oxygen transfer coefficient (k
L
a) was 0.4957 min−1 and the maximum specific growth rate of fungus was 0.224 h−1. The values of yield coefficient (Y
x/s) and maintenance coefficient (m
s) were found to be 0.48 g cells (g substrate)−1 and 0.015 g substrate (g cells)−1 h−1. 相似文献
12.
ImGyu Byun JeungJin Park SoRa Park TaeHo Lee TaeJoo Park 《Biotechnology and Bioprocess Engineering》2008,13(1):96-101
Spent sulfidic caustic was applied to sulfur utilizing autotrophic denitrification as the simultaneous source of electron
donor and alkalinity. The two experiment set-up of upflow anoxic hybrid growth reactor (UAHGR) and upflow anoxic suspended
growth reactor (UASGR) was adopted and nitrate removals were similar in both reactors. Approximately 90% of the initial nitrate
was denitrified at nitrate loading rate of 0.15∼0.40 kgNO3
−/m3·d. The experimental stoichiometric ratio of sulfate production to nitrate removal was ranged from 1.5 to 2.1 mgSO4
2−/mgNO3
−. During the operation period, denaturing gradient gel electrophoresis (DGGE) analysis of polymerase chain reaction (PCR)-amplified
16S rDNA fragments for the sludge sample of both reactors showed the change of microbial communities. Thiobacillus denitrificans-like microorganism occupied 28.5% (18 clones) of the 63 clones by cloning the PCR products from the sludge sample of UAHGR.
Acidovorax avenae, which can reduce nitrate to nitrogen gas while oxidizing phenol (heterotrophic denitrifier), was also found in 7 clones
(11.1%). Although an organic carbon source was not added to the medium, a microorganism (Kaistella koreensis) capable of oxidizing organic compounds was found in 7 clones (11.1%). Therefore, the microbial community of spent sulfidic
caustic applied autotrophic denitrification process well corresponds to the substrate components of spent sulfidic caustic.
Through the batch cultivation of microorganisms in UAHGR, the microbial kinetic coefficients of spent sulfidic caustic applied
autotrophic denitrification were estimated to be μ
max
= 0.097 h−1, k
d
= 0.0021 h−1, K
s
= 200 mgNO3
−/L, and Y = 0.31 mgMLVSS/mgNO3
−. 相似文献
13.
The biokinetics of glucose metabolism were evaluated in Aeromonas hydrophila during growth in an anaerobic biosystem. After approx 34 h growth, A. hydrophila metabolized 5,000 mg glucose l−1 into the end-products ethanol, acetate, succinate and formate. The maximum growth rate, μ
m, half saturation coefficients, K
s, microbial yield coefficient, Y, cell mass decay rate coefficient, k
d, and substrate inhibition coefficient, K
si were 0.25 ± 0.03 h−1, 118 ± 31 mg glucose l−1, 0.12 μg DNA mg glucose−1, 0.01 h−1, and 3,108 ± 1,152 mg glucose l−1, respectively. These data were used to predict the performance of a continuous growth system with an influent glucose concentration
of 5,000 mg l−1. Results of the analysis suggest that A. hydrophila will metabolize glucose at greater than 95% efficiency when hydraulic retention times (HRTs) exceed 7 h, whereas the culture
is at risk of washing out at an HRT of 6.7 h. 相似文献
14.
Christian Oliveira Reinehr Jorge Alberto Vieira Costa 《World journal of microbiology & biotechnology》2006,22(9):937-943
Summary The cultivation of photosynthetic microorganisms such as the microalga Spirulina platensis can provide an alternative source of food. The water in Mangueira Lagoon (Rio Grande do Sul state, southern Brazil) has several required nutrients for the growth of Spirulina and could be added to culture medium to reduce the cost of producing S. platensis. Although little studied, repeated batch cultivation is a very useful technique because it has a better cost–benefit ratio than other cultivation methods. In a series of runs, we studied the influence of cell concentration, renewal rate and strain on the specific growth rate and biomass productivity of S. platensis during repeated batch cultivation, the runs taking place in 2-l Erlenmeyer flasks for 2160 h at 30 °C and a light intensity of 2500 lux under a 12 h photoperiod. The three factors studied had a significant (P < 0.05) effect on the results (specific growth rate and productivity). Using Zarrouk’s medium, the highest specific growth rate (μX) was 0.111 day−1 while the biomass productivity (P
X) was 0.0423 g l−1 day−1, while Mangueira Lagoon water supplemented with 10% Zarrouk’s medium gave μX = 0.113 day−1 and a productivity P
X = 0.0467 g l−1 day−1. These values were two to three times higher than the results obtained in batch cultivation, indicating that the repeated batch cultivation of S. platensis is attractive and convenient. 相似文献
15.
