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1.
Extraction of medium after incubation of the fungus, Cunninghamella elegans, with 0.03% (w/v) 1-methylnaphthalene produced mainly 1-hydroxymethylnaphthalene together with some 1-naphthoic acid and
hydroxynaphthoic acid. Higher concentrations of substrate were inhibitory to biotransformation. Similar incubations with 1-naphtoic
acid as substrate resulted in reduction of the carboxyl group to give 1-hydroxymethylnaphthalene. When 6-methylquinoline was
used, the main product was 6-hydroxymethylquinoline but also some quinoline-6-carboxylic acid and some 6-methylquinoline-N-oxide were identified. In a 2-l fermenter 2.5 g substrate was transformed in 324 h. The 6-hydroxymethylquinoline was also
produced by reduction of quinoline-6-carboxylic acid by the organism.
Received: 9 March 1998 / Received revision: 15 June 1998 / Accepted: 19 June 1998 相似文献
2.
Addition of sodium acetate to chemically defined MP2 medium was found to increase and stabilize solvent production by Clostridium beijerinckii BA101, a solvent-hyperproducing mutant derived from C. beijerinckii NCIMB 8052. C. beijerinckii BA101 demonstrated a greater increase in solvent production than C. beijerinckii NCIMB 8052 when sodium acetate was added to MP2 medium. In 1-l batch fermentations, C. beijerinckii BA101 produced 32.6 g/l total solvents, with butanol at 20.9 g/l, when grown in MP2 medium containing 60 mM sodium acetate
and 8% glucose. To our knowledge, these values represent the highest solvent and butanol concentrations produced by a solventogenic
Clostridium strain when grown in batch culture.
Received: 29 September 1998 / Received revision: 13 February 1999 / Accepted: 26 February 1999 相似文献
3.
Microorganisms and commercial enzymes were screened for their ability to produce (R)-3-pentyn-2-ol from racemic 3-pentyn-2-ol esters through stereospecific hydrolysis. Among the esters formed with acetic acid,
propionic acid, hexanoic acid and benzoic acid, the acetate was most effectively hydrolyzed by microbial cells and commercial
lipases with high stereospecificity. Rhodococcus rubropertinctus AKU NOC082 was a good catalyst for (R)-3-pentyn-2-ol production through the hydrolytic resolution of racemic 3-pentyn-2-yl acetate. With 15%, 25% and 50% (v/v)
racemic 3-pentyn-2-yl acetate as the substrate, 42.6%, 40.8% and 40.0% was hydrolyzed in 5 h, 10 h and 98 h respectively,
under the optimized conditions (pH 7.0, 30 °C, 7.5% wet cell concentration), the (R) enantiomer of 3-pentyn-2-ol being formed with an optical purity of 97.8%, 98.0% and 94.2% respectively.
Received: 2 June 1998 / Received revision: 3 August 1998 / Accepted: 3 September 1998 相似文献
4.
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
5.
We fused the Pseudomonas aeruginosa recA promoter to a promoterless Vibrio fisherilux operon. This recA–lux fusion (pMOE15) was introduced into wild-type P. aeruginosa strain FRD1 and recA expression was monitored by measuring 490-nm light production. The RM4440 strain responded to increasing doses of ultraviolet
radiation by an increase in its bioluminescence. RM4440 has the potential to be useful as a biosensor for the presence of
DNA-damaging agents in the environment.
Received: 18 February 1998 / Received revision: 18 June 1998 / Accepted: 27 June 1998 相似文献
6.
Efficacy of silver thiosulfate (STS) in reducing ethylene-induced culture abnormalities during minimal growth conservation
of microplants was studied in seven potato (Solanum tuberosum L.) genotypes. Different concentrations of STS (0, 1.5, 3.0, 4.5, 6.0, 7.5 and 9.0 μg ml–1) were tested in minimal growth medium based on MS medium supplemented with 20 g l–1 mannitol and 40 g l–1 sucrose. STS improved the microplant growth and reduced the culture abnormalities during prolonged maintenance of potato
shoot cultures in vitro. The beneficial effect of STS was most prominent for number of green leaves per microplant and leaf
senescence. After 16 months of storage, desirable microplant growth was observed in cultures conserved in medium containing
6.0–9.0 μg ml–1 STS. The profile of the peroxidase isozymes of conserved cultures did not show any apparent genetic variation due to the
presence of STS in the conservation medium.
