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1.
A flocculent Saccharomyces cerevisiae strain with the ability to express both the LAC4 (coding for β-galactosidase) and LAC12 (coding for lactose permease) genes of Kluyveromyces marxianus was constructed. This recombinant strain is not only able to grow on lactose, but it can also ferment this substrate. To
our knowledge this is the first time that a recombinant S. cervisiae has been found to ferment lactose in a way comparable to that of the existing lactose-fermenting yeast strains. Moreover,
the flocculating capacity of the strain used in this work gives the process several advantages. On the one hand, it allows
for operation in a continuous mode at high cell concentration, thus increasing the system's overall productivity; on the other
hand, the biomass concentration in the effluent is reduced, thus decreasing product separation/purification costs.
Received: 2 October 1998 / Received revision: 15 January 1999 / Accepted: 17 January 1999 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.
The agaric basidiomycete Clitocybula dusenii was used for the production of the extracellular ligninolytic enzyme, manganese (Mn) peroxidase. An immobilization technique
is described using cellulose and polypropylene as carrier for the fungal mycelium. High amounts of Mn peroxidase were obtained
with agitated cultures of immobilized fungus (up to 3,000 U l−1) while the biomass was recovered and used for further production cycles. Purification of Mn peroxidase revealed the existence
of two forms: MnP1 (molecular mass 43 kDa, pI 4.5) and MnP2 (42 kDa, pI 3.8).
Received: 30 July 1999 / Received revision: 1 December 1999 / Accepted: 3 December 1999 相似文献
4.
Zn biosorption by Rhizopus arrhizus and other fungi 总被引:1,自引:0,他引:1
J. L. Zhou 《Applied microbiology and biotechnology》1999,51(5):686-693
Biosorption of zinc ions by inactivated fungal mycelia was studied. Of the six fungal species, Rhizopus arrhizus, Mucor racemosus, Mycotypha africana, Aspergillus nidulans, Aspergillus niger and Schizosaccharomyces pombe, R. arrhizus exhibited the highest capacity (Q
max = 213 μmol g−1 dry weight). Further experiments with different cellular fractions of R. arrhizus showed that Zn was predominantly bound to cell-wall chitin and chitosan (Q
max = 312 μmol g−1 dry weight). Adsorption data were best modelled by the Langmuir isotherm, although they can be modelled by the Freundlich
equation as well at relatively low aqueous concentrations. Biosorption generally decreased with increase in biosorbent particle
size and its concentration. Low pH reduced Zn sorption, because of the strong competition from hydrogen ions for binding sites
on fungi. The presence of ligands reduced metal uptake, chiefly by forming metal complexes of a less biosorbable nature.
Received: 2 November 1998 / Received revision: 12 January 1999 / Accepted: 17 January 1999 相似文献
5.
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
6.
Culture conditions for the fermentative production of β-poly(l-malate) (PMLA) by microplasmodia of Physarum polycephalum were investigated and optimized. Optimal production was achieved in the presence of CaCO3. For 1.5% (w/v) d-glucose, 1% bactotryptone and 1% CaCO3, a maximum of 1.7 g PMLA/l was secreted in 3 days. For 4.5% glucose and otherwise the same conditions, 2.7 g PMLA/l was produced
in 6 days. The contribution of carbonate was inhibited by avidin. PMLA and biomass production were not strictly coupled: PMLA
was also synthesized at the beginning of the stationary phase. At pH 5.5 PMLA production was twice that at pH 4.0, while biomass
was not changed. Optimal temperatures were 24–28 °C.
Received: 12 November 1998 / Received revision: 10 February 1999 / Accepted: 12 February 1999 相似文献
7.
