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1.
Slight differences in the chemical behavior of germanium (Ge) and silicon (Si) during soil weathering enable Ge/Si ratios
to be used as a tracer of Si pathways. Mineral weathering and biogenic silicon cycling are the primary modifiers of Ge/Si
ratios, but knowledge of the biogenic cycling component is based on relatively few studies. We conducted two sets of greenhouse
experiments in order to better quantify the range and variability in Ge discrimination by plants. Graminoid species commonly
found in North American grassland systems, Agropyron smithii, Schizachyrium scoparium, and Andropogon gerardii were grown under controlled hydroponic environmental conditions. Silicon leaf contents were positively correlated with solution
Si and ambient temperature but not with nutrient solution pH, electrical conductivity, or species. The Ge/Si ratio incorporated
into phytoliths shows a distribution coefficient [(Ge/Si) phytolith/(Ge/Si) solution] of about 0.2 and is remarkably invariant between species, photosynthetic pathway, and solution temperature. Ge seems to
be discriminated against during the uptake and translocation of Si to the opal deposition sites by about a factor of five.
In the second experiment, a wider range of graminoid species ( Agropyron smithii, Bouteloua gracilis, Buchloe dactyloides, Oryzopsis hymenoides, Schizachyrium scoparium and Andropogon gerardii) were grown in two different soil mediums. Plant phytoliths showed a distribution factor of about 0.4 for field grown grasses,
and 0.6 for potting soil grown grasses with no clear trends among the species. Evidence of the direction and degree of biological
Ge discrimination during plant uptake provides a geochemical finger print for plants and improves the utility of Ge/Si ratios
in studies of terrestrial weathering and links between Si cycles in terrestrial and marine systems. 相似文献
2.
In forest ecosystems, the silicon (Si) mass-balance at the watershed scale can be strongly influenced by readily soluble Si components, such as dissolved Si, adsorbed Si, amorphous silica (biogenic and pedogenic opal) and short-range ordered aluminosilicates. The aim of the present study is to (a) identify the components of the readily soluble Si pool in the Cambisol found below three tree species, under homogeneous soil and climate conditions, and (b) study the impact of Si recycling by tree species on the Si pools. We therefore measured the concentrations of Si extracted by Na 2CO 3 (Si alk), oxalate (Si ox) and CaCl 2. The Si alk concentration decreased from the humus layer to 15 cm depth and then slightly increased until a depth of 75 cm. In the humus layer, the Si alk concentration consisted mainly of phytoliths and differed significantly between tree species (expressed as mg SiO 2 g -1): Douglas fir (14.5?±?0.65) > European beech (11.8?±?0.30) > Black pine (5.4?±?0.31). Below 7.5 cm, the Si alk content did not differ significantly between tree species, and the Si ox content, increasing significantly, was mainly comprised of Si adsorbed onto amorphous Fe oxides. These results suggest that (a) tree species can impact the readily soluble Si content in the topsoil, through different rates of Si uptake and phytolith restitution by the vegetation, and (b) the soil’s readily soluble Si pool is mainly comprised of phytoliths and adsorbed Si. Here, the readily soluble Si pool is thus controlled by both the iron dynamics and Si biocycling. 相似文献
3.
Phytoliths are microscopic amorphous silicon dioxide (SiO2.H2O) particles occurring in leaves, internodes, glumes and inflorescence
within all members of the grass family Poaceae. Phytoliths of grasses are of particular interest, as they possess morphological
features which have encouraged many investigators to identify these plants from which fossil phytoliths might have originated.
