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1.
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
2.
Degradation of styrene by white-rot fungi 总被引:2,自引:0,他引:2
A. Braun-Lüllemann A. Majcherczyk A. Hüttermann 《Applied microbiology and biotechnology》1997,47(2):150-155
Degradation of styrene in the gaseous phase was investigated for white-rot fungi Pleurotus ostreatus (two strains), Trametes versicolor, Bjerkandera adusta and Phanerochaete chrysosporium. Fungi were grown in liquid culture and the gas/mycelium contact surface was enhanced with the help of perlite. The influence
of various inducers on styrene degradation was studied. The best inducers for styrene degradation were lignosulphonate for
P. ostreatus and T. versicolor and wood meal for B. adusta and P. chrysosoporium. Under these conditions all fungi were able to degrade styrene almost completely in 48 h at a concentration of 44 μmol/250 ml
total culture volume; one strain of P. ostreatus was able to remove 88 μmol styrene under these conditions. Three transformation products of [14C]styrene in cultures of P. ostreatus were identified: phenyl-1,2-ethanediol, 2-phenylethanol and benzoic acid; 4% of the styrene was metabolised to CO2 in 24 h and no other volatile products were found.
Received: 16 July 1996 / Received revision: 23 September 1996 / Accepted: 29 September 1996 相似文献
3.
D. Licht S. S. Johansen E. Arvin B. K. Ahring 《Applied microbiology and biotechnology》1997,47(2):167-172
Degradation of indole and quinoline by Desulfobacterium␣indolicum was studied in batch cultures. The first step in the degradation pathway of indole and quinoline was a hydroxylation at the
2 position to oxindole and 2-hydroxyquinoline respectively. These hydroxylation reactions followed saturation kinetics. The
kinetic parameters for indole were an apparent maximum specific transformation rate (V
Amax) of 263 μmol mg total protein−1 day−1 and an apparent half-saturation constant (K
Am) of 139 μM. The V
Amax for quinoline was 170 μmol mg total protein−1 day−1 and K
Am was 92 μM. Oxindole inhibited indole hydroxylation whereas 2-hydroxyquinoline stimulated quinoline hydroxylation. An adaptation
period of approximately 20 days was required before transformation of 2-hydroxyquinoline in cultures previously grown on quinoline.
Indole and quinoline were hydroxylated with a lag phase shorter than 4 h in a culture adapted to ethanol. Chloramphenicol
inhibited the hydroxylation of indole and quinoline in ethanol-adapted cells, indicating an inducible enzyme system. Chloramphenicol
had no effect on the hydroxylation of indole in quinoline-adapted cells or on the hydroxylation of quinoline in indole-adapted
cells. This indicated that it was the same inducible enzyme system that hydroxylated indole and quinoline.
Received: 16 July 1996 / Received revision: 23 September 1996 / Accepted: 29 September 1996 相似文献
4.
Desulfomonile tiedjei, a strict anaerobe capable of reductively dechlorinating 3-chlorobenzoate, also dechlorinates tetrachloroethene and trichloroethene. It is not known, however, if the aryl and aliphatic dechlorination activities are catalyzed by the same enzymatic system. Cultures induced for 3-chlorobenzoate activity dechlorinated tetrachloroethene and trichloroethene to lower chlorinated products while uninduced parallel cultures did not dechlorinate either substrate. The observed rate of PCE dechlorination in induced cultures was 22 µmol h–1 g protein–1, which is considerably faster than previous rates obtained with defined cultures of this organism. These results show that both dechlorination activities are co-induced and therefore, that the dechlorination mechanisms may share at least some components.Abbreviations PCE
tetrachloroethene
- TCE
trichloroethene
-
cis-DCE
cis-dichloroethene
-
trans-DCE
trans-dichloroethene
- 3FBz
3-fluorobenzoate
- 3ClBz
3-chlorobenzoate 相似文献
5.
J. H. de Best A. Hage H. J. Doddema D. B. Janssen W. Harder 《Applied microbiology and biotechnology》1999,51(2):277-283
A methanogenic mixed population in a packed-bed reactor completely transformed 1,1,1-trichloroethane (10 μM) to chloroethane
by a cometabolic process. Chloroethane was not further transformed. Acetate and methanol served as electron donors. Complete
transformation of 1,1,1-trichloroethane to chloroethane only occurred when sufficient electron donor was fed into the reactor.
