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1.
C. Löser H. Seidel A. Zehnsdorf U. Stottmeister 《Applied microbiology and biotechnology》1998,49(5):631-636
Microbial hydrocarbon degradation in soil was studied during periodical aerobic/anaerobic switching and under purely aerobic
conditions by using a pilot-scale plant with diesel-fuel-contaminated sand. The system worked according to the percolation
principle with controlled circulation of process water and aeration. Periodical switching between 4 h of aerobic and 2 h of
anaerobic conditions was achieved by repeated saturation of the soil with water. Whatever the cultivation mode, less than
50% of the diesel was degraded after 650 h because the hydrocarbons were adsorbed. Contrary to expectations, aerobic/anaerobic
changes neither accelerated the rate of degradation nor reduced the residual hydrocarbon content of the soil. Obviously the
pollutant degradation rate was determined mainly by transport phenomena and less by the efficiency of microbial metabolism.
The total mass of oxygen consumed and carbon dioxide produced was greater under aerobic/anaerobic changing than under aerobic
conditions, although the mass of hydrocarbons degraded was nearly the same. As shown by an overall balance of microbial growth
and by a carbon balance, the growth yield coefficient was smaller during aerobic/anaerobic changes than under aerobic conditions.
Received: 25 November 1997 / Received revision: 15 January 1998 / Accepted: 18 January 1998 相似文献
2.
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
3.
Biodegradation of azo dyes in cocultures of anaerobic granular sludge with aerobic aromatic amine degrading enrichment cultures 总被引:6,自引:0,他引:6
N. C. G. Tan F. X. Prenafeta-Boldú J. L. Opsteeg G. Lettinga J. A. Field 《Applied microbiology and biotechnology》1999,51(6):865-871
A prerequisite for the mineralization (complete biodegradation) of many azo dyes is a combination of reductive and oxidative
steps. In this study, the biodegradation of two azo dyes, 4-phenylazophenol (4-PAP) and Mordant Yellow 10 (4-sulfophenylazo-salicylic
acid; MY10), was evaluated in batch experiments where anaerobic and aerobic conditions were integrated by exposing anaerobic
granular sludge to oxygen. Under these conditions, the azo dyes were reduced, resulting in a temporal accumulation of aromatic
amines. 4-Aminophenol (4-AP) and aniline were detected from the reduction of 4-PAP. 5-Aminosalicylic acid (5-ASA) and sulfanilic
acid (SA) were detected from the reduction of MY10. Subsequently, aniline was degraded further in the presence of oxygen by
the facultative aerobic bacteria present in the anaerobic granular sludge. 5-ASA and SA were also degraded, if inocula from
aerobic enrichment cultures were added to the batch experiments. Due to rapid autoxidation of 4-AP, no enrichment culture
could be established for this compound. The results of this study indicate that aerobic enrichment cultures developed on aromatic
amines combined with oxygen-tolerant anaerobic granular sludge can potentially be used to completely biodegrade azo dyes under
integrated anaerobic/aerobic conditions.
Received: 16 September 1998 / Received revision: 14 December 1998 / Accepted: 21 December 1998 相似文献
4.
Thiobacillus ferrooxidans was able to grow under anaerobic conditions on copper sulphide with ferric ion as the electron acceptor. The dissolution of
covellite under these conditions (68% after 35 days) was higher than values observed aerobically in cultures with similar
media composition and almost as high as under aerobic conditions without iron. From these results we propose a mechanism for
anaerobic bioleaching of covellite in the presence of ferric iron and speculate that it may occur in leach dumps where the
oxygen concentration is, as reported elsewhere, very low.
Received: 3 September 1996 / Received revision: 13 January 1997 / Accepted: 24 January 1997 相似文献
5.
