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1.
Degradation of lignite (low-rank coal) by ligninolytic basidiomycetes and their manganese peroxidase system 总被引:6,自引:0,他引:6
M. Hofrichter D. Ziegenhagen S. Sorge R. Ullrich F. Bublitz W. Fritsche 《Applied microbiology and biotechnology》1999,52(1):78-84
Ligninolytic basidiomycetes (wood and leaf-litter-decaying fungi) have the ability to degrade low-rank coal (lignite). Extracellular
manganese peroxidase is the crucial enzyme in the depolymerization process of both coal-derived humic substances and native
coal. The depolymerization of coal by Mn peroxidase is catalysed via chelated Mn(III) acting as a diffusible mediator with
a high redox potential and can be enhanced in the presence of additional mediating agents (e.g. glutathione). The depolymerization
process results in the formation of a complex mixture of lower-molecular-mass fulvic-acid-like compounds. Experiments using
a synthetic 14C-labeled humic acid demonstrated that the Mn peroxidase-catalyzed depolymerization of humic substances was accompanied by
a substantial release of carbon dioxide (17%–50% of the initially added radioactivity was released as 14CO2). Mn peroxidase was found to be a highly stable enzyme that remained active for several weeks under reaction conditions in
a liquid reaction mixture and even persisted in sterile and native soil from an opencast mining area for some days.
Received: 31 July 1998 / Received revision: 29 September 1998 / Accepted: 2 October 1998 相似文献
2.
A screening identified several bacteria that were able to use chemically heterogeneous low-rank coal liquefaction products
as complex carbon sources for growth. Pseudomonas oleovorans and Rhodococcus ruber accumulated polyhydroxyalkanoic acids (PHA) amounting to 2%–8% of the cell dry weight when the cells were cultivated on these
liquefaction products in the absence of any other carbon source. R. ruber accumulated, in addition to PHA, small amounts of triacylglycerols. The accumulated PHA consisted of 3-hydroxyhexanoate,
3-hydroxydecanoate, and 3-hydroxydodecanoate (P. oleovorans) or 3-hydroxybutyric acid and 3-hydroxyvaleric acid (R. ruber). Low-rank coal liquefaction products obtained from Trichoderma atroviride were better substrates for P. oleovorans than chemically produced fulvic acids.
Received: 13 May 1998 / Received revision: 11 August 1998 / Accepted: 12 August 1998 相似文献
3.
Lignite (brown coal) can be liquefied/solubilized with several fungi by different mechanisms. When applied industrially,
only catalytic mechanisms can compete with chemical methods. The well-known fungal ligninolytic peroxidases are at a disadvantage,
in that the relatively expensive hydrogen peroxide must be used as a cofactor. Comparing several fungal strains, we observed
that the fungus Trametes versicolor is able to decolorize coal-derived humic acids, producing a considerable amount of laccase in the process. During this reaction
the amount of humic acids decreases whilst that of fulvic acids increases; this was verified by optical density measurement
and GPC after the two substance classes had been separated.
Received: 27 August 1998 / Received revision: 4 November 1998 / Accepted: 7 November 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.
Lentinula edodes (Berk.) Pegler was cultivated in liquid media containing malt and yeast extract. Extracellular laccase activity, measured
in the culture fluids, was 5–18 times higher in cultures incubated for 29 days than in cultures incubated for 24 days. The
addition of water-soluble lignin derivatives or Trichoderma sp. in cultures of L. edodes incubated for 11 days increased laccase activity 3- to 20 fold. The higher response was obtained with live mycelium of Trichoderma sp., but cell-free culture fluids of Trichoderma sp. in pure cultures were also effective. Trichoderma sp. induced changes in the laccase isoenzyme pattern as a result of the alteration of laccases secreted by L. edodes and not the induction of new isoforms.
Received: 3 November 1997 / Received revision: 19 January 1998 / Accepted: 24 January 1998 相似文献
6.
