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1.
The toxicity of chlorinated aliphatic hydrocarbons on acetoclastic methanogens in anaerobic granular sludge was determined
using a standardized anaerobic bioassay method. Most of the chloroaliphatics tested were strong inhibitors of methanogenesis.
Tri- and tetrachloride derivatives of methane and ethane were the most highly toxic compounds tested, with concentrations
of less than 18 mg/l resulting in 50% inhibition (IC50) of the methanogenic activity. Dichlorinated compounds were less toxic, with IC50 values ranging from 40 mg/l to 100 mg/l. On the other hand, perchlorinated derivatives of ethane and ethene were scarcely
inhibitory at concentrations near their maximum water solubility. The toxicity caused by chlorinated aliphatic hydrocarbons
was reversible. The comparison of structurally related compounds indicated that unsaturated chloroaliphatics were less toxic
than their saturated counterparts. A reverse correlation between the electric dipole moment of these compounds and their methanogenic
toxicity is discussed.
Received: 9 July 1996 / Received revision: 11 October 1996 / Accepted: 18 October 1996 相似文献
2.
M. R. Natarajan W.-M. Wu J. Nye H. Wang L. Bhatnagar M. K. Jain 《Applied microbiology and biotechnology》1996,46(5-6):673-677
An anaerobic methanogenic microbial consortium, developed in a granular form, exhibited extensive dechlorination of defined
polychlorinated biphenyl (PCB) congeners. A 2,3,4,5,6-pentachlorobiphenyl was dechlorinated to biphenyl via 2,3,4,6-tetrachlorobiphenyl,
2,4,6-trichlorobiphenyl, 2,4-dichlorobi-phenyl and 2-chlorobiphenyl (CB). Removal of chlorine atoms from all three positions
of the biphenyl ring, i.e., ortho, meta and para, was observed during this reductive dechlorination process. Biphenyl was identified as one of the end-products of the reductive
dechlorination by GC-MS. After 20 weeks, the concentrations of the dechlorination products 2,4,6-CB, 2,4-CB, 2-CB and biphenyl
were 8.1, 41.2, 3.0 and 47.8 μM respectively, from an initial 105 μM 2,3,4,5,6-CB. The extent and pattern of the dechlorination
were further confirmed by the dechlorination of lightly chlorinated congeners including 2-CB, 3-CB, 4-CB, 2,4-CB and 2,6-CB
individually. This study indicates that the dechlorination of 2,3,4,5,6-CB to biphenyl is due to ortho, meta and para dechlorination by this anaerobic microbial consortium.
Received: 30 April 1996 / Received revision: 26 July 1996 / Accepted: 5 August 1996 相似文献
3.
R. Beaudet M.-J. Lévesque R. Villemur M. Lanthier M. Chénier F. Lépine J.-G. Bisaillon 《Applied microbiology and biotechnology》1998,50(1):135-141
Anaerobic biodegradation of pentachlorophenol (PCP) in a contaminated soil from a wood-treating industrial site was studied
in soil slurry microcosms inoculated with a PCP-degrading methanogenic consortium. When the microcosms containing 10%–40%
(w/v) soil were inoculated with the consortium, more than 90% of the PCP was removed in less than 30 days at 29 °C. Less-chlorinated
phenols, mainly 3-chlorophenol were slowly degraded and accumulated in the cultures. Addition of glucose and sodium formate
to the microcosms was not necessary, suggesting that the organic compounds in the soil can sustain the dechlorinating activity.
Inoculation of Desulfitobacterium frappieri strain PCP-1 along with a 3-chlorophenol-degrading consortium in the microcosms also resulted in the rapid dechlorination
of PCP and the slow degradation of 3-chlorophenol. Competitive polymerase chain reaction experiments showed that PCP-1 was
present at the same level throughout the 21-day biotreatment. D. frappieri, strain PCP-1, inoculated into the soil microcosms, was able to remove PCP from soil containing up to 200 mg PCP/kg soil.
However, reinoculation of the strain was necessary to achieve more than 95% PCP removal with a concentration of 300 mg and
500 mg PCP/kg soil. These results demonstrate that D. frappieri strain PCP-1 can be used effectively to dechlorinate PCP to 3-chlorophenol in contaminated soils.
Received: 14 November 1997 / Received revision: 29 January 1998 / Accepted: 24 February 1998 相似文献
4.
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
5.