M. Kudlich P. L. Bishop H.-J. Knackmuss A. Stolz 《Applied microbiology and biotechnology》1996,46(5-6):597-603
The naphthalenesulfonate-oxidizing bacterium Sphingomonas sp. BN6 was immobilized in calcium alginate. These beads were incubated under aerobic conditions in a medium with the sulfonated
azo dye, Mordant Yellow 3 (MY3), and glucose. The immobilized cells converted MY3, but only a marginal turnover of the dye
was found under these conditions with freely suspended cells of Sphingomonas sp. BN6. Under anaerobic conditions, suspended cells of Sphingomonas sp. BN6 reductively cleaved the azo bond of MY3 to 6-aminonaphthalene-2-sulfonate (6A2NS) and 5-aminosalicylate. The turnover
of MY3 by the immobilized cells under aerobic conditions resulted in the formation of more than equimolar amounts of 5-aminosalicylate,
but almost no (6A2NS) was detected. Cells of Sphingomonas sp. BN6 aerobically oxidize 6A2NS to 5-aminosalicylate. It was therefore concluded that the cells in the anaerobic center
of the alginate beads reduced MY3 to 6A2NS and 5-aminosalicylate and that 6A2NS was oxidized to 5-aminosalicylate by those
cells that were immobilized in the outer aerobic zones of the alginate beads. The presence of oxygen gradients within the
alginate beads was verified by using oxygen micro-electrodes. A coimmobilisate of Sphingomonas sp. BN6 with a 5-aminosalicylate degrading bacterium completely degraded MY3. The immobilized cells also converted the sulfonated
azo dyes Amaranth and Acid Red␣1.
Received: 6 May 1996 / Received revision: 6 August 1996 / Accepted: 12 August 1996 相似文献
6.
Bioreactor selection is important for maximising the productivity of recombinant organisms. In this paper a comparison is
made between growth and recombinant protein synthesis in three types of bioreactor containing a marine Vibrio capable of heterologous expression and secretion of the non-toxic B-subunit pentamer of Escherichia coli heat-labile enterotoxin, EtxB. The heterologous gene was located on the plasmid pMMB68. Resistance to carbenicillin was used
to select for plasmid-containing cells. In batch and continuous culture, volumetric productivities were highest when cells
were grown in the presence of carbenicillin. Without antibiotic selection, the highest volumetric productivity (9.4 mg EtxB−1 h−1) was observed in hollow-fibre bioreactors, and the production phase could be maintained for over 50 h. The highest specific
productivity under these conditions was found in batch culture, but the maximal production phase was only of 5 h duration.
In hollow-fibre reactors the type of fibre used significantly affected productivity, both with regards to the maintenance
of reactor integrity and by allowing passage of the recombinant toxoid through the selectively permeable membrane. Where contamination
of the product with carbenicillin is to be avoided, these bioreactors are superior to batch or continuous culture.
Received: 29 January 1997 / Received revision: 9 April 1997 / Accepted: 13 April 1997 相似文献
7.
S. Guillouet J. H. Choi C. K. Rha A. J. Sinskey 《Applied microbiology and biotechnology》1999,51(2):235-240
Although many studies have examined the influence of culture conditions on the production and composition of polysaccharides,
little is known about the factors influencing the quality of exopolysaccharides (EPS). In this work we studied the effect
of yeast extract on the production, composition and molecular weight of the EPS zooglan produced by Zoogloea ramigera 115SLR. This bacterium was grown on a new completely defined synthetic medium and on a medium containing yeast extract. Growth
and polysaccharide production performances were comparable on the two media with a glucose to exopolysaccharide conversion
yield of 35% (g/g). The polysaccharides produced on these two media have an identical composition but a different molecular
weight and molecular weight distribution. The yeast extract medium leads to a more homogeneous polysaccharide solution.
Received: 12 June 1998 / Received revision: 19 September 1998 / Accepted: 11 October 1998 相似文献
8.
The maximum growth rate of Saccharomyces cerevisiae ATCC 96581, adapted to fermentation of spent sulphite liquor (SSL), was 7 times higher in SSL of hardwood than the maximum
growth rate of bakers' yeast. ATCC 96581 was studied in the continuous fermentation of spruce hydrolysate without and with
cell recycling. Ethanol productivity by ATCC 96581 in continuous fermentation of an enzymatic hydrolysate of spruce was increased
4.6 times by employing cell recycling. On-line analysis of CO2, glucose and ethanol (using a microdialysis probe) was used to investigate the effect of fermentation pH on cell growth and
ethanol production, and to set the dilution rate. Cell growth in the spruce hydrolysates was strongly influenced by fermentation
pH. The fermentation was operated in continuous mode for 210 h and a theoretical ethanol yield on fermentable sugars was obtained.
Received: 25 May 1998 / Received revision: 11 August 1998 / Accepted: 12 August 1998 相似文献
9.