Laccase can be used for enzymatic detoxification of lignocellulosic hydrolysates. A Saccharomyces cerevisiae strain with enhanced resistance to phenolic inhibitors and thereby improved ability to ferment lignocellulosic hydrolysates
would presumably be obtained by heterologous expression of laccase. Sequencing of the cDNA for the novel laccase gene lcc2 from the lignin-degrading basidiomycete Trametes versicolor showed that it encodes an isoenzyme of 499 amino-acid residues preceded by a 21-residue signal peptide. By comparison with
Edman degradation data, it was concluded that lcc2 encodes an isoenzyme corresponding to laccase A. The gene product of lcc2 displays 71% identity with the previously characterized T. versicolor lcc1 gene product. An alignment of laccase sequences revealed that the T. versicolor isoenzymes in general are more closely related to corresponding isoenzymes from other white-rot fungi than to the other T. versicolor isoenzymes. The multiplicity of laccase is thus a conserved feature of T. versicolor and related species of white-rot fungi. When the T. versicolor lcc2 cDNA was expressed in S. cerevisiae, the production of active enzyme was strongly dependent on the temperature. After 3 days of incubation, a 16-fold higher laccase
activity was found when a positive transformant was kept at 19 °C instead of 28 °C. Similar experiments with Pichia pastoris expressing the T. versicolor laccase gene lcc1 also showed that the expression level was favoured considerably by lower cultivation temperature, indicating that the observation
made for the S. cerevisiae expression system is of general significance.
Received: 8 December 1998 / Received revision: 9 April 1999 / Accepted: 16 April 1999 相似文献
7.
Cloning of the transketolase gene and the effect of its dosage on aromatic amino acid production in Corynebacterium glutamicum 总被引:2,自引:0,他引:2
Transketolase is a key enzyme of the nonoxidative pentose phosphate pathway. The effect of its overexpression on aromatic
amino acid production was investigated in Corynebacterium glutamicum, a typical amino-acid-producing organism. For this purpose, the transketolase gene of the organism was cloned on the basis
of its ability to complement a C. glutamicum transketolase mutant with pleiotropically shikimic-acid-requiring, ribose- and gluconic-acid-negative phenotype. The gene
was shown by deletion mapping and complementation analysis to be located in a 3.2-kb XhoI-SalI fragment of the genome. Amplification of␣the gene by use of low-, middle-, and high-copy-number vectors in a C. glutamicum strain resulted in overexpression of transketolase activities as well as a␣protein of approximately 83kDa in proportion to
the copy numbers. Introduction of the plasmids into a tryptophan and lysine co-producer resulted in copy-dependent increases
in tryptophan production along with concomitant decreases in lysine production. Furthermore, the presence of the gene in high
copy numbers enabled tyrosine, phenylalanine and tryptophan producers to accumulate 5%–20% more aromatic amino acids. These
results indicate that overexpressed transketolase activity operates to redirect the glycolytic intermediates toward the nonoxidative
pentose phosphate pathway in vivo, thereby increasing the intracellular level of erythrose 4-phosphate, a precursor of aromatic
biosynthesis, in the aromatic-amino-acid-producing C. glutamicum strains.
Received: 27 July 1998 / Received last revision: 12 October 1998 / Accepted: 24 October 1998 相似文献
8.
The production of ligninolytic enzymes was studied in surface cultures of the South American white-rot fungus Nematoloma frowardii b19 and four other strains of this ecophysiological group (Clitocybula dusenii b11, Auricularia sp. m37a, wood isolates u39 and u45), which are able to depolymerize low-rank-coal-derived humic acids with the formation
of fulvic-acid-like compounds. The fungi produced the three crucial enzymes of lignin degradation – lignin peroxidase, manganese
peroxidase and laccase. In the case of N. frowardii b19, laccase and the two peroxidases could be stimulated by veratryl alcohol. Manganese (II) ions (Mn2+) caused a rapid increase of Mn peroxidase activity accompanied by the complete repression of lignin peroxidase. Under nitrogen-limited
conditions the growth as well as the production of ligninolytic enzymes was partly repressed. During the depolymerization
process of coal humic acids using solid agar media, gradients of ligninolytic enzyme activities toward 2,2′-azinobis(3-ethylbenzthiazoline-6-sulphonate)
and syringaldazine were detectable inside the agar medium.
Received: 5 August 1996 / Received revision: 13 November 1996 / Accepted: 15 November 1996 相似文献
9.