The present study is a step towards preparing a systematic inventory of grass phytoliths in western tropical Africa. Morphology
and dimensions of phytoliths from 66 species belonging to the tribe Paniceae have been studied. Four shape categories of lobate
phytoliths have been determined in leaf blade spodograms: bilobate, nodular bilobate, polylobate, quadra-lobate. Bilobate
shaped phytoliths are frequently represented in all genera of Paniceae. 13 groups of lobate phytoliths have been distinguished
based on significant morphological criteria like shape of outer margins, shape of the shank and number of lobes. A size category
system of lobate phytolith dimensions (length, width; length and width of shanks) has been developed by the analysis of average,
minimum and maximum values of these dimensions. Application of the size category system results on classifying the major groups
into 25 subgroups. The study proves that size and shape can be used to assign some of the lobate phytoliths to their respective
genera. Some rarely produced lobate shapes like nodular bilobate and polylobate types could be used together on assemblage
basis as markers for definite genera in the tribe Paniceae, e.g. Brachiaria, Panicum, Pennisetum and Setaria. Also, bilobate phytoliths with concave margins have been recorded in five species. Bilobate phytoliths with flattened and
convex margins and quadra-lobate shapes are produced by almost all species which therefore resulted in an inconsistent and
indefinite relationship with the taxa that produce them. The study shows a correlation between width dimensions of bilobate
shapes and their shanks. Greater width dimensions usually connected to thick shanks while short ones are attached to thin
shanks. A spectrum on percentages of species producing each type of lobate phytolith has been designed. It is recommended
that such spectrum should be carried out for all tribes of Poaceae on phyto-geographical basis which might eliminate the effect
of redundancy and multiplicity on the classification of grass phytoliths. 相似文献
4.
Although roots and tubers are dietary staples in many parts of the world, their use is difficult to document archaeo logically
because their organic remains are often poorly preserved in archaeological sedi ments. Here we describe the first diagnostic
phytoliths from the underground storage organs of the important New World agricultural crops manioc or yuca (Manihot esculenta Crantz), arrowroot (Maranta arundinacea L.), and llerén (Calathea allouia [Aubl.] Lindl.) and demonstrate their usefulness for identifying prehistoric root and tuber processing with a study of stone artifacts from
a Valdivia 3 (2800–2400 B.C., calibrated) household at Real Alto, Ecuador. Gelatinized starch (heat-altered) and unaltered
starch from maize (Zea mays L.), arrowroot, and manioc were also found on these stone tools. Our data document early evidence
for manioc in Ecuador’s coastal lowlands. In combination, these phytoliths and starch residues provide evidence that both
raw and cooked foods were processed in this early mixed agricultural economy. 相似文献
5.
A multiproxy analysis of diatoms, chrysophyte cysts, opal phytoliths, and palynomorphs was undertaken in Negra Lagoon, to
decipher Holocene changes in paleobotanical proxies associated with sea-level changes and paleolimnological conditions. Before
the Holocene transgression (7000 yr BP), a terrestrial system was inferred as no aquatic palynomorphs or biogenic silica remains
were recorded. During the sea-level maximum (5200 yr BP), marine/brackish conditions were established as indicated by diatoms,
Chenopodiaceae, and a high content of cysts of Peridinioideae. The catchment consisted of grasslands and wetlands as indicated
by the opal phytolith data. The Holocene transgression was followed by a sea-level decrease, which led to the onset of brackish/freshwater
conditions as inferred from the co-dominance of freshwater and marine/brackish diatoms. This is also supported not only by
the concomitant increase in non-siliceous freshwater microalgae and emergent macrophytes, but also by the presence of Myriophyllum. As sea level continued to decrease during late Holocene, a freshwater system was observed because of the complete separation
from the ocean. Chrysophyte cysts were consistently recorded and brackish diatoms exhibited reduced abundances. The observed
limnological changes are consistent with the alternative states hypothesis of Scheffer’s model ( 1998). That is, the clear water phases were explained because of high macrophyte abundances, low phytoplankton frequencies, high
cyst to diatom ratios, and increase in frequencies of benthic diatom species. Conversely, turbid phases were likely to occur
when low cyst to diatom ratios together with increase in planktonic diatoms and decrease in macrophytes values were detected.
This highlights the importance of this approach to detect long-term changes in shallow lake alternative states. 相似文献
6.
