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1.
High-cell-density cultivation of microorganisms 总被引:29,自引:0,他引:29
High-cell-density cultivation (HCDC) is required to improve microbial biomass and product formation substantially. An overview
of HCDC is given for microorganisms including bacteria, archae and eukarya (yeasts). Problems encountered by HCDC and their
possible solutions are discussed. Improvements of strains, different types of bioreactors and cultivation strategies for successful
HCDC are described. Stirred-tank reactors with and without cell retention, a dialysis-membrane reactor, a gas-lift reactor
and a membrane cyclone reactor used for HCDC are outlined. Recently modified traditional feeding strategies and new ones are
included, in particular those for unlimited growth to very dense cultures. Emphasis is placed on robust fermentation control
because of the growing industrial interest in this field. Therefore, developments in the application of multivariate statistical
control, artificial neural networks, fuzzy control and knowledge-based supervision (expert systems) are summarized. Recent
advances using Escherichia coli– the pioneer organism for HCDC – are outlined.
Received: 20 October 1998 / Received revision: 18 December 1998 / Accepted: 21 December 1998 相似文献
2.
Pollutant degradation in biotrickling filters for waste air treatment is generally thought to occur only in the biofilm.
In two experiments with toluene degrading biotrickling filters, we show that suspended microorganisms in the recycle liquid
may substantially contribute to the overall pollutant removal. Two days after reactor start up, the overall toluene elimination
capacity reached a maximum of 125 g m−3 h−1, which was twice that found during prolonged operation. High biodegradation activity in the recycle liquid fully accounted
for this short-term peak of pollutant elimination. During steady-state operation, the toluene degradation in the recycle liquid
was 21% of the overall elimination capacity, although the amount of suspended biomass was only 1% of the amount of immobilized
biomass. The results suggest that biotrickling filter performance may be improved by selecting operating conditions allowing
for the development of an actively growing suspended culture.
Received: 16 June 1999 / Received revision: 17 November 1999 / Accepted: 15 December 1999 相似文献
3.
Bioremediation of pentachlorophenol-contaminated soil by bioaugmentation using activated soil 总被引:11,自引:0,他引:11
C. Barbeau L. Deschênes D. Karamanev Y. Comeau R. Samson 《Applied microbiology and biotechnology》1997,48(6):745-752
The use of an indigenous microbial consortium, pollutant-acclimated and attached to soil particles (activated soil), was
studied as a bioaugmentation method for the aerobic biodegradation of pentachlorophenol (PCP) in a contaminated soil. A 125-l
completely mixed soil slurry (10% soil) bioreactor was used to produce the activated soil biomass. Results showed that the
bioreactor was very effective in producing a PCP-acclimated biomass. Within 30 days, PCP-degrading bacteria increased from
105 cfu/g to 108 cfu/g soil. Mineralization of the PCP added to the reactor was demonstrated by chloride accumulation in solution. The soil-attached
consortium produced in the reactor was inhibited by PCP concentrations exceeding 250 mg/l. This high level of tolerance was
attributed to the beneficial effect of the soil particles. Once produced, the activated soil biomass remained active for 5
weeks at 20 °C and for up to 3 months when kept at 4 °C. The activated attached soil biomass produced in the completely mixed
soil slurry bioreactor, as well as a PCP-acclimated flocculent biomass obtained from an air-lift immobilized-soil bioreactor,
were used to stimulate the bioremediation of a PCP-impacted sandy soil, which had no indigenous PCP-degrading microorganisms.
Bioaugmentation of this soil by the acclimated biomass resulted in a 99% reduction (from 400 mg/kg to 5 mg/kg in 130 days)
in PCP concentration. The PCP degradation rates obtained with the activated soil biomass, produced either as a biomass attached
to soil particles or as a flocculent biomass, were similar.
Received: 31 March 1997 / Received revision: 22 July 1997 / Accepted: 25 August 1997 相似文献
4.