Received: 2 September 1998 / Revision received: 20 November 1998 / Accepted: 12 December 1998 相似文献
7.
When grown on vegetable oils and their derivatives, the smut fungus Ustilago maydis (DSM 4500 and ATCC 14826) produces several glycolipids under nitrogen-limiting conditions. With 45 g l−1 sunflower oil fatty acids (technical grade) a yield of 30 g l−1 glycolipid was achieved. The resulting mixture contained predominantly mannosylerythritol lipids together with smaller amounts
of cellobiose lipids. The production of the more polar cellobiose lipids was enhanced when glucose was used as carbon source.
The molecular structure of the main components of the glycolipid mixture were elucidated by a combination of NMR spectroscopic
and mass-spectrometric techniques.
Received: 22 June 1998 / Received revision: 11 September 1998 / Accepted: 13 September 1998 相似文献
8.
During cassava starch production, large amounts of cyanoglycosides were released and hydrolysed by plant-borne enzymes, leading
to cyanide concentrations in the wastewater as high as 200 mg/l. For anaerobic degradation of the cyanide during pre-acidification
or single-step methane fermentation, anaerobic cultures were enriched from soil residues of cassava roots and sewage sludge.
In a pre-acidification reactor this culture was able to remove up to 4 g potassium cyanide/l of wastewater at a hydraulic
retention time (t
HR) of 4 days, equivalent to a maximal cyanide space loading of 400 mg CN− l−1 day−1. The residual cyanide concentration was 0.2–0.5 mg/l. Concentrated cell suspensions of the mixed culture formed ammonia and
formate in almost equimolar amounts from cyanide. Little formamide was generated by chemical decay. A concentration of up
to 100 mmol ammonia/l had no inhibitory effect on cyanide degradation. The optimal pH for cyanide degradation was 6–7.5, the
optimal temperature 25–37 °C. At a pH of 5 or lower, cyanide accumulated in the reactor and pre-acidification failed. The
minimal t
HR for continuous cyanide removal was 1.5 days. The enriched mixed culture was also able to degrade cyanide in purely mineralic
wastewater from metal deburring, either in a pre-acidification reactor with a two-step process or in a one-step methanogenic
reactor. It was necessary to supplement the wastewater with a carbon source (e.g. starch) to keep the population active enough
to cope with any possible inhibiting effect of cyanide.
Received: 29 April 1998 / Received revision: 8 June 1998 / Accepted: 14 June 1998 相似文献
9.
M.-P. Bousquet R.-M. Willemot P. Monsan E. Boures 《Applied microbiology and biotechnology》1998,50(2):167-173
α-Transglucosidase from Talaromycesduponti was used to synthesize different alkyl-α-d-glucosides from α(1-4) linked carbohydrate donors. The enzymatic preparation, purified by a single step, consisting of hydrophobic
interaction chromatography, was sufficiently pure for very stereospecific synthesis to be achieved. Biphasic and homogeneous
organic media could be compared for such purposes. Yields appeared to be two- to threefold higher in low-water biphasic media.
High concentrations of the glucosyl donor were present in the aqueous phase, while water-immiscible alcohols were used as
glucosyl acceptors. The high efficiency of the method was attributed to the shift of the thermodynamic equilibrium thanks
to the extraction of the product from the aqueous phase, where the reaction occurs, into the organic phase. Operated in a
continuous biphasic reactor, T. dupontiα-transglucosidase showed a good thermostability with a half-life of 23 days at 30 °C.
Received: 26 January 1998 / Received revision: 15 April 1998 / Accepted: 19 April 1998 相似文献
10.
Candida tropicalis, a strain isolated from the sludge of a factory manufacturing xylose, produced a high xylitol concentration of 131 g/l from
150 g/l xylose at 45 h in a flask. Above 150 g/l xylose, however, volumetric xylitol production rates decreased because of
a lag period in cell growth. In fed-batch culture, the volumetric production rate and xylitol yield from xylose varied substantially
with the controlled xylose concentration and were maximum at a controlled xylose concentration of 60 g/l. To increase the
xylitol yield from xylose, feeding experiments using different ratios of xylose and glucose were carried out in a fermentor.
