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1.
R. Dijkerman H. J. M. Op den Camp C. van der Drift 《Applied microbiology and biotechnology》1996,46(1):85-91
Two species of anaerobic fungi, i.e. Piromyces strain E2 and Neocallimastix patriciarum strain N2, were cultivated in a 10-l batch fermenter with filter- paper cellulose as the carbon source. The accumulation
of fermentation products, production of extracellular protein and (hemi-)cellulolytic enzymes were monitored during growth.
Growth of Piromyces E2 in the fermenter resulted in a shift in the fermentation pattern to more acetate and formate and less ethanol, lactate,
succinate and malate, possibly because of removal of hydrogen. The specific activities of Avicelase, endoglucanase, β-glucosidase
and xylanase were up to threefold higher compared to small batch cultures. Enzyme activities produced per gram of cellulose
were up to four times the values reported for Piromyces E2 grown in a semi-continuous coculture with the methanogen Methanobacterium formicicum. The performance of fermenter enzyme preparations from the anaerobic fungi with respect to hydrolysis of Avicel compared
well to that of preparations of Trichoderma reesei. However, addition of exogenous β-glucosidase was indispensible with the latter preparation for the complete conversion to
glucose.
Received: 14 December 1995/Received revision: 19 March 1996/Accepted: 25 March 1996 相似文献
2.
The effect of some culture variables in the production of β-galactosidase from Escherichia coli in Bacillus subtilis was evaluated. The lacZ gene was expressed in B. subtilis using the regulatory region of the subtilisin gene aprE. The host contained also the hpr2 and degU32 mutations, which are known to overexpress the aprE gene. We found that, when this overproducing B. subtilis strain was grown in mineral medium supplemented with glucose (MMG), β-galactosidase production was partially growth-associated,
as 40%–60% of the maximum enzyme activity was produced before the onset of the stationary phase. In contrast, when a complex
medium was used, β-galactosidase was produced only at low levels during vegetative growth, whereas it accumulated to high
levels during early stationary phase. Compared with the results obtained in complex media, a 20% increase in specific β-galactosidase
activity in MMG supplemented with 11.6 g/l glucose was obtained. On the 1-l fermenter scale, a threefold increase in volumetric
β-galactosidase activity was obtained when the glucose concentration was varied from 11 g/l to 26 g/l. In addition, glucose
feeding during the stationary phase resulted in a twofold increase in volumetric enzyme activity as cellular lysis was prevented.
Finally, we showed that oxygen uptake and carbon dioxide evolution rates can be used for on-line determination of the onset
of stationary phase, glucose depletion and biomass concentration.
Received: 18 April 1996 / Received revision: 27 August 1996 / Accepted: 6 September 1996 相似文献
3.
Differential profiles of soluble proteins during the initiation of morphogenesis in Candida albicans 总被引:1,自引:0,他引:1
Candida albicans is a dimorphic fungus that can grow either as yeast or as mycelia. The mycelial form may be required for tissue penetration
and therefore may have a role in pathogenesis. The protein profiles of the cell-free S100 fraction from budding yeast cells
and germ tube-forming cells (an early stage of the transition between yeast and mycelia) were evaluated using two-dimensional
polyacrylamide gel electrophoresis (2-D PAGE). Yeast growth or germ tube formation was induced in carbon-starved cells at
37° C by either glucose, galactose or N-acetylglucosamine at pH 4.5 or pH 6.7. More than 400 constitutively synthesised polypeptides were identified on 2-D PAGE
by silver staining. A few polypeptides which seem to reflect the release from carbon starvation were detected, but no polypeptides
unique to either morphology were observed. Fractionation of S100 preparations by polyethylenimine or heparin-agarose affinity
chromatography, which have been used to detect DNA-binding proteins, revealed several proteins that were synthesised on the
resumption of cell growth or in response to pH difference. Heparin-agarose also bound novel polypeptides in the size range
130–200 kDa that were preferentially synthesised in germ tube-forming cells. These results suggest that any protein factors
that might exert a regulatory role early in germ tube formation are of low abundance, and that a minor group of soluble proteins
involved in C. albicans morphogenesis may be differentially synthesised.