Aims Carbon (C) bio-sequestration within the phytoliths of plants, a mechanism of long-term biogeochemical C sequestration, may play a major role in the global C cycle and climate change. In this study, we explored the potential of C bio-sequestration within phytoliths produced in cultivated rice ( Oryza sativa), a well known silicon accumulator. Methods The rice phytolith extraction was undertaken with microwave digestion procedures and the determination of occluded C in phytoliths was based on dissolution methods of phytolith-Si. Results Chemical analysis indicates that the phytolith-occluded C (PhytOC) contents of the different organs (leaf, stem, sheath and grains) on a dry weight basis in 5 rice cultivars range from 0.4 mg?g ?1 to 2.8 mg?g ?1, and the C content of phytoliths from grains is much lower than that of leaf, stem and sheath. The data also show that the PhytOC content of rice depends on both the content of phytoliths and the efficiency of C occlusion within phytoliths during rice growth. The biogeochemical C sequestration flux of phytoliths in 5 rice cultivars is approximately 0.03–0.13 Mg of carbon dioxide (CO 2) equivalents (Mg-e-CO 2) ha ?1?year ?1. From 1950 to 2010, about 2.37?×?10 8?Mg of CO 2 equivalents might have been sequestrated within the rice phytoliths in China. Assuming a maximum phytoliths C bio-sequestration flux of 0.13 Mg-e-CO 2 ha ?1?year ?1, the global annual potential rate of CO 2 sequestrated in rice phytoliths would approximately be 1.94?×?10 7?Mg. Conclusions Therefore rice crops may play a significant role in long-term C sequestration through the formation of PhytOC. 相似文献
7.
Ge/Si ratios of plant phytoliths have been widely used to trace biogeochemical cycling of Si. However, until recently, information on how much of the Ge and Si transferred from soil to plants is actually stored in phytoliths was lacking. The aim of the present study is to (i) compare the uptake of Si and Ge in three grass species, (ii) localize Ge and Si stored in above-ground plant parts and (iii) evaluate the amounts of Ge and Si sequestrated in phytoliths and plant tissues. Mays (Zea mays), oat (Avena sativa) and reed canary grass (Phalaris arundinacea) were cultivated in the greenhouse on soil and sand to control element supply. Leaf phytoliths were extracted by dry ashing. Total elemental composition of leaves, phytoliths, stems and roots were measured by ICP-MS. For the localization of phytoliths and the determination of Ge and Si within leaf tissues and phytoliths scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and laser ablation inductively coupled mass spectrometry (LA-ICP-MS) was used. The amounts of Si and Ge taken up by the species corresponded with biomass formation and decreased in the order Z. mays > P. arundinacea, A. sativa. Results from LA-ICP-MS revealed that Si was mostly localized in phytoliths, while Ge was disorderly distributed within the leaf tissue. In fact, from the total amounts of Ge accumulated in leaves only 10% was present in phytoliths highlighting the role of organic matter on biogeochemical cycling of Ge and the necessity for using bulk Ge/Si instead of Ge/Si in phytoliths to trace biogeochemical cycling of Si. 相似文献
8.
Particulate biogenic opaline silica is concentrated in cellwalls, intercellular deposits and cell lumina of all portionsof the above-ground plant body of three species of PanicoidGramineae, Andropogon gerardi, Sorgastrum nutans and Panicumvirgatum. Morphologically distinct opal phytoliths form notonly in long cells, short cells, trichomes, stomatal elementsand bulliform cells of the epidermis but also within the cellularstructure of mesophyll, vascular, and sclerenchyma tissues.Roots and rhizomes contain measurable quantities of opalinesilica, and phytoliths develop in epidermal long cells, saddle-shapedshort cells, vascular cells, and intercellular deposits. A morphologicallyunique plate-phytolith, formed by silicification of the innertangential wall of the endodermis, is present in the roots ofall three species. Differences in the quantity of opaline silicaoccur between species and between parts of the same species.The amount of opal deposited in the soil annually by root systemsand above-ground parts is approximately equal in magnitud Andropogon gerardi, Sorgastrum nutans, Panicum virgatum, opaline silica deposition 相似文献
9.
Silica phytoliths are microscopic structures of amorphous hydrated silica ( SiO2· nH 2O) formed by specialized plant cells. Besides their biological roles, physical, chemical, and structural properties of biogenic silica offer a wide spectrum of applications in many fields of industry and technology. Therefore, processes involved in their formation recently become a very interesting topic to study. However, optical transparency and microscopic sizes of silica phytoliths do not allow their visualization and localization by classical light microscopy methods. Their observation thus requires phytolith isolation, technically difficult or lengthy sample preparation procedures, or a work with toxic chemicals. In this paper we are proposing a novel method for visualization of silica phytoliths in Sorghum bicolor root endodermal cells by fluorescence microscopy using alkali mounting solution (pH 12). This method offers an easy and quick preparation of the samples and high contrast imaging. Based on our results we can assume that the proposed fluorescent method for silica phytolith investigation allows observation of multiple samples in relatively short time period and thus might be applicable also for high-throughput screenings. Using this method we found out that after a 3-day cultivation of sorghum plants the minimal needed concentration of sodium silicate, limiting the formation of silica phytoliths in the root endodermis, was 25 µmol dm ?3. The positive correlation of sodium silicate concentration in the substrate with the phytolith diameter was also observed. 相似文献
10.