Otherwise, besides chloroethane, 1,1-dichloroethane was also found as a product. The products of 1,1,1-trichloroethane transformation
also depended on the type of electron donor present. With acetate, the degree of dechlorination was higher, i.e. more 1,1,1-trichloroethane
was transformed to chloroethane than with methanol. In an enrichment culture obtained from the reactor contents, 1,1,1-trichloroethane
was only transformed to 1,1-dichloroethane and was not further metabolized. Methanol, acetate, formate, ethanol, 2-propanol,
trimethylamine and H2, but not dimethylamine and methylamine, served as electron donors for 1,1,1-trichloroethane transformation by this enrichment
culture. Both nitrate and nitrite inhibited 1,1,1-trichloroethane transformation; while nitrate completely inhibited 1,1,1-trichloroethane
dechlorination, some conversion did occur in the presence of nitrite. The product(s) of this conversion remain unknown, since
no chlorinated hydrocarbons were detected.
Received: 19 June 1998 / Received revision: 14 September 1998 / Accepted: 17 September 1998 相似文献
6.
An anaerobic enrichment culture with glucose as the sole source of carbon and energy plus trichloroethene (TCE) as a potential electron acceptor was inoculated with material from a full size anaerobic charcoal reactor that biologically eliminated dichloromethane from contaminated groundwater (Stromeyer et al. 1991). In subcultures of this enrichment complete sequential transformation of 10 µM TCE viacis-dichloroethene and chloroethene to ethene was reproducibly observed. Maintenance of this activity on subcultivation required the presence of TCE in the medium. The enrichment culture was used to inoculate an anaerobic fixed-bed reactor containing sintered glass Raschig elements as support material. The reactor had a total volume of 1780 ml and was operated at 20 °C in an up-flow mode with a flow rate of 50 ml/h. It was fed continuously with 2 mM glucose and 55 µM TCE. Glucose was converted to acetate as the major product and to a minor amount of methane; TCE was quantitatively dehalogenated to ethene. When, in addition to TCE, tetrachloroethene or 1,2-dichloroethane were added to the system, these compounds were also dehalogenated to ethene. In contrast, 1,1,1-trichloroethane was not dehalogenated, but at 40 µM severely inhibited acetogenesis and methanogenesis. When the concentration of TCE in the feed was raised to 220 µM, chloroethene transiently accumulated, but after an adaptation period ethene was again the only volatile product detected in the effluent. The volumetric degradation rate at this stage amounted to 6.2 µmol/l/h. Since complete transformation of TCE occurred in the first sixth of the reactor volume, the degradation capacity of the system is estimated to exceed this value by factor of about ten.Abbreviations CA
chloroethane
- 1,1-DCA
1,1-dichloroethane
- 1,2-DCA
1,2-dichloroethane
- 1,1-DCE
1,1-dichloroethene
- c-DCE
cis-1,2-dichloroethene
- t-DCE
trans-1,2-dichloroethene
- PCE
tetrachloroethene, perchloroethene
- 1,1,1-TCA
1,1,1-trichloroethane
- TCE
trichloroethene
- VC
chloroethene, vinyl chloride 相似文献
7.
Reductive dechlorination of tetrachloroethene by a stepwise catalysis of different organohalide respiring bacteria and reductive dehalogenases 总被引:1,自引:0,他引:1
Maillard J Charnay MP Regeard C Rohrbach-Brandt E Rouzeau-Szynalski K Rossi P Holliger C 《Biodegradation》2011,22(5):949-960
The enrichment culture SL2 dechlorinating tetrachloroethene (PCE) to ethene with strong trichloroethene (TCE) accumulation
prior to cis-1,2-dichloroethene (cis-DCE) formation was analyzed for the presence of organohalide respiring bacteria and reductive dehalogenase genes (rdhA). Sulfurospirillum-affiliated bacteria were identified to be involved in PCE dechlorination to cis-DCE whereas “Dehalococcoides”-affiliated bacteria mainly dechlorinated cis-DCE to ethene. Two rdhA genes highly similar to tetrachloroethene reductive dehalogenase genes (pceA) of S. multivorans and S. halorespirans were present as well as an rdhA gene very similar to the trichloroethene reductive dehalogenase gene (tceA) of “Dehalococcoides ethenogenes” strain 195. A single strand conformation polymorphism (SSCP) method was developed allowing the simultaneous detection of
the three rdhA genes and the estimation of their abundance. SSCP analysis of different SL2 cultures showed that one pceA gene was expressed during PCE dechlorination whereas the second was expressed during TCE dechlorination. The tceA gene was involved in cis-DCE dechlorination to ethene. Analysis of the internal transcribed spacer region between the 16S and 23S rRNA genes revealed
two distinct sequences originating from Sulfurospirillum suggesting that two Sulfurospirillum populations were present in SL2. Whether each Sulfurospirillum population was catalyzing a different dechlorination step could however not be elucidated. 相似文献
8.