S. F. Baldia A. D. Evangelista E. V. Aralar A. E. Santiago 《Journal of applied phycology》2007,19(6):607-613
Phytoplankton supports fisheries and aquaculture production. Its vital role as food for aquatic animals, like mollusks, shrimp,
and fish cannot be overemphasized. Because of its contribution as a food source for fish, the growth kinetics of Microcystis aeruginosa, a dominant cyanobacterium in the lake, was studied. The regular occurrence of M. aeruginosa is experienced during the months of May to July or from September to November in Laguna de Bay, the largest freshwater lake
in the Philippines. M. aeruginosa was collected from Laguna de Bay, isolated, and established in axenic conditions. Data on the growth kinetic parameters for
nitrate-nitrogen and phosphate-phosphorus utilization by M. aeruginosa gave the following values: half-saturation constant (K
s
), 0.530 mg N. L−1 and 0.024 mg P. L−1 respectively; maximum growth rate (μ
max
), 0.671. d−1 and 0.668. d−1 respectively; maximum cell yield, 6.5 and 6.54 log, cells. ml−1 respectively; nutrient level for saturated growth yield, 8.71 mg N. L−1 and 0.22 mg P. L−1 respectively; and minimum cell quota (Q
0
), 2.82 pg N. cell−1 and 0.064 pg P. cell−1 respectively. The low K
s value and high maximum growth rate (μ
max
) for phosphorus by M. aeruginosa would suggest a high efficiency of phosphorus utilization. On the other hand, the high K
s
value for nitrogen indicated a low rate of uptake for this nutrient. 相似文献
16.
Derin Orhon Emine Ubay Cokgor Guclu Insel Ozlem Karahan Tugce Katipoglu 《Bioresource technology》2009,100(23):5678-5686
The study presented an evaluation of the effect of culture history (sludge age) on the growth kinetics of a mixed culture grown under aerobic conditions. It involved an experimental setup where a lab-scale sequencing batch reactor was operated at steady-state at two different sludge ages (θX) of 2 and 10 days. The system sustained a mixed culture fed with a synthetic substrate mainly consisting of peptone. The initial concentration of substrate COD was selected around 500 mg COD/L. Polyhydroxyalkanoate (PHA) storage occurred to a limited extent, around 30 mg COD/L for θX = 10 days and 15 mg COD/L for θX = 2 days. Evaluation of the experimental data based on calibration of two different models provided consistent and reliable evidence for a variable Monod kinetics where the maximum specific growth rate, was assessed as 6.1/day for θX = 2 days and 4.1/day for θX = 10 days. A similar variability was also applicable for the hydrolysis and storage kinetics. The rate of storage was significantly lower than the levels reported in the literature, exhibiting the ability of the microorganisms to regulate their metabolic mechanisms for adjusting the rate of microbial growth and storage competing for the same substrate. This adjustment evidently resulted in case-specific, variable kinetics both for microbial growth and substrate storage. 相似文献
17.
Biodegradation and kinetics of aerobic granules under high organic loading rates in sequencing batch reactor 总被引:1,自引:0,他引:1
Biodegradation, kinetics, and microbial diversity of aerobic granules were investigated under a high range of organic loading
rate 6.0 to 12.0 kg chemical oxygen demand (COD) m−3 day−1 in a sequencing batch reactor. The selection and enriching of different bacterial species under different organic loading
rates had an important effect on the characteristics and performance of the mature aerobic granules and caused the difference
on granular biodegradation and kinetic behaviors. Good granular characteristics and performance were presented at steady state
under various organic loading rates. Larger and denser aerobic granules were developed and stabilized at relatively higher
organic loading rates with decreased bioactivity in terms of specific oxygen utilization rate and specific growth rate (μ
overall) or solid retention time. The decrease of bioactivity was helpful to maintain granule stability under high organic loading
rates and improve reactor operation. The corresponding biokinetic coefficients of endogenous decay rate (k
d), observed yield (Y
obs), and theoretical yield (Y) were measured and calculated in this study. As the increase of organic loading rate, a decreased net sludge production (Y
obs) is associated with an increased solid retention time, while k
d and Y changed insignificantly and can be regarded as constants under different organic loading rates. 相似文献
18.