Mineralization of synthetic humic substances by manganese peroxidase from the white-rot fungus Nematoloma frowardii 总被引:3,自引:0,他引:3
M. Hofrichter K. Scheibner I. Schneegaß D. Ziegenhagen W. Fritsche 《Applied microbiology and biotechnology》1998,49(5):584-588
A manganese peroxidase preparation from the white-rot fungus Nematoloma frowardii was found to be capable of releasing up to 17% 14CO2 from 14C-labelled synthetic humic substances. The latter were prepared from [U-14C]catechol by spontaneous oxidative polymerization or laccase-catalysed polymerization. The ex-tent of humic substance mineralization
was considerably enhanced in the presence of the thiol mediator glutathione (up to 50%). Besides the evolution of 14CO2, the treatment of humic substances with Mn peroxidase resulted in the formation of lower-molecular-mass products. Analysis
of residual radioactivity by gel-permeation chromatography demonstrated that the predominant molecular masses of the initial
humic substances ranged between 2 kDa and 6 kDa; after treatment with Mn peroxidase, they were reduced to 0.5–2 kDa. The extracellular
depolymerization and mineralization of humic substances by the Mn peroxidase system may play an important role in humus turnover
of habitats that are rich in basidiomycetous fungi.
Received: 25 September 1997 / Received revision: 12 January 1998 / Accepted: 13 January 1998 相似文献
10.
Evaluation of solid substrates for enzyme production by Coriolus versicolor, for use in bioremediation of chlorophenols in aqueous effluents 总被引:1,自引:0,他引:1
In the development of a system for the removal of chlorophenols from aqueous effluents, a range of solid substrates for the
growth of Coriolus versicolor were investigated. Substrates included wood chips, cereal grain, wheat husk and wheat bran. Suitability for transformation
of chlorophenols depended on laccase production by the fungus. The greatest amount of laccase (<25 Units g−1 substrate) was produced on wheat husk and wheat bran over 30 days colonisation. Aqueous extracts of laccase from wheat husk
and wheat bran cultures removed 100% of 2,4-dichlorophenol (50 ppm) from solution within 5 h and 75–80% of pentachlorophenol
(50 ppm) within 24 h. Wheat bran was formulated into pellets with biscuit flour to provide a compact substrate for fungal
immobilisation. Addition of 8–12% yeast extract to the pellets increased laccase production five-fold. Colonised pellets were
added to chlorophenol solutions in 200–4000-ml bioreactors, resulting in >90% removal of chlorophenols within 100 min.
Received: 10 April 2000 / Received revision: 4 July 2000 / Accepted: 10 July 2000 相似文献
11.
Laccase, purified from Coriolus versicolor, removed pentachlorophenol (PCP) from solution at pH 5, depending on initial PCP concentration and amount of laccase. With
100 units of laccase, 100% of 25 μg ml−1 PCP and 60% of 200 μg ml−1 PCP were removed respectively over 72 h. No free chloride was released in the reaction. In reaction with 100 μg PCP, products
were primarily polymers (about 80,000 MW) with only 2–3 pg of o- and p-chloranils formed. Polymers were stable to acid hydrolysis and no release of PCP, or other low-molecular-weight products,
was detected over several weeks. Laccase has a potential use in the biotreatment of aqueous effluents containing PCP, with
polymerised products being removed from solution due to their high molecular weight.
Received: 7 June 1999 / Received revision: 18 August 1999 / Accepted: 2 September 1999 相似文献
12.
K. L. Larsen H. J. S. Christensen F. Mathiesen L. H. Pedersen W. Zimmermann 《Applied microbiology and biotechnology》1998,50(3):314-317
The conversion of soluble starch to cyclomaltohexaose (α-CD), cyclomaltoheptaose (β-CD), cyclomaltooctaose (γ-CD) and cyclomaltononaose
(δ-CD) by cyclodextrin glycosyltransferases (E.C. 2.4.1.19) from Bacillus spp. and bacterial isolates was studied. The results show that δ-CD was formed by all the enzymes investigated in the range
of 5%–11.5% of the total amount of α-, β-, γ-, and δ-CD produced.
Received: 17 February 1998 / Received revision: 18 May 1998 / Accepted: 21 May 1998 相似文献
13.
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
14.