In this work, the effect of the feeding strategy in Zymomonas mobilis CP4 fed-batch fermentations on the final biomass and ethanol concentrations was studied. Highest glucose yields to biomass
(0.018 g/g) and to ethanol (0.188 g/g) were obtained in fed-batch fermentations carried out using different feeding rates
with a glucose concentration in the feed equal to 100 g/l. Lower values (0.0102 g biomass/g glucose and 0.085 g ethanol/g
glucose) were obtained when glucose accumulated to levels higher than 60 g/l. On the other hand, the highest biomass (5 g/l)
and ethanol (39 g/l) concentrations were obtained using a glucose concentration in the feed equal to 220 g/l and exponentially
varied feeding rates. Experimental data were used to validate the mathematical model of the system. The prediction errors
of the model are 0.39, 14.36 and 3.24 g/l for the biomass, glucose and ethanol concentrations, respectively. Due to the complex
relationship for describing the specific growth rate, a fed-batch culture in which glucose concentration is constant would
not optimize the process.
Received: 30 November 1999 / Received revision: 24 March 2000 / Accepted: 7 April 2000 相似文献
8.
J. M. Obón J. R. Maiquez M. Cánovas H.-P. Kleber J. L. Iborra 《Applied microbiology and biotechnology》1999,51(6):760-764
The use of a biological procedure for l-carnitine production as an alternative to chemical methods must be accompanied by an efficient and highly productive reaction
system. Continuous l-carnitine production from crotonobetaine was studied in a cell-recycle reactor with Escherichia coli O44 K74 as biocatalyst. This bioreactor, running under the optimum medium composition (25 mM fumarate, 5 g/l peptone), was
able to reach a high cell density (26 g dry weight/l) and therefore to obtain high productivity values (6.2 g l-carnitine l−1 h−1). This process showed its feasibility for industrial l-carnitine production. In addition, resting cells maintained in continuous operation, with crotonobetaine as the only medium
component, kept their biocatalytic capacity for 4 days, but the biotransformation capacity decreased progressively when this
particular method of cultivation was used.
Received: 10 December 1998 / Received revision: 19 February 1999 / Accepted: 20 February 1999 相似文献
9.
Industrial 20-m3-scale and laboratory-scale aerobic fed-batch processes with Escherichia coli were compared. In the large-scale process the observed overall biomass yield was reduced by 12% at a cell density of 33 g/l
and formate accumulated to 50 mg/l during the later constant-feeding stage of the process. Though the dissolved oxygen signal
did not show any oxygen limitation, it is proposed that the lowered yield and the formate accumulation are caused by mixed-acid
fermentation in local zones where a high glucose concentration induced oxygen limitation. The hypothesis was further investigated
in a scale-down reactor with a controlled oxygen-limitation compartment. In this scale-down reactor similar results were obtained:
i.e. an observed yield lowered by 12% and formate accumulation to 238 mg/l. The dynamics of glucose uptake and mixed-acid
product formation (acetate, formate, d-lactate, succinate and ethanol) were investigated within the 54 s of passage time through the oxygen-limited compartment.
Of these, all except succinate and ethanol were formed; however, the products were re-assimilated in the oxygen-sufficient
reactor compartment. Formate was less readily assimilated, which accounts for its accumulation. The total volume of the induced-oxygen-limited
zones was estimated to be 10% of the whole liquid volume in the large bioreactor. It is also suggested that repeated excretion
and re-assimilation of mixed-acid products contribute to the reduced yield during scale-up and that formate analysis is useful
for detecting local oxygen deficiency in large-scale E. coli processes.
Received: 7 November 1998 / Received revision: 4 February 1999 / Accepted: 5 February 1999 相似文献
10.
Towards a reduction in excess sludge production in activated sludge processes: biomass physicochemical treatment and biodegradation 总被引:15,自引:0,他引:15
M. Rocher G. Goma A. Pilas Begue L. Louvel J. L. Rols 《Applied microbiology and biotechnology》1999,51(6):883-890
To decrease activated sludge production, microbial cell lysis can be amplified to enhance cryptic growth (biomass growth
on lysates). Cell breakage techniques (thermal, alkaline, acid) were studied to generate Alcaligenes eutrophus and sludge lysates and to evaluate their biodegradability. Gentle treatment conditions produced the best results. Complete
cell deactivation was obtained for temperatures higher than 55 °C. The release kinetics were similar for temperatures varying
from 60 °C to 100 °C. A 20-min incubation was suitable for reaching 80% of the maximum releasable carbon. In thermal-chemical
hydrolysis, NaOH was the most efficient for inducing cell lysis. Carbon release was a two-step process. First an immediate
release occurred, which was of the same order of magnitude for A. eutrophus and sludge [100–200 mg dissolved organic C (DOC) g total suspended solids (TSS)−1], followed by a post-treatment release. The second step was virtually equivalent to the first for sludge, and weaker for
A. eutrophus (<50 mg DOC g TSS−1). The biodegradability of the soluble fraction, both the immediate and the post-treatment carbon release, was investigated.