Received: 11 March 1996 / Accepted: 10 July 1996 相似文献
4.
P. Schmitt C. Vasseur V. Phalip D. Q. Huang C. Diviès H. Prévost 《Applied microbiology and biotechnology》1997,47(6):715-718
The co-metabolism of citrate plus xylose by Leuconostoc mesenteroides subsp. mesenteroides results in a growth stimulation, an increase in d-lactate and acetate production and repression of ethanol production. This correlated well with the levels of key enzymes
involved. A partial repression of alcohol dehydrogenase and a marked stimulation of acetate kinase were observed. High citrate
bioconversion yields in diacetyl plus acetoin were obtained at pH 5.2 in batch (11.5%) or in chemostat (up to 17.4%) culture.
In contrast, no diacetyl or acetoin was detected in citrate plus glucose fermentation.
Received: 6 December 1996 / Received revision: 14 February 1997 / Accepted: 14 February 1997 相似文献
5.
Induction of submerged conidiation of Penicillium oxalicum has been examined using a range of synthetic and complex media and complex media supplemented with by-products of the brewing
industry. Only one method (Morton's method), consisting of growth in a glucose/salts-based medium (C:N ratio 62.5, medium
A) for 24 h and then transference to the same medium without a nitrogen source (medium B), induced conidiation. Levels of
sporulation were significantly (P = 0.05) increased by addition of calcium or poly(ethylene glycol) 6000 to medium B. The optimum age for transference of the
mycelium was 24 h and the optimum pH was 6. Calcium was an induction factor when added to medium A (C:N ratio 62.5) of Morton's
method. It was concluded that nitrogen depletion and calcium addition to a medium with high C:N ratio are the factors inducing
conidiation of P. oxalicum. Maximum levels of conidiation (35 × 106 spores ml−1) were obtained when the nitrogen level in medium A of Morton's method was further reduced (C:N ratio 142.9) and calcium (20 mM)
was added. These results are the essential starting point to investigate liquid fermentation systems for the biocontrol agent
P. oxalicum.
Received: 19 November 1996 / Received revision: 25 March 1997 / Accepted: 27 March 1997 相似文献
6.
Trametes versicolor was shown to produce extracellular laccase during surface cultivation on glucose, wheat straw and beech wood. Growth on both
wheat straw and beech wood led to an increase as high as 3.5-fold in extracellular laccase activity, in comparison with growth
on glucose. The corresponding yields in fungal biomass reached only about 20% of the value obtained on glucose. Manganese
peroxidase activity␣appeared during growth on wheat straw and beech wood. Mycelia grown on glucose, wheat straw and beech
wood also showed intracellular laccase activities, monitored with 2,6-dimethoxyphenol, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic
acid), 4-hydroxy-3,5-dimethoxybenzaldehyde azine (syringaldazine) and 3,4-dihydroxyphenylalanine (l-DOPA). Assaying intracellular laccase with 2,6-dimethoxyphenol, syringaldazine and l-DOPA showed the maximum oxidation rates to be at pH values different from those producing maximum oxidation rates with extracellular
laccase. In each case most of the total laccase activity was recovered from the culture filtrates. Growth on wheat straw and
beech wood led to increased values for both extra- and intracellular laccase activities, based on fungal dry weight, in comparison
with growth on glucose.
Received: 18 July 1996 / Received revision: 19 November 1996 / Accepted: 23 November 1996 相似文献
7.