S. Thangminlal Vaiphei Gaurav Pandey K. J. Mukherjee 《Journal of industrial microbiology & biotechnology》2009,36(12):1453-1458
A series of continuous cultures was performed to understand the product formation kinetics of recombinant human interferon
gamma (rhIFN-γ) in Escherichia coli at different dilution rates ranging from 0.1 to 0.3 h−1 in different media. A T7 promoter-based vector was used for expression of IFN-γ in E. coli BL21 (DE3) cells. The recombinant protein was produced as inclusion bodies, thus allowing a rapid buildup of rhIFN-γ inside
the cell, with the specific product yield (Y
p/X
) reaching a maximum value of 182 mg g−1 dry cell weight (DCW). In all the media tested, the specific product formation rate (q
p
) was found to be strongly correlated with the specific growth rate (μ), demonstrating the growth-associated nature of product formation. The q
p
values show no significant decline with time postinduction, even though the recombinant protein has been over produced inside
the cell. The maximum q
p
level of 75.5 mg g−1 h−1 was achieved at the first hour of induction at the dilution rate of 0.3 h−1. Also, this correlation between q
p
and μ was not critically dependent on media composition, which would made it possible to grow cells in defined media in the growth
phase and then push up the specific growth rate just before induction by pulse addition of glucose and yeast extract. This
would ensure the twin objectives of high biomass and high specific productivities, leading to high volumetric product concentration. 相似文献
19.
The kinetic parameters Km and Vmax for urea uptake by Melosira italica were determined at 160 μeinsteins m−2 s−1 and in the dark. The transport systems showed an affinity for the substrate and a storing capacity in the dark (Km = 65.07 μM; Vmax = 2.18 nmoles 105 cells −1 h−1) greater than under 160 μE m−2 s −1 (Km = 111.2 μM; Vmax = 1.11 nmoles 105 cells−1 h−1). Similarly, a reduction in consumption rate of urea under increasing photon flux densities was observed. The use of an inhibitor
(potassium cyanide) indicated that the uptake process requires metabolic energy. That urea transport is more important in
darkness, may constitute a survival strategy in which this compound is utilized by cells mainly during heterotrophic growth. 相似文献
20.
David A. Lipson Russell K. Monson Steven K. Schmidt Michael N. Weintraub 《Biogeochemistry》2009,95(1):23-35
Soil microbial respiration is a critical component of the global carbon cycle, but it is uncertain how properties of microbes
affect this process. Previous studies have noted a thermodynamic trade-off between the rate and efficiency of growth in heterotrophic
organisms. Growth rate and yield determine the biomass-specific respiration rate of growing microbial populations, but these
traits have not previously been used to scale from microbial communities to ecosystems. Here we report seasonal variation
in microbial growth kinetics and temperature responses (Q10) in a coniferous forest soil, relate these properties to cultured and uncultured soil microbes, and model the effects of
shifting growth kinetics on soil heterotrophic respiration (Rh). Soil microbial communities from under-snow had higher growth rates and lower growth yields than the summer and fall communities
from exposed soils, causing higher biomass-specific respiration rates. Growth rate and yield were strongly negatively correlated.
Based on experiments using specific growth inhibitors, bacteria had higher growth rates and lower yields than fungi, overall,
suggesting a more important role for bacteria in determining Rh. The dominant bacteria from laboratory-incubated soil differed seasonally: faster-growing, cold-adapted Janthinobacterium species dominated in winter and slower-growing, mesophilic Burkholderia and Variovorax species dominated in summer. Modeled Rh was sensitive to microbial kinetics and Q10: a sixfold lower annual Rh resulted from using kinetic parameters from summer versus winter communities. Under the most realistic scenario using seasonally
changing communities, the model estimated Rh at 22.67 mol m−2 year−1, or 47.0% of annual total ecosystem respiration (Re) for this forest. 相似文献