The optimal degradation yield, obtained with sludge cells, reached 55% after 48 h of incubation and 80% after 350 h. The most
consistent lysis and biodegradation results occurred at pH 10 and 60 °C after a 20-min incubation.
Received: 30 October 1998 / Received revision: 16 February 1999 / Accepted: 20 February 1999 相似文献
11.
Rajaguru P Kalaiselvi K Palanivel M Subburam V 《Applied microbiology and biotechnology》2000,54(2):268-273
A sequential anaerobic–aerobic treatment process based on mixed culture of bacteria isolated from textile dye effluent-contaminated
soil was used to degrade sulfonated azo dyes Orange G (OG), Amido black 10B (AB), Direct red 4BS (DR) and Congo red (CR).
Under anaerobic conditions in a fixed-bed column using glucose as co-substrate, the azo dyes were reduced and amines were
released by the bacterial biomass. The amines were completely mineralized in a subsequent aerobic treatment using the same
isolates. The maximum degradation rate observed in the treatment system for OG was 60.9 mg/l per day (16.99 mg/g glucose utilized),
for AB 571.3 mg/l per day (14.46 mg/g glucose utilized), for DR 112.5 mg/l per day (32.02 mg/g glucose utilized) and for CR
134.9 mg/l per day (38.9 mg/g glucose utilized).
Received: 6 August 1999 / Received revision: 20 December 1999 / Accepted: 24 December 1999 相似文献
12.
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
13.
M. Arnold A. Reittu A. von Wright P. J. Martikainen M.-L. Suihko 《Applied microbiology and biotechnology》1997,48(6):738-744
A biofiltration process was developed for styrene-containing off-gases using peat as filter material. The average styrene
reduction ratio after 190 days of operation was 70% (max. 98%) and the mean styrene elimination capacity was 12 g m−3 h−1 (max. 30 g m−3 h−1). Efficient styrene degradation required addition of nutrients to the peat, adjustment of the pH to a neutral level and efficient
control of the humidity. Maintenance of the water balance was easier in a down-flow than in an up-flow process, the former
consequently resulting in much better filtration efficiency. The optimum operation temperature was around 23 °C, but the styrene
removal was still satisfactory at 12 °C. Seven different bacterial isolates belonging to the genera Tsukamurella, Pseudomonas, Sphingomonas, Xanthomonas and an unidentified genus in the γ group of the Proteobacteria isolated from the microflora of active peat filter material were capable of styrene degradation. The isolates differed in
their capacity to decompose styrene to carbon dioxide and assimilate it to biomass. No toxic intermediate degradation products
of styrene were detected in the filter outlet gas or in growing cultures of isolated bacteria. The use of these isolates in
industrial biofilters is beneficial at low styrene concentrations and is safe from both the environmental and public health
points of view.
Received: 30 May 1997 / Received revision: 22 August 1997 / Accepted: 25 August 1997 相似文献
14.
Babu KR Swaminathan S Marten S Khanna N Rinas U 《Applied microbiology and biotechnology》2000,53(6):655-660
Escherichia coli TG1 transformed with a temperature-regulated interferon-α expression vector was grown to high cell density in defined medium
containing glucose as the sole carbon and energy source, utilizing a simple fed-batch process. Feeding was carried out to
achieve an exponential increase in biomass at growth rates which minimized acetate production. Thermal induction of such high
cell density cultures resulted in the production of ∼4 g interferon-α/l culture broth. Interferon-α was produced exclusively
in the form of insoluble inclusion bodies and was solubilized under denaturing conditions, refolded in the presence of arginine
and purified to near homogeneity, utilizing single-step ion-exchange chromatography on Q-Sepharose. The yield of purified
interferon-α was ∼300 mg/l with respect to the original high cell density culture broth (overall yield of ∼7.5% active interferon-α).
