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1.
A two-phase aqueous/organic partitioning bioreactor scheme was used to degrade mixtures of toluene and benzene, and toluene
and p-xylene, using simultaneous and sequential feeding strategies. The aqueous phase of the partitioning bioreactor contained
Pseudomonas sp. ATCC 55595, an organism able to degrade benzene, toluene and p-xylene simultaneously. An industrial grade of oleyl alcohol served as the organic phase. In each experiment, the organic
phase of the bioreactor was loaded with 10.15 g toluene, and either 2.0 g benzene or 2.1 g p-xylene. The resulting aqueous phase concentrations were 50 mg/l, 25 mg/l and 8 mg/l toluene, benzene and p-xylene respectively. The simultaneous fermentation of benzene and toluene consumed these compounds at volumetric rates of
0.024 g l−1 h−1 and 0.067 g l−1 h−1, respectively. The simultaneous fermentation of toluene and p-xylene consumed these xenobiotics at volumetric rates of 0.066 g l−1 h−1 and 0.018 g l−1 h−1, respectively. A sequential feeding strategy was employed in which toluene was added initially, but the benzene or p-xylene aliquot was added only after the cells had consumed half of the initial toluene concentration. This strategy was shown
to improve overall degradation rates, and to reduce the stress on the microorganisms. In the sequential fermentation of benzene
and toluene, the volumetric degradation rates were 0.056 g l−1 h−1 and 0.079 g l−1 h−1, respectively. In the toluene/p-xylene sequential fermentation, the initial toluene load was consumed before the p-xylene aliquot was consumed. After 12 h in which no p-xylene degradation was observed, a 4.0-g toluene aliquot was added, and p-xylene degradation resumed. Excluding that 12-h period, the microbes consumed toluene and p-xylene at volumetric rates of 0.074 g l−1 h−1 and 0.025 g l−1 h−1, respectively. Oxygen limitation occurred in all fermentations during the rapid growth phase.
Received: 16 November 1998 / Received revision: 29 March 1999 / Accepted: 9 April 1999 相似文献
2.
Farshid Ghorbani Shahna Faride Golbabaei Javad Hamedi Hossein Mahjub Hossein Reza Darabi Seyed Jamaleddin Shahtaheri 《Bioprocess and biosystems engineering》2010,33(2):219-226
An adapted bioactive foamed emulsion bioreactor for the treatment of benzene vapor has been developed. In this reactor, bed
clogging was resolved by bioactive foam as a substitute of packing bed for interfacial contact of liquid to gaseous phase.
The pollutant solubility has been increased using biocompatible organic phase in liquid phase and this reactor can be applied
for higher inlet benzene concentration. Experimental results showed a benzene elimination capacity (EC) of 220 g m−3 h−1 with removal efficiency (RE) of 85% for benzene inlet concentration of 1–1.2 g m−3 at 15 s gas residence time in bioreactor. Assessment of benzene concentration in liquid phase showed that a significant amount
of transferred benzene mass has been biodegraded. By optimizing the operational parameters of bioreactor, continuous operation
of bioreactor with high EC and RE was demonstrated. With respect to the results, this reactor has the potential to be applied
instead of biofilter and biotrickling filters. 相似文献
3.
A two-phase organic/aqueous reactor configuration was developed for use in the biodegradation of benzene, toluene and p-xylene, and tested with toluene. An immiscible organic phase was systematically selected on the basis of predicted and experimentally
determined properties, such as high boiling points, low solubilities in the aqueous phase, good phase stability, biocompatibility,
and good predicted partition coefficients for benzene, toluene and p-xylene. An industrial grade of oleyl alcohol was ultimately selected for use in the two-phase partitioning bioreactor. In
order to examine the behavior of the system, a single-component fermentation of toluene was conducted with Pseudomonas sp. ATCC 55595. A 0.5-l sample of Adol 85 NF was loaded with 10.4 g toluene, which partitioned into the cell containing 1 l
aqueous medium at a concentration of approximately 50 mg/l. In consuming the toluene to completion, the organisms were able
to achieve a volumetric degradation rate of 0.115 g l−1 h−1. This system is self-regulating with respect to toluene delivery to the aqueous phase, and requires only feedback control
of temperature and pH.