The maximum xylitol yield from 300 g/l xylose was 91% at a glucose/xylose feeding ratio of 15%, while the maximum volumetric
production rate of xylitol was 3.98 g l−1 h−1 at a glucose/xylose feeding ratio of 20%. Xylitol production was found to decrease markedly as its concentration rose above
250 g/l. In order to accumulate xylitol to 250 g/l, 270 g/l xylose was added in total, at a glucose/xylose feeding ratio of
15%. Under these conditions, a final xylitol production of 251 g/l, which corresponded to a yield of 93%, was obtained from
270 g/l xylose in 55 h.
Received: 20 April 1998 / Received revision: 29 May 1998 / Accepted: 19 June 1998 相似文献
11.
A transketolase mutant was first isolated from Corynebacterium glutamicum, an organism of industrial importance. The mutant strain exhibited an absolute requirement for shikimic acid or the aromatic
amino acids and vitamins for growth, and also failed to grow on ribose or gluconic acid as sole carbon source, even with the
aromatic supplement. All of these defective properties were fully restored in spontaneous revertants, indicating the existence
of a single transketolase in C. glutamicum that was indispensable both for aromatic biosynthesis and for utilization of these carbohydrates in vivo. The transketolase
mutant accumulated ribulose extracellularly when cultivated in glucose medium with shikimic acid, but no ribose was detected.
Received: 10 April 1998 / Received revision: 26 May 1998 / Accepted: 14 June 1998 相似文献
12.
Influence of microbial concentration on the rheology of non-Newtonian fermentation broths 总被引:2,自引:0,他引:2
The objective of this study was to quantify the effect of fungal biomass concentration on the rheology of non-Newtonian fermentation
systems. Batch fermentations of Penicillium chrysogenum were carried out with glucose as the sole carbon source. The flow behavior of the system was characterized at various fermentation
times and was adequately described by the power-law model. The apparent viscosity of the fermentation broth was significantly
affected by biomass concentrations in the fermenter. Fermentation broths containing 17.71 g/l biomass as dry weight were characterized
by an apparent viscosity of 0.25 Pa s at a shear rate of 50 s−1. Microbial concentration also affected the power-law flow-behavior index and the consistency index. The value of the consistency
index ranged from 0.002 Pa s
n
at a biomass concentration of 0.1 g/l to 6.14 Pa s
n
at a biomass concentration of 17.71 g/l. The flow-behavior index decreased from an initial value of 1 to a final value of
0.17. Simple empirical correlations have been proposed to quantify the dependence of the power-law parameters on fungal biomass
concentration. Experimental data obtained in this study were accurately described by these correlations. The general applicability
of these relationships was tested, using previously published rheological data on Aspergillus awamori and Aspergillus niger fermentation broths, and good agreement was seen between experimental data and the predictions from the empirical correlations.
Received: 24 March 1998 / Received revision: 10 September 1998 / Accepted: 16 October 1998 相似文献
13.
G. H. van Geel-Schutten F. Flesch B. ten Brink M. R. Smith L. Dijkhuizen 《Applied microbiology and biotechnology》1998,50(6):697-703
A total of 182 Lactobacillus strains were screened for production of extracellular polysaccharides (EPS) by a new method: growth in liquid media with
high sugar concentrations. Sixty EPS-positive strains were identified; 17 strains produced more than 100 mg/l soluble EPS.
Sucrose was an excellent substrate for abundant EPS synthesis. The ability to produce glucans appears to be widespread in
the genus Lactobacillus. The monosaccharide composition of EPS produced by Lactobacillus reuteri strain LB 121 varied with the growth conditions (solid compared to liquid medium) and the sugar substrates (sucrose or raffinose)
supplied in the medium. Strain LB 121 produced both a glucan and a fructan on sucrose, but only a fructan on raffinose. This
is the first report of fructan production by a Lactobacillus species. EPS production increased with increasing sucrose concentrations and involved extracellular sucrase-type enzymes.
Received: 20 March 1998 / Received revision: 12 August 1998 / Accepted: 12 August 1998 相似文献
14.
