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1.
N2O emission from soil following combined application of fertiliser-N and ground weed residues 总被引:1,自引:0,他引:1
Emissions of N2O and CO2 were measured following combined applications of 15N-labelled fertiliser (100 μg N g−1; 10 atom % excess 15N) and organic olive crop weed residues (Avena sativa, Ononis viscosa, Ridolfia segetum and Olea europea; 100 μg N g−1) to a silt loam soil under controlled environment conditions. The objective was to determine the effect of varying combinations
of inorganic fertiliser and plant residues on these emissions and soil mineral N dynamics. Emissions were generally increased
following application of residues alone, with 23 ng N2O–N g−1 soil (2 ng N2O–N g−1 soil mg−1 biomass) and 389 μg CO2–C g−1 soil (39 μg CO2–C g−1 soil mg−1 biomass) emitted over 28 days after addition of the Ridolfia residues in the absence of fertiliser-N. N2O emissions from these residue-only treatments were strongly negatively correlated with residue lignin content (r = −0.91; P < 0.05), total carbon content (r = −0.90; P < 0.05) and (lignin + polyphenol)-to-N ratio (r = −0.70; P < 0.1). However, changes in the net input of these compounds through application of 25:75, 50:50 and 75:25 proportional mixtures
of Avena and Ononis residues had no effect on emissions compared to their single (0:100 or 100:0) applications. Addition of fertiliser-N increased
emissions (by up to 30 ng N2O–N g−1 28 days−1; 123%), particularly from the low residue-N treatments (Avena and Ridolfia) where a greater quantity of biomass was applied, resulting in emissions above that of the sum from the unfertilised residue
and fertilised control treatments. In contrast, fertiliser application had no impact on emissions from the Olea treatment with the highest polyphenol (2%) and lignin (11%) contents due to strong immobilisation of soil N, and the 15N–N2O data indicated that residue quality had no effect on the denitrification of applied fertiliser-N. Such apparent inconsistencies
mean that before the potential for manipulating N input (organic + inorganic) to lower gaseous N losses can be realised, first
the nature and extent of interactions between the different N sources and any interactions with other compounds released from
the residues need to be better understood. 相似文献
2.
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
3.
A Pseudomonas sp. strain NGK 1 (NCIM 5120) was immobilized in various matrices, namely, alginate, agar (1.8 × 1011 cfu g−1 beads) and polyacrylamide (1.6 × 1011 cfu g−1 beads). The degradation of naphthalene was studied, by freely suspended cells (4 × 1010 cfu ml−1) and immobilized cells in batches, with shaken culture and continuous degradation in a packed-bed reactor. Free cells brought
about the complete degradation of 25 mmol naphthalene after 3 days of incubation, whereas, a maximum of 30 mmol naphthalene
was degraded by the bacteria after 3–4 days of incubation with 50 mmol and 75 mmol naphthalene, and no further degradation
was observed even after 15 days of incubation. Alginate-entrapped cells had degraded 25 mmol naphthalene after 3.5 days of
incubation, whereas agar- and polyacrylamide-entrapped cells took 2.5 days; 50 mmol naphthalene was completely degraded by
the immobilized cells after 6–7 days of incubation. Maximum amounts of 55 mmol, 70 mmol and 67 mmol naphthalene were degraded,
from an initial 75 mmol naphthalene, by the alginate-, agar- and polyacrylamide-entrapped cells after 15 days of incubation.
When the cell concentrations were doubled, 25 mmol and 50 mmol naphthalene were degraded after 2 and 5.5 days of incubation
by the immobilized cells. Complete degradation of 75 mmol naphthalene occurred after 10 days incubation with agar- and polyacrylamide-entrapped␣cells,
whereas only 60 mmol naphthalene was degraded by alginate-entrapped cells after 15 days of␣incubation. Further, with 25 mmol
naphthalene, alginate-, agar- and polyacrylamide-entrapped cells (1.8 × 1011 cfu g−1 beads) could be reused 18, 12 and 23 times respectively. During continuous degradation in a packed-bed reactor, 80 mmol naphthalene
100 ml−1 h−1 was degraded by alginate- and polyacrylamide-entrapped cells whereas 80 mmol naphthalene 125 ml−1␣h−1 was degraded by agar-entrapped cells.