Respiratory and fermentative pathways co-exist to support growth and product formation in Pichia stipitis. This yeast grows rapidly without ethanol production under fully aerobic conditions, and it ferments glucose or xylose under
oxygen-limited conditions, but it stops growing within one generation under anaerobic conditions. Expression of Saccharomyces cerevisiaeURA1 (ScURA1) in P. stipitis enabled rapid anaerobic growth in minimal defined medium containing glucose when essential lipids were present. ScURA1 encodes a dihydroorotate dehydrogenase that uses fumarate as an alternative electron acceptor to confer anaerobic growth.
Initial P. stipitis transformants grew and produced 32 g/l ethanol from 78 g/l glucose. Cells produced even more ethanol faster following two
anaerobic serial subcultures. Control strains without ScURA1 were incapable of growing anaerobically and showed only limited fermentation. P. stipitis cells bearing ScURA1 were viable in anaerobic xylose medium for long periods, and supplemental glucose allowed cell growth, but xylose alone could
not support anaerobic growth even after serial anaerobic subculture on glucose. These data imply that P. stipitis can grow anaerobically using metabolic energy generated through fermentation but that it exhibits fundamental differences
in cofactor selection and electron transport with glucose and xylose metabolism. This is the first report of genetic engineering
to enable anaerobic growth of a eukaryote.
Received: 6 January 1998 / Received revision: 9 April 1998 / Accepted: 19 April 1998 相似文献
10.
The fermentation characteristics of the novel, thermotolerant, isolate Kluyveromyces marxianus var marxianus were determined to evaluate its aptitude for use in an ethanol production process. Sustainable growth was not observed under
anaerobic conditions, even in the presence of unsaturated fatty acid and sterol. A maximum ethanol concentration of 40 g L−1 was produced at 45°C, with an initial specific ethanol production rate of 1.7 g g−1 h−1. This was observed at ethanol concentrations below 8 g L−1 and under oxygen-limited conditions. The low ethanol tolerance and low growth under oxygen-limited conditions required for
ethanol production implied that a simple continuous process was not feasible with this yeast strain. Improved productivity
was achieved through recycling biomass into the fermenter, indicating that utilising an effective cell retention method such
as cell recycle or immobilisation, could lead to the development of a viable industrial process using this novel yeast strain.
Received 14 February 1998/ Accepted in revised form 19 May 1998 相似文献
11.
H. A. Kang S. J. Kim E.-S. Choi S.-K. Rhee B. H. Chung 《Applied microbiology and biotechnology》1998,50(2):187-192
When human parathyroid hormone (hPTH) is expressed as a secretory product in yeast, the main problem is the aberrant proteolytic
cleavage that reduces the yield of intact protein. To overcome this problem, we developed an hPTH expression system using a host strain in which the YAP3 gene encoding yeast aspartic protease 3 (YAP3) was disrupted. After 48 h of culture, most of the hPTH secreted by the yap3 disruptant remained intact, whereas more than 90% of the hPTH secreted by the wild-type strain was cleaved. When the authentic
hPTH was incubated in each of the culture supernatants of untransformed yap3 disruptant and wild-type strain, the proteolysis proceeded much more slowly in the culture supernatant of yap3 disruptant than in that of the wild type. The extent of hPTH proteolysis was also significantly reduced by the addition of
pepstatin A, a specific aspartic protease inhibitor. The results suggest that YAP3 is involved in the internal cleavage of
hPTH expressed in yeast. The correct processing of the intact hPTH secreted in the yap3 disruptant demonstrates that the yeast mutant lacking the YAP3 activity is a suitable host for the high-level expression
of intact hPTH.
Received: 8 December 1997 / Received last revision: 3 March 1998 / Accepted: 19 April 1998 相似文献
12.
Y. Shiba F. Fukui K. Ichikawa N. Serizawa H. Yoshikawa 《Applied microbiology and biotechnology》1998,50(1):34-41
In order to develop a production process for carboxypeptidase Y (CPY, yeast vacuolar protease) secreted by Saccharomyces cerevisiae KS58-2D, medium composition, culture conditions, and expression systems were investigated. We found that the addition of
histidine to thiamine-free medium, in which CPY production was almost negligible, raised the intracellular thiamine level,
resulting in the increase of CPY production. On the basis of the choice of an expression system that uses an inducible GAL10 promoter, reassessment of histidine concentration in the medium, and optimization of the pH level during cultivation (pH
6.5), active CPY was secreted in a quantity of over 400 mg/l, which was more than tenfold that higher than that previously
reported. The process developed could be easily scaled-up to industrial-scale fermentation.
