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1.
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
2.
Influence of complex nutrients, temperature and pH on bacteriocin production by Lactobacillus sakei CCUG 42687 总被引:1,自引:0,他引:1
Aasen IM Møretrø T Katla T Axelsson L Storrø I 《Applied microbiology and biotechnology》2000,53(2):159-166
The effects of process conditions and growth kinetics on the production of the bacteriocin sakacin P by Lactobacillus sakei CCUG 42687 have been studied in pH-controlled fermentations. The fermentations could be divided into phases based on the
growth kinetics, phase one being a short period of exponential growth, and three subsequent ones being phases of with decreasing
specific growth rate. Sakacin P production was maximal at 20 °C. At higher temperatures (25–30 °C) the production ceased at
lower cell masses, when less glucose was consumed, resulting in much lower sakacin P concentrations. With similar media and
pH, the maximum sakacin P concentration at 20 °C was seven times higher than that at 30 °C. The growth rate increased with
increasing concentrations of yeast extract, and the maximum concentration and specific production rate of sakacin P increased
concomitantly. Increasing tryptone concentrations also had a positive influence upon sakacin P production, though the effect
was significantly lower than that of yeast extract. The maximum sakacin P concentration obtained in this study was 20.5 mg
l−1. On the basis of the growth and production kinetics, possible metabolic regulation of bacteriocin synthesis is discussed,
e.g. the effects of availability of essential amino acids, other nutrients, and energy.
Received: 7 June 1999 / Received revision: 15 September 1999 / Accepted: 17 September 1999 相似文献
3.
Sanjay Chauhan Anuradha Nichkawade M.R.S. Iyengar Bharat B. Chattoo 《Current microbiology》1998,37(3):186-190
Aerobic cultures of an actinomycete were found to produce penicillin V acylase (PVA) (PA, EC-3.5.1.11) extracellularly. The
presence of L-2-3 diamino-propionic acid in cell wall and formation of sclerotia on culture media led to its identification
as Chainia, a sclerotial Streptomyces. Partially purified acylase was adsorbed on kieselguhr and entrapped in polyacrylamide gel. The immobilized preparation proved
effective with respect to retention of enzyme and enzyme activity even after 15 successful cycles. The pH optimum for crude
enzyme was in the range of pH 7.5–8.0, and for the (NH4)2 SO4 fraction it was pH 8.5. The immobilized enzyme showed maximal activity at pH 9.5. The optimum temperature for acylase activity
was at 55°C. The crude enzyme, ammonium sulfate fraction, and immobilized enzyme showed K
m
value for penicillin V of 6.13 mM, 14.3 mM, and 17.1 mM, respectively.
Received: 11 December 1997 / Accepted: 9 April 1998 相似文献
4.
C. Suresh A. K. Dubey S. Srikanta S. Umesh Kumar N. G. Karanth 《Applied microbiology and biotechnology》1999,51(5):673-675
A UV-induced mutant strain of Aspergillus niger (CFTRI-1105-U9) overproduced a starch-hydrolysing enzyme with properties characteristically different from the known amylases
of the fungus. The purified enzyme of 4.0 pI had an apparent molecular mass of 125 kDa and it dextrinised starch and then
saccharified the dextrins. Patterns of the enzyme activity on starch, resulting in glucose at 60 °C and glucose, maltose and
maltodextrins at 70 °C as primary products, suggested significant applications for the enzyme in starch-processing industries.
Received: 29 October 1998 / Received revision: 11 January 1999 / Accepted: 19 January 1999 相似文献
5.
