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1.
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
2.
Adaptation and acclimation of growth and photosynthesis of five Antarctic red algae to low temperatures 总被引:2,自引:0,他引:2
Temperature requirements for growth, photosynthesis and dark respiration were determined for five Antarctic red algal species.
After acclimation, the stenothermal species Gigartina skottsbergii and Ballia callitricha grew at 0 or up to 5 °C, respectively; the eurythermal species Kallymenia antarctica, Gymnogongrus antarcticus and Phyllophora ahnfeltioides grew up to 10 °C. The temperature optima of photosynthesis were between 10 and 15 °C in the stenothermal species and between
15 and 25 °C in the eurythermal species, irrespective of the growth temperature. This shows that the temperature optima for
photosynthesis are located well below the optima from species of other biogeographical regions, even from the Arctic. Respiratory
rates rose with increasing temperatures. In contrast to photosynthesis, no temperature optimum was evident between 0 and 25 °C.
Partial acclimation of photosynthetic capacity to growth temperature was found in two species. B. callitricha and Gymnogongrus antarcticus acclimate to 0 °C, and 5 and 0 °C, respectively. But acclimation did in no case lead to an overall shift in the temperature
optimum of photosynthesis. B. callitricha and Gymnogongrus antarcticus showed acclimation of respiration to 5 °C, and P. ahnfeltioides to 5 and 10 °C, resulting in a temperature independence of respiration when measured at growth temperature. With respect
to the acclimation potential of the species, no distinction can be made between the stenothermal versus the eurythermal group.
(Net)photosynthetic capacity:respiration (P:R) ratios showed in all species highest values at 0 °C and decreased continuously to values lower than 1.0 at 25 °C. In turn,
the low P:R ratios at higher temperatures are assumed to determine the upper temperature growth limit of the studied species. Estimated
daily carbon balance reached values between 4.1 and 30.7 mg C g−1 FW day−1 at 0 °C, 16:8 h light/dark cycle, 12–40 μmol m−2 s−1.
Received: 4 November 1999 / Accepted: 7 March 2000 相似文献
3.
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
4.
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
5.
A Clostridium thermocellum gene, xynX, coding for a xylanase was cloned and the complete nucleotide sequence was determined. The xylanase gene of Clostridium thermocellum consists of an ORF of 3261 nucleotide encoding a xylanase (XynX) of 1087 amino acid residues (116 kDa). Sequence analysis
of XynX showed a multidomain structure that consisted of four different domains: an N-terminal thermostabilizing domain homologous
to sequences found in several thermophilic enzymes, a catalytic domain homologous to family 10 glycosyl hydrolases, a duplicated
cellulose-binding domain (CBD) homologous to family IX CBDs, and a triplicated S-layer homologous domain. A deletion mutant
of xynX having only the catalytic region produced a mutant enzyme XynX-C which retained catalytic activity but lost thermostability.
In terms of half-life at 70 °C, the thermostability of XynX-C was about six times lower than that of the other mutant enzyme,
XynX-TC, produced by a mutant containing both the thermostabilizing domain and the catalytic domain. The optimum temperature
of XynX-C was about 5–10 °C lower than that of XynX-TC.
Received: 12 January 2000 / Received revision: 24 April 2000 / Accepted: 1 May 2000 相似文献
6.
The kinetics of continuous oxidation of ferrous iron by immobilized cells of Thiobacillus ferrooxidans was studied in a packed-bed bioreactor. Polyurethane foam biomass support particles were used as carriers for cell immobilization.
Effects of ferrous iron concentration and its volumetric loading on the kinetics of the reaction were investigated. Media
containing different concentrations of ferrous iron in the range 5–20 kg m-3 were tested. For each medium the kinetics of the reaction at different volumetric loadings of ferrous iron, at a constant
temperature of 30°C, were determined. With media containing 5 kg m-3 and 10 kg m-3 Fe2+, the fastest oxidation rates of 34.25 kg m-3 h-1 and 32 kg m-3 h-1 were achieved at a dilution rate of around 6 h-1, which represents a residence time of 10 min. Employing a higher concentration of ferrous iron (20 kg m-3) in the medium resulted in lower oxidation rates, with a maximum value of 10 kg m-3 h-1, indicating an inhibitory effect of ferrous iron on growth and activity of T. ferrooxidans. The reliable performance of the bioreactor during the course of the experiments confirmed the suitability of polyurethane
foam biomass support particles as carriers for T. ferrooxidans immobilization.