Received: 16 January 1998 / Received revision: 16 February 1998 / Accepted: 27 February 1998 相似文献
13.
An autoselection system for increasing plasmid stability in Kluyveromyces lactis, based on the blockage of the pyrimidine de novo and salvage pathways, was investigated. In a manner analogous to that used in Saccharomyces cerevisiae, a putative “fur1” mutation was selected in a uraA K. lactis strain using 5-fluorouracil and 5-fluorocytosine plates. Survival of the mutant required expression of a plasmid-borne URA3 gene regardless of the culture medium employed, verifying the efficacy of this autoselection system in K. lactis. The expression of heterologous invertase, encoded by the S. cerevisiae SUC2 gene, was studied during long-term sequential batch cultures (70 generations) in complex yeast/peptone/glucose medium. The
fur1 mutant successfully retained the plasmid; invertase specific activity remained above 90% of the initial level. Furthermore,
no mutation reversion was observed. In contrast, for the control non-fur1 strain, only 4% of the cells retained the plasmid after 70 generations, and invertase specific activity dropped to less than
10% of the initial level. Experiments comparing growth and activity in different media indicated the potential for improving
productivity through medium enrichment using this autoselection system.
Received: 1 April 1997 / Received revision: 16 August 1997 / Accepted: 11 September 1997 相似文献
14.
A. Krastanov 《Applied microbiology and biotechnology》1997,47(5):476-481
A novel immobilized biocatalyst with invertase activity was prepared by adhesion of yeast cells to wool using glutaraldehyde.
Yeast cells could be immobilized onto wool by treating either the yeast cells or wool or both with glutaraldehyde. Immobilized
cells were not desorbed by washing with 1 M KCl or 0.1 M buffers, pH 3.5–7.5. The biocatalyst shows a maximum enzyme activity
when immobilized at pH 4.2–4.6 and 7.5–8.0. The immobilized biocatalyst was tested in a tubular fixed-bed reactor to investigate
its possible application for continuous full-scale sucrose hydrolysis. The influence of temperature, sugar concentration and
flow rate on the productivity of the reactor and on the specific productivity of the biocatalyst was studied. The system demonstrates
a very good productivity at a temperature of 70 °C and a sugar concentration of 2.0 M. The increase of the volume of the biocatalyst
layer exponentially increases the productivity. The productivity of the immobilized biocatalyst decreases no more than 50%
during 60 days of continuous work at 70 °C and 2.0 M sucrose, but during the first 30 days it remains constant. The cumulative
biocatalyst productivity for 60 days was 4.8 × 103kg inverted sucrose/kg biocatalyst. The biocatalyst was proved to be fully capable of continuous sucrose hydrolysis in fixed-bed
reactors.
Received: 8 November 1996 / Received revision: 31 January 1997 / Accepted: 31 January 1997 相似文献
15.
The stability of pKD1-based vectors in the yeast Kluyveromyces lactis was investigated during short- and long-term culture. The vectors carried an expression/secretion cassette consisting of
the Saccharomyces cerevisiaeSUC2 gene under the control of the S. cerevisiaeα-factor promoter and leader. The first set of vectors contained the entire pKD1 sequence linearized at either the unique
EcoRI or the unique SphI site of the pKD1 plasmid. During long-term sequential batch culture in selective medium with either vector, invertase activity
rapidly dropped while the plasmid-bearing population increased from 60% to 100%. This apparently contradictory behavior was due to structural instability. The
enzyme restriction patterns of recovered plasmid DNA retained the pKD1 band while the band containing the SUC2 cassette had decreased substantially in size. To overcome this structural instability, a vector carrying the pKD1 replication
origin and the cis-acting stability locus (lacking the inverted repeats) was employed in a pKD1+ (but otherwise isogenic) strain. With this plasmid, invertase activity remained constant (for at least 70 generations). While
the new vector was significantly more stable, initial invertase activity was substantially lower than that for the vectors
containing the full pKD1 sequence. Southern hybridization confirmed that this decrease was primarily due to reduced copy number.
The results indicate that full-pKD1 vectors may be preferred for batch culture, while partial-pKD1 vectors are more suitable
for long-term (e.g. fed-batch or continuous) culture.
Received: 24 June 1997 / Received revision: 14 November 1997 / Accepted: 29 November 1997 相似文献
16.