Initiation of [36Cl]hexachlorobenzene dechlorination in three different soils under artificially induced anaerobic conditions 总被引:1,自引:0,他引:1
P. Rosenbrock R. Martens F. Buscot J. C. Munch 《Applied microbiology and biotechnology》1997,48(1):115-120
The potential for reductive dechlorination of hexachlorobenzene was investigated in samples of three different, naturally
oxic soils held under conditions of high oxygen deficiency. The soils were water-saturated and the influence on dechlorination
of adding different electron donors, a surfactant and an anaerobic microbial consortium was tested. The influence of supplied
electron donors seems to depend on the organic matter content of the soils. Dechlorination in the organic-matter-rich soil
from Maulach was not affected by amendment with organic electron donors. A release of about 40% chloride within 140 days was
observed for this soil in all biotic-treated assays. By contrast, the organic-matter-poor soil of Eppingen showed no dechlorination
in unamended assays. However, when it was supplemented with organic electron donors dechlorination of 2%–37% occurred within
140 days, depending on the type of electron donor. Complex substrate (wheat strawdust), from which carbon is slowly liberated,
gave the best results. These two soils had an indigenous dechlorinating anaerobic microflora, whereas the third soil (Rastatt)
required inoculation with an anaerobic consortium for dechlorination. The addition of electron donors alone did not cause
dechlorination in this sandy soil. The addition of a surfactant (Tween 80) to increase the bioavailability of hexachlorobenzene
did not enhance dechlorination. This process was not inhibited by inherent alternative electron acceptors in soil (NO3−, SO4
2−, Fe3+). The dechlorination did not require methanogenic conditions.
Received: 12 December 1996 / Received revision: 14 March 1997 / Accepted: 15 March 1997 相似文献
6.
We studied in batch reactors the kinetics and characterization of 70 °C, volatile fatty acids (VFAs)-grown, upflow anaerobic
sludge blanket granular sludge with 55 and 35 °C sludge as reference. The half-saturation constant (K
s), the inhibition constant (K
i), the maximum specific methane production rate (μCH4max), and the inhibition response coefficient (n) of the 70 °C sludge were 6.15 mM, 48.2 mM, 0.132 h−1, and 2.48, respectively, while no inhibition occurred at 55 and 35 °C, where the K
s was 3.67 and 3.82 mM, respectively. At 70 °C, the highest initial specific methanogenic activity (ISMA, 0.311 gCH4-COD per gram volatile solids per day) on VFAs was about 12–15% lower than that on acetate and three to four times less than
the ISMA for the 55 and 35 °C sludge. In the acetate conversion study, residual acetate (79 mg l−1) at 70 °C was three to five times higher than that at 55 and 35 °C. Further, the methane produced as percentage of the acetate
consumed at 70 °C (89%) was lower than that at 55 (95%) and 35 °C (97%). At 70 °C, 10% of the ISMA remained after 15 days
of starvation as compared to 26% (55 °C) and 92% (35 °C) after 30 days of starvation. Thus, the kinetics of the 70 °C granular
sludge seem to differ from those at 55 and 35 °C.
Received: 1 February 1999 / Accepted: 20 March 1999 相似文献
7.
Cometabolic biodegradation of methyl t-butyl ether by Pseudomonas aeruginosa grown on pentane 总被引:1,自引:0,他引:1
A bacterial strain identified as Pseudomonas aeruginosa was isolated from a soil consortium able to mineralize pentane. P. aeruginosa could metabolize methyl t-butyl ether (MTBE) in the presence of pentane as the sole carbon and energy source. The carbon balance for this strain, grown
on pentane, was established in order to determine the fate of pentane and the growth yield (0.9 g biomass/g pentane). An inhibition
model for P. aeruginosa grown on pentane was proposed. Pentane had an inhibitory effect on growth of P. aeruginosa, even at a concentration as low as 85 μg/l. This resulted in the calculation of the following kinetic parameters (μmax = 0.19 h−1, K
s = 2.9 μg/l, K
i = 3.5 mg/l). Finally a simple model of MTBE degradation was derived in order to predict the quantity of MTBE able to be degraded
in batch culture in the presence of pentane. This model depends only on two parameters: the concentrations of pentane and
MTBE.
Received: 16 July 1998 / Received revision: 11 November 1998 / Accepted 31 November 1998 相似文献
8.
