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1.
S. V. N. Vijayendra N. K. Rastogi T. R. Shamala P. K. Anil Kumar L. Kshama G. J. Joshi 《Indian journal of microbiology》2007,47(2):170-175
Polyhydroxyalkanotes (PHAs), the eco-friendly biopolymers produced by many bacteria, are gaining importance in curtailing
the environmental pollution by replacing the non-biodegradable plastics derived from petroleum. The present study was carried
out to economize the polyhydroxybutyrate (PHB) production by optimizing the fermentation medium using corn steep liquor (CSL),
a by-product of starch processing industry, as a cheap nitrogen source, by Bacillus sp. CFR 256. Response surface methodology (RSM) was used to optimize the fermentation medium using the variables such as
corn steep liquor (5–25 g l−1), Na2HPO4 2H2O (2.2–6.2 g l−1), KH2PO4 (0.5–2.5 g l−1), sucrose (5–55 g l−1) and inoculum concentration (1–25 ml l−1). Central composite rotatable design (CCRD) experiments were carried out to study the complex interactions of the variables.
The optimum conditions for maximum PHB production were (g l−1): CSL-25, Na2HPO4 2H2O-2.2, KH2PO4 − 0.5, sucrose − 55 and inoculum − 10 (ml l−1). After 72 h of fermentation, the amount of PHA produced was 8.20 g l−1 (51.20% of dry cell biomass). It is the first report on optimization of fermentation medium using CSL as a nitrogen source,
for PHB production by Bacillus sp. 相似文献
2.
Effect of protective solutes on leakage from and survival of immobilized Lactobacillus subjected to drying, storage and rehydration 总被引:7,自引:1,他引:6
When lactic acid bacteria are used industrially as fermentation starters it is important to obtain stable and highly viable bacterial cultures. Six strains of Lactobacillus encapsulated in Ca-alginate gel beads were investigated to determine whether dehydration, storage and rehydration may inflict injury. A negative relationship between leakage of lactate dehydrogenase and survival rates was found. Mesophilic lactobacilli showed only negligible leakage compared with thermophilic strains when dehydrated at 30 °C to a level of 0·11 g H2 0 (g dry wt)−1 . The choice of an appropriate suspending medium to be introduced before drying was therefore very important for thermophilic lactobacilli in order to increase the survival rates during dehydration, storage and rehydration. The osmoregulatory solutes tested were adonitol, betaine, glycerol and reconstituted non-fat milk solids (NFMS). Less injury was inflected during dehydration for Lactobacillus helveticus with adonitol, glycerol and NFMS. Survival rates for the strains subjected to immobilization, dehydration, storage and rehydration varied with the strain and the protective solute when fluidized-bed drying was used at 5 °C to a level as high as 0·34 g H2 0 (g dry wt)−1 . Non-fat milk solids gave the best protection for thermophilic lactobacilli, while adonitol and NFMS were best for mesophilic lactobacilli. 相似文献
3.
Spatial and Temporal Variability in Sediment Denitrification Within an Agriculturally Influenced Reservoir 总被引:2,自引:1,他引:1
Reservoirs are intrinsically linked to the rivers that feed them, creating a river–reservoir continuum in which water and
sediment inputs are a function of the surrounding watershed land use. We examined the spatial and temporal variability of
sediment denitrification rates by sampling longitudinally along an agriculturally influenced river–reservoir continuum monthly
for 13 months. Sediment denitrification rates ranged from 0 to 63 μg N2O g ash free dry mass of sediments (AFDM)−1 h−1 or 0–2.7 μg N2O g dry mass of sediments (DM)−1 h−1 at reservoir sites, vs. 0–12 μg N2O gAFDM−1 h−1 or 0–0.27 μg N2O gDM−1 h−1 at riverine sites. Temporally, highest denitrification activity traveled through the reservoir from upper reservoir sites
to the dam, following the load of high nitrate (NO3−-N) water associated with spring runoff. Annual mean sediment denitrification rates at different reservoir sites were consistently
higher than at riverine sites, yet significant relationships among theses sites differed when denitrification rates were expressed
per gDM vs. per gAFDM. There was a significant positive relationship between sediment denitrification rates and NO3−-N concentration up to a threshold of 0.88 mg NO3− -N l−1, above which it appeared NO3−-N was no longer limiting. Denitrification assays were amended seasonally with NO3−-N and an organic carbon source (glucose) to determine nutrient limitation of sediment denitrification. While organic carbon
never limited sediment denitrification, all sites were significantly limited by NO3−-N during fall and winter when ambient NO
3−-N was low. 相似文献
4.