Received: 5 December 1995/Received revision: 21 April 1996/Accepted: 29 April 1996 相似文献
7.
Cells of a suspension culture of Doritaenopsis cv. New Toyohashi were placed in a mixture of 2 M glycerol and 0.4 M sucrose for 15 min at room temperature and then dehydrated with a vitrification solution (PVS2) for 1–3 h on ice and plunged
into liquid nitrogen. The highest viability (64% by 2,3,5-triphenyltetrazolium chloride stainability) was obtained when the
cells were precultured in liquid New Dogashima medium with 0.1 M sucrose and 1.0 mg/l abscisic acid for 1 week at 25 °C in the light. Dehydration by PVS2 was important for the cryopreservation
of Doritaenopsis cells. Protocorm-like bodies were induced from cryopreserved cells without morphological variations.
Received: 18 January 2000 / Revision received: 16 June 2000 / Accepted: 22 June 2000 相似文献
8.
C. J. Baxter N. Magan B. Lane H. G. Wildman 《Applied microbiology and biotechnology》1998,49(3):328-332
A Phoma sp., known to produce the pharmaceutically active metabolites squalestatin 1 (S1) and squalestatin 2 (S2), was cultured on
malt-extract/agar (MEA) over a range of water activities (a
w, 0.995–0.90) and temperatures (10–35 °C) to investigate the influence on growth and metabolite production. Use of the ionic
solute NaCl to adjust a
w resulted in significantly lower (P < 0.01) squalestatin yields than when the Phoma sp. was grown on MEA amended with the non-ionic solute glycerol. Water activity and temperature and their interactions were
highly significant factors (P < 0.001) affecting growth of the Phoma sp., with optimum conditions of 0.998–0.980 a
w and 25 °C. Squalestatin production was similarly influenced by a
w, temperature, time and their interactions (P < 0.001). S1 and S2 production occurred over a narrower a
w and temperature range than growth, with a slightly lower optimum a
w range of 0.995–0.980 a
w. The optimum temperature for squalestatin production varied from 20 °C (S1) to 25 °C (S2) and yields of S2 were up to 1000
times lower than those of S1. The ratio of S1 and S2 produced by the Phoma sp. was influenced by a
w and temperature, with highest values at 0.99–0.98 a
w, and at 15 °C. Incubation times of 28 days gave highest yields of both S1 and S2. Up to 2000-fold increases in squalestatin
yields were measured at optimum environmental conditions, compared to the unmodified MEA. This indicates the need to consider
such factors in screening systems used to detect biologically active lead compounds produced by fungi.
Received: 2 June 1997 / Received last revision: 6 November 1997 / Accepted: 7 November 1997 相似文献
9.
Booth DT Thompson MB Herring S 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(4):269-276
Eggs of two small Australian lizards, Lampropholis guichenoti and Bassiana duperreyi, were incubated to hatching at 25 °C and 30 °C. Incubation periods were significantly longer at 25 °C in both species, and
temperature had a greater effect on the incubation period of B. duperreyi (41.0 days at 25 °C; 23.1 days at 30 °C) than L. guichenoti (40.1 days at 25 °C; 27.7 days at 30 °C). Patterns of oxygen consumption were similar in both species at both temperatures,
being sigmoidal in shape with a fall in the rate of oxygen consumption just prior to hatching. The higher incubation temperature
resulted in higher peak and higher pre-hatch rates of oxygen consumption in both species. Total amount of oxygen consumed
during incubation was independent of temperature in B. duperreyi, in which approximately 50 ml oxygen was consumed at both temperatures, but eggs of L. guichenoti incubated at 30 °C consumed significantly more (32.6 ml) than eggs incubated at 25 °C (28.5 ml). Hatchling mass was unaffected
by either incubation temperature or the amount of water absorbed by eggs during incubation in both species. The energetic
production cost of hatchling B. duperreyi (3.52 kJ · g−1) was independent of incubation temperature, whereas in L. guichenoti the production cost was greater at 30 °C (4.00 kJ · g−1) than at 25 °C (3.47 kJ · g−1). Snout-vent lengths and mass of hatchlings were unaffected by incubation temperature in both species, but hatchling B. duperreyi incubated at 30 °C had longer tails (29.3 mm) than those from eggs incubated at 25 °C (26.2 mm). These results indicate that
incubation temperature can affect the quality of hatchling lizards in terms of embryonic energy consumption and hatchling
morphology.
Accepted: 27 January 2000 相似文献
10.
