共查询到20条相似文献,搜索用时 15 毫秒
1.
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
2.
Fernández MJ Adrio JL Piret JM Wolfe S Ro S Demain AL 《Applied microbiology and biotechnology》1999,52(4):484-488
Growth of Streptomyces clavuligerus NP1 in the presence of methanol or ethanol resulted in a marked increase in production of cephalosporin(s) from penicillin
G by resting cells. The mycelium produced in alcohol-supplemented medium was fragmented and dispersed as compared with growth
in control medium. HPLC analysis showed that at least two products were present in the biotransformation supernatant fluid
after 1 h incubation. One of them has been identified as deacetoxycephalosporin G (DAOG).
Received: 9 December 1998 / Received revision: 29 March 1999 / Accepted: 16 April 1999 相似文献
3.
Babu KR Swaminathan S Marten S Khanna N Rinas U 《Applied microbiology and biotechnology》2000,53(6):655-660
Escherichia coli TG1 transformed with a temperature-regulated interferon-α expression vector was grown to high cell density in defined medium
containing glucose as the sole carbon and energy source, utilizing a simple fed-batch process. Feeding was carried out to
achieve an exponential increase in biomass at growth rates which minimized acetate production. Thermal induction of such high
cell density cultures resulted in the production of ∼4 g interferon-α/l culture broth. Interferon-α was produced exclusively
in the form of insoluble inclusion bodies and was solubilized under denaturing conditions, refolded in the presence of arginine
and purified to near homogeneity, utilizing single-step ion-exchange chromatography on Q-Sepharose. The yield of purified
interferon-α was ∼300 mg/l with respect to the original high cell density culture broth (overall yield of ∼7.5% active interferon-α).
The purified recombinant interferon-α was found by different criteria to be predominantly monomeric and possessed a specific
bioactivity of ∼2.5 × 108 IU/mg based on viral cytopathic assay.
Received: 8 October 1999 / Received revision: 8 December 1999 / Accepted: 12 December 1999 相似文献
4.
Rajaguru P Kalaiselvi K Palanivel M Subburam V 《Applied microbiology and biotechnology》2000,54(2):268-273
A sequential anaerobic–aerobic treatment process based on mixed culture of bacteria isolated from textile dye effluent-contaminated
soil was used to degrade sulfonated azo dyes Orange G (OG), Amido black 10B (AB), Direct red 4BS (DR) and Congo red (CR).
Under anaerobic conditions in a fixed-bed column using glucose as co-substrate, the azo dyes were reduced and amines were
released by the bacterial biomass. The amines were completely mineralized in a subsequent aerobic treatment using the same
isolates. The maximum degradation rate observed in the treatment system for OG was 60.9 mg/l per day (16.99 mg/g glucose utilized),
for AB 571.3 mg/l per day (14.46 mg/g glucose utilized), for DR 112.5 mg/l per day (32.02 mg/g glucose utilized) and for CR
134.9 mg/l per day (38.9 mg/g glucose utilized).
Received: 6 August 1999 / Received revision: 20 December 1999 / Accepted: 24 December 1999 相似文献
5.
J. M. Obón J. R. Maiquez M. Cánovas H.-P. Kleber J. L. Iborra 《Applied microbiology and biotechnology》1999,51(6):760-764
The use of a biological procedure for l-carnitine production as an alternative to chemical methods must be accompanied by an efficient and highly productive reaction
system. Continuous l-carnitine production from crotonobetaine was studied in a cell-recycle reactor with Escherichia coli O44 K74 as biocatalyst. This bioreactor, running under the optimum medium composition (25 mM fumarate, 5 g/l peptone), was
able to reach a high cell density (26 g dry weight/l) and therefore to obtain high productivity values (6.2 g l-carnitine l−1 h−1). This process showed its feasibility for industrial l-carnitine production. In addition, resting cells maintained in continuous operation, with crotonobetaine as the only medium
component, kept their biocatalytic capacity for 4 days, but the biotransformation capacity decreased progressively when this
particular method of cultivation was used.
Received: 10 December 1998 / Received revision: 19 February 1999 / Accepted: 20 February 1999 相似文献
6.
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
7.