C. Immoos Michael G. Hill Donita Sanders James A. Fee Claire E. Slutter John H. Richards Harry B. Gray 《Journal of biological inorganic chemistry》1996,1(6):529-531
The electrochemistry of a water-soluble fragment from the CuA domain of Thermus thermophilus cytochrome ba
3
has been investigated. At 25 °C, CuA exhibits a reversible reduction at a pyridine-4-aldehydesemicarbazone-modified gold electrode (0.1 M Tris, pH 8) with E° = 0.24 V vs NHE. Thermodynamic parameters for the [Cu(Cys)2Cu]+/0 electrode reaction were determined by variable-temperature electrochemistry (ΔS°rc = –5.4(12) eu, ΔS° = –21.0(12) eu, ΔH° = –11.9(4) kcal/mol;ΔG° = –5.6 (11) kcal/mol). The relatively small reaction entropy is consistent with a low reorganization energy for [Cu(Cys)2Cu]+/0 electron transfer. An irreversible oxidation of [Cu(Cys)2Cu]+ at 1 V vs NHE confirms that the CuII:CuII state of CuA is significantly destabilized relative to the CuII state of analogous blue-copper proteins.
Received: 3 June 1996 / Accepted: 26 August 1996 相似文献
9.
Chlorinated propanes are important pollutants that may show persistent behaviour in the environment. The biotransformation
of 1-chloropropane, 1,2-dichloropropane, 1,3-dichloropropane and 1,2,3-trichloropropane was studied using resting cell suspensions
of Methylosinus trichosporium OB3b expressing soluble methane monooxygenase. The transformation followed first-order kinetics. The rate constants were
in the order 1-chloropropane > 1,3-dichloropropane > 1,2-dichloropropane > 1,2,3-trichloropropane, and varied from 0.07 to
1.03 ml min−1 mg of cells−1 for 1,2,3-trichloropropane and 1-chloropropane respectively. Turnover-dependent inactivation occurred for all of the chloropropanes
tested. The inactivation constants were lower for 1-chloropropane and 1,2-dichloropropane than for 1,2,3-trichloropropane
and 1,3-dichloropropane. Not all the chloride was released during cometabolic transformation of the chlorinated propanes and
production of monochlorinated- and dichlorinated propanols was found by gas chromatography. The reaction pathway of 1,2,3-trichloropropane
conversion was studied by mass spectrometric analysis of products formed in 2H2O, which indicated that 1,2,3-trichloropropane was initially oxidized to 2,3-dichloropropionaldehyde and 1,3-dichloroacetone,
depending on whether oxygen insertion occurred on the C-3 or C-2 carbon of 1,2,3,-trichloropropane, followed by reduction
to the corresponding propanols. The results show that chloropropanes are susceptible to cometabolic oxidation by methanotrophs,
but that the transformation kinetics is worse than with cometabolic conversion of trichloroethylene.
Received: 27 November 1997 / Received revision: 27 February 1998 / Accepted: 27 February 1998 相似文献
10.
During cassava starch production, large amounts of cyanoglycosides were released and hydrolysed by plant-borne enzymes, leading
to cyanide concentrations in the wastewater as high as 200 mg/l. For anaerobic degradation of the cyanide during pre-acidification
or single-step methane fermentation, anaerobic cultures were enriched from soil residues of cassava roots and sewage sludge.
In a pre-acidification reactor this culture was able to remove up to 4 g potassium cyanide/l of wastewater at a hydraulic
retention time (t
HR) of 4 days, equivalent to a maximal cyanide space loading of 400 mg CN− l−1 day−1. The residual cyanide concentration was 0.2–0.5 mg/l. Concentrated cell suspensions of the mixed culture formed ammonia and
formate in almost equimolar amounts from cyanide. Little formamide was generated by chemical decay. A concentration of up
to 100 mmol ammonia/l had no inhibitory effect on cyanide degradation. The optimal pH for cyanide degradation was 6–7.5, the
optimal temperature 25–37 °C. At a pH of 5 or lower, cyanide accumulated in the reactor and pre-acidification failed. The
minimal t
HR for continuous cyanide removal was 1.5 days. The enriched mixed culture was also able to degrade cyanide in purely mineralic
wastewater from metal deburring, either in a pre-acidification reactor with a two-step process or in a one-step methanogenic
reactor. It was necessary to supplement the wastewater with a carbon source (e.g. starch) to keep the population active enough
to cope with any possible inhibiting effect of cyanide.
Received: 29 April 1998 / Received revision: 8 June 1998 / Accepted: 14 June 1998 相似文献
11.