Received: 21 October 1997 / Received revision: 15 January 1998 / Accepted: 18 January 1998 相似文献
4.
B. C. Okeke A. Paterson J. E. Smith I. A. Watson-Craik 《Applied microbiology and biotechnology》1997,48(4):563-569
Sterilised and non-sterilised soils contaminated with pentachlorophenol (PCP) were inoculated with solid substrate cultures
of Lentinula edodes LE2 (“shiitake” mushroom) to simulate monoculture bioremediation treatments and treatments in which the fungus competes with
natural microflora. With monocultures of L. edodes, rates of PCP depletion were rapid for the initial 4 weeks and, although thereafter the rate decreased, 99% biotransformation
was obtained in 10 weeks. In mixed culture, PCP biotransformation by L.␣edodes was markedly slower and only 42% of the PCP was depleted after 10 weeks. Maximal rates of PCP transformation, biomass (ergosterol)
accumulation and oxidative enzymes (phenol oxidase and manganese-peroxidase) production were observed after 2 weeks of incubation.
In monocultures, phenol oxidase activity was 195.5 U g−1 and Mn-peroxidase 138.4 U g−1. In mixed cultures, fungal enzyme activities were markedly lower: 70.33 U g−1 for phenol oxidase and 85.0 g−1 for Mn-peroxidase. Analyses of soil metabolites after 10 weeks revealed that monocultures of L.edodes had eliminated both PCP and pentachloroanisole. Pentachloroanisole, however, was detected in soils with the mixed microflora.
Both dechlorination and mineralisation of the xenobiotic compound were effected by L. edodes LE2.
Received: 7 April 1997 / Accepted: 14 June 1997 相似文献
5.
K.T. Leung Y.J. Chang Y.D. Gan A. Peacock S.J Macnaughton J.R. Stephen R.S. Burkhalter C.A. Flemming D.C. White 《Journal of industrial microbiology & biotechnology》1999,23(4-5):252-260
Sphingomonas spp possess unique abilities to degrade refractory contaminants and are found ubiquitously in the environment. We developed
Sphingomonas genus-specific PCR primers (SPf-190 and SPr1-852) which showed specific amplification of a 627-bp 16S rDNA fragment from
Sphingomonas spp. A PCR assay using these Sphingomonas specific primers was developed to detect Sphingomonas aromaticivorans B0695R in three texturally distinct soil types, showing detection limits between 1.3–2.2 × 103 CFU g−1 dry soil. A sphingolipid extraction protocol was also developed to monitor Sphingomonas populations in soil quantitatively. The detection limit of the assay was 20 pmol g−1 dry soil, equivalent to about 3 × 105 cells g−1 dry soil. Survival of S. aromaticivorans B0695R was monitored in the three different soils by antibiotic selective plate counting, PCR and sphingolipid analysis.
All three approaches showed that the B0695R cells persisted in the low biomass Sequatchie sub-soil at about 3–5 × 107cells g−1 dry soil. In comparison to the plate counting assay, both the PCR and sphingolipid analysis detected a significantly higher
level of B0695R cells in the clay soil and Sequatchie top-soil, indicating the possibility of the presence of viable but non-culturable
B0695R cells in the soils. The combination of PCR and sphingolipid analysis may provide a more realistic estimation of Sphingomonas population in the environment.
Received 17 March 1999/ Accepted in revised form 07 April 1999 相似文献
6.