A Saccharomyces-cerevisiae-based simultaneous saccharification and fermentation (SSF) of lignocellulosic biomass is limited to an operating temperature
of about 37 °C, and even a small increase in temperature can have a deleterious effect. This points to a need for a more thermotolerant
yeast. To this end, S. cerevisiae D5A and a thermotolerant yeast, Candida acidothermophilum, were tested at 37 °C, 40 °C, and 42 °C using dilute-acid-pretreated poplar as substrate. At 40 °C, C. acidothermophilum produced 80% of the theoretical ethanol yield, which was higher than the yield from S.cerevisiae D5A at either 37 °C or 40 °C. At 42 °C, C. acidothermophilum showed a slight drop in performance. On the basis of preliminary estimates, SSF with C. acidothermophilum at 40 °C can reduce cellulase costs by about 16%. Proportionately greater savings can be realized at higher temperatures
if such a high-temperature SSF is feasible. This demonstrates the advantage of using thermophilic or thermotolerant yeasts.
Received: 20 February 1997 / Received revision: 24 June 1997 / Accepted: 4 July 1997 相似文献
6.
A Gram-negative bacterium producing a heat-stable nitrilase highly active on aliphatic dinitriles 总被引:8,自引:0,他引:8
J. E. Gavagan R. DiCosimo A. Eisenberg S. K. Fager P. W. Folsom E. C. Hann K. J. Schneider R. D. Fallon 《Applied microbiology and biotechnology》1999,52(5):654-659
A Gram-negative bacterial strain, identified as Acidovorax facilis strain 72W, has been isolated from soil by enrichment using 2-ethylsuccinonitrile as the sole nitrogen source. This strain
grows on a variety of aliphatic mono- and dinitriles. Experiments using various heating regimes indicate that nitrile hydratase,
amidase and nitrilase activities are present. The nitrilase is efficient at hydrolyzing aliphatic dinitriles to cyanoacid
intermediates. It has a strong bias for C3–C6 dinitriles over mononitriles of the same chain length. Whole, resting cell hydrolysis of 2-methylglutaronitrile results in
4-cyanopentanoic acid and 2-methylglutaric acid as the major products. Heating, at least 20 min at 50 °C, eliminates nitrile
hydratase and amidase activities, resulting in greater than 97% selectivity to 4-cyanopentanoic acid. The nitrilase activity
has good heat stability, showing a half-life of 22.7 h at 50 °C and a temperature optimum of at least 65 °C for activity.
The strain has been deposited as ATCC 55746.
Received: 26 January 1999 / Received revision: 10 June 1999 / Accepted: 27 June 1999 相似文献
7.
M. A. Ferrero G. R. Castro C. M. Abate M. D. Baigorí F. Siñeriz 《Applied microbiology and biotechnology》1996,45(3):327-332
Bacillus licheniformis MIR 29 has been isolated and produces extracellular proteases. It is able to grow at temperatures up to 60 °C and at pH values
up to 9.0. Casein was the best carbon source for production of a thermostable protease activity which, in some conditions,
is 90% extracellular. The synthesis of alkaline protease is not constitutive; different levels of production were found with
different carbon and nitrogen sources. Casein was thought to be an inducer of enzyme synthesis. The optimal pH and temperature
of the enzyme activity were 12 °C and 60 °C, respectively. The enzyme was stable up to 60 °C in the absence of stabilizers.
The protease activity was inhibited with phenylmethylsulphonyl fluoride, indicating a serine-protease activity. The proteolytic
activity was lowered by molecules present in the culture supernatant, which include amino acids and peptides, indicating end-product
inhibition. Electrophoresis assay on denaturating gels showed two bands with alkaline protease activity, in the 25 to 40-kDa
molecular mass range.
Received: 7 June 1995/Received revision: 14 September 1995/Accepted: 20 September 1995 相似文献
8.