Purification and characterization of the tetrachloroethene reductive dehalogenase of strain PCE-S 总被引:5,自引:0,他引:5
The membrane-associated tetrachloroethene reductive dehalogenase from the tetrachloroethene-reducing anaerobe, strain PCE-S,
was purified 165-fold to apparent homogeneity in the presence of the detergent Triton X-100. The purified dehalogenase catalyzed
the reductive dechlorination of tetrachloroethene to trichloroethene and of trichloroethene to cis-1,2-dichloroethene with reduced methyl viologen as the electron donor, showing a specific activity of 650 nkat/mg protein.
The apparent K
m values of the enzyme for tetrachloroethene, trichloroethene, and methyl viologen were 10 μM, 4 μM, and 0.3 mM, respectively.
SDS-PAGE revealed a single protein band with an apparent molecular mass of 65 kDa. The apparent molecular mass of the native
enzyme was 200 kDa as determined by gel filtration. Tetrachloroethene dehalogenase contained 0.7 ± 0.3 mol corrinoid, 1.0
± 0.3 mol cobalt, 7.8 ± 0.5 mol iron, and 10.3 ± 2.0 mol acid-labile sulfur per mol subunit. The pH optimum was approximately
7.2, and the temperature optimum was approximately 50 °C. The dehalogenase was oxygen-sensitive with a half-life of approximately
50 min. The N-terminal amino acid sequence of the enzyme was determined, and no significant similarity was found to any part
of the amino acid sequence of the tetrachloroethene (PCE) reductive dehalogenase from Dehalospirillum multivorans.
Received: 4 December 1997 / Accepted: 10 February 1998 相似文献
9.
Characterization and optimization of a two-phase partitioning bioreactor for the biodegradation of phenol 总被引:2,自引:0,他引:2
An electrochemical reactor employing activated carbon fibers (ACF) was constructed for the disinfection of bacteria in drinking
water. The application of an alternating potential of 1.0 V and −0.8 V versus a saturated calomel electrode, for disinfecting
and desorbing bacteria, enabled reactor operation for 840 h. Drinking water was passed through the reactor in stop/flow mode:
300 ml/min flow for 12 h and no flow for 12 h, alternately. The bacterial cell density in treated water was always been less
than 20 cells/ml. It was also found that the formation of biofilm on the ACF reactor caused an increase in current, enabling
the self-detection of microbial fouling.
Received: 19 February 1996 / Received last revision: 23 July 1996 / Accepted: 2 September 1996 相似文献
10.
Complete reductive dechlorination of tetrachloroethene to ethene by anaerobic microbial enrichment culture developed from sediment 总被引:1,自引:0,他引:1
Byung-Hyuk Kim Kyung-Hwa Baek Dae-Hyun Cho Youlboong Sung Sung-Cheol Koh Chi-Yong Ahn Hee-Mock Oh Hee-Sik Kim 《Biotechnology letters》2010,32(12):1829-1835
A mixed, anaerobic microbial enrichment culture, AMEC-4P, was developed that uses lactate as the electron donor for the reductive
dechlorination of tetrachloroethene (PCE) to ethene. AMEC-4P consistently and completely converted 2 mM PCE to cis-1,2-dichloroethene (cis-DCE) within 13 days, and the intermediate, cis-DCE, was then completely dechlorinated to ethene after 130 days. Dechlorination rates for PCE to cis-DCE, cis-DCE to VC, and VC to ethene were 243, 27, and 41 μmol/l/day, respectively. Geobacter lovleyi and a Dehalococcoides sp. were identified from their 16S rRNA sequences to be the dominant phylotypes in AMEC-4P. 相似文献
11.