Stiffler DF Talbot CR 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(7):505-509
Oxygen consumption was measured in five Dermophis mexicanus and averaged (±SEM) 0.047 ± 0.004 ml O2 g−1 h−1. Carbon dioxide production averaged 0.053 ± 0.005 ml CO2 g−1 h−1 in the same five animals 1 week later. This metabolic rate is similar to metabolic rates of other Gymnophionans but lower
than metabolic rates reported for Anurans and Urodeles. Total nitrogen excretion averaged 1.37 μmol N g−1 h−1 which is higher than that found for other amphibians. Of this, 82.5% (1.13 μmol N g−1 h−1) was in the form of urea while 17.5% (0.24 μmol N g−1 h−1) was in the form of NH3 + NH+
4. Such ureotelism is typical of terrestrial amphibians like D. mexicanus. Osmotic water flux averaged 0.0193 ml g−1 h−1 in control (sham injected) animals and was not significantly altered by injection of either arginine vasotocin or mesotocin.
This osmotic flux is similar to osmotic fluxes found for other terrestrial amphibians. The combined data suggest that metabolism
in D. mexicanus is, like most other Gymnophionans, lower than other amphibians. The high rates of nitrogen (especially urea) excretion suggests
that this fossorial animal accumulates urea like other burrowing amphibians.
Accepted: 27 June 2000 相似文献
7.
Yoshida A Nishimura T Kawaguchi H Inui M Yukawa H 《Applied microbiology and biotechnology》2007,74(4):754-760
A three-step biohydrogen production process characterized by efficient anaerobic induction of the formate hydrogen lyase (FHL)
of aerobically grown Escherichia coli was established. Using E. coli strain SR13 (fhlA
++, ΔhycA) at a cell density of 8.2 g/l medium in this process, a specific hydrogen productivity (28.0 ± 5.0 mmol h−1 g−1 dry cell) of one order of magnitude lower than we previously reported was realized after 8 h of anaerobic incubation. The
reduced productivity was attributed partly to the inhibitory effects of accumulated metabolites on FHL induction. To avoid
this inhibition, strain SR14 (SR13 ΔldhA ΔfrdBC) was constructed and used to the effect that specific hydrogen productivity increased 1.3-fold to 37.4 ± 6.9 mmol h−1 g−1. Furthermore, a maximum hydrogen production rate of 144.2 mmol h−1 g−1 was realized when a metabolite excretion system that achieved a dilution rate of 2.0 h−1 was implemented. These results demonstrate that by avoiding anaerobic cultivation altogether, more economical harvesting
of hydrogen-producing cells for use in our biohydrogen process was made possible. 相似文献
8.
Mode of depolymerisation of hemicellulose by various mannanases and xylanases in relation to their ability to bleach softwood pulp 总被引:2,自引:0,他引:2
G. M. Gübitz D. Haltrich B. Latal W. Steiner 《Applied microbiology and biotechnology》1997,47(6):658-662
Endo-mannanases and endo-xylanases cleave different heteromannans and xylans yielding mainly dimers and trimers of the corresponding
sugars as end-products. However, in the early stages of hydrolysis, four purified mannanases and four xylanases from fungal
and bacterial origin, examined in this study, showed a different pattern of released oligomers (determined up to the pentamers).
Furthermore, some of these enzymes showed a preference for cleaving the polysaccharides in the middle of the chain while others
acted more at the end. When the increase in the specific fluidity of mannan and xylan solutions per reducing sugar released
(K
v) was measured against the bleaching effect of the enzymes on softwood kraft pulp, a correlation was found. A xylanase from
Penicillium simplicissimum (K
v = 0.15 l mPa−1s−1g−1) and a mannanase from Sclerotium rolfsii (K
v = 0.12 l mPa−1s−1g−1) applied in a O(QX)P bleaching sequence (O = oxygen delignification, X = treatment with hemicellulolytic enzymes, Q = chelation
of metals, P = treatment with hydrogen peroxide in alkaline solution) gave a high brightness increase of 3.0% and 1.9% ISO
respectively. A less significant brightness increase was obtained with enzymes showing lower K
v values, such as a xylanase from Schizophyllum commune (Kv = 0.051 l mPa−1s−1g−1, 0.2% ISO) and a bacterial mannanase (K
v = 0.061 l mPa−1s−1g−1,0.5% ISO).