Related streptococcal and Leuconostoc mesenteroides glucansucrases are enzymes of medical and biotechnological interest. Molecular modelling has suggested that the catalytic
domain contains a circularly permuted version of the (β/α)8 barrel structure found in the amylase superfamily, and site-directed mutagenesis has identified critical amino acids in this
region. In this study, sequential N-terminal truncations of Streptococcus downei GTF-I showed that key amino acids are also present in the first one-third of the core domain. Mutations were introduced at
Trp-344, Glu-349 and His-355, residues that are conserved in all glucansucrases and lie within a region which is a target
for inhibitory antibodies. W344L, E349L and H355V substitutions were assayed for their effect on mutan synthesis and also
on oligosaccharide synthesis with various acceptors. It appeared that Trp-344 and His-355 are involved in the action mechanism
of GTF-I; His-355 may also play a role in a binding subsite necessary for oligosaccharide and glucan elongation.
Received: 14 May 1999 / Received revision: 8 July 1999 / Accepted: 9 July 1999 相似文献
8.
K. Hofvendahl E. W. J. van Niel B. Hahn-Hägerdal 《Applied microbiology and biotechnology》1999,51(5):669-672
Lactococcus lactis ssp. lactis ATCC 19435 is known to produce mixed acids when grown on maltose. A change in fermentation conditions only, elevated temperatures
(up to 37 °C) and reduced pH values (down to 5.0) resulted in a shift towards homolactic product formation. This was accompanied
by decreased growth rate and cell yield. The results are discussed in terms of redox balance and maintenance, and the regulation
of lactate dehydrogenase and pyruvate formate-lyase.
Received: 14 December 1998 / Received revision: 12 January 1999 / Accepted: 22 January 1999 相似文献
9.
A highly thermostable endo-(1,4)-β-mannanase from the marine bacterium Rhodothermus marinus 总被引:2,自引:0,他引:2
Rhodothermus marinus ATCC 43812, a thermophilic bacterium isolated from marine hot springs, possesses hydrolytic activities for depolymerising
substrates such as carob-galactomannan. Screening of expression libraries identified mannanase-positive clones. Subsequently,
the corresponding DNA sequences were determined, eventually identifying a coding sequence specifying a 997 amino acid residue
protein of 113 kDa. Analyses revealed an N-terminal domain of unknown function and a C-terminal mannanase domain of 550 amino
acid residues with homology to known mannanases of glycosidase family 26. Action pattern analysis categorised the R. marinus mannanase as an endo-acting enzyme with a requirement for at least five sugar moieties for effective catalytic activity.
When expressed in Escherichia coli, purified gene product with catalytic activity was mainly found as two protein fragments of 45 kDa and 50 kDa. The full-length
protein of 113 kDa was only detected in crude extracts of R. marinus, while truncated protein-containing fractions of the original source resulted in a major active protein of 60 kDa. Biochemical
analysis of the mannanase revealed a temperature and pH optimum of 85 °C and pH 5.4, respectively. Purified, E. coli-produced protein fragments showed high heat stability, retaining more than 70% and 25% of the initial activity after 1 h
incubation at 70 °C and 90 °C, respectively. In contrast, R. marinus-derived protein retained 87% activity after 1 h at 90 °C. The enzyme hydrolysed carob-galactomannan (locust bean gum) effectively
and to a smaller extent guar gum, but not yeast mannan.
Received: 5 November 1999 / Received revision: 19 January 2000 / Accepted: 23 January 2000 相似文献
10.
Pollutant degradation in biotrickling filters for waste air treatment is generally thought to occur only in the biofilm.
In two experiments with toluene degrading biotrickling filters, we show that suspended microorganisms in the recycle liquid
may substantially contribute to the overall pollutant removal. Two days after reactor start up, the overall toluene elimination
capacity reached a maximum of 125 g m−3 h−1, which was twice that found during prolonged operation. High biodegradation activity in the recycle liquid fully accounted
for this short-term peak of pollutant elimination. During steady-state operation, the toluene degradation in the recycle liquid
was 21% of the overall elimination capacity, although the amount of suspended biomass was only 1% of the amount of immobilized
biomass. The results suggest that biotrickling filter performance may be improved by selecting operating conditions allowing
for the development of an actively growing suspended culture.
Received: 16 June 1999 / Received revision: 17 November 1999 / Accepted: 15 December 1999 相似文献
11.