J. Lange E. Hammer M. Specht W. Francke F. Schauer 《Applied microbiology and biotechnology》1998,50(3):364-368
Cells of the yeast strain Debaryomyces vanrijiae SBUG 770, grown with glucose, converted biphenyl to 4-hydroxybiphenyl as the major metabolite. In addition, 2-hydroxybiphenyl
was formed in minor amounts. No further degradation of these substances was detected. However, these monohydroxylated derivatives
were oxidised by alkane-grown cells in the presence of the co-metabolic substrate, tetradecane. Under these conditions 2-hydroxybiphenyl
was oxidised to 2,5-dihydroxybiphenyl, and 4-hydroxybiphenyl was rapidly metabolised by formation of two major metabolites.
One was identified as 3,4-dihydroxybiphenyl. Characterisation of the second product as 4-phenylmuconolactone points to a further
metabolism of the initially formed dihydroxylated biphenyl via ortho-ring fission.
Received: 8 May 1998 / Received revision: 26 June 1998 / Accepted: 2 July 1998 相似文献
15.
The influence of ammonia on the anaerobic degradation of peptone by mesophilic and thermophilic populations of biowaste was
investigated. For peptone concentrations from 5 g l−1 to 20 g l−1 the mesophilic population revealed a higher rate of deamination than the thermophilic population, e.g. 552 mg l−1 day−1 compared to 320 mg l−1 day−1 at 10 g l−1 peptone. The final degree of deamination of the thermophilic population was, however, higher: 102 compared to 87 mg NH3/g peptone in the mesophilic cultures. If 0.5–6.5 g l−1 ammonia was added to the mesophilic biowaste cultures, deamination of peptone, degradation of its chemical oxygen demand
(COD) and formation of biogas were increasingly inhibited, but no hydrogen was formed. The thermophilic biowaste cultures
were most active if around 1 g ammonia l−1 was present. Deamination, COD degradation and biogas production decreased at lower and higher ammonia concentrations and
hydrogen was formed in addition to methane. Studies of the inhibition by ammonia of peptone deamination, COD degradation and
methane formation revealed a K
i (50%) for NH3 of 92, 95 and 88 mg l−1 at 37 °C and 251, 274 and 297 mg l−1 at 55 °C respectively. This indicated that the thermophilic flora tolerated significantly more NH3 than the mesophilic flora. In the mesophilic reactor effluent 4.6 × 108 peptone-degrading colony-forming units (cfu)/ml were culturable, whereas in the thermophilic reactor effluent growth of only
5.6 × 107 cfu/ml was observed.
Received: 24 April 1998 / Received revision: 26 June 1998 / Accepted: 27 June 1998 相似文献
16.
T. Potrawfke T.-H. Löhnert K. N. Timmis R.-M. Wittich 《Applied microbiology and biotechnology》1998,50(4):440-446
The biphenyl-mineralizing bacterium Burkholderia sp. strain LB400 also utilized 3-chloro-, 4-chloro-, 2,3′-dichloro- and 2,4′-dichlorobiphenyl for growth. By the attack of the initial enzyme a chlorine was eliminated dioxygenolytically
from position 2 of one of the aromatic rings when hydrogens of both were substituted by chlorine. The strain mineralized 3-chloro-
and 2,3′-dichlorobiphenyl via the central intermediate 3-chlorobenzoate through its chlorocatechol pathway enzymes, but excreted
stoichiometric amounts of 4-chlorobenzoate from 4-chloro- and 2,4′-dichlorobiphenyl. These two compounds were mineralized by a co-culture of strain LB400 and a derivative of the (methyl-)
benzoate-degrading strain Pseudomonas putida mt-2 (TOL). The complete degradation was achieved upon transfer of a cluster of at least five genes, encoding the regulated
chlorocatechol pathway operon, from strain LB400 to strain mt-2. This transfer was demonstrated by the polymerase chain reaction.
Received: 15 April 1998 / Received revision: 12 June 1998 / Accepted: 19 June 1998 相似文献
17.