Received: 16 November 1998 / Received revision: 28 March 1999 / Accepted: 9 April 1999 相似文献
4.
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
5.
Toluene vapour removal in a laboratory-scale biofilter 总被引:4,自引:0,他引:4
A bench-scale biofilter with a 0.5-m high filter bed, inoculated with a toluene-degrading strain of Acinetobacter sp. NCIMB 9689, was used to study toluene removal from a synthetic waste air stream. Different sets of continuous tests were
conducted at influent toluene concentrations ranging over 0.1–4.0 g m−3 and at superficial gas velocities ranging over 17.8–255 m h−1. The maximum volumetric toluene removal rate for the biofilter (242 g m−3 h−1) was obtained at a superficial gas velocity of 127.5 m h−1 (corresponding to a residence time of 28 s) and a toluene inlet concentration of 4.0 g m−3. Under these operating conditions, toluene removal efficiency was only 0.238, which suggested that effective operation required
higher residence times. Removal efficiencies higher than 0.9 were achieved at organic loads less than 113.7 g m−3 h−1. A macro-kinetic study, performed using concentration profiles along the bioreactor, revealed this process was limited by
diffusion at organic loads less than 100 g m−3 h−1 and by biological reaction beyond this threshold.
Received: 10 October 1999 / Received revision: 15 February 2000 / Accepted: 18 February 2000 相似文献
6.
L Oliver T Zakharova A Konopka R F Turco 《Journal of industrial microbiology & biotechnology》2000,24(3):191-197
A novel graywater treatment system consisting of an aerated batch reactor and biomass-retaining ultrafiltration unit was evaluated
for treatment of shipboard wastes. The focus of this study was to determine the resilience of the biomass recycle reactor
to perturbations of sodium hypochlorite, the major component of bleach. A bench-scale reactor was perturbed with 50, 190,
and 1000 mg L−1 sodium hypochlorite and monitored for changes in respiration, substrate utilization, viable plate counts, fatty acid methyl
ester profiles, and Biolog-GN patterns. Following the addition of hypochlorite, respiration and substrate utilization were
not detected, and viable biomass decreased. Recovery times following perturbations were longer with higher concentrations
of sodium hypochlorite. Community composition (determined by fatty acid methyl ester analysis) changed during the recovery
from hypochlorite perturbations. However, more significant differences in community composition were noted between different
perturbations and were a function of time. Irrespective of initial community composition, the reactor communities recovered
from hypochlorite perturbations. Biolog patterns showed no notable change in the overall metabolic capacity of the community.
The biomass recycle reactor’s resistance to sodium hypochlorite perturbations contributes to its usefulness in treatment of
shipboard wastes. Journal of Industrial Microbiology & Biotechnology (2000) 24, 191–197.
Received 28 July 1999/ Accepted in revised form 03 December 1999 相似文献
7.
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
8.
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
9.
Two protozoan species as well as an uncharacterized protozoan consortium were added to a toluene-degrading biotrickling filter to investigate protozoan predation as a means of biomass control. Wet biomass formation in 23.6-L reactors over a 77-day period was reduced from 13.875 kg in a control biotrickling filter to 11.795 kg in a biotrickling filter enriched with protozoa. The average toluene vapor elimination capacity at 1 g/m3 toluene and 64 m3/(m3. h) was 31.1 g/(m3. h) in the control and 32.2 g/(m3. h) in the biotrickling filter enriched with protozoa. At higher toluene inlet concentrations, toluene degradation rates increased and were slightly higher in the biotrickling filter enriched with protozoa. The lower rate of biomass accumulation after the addition of protozoa was due to an increase of carbon mineralization (68% as compared to 61% in the control). Apparent biomass yield coefficients in the control and enriched trickling filter were 0.72 and 0.59 g dry biomass/g toluene, respectively. The results show that protozoan predation may be a useful tool to control biomass in biotrickling filters, however, further stimulation of predation of the biomass immobilized in the reactor is required to ensure long-term stability of biotrickling filters. 相似文献
10.