Optimization of agitation and aeration conditions for maximum virginiamycin production 总被引:3,自引:0,他引:3
To maximize the productivity of virginiamycin, which is a commercially important antibiotic as an animal feed additive, an
empirical approach was employed in the batch culture of Streptomyces virginiae. Here, the effects of dissolved oxygen (DO) concentration and agitation speed on the maximum cell concentration at the production
phase, as well as on the productivity of virginiamycin, were investigated. To maintain the DO concentration in the fermentor
at a certain level, either the agitation speed or the inlet oxygen concentration of the supply gas was manipulated. It was
found that increasing the agitation speed had a positive effect on the antibiotic productivity independent of the DO concentration.
The optimum DO concentration, agitation speed and addition of an autoregulator, virginiae butanolide C (VB-C), were determined
to maximize virginiamycin productivity. The optimal strategy was to start the cultivation at 450 rpm and to continue until
the DO concentration reached 80%. After reaching 80%, the DO concentration was maintained at this level by changing the agitation
speed, up to a maximum of 800 rpm. The addition of an optimal amount of the autoregulator VB-C in an experiment resulted in
the maximal production of virginiamycin M (399 mg/l), which was about 1.8-fold those obtained previously.
Received: 13 July 1998 / Received revision: 19 August 1998 / Accepted: 13 September 1998 相似文献
17.
Kajiwara S Aritomi T Suga K Ohtaguchi K Kobayashi O 《Applied microbiology and biotechnology》2000,53(5):568-574
The fermentation characteristics of Saccharomyces cerevisiae strains which overexpress a constitutive OLE1 gene were studied to clarify the relationship between the fatty acid composition of this yeast and its ethanol productivity.
The growth yield and ethanol productivity of these strains in the medium containing 15% dextrose at 10 °C were greater than
those of the control strains under both aerobic and anaerobic conditions but this difference was not observed under other
culture conditions. During repeated-batch fermentation, moreover, the growth yield and ethanol productivity of the wild-type
S. cerevisiae increased gradually and then were similar to those of the OLE1-overexpressing transformant in the last batch fermentation. However, the unsaturated fatty acid content (77.6%) of the wild-type
cells was lower than that (86.2%) of the OLE1-recombinant cells. These results suggested that other phenomena caused by the overexpression of the OLE1 gene, rather than high unsaturated fatty acid content, are essential to ethanol fermentation by this yeast.
Received: 11 June 1999 / Received last revision: 12 November 1999 / Accepted: 28 November 1999 相似文献
18.
Physiological aspects of continuous lactic acid fermentations at high dilution rates 总被引:1,自引:0,他引:1
U. Kulozik 《Applied microbiology and biotechnology》1998,49(5):506-510
The effects of the substrate conditions on the volumetric productivity of Lactobacillus helveticus at different cell densities up to 60 g l−1 in a continuous stirred-tank reactor with microfiltration to retain the biomass were investigated. At low dilution rates,
D, the steady-state volumetric productivity, r
p, gradually increased to a maximum at D = 1.2–1.5 h−1, because of reduced product inhibition. At higher D values, r
p unexpectedly decreased, although the substrate conditions further improved. The maxima of r
p at different cell densities coincided with a critical specific substrate utilization rate beyond which the cell metabolism
seems to be controlled through a catabolic modulator factor, and r
p decreases.
Received: 8 September 1997 / Received last revision: 31 December 1997 / Accepted: 2 January 1998 相似文献
19.
Daniel HJ Otto RT Binder M Reuss M Syldatk C 《Applied microbiology and biotechnology》1999,51(1):40-45
In order to produce sophorolipids from whey, thereby lowering the lactose content and biological oxygen demand, a two-step
batch cultivation process was developed including medium sterilization by filtration. In the first step, whey was sterilized
by a combination of crossflow and sterile filtration. Because the sophorolipid-producing yeast Candida bombicola ATCC 22214 was not able to use lactose as a carbon source directly, the oleaginous yeast Cryptococcus curvatus ATCC 20509 was grown on deproteinized whey concentrates (DWC). With 1: 1 diluted DWC-20, lactose was consumed as the carbon
source and biomass (24 g/l dry weight content) as well as single-cell oil (SCO, 10 g/l) were produced. The cultivation broth
was disrupted with a glass bead mill and it served as medium for growth (29 g cell dry mass/l) and sophorolipid production
(12 g/l) of the yeast C. bombicola.
Received: 29 July 1998 / Received revision: 5 October 1998 / Accepted: 11 October 1998 相似文献
20.
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