Shake-flask cultivation of T. lanuginosus strain SSBP on coarse corn cobs yielded β-xylanase levels of 56,500 nkat/ml at 50 °C, whereas other hemicellulases (β-xylosidase,
β-glucosidase, and α-l-arabinofuranosidase) were produced at levels less than 7 nkat/ml. Cultivation on d-xylose yielded much lower levels of xylanase (350 nkat/ml), although other hemicellulase levels were similar to those produced
on corn cobs. The influence of agitation rate and dissolved oxygen tension (DOT) on hemicellulase production was studied further
in a bioreactor. On xylose, xylanase activities of 4,330 nkat/ml and 4,900 nkat/ml were obtained at stirrer speeds up to 1,400 rpm
to control DOT. At a constant stirrer speed of 400 rpm, xylanase activities of 10,930 nkat/ml and 15,630 nkat/ml were obtained
when cultivated on xylose and beechwood xylan respectively, despite DOT levels below 5% for the duration of fermentation.
The results indicate that there is an interaction between agitation rate and DOT, impacting on xylanase and accessory enzyme
production. Higher agitation rates favoured the production of xylosidase, arabinofuranosidase and glucosidase by T. lanuginosus strain SSBP, whereas the lower agitation rates favoured xylanase production. Rheological difficulties precluded cultivation
on corn cobs in the bioreactor. Volumetric xylanase productivities of 1,060,000 nkat/l · h and 589,000 nkat/l · h obtained
on beechwood xylan and xylose indicate that T. lanuginosus strain SSBP is a hyper-xylanase producer with considerable industrial potential.
Received: 5 May 1999 / Received revision: 31 May 2000 / Accepted: 3 June 2000 相似文献
11.
B. L. García A. S. Ball J. Rodríguez M. I. Pérez-Leblic M. E. Arias J. L. Copa-Patiño 《Applied microbiology and biotechnology》1998,50(2):213-218
Streptomyces avermitilis CECT 3339 produces extracellular ferulic acid esterase (FAE) activity during growth on a range of lignocellulose substrates.
Maximal levels of FAE activity were detected in culture filtrates from S. avermitilis CECT 3339 grown in media containing wheat bran and yeast extract as carbon and nitrogen sources respectively. Biochemical
characterization of this enzyme activity revealed that it was 100-fold higher when wheat bran was pretreated with Celluclast
(a mix of hydrolytic enzymes). FAE was found to be end-product-inhibited. Characterization of the properties of the enzyme
showed that FAE exhibited an activity optimum pH at 6 with pH stability between pH 6 and 8. The optimum temperature was 50 °C
while the temperature stability was between 30 °C and 40 °C, with rapid inactivation at 60 °C and above. The characteristics
and stability of FAE from S. avermitilis CECT 3339 suggest a potential role for this enzyme in combination with endoxylanases for the upgrading of plant-residue silage
and for biopulping.
Received: 17 November 1997 / Received revision: 13 March 1998 / Accepted: 13 April 1998 相似文献
12.
Laccase can be used for enzymatic detoxification of lignocellulosic hydrolysates. A Saccharomyces cerevisiae strain with enhanced resistance to phenolic inhibitors and thereby improved ability to ferment lignocellulosic hydrolysates
would presumably be obtained by heterologous expression of laccase. Sequencing of the cDNA for the novel laccase gene lcc2 from the lignin-degrading basidiomycete Trametes versicolor showed that it encodes an isoenzyme of 499 amino-acid residues preceded by a 21-residue signal peptide. By comparison with
Edman degradation data, it was concluded that lcc2 encodes an isoenzyme corresponding to laccase A. The gene product of lcc2 displays 71% identity with the previously characterized T. versicolor lcc1 gene product. An alignment of laccase sequences revealed that the T. versicolor isoenzymes in general are more closely related to corresponding isoenzymes from other white-rot fungi than to the other T. versicolor isoenzymes. The multiplicity of laccase is thus a conserved feature of T. versicolor and related species of white-rot fungi. When the T. versicolor lcc2 cDNA was expressed in S. cerevisiae, the production of active enzyme was strongly dependent on the temperature. After 3 days of incubation, a 16-fold higher laccase
activity was found when a positive transformant was kept at 19 °C instead of 28 °C. Similar experiments with Pichia pastoris expressing the T. versicolor laccase gene lcc1 also showed that the expression level was favoured considerably by lower cultivation temperature, indicating that the observation
made for the S. cerevisiae expression system is of general significance.
Received: 8 December 1998 / Received revision: 9 April 1999 / Accepted: 16 April 1999 相似文献
13.