Thermophilic acidification of dairy wastewater 总被引:2,自引:0,他引:2
Acidification of simulated dairy wastewater was conducted in an upflow reactor at 55 °C. Results showed that the degree of
acidification decreased with the increase in chemical oxygen demand (COD) loading rate, from 60.8% at 4 g l−1 day−1 to 27.1% at 24 g l−1 day−1. Carbohydrate was readily degraded at all loading rates, but degradation of protein and lipid decreased with the increase
in loading rate. Most carbohydrate degradation occurred at the reactor bottom, whereas protein was degraded mainly after the
carbohydrate became depleted. The predominant acidification products were acetate, propionate, butyrate and ethanol, whereas
formate, i-butyrate, valerate, i-valerate, caproate, lactate, methanol, propanol and butanol were present in lesser quantities. The increase in loading rate
resulted in the increase of propionate and the decrease of acetate, but had little effect on ethanol and butyrate productions.
Only 2.5–8.8% of influent COD was converted to hydrogen and methane. The biomass yield was 0.30–0.43 mg VSS mg−1 COD.
Received: 8 December 1999 / Received revision: 14 February 2000 / Accepted: 25 February 2000 相似文献
11.
The effect of nitrogen limitation on young and mature steady-state biofilm in a trickle-bed filter was studied. Toluene and
n-heptane were the sole carbon source. Biomass concentration, respiration, substrate-induced respiration, metabolic quotient,
and total hydrocarbon degradation efficiency were measured. The aim of the experiment was to control excess biomass production
in the trickle-bed filter by limiting the mineral nutrients and to achieve increased mineralization of the carbon source.
Biofilm growth responded strongly to the amount of available nitrogen, whereas hydrocarbon degradation efficiency reached
a maximum of 60% and could not be increased even by further addition of nitrogen. The experiments showed that 95% of the adsorbed
carbon was mineralized completely and only 5% was used for biofilm formation. This complete mineralization can also be concluded
from the metabolic quotient. The value of the latter was about 6–10 mg CO2-C g−1 Cmic
h−1, indicating an expanded energy demand due to stress effects in the presence of nutrient deficiency. It was postulated that
determination of the metabolic quotient could be an simple instrument to measure the rate of mineralization of carbon sources
and also the rate of biomass formation in trickle-bed filters or biofilters.
Received: 11 November 1998 / Accepted: 5 December 1998 相似文献
12.
Studies of microbial purification of a model waste water containing 4-nitrophenol were carried out in a continuously working
aerobic solid-bed reactor. The main emphasis was on the dynamic behaviour of the system after a sudden change in cultivation
conditions and on the steady-state performance of the reactor as a function of the pollution load. A change from ammonium-free
to ammonium-containing medium hardly influenced the nitrophenol degradation. The reactor responded differently to an increase
in pollutant load, which was brought about by increasing either the 4-nitrophenol content or the flow of the waste water.
Up to a load of 270 mg l−1 h−1 the pollutant was stably and almost completely degraded. At a higher load, only a partial 4-nitrophenol degradation took
place. A mathematical model was derived to describe the processes that occurred in the reactor. By segregation into two compartments
– the aqueous phase and the biofilm – account was taken of the fact that the pollutant is carried into the biofilm by diffusion
and is degraded there. The observed relations between the pollutant load, the pollutant concentration in the outlet of the
reactor and the reactor performance agreed with the simulated process behaviour. As the model simulation showed, the incomplete
pollutant degradation at a higher reactor load was caused by oxygen limitation.
Received: 5 August 1998 / Received revision: 22 October 1998 / Accepted: 24 October 1998 相似文献
13.