M. Graf A. Brunella M. Kittelmann K. Laumen O. Ghisalba 《Applied microbiology and biotechnology》1997,47(6):650-657
A new amidohydrolase deacetylating several N-acetyl-1-phenylethylamine derivatives (R)-specifically was found in Arthrobacter aurescens AcR5b. The strain was isolated from a wet haystack by enrichment culture with (R)-N-acetyl-1-phenylethylamine as the sole carbon source. (R) and (S )-N-acetyl-1-phenylethylamine do not serve as inducers for acylase formation. By improving the growth conditions the enzyme production
was increased 47-fold. The amidohydrolase was purified to homogeneity leading to a 5.2-fold increase of the specific activity
with a recovery of 67%. A molecular mass of 220 kDa was estimated by gel filtration. Sodium dodecyl sulfate/polyacrylamide
gel electrophorosis shows two subunits with molecular masses of 16 kDa and 89 kDa. The optimum pH and temperature were pH 8
and 50 °C, respectively. The enzyme was stable in the range of pH 7–9 and at temperatures up to 30 °C. The enzyme activity
was inhibited by Cu2+, Co2+, Ni2+, and Zn2+, and this inhibition was reversed by EDTA.M
Received: 20 September 1996 / Received version: 23 December 1996 / Accepted: 30 December 1996 相似文献
9.
Keratinase of Doratomyces microsporus 总被引:10,自引:0,他引:10
The fungus Doratomyces microsporus produced an extracellular keratinase during submerged aerobic cultivation in a medium containing a protein inducer for enzyme
synthesis. The keratinase was purified to homogeneity using hydrophobic interaction chromatography followed by gel chromatography.
The molecular weight was estimated to be 33 kDa (from SDS-PAGE analysis) or 30 kDa (by gel chromatography), suggesting a monomeric
structure. The isoelectric point of the enzyme was determined to be around 9. The optimal pH and temperature for keratinolytic
activity were pH 8–9 and 50 °C, respectively. The serine protease inhibitor PMSF totally inhibited the keratinase. The enzyme
was not glycosylated. It was capable of hydrolysing different keratinous materials as well as some non-keratinous proteins.
Hydrolysis of some synthetic substrates, specific for known proteinases, suggested that the keratinase of D. microsporus is close to proteinase K.
Received: 9 July 1999 / Received revision: 13 September 1999 / Accepted: 17 September 1999 相似文献
10.
P. Wahl P. Walser-Volken K. Laumen M. Kittelmann O. Ghisalba 《Applied microbiology and biotechnology》1999,53(1):12-18
Rhodococcus globerulus K1/1 was found to express an inducible (S)-specific N-acetyl-2-amino-1-phenyl-4-pentene amidohydrolase. Optimal bacterial growth and amidohydrolase expression were both observed
at about pH 6.5. Purification of the enzyme to a single band in a Coomassie blue-stained SDS-PAGE gel was achieved by nucleic
acid and ammonium sulfate precipitation of Rhodococcus globerulus K1/1 crude extract and column chromatography on TSK Butyl-650(S) Fractogel and Superose 12HR. The amidohydrolase was purified to a homogeneity leading to a tenfold increase of the specific
activity with a recovery rate of 65%. At pH 7.0 and 23 °C the enzyme showed no loss of activity after 30 days incubation.
The amidohydrolase was stable up to 55 °C. The enzyme was inhibited strongly only by 10 mM Zn2+ among the tested metal cations and was inhibited 100% by 0.01 mM phenylmethanesulfonyl fluoride. The molecular weight of
the native enzyme was estimated to be 92 kDa by gel filtration and 55 kDa by SDS-PAGE, suggesting a homodimeric structure.
Received: 8 February 1999 / Received revision: 3 May 1999 / Accepted: 7 May 1999 相似文献
11.
A heat shock following electroporation induces highly efficient transformation of Corynebacterium glutamicum with xenogeneic plasmid DNA 总被引:10,自引:0,他引:10
An improved method for the electrotransformation of wild-type Corynebacterium glutamicum (ATCC 13032) is described. The two crucial alterations to previously developed methods are: cultivation of cells used for
electrotransformation at 18 °C instead of 30 °C, and application of a heat shock immediately following electrotransformation.