Importance of point sources on regional nitrous oxide fluxes in semi-arid steppe of Inner Mongolia, China 总被引:3,自引:0,他引:3
J. Holst C. Liu Z. Yao N. Brüggemann X. Zheng X. Han K. Butterbach-Bahl 《Plant and Soil》2007,296(1-2):209-226
The aim of the present work was to estimate the contribution of different point and diffuse sources to the regional N2O emission strength of steppe in the Xilin river catchment, Inner Mongolia, People’s Republic of China. Transect studies showed
that the topographic effect on N2O emissions from upland soils was negligible and that upland steppe is only a very weak net source of N2O during the growing season (0.8 ± 0.4 μg N2O–N m−2 h−1). Slightly higher emissions were found for riparian areas (1.8 ± 0.3 μg N2O–N m−2 h−1), which cover ∼4% of the landscape. Even faeces or urine additions stimulated N2O emissions from steppe soils only weakly (<2.5 μg N2O–N m−2 h−1 for a 5 days period). Due to low moisture contents, N2O emissions from dung heaps were also rather low (6.2 ± 0.8 μg N2O–N kg−1 dry matter h−1). In contrast, three orders of magnitude higher N2O emissions were found at sheepfolds (2.45 mg N2O–N m−2 h−1 on average). By calculating N2O emissions on a landscape scale, we show that point sources, and especially sheepfolds, become the dominating regional N2O source during the growing season if stocking rates are >1 sheep ha−1. Our results indicate that the common grazing management in the Xilin river region leads to a translocation of nitrogen from
large source areas towards defined spots. This finding is further supported by measurements of NH3 concentrations at different sites. Since most of the nitrogen accumulated in these hot spots is finally lost through burning
of the dried excrements by the farmers for heating and cooking purposes, the ecosystem faces a significant human perturbation
of regional N cycling, which may contribute to an accelerated degradation of steppe in the Xilin river region.
Responsible Editor: Per Ambus. 相似文献
5.
Jian Wu Henk Schat Rifei Sun Maarten Koornneef Xiaowu Wang Mark G. M. Aarts 《Plant and Soil》2007,291(1-2):167-180
Brassica rapa L. is an important vegetable crop in eastern Asia. The objective of this study was to investigate the genetic variation in
leaf Zn, Fe and Mn accumulation, Zn toxicity tolerance and Zn efficiency in B. rapa. In total 188 accessions were screened for their Zn-related characteristics in hydroponic culture. In experiment 1, mineral
assays on 111 accessions grown under sufficient Zn supply (2 μM ZnSO4) revealed a variation range of 23.2–155.9 μg g−1 dry weight (d. wt.) for Zn, 60.3–350.1 μg g−1 d. wt. for Fe and 20.9–53.3 μg g−1 d. wt. for the Mn concentration in shoot. The investigation of tolerance to excessive Zn (800 μM ZnSO4) on 158 accessions, by using visual toxicity symptom parameters (TSPs), identified different levels of tolerance in B. rapa. In experiment 2, a selected sub-set of accessions from experiment 1 was characterized in more detail for their mineral accumulation
and tolerance to excessive Zn supply (100 μM and 300 μM ZnSO4). In this experiment Zn tolerance (ZT) determined by relative root or shoot dry biomass varied about 2-fold. The same six
accessions were also examined for Zn efficiency, determined as relative growth under 0 μM ZnSO4 compared to 2 μM ZnSO4. Zn efficiency varied 1.8-fold based on shoot dry biomass and 2.6-fold variation based on root dry biomass. Zn accumulation
was strongly correlated with Mn and Fe accumulation both under sufficient and deficient Zn supply. In conclusion, there is
substantial variation for Zn accumulation, Zn toxicity tolerance and Zn efficiency in Brassica rapa L., which would allow selective breeding for these traits. 相似文献
6.