Received: 19 December 1996 / Received revision: 20 February 1997 / Accepted: 22 February 1997 相似文献
9.
Kallistova AY Kevbrina MV Nekrasova VK Shnyrev NA Einola JK Kulomaa MS Rintala JA Nozhevnikova AN 《Microbial ecology》2007,54(4):637-645
The enumeration of methanotrophic bacteria in the cover soil of an aged municipal landfill was carried out using (1) fluorescent
in situ hybridization (FISH) with horseradish peroxidase-labeled oligonucleotide probes and tyramide signal amplification, also known
as catalyzed reporter deposition-FISH (CARD-FISH), and (2) most probable number (MPN) method. The number of methanotrophs
was determined in cover soil samples collected during April–November 2003 from a point with low CH4 emission. The number of types I and II methanotrophs obtained by CARD-FISH varied from 15 ± 2 to 56 ± 7 × 108 cells g−1 absolute dry mass (adm) of soil and methanotrophs of type I dominated over type II. The average number of methanotrophs throughout
the cover soil profile was highest during May–September when the cover soil temperature was above 13°C. Methanotrophs accounted
for about 50% of the total bacterial population in the deepest cover soil layer owing to higher availability of substrate
(CH4). A lower number of methanotrophs (7 × 102 to 17 × 105 cells g−1 adm of soil) was determined by the MPN method compared to the CARD-FISH counts, thus confirming previous results that the
MPN method is limited to the estimation of the culturable species that can be grown under the incubation conditions used.
The number of culturable methanotrophs correlated with the methane-oxidizing activity measured in laboratory assays. In comparison
to the incubation-based measurements, the number of methanotrophs determined by CARD-FISH better reflected the actual characteristics
of the environment, such as release and uptake of CH4, temperature, and moisture, and availability of substrates. 相似文献
10.
Ruelas-Inzunza J Vega-Sánchez B Ramos-Osuna M Páez-Osuna F 《Biological trace element research》2011,143(1):231-239
With the aim of knowing levels of Cu, Fe, and Zn in the edible portion of tunas Thunnus albacares and Katsuwonus pelamis, these elements were measured in 73 fish collected in the eastern Pacific. Additionally, trophic transfer (TF) and dietary
mineral intake (DMI) of analyzed metals were determined. The most elevated average concentration of Zn (31.7 μg g−1 dry weight) was found in T. albacares from the Baja California region; in the case of Cu and Fe, highest values (3.86 and 71.0 μg g−1 dry weight) were found in K. pelamis from the offshore waters in the Pacific Ocean. Concentrations of Cu in muscle tissue of both species were significantly (p < 0.05) correlated (negatively) with total length of specimens; levels of Fe in muscle of K. pelamis also showed a negative correlation with total length. None of TFs were above the unit, it implies that there is no biomagnification
of Cu, Fe, and Zn. The DMI of Cu, Fe, and Zn from muscle tissue of analyzed tuna represented less than 13%, 21%, and 8%, respectively,
of the daily requirements for humans. 相似文献
11.
Batch experiments were conducted to evaluate the biodegradation rates of limonene, α-pinene, γ-terpinene, terpinolene and
α-terpineol at 23 °C under aerobic conditions. Biodegradation was demonstrated by the depletion of monoterpene mass, CO2 production and a corresponding increase in biomass. Monoterpene degradation in liquid cultures devoid of soil followed Monod
kinetics. The maximum specific growth rate (μmax) was 0.02 h−1 and 0.06 h−1 and the half-velocity constant (K
s ) varied from 32 mg/l to 3 mg/l for the limonene and α-terpineol respectively. The recovery of monoterpenes by solvent extraction
from autoclaved and azide-amended soil-slurry samples decreased over time and ranged from 69% to 73% for 120 h of incubation
period. Although a significant fraction of monoterpene hydrocarbon could not be extracted, mineralization of these compounds
in the soil-slurry systems took place, as shown by CO2 production. The soil-normalized degradation rates for the hydrocarbon monoterpenes ranged from 0.6 μg g−1 h−1 to 2.1 μg g−1 h−1. A kinetic model – which combined monoterpene biodegradation in the liquid phase and net desorption – was developed and applied
to data obtained from soil-slurry assays.