Streptococcus bovis JB1 utilized glucose preferentially to lactose and grew diauxically, but S. bovis 581AXY2 grew nondiauxically and used glucose preferentially only when the glucose concentration was very high (greater than
5 mM). As little as 0.1 mM glucose completely inhibited the lactose transport of JB1. The lactose transport system of 581AXY2
was at least tenfold less sensitive to glucose, and 1 mM glucose caused only a 50% inhibition of lactose transport. Both strains
had phosphotransferase systems (PTSs) for glucose and lactose. The glucose PTSs were constitutive, but little lactose PTS
activity was detected unless lactose was the energy source for growth. JB1 had approximately threefold more glucose PTS activity
than 581AXY2 (1600 versus 600 nmol glucose (mg protein)−1(min)−1. The glucose PTS of JB1 showed normal Michaelis Menten kinetics, and the affinity constant (K
s
) was 0.12 mM. The glucose PTS of 581AXY2 was atypical, and the plot of velocity versus velocity/substrate was biphasic. The
low capacity system had a Ks of 0.20 mM, but the Ks of the high capacity system was greater than 6 mM. On the basis of these results, diauxic growth is dependent on the affinity
of glucose enzyme II and the velocity of glucose transport.
Received: 22 January 1996 / Accepted: 18 March 1996 相似文献
8.
H. De Wever S. De Cort I. Noots H. Verachtert 《Applied microbiology and biotechnology》1997,47(4):458-461
2-Hydroxybenzothiazole (OBT) is present in wastewaters from the industrial production of the rubber vulcanization accelerator
2-mercaptobenzothiazole (MBT). We have achieved the first isolation of axenic bacterial cultures capable of the degradation
of OBT and growth on this substrate as the sole source of carbon, nitrogen and energy. All isolates had similar characteristics
corresponding to one particular isolate, which was studied in more detail and identified as Rhodococcus rhodochrous. The strains were also capable of degrading benzothiazole (BT) but not MBT or benzothiazole-2-sulphonate (BTSO3). OBT was degraded at a concentration of up to 600 mg · l−1. BT was toxic above 300 mg · l−1. MBT inhibited OBT degradation. Growth on OBT was not significantly different at pH values of between 6.3 and 7.9 or salt
concentrations between 1 % and 3 %. In shake flasks the cells clumped together, which resulted in a lower rate of oxygen transfer
and slower degradation as compared to cells grown on OBT in a stirred reactor.
Received: 22 August 1996 / Received revision: 29 November 1996 / Accepted: 29 November 1996 相似文献
9.
The thermophilic fungus Thermomyces lanuginosus, which is able to use dextran as primary carbon source for growth, excreted during the early phases of growth an enzyme activity
capable of degrading dextran. The activity peaked at 22 h and decreased rapidly after the culture entered the stationary phase,
probably caused by protease activity. Results from growth on a number of different carbon sources showed that polymer carbohydrates
yielded the highest dextranase activities. On the basis of the substrate specificity and the release of glucose in the α-anomeric
form from the hydrolysis of maltose, it is proposed that the enzyme responsible for the necessary degradation of dextran to
smaller saccharides is an α-glucosidase.
Received: 30 November 1995 / Accepted: 14 February 1996 相似文献
10.
G. J. Grobben M. R. Smith J. Sikkema J. A. M. de Bont 《Applied microbiology and biotechnology》1996,46(3):279-284
The effect of fructose and glucose on the growth, production of exopolysaccharides and the activities of enzymes involved
in the synthesis of sugar nucleotides in Lactobacillus delbrueckii subsp. bulgaricus grown in continuous culture was investigated. When grown on fructose, the strain produced 25 mg l-1 exopolysaccharide composed of glucose and galactose in the ratio 1:2.4. When the carbohydrate source was switched to a mixture
of fructose and glucose, the exopolysaccharide production increased to 80 mg l-1, while the sugar composition of the exopolysaccharide changed to glucose, galactose and rhamnose in a ratio of 1:7.0:0.8.
A switch to glucose as the sole carbohydrate source had no further effect. Analysis of the enzymes involved in the synthesis
of sugar nucleotides indicates that in cell-free extracts of glucose-grown cells the activity of UDP-glucose pyrophosphorylase
was higher than that in cell-free extracts of fructose-grown cells. The activities of dTDP-glucose pyrophosphorylase and the
rhamnose synthetic enzyme system were very low in glucose-grown cultures but could not be detected in fructose-grown cultures.