A. E. Cazemier J. C. Verdoes H. J. M. Op den Camp J. H. P. Hackstein A. J. J. van Ooyen 《Applied microbiology and biotechnology》1999,52(2):232-239
A gene library of Cellulomonas pachnodae was constructed in Escherichia coli and was screened for endoglucanase activity. Five endoglucanase-positive clones were isolated that carried identical DNA
fragments. The gene, designated cel6A, encoding an endoglucanase enzyme, belongs to the glycosyl hydrolase family 6 (cellulase family B). The recombinant Cel6A
had a molecular mass of 53 kDa, a pH optimum of 5.5, and a temperature optimum of 50–55 °C. The recombinant endoglucanase
Cel6A bound to crystalline cellulose and beech litter. Based on amino acid sequence similarity, a clear cellulose-binding
domain was not distinguished. However, the regions in the Cel6A amino acid sequence at the positions 262–319 and 448–473,
which did not show similarity to any of the known family-6 glycosyl hydrolases, may be involved in substrate binding.
Received: 14 January 1999 / Received revision: 29 March 1999 / Accepted: 6 April 1999 相似文献
15.
Oxidation of aromatic alcohols, such as non-phenolic lignin model compounds, by oxidised species of 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonic
acid) (ABTS) has been investigated. The cation radical and dication formed from ABTS were both capable of oxidising aromatic
alcohols to aldehydes. The reactions terminated at the level of the aldehyde and no acids were formed. The cation radical
and dication worked in a cycle as an electron-transfer compound between an oxidant and alcohol. In addition to the oxidation
of the primary benzyl-hydroxyl group, an oxidation of the secondary α-hydroxyl group to the ketone by the dication was possible.
All distinguishing features of these reactions corresponded to the results of the oxidation performed by the laccase of Trametes versicolor in the presence of ABTS. The decomposition products from the dication alone and ABTS with laccase confirmed the supposition
that the dication was involved in the laccase mediator system. A reaction mechanism based on deprotonation of the alcohol
cation radical was predicted to play a key role in the irreversible followup reaction and to be the driving force of the process.
Received: 8 June 1998 / Received revision: 23 September 1998 / Accepted: 2 October 1998 相似文献
16.
E. J. Bormann M. Leißner M. Roth B. Beer K. Metzner 《Applied microbiology and biotechnology》1998,50(5):604-607
Polyhydroxybutyrate (PHB) was produced by Ralstonia eutropha DSM 11348 (formerly Alicaligenes eutrophus) in media containing 20–30 g l−1 casein peptone or casamino acids as sole sources of nitrogen. In fermentations using media based on casein peptone, permanent
growth up to a cell dry mass of 65 g l−1 was observed. PHB accumulated in cells up to 60%–80% of dry weight. The lowest yields were found in media without any trace
elements or with casamino acids added only. The residual cell dry masses were limited to 10–15 g l−1 and did not contain PHB. The highest productivity amounted to 1.2 g PHB l−1 h−1. The mean molecular mass of the biopolymer was determined as 750 kDa. The proportion of polyhydroxyvalerate was less than
0.2% in PHB. The bioprocess was scaled up to a 300-l plant. During a fermentation time of 39 h the cells accumulated PHB to
78% w/w. The productivity was 0.98 g PHB l−1 h1.
Received: 8 July 1998 / Accepted: 26 August 1998 相似文献
17.
The gene dak1 encoding a dihydroxyacetone kinase (DHAK) isoenzyme I, one of two isoenzymes in the Schizosaccharomyces pombe IFO 0354 strain, was cloned and sequenced. The dak1 gene comprises 1743 bp and encodes a protein of 62 245 Da. The deduced amino acid sequence showed a similarity to a putative
DHAK of Saccharomyces cerevisiae and DHAK of Citrobacter freundii. The dak1 gene was expressed at a high level in Escherichia coli, and the recombinant enzyme was purified to homogeneity and characterized. The acetone powder of recombinant E. coli cells was used to produce dihydroxyacetone phosphate.
Received: 25 August 1998 / Received revision: 22 September 1998 / Accepted: 11 October 1998 相似文献
18.