Raúl Muñoz María Hernández Ana Segura Joao Gouveia Antonia Rojas Juan Luis Ramos Santiago Villaverde 《Applied microbiology and biotechnology》2009,83(1):189-198
The long-term performance and stability of Pseudomonas putida mt-2 cultures, a toluene-sensitive strain harboring the genes responsible for toluene biodegradation in the archetypal plasmid
pWW0, was investigated in a chemostat bioreactor functioning under real case operating conditions. The process was operated
at a dilution rate of 0.1 h−1 under toluene loading rates of 259 ± 23 and 801 ± 78 g m−3 h−1 (inlet toluene concentrations of 3.5 and 10.9 g m−3, respectively). Despite the deleterious effects of toluene and its degradation intermediates, the phenotype of this sensitive
P. putida culture rapidly recovered from a 95% Tol− population at day 4 to approx. 100% Tol+ cells from day 13 onward, sustaining elimination capacities of 232 ± 10 g m−3 h−1 at 3.5 g Tol m−3 and 377 ± 13 g m−3 h−1 at 10.9 g Tol m−3, which were comparable to those achieved by highly tolerant strains such as P. putida DOT T1E and P. putida F1 under identical experimental conditions. Only one type of Tol− variant, harboring a TOL-like plasmid with a 38.5 kb deletion (containing the upper and meta operons for toluene biodegradation), was identified. 相似文献
14.
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
15.
The influence of toluene concentration on the specific growth rate, cellular yield, specific CO2, and metabolite production by Pseudomonas putida F1 (PpF1) was investigated. Both cellular yield and specific CO2 production remained constant at 1.0 ± 0.1 g biomass dry weight (DW) g−1 toluene and 1.91 ± 0.31 g CO2 g−1 biomass, respectively, under the tested range of concentrations (2–250 mg toluene l−1). The specific growth rate increased up to 70 mg toluene l−1. Further increases in toluene concentration inhibited PpF1 growth, although inhibitory concentrations were far from the application range of biological treatment processes. The specific
ATP content increased with toluene concentration up to toluene concentrations of 170 mg l−1. 3-Methyl catechol (3-MC) was never detected in the cultivation medium despite being an intermediary in the TOD pathway.
This suggested that the transformation from toluene to 3-MC was the limiting step in the biodegradation process. On the other
hand, benzyl alcohol (BA) was produced from toluene in a side chain reaction. This is, to the best of our knowledge, the first
reported case of methyl monoxygenation of toluene by PpF1 not harboring the pWW0 TOL plasmid. In addition, the influence of 3-MC, BA, and o-cresol on toluene degradation was investigated respirometrically, showing that toluene-associated respiration was not significantly
inhibited in the presence of 10–100 mg l−1 of the above-mentioned compounds. 相似文献
16.
Batch experiments were conducted to evaluate the biodegradation rates of limonene, α-pinene, γ-terpinene, terpinolene and
α-terpineol at 23 °C under aerobic conditions. Biodegradation was demonstrated by the depletion of monoterpene mass, CO2 production and a corresponding increase in biomass. Monoterpene degradation in liquid cultures devoid of soil followed Monod
kinetics. The maximum specific growth rate (μmax) was 0.02 h−1 and 0.06 h−1 and the half-velocity constant (K
s ) varied from 32 mg/l to 3 mg/l for the limonene and α-terpineol respectively. The recovery of monoterpenes by solvent extraction
from autoclaved and azide-amended soil-slurry samples decreased over time and ranged from 69% to 73% for 120 h of incubation
period. Although a significant fraction of monoterpene hydrocarbon could not be extracted, mineralization of these compounds
in the soil-slurry systems took place, as shown by CO2 production. The soil-normalized degradation rates for the hydrocarbon monoterpenes ranged from 0.6 μg g−1 h−1 to 2.1 μg g−1 h−1. A kinetic model – which combined monoterpene biodegradation in the liquid phase and net desorption – was developed and applied
to data obtained from soil-slurry assays.
Received: 10 September 1996 / Received revision: 16 December 1996 / Accepted: 10 January 1997 相似文献
17.
BTEX catabolism interactions in a toluene-acclimatized biofilter 总被引:1,自引:0,他引:1
BTEX substrate interactions for a toluene-acclimatized biofilter consortium were investigated. Benzene, ethylbenzene, o-xylene, m-xylene and p-xylene removal efficiencies were determined at a loading rate of 18.07 g m−3 h−1 and retention times of 0.5–3.0 min. This was also repeated for toluene in a 1:1 (m/m) ratio mixture (toluene: benzene, ethylbenzene,
or xylene ) with each of the other compounds individually to obtain a final total loading of 18.07 g m−3 h−1. The results obtained were modelled using Michaelis–Menten kinetics and an explicit finite difference scheme to generate
v
max and K
m parameters. The v
max/K
m ratio (a measure of the catalytic efficiency, or biodegradation capacity, of the reactor) was used to quantify substrate
interactions occurring within the biofilter reactor without the need for free-cell suspended and monoculture experimentation.