Cells grown on a mixture of fructose and glucose showed similar enzyme activities as cells grown on glucose. Analysis of the
intracellular level of sugar nucleotides in glucose-grown cultures of L. delbrueckii subsp. bulgaricus showed the presence of UDP-glucose and UDP-galactose in a ratio of 3.3:1, respectively, a similar ratio and slightly lower
concentrations were found in fructose-grown cultures. The lower production of exopolysaccharides in cultures grown on fructose
may be caused by the more complex pathway involved in the synthesis of sugar nucleotides. The absence of activities of enzymes
leading to the synthesis of rhamnose nucleotides in fructose-grown cultures appeared to result in the absence of rhamnose
monomer in the exopolysaccharides produced on fructose.
Received: 1 February 1996/Received revision: 31 May 1996/Accepted: 2 June 1996 相似文献
11.
Shankar SK Kumar SK Mulimani VH 《Journal of industrial microbiology & biotechnology》2011,38(9):1399-1405
Thermostable α-galactosidase from Aspergillus terreus
GR was insolubilized using concanavalin A obtained from jack bean extract and in order to maintain the integrity of complex
in the presence of its substrate or products, this complex was crosslinked with glutaraldehyde. Soluble α-galactosidase entrapped
in calcium alginate retained 82% of enzyme activity whereas, Con A-α-galactosidase complex entrapped in calcium alginate and
crosslinked Con A-α-galactosidase complex entrapped calcium alginate retained 74 and 61% activity, respectively. A fluidized
bed reactor was constructed for continuous hydrolysis of galactooligosaccharides in soymilk using crosslinked Con A-α-galactosidase
complex entrapped calcium alginate. Optimum conditions such as pH (5.0) and temperature (65°C) were the same for all immobilized
enzyme preparations and soluble enzyme. Crosslinked Con A-α-galactosidase entrapped complex exhibited enhanced thermostability
and showed 62% of activity (38%) after 360 min at 65°C. Entrapped crosslinked Con A-α-galactosidase complex preparation was
superior in the continuous hydrolysis of oligosaccharides in soymilk by batch processes compared to the other entrapped preparations.
The entrapped crosslinked concanavalin A-α-galactosidase complex retained 95% activity after eight cycles of use. 相似文献
12.
Ryszard Russa Maud Bruneteau Alexander S. Shashkov Teresa Urbanik-Sypniewska Hubert Mayer 《Archives of microbiology》1996,165(1):26-33
Lipopolysaccharides from the Rhizobium meliloti wild-type strain 102F51, which is effective in symbiosis with alfalfa, and from the nonnodulating mutant WL113, defective
in root hair adhesion, derived thereof, were isolated and comparatively analyzed. Both preparations were composed of galactose,
glucose, glucuronic acid, galacturonic acid, glucosamine, 3-deoxyheptulosaric acid, and 2-keto-3-deoxyoctonic acid as the
major sugar constitutents. After a modified methylation analysis (consisting of the following consecutive steps: methylation,
carboxyl reduction, remethylation, mild acid hydrolysis, reduction, and trideuterio-methylation), all of the 3-deoxyheptulosaric
and some of the 2-keto-3-deoxyoctonic acid residues were converted into their corresponding 3-deoxyalditol derivatives, which
carried trideuteriomethyl groups at positions C-2, C-4, and C-6. Another part of the permethylated 3-deoxyoctitol was also
found as 2,5,6- and 2,6,8-tri-O-trideuteriomethyl derivatives. NMR data obtained with the separated oligosaccharides and the results of methylation analysis
indicated that the majority of 2-keto-3-deoxyoctonate was present in the fraction of permethylated disaccharide alditols,
namely as 6-O-CD3-aGlc(1→5)3-deoxyoctitol, 6-O-CD3-βGlcNMeAcyl(1→4)3-deoxyoctitol, and as the permethylated trisaccharide alditol, αGalA(1→3)-[6-O-CD3]-β-Glc(1→5)-[4-O-CD3]-3-deoxyoctitol. The presence of trideuteriomethyl groups at C-4 of both 3-deoxyalditols and at C-6 of the glucosaminyl or
glucosyl residues indicated the linkage points of the released acid-labile ketosidic substituents, such as 3-deoxyheptulosarate
and 2-keto-3-deoxyoctonate, in these oligosaccharides. The main differences between the preparations from the wild-type 102F51
and its mutant strain WL 113 were found in the higher content (in strain 102F51) of the following oligosaccharides: α-glucuronosyl(1→4)2-keto-3-deoxyoctonate
and α-galacturonosyl-(1→3)α-glucosyl-(1→5)2-keto-3-deoxyoctonate and in the decreased content of β-glucosaminyl(1→4)2-keto-3-deoxy-octonate.