The purified recombinant interferon-α was found by different criteria to be predominantly monomeric and possessed a specific
bioactivity of ∼2.5 × 108 IU/mg based on viral cytopathic assay.
Received: 8 October 1999 / Received revision: 8 December 1999 / Accepted: 12 December 1999 相似文献
15.
Rhizobium meliloti proved to be sensitive to low concentrations of the herbicide phosphinothricintripeptide (PTT) and its active ingredient
phosphinothricin (PT), which was formerly assumed to be non-toxic for most of the bacteria analysed. Growth was more strongly
reduced in sterile synthetic media and less reduced in sterile soil; in unsterile soil only a transient growth reduction was
detectable. Sensitivity was also observed in five out of eight other species analysed. In all sensitive species tested, spontaneous
resistances to PT occurred. Under sterile conditions, PTT and PT reduced rhizobial nodulation rates of PT-resistant alfalfa
plants drastically; however, nitrogen fixation in the few nodules that arose was unaffected. Because of the small number of
nodules, the overall fixation rate was strongly diminished. In unsterile soil, nodulation and nitrogen fixation rates were
not changed, possibly because of the rapid degradation of PTT and PT in the soil. Using a herbicide as model substance it
could be demonstrated that the sensitivity of R. meliloti to chemical additives in the soil can be detected by analysing its growth rate, and that even a weak impact can influence
its nodulation capacity. R. meliloti has proven to be a fast, easy and sensitive detection system for bacteriostatic components present in the soil.
Received: 12 April 1996 / Received revision: 15 July 1996 / Accepted: 18 July 1996 相似文献
16.
Acetobacter aceti have been grown on ethanol under inhibitory conditions created by high concentrations of phenol. A defined medium with no
vitamin or amino acid supplements has been used such that ethanol was the sole carbon substrate. The culture temperature was
maintained at 30 °C while the pH was manually controlled to fall within the range 4.5–6.0 during ethanol consumption. Growth
on ethanol at a few thousand milligrams per litre (below the known inhibitory level) resulted in a maximum specific growth
rate of 0.16 h−1 with a 95% yield of acetic acid, followed immediately by acetic acid consumption at a growth rate of 0.037 h−1. Phenol was found to inhibit growth by decreasing both the specific growth rate and the biomass yield during ethanol consumption.
On the other hand, the yield of acetic acid during ethanol consumption and the yield of biomass during acetic acid consumption
remained constant, independent of phenol inhibition. A model is presented and is shown to represent the phenol-inhibited growth
behaviour of A. aceti during both ethanol and acetic acid consumption.
Received: 6 November 1998 / Received revision: 8 February 1999 / Accepted: 12 February 1999 相似文献
17.
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
18.
J. S. Potekhina N. G. Sherisheva L. P. Povetkina A. P. Pospelov T. A. Rakitina F. Warnecke G. Gottschalk 《Applied microbiology and biotechnology》1999,51(5):639-646
In acetate-limited chemostat cultures of Acinetobacter johnsonii 210A at a dilution rate of 0.1 h−1 the polyphosphate content of the cells increased from 13% to 24% of the biomass dry weight by glucose (100 mM), which was
only oxidized to gluconic acid. At this dilution rate, only about 17% of the energy from glucose oxidation was calculated
to be used for polyphosphate synthesis, the remaining 83% being used for biomass formation. Suspensions of non-growing, phosphate-deficient
cells had a six- to tenfold increased uptake rate of phosphate and accumulated polyphosphate aerobically up to 53% of the
biomass dry weight when supplied with only orthophosphate and Mg2+. The initial polyphosphate synthesis rate was 98 ± 17 nmol phosphate min−1 mg protein−1. Intracellular poly-β-hydroxybutyrate and lipids served as energy sources for the active uptake of phosphate and its subsequent
sequestration to polyphosphate. The H+-ATPase inhibitor N,N′-dicyclohexylcarbodiimide caused low ATP levels and a severe inhibition of polyphosphate formation, suggesting the involvement
of polyphosphate kinase in polyphosphate synthesis. It is concluded that, in A. johnsonii 210A, (i) polyphosphate is accumulated as the energy supply is in excess of that required for biosynthesis, (ii) not only
intracellular poly-β-hydroxybutyrate but also neutral lipids can serve as an energy source for polyphosphate-kinase-mediated
polyphosphate formation, (iii) phosphate-deficient cells may accumulate as much polyphosphate as activated sludges and recombinants
of Escherichia coli designed for polyphosphate accumulation.