Cells cultivated at sub optimal temperature have a 100-fold improved transformation efficiency (108 cfu μg−1) for syngeneic DNA (DNA isolated from the same species). A heat shock applied to these cells following electroporation improved
the transformation efficiency for xenogeneic DNA (DNA isolated from a different species). In combination, low cultivation
temperature and heat shock act synergistically and increased the transformation efficiency by four orders of magnitude to
2.5 × 106 cfu μg−1 xenogeneic DNA. The method was used to generate gene disruptions in C. glutamicum.
Received: 26 March 1999 / Received revision: 9 June 1999 / Accepted: 11 June 1999 相似文献
12.
K. Hayakawa Y. Ueno S. Kawamura T. Kato R. Hayashi 《Applied microbiology and biotechnology》1998,50(4):415-418
In order to test the possibility of utilizing high pressure in bioscience and biotechnology, a simple method for high-pressure
generation and its use for microbial inactivation have been studied. When a pressure vessel was filled with water, sealed
tightly and cooled to sub-zero temperatures, high pressure was generated in the vessel. The pressure generation was 60 MPa
at −5 °C, 103 MPa at −10 °C, and 140 MPa at −15 °C, −20 °C, and −22 °C. The high pressure generated inactivated microorganisms
effectively: yeasts (Saccharomyces cerevisiae and Zygosaccharomyces rouxii), bacteria (Lactobacillus brevis and Eschericia coli), and fungi (Aspergillus niger and Aspergillus oryzae) were completely inactivated when stored in sealed vessels −20 °C for 24 h. However, Staphylococcus aureus was only partly inactivated under the same conditions. This method opens up a new application of high pressure for storing,
transporting, and sterilizing of foods and biological materials.
Received: 28 July 1997 / Received last revision: 12 June 1998 / Accepted: 19 June 1998 相似文献
13.
Purification and properties of a novel raw starch degrading cyclomaltodextrin glucanotransferase from Bacillus firmus 总被引:3,自引:0,他引:3
B. N. Gawande A. Goel A. Y. Patkar S. N. Nene 《Applied microbiology and biotechnology》1999,51(4):504-509
A novel raw starch degrading cyclomaltodextrin glucanotransferase (CGTase; E.C. 2.4.1.19), produced by Bacillus firmus, was purified to homogeneity by ultrafiltration, affinity and gel filtration chromatography. The molecular weight of the
pure protein was estimated to be 78 000 and 82 000 Da, by SDS-PAGE and gel filtration, respectively. The pure enzyme had a
pH optimum in the range 5.5–8.5. It was stable over the pH range 7–11 at 10 °C, and at pH 7.0 at 60 °C. The optimum temperature
for enzyme activity was 65 °C. In the absence of substrate, the enzyme rapidly lost its activity above 30 °C. K
m and k
cat for the pure enzyme were 1.21 mg/ml and 145.17 μM/mg per minute respectively, with soluble starch as the substrate. For cyclodextrin
production, tapioca starch was the best substrate used when gelatinized, while wheat starch was the best substrate used when
raw. This CGTase could degrade raw wheat starch very efficiently; up to 50% conversion to cyclodextrins was obtained from
150 g/l starch without using any additives. The enzyme produced α-, β- and γ-cyclodextrins in the ratio of 0.2:9.2:0.6 and
0.2:8.6:1.2 from gelatinized tapioca starch and raw wheat starch with 150 g/l concentration respectively, after 18 h incubation.
Received: 25 September 1998 / Received revision: 15 December 1998 / Accepted: 21 December 1998 相似文献
14.