Received: 21 July 1995 / Accepted: 25 October 1995 相似文献
13.
H. P. Molitoris S. T. Moss G. J. M. de Koning D. Jendrossek 《Applied microbiology and biotechnology》1996,46(5-6):570-579
Bacterial degradation of sheets of selected polyhydroxyalkanoates by Comamonas sp., Pseudomonas lemoignei and Pseudomonas fluorescens GK13 is reported. Five natural polyhydroxyalkanoates were used, namely poly(3-hydroxybutyrate), poly(3-hydroxyvalerate),
a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate, a copolymer of mainly 3-hydroxyoctanoate and minor amounts of 3-hydroxyhexanoate,
and two rubber-like copolymers of saturated and unsaturated hydroxyalkanoic acids that had been modified by electron-beam-induced
cross-linking. Each of these polymers was degraded by at least one bacterial strain, the rate of hydrolysis being dependent
on the surface area of the polymer exposed to attack. Scanning electron microscopy of partially degraded samples showed that
hydrolysis started at the surface and at physical lesions in the polymer and proceeded to the inner part of the material.
No evidence for areas of non-degradable polymer was found for any of the polymers analysed, even if the polymer contained
chemical cross-links.
Received: 24 July 1996 / Accepted: 29 August 1996 相似文献
14.
Xanthomonas campestris pv. campestris, the causal agent of black-rot disease of cruciferous plants, and an important industrial microbe, was able to express the
Escherichia coliβ-glucuronidase reporter gene (uidA) when fused to the E. coli lactose operon promoter on a wide-host-range plasmid vector. The gene fusion is expressed constitutively at high levels in
both complex and defined media using a wide range of carbon sources, and is not repressible by glucose or inducible by the
gratuitous lac inducer isopropyl β-d-thiogalactoside. An X. campestris campestris strain with a lesion in the clp (catabolite-repressor-like protein) locus, and containing the plac/uidA fusion, was tested for β-glucuronidase activity. We found that the expression of the plac/uidA fusion gene is dependent on the presence of catabolite-repressor-like protein, with an approximately 75% reduction of expression
in the clp -deficient mutant.
Received: 1 April 1996 / Received revision: 21 June 1996 / Accepted: 15 July 1996 相似文献
15.