The thermotolerant fungus, Aspergillus niger NCIM 563, was used for production of extracellular phytase on agricultural residues: wheat bran, mustard cake, cowpea meal,
groundnut cake, coconut cake, cotton cake and black bean flour in solid state fermentation (SSF). Maximum enzyme activity
(108 U g−1 dry mouldy bran, DMB) was obtained with cowpea meal. During the fermentation phytic acid was hydrolysed completely with a
corresponding increase in biomass and phytase activity within 7 days. Phosphate in the form of KH2PO4 (10 mg per 100 g of agriculture residue) increased phytase activity. Among various surfactants added to SSF, Trition X-100
(0.5%) exhibited a 30% increase in phytase activity. The optimum pH and temperature of the crude enzyme were 5.0 and 50°C
respectively. Phytase activity (86%) was retained in buffer of pH 3.5 for 24 h. The enzyme retained 75% of its activity on
incubation at 55°C for 1 h. In the presence of 1 mM K+ and Zn2+, 95% and 55% of the activity were retained. Scanning electron microscopy showed a high density growth of fungal mycelia on
wheat bran particles during SSF. Journal of Industrial Microbiology & Biotechnology (2000) 24, 237–243.
Received 07 June 1999/ Accepted in revised form 18 December 1999 相似文献
12.
We investigate the effect of spatial aggregation in the infection dynamics of nematode parasites in ruminants. We show that
a high degree of spatial aggregation is likely to lead to a dramatically enhanced rate of invasion by drug-resistant strains.
Received: 13 December 1999 / Revised version: 3 April 2000 / Published online: 4 October 2000 相似文献
13.
Gapes JR Swoboda H Haslinger A Nimcevic D 《Applied microbiology and biotechnology》2000,54(1):118-120
In spite of the large-scale industrial use of the acetone-butanol fermentation process earlier this century (until 1983 in
South Africa), very little has been published on the inoculum preparation techniques required for successful fermentation
using these bacteria. In particular, heat-shocking has often been referred to as “useful” but no quantitative data are available.
Data presented in this paper demonstrate and quantify the effect of heat-shocking on batch fermentation yields using one organism
capable of this fermentation.
Received: 27 August 1999 / Received revision: 23 December 1999 / Accepted: 5 January 2000 相似文献
14.
Amino acids have been produced with the aid of microorganisms for nearly 40 years now. The economic importance of these cellular
building blocks is enormous. Demand for them is rising continuously and currently more than 106 tonnes/year are required. Continual efforts to increase production performance are directed towards the microorganisms themselves,
as well as towards technical improvements of the respective processes. A special position within the amino-acid-producing
microorganisms is traditionally occupied by Corynebacterium glutamicum. Molecular research in conjunction with NMR studies of flux has revealed fascinating new properties of this particular organism,
including the existence of a new type of exporter and reverse fluxes within the anaplerosis. The knowledge gained will enable
the further improvement of production strains and furthermore extend fundamental insights into metabolite flux management
within bacteria in general.
Received: 8 December 1998 / Received revision: 1 March 1999 / Accepted: 5 March 1999 相似文献
15.
Inhibition of methane production from whey by heavy metals – protective effect of sulfide 总被引:1,自引:0,他引:1
A whey solution was used as a substrate for methane production in an anaerobic fixed-bed reactor. At a hydraulic retention
time of 10 days, equivalent to a space loading of 3.3 kg (m3 day)−1, 90% of the chemical oxygen demand was converted to biogas. Only a little propionate remained in the effluent. Toxicity tests
with either copper chloride, zinc chloride or nickel chloride were performed on effluent from the reactor. Fifty per cent
inhibition of methanogenesis was observed in the presence of ≥10 mg CuCl2 l−1≥40 mg ZnCl2 l−1 and ≥60 mg NiCl2 l−1, respectively. After exposure to Cu2+, Zn2+ or Ni2+ ions for 12 days, complete recovery of methanogenesis by equimolar sulfide addition was possible upon prolonged incubation.
Recovery failed, however, for copper chloride concentrations ≥40 mg l−1. If the sulfide was added simultaneously with the three heavy metal salts, methanogenesis was only slightly retarded and
the same amount of methane as in non-inhibited controls was reached either 1 day (40 mg ZnCl2 l−1) or 2 days later (10 mg CuCl2 l−1). Up to 60 mg NiCl2 l−1 had no effect if sulfide was present. Sulfide presumably precipitated the heavy metals as metal sulfides and by this means
prevented heavy metal toxicity.
Received: 8 October 1999 / Received revision: 3 January 2000 / Accepted: 4 January 2000 相似文献
16.
P Nanda Devi C Sasikala C V Ramana 《Journal of industrial microbiology & biotechnology》2000,24(3):219-221
Rhodobacter sphaeroides OU5 transformed anthranilate (2 mM) to an indole (0.7 mM) in a light-dependent process. Photobiotransformation was enhanced
by tricarboxylic acid cycle intermediates and the indole formed was identified as 2,3 dihydroxy indole. Journal of Industrial Microbiology & Biotechnology (2000) 24, 219–221.