S. Sánchez V. Bravo E. Castro A. J. Moya F. Camacho 《Applied microbiology and biotechnology》1998,50(5):608-611
We have analysed the influence of the initial pH of the medium and the quantity of aeration provided during the batch fermentation
of solutions of d-xylose by the yeast Hansenula polymorpha (34438 ATCC). The initial pH was altered between 3.5 and 6.5 whilst aeration varied between 0.0 and 0.3 vvm. The temperature
was kept at 30 °C during all the experiments. Hansenula polymorpha is known to produce high quantities of xylitol and low quantities of ethanol. The most favourable conditions for the growth
of xylitol turned out to be: an initial pH of between 4.5 and 5.5 and the aeration provided by the stirring vortex alone.
Thus, at an initial pH of 5.5, the maximum specific production rate (μm) was 0.41 h−1, the overall biomass yield (Y
x/s
G) was 0.12 g g−1, the specific d-xylose-consumption rate (q
s
) was 0.075 g g−1 h−1 (for t = 75 h), the specific xylitol-production rate (q
Xy
) was 0.31 g g−1 h−1 (for t = 30 h) and the overall yields of ethanol (Y
E/s
G) and xylitol (Y
Xy/s
G) were 0.017 and 0.61 g g−1 respectively. Both q
s
and q
Xy
decreased during the course of the experiments once the exponential growth phase had finished.
Received: 26 March 1998 / Received revision: 30 June 1998 / Accepted: 2 July 1998 相似文献
12.
T. Potrawfke T.-H. Löhnert K. N. Timmis R.-M. Wittich 《Applied microbiology and biotechnology》1998,50(4):440-446
The biphenyl-mineralizing bacterium Burkholderia sp. strain LB400 also utilized 3-chloro-, 4-chloro-, 2,3′-dichloro- and 2,4′-dichlorobiphenyl for growth. By the attack of the initial enzyme a chlorine was eliminated dioxygenolytically
from position 2 of one of the aromatic rings when hydrogens of both were substituted by chlorine. The strain mineralized 3-chloro-
and 2,3′-dichlorobiphenyl via the central intermediate 3-chlorobenzoate through its chlorocatechol pathway enzymes, but excreted
stoichiometric amounts of 4-chlorobenzoate from 4-chloro- and 2,4′-dichlorobiphenyl. These two compounds were mineralized by a co-culture of strain LB400 and a derivative of the (methyl-)
benzoate-degrading strain Pseudomonas putida mt-2 (TOL). The complete degradation was achieved upon transfer of a cluster of at least five genes, encoding the regulated
chlorocatechol pathway operon, from strain LB400 to strain mt-2. This transfer was demonstrated by the polymerase chain reaction.
Received: 15 April 1998 / Received revision: 12 June 1998 / Accepted: 19 June 1998 相似文献
13.
C. Hörber N. Christensen E. Arvin B. Kiær Ahring 《Applied microbiology and biotechnology》1999,51(5):694-699
Tetrachloroethene (C2Cl4) dechlorination kinetics in upflow anaerobic sludge blanket (UASB) reactors was determined after introducing de novo activities into the granular sludge. These activities were introduced by immobilizing Dehalospirillum multivorans in a test reactor containing unsterile granular sludge, and in a reference reactor, R1, containing sterile granular sludge.
A second reference reactor, R2, contained only unsterile granular sludge and served as a control. The kinetic experiments
were performed by pulsing the reactors with C2Cl4 in a recirculating batch mode. Formate and acetate were added as electron donor and carbon source. Both reactors inoculated
with D. multivorans dechlorinated C2Cl4 to an equimolar amount of C2H2Cl2 with only traces of C2HCl3 in the effluent. In the control reactor, C2HCl3 accumulated before C2H2Cl2 was produced. A computer simulation program (AQUASIM) was used to estimate the kinetic parameters. The half-saturation constants
(K
s) for C2Cl4 and C2HCl3 were almost equal in the reactors containing D.␣multivorans (17 μM and 18 μM for C2Cl4; 26 μM and 28 μM for C2HCl3), indicating no influence of sludge bacteria on the affinity of D. multivorans for C2Cl4 and C2HCl3. The maximum dechlorination rates (k
m
X
B) were about twice as high in the reactor containing D.␣multivorans immobilized in sterile sludge (11 mmol C2Cl4 l sludge−1 day−1 and 27 mmol C2HCl3 l sludge−1 day−1) than in the test reactor (4.4 mmol C2Cl4 l sludge−1 day−1 and 15 mmol C2HCl3 l sludge−1 day−1). Compared to other C2Cl4-degrading systems, the dechlorination rates of the inoculated reactors and their affinities for C2Cl4 and C2HCl3 were high. Therefore, introduction of de novo activity is promising for the use of anaerobic reactors to bioremediate C2Cl4-polluted water.