Fungal biomass in the decaying cones ofPinus densiflora was investigated. Leaching, immobilization and mobilization phases were recognized in the decomposition process of cones.
Fungal biomass was estimated by the agar-film technique, using a conversion factor of 0.62 mg dry wt. mm−3 of hyphal volume to biomass and a factor of 2.5 for in-efficiencency of homogenization. The fungal biomass was 4.9±2.1 (mean±S.D.)
mg dry wt. g−1 dry matter in the cones on the tree, 11±6 mg g−1 in the leaching phase, 19±7 mg g−1 in the immobilization phase and 30±15 mg g−1 in the mobilization phase. It significantly increased after cones had lain on the forest floor, and also in the immobilization
phase. The latter result suggests that the fungal biomass contributed to the immobilization of nitrogen in the decomposition
process. The ratio of ergosterol content to fungal biomass in the cones was 2.9–8.8 μg mg−1 dry wt., lying in the range of 2–16 μg mg−1 reported for mycelia. This suggested that the estimate of fungal biomass was reasonable. Reduction in this ratio with the
dry weight loss in the cones suggested that the proportion of relatively active fungal biomass decreased with the progress
of decomposition. 相似文献
7.
Christian Brümmer Nicolas Brüggemann Klaus Butterbach-Bahl Ulrike Falk Jörg Szarzynski Konrad Vielhauer Reiner Wassmann Hans Papen 《Ecosystems》2008,11(4):582-600
In a combined field and laboratory study in the southwest of Burkina Faso, we quantified soil-atmosphere N2O and NO exchange. N2O emissions were measured during two field campaigns throughout the growing seasons 2005 and 2006 at five different experimental
sites, that is, a natural savanna site and four agricultural sites planted with sorghum (n = 2), cotton and peanut. The agricultural fields were not irrigated and not fertilized. Although N2O exchange mostly fluctuated between −2 and 8 μg N2O–N m−2 h−1, peak N2O emissions of 10–35 μg N2O–N m−2 h−1 during the second half of June 2005, and up to 150 μg N2O–N m−2 h−1 at the onset of the rainy season 2006, were observed at the native savanna site, whereas the effect of the first rain event
on N2O emissions at the crop sites was low or even not detectable. Additionally, a fertilizer experiment was conducted at a sorghum
field that was divided into three plots receiving different amounts of N fertilizer (plot A: 140 kg N ha−1; plot B: 52.5 kg N ha−1; plot C: control). During the first 3 weeks after fertilization, only a minor increase in N2O emissions at the two fertilized plots was detected. After 24 days, however, N2O emission rates increased exponentially at plot A up to a mean of 80 μg N2O–N m−2 h−1, whereas daily mean values at plot B reached only 19 μg N2O–N m−2 h−1, whereas N2O flux rates at plot C remained unchanged. The calculated annual N2O emission of the nature reserve site amounted to 0.52 kg N2O–N ha−1 a−1 in 2005 and to 0.67 kg N2O–N ha−1 a−1 in 2006, whereas the calculated average annual N2O release of the crop sites was only 0.19 kg N2O–N ha−1 a−1 and 0.20 kg N2O–N ha−1 a−1 in 2005 and 2006, respectively. In a laboratory study, potential N2O and NO formation under different soil moisture regimes were determined. Single wetting of dry soil to medium soil water
content with subsequent drying caused the highest increase in N2O and NO emissions with maximum fluxes occurring 1 day after wetting. The stimulating effect lasted for 3–4 days. A weaker
stimulation of N2O and NO fluxes was detected during daily wetting of soil to medium water content, whereas no significant stimulating effect
of single or daily wetting to high soil water content (>67% WHCmax) was observed. This study demonstrates that the impact of land-use change in West African savanna on N trace gas emissions
is smaller—with the caveat that there could have been potentially higher N2O and NO emissions during the initial conversion—than the effect of timing and distribution of rainfall and of the likely
increase in nitrogen fertilization in the future. 相似文献
8.