Received: 10 September 1996 / Received revision: 16 December 1996 / Accepted: 10 January 1997 相似文献
12.
Phosphate Addition and Plant Species Alters Microbial Community Structure in Acidic Upland Grassland Soil 总被引:2,自引:0,他引:2
Agricultural improvement (addition of fertilizers, liming) of seminatural acidic grasslands across Ireland and the UK has
resulted in significant shifts in floristic composition, soil chemistry, and microbial community structure. Although several
factors have been proposed as responsible for driving shifts in microbial communities, the exact causes of such changes are
not well defined. Phosphate was added to grassland microcosms to investigate the effect on fungal and bacterial communities.
Plant species typical of unimproved grasslands (Agrostis capillaris, Festuca ovina) and agriculturally improved grasslands (Lolium perenne) were grown, and phosphate was added 25 days after seed germination, with harvesting after a further 50 days. Phosphate addition
significantly increased root biomass (p < 0.001) and shoot biomass (p < 0.05), soil pH (by 0.1 U), and microbial activity (by 5.33 mg triphenylformazan [TPF] g−1 soil; p < 0.001). A slight decrease (by 0.257 mg biomass-C g−1 soil; p < 0.05) in microbial biomass after phosphate addition was found. The presence of plant species significantly decreased soil
pH (p < 0.05; by up to 0.2 U) and increased microbial activity (by up to 6.02 mg TPF g−1 soil) but had no significant effect on microbial biomass. Microbial communities were profiled using automated ribosomal intergenic
spacer analysis. Multidimensional scaling plots and canonical correspondence analysis revealed that phosphate addition and
its interactions with upland grassland plant species resulted in considerable changes in the fungal and bacterial communities
of upland soil. The fungal community structure was significantly affected by both phosphate (R = 0.948) and plant species (R = 0.857), and the bacterial community structure was also significantly affected by phosphate (R = 0.758) and plant species (R = 0.753). Differences in microbial community structure following P addition were also revealed by similarity percentage analysis.
These data suggest that phosphate application may be an important contributor to microbial community structural change during
agricultural management of upland grasslands. 相似文献
13.
Two responses to elicitins are described in cultivars of radish (Raphanus sativus L.). Type I, exhibited by the cultivar Daikon, is characterised by wilting and desiccation within 24 h of elicitin application
and was previously reported as the sensitive response (S. Kamoun et al. 1993, Mol Plant-Microbe Interact 6: 15–25). At 1 μg
elicitin · g−1 FW radish tissue, symptoms appeared after 8 h, a sensitivity comparable to that shown by tobacco to β elicitins (J.-C. Pernollet
et al., 1993, Physiol Mol Plant Pathol 42: 53–67; S. Kamoun et al., 1993, Mol Plant-Microbe Interact 6: 15–25). Elicitin failed
to induce these symptoms in the cultivar White Icicle, even at 100 μg · g−1 FW of tissue. However, a different response (Type II) with symptoms resembling senescence appeared in White Icicle after
48 h and were fully developed by 72 h. The Type II response was induced at levels of elicitin above 0.3 μg · g−1 FW. Elicitin-treated Daikon leaves held at 100% relative humidity, rather than ambient (50–60%) did not wilt and by 72 h
displayed Type II symptoms. When treated Daikon leaves were removed to ambient humidity at any time during the latent period,
they developed Type I symptoms within 2 h. Although Type I symptoms were suppressed in Daikon at high humidity, there was
no indication that leaf diffusion resistance or plant water conductance were affected. Protoplasts from the cultivar Daikon
responded to elicitin by H+ uptake and K+ release, with maximal response at 300 pM. The response was eliminated by K252a or staurosporine. Daikon protoplasts also
showed transient uptake/secretion of Ca2+ on elicitin addition. Protoplasts from White Icicle gave neither of these responses. Both Daikon and White Icicle phenotypes
could be transferred to progeny of Daikon-White Icicle crosses and in the F2 generation three phenotypes, including a null,
segregated. Only those F2 plants which exhibited the Daikon phenotype produced protoplasts which responded to elicitin.