The ability of a photobioreactor to fix CO2 was evaluated with the thermophilic cyanobacterium, Synechocystis aquatilis SI-2. The reactor consisted of three to five flat plates of transparent acrylic plastic standing upright and in parallel
and giving a 0.015-m light path. The reactor was 0.8 m high and 1 m long with 9 l working volume. The effects of the orientation
of the vertical bioreactor, distance between the plates, and culture temperature on the productivity of biomass were investigated
during the summer of 1998 in Kamaishi (39°N, 142°E), Japan. When the illuminated surface reactor was placed in an east–west-facing
orientation, the biomass productivity was roughly 1.4-fold higher than that obtained in a north–south-facing orientation,
because the former received more solar energy than the latter. The productivity based on the overall land area was the same
for plates set either 0.25 m or 0.5 m apart. However, the volumetric productivity of the reactor in which the plates were
set 0.25 m apart was lower than that when the plates were set 0.5 m apart, since the former plates received relatively lower
solar irradiation because of severe mutual shading. When the culture temperature was maintained in its optimal range (37–43 °C),
the productivity was 50% greater than that obtained in a culture at ambient temperature (20–44 °C). The biomass productivity
and CO2 fixation rate were investigated under various experimental conditions. The maximum rate of 53 g CO2 m−2 day−1 was achieved in the temperature-regulated culture with the reactor set in an east–west-facing orientation, the distance between
plates being 0.25 m.
Received: 6 may 1999 / Received revision: 14 June 1999 / Accepted 5 July 1999 相似文献
5.
J. Benitez J. Beltran-Heredia J. Torregrosa J. L. Acero V. Cercas 《Applied microbiology and biotechnology》1997,47(2):185-188
The degradation of olive mill wastewater by aerobic microorganisms has been investigated in a batch reactor, by conducting
experiments where the initial concentration of organic matter, quantified by the chemical oxygen demand, and the initial biomass
were varied. The evolution of the chemical oxygen demand, biomass and the total contents of phenolic and aromatic compounds
were followed through each experiment. According to the Contois model, a kinetic expression for the substrate utilization
rate is derived, and its biokinetic constants are evaluated. This final predicted equation agrees well with all the experimental
data.
Received: 12 June 1996 / Received revision: 11 September 1996 / Accepted: 13 September 1996 相似文献
6.
J. H. de Best A. Hage H. J. Doddema D. B. Janssen W. Harder 《Applied microbiology and biotechnology》1999,51(2):277-283
A methanogenic mixed population in a packed-bed reactor completely transformed 1,1,1-trichloroethane (10 μM) to chloroethane
by a cometabolic process. Chloroethane was not further transformed. Acetate and methanol served as electron donors. Complete
transformation of 1,1,1-trichloroethane to chloroethane only occurred when sufficient electron donor was fed into the reactor.
Otherwise, besides chloroethane, 1,1-dichloroethane was also found as a product. The products of 1,1,1-trichloroethane transformation
also depended on the type of electron donor present. With acetate, the degree of dechlorination was higher, i.e. more 1,1,1-trichloroethane
was transformed to chloroethane than with methanol. In an enrichment culture obtained from the reactor contents, 1,1,1-trichloroethane
was only transformed to 1,1-dichloroethane and was not further metabolized. Methanol, acetate, formate, ethanol, 2-propanol,
trimethylamine and H2, but not dimethylamine and methylamine, served as electron donors for 1,1,1-trichloroethane transformation by this enrichment
culture. Both nitrate and nitrite inhibited 1,1,1-trichloroethane transformation; while nitrate completely inhibited 1,1,1-trichloroethane
dechlorination, some conversion did occur in the presence of nitrite. The product(s) of this conversion remain unknown, since
no chlorinated hydrocarbons were detected.
Received: 19 June 1998 / Received revision: 14 September 1998 / Accepted: 17 September 1998 相似文献
7.
E. Kostyál M. Borsányi L. Rigottier-Gois M. S. Salkinoja-Salonen 《Applied microbiology and biotechnology》1998,50(5):612-622
The dechlorinating and genotoxicity-removing activities of nitrifying fluidized-bed reactor biomass towards chlorinated organic
compounds in water were shown at level below 1 ppm. The removal rates of adsorbable organic halogens were 200 μg Cl (g VS
day)−1 for chlorinated humic ground water and 50 μyg Cl (g VS day)−1 for chlorinated lake water when studied in batch mode. In a sequenced batch mode the removal rates μg Cl (g VS day)−1] were 2000 from chlorohumus, 1400–1800 from chlorophenols in chlorinated ground water, and 430–720 from chlorohumus in chlorinated
lake water. Genotoxicity was removed to a large extent (60%–80%) from the chlorinated waters upon incubation with nitrifying
reactor biomass. 2,6-Di-, 2,4,6-tri and 2,3,4,6-tetrachlorophenols competed with chlorinated water organohalogens for dechlorination.