M. B. Cassidy K. W. Shaw H. Lee J. T. Trevors 《Applied microbiology and biotechnology》1997,47(2):108-113
A pentachlorophenol(PCP)-degrading Pseudomonas sp. strain UG30 was encapsulated in κ-carrageenan for use in PCP degradation. Free and encapsulated cells were compared for
their ability to dechlorinate and mineralize 100–800 μg/ml sodium pentachlorophenate in broth. Dechlorination was measured
with a chloride ion electrode, and mineralization was measured by 14CO2 evolution from radiolabelled [U-14C]PCP. Free and encapsulated Pseudomonas sp. UG30 cells mineralized up to 200 μg/ml and 600 μg/ml PCP, respectively, after 21 days. Encapsulation of UG30 cells provided
a protective effect, allowing dechlorination and mineralization of high levels of PCP to occur.
Received: 3 May 1996 / Received revision: 4 September 1996 / Accepted: 13 September 1996 相似文献
12.
M D Lee G E Quinton R E Beeman A A Biehle R L Liddle D E Ellis RJ Buchanan Jr 《Journal of industrial microbiology & biotechnology》1997,18(2-3):106-115
For the full scale implementation of in situ anaerobic bioremediation of tetrachloroethene (PCE) in groundwater, the following issues must be addressed: which organic
substrates at which concentration would be most effective in promoting dechlorination and are economical; how far the substrate,
electron acceptor, and nutrients can be transported in the aquifer; and the placement of delivery and recovery wells for
distributing these amendments. In a microcosm study, almost all of the tested inexpensive substrates supported reductive
dechlorination of PCE through vinyl chloride (VC) under methanogenic conditions. A minimum of about 60 mg L−1 of organic carbon was needed to dechlorinate 23 μM PCE with a single feeding. In a second microcosm study dechlorination
stopped at 1,2-dichloroethene (DCE) in microcosms fed higher concentrations of several substrates. At the highest concentrations
the substrates inhibited DCE production. Three field tracer tests were conducted to evaluate methods to distribute the amendments
across the aquifer. The natural groundwater gradient is not sufficient to distribute substrate evenly. Groundwater injection
at 60 times the natural flux rate increased the distribution of substrate. A mixing strategy of cross-gradient injection
further increased the distribution of the substrate. Ammonia-nitrogen, sulfate, and phosphate were retarded relative to
the substrate and inorganic tracer.
Received 30 October 1995/ Accepted in revised form 07 June 1996 相似文献
13.
Cultures able to dechlorinate cis-1,2-dichloroethene (cDCE) were selected with ethene (3–20%, v/v) as the sole source of carbon and energy. One mixed culture (K20) could degrade
cDCE (400 μmol l–1) or vinyl chloride (100 μmol l–1) in the presence of ethene (≤ 80 μmol l–1 and ≤ 210 μmol l–1, respectively). This culture consists of at least five bacterial strains. All five strains were able to degrade cDCE cometabolically in pure culture. The mixed culture K20 was highly tolerant against cDCE (up to 6 mmol l–1 in the liquid phase). Degradation of cDCE (200 μmol l–1) was not affected by the presence of trichloroethene (100 μmol l–1) or tetrachloroethene (100 μmol l–1). Transformation yields (Ty, defined as unit mass of chloroethene degraded per unit mass of ethene consumed) of the mixed culture K20 were relatively
high (0.51 and 0.61 for cDCE and vinyl chloride, respectively). The yield for cDCE with ethene as auxiliary substrate was ninefold higher than any values reported with methane or methane/formate as auxiliary
substrate. The viability of the cells of the mixed culture K20 (0.3 mg of cells ml–1) was unaffected by the transformation of ≤ 200 μmol l–1
cDCE in 300 min.
Received: 9 March 1999 / Accepted: 21 July 1999 相似文献
14.