Received: 5 November 1998 / Received revision: 25 January 1999 / Accepted: 31 January 1999 相似文献
14.
The effects of different phenolic compound concentrations on the fatty acid composition of Lactobacillus plantarum isolated from traditional home-made olive brines were determined. Increasing amounts of caffeic and ferulic acids induced
a gradual increase in the amounts of myristic, palmitoleic, stearic and 9,10-methylenehexadecanoic (C17Δ, where Δ represents
the cyclopropane group) acid with a concomitant decrease of lactobacillic acid (C19Δ). On the other hand, the addition of tannins induced an increase in the C19Δ level at the expense of vaccenic acid content. The presence of acidic phenols and tannins also affected bacterial growth,
inducing the most obvious effect with tannin at 1 g l−1.
Received: 1 July 1997 / Received revision: 9 September 1997 / Accepted: 15 September 1997 相似文献
15.
Effect of feed composition and upflow velocity on aggregate characteristics in anaerobic upflow reactors 总被引:4,自引:0,他引:4
V. O'Flaherty P. N. L. Lens D. de Beer E. Colleran 《Applied microbiology and biotechnology》1997,47(2):102-107
Two upflow anaerobic hybrid reactors treated lactose and a mixture of ethanol, propionate and butyrate, respectively, at
a volumetric loading rate of 3.7 kg chemical oxygen demand (COD) m−3day−1, a hydraulic retention time of 5 days and a liquid upflow velocity of 0.01 m/h. Under steady-state conditions, the lactose-fed
sludge had much higher (20%–100%) specific methanogenic conversion rates than the volatile-fatty acid␣(VFA)/ethanol-fed sludge
for all substrates tested, including VFA. In both reactors, a flocculant sludge developed, although a much higher content
of extracellular polysaccharide was measured in the lactose-fed sludge [1900 μg compared to 305 μg uronic acid/g volatile
suspended solids (VSS)]. When the liquid upflow velocity of a third, VFA/ethanol-fed reactor was increased to 0.5 m/h, granulation
of the sludge occurred, accompanied by a large increase (200%–500%) in the specific methanogenic conversion rates for the
syntrophic and methanogenic substrates studied. Granulation reduced the susceptibility of the sludge to flotation. Glucose
was degraded at a high rate (100 mg glucose gVSS−1h−1) by the sludge from the third reactor, despite not having been exposed to a sugar-containing influent for 563␣days.
Received: 7 June 1996 / Received revision: 23 September 1996 / Accepted: 29 September 1996 相似文献
16.
P. Ledent H. Michels G. Blackman H. Naveau S. N. Agathos 《Applied microbiology and biotechnology》1999,51(3):370-374
Anionic, cationic, amphoteric and non-ionic surfactants inhibited spore germination and subsequent growth of a mixture of
two Bacillus strains at surfactant concentrations ranging from 1 ppm to 50 ppm. Germination appeared to be more affected than cell growth
by the presence of surfactants, the inhibitory thresholds being largely increased when media were inoculated with vegetative
cells. The bacterial species forming the consortium were incapable of growing on liquid and agar-solidified media prepared
with non-diluted domestic wastewater. Addition of hydrolases (protease, cellulase, α-amylase and lipase) to the wastewater
medium allowed the germination of spores and their vegetative growth.
Received: 9 July 1998 / Received revision: 26 October 1998 / Accepted: 30 October 1998 相似文献
17.
In order to measure the substrate-oxidizing activity of intact cells of Acetobacter pasteurianus no. 2, a given amount of the bacterial cells was immobilized on a carbon-paste electrode, and the current at the electrode
was measured in a buffer solution. When Fe(CN)3−
6 was added to the buffer solution, an anodic current was observed at 0.5 V (against Ag/AgCl). Further, when ethanol was added
to the solution, the current started to increase to reach a steady-state within 3 min. The electrode had a good response to
acetaldehyde and lactic acid as well as ethanol. Culture conditions affected the current response to various substances; the
response of the electrode modified with the cells grown in static culture was much higher than that of the electrode with
the cells grown in shaking culture, and the electrode with ethanol-grown cells had a high response to ethanol and acetaldehyde
compared with that of the electrode with glucose-grown cells. The increase in the amount of the current after the addition
of ethanol (ΔI
EtOH) was linearly proportional to the total number of immobilized cells per electrode in the range 1.0 × 104–1.0 × 108 cells. The ΔI
EtOH values were measured with the electrode prepared with a fixed volume of the cell suspensions taken from the culture at 6-h
intervals; the dependence of the ΔI
EtOH value on time agreed well with the cell growth measured by colony counting and turbidity in the lag and logarithmic phase.