An ecotype of brake fern (Pteris vittata) was assessed for arsenic tolerance and accumulation in its biomass under in vivo and in vitro condition; using soil, and
agar-gelled Murashige and Skoog (MS) medium supplemented with different concentrations of arsenic. The plants were raised
in soil amended with 100–1000 mg arsenic kg−1 soil, and MS medium was supplemented with 10–300 mg arsenic 1−1 medium using Na2HAsO4 · 7H2O. The spores and haploid gametophytic-prothalli were raised in vitro on MS medium supplemented with arsenic. The field plants
showed normal growth and biomass formation in arsenic amended soil, and accumulated 1908–4700 mg arsenic kg−1 dry aerial biomass after 10 weeks of growth. Arsenic toxicity was observed above >200 mg arsenic kg−1 soil. The concentrations of arsenic accumulated in the plant biomass were statistically significant (p < 0.05). Normal plants were developed from spores and gametophyte prothalli on the MS media supplemented with 50–200 mg arsenic
1−1 medium. The in vitro raised plants were tolerant to 300 mg arsenic kg−1 of soil and accumulated up to 3232 mg arsenic kg−1 dry aerial biomass that showed better growth performance, biomass generation and arsenic accumulation in comparison to the
field plants.
The text was submitted by the authors in English. 相似文献
9.
Héctor Guzmán Doan Van-Thuoc Javier Martín Rajni Hatti-Kaul Jorge Quillaguamán 《Applied microbiology and biotechnology》2009,84(6):1069-1077
The paper reports a study involving the use of Halomonas boliviensis, a moderate halophile, for co-production of compatible solute ectoine and biopolyester poly(3-hydroxybutyrate) (PHB) in a
process comprising two fed-batch cultures. Initial investigations on the growth of the organism in a medium with varying NaCl
concentrations showed the highest level of intracellular accumulation of ectoine (0.74 g L−1) at 10–15% (w/v) NaCl, while at 15% (w/v) NaCl, the presence of hydroxyectoine (50 mg L−1) was also noted. On the other hand, the maximum cell dry weight and PHB concentration of 10 and 5.8 g L−1, respectively, were obtained at 5–7.5% (w/v) NaCl. A process comprising two fed-batch cultivations was developed—the first culture aimed at obtaining high cell mass
and the second for achieving high yields of ectoine and PHB. In the first fed-batch culture, H. boliviensis was grown in a medium with 4.5% (w/v) NaCl and sufficient levels of monosodium glutamate, NH4+, and PO43−. In the second fed-batch culture, the NaCl concentration was increased to 7.5% (w/v) to trigger ectoine synthesis, while nitrogen and phosphorus sources were fed only during the first 3 h and then stopped
to favor PHB accumulation. The process resulted in PHB yield of 68.5 wt.% of cell dry weight and volumetric productivity of
about 1 g L−1 h−1 and ectoine concentration, content, and volumetric productivity of 4.3 g L−1, 7.2 wt.%, and 2.8 g L−1 day−1, respectively. At salt concentration of 12.5% (w/v) during the second cultivation, the ectoine content was increased to 17 wt.% and productivity to 3.4 g L−1 day−1. 相似文献
10.
Jirko Holst Chunyan Liu Nicolas Brüggemann Klaus Butterbach-Bahl Xunhua Zheng Yuesi Wang Shenghui Han Zhisheng Yao Jin Yue Xingguo Han 《Ecosystems》2007,10(4):623-634
Gross rates of N mineralization and nitrification, and soil–atmosphere fluxes of N2O, NO and NO2 were measured at differently grazed and ungrazed steppe grassland sites in the Xilin river catchment, Inner Mongolia, P. R.
China, during the 2004 and 2005 growing season. The experimental sites were a plot ungrazed since 1979 (UG79), a plot ungrazed
since 1999 (UG99), a plot moderately grazed in winter (WG), and an overgrazed plot (OG), all in close vicinity to each other.