J. H. de Best H. Jongema A. Weijling H. J. Doddema D. B. Janssen W. Harder 《Applied microbiology and biotechnology》1997,48(3):417-423
Biotransformation of 1,1,1-trichloroethane (CH3CCl3) was observed in an anaerobic packed-bed reactor under conditions of both sulfate reduction and methanogenesis. Acetate (1 mM)
served as an electron donor. CH3CCl3 was completely converted up to the highest investigated concentration of 10 μM. 1,1-Dichloroethane and chloroethane were
found to be the main transformation products. A fraction of the CH3CCl3 was completely dechlorinated via an unknown pathway. The rate of transformation and the transformation products formed depended
on the concentrations of CH3CCl3, acetate and sulfate. With an increase in sulfate and CH3CCl3 concentrations and a decrease in acetate concentration, the degree of CH3CCl3 dechlorination decreased. Both packed-bed reactor studies and batch experiments with bromoethanesulfonic acid, an inhibitor
of methanogenesis, demonstrated the involvement of methanogens in CH3CCl3 transformation. Batch experiments with molybdate showed that sulfate-reducing bacteria in the packed-bed reactor were also
able to transform CH3CCl3. However, packed-bed reactor experiments indicated that sulfate reducers only had a minor contribution to the overall transformation
in the packed-bed reactor.
Received: 22 January 1997 / Received revision: 12 May 1997 / Accepted: 19 May 1997 相似文献
15.
K. Scheibner M. Hofrichter A. Herre J. Michels W. Fritsche 《Applied microbiology and biotechnology》1997,47(4):452-457
Within a screening program, 91 fungal strains belonging to 32 genera of different ecological and taxonomic groups (wood-
and litter-decaying basidiomycetes, saprophytic micromycetes) were tested for their ability to metabolize and mineralize 2,4,6-trinitrotoluene
(TNT). All these strains metabolized TNT rapidly by forming monoaminodinitrotoluenes (AmDNT). Micromycetes produced higher
amounts of AmDNT than did wood- and litter-decaying basidiomycetes. A significant mineralization of [14C]TNT was only observed for certain wood- and litter-decaying basidiomycetes. The most active strains, Clitocybula dusenii TMb12 and Stropharia rugosa-annulata DSM11372 mineralized 42 % and 36 % respectively of the initial added [14C]TNT (100 μM corresponding to 4.75 μCi/l) to 14CO2 within 64 days. Micromycetes (deuteromycetes, ascomycetes, zygomycetes) proved to be unable to mineralize [14C]TNT significantly.
Received: 8 August 1996 / Received revision: 16 December 1996 / Accepted: 20 December 1996 相似文献
16.
I. Besson C. Creuly J. B. Gros C. Larroche 《Applied microbiology and biotechnology》1997,47(5):489-495
2,5-Dimethylpyrazine (2,5-DMP) and tetramethylpyrazine (TTMP) were produced using Bacillus subtilis IFO 3013 grown on soybeans. Solid-state cultivations were carried out either in 100-ml bottles or in a fixed-bed column reactor,
both systems being at 27 °C. Optimization studies showed that the best way to produce the two above aroma compounds involved
two separate processes. 2,5-DMP was obtained using soybeans enriched with 75 g threonine/kg initial dry weight (i.d.w.), giving
0.85 g metabolite/kg i.d.w. after 6 days. TTMP production involved addition of 90 g/kg i.d.w. acetoin to soybeans, and 2.5 g/kg
i.d.w. was recovered after 14 days. These results demonstrated the suitability of solid-state cultivation for production of
high-added-value compounds.
Received: 30 September 1996 / Received revision: 23 December 1996 / Accepted: 30 December 1996 相似文献
17.
Plant regeneration via somatic embryogenesis was achieved from leaf petioles of Pelargonium sp. `Frensham' cultured on Murashige and Skoog medium containing 15 μM N6-benzyladenine, and 5 μM α-naphthaleneacetic acid (NAA). More than 80% of these somatic embryos converted into plants when
isolated and cultured on Murashige and Skoog medium supplemented with 15 μM NAA. Stable transgenic plants were obtained by
co-cultivation of the petioles (prior to culture) with Agrobacterium tumefaciens strains LBA4404 (harbouring a binary vector pBI121 carrying the nptII and gus genes) and LBG66 (harbouring a binary plasmid pJQ418 carrying the gus/int:nptII fusion gene). Transformants were selected using kanamycin and transformation was verified by β-glucuronidase histochemical
assay and polymerase chain reaction. Southern analysis further confirmed the integration of these genes into the genome of
transgenic plants. We report here for the first time, an Agrobacterium-mediated model transformation system coupled with regeneration via somatic embryogenesis for production of transgenics in
Pelargonium sp.
Received: 20 September 1996 / Accepted: 13 November 1996 相似文献
18.