R Rech C F Cassini A Secchi M A Z Ayub 《Journal of industrial microbiology & biotechnology》1999,23(2):91-96
We studied the utilization of protein-hydrolyzed sweet cheese whey as a medium for the production of β-galactosidase by the
yeasts Kluyveromyces marxianus CBS 712 and CBS 6556. The conditions for growth were determined in shake cultures. The best growth occurred at pH 5.5 and
37°C. Strain CBS 6556 grew in cheese whey in natura, while strain CBS 712 needed cheese whey supplemented with yeast extract. Each yeast was grown in a bioreactor under these
conditions. The strains produced equivalent amounts of β-galactosidase. To optimize the process, strain CBS 6556 was grown
in concentrated cheese whey, resulting in a higher β-galactosidase production. The β-galactosidase produced by strain CBS
6556 produced maximum activity at 37°C, and had low stability at room temperature (30°C) as well as at a storage temperature
of 4°C. At −4°C and −18°C, the enzyme maintained its activity for over 9 weeks.
Received 20 January 1999/ Accepted in revised form 30 April 1999 相似文献
15.
Towards a reduction in excess sludge production in activated sludge processes: biomass physicochemical treatment and biodegradation 总被引:15,自引:0,他引:15
M. Rocher G. Goma A. Pilas Begue L. Louvel J. L. Rols 《Applied microbiology and biotechnology》1999,51(6):883-890
To decrease activated sludge production, microbial cell lysis can be amplified to enhance cryptic growth (biomass growth
on lysates). Cell breakage techniques (thermal, alkaline, acid) were studied to generate Alcaligenes eutrophus and sludge lysates and to evaluate their biodegradability. Gentle treatment conditions produced the best results. Complete
cell deactivation was obtained for temperatures higher than 55 °C. The release kinetics were similar for temperatures varying
from 60 °C to 100 °C. A 20-min incubation was suitable for reaching 80% of the maximum releasable carbon. In thermal-chemical
hydrolysis, NaOH was the most efficient for inducing cell lysis. Carbon release was a two-step process. First an immediate
release occurred, which was of the same order of magnitude for A. eutrophus and sludge [100–200 mg dissolved organic C (DOC) g total suspended solids (TSS)−1], followed by a post-treatment release. The second step was virtually equivalent to the first for sludge, and weaker for
A. eutrophus (<50 mg DOC g TSS−1). The biodegradability of the soluble fraction, both the immediate and the post-treatment carbon release, was investigated.
The optimal degradation yield, obtained with sludge cells, reached 55% after 48 h of incubation and 80% after 350 h. The most
consistent lysis and biodegradation results occurred at pH 10 and 60 °C after a 20-min incubation.
Received: 30 October 1998 / Received revision: 16 February 1999 / Accepted: 20 February 1999 相似文献
16.
Penicillin V acylase was produced, both intracellularly and extracellularly, by Fusarium sp. SKF 235 grown in submerged fermentation. When neopeptone was added to the medium, >95% of the penicillin V acylase was extracellular. In the absence of a complex organic nitrogen source, the fungus produced low levels of totally intracellular penicillin V acylase. MgSO4 was essential for synthesis of the enzyme, which was induced by phenoxyacetic acid and penicillin V. The maximum yield of penicillin V acylase was 430 IU/g dry cell wt. The optimum pH value and temperature for the penicillin V acylase were 6.5 and 55°C, respectively. 相似文献
17.
The influence of low temperature (5–29 °C) on the methanogenic activity of non-adapted digested sewage sludge and on temperature/leachate-adapted
biomass was assayed by using municipal landfill leachate, intermediates of anaerobic degradation (propionate) and methane
precursors (acetate, H2/CO2) as substrates. The temperature dependence of methanogenic activity could be described by Arrhenius-derived models. However,
both substrate and adaptation affected the temperature dependence. The adaptation of biomass in a leachate-fed upflow anaerobic
sludge-blanket reactor at approximately 20 °C for 4 months resulted in a sevenfold and fivefold increase of methanogenic activity
at 11 °C and 22 °C respectively. Both acetate and H2/CO2 were methanized even at 5 °C. At 22 °C, methanogenic activities (acetate 4.8–84 mM) were 1.6–5.2 times higher than those
at 11 °C. The half-velocity constant (K
s) of acetate utilization at 11 °C was one-third of that at 22 °C while a similar K
i was obtained at both temperatures. With propionate (1.1–5.5 mM) as substrate, meth‐anogenic activities at 11 °C were half
those at 22 °C. Furthermore, the residual concentration of the substrates was not dependent on temperature. The results suggest
that the adaptation of biomass enables the achievement of a high treatment capacity in the anaerobic process even under psychrophilic
conditions.