Gross rates of N mineralization and nitrification determined at in situ soil moisture and soil temperature conditions were
in a range of 0.5–4.1 mg N kg−1 soil dry weight day−1. In 2005, gross N turnover rates were significantly higher at the UG79 plot than at the UG99 plot, which in turn had significantly
higher gross N turnover rates than the WG and OG plots. The WG and the OG plot were not significantly different in gross ammonification
and in gross nitrification rates. Site differences in SOC content, bulk density and texture could explain only less than 15%
of the observed site differences in gross N turnover rates. N2O and NO
x
flux rates were very low during both growing seasons. No significant differences in N trace gas fluxes were found between
plots. Mean values of N2O fluxes varied between 0.39 and 1.60 μg N2O-N m−2 h−1, equivalent to 0.03–0.14 kg N2O-N ha−1 y−1, and were considerably lower than previously reported for the same region. NO
x
flux rates ranged between 0.16 and 0.48 μg NO
x
-N m−2 h−1, equivalent to 0.01–0.04 kg NO
x
-N ha−1 y−1, respectively. N2O fluxes were significantly correlated with soil temperature and soil moisture. The correlations, however, explained only
less than 20% of the flux variance. 相似文献
11.
Increased astaxanthin production by a Phaffia rhodozyma mutant grown on date juice from Yucca fillifera 总被引:1,自引:0,他引:1
J Ramírez M L Nuñez R Valdivia 《Journal of industrial microbiology & biotechnology》2000,24(3):187-190
The wild strain and the astaxanthin-overproducing mutant strain 25–2 of Phaffia rhodozyma were analyzed in order to assess their ability to grow and synthesize astaxanthin in a minimal medium composed of g L−1: KH2PO4 2.0; MgSO4 0.5; CaCl2 0.1; urea 1.0 and supplemented with date juice of Yucca fillifera as a carbon source (yuca medium). The highest astaxanthin production (6170 μg L−1) was obtained at 22.5 g L−1 of reducing sugars. The addition of yeast extract to the yuca medium at concentrations of 0.5–3.0 g L−1 inhibited astaxanthin synthesis. The yuca medium supported a higher production of astaxanthin, 2.5-fold more than that observed
in the YM medium. Journal of Industrial Microbiology & Biotechnology (2000) 24, 187–190.
Received 14 July 1999/ Accepted in revised form 02 December 1999 相似文献
12.
Atmospheric Deposition to the Turkey Lakes Watershed: Temporal Variations and Characteristics 总被引:3,自引:0,他引:3
We investigated the atmospheric concentrations and deposition fluxes of major ions to the Turkey Lakes Watershed (TLW) between
1980 and 1996. During that time, daily SO4
2− concentrations in precipitation decreased markedly, while NO3
−, NH4
+, and H+ concentrations remained roughly constant. It appears that precipitation acidity did not decrease in spite of declining SO4
2− concentrations due to a concurrent and counterbalancing decrease in the concentrations of Ca2+, Mg2+, and K+ in precipitation. The reasons for the decline in base cations are unknown, but this decline is probably related to decreasing
emissions of soil-derived particles from agricultural, industrial, and road sources. A similar situation was seen during the
same period in other parts of Canada, the eastern United States, and Europe. Wet, dry, and total (wet + dry) deposition fluxes
of sulphur (S) and nitrogen (N) were estimated annually for the years 1980–96. The 17-year mean annual total (wet + dry) deposition
of S to the watershed was estimated at 38.5 mmol m−2 y−1 (range 24.3–50.3). Total S deposition decreased by 35% from the early 1980s (1982–84) to the mid-1990s (1994–96), a decline
consistent with the 23% decline in annual SO2 emissions in eastern North America during the same period. In contrast, the annual total (wet + dry) deposition of oxidized
N ranged from 39.8 to 60.4 mmol m−2 y−1, with a 15-year mean of 50.1 mmol m−2 y−1 and a net increase of 10% between the early 1980s (1983–85) and the mid-1990s (1994–96). This is in keeping with a 10% increase
in NOx emissions in eastern North America during the same period. For both S and N (oxidized), wet deposition dominated over dry
deposition as the major mechanism for atmospheric input to the watershed. Annually, wet deposition accounted for approximately
two-thirds of the total atmospheric deposition of both S and N. Dry S deposition was due more to gaseous SO2 deposition (two-thirds of dry S deposition) than to particulate SO4
2− deposition (one-third of dry S deposition). Dry deposition of oxidized N, however, was dominated (95%) by gaseous HNO3 deposition, with minimal input from particulate NO3
− deposition. Compared to several selected watershed/forest sites in Canada, the United States, and Europe, the estimated total
deposition of S and N at the TLW was relatively high during the measurement period.