The dechlorination of chlorophenols and chlorohumus required no ammonia and was not prevented by inhibitors of ammonia oxidation,
nitrapyrin, parathion, sodium diethyldithiocarbamate, or allylthiourea. Electron microscopical inspection of the biomass showed
the dominance of clusters of bacteria resembling known nitrifying species, Nitrosomonas, Nitrobacter, and Nitrosospira. This was supported by polymerase chain reaction amplification of the biomass DNA with four different primers, revealing
the presence of 16S rDNA sequences assignable to the same species. The most intensive band obtained with the Nitroso4E primer
was shown to be closely related to Nitrosomonas europaea by restriction analysis.
Received: 27 March 1998 / Received revision: 30 July 1998 / Accepted: 31 July 1998 相似文献
8.
Carbon isotope fractionation between diet and bioapatite in ungulate mammals and implications for ecological and paleoecological studies 总被引:16,自引:0,他引:16
The isotope enrichment ɛ* of 13C between tooth enamel of large ruminant mammals and their diet is 14.1 ± 0.5‰. This value was obtained by analyzing both
the dental enamel of a variety of wild and captive mammals and the vegetation that comprised their foodstuffs. This isotope
enrichment factor applies to a wide variety of ruminant mammals. Non-ruminant ungulates have a similar isotope enrichment,
although our data cannot determine if it is significantly different. We also found a 13C isotope enrichment ɛ* of 3.1 ± 0.7‰ for horn relative to diet, and 11.1 ± 0.8‰ for enamel relative to horn for ruminant
mammals. Tooth enamel is a faithful recorder of diet. Its isotopic composition can be used to track changes in the isotopic
composition of the atmosphere, determine the fraction of C3 or C4 biomass in diets of modern or fossil mammals, distinguish between mammals using different subpathways of C4 photosynthesis,and identify those mammals whose diet is derived from closed-canopy habitats.
Received: 1 July 1998 / Accepted: 9 February 1999 相似文献
9.
Dialysis cultures 总被引:8,自引:0,他引:8
Dialysis techniques are discussed as a means for effective removal of low-molecular-mass components from fermentation broth
to reach high cell density. Reactor systems and process strategies, the relevant properties of membranes and examples for
high-density fermentation with dialysis, and problems related to scale-up are addressed. The dialysis technique has turned
out to be very efficient and reliable for obtaining high cell densities. As in dialysis processes the membranes are not perfused,
membrane clogging is not a problem as it is for micro- and ultrafiltration. By applying a “nutrient-split” feeding strategy,
the loss of nutrients can be avoided and the medium is used very efficiently. The potential of dialysis cultures is demonstrated
on the laboratory scale in a membrane dialysis reactor with an integrated membrane and in reactor systems with an external
dialysis loop. In dialysis cultures with different microorganisms (Staphylococci, Escherichia coli, extremophilic microorganisms, Lactobacilli) the cell densities achieved were up to 30 times higher than those of other fermentation methods. The technique enables high
cell densities to be attained without time-consuming medium optimization. For animal cell cultures the concept of a fixed
bed coupled with dialysis proved to be very effective.
Received: 24 March 1998 / Received revision: 18 June 1998 / Accepted: 19 June 1998 相似文献
10.