Received: 13 May 1997 / Accepted: 27 August 1997 相似文献
14.
The objective of this study was the application of the experimental design technique to optimize the conditions for the bioremediation
of contaminated soil by means of composting. A low-cost material such as compost from the Organic Fraction of Municipal Solid
Waste as amendment and pyrene as model pollutant were used. The effect of three factors was considered: pollutant concentration
(0.1–2 g/kg), soil:compost mixing ratio (1:0.5–1:2 w/w) and compost stability measured as respiration index (0.78, 2.69 and
4.52 mg O2 g−1 Organic Matter h−1). Stable compost permitted to achieve an almost complete degradation of pyrene in a short time (10 days). Results indicated
that compost stability is a key parameter to optimize PAHs biodegradation. A factor analysis indicated that the optimal conditions
for bioremediation after 10, 20 and 30 days of process were (1.4, 0.78, 1:1.4), (1.4, 2.18. 1:1.3) and (1.3, 2.18, 1:1.3)
for concentration (g/kg), compost stability (mg O2 g−1 Organic Matter h−1) and soil:compost mixing ratio, respectively. 相似文献
15.
Moro D Bradshaw SD 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(8):538-548
A laboratory study investigated the metabolic physiology, and response to variable periods of water and sodium supply, of
two arid-zone rodents, the house mouse (Mus domesticus) and the Lakeland Downs short-tailed mouse (Leggadina lakedownensis) under controlled conditions. Fractional water fluxes for M. domesticus (24 ± 0.8%) were significantly higher than those of L. lakedownensis (17 ± 0.7%) when provided with food ad libitum. In addition, the amount of water produced by M. domesticus and by L. lakedownensis from metabolic processes (1.3 ± 0.4 ml · day−1 and 1.2 ± 0.4 ml · day−1, respectively) was insufficient to provide them with their minimum water requirement (1.4 ± 0.2 ml · day−1 and 2.0 ± 0.3 ml · day−1, respectively). For both species of rodent, evaporative water loss was lowest at 25 °C, but remained significantly higher
in M. domesticus (1.1 ± 0.1 mg H2O · g−0.122 · h−1) than in L. lakedownensis (0.6 ± 0.1 mg H2O · g−0.122 · h−1). When deprived of drinking water, mice of both species initially lost body mass, but regained it within 18 days following
an increase in the amount of seed consumed. Both species were capable of drinking water of variable saline concentrations
up to 1 mol · l−1, and compensated for the increased sodium in the water by excreting more urine to remove the sodium. Basal metabolic rate
was significantly higher in M. domesticus (3.3 ± 0.2 mg O2 · g−0.75 · h−1) than in L. lakedownensis (2.5 ± 0.1 mg O2 · g−0.75 · h−1). The study provides good evidence that water flux differences between M. domesticus and L. lakedownensis in the field are due to a requirement for more water in M. domesticus to meet their physiological and metabolic demands. Sodium fluxes were lower than those observed in free-ranging mice, whose
relatively high sodium fluxes may reflect sodium associated with available food.
Accepted: 16 August 1999 相似文献
16.
S. Sánchez V. Bravo E. Castro A. J. Moya F. Camacho 《Applied microbiology and biotechnology》1998,50(5):608-611
We have analysed the influence of the initial pH of the medium and the quantity of aeration provided during the batch fermentation
of solutions of d-xylose by the yeast Hansenula polymorpha (34438 ATCC). The initial pH was altered between 3.5 and 6.5 whilst aeration varied between 0.0 and 0.3 vvm. The temperature
was kept at 30 °C during all the experiments. Hansenula polymorpha is known to produce high quantities of xylitol and low quantities of ethanol. The most favourable conditions for the growth
of xylitol turned out to be: an initial pH of between 4.5 and 5.5 and the aeration provided by the stirring vortex alone.