Received 5 October 1999; accepted 1 March 2001. 相似文献
13.
Artemisinin production by hairy roots of Artemisia annua L. was increased 6-fold to 1.8 μg mg−1 dry wt over 6 days by adding 150 mg chitosan l−1. The increase was dose-dependent. Similar treatment of hairy roots with methyl jasmonate (0.2 mM) or yeast extract (2 mg ml−1) increased artemisinin production to 1.5 and 0.9 μg mg−1 dry wt, respectively. 相似文献
14.
Contribution of plants to N
2
O emissions in soil-winter wheat ecosystem: pot and field experiments 总被引:1,自引:0,他引:1
Outdoor pot and field experiments were conducted to assess the role of growing plants in agricultural ecosystem N2O emissions. N2O emissions from plants were quantified as the difference in soil-crop system N2O emissions before and immediately after cutting plants during the main growth stages in 2001–02 and 2002–03 winter wheat
seasons. Emissions of N2O from plants depended on biomass within the same plant developmental status. Field results indicated that the seasonal contribution
of N2O emissions from plants to ecosystem fluxes averaged 25%, ranging from 10% at wheat tillering to 62% at the heading stage.
The fluxes of N2O emissions from plants varied between 0.3 and 3.9 mg N2O-N m−2 day−1 and its seasonal amount was equivalent to 0.23% of plant N released as N2O. A N2O emission coefficient (N2OE, mg N2O-N g−1 C day−1), defined as N2O-N emission in milligrams from per gram carbon of plant dry matter within a day, was represented by a 5-fold variation ranging
from 0.021 to 0.004 mg N2O-N g C−1 day−1. A linear relationship (y=0.4611x+0.0015, r
2=0.9352, p < 0.001) between N2OE (y) and plant dark respiration rate (x, mg CO2-C g C−1 day−1) suggested that in the absence of photosynthesis, some N2O production in plant N assimilation was associated with plant respiration. Although this study could not show whether N2O was produced or transferred by winter wheat plants, these results indicated an important role for higher plant in N2O exchange. Identifying its potential contribution is critical for understanding agricultural ecosystem N2O sources. 相似文献
15.
Nutrient-enriched water hyacinths were stocked in outdoor tanks and cultured under both high nutrient (HN) and low nutrient
(LN) regimes for 10 months. Seasonal changes in standing crop biomass and morphology of LN water hyacinths were similar to
those of HN water hyacinths, despite a ten-fold between-treatment difference in N availability and a two-fold difference in
average plant N concentrations (1.0 and 2.0% for LN and HN plants, respectively). Tissue N accumulated by the LN plants prior
to stocking helped support standing crop development during the 10 month study.
In both HN and LN treatments, the rate of detritus deposition, or the sloughing of dead plant tissues from the mat, was lower
than the actual detritus production rate because of the retention of dead ‘aerial’ tissues (laminae and petioles) in the floating
mat. The retention of laminae and petioles may serve as a nutrient conservation mechanism, since nutrients released from decomposing
tissues in the mat-water environment may be assimilated by adjacent plants. The average rate of detritus deposition (both
dry matter and N) by LN water hyacinths (1.2 g dry wt. m−2 day−1 and 0.017 g N m−2 day−1) was lower than that of HN plants (3.0 g dry wt. m−2 day−1 and 0.075 g N m−2 day−1) during the study. Low detrital N losses by the water hyacinth probably enhance the survival of this species in aquatic systems
which receive nutrient inputs intermittently. 相似文献
16.
Orlita A Sidwa-Gorycka M Malinski E Czerwicka M Kumirska J Golebiowski M Lojkowska E Stepnowski P 《Biotechnology letters》2008,30(3):541-545
Growth of Ruta graveolens shoots was induced when Bacillus sp. cell lysates were added to the culture medium. Elicitation of coumarin by this lysate was also very effective; the concentrations
of isopimpinelin, xanthotoxin and bergapten increased to 610, 2120 and 1460 μg g−1 dry wt, respectively. It also had a significant effect on the production of psoralen and rutamarin (680 and 380 μg g−1 dry wt) and induced the biosynthesis of chalepin, which was not detected in the control sample, up to 47 μg g−1 dry wt With lysates of the Pectobacterium
atrosepticum, their effect on growth was not so significant and had no effect on the induction of coumarin accumulation. But elicitation
with this lysate was much more effective for inducing the production of furoquinolone alkaloids; the concentrations of γ-fagarine,
skimmianine, dictamnine and kokusaginine rose to 99, 680, 172 and 480 μg g−1 dry wt, respectively. 相似文献
17.