Received: 23 October 1998 / Received revision: 18 January 1999 / Accepted: 22 January 1999 相似文献
19.
The thermophilic bacterium, Thermus species ATCC 27978, which is capable of aerobically degrading benzene, toluene, ethylbenzene, and the xylenes (BTEX), was
cultured in 5-1 fermentors on a Castenholz salts-tryptone medium. This bacterium can be cultivated more conveniently at 45 °C,
a temperature substantially lower than its optimal growth temperature (approx. 60 °C). Yet, the washed harvested cells from
such cultures display the same initial BTEX-degrading activity as those when Thermus sp. is grown at its higher optimal temperature. Two bioreactor cultivation modes, batch and fed batch, were investigated.
More biomass and more BTEX-degrading activity (assayed at 60 °C) were generated in fed-batch cultures than in the growth-limited
batch cultures. The former yielded a biomass concentration of 2.5 g dry cell weight (DCW) l−1 and whole-cell degrading specific activities of 7.6 ± 1.3, 10.1 ± 1.9, 9.8 ± 2.1, 2.3 ± 0.5, and 4.6 ± 0.9 nmol degraded
(mg DCW)−1 min−1 for benzene, toluene, ethylbenzene, m-xylene, and the o- plus p-xylenes (unresolved mixture), respectively. Although the formation of cellular BTEX-degrading activity is growth-associated,
a slow to moderate specific growth rate of 0.02–0.07 h−1 favors the production of BTEX-degrading activity, while a high growth rate, of the order of 0.16 h−1, is detrimental to its production. The washed harvested Thermus sp. cells were capable of degrading BTEX over a broad range of thermophilic incubation temperatures, 45–77 °C.
Received: 28 June 1996 / Received revision: 31 December 1996 / Accepted: 31 January 1997 相似文献
20.
The biological degradation of complex mixtures of recalcitrant substances is still a major challenge in environmental biotechnology
and the remediation of coal-tar constitutes one such problem area. Biofilm bioreactors offer many advantages and may be successfully
used for this purpose. Two stirred-tank reactors and one packed-bed reactor were tested in a continuous mode. Continuous cultivation
allows microbial selection to take place whilst adhesive growth provides a high degradation capacity and process stability.
The reactors were inoculated with mixed microbial populations to favour complete metabolism and to prevent metabolite accumulation
and substrate inhibition effects. Phenol, o-cresol, quinoline, dibenzofuran, acenaphthene and phenanthrene were used as model contaminants and constituted the sole energy
and carbon sources. The hydraulic retention time (HRT) was initially set to 2.5 days for a period of several months to allow
the establishment of a stable biofilm and was then gradually decreased. All the compounds were found to be degraded by more
than 90% at HRT of 3 h or more. Neither substrate inhibition nor metabolite accumulation effects were observed. The stirred-tank
configuration was found to be the most efficient for use with high loads. No improvement in the degradation capacity could
be achieved by increasing the biofilm surface in these reactors, illustrating that the limiting factor may be the mass transfer
limitations rather than the availability of the biofilm surface. Finally, anaerobic treatment was successfully achieved, confirming
the potential for remediation of contaminated sites under anaerobic conditions, providing that alternative electron acceptors
are present.
Received: 16 March 1999 / Received revision: 3 May 1999 / Accepted: 7 May 1999 相似文献