Toluene was found to enhance the catalytic efficiency of the reactor for p-xylene, while catabolism of all the other compounds was inhibited competitively by the presence of toluene. The toluene-acclimatized
biofilter was also able to degrade all of the other BTEX compounds, even in the absence of toluene. The catalytic efficiency
of the reactor for compounds other than toluene was in the order: ethylbenzene>benzene>o-xylene>m-xylene>p-xylene. The catalytic efficiency for toluene was reduced by the presence of all other tested BTEX compounds, with the greatest
inhibitory effect being caused by the presence of benzene, while o-xylene and p-xylene caused the least inhibitory effect. This work illustrated that substrate interactions can be determined directly from
biofilter reactor results without the need for free-cell and monoculture experimentation.
Received: 13 April 2000 / Received revision: 20 July 2000 / Accepted: 27 July 2000 相似文献
18.
J. Carlos Roseiro P. J. Partidário N. Lobo M. J. Marçal 《Applied microbiology and biotechnology》1999,52(4):546-552
The change of dilution rate (D) on both Methylophilus methylotrophus NCIMB11348 and Methylobacterium sp. RXM CCMI908 growing in trimethylamine (TMA) chemostat cultures was studied in order to assess their ability to remove
odours in fish processing plants. M. methylotrophus NCIMB11348 was grown at dilution rates of 0.012–0.084 h−1 and the biomass level slightly increased up to values of D around 0.07 h−1. The maximum cell production rate was obtained at 0.07 h−1 corresponding to a maximum conversion of carbon into cell mass (35%). The highest rate of TMA consumption was 3.04 mM h−1 occurring at D=0.076 h−1. Methylobacterium sp. RXM CCMI908 was grown under similar conditions. The biomass increased in a more steep manner up to values of D around 0.06 h−1. The maximum cell production rate (0.058 g l−1h−1) was obtained in the region close to 0.06 h−1 where a maximum conversion of the carbon into cell mass (40%) was observed. The maximum TMA consumption was 2.33 mM h−1 at D=0.075 h−1. The flux of carbon from TMA towards cell synthesis and carbon dioxide in both strains indicates that the cell is not excreting
products but directing most of the carbon source to growth. Carbon recovery levels of approximately 100% show that the cultures
are carbon-limited. Values for theoretical maximum yields and maintenance coefficients are presented along with a kinetic
assessment based on the determination of the substrate saturation constant and maximum growth rate for each organism.
Received: 25 February 1999 / Received revision: 14 May 1999 / Accepted: 17 May 1999 相似文献
19.
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
20.
Extracellular radicals produced by Trametes versicolor under quinone redox cycling conditions can degrade a large variety of pollutant compounds, including trichloroethylene (TCE).
This study investigated the effect of the agitation speed and the gas–liquid phase volume ratio on TCE degradation using central
composite design (CCD) methodology for a future scale-up to a reactor system. The agitation speed ranged from 90 to 200 rpm,
and the volume ratio ranged from 0.5 to 4.4. The results demonstrated the important and positive effect of the agitation speed
and an interaction between the two factors on TCE degradation. Although the volume ratio did not have a significant effect
if the agitation speed value was between 160 and 200 rpm, at lower speed values, the specific pollutant degradation was clearly
more extensive at low volume ratios than at high volume ratios. The fitted response surface was validated by performing an
experiment using the parameter combination in the model that maximised TCE degradation. The results of the experiments carried
out using different biomass concentrations demonstrated that the biomass concentration had a positive effect on pollutant
degradation if the amount of biomass present was lower than 1.6 g dry weight l−1. The results show that the maximum TCE degradation was obtained at the highest speed (200 rpm), gas–liquid phase volume ratio
(4.4), and a biomass concentration of 1.6 g dry weight l−1. 相似文献