M. Wenk T. Baumgartner J. Dobovšek T. Fuchs J. Kucsera J. Zopfi G. Stucki 《Applied microbiology and biotechnology》1998,49(5):624-630
The evaluation of pesticide-mineralising microorganisms to clean-up contaminated soils was studied with the widely applied
and easily detectable compound atrazine, which is rapidly mineralised by several microorganisms including the Pseudomonas sp. strain Yaya 6. The rate of atrazine removal was proportional to the water content of the soil and the amount of bacteria
added to the soil. In soil slurry, 6 mg atrazine kg soil−1 was eliminated within 1 day after application of 0.3 g dry weight inoculant biomass kg soil−1 and within 5 days when 0.003 g kg soil−1 was used. In partially saturated soil (60% of the maximal water-holding capacity) 15 mg atrazine kg soil−1 was eliminated within 2 days by 1 g biomass kg soil−1 and within 25 days when 0.01 g biomass kg soil−1 was used. In unsaturated soil, about 60% [U-ring-14C]atrazine was converted to 14CO2 within 14 days. Atrazine was very efficiently removed by the inoculant biomass, not only in soil that was freshly contaminated
but also in soil aged with atrazine for up to 260 days. The bacteria exposed to atrazine in unsaturated sterile soil were
still active after a starvation period of 240 days: 15 mg newly added atrazine kg soil−1 was eliminated within 5 days.
Received: 31 October 1997 / Received revision: 16 January 1998 / Accepted: 18 January 1998 相似文献
11.
Continuous production of lactic acid from lactose has been carried out in a stirred-tank reactor with non-growing Lactobacillus helveticus entrapped in calcium alginate beads. A considerably longer operation half-life was obtained in a continuously operated reactor
than in a batch-operated reactor. It is possible to simulate the action of entrapped non-growing cells on the basis of information
from diffusion and kinetic experiments with suspended free cells. The simulation fit the experimental data over a broad range
of substrate concentrations if the specific lactic acid production rate, q
P, was used as a variable parameter in the model. The dynamic mathematical model used is divided into three parts: the reactor
model, which describes the mass balance in a continuously operated stirred-tank reactor with immobilized biomass, the mass-transfer
model including both external diffusion and internal mass transfer, and the kinetic model for uptake of substrate on the basis
of a Michaelis-Menten-type mechanism. From kinetic data obtained for free biomass experiments it was found, with the use of
non-linear parameter estimation techniques, that the conversion rate of lactose by L. helveticus followed a Michaelis-Menten-type mechanism with K
S at half-saturation=0.22±0.01 g/l. The maximum specific lactose uptake rate for growing cells, q
S,max, varied between 4.32±0.02 g lactose g cells-1 h-1 and 4.89 ±0.02 g lactose g cells-1 h-1. The initial specific lactose uptake rate for non-growing cells, q
S,0, was found to be approximately 40% of the maximum specific lactose uptake rate for growing cells.
Received: 4 October 1995/Received last revision: 23 April 1996/Accepted: 29 April 1996 相似文献
12.
It is critical that an inexpensive electron- donor/carbon-source be found for selenium bioremedia-tion using the selenate-respiring
bacterium, Thauera selenatis. Since acetate is a preferred substrate for growth of this organism, a method was developed for fermenting the lactose in
whey to large amounts of acetate. Indigenous whey microorganisms fermented the whey lactose in this manner when grown in continuous
culture at a very slow dilution rate (D = 0.05 h−1). The successful use of the fermented whey lactose as the carbon-source/electron-donor feed for a laboratory-scale selenium-bioremediation
reactor system, inoculated with T. selenatis, treating selenium-contaminated drainage water was also demonstrated. Selenium oxyanions and nitrate were reduced by 98%.
Received: 30 October 1998 / Received revision: 26 January 1999 / Accepted: 5 February 1999 相似文献
13.
Two coals of different rank, mined in Russia, were treated by an anaerobic methanogenic enrichment culture. The addition
of alkaline enclosing rock to the lower-rank coal increased the pH of the incubation medium and methane production above that
of the higher-rank coal with addition of its enclosing rock. This effect was accompanied by the leaching of cations from the
incubation medium. The coal was processed without a preliminary chemical treatment in a two-stage aerobic/anaerobic bioreactor
containing an anaerobic methanogenic granulated enrichment culture.
Received: 15 January 1998 / Received revision: 2 October 1998 / Accepted: 2 October 1998 相似文献
14.