P. J. M. Teunissen H. J. Swarts J. A. Field 《Applied microbiology and biotechnology》1997,47(6):695-700
Ligninolytic basidiomycetes were screened for their ability to produce the tetrachlorinated hydroquinone metabolites drosophilin
A (DA, tetrachloro-4-methoxyphenol) and drosophilin A methyl ether (DAME, tetrachloro-1,4-dimethoxybenzene). Five fungal strains
produced these metabolites in detectable amounts, including strains from Bjerkandera and Peniophora, which are genera not previously known for DA or DAME production. Phellinus fastuosus ATCC26.125 had the highest and most reliable production of DA and DAME in peptone medium, respectively 15–60 μM and 4–40 μM.
This fungus was used to study culture conditions that could increase DAME production. A fourfold increase in DAME production
was found after the addition of hydroquinone to growing cultures of P. fastuosus. Therefore, hydroquinone is postulated to be a possible biosynthetic precursor of DAME in the fungus. Antagonising P. fastuosus by adding filter-sterilised culture fluid of a competing fungus, Phlebia radiata, increased DAME production significantly by tenfold. This result suggests that DAME production is elicited by compounds present
in the culture fluid of P. radiata, indicating that DAME has an antibiotic function in P. fastuosus.
Received: 17 September 1996 / Received revision: 7 February 1997 / Accepted: 15 February 1997 相似文献
19.
Influence of the starting microbial nucleus type on the anaerobic granulation dynamics 总被引:4,自引:0,他引:4
The influence of four different granulation precursors, syntroph-enriched methanogenic consortia, Methanosaeta-enriched, Methanosarcina-enriched nuclei and acidogenic flocs, on the time course of complex granule development and the lag time for start-up was
investigated in four upflow anaerobic sludge-bed and filter reactors. Although the operational conditions allowed the maintenance
of the same specific growth rate of biomass in the four reactors, granulation proceeded rapidly with syntroph/methanogenic
consortia, Methanosaeta and Methanosarcina nuclei. However, granulation was significantly retarded when acidogenic flocs were used as precursors. The granule mean Sauter
diameter increased rapidly in the reactor inoculated with syntroph/methanogenic consortia, Methanosaeta and Methanosarcina nuclei and reached, at the end of the experiment, 3.1, 2.7 and 2.4 mm compared to 1.1 mm in that inoculated with acidogenic
flocs. This corresponded to a rate of granule size increase of 31, 21, 18 μm/day in syntroph/methanogenic consortia, Methanosaeta and Methanosarcina nuclei, respectively, compared to 7 μm/day in acidogenic flocs. Biomass specific activities (i.e. acidogenic, syntrophic
and methanogenic activities) increased stepwise in all reactors with time, especially in those inoculated with syntroph/methanogenic
consortia and Methanosaeta nuclei. From these results it appears that syntrophs and Methanosaeta spp. play an important role in the anaerobic granulation process.
Received: 25 January 1996 / Received revision: 3 September 1996 / Accepted: 13 September 1996 相似文献
20.
The magnesium content of Saccharomyces cerevisiae was found to vary by up to fivefold at differing␣ stages of batch growth and during growth in the presence of differing magnesium
concentrations. Excess Mg was primarily sequestered in vacuoles. Mn2+-uptake experiments revealed that Mg-enriched cells had a markedly reduced capacity for Mn2+ accumulation. For example, after 6 h incubation in the presence of 50 μM Mn2+, Mn levels were approximately twofold higher in cells previously grown in unsupplemented medium than in those from Mg-supplemented
medium. These differences were further accentuated at higher Mn2+ concentrations and were not attributable to altered cell-surface charge or altered cell-surface Mn2+ binding. Cellular Mg status also influenced Mn toxicity towards S. cerevisiae. During exposure to 5 mM Mn2+, 50% reductions in the viability of cells with initial Mg contents of approximately 1400 and 2700 nmol (109 cells)−1 occurred after approximately 1.6 h and 3.6 h respectively. In cells containing 3300 nmol Mg (109 cells)−1, more than 75% viability was still maintained after 7 h incubation with 5 mM Mn2+. It is concluded that Mn2+ uptake and toxicity in S. cerevisiae are strongly influenced by intracellular Mg, possibly through Mg-dependent regulation of divalent-cation transport activity.
Received: 15 May 1996 / Received revision: 13 September 1996 / Accepted: 22 September 1996 相似文献