Composition of the cell walls of several yeast species 总被引:14,自引:0,他引:14
Cell walls, representing 26%–32% of the cell dry weight, were prepared from several strains of the yeasts Kloeckera apiculata, Debaryomyces hansenii, Zygosaccharomyces bailii,Kluyveromyces marxianus and Saccharomyces cerevisiae. Extraction of the walls with potassium hydroxide at 4 °C, followed by saturation of the alkali-soluble extract with ammonium
sulphate gave fractions of mannoprotein, alkali-soluble glucan and alkali-insoluble glucan. Chitin was associated with the
alkali-insoluble glucan. The proportions of the different fractions within the walls varied with the species and strain. Mannoprotein
comprised between 25% and 34% of the walls, the content of alkali-insoluble glucan ranged from 15% to 48%, and the content
of alkali-soluble glucan ranged from 10% to 48%. There was significant variation in the physical appearance of the alkali-soluble
glucans and the relative viscosity of suspensions of these glucans. The yeasts could represent novel sources of polysaccharides
with industrial and medical applications.
Received: 30 December 1997 / Received revision: 24 March 1998 / Accepted: 27 March 1998 相似文献
19.
Production of ligninolytic enzymes and synthetic lignin mineralization by the bird's nest fungus Cyathus stercoreus 总被引:3,自引:0,他引:3
Production of ligninolytic enzymes and degradation of 14C-ring labeled synthetic lignin by the white-rot fungus Cyathus stercoreus ATCC 36910 were determined under a variety of conditions. The highest mineralization rate for 14C dehydrogenative polymerizates (DHP; 38% 14CO2 after 30 days) occurred with 1 mM ammonium tartrate as nitrogen source and 1% glucose as additional carbon source, but levels
of extracellular laccase and manganese peroxidase (MnP) were low. In contrast, 10 mM ammonium tartrate with 1% glucose gave
low mineralization rates (10% 14CO2 after 30 days) but higher levels of laccase and manganese peroxidase. Lignin peroxidase was not produced by C. stercoreus under any of the studied conditions. Mn(II) at 11 ppm gave a higher rate of 14C DHP mineralization than 0.3 or 40 ppm, but the highest manganese peroxidase level was obtained with Mn(II) at 40 ppm. Cultivation
in aerated static flasks gave rise to higher levels of both laccase and manganese peroxidase compared to the levels in shake
cultures. 3,4-Dimethoxycinnamic acid at 500 μM concentration was the most effective inducer of laccase of those tested. The
purified laccase was a monomeric glycoprotein having an apparent molecular mass of 70 kDa, as determined by calibrated gel
filtration chromatography. The pH optimum and isoelectric point of the purified laccase were 4.8 and 3.5, respectively. The
N-terminal amino acid sequence of C. stercoreus laccase showed close homology to the N-terminal sequences determined from other basidiomycete laccases. Information on C. stercoreus, whose habitat and physiological requirements for lignin degradation differ from many other white-rot fungi, expands the
possibilities for industrial application of biological systems for lignin degradation and removal in biopulping and biobleaching
processes.
Received: 29 January 1999 / Received revision: 5 July 1999 / Accepted: 9 July 1999 相似文献
20.
Residues and coal fractions that remained after the biosolubilization of Rhenish brown coal by strains of Lentinula edodes and Trametes versicolor have been studied by Curie-point pyrolysis/gas chromatography/mass spectrometry using tetraethylammonium hydroxide (NEt4OH) at 610 °C. To differentiate methyl derivatives of esters and ethers from free or bound hydroxyl and carboxyl groups NEt4OH was used in the thermochemolysis experiments instead the commonly used tetramethylammonium hydroxide. A comparison of humic
acid fractions before and after fungal attack shows considerable alteration of the soluble macromolecules of coal. Depending
on the coal fraction studied and the fungi used, the assortment of fatty acid esters released during the pyrolysis varies
significantly. Furthermore, dicarbonic acid ethyl diesters as well as ethyl derivatives of aromatic ethers and acids yield
information about humic acid structure and the biosolubilization of brown coal. Variations in the mixture produced are possibly
caused by differences in the pattern of extracellular enzymes secreted that attack the macromolecular structural elements
of brown coal. Therefore pyrolysis of native and microbiologically altered geomacromolecules using NEt4OH allows one to differentiate between free hydroxyl groups as well as substances that are attached to humic substances via
ester or ether bridges, and their methylated counterparts.
Received: 13 July 1998 / Received revision: 12 October 1998 / Accepted: 16 October 1998 相似文献