I. Poirier P.-A. Maréchal C. Evrard P. Gervais 《Applied microbiology and biotechnology》1998,50(6):704-709
Escherichia coli and Lactobacillus plantarum were subjected to final water potentials of −5.6 MPa and −11.5 MPa with three solutes: glycerol, sorbitol and NaCl. The water
potential decrease was realized either rapidly (osmotic shock) or slowly (20 min) and a difference in cell viability between
these conditions was only observed when the solute was NaCl. The cell mortality during osmotic shocks induced by NaCl cannot
be explained by a critical volume decrease or by the intensity of the water flow across the cell membrane. When the osmotic
stress is realized with NaCl as the solute, in a medium in which osmoregulation cannot take place, the application of a slow
decrease in water potential resulted in the significant maintenance of cell viability (about 70–90%) with regard to the corresponding
viability observed after a sudden step change to same final water potential (14–40%). This viability difference can be explained
by the existence of a critical internal free Na+ concentration.
Received: 20 May 1998 / Received revision: 31 July 1998 / Accepted: 31 July 1998 相似文献
18.
Dialysis cultures 总被引:8,自引:0,他引:8
Dialysis techniques are discussed as a means for effective removal of low-molecular-mass components from fermentation broth
to reach high cell density. Reactor systems and process strategies, the relevant properties of membranes and examples for
high-density fermentation with dialysis, and problems related to scale-up are addressed. The dialysis technique has turned
out to be very efficient and reliable for obtaining high cell densities. As in dialysis processes the membranes are not perfused,
membrane clogging is not a problem as it is for micro- and ultrafiltration. By applying a “nutrient-split” feeding strategy,
the loss of nutrients can be avoided and the medium is used very efficiently. The potential of dialysis cultures is demonstrated
on the laboratory scale in a membrane dialysis reactor with an integrated membrane and in reactor systems with an external
dialysis loop. In dialysis cultures with different microorganisms (Staphylococci, Escherichia coli, extremophilic microorganisms, Lactobacilli) the cell densities achieved were up to 30 times higher than those of other fermentation methods. The technique enables high
cell densities to be attained without time-consuming medium optimization. For animal cell cultures the concept of a fixed
bed coupled with dialysis proved to be very effective.
Received: 24 March 1998 / Received revision: 18 June 1998 / Accepted: 19 June 1998 相似文献
19.
The biodegradation and toxicity of tetrachloroethylene (C2Cl4) and trichloroethylene (C2HCl3) were studied with different anaerobic enrichment cultures using the following electron donors: acetate, propionate, butyrate,
methanol, formate and hydrogen. All of them sustained dechlorination except propionate, for which C2Cl4 biodegradation rates were not significant. The best results were obtained with butyrate. Hydrogen appeared to be a relevant
electron donor for dechlorination with the present cultures. In the presence of specific inhibitors such as bromoethanesulphonate
or molybdate, a slight inhibition of dechlorination was observed. According to dechlorination kinetics, Monod-type behaviour
was observed up to 120 μM C2Cl4 or 200 μM C2HCl3 with K
s values around 7 μM for both compounds. Dechlorination was partially inhibited at higher concentrations. In contrast, methanogens,
or at least methane production, were more sensitive to the presence of chlorinated ethylenes and inhibition of methanogenesis
was observed to different extents over all the C2Cl4/C2HCl3 concentration range tested, even at the lowest concentrations.
Received: 17 April 1998 / Received revision: 18 June 1998 / Accepted: 19 June 1998 相似文献
20.
The influence of temperature and pH on growth of Leuconostoc mesenteroides subsp. mesenteroides FR52 and production of its two bacteriocins, mesenterocin 52A and mesenterocin 52B, was studied during batch fermentation.
Temperature and pH had a strong influence on the production of the two bacteriocins which was stimulated by slow growth rates.
The optimal temperature was 20 °C for production of mesenterocin 52A and 25 °C for mesenterocin 52B. Optimal pH values were
5.5 and 5.0 for production of mesenterocin 52A and mesenterocin 52B respectively. Thus, by changing the culture conditions,
production of one bacteriocin can be favoured in relation to the other. The relationship between growth and specific production
rates of the two bacteriocins, as a function of the culture conditions, showed different kinetics of production and the presence
of several peaks in the specific production rates during growth.
Received: 13 February 1998 / Received revision: 27 May 1998 / Accepted: 1 June 1998 相似文献