Zhang H Moon YH Watson BJ Suvorov M Santos E Sinnott CA Hutcheson SW 《Journal of industrial microbiology & biotechnology》2011,38(8):1117-1125
Saccharophagus degradans 2-40 is a marine gamma proteobacterium that can produce polyhydroxyalkanoates from lignocellulosic biomass using a complex
cellulolytic system. This bacterium has been annotated to express three surface-associated β-glucosidases (Bgl3C, Ced3A, and
Ced3B), two cytoplasmic β-glucosidases (Bgl1A and Bgl1B), and unusual for an aerobic bacterium, two cytoplasmic cellobiose/cellodextrin
phosphorylases (Cep94A and Cep94B). Expression of the genes for each of the above enzymes was induced when cells were transferred
into a medium containing Avicel as the major carbon source except for Bgl1B. Both hydrolytic and phosphorolytic degradation
of cellobiose by crude cell lysates obtained from cellulose-grown cells were demonstrated and all of these activities were
cell-associated. With the exception of Cep94B, each purified enzyme exhibited their annotated activity upon cloning and expression
in E. coli. The five β-glucosidases hydrolyzed a variety of glucose derivatives containing β-1, (2, 4, or 6) linkages but did not act
on any α-linked glucose derivatives. All but one β-glucosidases exhibited transglycosylation activity consistent with the
formation of an enzyme-substrate intermediate. The biochemistry and expression of these cellobiases indicate that external
hydrolysis by surface-associated β-glucosidases coupled with internal hydrolysis and phosphorolysis are all involved in the
metabolism of cellobiose by this bacterium. 相似文献
16.
M T Smith D R Cameron S J B Duff 《Journal of industrial microbiology & biotechnology》1997,18(1):18-21
Ethanol production from spent sulphite pulping liquor (SSL) was compared for four different yeasts. A second strain of S. cerevisiae as well as a 2-deoxyglucose-resistant strain formed through protoplast fusions between S. uvarum and S. diastaticus produced up to 27% more ethanol from SSL fortified with hydrolysis sugars than was produced by S. cerevisiae. The incremental improvement in ethanol yield appeared to vary with the degree of fortification, ranging from 5.8% for unfortified
SSL, to 27% for the highest level of fortification tested. Decreasing fermentation rates were observed for SSL fortified
with glucose, mannose and galactose, respectively. Sugar uptake rates in SSL fortified with glucose, galactose and mannose
were 6.8, 2.8 and 2.0 g L−1 h−1, respectively. However, when these sugars were fermented along with a glucose cosubstrate, the rate at which the combined
glucose/mannose medium was fermented was nearly identical to that of the glucose control.
Received 18 April 1996/ Accepted in revised form 27 August 1996 相似文献
17.
Cristina Solari Isabella Panfoli A. Morelli Denise Cassandrini Piersandro Cocconcelli Lorenzo Morelli 《Archives of microbiology》1997,168(3):205-209
Lactobacillus helveticus ATCC 15009 (wild-type) membrane preparations hydrolyzed Mg2+-ATP as a function of K+ concentration (2–200 mM). Mg2+-ATP hydrolysis by L. helveticus membranes was strongly inhibited in the absence of exogenous K+, while it amounted to 6 nmol ATP hydrolyzed min–1 (mg membrane protein)–1 at 50 mM KCl (saturating conditions) and pH 7.2. The K+-dependent ATPase of L. helveticus displayed a relatively high affinity for potassium ions (K
m = 800 μM) and was not affected by pretreatment of membranes with N,N’-dicyclohexylcarbodiimide. Membrane preparations were subjected to hypotonic shock to obtain a maximum yield of open profiles.
The formation of a maximum level of enzyme-phosphate complex with a molecular mass of approximately 82 kDa was induced upon
treatment of L. helveticus membrane preparations with low concentrations of [γ-32P]ATP in the presence of K+ and La3+ ions and was visualized by acidic SDS-PAGE. It was concluded that L. helveticus membranes contain an inwardly directed K+ pump whose presence is discussed in terms of its putative role in cytoplasmic pH regulation.
Received: 16 December 1996 / Accepted: 14 May 1997 相似文献
18.