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
14.
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
15.
Torres R Ramón F de la Mata I Acebal C Castillón MP 《Applied microbiology and biotechnology》1999,53(1):81-84
At 28 °C, Streptomyces lavendulae produced high levels of penicillin V acylase (178 IU/l of culture) when grown on skim milk as the sole nutrient source for
275 h. The enzyme showed catabolite repression by glucose and was produced in the stationary phase of growth. Penicillin V
was a good inducer of penicillin V acylase formation, while phenoxyacetic acid, the side-chain moiety of penicillin V, did
not alter enzyme production significantly. The enzyme was stable between pH 6 and 11 and at temperatures from 20 °C to 55 °C.
This extracellular enzyme was able to hydrolyse natural penicillins and unable to hydrolyse penicillin G.
Received: 22 March 1999 / Received revision: 16 June 1999 / Accepted: 20 June 1999 相似文献
16.
Bustard MT McEvoy EM Goodwin JA Burgess JG Wright PC 《Applied microbiology and biotechnology》2000,54(3):424-431
The aerobic biodegradation of high concentrations of 1-propanol and 2-propanol (IPA) by a mixed microbial consortium was
investigated. Solvent concentrations were one order of magnitude greater than any previously reported in the literature. The
consortium utilized these solvents as their sole carbon source to a maximum cell density of 2.4 × 109 cells ml−1. Enrichment experiments with propanol or IPA as carbon sources were carried out in batch culture and maximum specific growth
rates (μmax) calculated. At 20 °C, μ
max values were calculated to be 0.0305 h−1 and 0.1093 h−1 on 1% (v/v) IPA and 1-propanol, respectively. Growth on propanol and IPA was carried out between temperatures of 10 °C and
45 °C. Temperature shock responses by the microbial consortium at temperatures above 45 °C were demonstrated by considerable
cell flocculation. An increase in propanol substrate concentration from 1% (v/v) to 2% (v/v) decreased the μ
max from 0.1093 h−1 to 0.0715 h−1. Maximum achievable biodegradation rates of propanol and IPA were 6.11 × 10−3% (v/v) h−1 and 2.72 × 10−3% (v/v) h−1, respectively. Generation of acetone during IPA biodegradation commenced at 264 h and reached a maximum concentration of
0.4% (v/v). The results demonstrate the potential of mixed microbial consortia in the bioremediation of solvent-containing
waste streams.
Received: 14 December 1999 / Received revision: 3 April 2000 / Accepted: 7 April 2000 相似文献
17.
C. Åkerberg K. Hofvendahl G. Zacchi B. Hahn-Hägerdal 《Applied microbiology and biotechnology》1998,49(6):682-690
A kinetic model of the fermentative production of lactic acid from glucose by Lactococcus lactis ssp. lactis ATCC 19435 in whole-wheat flour has been developed. The model consists of terms for substrate and product inhibition as well
as for the influence of pH and temperature. Experimental data from fermentation experiments under different physical conditions
were used to fit and verify the model. Temperatures above 30 °C and pH levels below 6 enhanced the formation of by-products
and d-lactic acid. By-products were formed in the presence of maltose only, whereas d-lactic acid was formed independently of the presence of maltose although the amount formed was greater when maltose was present.
The lactic acid productivity was highest between 33 °C and 35 °C and at pH 6. In the concentration interval studied (up to
180 g l−1 glucose and 89 g l−1 lactic acid) simulations showed that both substances were inhibiting. Glucose inhibition was small compared with the inhibition
due to lactic acid.
Received: 28 October 1997 / Received revision: 3 February 1998 / Accepted: 6 February 1998 相似文献
18.
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
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.
Production of high yields of arachidonic acid in a fed-batch system by Mortierella alpina ATCC 32222
Of six strains of Mortierella tested, Mortierella alpina ATCC 32222 produced the highest yields of arachidonic acid. Supplementation of soy flour (1% w/v) and vegetable oils (1%
v/v) significantly increased the biomass, lipid content and arachidonic acid level. Replacement of NaNO3 with corn steep liquor (1% w/v) also improved arachidonic acid production. A fed-batch culture system at 25 °C, producing
a high biomass (52.4 g/l) and arachidonic acid content (9.1 g/l) in 8␣days, was developed. A fed-batch system at low temperature
(15 °C) gave even higher arachidonic acid levels (11.1 g/l) in 11 days.
Received: 28 October 1996 / Received revision: 3 March 1997 / Accepted: 7 March 1997 相似文献