A Bacillus sp., capable of degrading chloroform, was immobilized in calcium alginate. The beads in 20 g alginate l−1 (about 2 × 108 cells/bead) could be re-used nine times for degradation of chloroform at 40 μM. The immobilized cells had a higher range
of tolerance (pH 6.5–9 and 20–41°C) than free cells (pH 7–8.5 and 28–32°C). At 5 g alginate l−1, leakage of the cells from the beads was 0.51 mg dry wt ml−1. This species is the first reported Bacillus that can degrade chloroform as the sole carbon source. 相似文献
18.
Jordi Urmeneta Óscar Alcoba Efrén Razquín Elena Tarroja Antoni Navarrete Ricardo Guerrero 《Current microbiology》1998,37(3):151-155
Photosynthetic and respiratory activities at low light intensities (300 μE m−2 s−1) in the microbial mats of the Ebro Delta were measured by the oxygen exchange method in the laboratory. The response to H2S concentration, a significant factor in the dynamics of that ecosystem, was assessed. Total photosynthesis reached 23.78–28.17
μg O2 cm−2 h−1. Photosynthetic activity was not significantly different at the two temperatures tested. Respiratory activity reached a consumption
of 6.95–8.56 μg O2 cm−2 h−1 at 25°C and 11.42–11.70 μg O2 cm−2 h−1 at 35°C. The Q10 value for respiration was 1.37–1.64. Oxygen production in Microcoleus chthonoplastes, the most abundant cyanobacterium in those microbial mats, was highly resistant to sulfide inhibition. Concentrations less
than 0.02 mM sulfide did not affect the rate of photosynthesis. Concentrations up to 0.1 mM sulfide caused different degrees
of partially reversible inhibition, with a maximum of 67% at 0.78 mM sulfide. Primary production (g C assimilated/m2/year) in those microbial mats was also assessed and compared with data from other ecosystems.
Received: 24 October 1997 / Accepted: 18 December 1997 相似文献
19.
Sipma J Osuna MB Parshina SN Lettinga G Stams AJ Lens PN 《Applied microbiology and biotechnology》2007,76(2):339-347
Desulfotomaculum carboxydivorans, recently isolated from a full-scale anaerobic wastewater treatment facility, is a sulfate reducer capable of hydrogenogenic
growth on carbon monoxide (CO). In the presence of sulfate, the hydrogen formed is used for sulfate reduction. The organism
grows rapidly at 200 kPa CO, pH 7.0, and 55°C, with a generation time of 100 min, producing nearly equimolar amounts of H2 and CO2 from CO and H2O. The high specific CO conversion rates, exceeding 0.8 mol CO (g protein)−1 h−1, makes this bacterium an interesting candidate for a biological alternative of the currently employed chemical catalytic
water–gas shift reaction to purify synthesis gas (contains mainly H2, CO, and CO2). Furthermore, as D. carboxydivorans is capable of hydrogenotrophic sulfate reduction at partial CO pressures exceeding 100 kPa, it is also a good candidate for
biodesulfurization processes using synthesis gas as electron donor at elevated temperatures, e.g., in biological flue gas
desulfurization. Although high maximal specific sulfate reduction rates (32 mmol (g protein)−1 h−1) can be obtained, its sulfide tolerance is rather low and pH dependent, i.e., maximally 9 and 5 mM sulfide at pH 7.2 and
pH 6.5, respectively. 相似文献
20.
Cell suspension cultures of Commiphora wightii, grown in modified MS medium containing 2,4-dichlorophenoxyacetic acid (0.5 mg l−1) and kinetin (0.25 mg l−1), produced ∼5 μg guggulsterone g−1 dry wt. In a 2 l stirred tank bioreactor, the biomass was 5.5 g l−1 and total guggulsterone was 36 μg l−1. 相似文献