Carbon and nitrogen regulation of UBI4, the stress-inducible polyubiquitin gene of Saccharomyces cerevisiae, was investigated using a UBI4 promoter-LacZ fusion gene (UBI4-LacZ). Expression of this gene in cells grown on different
media indicated that the UBI4 promoter is more active during growth on respiratory than on fermentable carbon sources but
is not subject to appreciable control by nitrogen catabolite repression. UBI4-LacZ expression was virtually identical in cells
having constitutively high (ras2, sra1-13) or constitutively low (ras2) levels of cyclic AMP-dependent protein kinase activity,
indicating that this kinase does not exert a major influence on UBI4 expression. Catabolite derepression control of the UBI4
promoter was confirmed by measurements of UBI4-LacZ expression in hap mutant and wild-type strains before and after transfer
from glucose to lactate. Mutagenesis of the perfect consensus for HAP2/3/4 complex binding at position −542 resulted in considerable
reduction of UBI4 promoter derepression with respiratory adaptation in HAP wild-type cells and abolished the reduced UBI4-LacZ
derepression normally seen when aerobic cultures of the hap1 mutant are transferred from glucose to lactate. This HAP2/3/4
binding site is therefore a major element contributing to catabolite derepression of the UBI4 promoter, although data obtained
with hap1 mutant cells indicated that HAP1 also contributes to this derepression. The HAP2/3/4 and HAP1 systems are normally
found to activate genes for mitochondrial (respiratory) functions. Their involvement in mediating higher activity of the UBI4
promoter during respiratory growth may reflect the contribution of UBI4 expression to tolerance of oxidative stress.
Received: 3 June 1996 / Accepted: 20 August 1996 相似文献
19.
Eight strains of the genus Aureobasidium obtained from culture collections were tested for their capability to produce poly(β-L-malic acid) (PMA). Four of the tested strains showed positive results. The most productive strain, A. pullulans CBS 591.75, was used to study the production of PMA in stirred-tank reactors. It was found that PMA was mainly produced in
the late exponential phase, and the production related positively to glucose consumption. At the beginning of the fermentation
the pH increased from 4.0 to about 7.0; subsequently the pH decreased and remained stable at around 3.0–3.5 for several days.
Temperatures higher than 25°C were detrimental to PMA production and cell growth. PMA production and cell growth at 20°C and 25°C exhibited no significant differences. PMA production and cell growth were studied under pH-controlled fermentation (at pH
2.0, 4.0, 5.5). The highest PMA production occurred at pH 4.0. PMA production was reduced at pH 2.0 although quite reasonable
cell growth occurred at this pH value. Under optimized conditions 9.8 g PMA/l was produced during 9 days of fermentation in
the stirred-tank reactors with an overall yield of 0.11 g PMA/g glucose. A procedure for the isolation of PMA and its separation
from the other components of the fermentation broth was developed. The isolated PMA was characterized by 1H and 13C-NMR spectroscopy as well as by infrared absorption spectroscopy. Gel-permeation chromatography revealed a relative molecular
mass of approximately 3000–5000 by comparison with polyethylene glycol standards.
Received: 13 February 1996/Received revision: 25 April 1996/Accepted: 1 May 1996 相似文献
20.
L. Escalante I. Ramos I. Imriskova E. Langley S. Sanchez 《Applied microbiology and biotechnology》1999,52(4):572-578
The effect of glucose on growth and anthracycline production by Streptomyces peucetius var. caesius was examined in a chemically defined medium. Glucose concentrations above 100 mM inhibited anthracycline synthesis in the
original strain without causing significant change in growth and final pH values. This effect was observed when the carbohydrate
was added initially or after 24 h fermentation, but not when added during the stationary growth phase. When the microorganism
was pregrown in 100 mM glucose and then transferred to a resting cell system with 444 mM glucose, no significant differences
in antibiotic production were observed compared to the control without glucose. The negative effect of glucose on antibiotic
synthesis was not observed in a mutant (2-dogR–21) resistant to growth inhibition by 2-deoxyglucose. Glucose consumption by this mutant was approximately 30% of that utilized
by the original strain. Compared to the original strain, the mutant 2-dogR–21 exhibited a reduction of 50% in glucose transport and an 85% decrease in glucose kinase activity. The experimental evidence
obtained suggests that glucose represses anthracycline formation in a transitory manner and that this effect is related to
glucose transport and phosphorylation.
Received: 15 January 1999 / Received revision: 7 April 1999 / Accepted: 1 May 1999 相似文献