A Konopka T Zakharova L Oliver E Paseuth R F Turco 《Journal of industrial microbiology & biotechnology》1998,20(3-4):232-237
The transition in physiological state was investigated between a carbon-limited chemostat population and microbes growing
very slowly in a biomass recycle reactor. The mixed microbial population was metabolizing a mixture of biopolymers and linear
alkylbenzene sulfonate, formulated to represent the organic load in graywater. Biomass increased 30-fold during the first
14 days after a shift from chemostat to biomass recycle mode. The ratios of ATP and RNA to cell protein decreased over the
first days but then remained constant. The specific rate of CO2 production by microbes in the reactor decreased 6-fold within 24 h after the shift, and respiratory potentials declined 2–3
fold during the first 7 days. Whereas chemostat cultures used equal proportions of organic carbon substrate for catabolism
and anabolism, the proportion of organic substrate oxidized to CO2 rose from 62 to 82% over the first 8 days in a biomass recycle reactor, and eventually reached 100% as this reactor population
exhibited no net growth. Biomass recycle populations removed from the system and subjected to a nutritional shift-up did not
immediately initiate exponential growth. The physiological state of cells in the biomass recycle reactor may be distinct from
those grown in batch or continuous culture, or from starved cells.
Received 02 June 1997/ Accepted in revised form 20 February 1998 相似文献
15.
A. B. Więckowski G. P. Słowik J. A. Gąsiorek P. Gąsiorek F. Domka A. Perkowska 《Applied microbiology and biotechnology》1999,52(1):96-98
A comparison of iron-sulfur proteins obtained from Thiobacillus ferrooxidans was carried out. The microorganisms were grown on iron(II)- or sulfur-containing nutrients. In both cases different, broad
elctron paramagnetic resonance (EPR) lines, originating from an iron(III) compound, were detected. Additional EPR lines of
tetrahedral iron(III) and free radicals were observed. The UV spectra of these compounds also differ.
Received: 15 July 1998 / Received revision: 8 October 1998 / Accepted: 16 October 1998 相似文献
16.
Q. Hu N. Kurano M. Kawachi I. Iwasaki S. Miyachi 《Applied microbiology and biotechnology》1998,49(6):655-662
To test the feasibility of CO2 remediation by microalgal photosynthesis, a modified type of flat-plate photobioreactor [Hu et al. (1996) Biotechnol Bioeng 51:51–60] has been designed for cultivation of a high-CO2-tolerant unicellular green alga Chlorococcum littorale. The modified reactor has a narrow light path in which intensive turbulent flow is provided by streaming compressed air through
perforated tubing into the culture suspension. The length of the reactor light path was optimized for the productivity of
biomass. The interrelationship between cell density and productivity, as affected by incident light intensity, was quantitatively
assessed. Cellular ultrastructural and biochemical changes in response to ultrahigh cell density were investigated. The potential
of biomass production under extremely high CO2 concentrations was also evaluated. By growing C. littorale cells in this reactor, a CO2 fixation rate of 16.7 g CO2 l−1 24 h−1 (or 200.4 g CO2 m−2 24 h−1) could readily be sustained at a light intensity of 2000 μmol m−2 s−1 at 25 °C, and an ultrahigh cell density of well over 80 g l−1 could be maintained by daily replacing the culture medium.
Received: 20 October 1997 / Received revision: 19 December 1997 / Accepted: 24 January 1998 相似文献
17.
Extremophiles as a source of novel enzymes for industrial application 总被引:33,自引:0,他引:33
F. Niehaus C. Bertoldo M. Kähler G. Antranikian 《Applied microbiology and biotechnology》1999,51(6):711-729
Extremophilic microorganisms are adapted to survive in ecological niches such as at high temperatures, extremes of pH, high
salt concentrations and high pressure. These microorganisms produce unique biocatalysts that function under extreme conditions
comparable to those prevailing in various industrial processes. Some of the enzymes from extremophiles have already been purified
and their genes successfully cloned in mesophilic hosts. In this review we will briefly discuss the biotechnological significance
of extreme thermophilic (optimal growth 70–80 °C) and hyperthermophilic (optimal growth 85–100 °C) archaea and bacteria. In
particular, we will focus on selected extracellular-polymer-degrading enzymes, such as amylases, pullulanases, cyclodextrin
glycosyltransferases, cellulases, xylanases, chitinases, proteinases and other enzymes such as esterases, glucose isomerases,
alcohol dehydrogenases and DNA-modifying enzymes with potential use in food, chemical and pharmaceutical industries and in
environmental biotechnology.
Received: 14 August 1998 / Received revision: 17 February 1999 / Accepted: 19 February 1999 相似文献
18.