Received 16 September 1999/ Accepted in revised form 20 December 1999 相似文献
17.
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
18.
A bacterium, JS02, capable of degrading an aromatic medium-chain-length polyhydroxyalkanoate (PHAMCL), poly(3-hydroxy-5-phenylvalerate) (PHPV), was isolated from wastewater-treatment sludge (Ju et al. 1998), and was identified
as a Xanthomonas species. An extracellular PHPV depolymerase was purified from the concentrated culture broth of Xanthomonas sp. JS02 by using a chromatography series on Sephadex G-75, QAE-Sephadex A-50 and hydroxyapatite. The molecular mass of the
purified enzyme was estimated to be 41.7 kDa. The purified enzyme could hydrolyse PHPV and p-nitrophenyl (PNP)-esters of fatty acids, but did not hydrolyse short-chain-length PHAs, though the culture supernatant could
hydrolyse them. The optimum pH range was 8.0–9.0 and the optimum temperature was 60 °C for PNP-octanoate hydrolysis. The K
m values for PNP-hexanoate and PNP-octanoate were 10.9 and 0.88 μM, respectively.
Received: 3 June 1999 / Received revision: 24 August 1999 / Accepted: 24 September 1999 相似文献
19.
Van Laere KM Hartemink R Beldman G Pitson S Dijkema C Schols HA Voragen AG 《Applied microbiology and biotechnology》1999,52(5):681-688
Bifidobacterium adolescentis, a gram-positive saccharolytic bacterium found in the human colon, can, alongside other bacteria, utilise stachyose in vitro
thanks to the production of an α-galactosidase. The enzyme was purified from the cell-free extract of Bi. adolescentis DSM 20083T. It was found to act with retention of configuration (α→α), releasing α-galactose from p-nitrophenyl galactoside. This hydrolysis probably operates with a double-displacement mechanism, and is consistent with the
observed glycosyltransferase activity. As α-galactosides are interesting substrates for bifidobacteria, we focused on the
production of new types of α-galactosides using the transgalactosylation activity of Bi. adolescentisα-galactosides. Starting from melibiose, raffinose and stachyose oligosaccharides could be formed. The transferase activity
was highest at pH 7 and 40 °C. Starting from 300 mM melibiose a maximum yield of 33% oligosaccharides was obtained. The oligosaccharides
formed from melibiose were purified by size-exclusion chromatography and their structure was elucidated by NMR spectroscopy
in combination with enzymatic degradation and sugar linkage analysis. The trisaccharide α-d-Galp-(1 → 6)-α-d-Galp-(1 → 6)-d-Glcp and tetrasaccharide α-d-Galp-(1 → 6)-α-d-Galp-(1 → 6)-α-d-Galp-(1 → 6)-d-Glcp were identified, and this indicates that the transgalactosylation to melibiose occurred selectively at the C-6 hydroxyl group
of the galactosyl residue. The trisaccaride α-d-Galp-(1 → 6)-α-d-Galp-(1 → 6)-d-Glcp formed could be utilised by various intestinal bacteria, including various bifidobacteria, and might be an interesting pre-
and synbiotic substrate.
Received: 15 March 1999 / Received revision: 8 June 1999 / Accepted: 11 June 1999 相似文献
20.
Nitrate reduction by Citrobacter diversus under aerobic environment 总被引:17,自引:0,他引:17
A new aerobic denitrifier, Citrobacter diversus, was isolated from both nitrification and denitrification sludge. To monitor the variation in the concentration of nitrogen
oxides, aerobic denitrification by C. diversus was carried out in a batch reactor. When the nitrate concentration was greater than 180 mg N l−1, the nitrate reduction rate became stable. The effect of the C/N ratio on the denitrification activity was also investigated.
The results showed that the optimum denitrification activity was obtained when the C/N ratio was 4–5. The range of the C/N
ratio was higher than that for traditional anoxic denitrification. The effect of the dissolved oxygen concentration was further
studied; and it was found that the range of dissolved oxygen concentrations, both for specific growth rates and for specific
denitrification rates, was 2–6 mg−1. From these results, it can be concluded that both the concentration of dissolved oxygen and the C/N ratio are key factors
in the aerobic denitrification by C. diversus.
Received: 23 November 1999 / Received revision: 4 February 2000 / Accepted: 13 February 2000 相似文献