Thus, at an initial pH of 5.5, the maximum specific production rate (μm) was 0.41 h−1, the overall biomass yield (Y
x/s
G) was 0.12 g g−1, the specific d-xylose-consumption rate (q
s
) was 0.075 g g−1 h−1 (for t = 75 h), the specific xylitol-production rate (q
Xy
) was 0.31 g g−1 h−1 (for t = 30 h) and the overall yields of ethanol (Y
E/s
G) and xylitol (Y
Xy/s
G) were 0.017 and 0.61 g g−1 respectively. Both q
s
and q
Xy
decreased during the course of the experiments once the exponential growth phase had finished.
Received: 26 March 1998 / Received revision: 30 June 1998 / Accepted: 2 July 1998 相似文献
17.
Delorme M Thomas DW 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(2):123-132
Nitrogen (N) and energy (E) requirements of the phyllostomid fruit bat, Artibeus jamaicensis, and the pteropodid fruit bat Rousettus aegyptiacus, were measured in adults that were fed on four experimental diets. Mean daily food intake by A. jamaicensis and R. aegyptiacus ranged from 1.1–1.6 times body mass and 0.8–1.0 times body mass, respectively. Dry matter digestibility and metabolizable
E coefficient were high (81.1% and 82.4%, respectively) for A. jamaicensis and (77.5% and 78.0%, respectively) for R. aegyptiacus. Across the four diets, bats maintained constant body mass with mean metabolizable E intakes ranging from 1357.3 kJ · kg−0.75 · day−1 to 1767.3 kJ · kg−0.75 · day−1 for A. jamaicensis and 1282.6–1545.2 kJ · kg−0.75 · day−1 for R. aegyptiacus. Maintenance E costs were high, in the order of 3.6–5.4 times the basal metabolic rate (BMR). It is unlikely that the E intakes
that we observed represent a true measure of maintenance E requirements. All evidence seems to indicate that fruit bats are
E maximizers, ingesting more E than required and regulating storage by adjusting metabolic output. We suggest that true maintenance
E requirements are substantially lower than what we observed. If it follows the eutherian norm of two times the BMR, fruit
bats must necessarily over-ingest E on low-N fruit diet. Dietary E content did affect N metabolism of A. jamaicensis. On respective low- and high-E diets, metabolic fecal N were 0.492 mg N · g−1 and 0.756 mg N · g−1 dry matter intake and endogenous urinary N losses were 163.31 mg N · kg−0.75 · day−1 and 71.54 mg N · kg−0.75 · day−1. A. jamaicensis required 332.3 mg · kg−0.75 · day−1 and 885.3 mg · kg−0.75 · day−1 of total N on high- and low-E diets, respectively, and 213.7 mg · kg−0.75 · day−1 of truly digestible N to achieve N balance. True N digestibilities were low (29% and 49%) for low- and high-E diets, respectively.
For R. aegyptiacus, metabolic fecal N and endogenous urinary N losses were 1.27 mg N · g−1 dry matter intake and 96.0 mg N · kg−0.75 · day−1, respectively, and bats required 529.8 mg · kg−0.75 · day−1 (total N) or 284.0 mg · kg−0.75 · day−1 (truly digestible N). True N digestibility was relatively low (50%). Based on direct comparison, we found no evidence that
R. aegyptiacus exhibits a greater degree of specialization in digestive function and N retention than A. jamaicensis. When combined with results from previous studies, our results indicate that all fruit bats appear to be specialized in their
ability to retain N when faced with low N diet.
Accepted: 24 November 1998 相似文献
18.