Received: 23 December 1996 / Received last revision: 18 June 1997 / Accepted: 23 June 1997 相似文献
18.
S Hayashi S Sako H Yokoi Y Takasaki K Imada 《Journal of industrial microbiology & biotechnology》1999,22(3):160-163
β-Glucosidase hydrolyzing cellobiose was extracted from Aureobasidium sp ATCC 20524 and purified to homogeneity. The molecular mass was estimated to be about 331 kDa. The enzyme contained 26.5%
(w/w) carbohydrate. The optimum pH and temperature for the enzyme reaction were pH 4 and 80°C, respectively. The enzyme was
stable at a wide range of pH, 2.2–9.8, after 3 h and at 75°C for 15 min. The kinetic parameters were determined. The enzyme
was relatively stable against typical organic enzyme inhibitors. The enzyme also hydrolyzed gentiobiose, p-nitrophenyl-β-glucoside and salicin.
Received 05 November 1998/ Accepted in revised form 14 February 1999 相似文献
19.
M. Eriksson G. Dalhammar A.-K. Borg-Karlson 《Applied microbiology and biotechnology》1999,51(4):532-535
A hydrocarbon mixture containing p-xylene, naphthalene, Br-naphthalene and straight aliphatic hydrocarbons (C14 to C17) was aerobically degraded without lag phase by a natural uncontaminated potting soil at 20 °C and 6 °C. Starting concentrations
were approximately 46 ppm for the aromatic and 13 ppm for the aliphatic compounds. All aliphatic hydrocarbons were degraded
within 5 days at 20 °C, to levels below detection (ppb levels) but only down to 10% of initial concentration at 6 °C. Naphthalene
was degraded within 12 days at 20 °C and unaffected at 6 °C. At 20 °C p-xylene was degraded within 20 days, but no degradation occurred at 6 °C. Br-naphthalene was only removed down to 30% of initial
concentration at 20 °C, with no significant effect at 6 °C. The biodegradation was monitored with head space solid-phase microextraction
and gas chromatography–mass spectrometry.
Received: 5 October 1998 / Received revision: 4 December 1998 / Accepted: 5 December 1998 相似文献
20.
Cold adaptation of a mesophilic serine protease, subtilisin, by in vitro random mutagenesis 总被引:2,自引:0,他引:2
Artificial cold adaptation of a mesophilic protease, subtilisin BPN′, was attempted by means of random mutagenesis of its
entire gene coupled with screening of cleared-zone-forming colonies on skim-milk plates at a low temperature. Out of sixty
clones screened at 10 °C, one mutant enzyme (termed M-15) was found to acquire higher proteolytic activities, specifically
dependent on low temperatures ranging from 10 °C to 1 °C, in comparison with those of the wild-type. DNA sequencing analysis
revealed that, by this mutation, the 84th amino acid residue, valine, was substituted by isoleucine, which is located 1.5
nm from the center of the catalytic triad in the tertiary structure of subtilisin. By kinetic analysis of the purified enzyme
samples, the higher proteolytic activities of M-15 at low temperatures were found to be due to the decrease in the K
m value. There was no difference in thermostability between the wild-type and mutant enzymes, when tested by heat treatment.
Circular dichroism spectra also showed no difference between them at 10 °C, indicating that the mutation of V84I had no effect
on the secondary structure of subtilisin.
Received: 22 April 1996 / Received last revision: 29 July 1996 / Accepted: 24 August 1996 相似文献