After the logarithmic phase, the value of ΔI
EtOH sharply decreased, resembling to the growth measured by colony counting, rather than by turbidity.
Received: 30 October 1998 / Received revision: 2 February 1999 / Accepted: 5 February 1999 相似文献
18.
S. Chauhan E. Yankelevich V. M. Bystritskii T. K. Wood 《Applied microbiology and biotechnology》1999,52(2):261-266
Degradation of 2,4,5-trichlorophenol (2,4,5-TCP) and 2,3,5,6-tetrachlorophenol (TeCP) was studied using a two-stage approach
that utilized efficient pulse electric discharge (PED) followed by biological degradation with a consortium from acclimated
return activated sludge. The chlorinated phenols were treated in the PED reactor as an aerosol at a voltage of 55–60 kV, a
frequency of 385 Hz, a current of 50–60, and with a 200-ns pulse. As determined by gas chromatography and mass spectrometry
(GC/MS), the first stage converted 500 ppm 2,4,5-TCP to 163 ppm 2,4,5-TCP and dimethyldecene, dichloronaphthalenol, octyl
acetate, and silyl esters. The total carbon content of 2,4,5-TCP after PED treatment was determined to be 228 ± 35 ppm. The
remaining 2,4,5-TCP and the products formed were then mineralized by the acclimated activated sludge in shake flasks; the
initial rate of degradation of 2,4,5-TCP was calculated to be 5 nmol min−1 mg protein−1 at 163 ppm initial concentration (three orders of magnitude higher than the only rate found in the literature). By combining
the two techniques, a synergistic effect (2.3-fold increase in the concentration of 2,4,5-TCP degraded and 3.3-fold increase
in total carbon degraded) was observed, in that bacteria without any treatment degraded a maximum of 70 ppm 2,4,5-TCP but
after PED treatment 163 ppm 2,4,5-TCP was degraded. TeCP was also mineralized by the acclimated activated sludge after treatment
with PED. This two-stage approach was also evaluated using a continuous 1-l fluidized-bed reactor.
Received: 3 November 1998 / Received revision: 28 February 1999 / Accepted: 14 March 1999 相似文献
19.
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
20.
4-Chlorophenol degradation by a bacterial consortium: development of a granular activated carbon biofilm reactor 总被引:5,自引:0,他引:5
Caldeira M Heald SC Carvalho MF Vasconcelos I Bull AT Castro PM 《Applied microbiology and biotechnology》1999,52(5):722-729
A bacterial consortium that can degrade chloro- and nitrophenols has been isolated from the rhizosphere of Phragmitis communis. Degradation of 4-chlorophenol (4-CP) by a consortium attached to granular activated carbon (GAC) in a biofilm reactor was
evaluated during both open and closed modes of operation. During the operation of the biofilm reactor, 4-CP was not detected
in the column effluent, being either adsorbed to the GAC or biodegraded by the consortium. When 4-CP at 100 mg l−1 was fed to the column in open mode operation (20 mg g−1 GAC total supply), up to 27% was immediately available for biodegradation, the rest being adsorbed to the GAC. Biodegradation
continued after the system was returned to closed mode operation, indicating that GAC bound 4-CP became available to the consortium.
Biofilm batch cultures supplied with 10–216 mg 4-CP g−1 GAC suggested that a residual fraction of GAC-bound 4-CP was biologically unavailable. The consortium was able to metabolise
4-CP after perturbations by the addition of chromium (Cr VI) at 1–5 mg l−1 and nitrate at concentrations up to 400 mg l−1. The development of the biofilm structure was analysed by scanning electron microscopy and confocal laser scanning microscopy
(CLSM) techniques. CLSM revealed a heterogeneous structure with a network of channels throughout the biofilm, partially occupied
by microbial exopolymer structures.
Received: 17 March 1999 / Received revision: 27 May 1999 / Accepted: 28 May 1999 相似文献