Brown CR Everitt VJ Baxter RM 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1999,169(1):19-24
The Hogsback (32°33S 26°57E) and Alice (32°47S 26°50E), Eastern Cape, South Africa, are separated by only 24 km but by 1000 m
in altitude and fall into different climatic regions. Thermal responses (energy expenditure and body temperature) to ambient
temperature were measured in a population of vlei rats (Otomys irroratus) from each of the two localities. We predicted that animals from the colder Hogsback would show differences in their thermal
physiology and morphology consistent with better cold-resistance. Basal metabolic rates of the Hogsback population were slightly,
but not significantly, higher than the Alice population (23.9 J g−1 h−1 vs 22.3 J g−1 h−1), but the slope of the regression between energy expenditure and ambient temperature below the thermal neutral zone was significantly
lower (−1.28 vs −1.60). Body temperature, although quite variable in both populations, was not significantly influenced by
ambient temperature in the Hogsback population, whereas that of Alice animals was. Fur length was longer and relative size
of the ears and tail was smaller in the Hogsback population, which probably accounted for the slightly lower minimum thermal
conductance (1.79 J g−1 h−1 °C−1 vs 1.91 J g−1 h−1 °C−1) in the Hogsback population. Vlei rats from the two sites also have different karyotypes that correlate with climate but
there is insufficient evidence at present to suggest that the different karyotypes and the physiological parameters measured
are adaptive.
Accepted: 15 October 1998 相似文献
19.
Malaysia is the world’s leading producer of palm oil products that contribute US$ 7.5 billion in export revenues. Like any
other agro-based industries, it generates waste that could be utilized as a source of organic nutrients for microalgae culture.
Present investigation delves upon Isochrysis sp. culture in POME modified medium and its utilization as a supplement to Nanochloropsis sp. in rotifer cultures. The culture conditions were optimized using a 1 L photobioreactor (Temp: 23°C, illumination: 180 ∼ 200 μmol
photons m−2s−1, n = 6) and scaled up to 10 L outdoor system (Temp: 26–29°C, illumination: 50 ∼ 180 μmol photons m−2s−1, n = 3). Algal growth rate in photobioreactor (μ = 0.0363 h−1) was 55% higher compared to outdoor culture (μ = 0.0163 h−1), but biomass production was 1.3 times higher in outdoor culture (Outdoor = 91.7 mg m−2d−1; Photobioreactor = 69 mg m−2d−1). Outdoor culture produced 18% higher lipid; while total fatty acids (FA) was not significantly affected by the change in
culture systems as both cultures yield almost similar concentrations of fatty acids per gram of sample (photobioreactor = 119.17 mg
g−1; outdoor culture = 104.50 mg g−1); however, outdoor cultured Isochrysis sp. had 26% more polyunsaturated fatty acids (PUFAs). Rotifers cultured in Isochrysis sp./ Nanochloropsis sp. (1:1, v/v) mixture gave similar growth rate as 100% Nanochoropsis sp. culture (μ = 0.40 d−1), but had 45% higher counts of rotifers with eggs (t = 7, maximum). The Isochrysis sp. culture successfully lowered the nitrate (46%) and orthophosphate (83%) during outdoor culture. 相似文献
20.
I-Y Lee W T Seo G J Kim M K Kim C S Park Y H Park 《Journal of industrial microbiology & biotechnology》1997,18(4):255-259
Maltose and sucrose were efficient carbon sources for the production of curdlan by a strain of Agrobacterium sp. A two-step, fed-batch operation was designed in which biomass was first produced, followed by curdlan production which
was stimulated by nitrogen limitation. There exists an optimal timing for nitrogen limitation for curdlan production in the
two-step, fed-batch operation. Maximum curdlan production (60 g L−1) was obtained from sucrose with a productivity of 0.2 g L−1 h−1 when nitrogen was limited at a cell concentration of 16.0 g L−1. It was also noted that the curdlan yield from sucrose was as high as 0.45 g curdlan g−1 sucrose, and the highest specific production rate was 1.0 g curdlan g−1 cells h−1 right after nitrogen limitation. Of particular importance was the use of molasses as a cheap carbon source to produce curdlan
in the two-step, fed-batch cultivation. As high as 42 g L−1 of curdlan with a yield of 0.35 g curdlan g−1 total sugar was obtained after 120 h of fed-batch cultivation.
Received 20 August 1996/ Accepted in revised form 26 November 1996 相似文献