Chloroaromatic compounds are xenobiotics that cause great concern. The degradation of a model molecule, 3,4-dichlorobenzoate
(3,4-DCB), was studied using three aerobic (AE)-anaerobic (AN) biofilm reactor systems: a coupled aerobic-anaerobic recycle
biofilm reactor (CAR) system, an in-series anaerobic-aerobic biofilm reactor (SAR) system; and an independent aerobic and
anaerobic biofilm reactor (IAR) system. In all three systems the inlet substrate concentration was 2.0 g/l and the dilution
rates ranged from 0.045 to 0.142 per hour. The results show that the degradation efficiency of the CAR system (expressed as
dechlorination and xenobiotic disappearance efficiencies, and biomass yield), was higher at all dilution rates tested than
in both SAR and IAR systems. Moreover, dechlorination and xenobiotic disappearance efficiencies for resting suspended aerobic
and anaerobic cells or mixed aerobic-anaerobic growing cells under anaerobic conditions were higher than under aerobic conditions.
These results suggest that a “cooperative metabolism” between aerobic and anaerobic bacteria (caused by an exchange of cells
and metabolites between AE and AN reactors) in the CAR system overcame the metabolic and kinetic limitations of aerobic and
anaerobic bacteria in the AE and AN reactors of IAR and SAR systems. Therefore, the degradation efficiency of persistent and
recalcitrant chloroaromatic xenobiotic compounds could be enhanced by using a CAR system.
Received: 1 March 1999 / Received revision: 11 May 1999 / Accepted: 16 May 1999 相似文献
19.
K. Hayakawa Y. Ueno S. Kawamura T. Kato R. Hayashi 《Applied microbiology and biotechnology》1998,50(4):415-418
In order to test the possibility of utilizing high pressure in bioscience and biotechnology, a simple method for high-pressure
generation and its use for microbial inactivation have been studied. When a pressure vessel was filled with water, sealed
tightly and cooled to sub-zero temperatures, high pressure was generated in the vessel. The pressure generation was 60 MPa
at −5 °C, 103 MPa at −10 °C, and 140 MPa at −15 °C, −20 °C, and −22 °C. The high pressure generated inactivated microorganisms
effectively: yeasts (Saccharomyces cerevisiae and Zygosaccharomyces rouxii), bacteria (Lactobacillus brevis and Eschericia coli), and fungi (Aspergillus niger and Aspergillus oryzae) were completely inactivated when stored in sealed vessels −20 °C for 24 h. However, Staphylococcus aureus was only partly inactivated under the same conditions. This method opens up a new application of high pressure for storing,
transporting, and sterilizing of foods and biological materials.
Received: 28 July 1997 / Received last revision: 12 June 1998 / Accepted: 19 June 1998 相似文献
20.
The influence of low temperature (5–29 °C) on the methanogenic activity of non-adapted digested sewage sludge and on temperature/leachate-adapted
biomass was assayed by using municipal landfill leachate, intermediates of anaerobic degradation (propionate) and methane
precursors (acetate, H2/CO2) as substrates. The temperature dependence of methanogenic activity could be described by Arrhenius-derived models. However,
both substrate and adaptation affected the temperature dependence. The adaptation of biomass in a leachate-fed upflow anaerobic
sludge-blanket reactor at approximately 20 °C for 4 months resulted in a sevenfold and fivefold increase of methanogenic activity
at 11 °C and 22 °C respectively. Both acetate and H2/CO2 were methanized even at 5 °C. At 22 °C, methanogenic activities (acetate 4.8–84 mM) were 1.6–5.2 times higher than those
at 11 °C. The half-velocity constant (K
s) of acetate utilization at 11 °C was one-third of that at 22 °C while a similar K
i was obtained at both temperatures. With propionate (1.1–5.5 mM) as substrate, meth‐anogenic activities at 11 °C were half
those at 22 °C. Furthermore, the residual concentration of the substrates was not dependent on temperature. The results suggest
that the adaptation of biomass enables the achievement of a high treatment capacity in the anaerobic process even under psychrophilic
conditions.
Received: 23 December 1996 / Received last revision: 18 June 1997 / Accepted: 23 June 1997 相似文献