Maize ( Zea mays L. subsp. mays) has been identified in archaeological contexts by a high proportion of large cross-shaped phytoliths. Given the numerous races of maize, this study was undertaken to determine if differences below the species level could be noted. It was also designed to see if phytoliths differed in various plant parts at various stages of growth. Several races were grown under experimental conditions. No significant differences were found. Furthermore, few phytoliths alleged to be diagnostic of maize were discovered. Systemic studies of maize and analyses of prehistoric cultivation by means of phytoliths seem not to be as promising as some researchers have argued. 相似文献
11.
The proper folding of tubulins prior to their incorporation into microtubules requires a group of conserved proteins called
cofactors A to E. In fission yeast, homologues of these cofactors (at least B, D and E) are necessary for the biogenesis of
microtubules and for cell viability. Here we show that the temperature-sensitive alp11-924 mutant, which is defective in the cofactor B homologue, contains an opal nonsense mutation, which results in the production
of a truncated Alp11 B protein (Alp11 1–118). We isolated a tRNA Trp gene as a multicopy suppressor of this mutation, which rescues alp11-924 by read-through of the nonsense codon. The truncated Alp11 1–118 protein lacks the C-terminal half of Alp11 B, consisting of a central coiled-coil region and the distal CLIP-170 domain found in a number of proteins involved in microtubule
functions. Both of these domains are required for the maintenance of microtubule architecture in vivo. Detailed functional
analyses lead us to propose that Alp11 B comprises three functional domains: the N-terminal half executes the essential function, the central coiled-coil region is
necessary for satisfactory maintenance of cellular α-tubulin levels, and the C-terminal CLIP-170 domain is required for efficient
binding to α-tubulin.
Received: 29 November 1999 / Accepted: 18 April 2000 相似文献
12.
The photoluminescence (PL) characteristics of CdSe quantum dots (QDs) infiltrated into inverse opal SiO 2 photonic crystals (PCs) are systemically studied. The special porous structure of inverse opal PCs enhanced the thermal exchange rate between the CdSe QDs and their surrounding environment. Finally, inverse opal SiO 2 PCs suppressed the nonlinear PL enhancement of CdSe QDs in PCs excited by a continuum laser and effectively modulated the PL characteristics of CdSe QDs in PCs at high temperatures in comparison with that of CdSe QDs out of PCs. The final results are of benefit in further understanding the role of inverse opal PCs on the PL characteristics of QDs. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
13.
Aim This study calibrates the relationship between phytolith indices, modern vegetation structure, and a climate parameter (AET/PET, i.e. the ratio of annual actual evapotranspiration to annual potential evapotranspiration), in order to present new proxies for long‐term Quaternary climate and vegetation changes, and model/data comparisons. Location Sixty‐two modern soil surface samples from West Africa (Mauritania and Senegal), collected along a latitudinal transect across four bioclimatic zones, were analysed. Methods Two phytolith indices are defined as normalized data: (1) humidity‐aridity index [Iph (%) = saddle vs. cross + dumbbell + saddle], and (2) water stress index [fan‐shaped index (Fs) (%) = fan‐shaped vs. sum of characteristic phytoliths]. Vegetation structures are delimited according to Iph and Fs boundaries. Bootstrapped regression methods are used for evaluating the strength of the relationship between the two phytolith indices and AET/PET. Additional modern phytolith assemblages, from Mexico, Cameroon and Tanzania are extracted in order to test the calibration established from the West African samples. Accuracy of the AET/PET phytolith proxy is compared with equivalent pollen proxy from the same area. Results Characterization of the grass cover is accurately made through Iph. A boundary of 20 ± 1.4% discriminates tall grass savannas from short grass savannas. Water stress and transpiration experienced by the grass cover can be estimated through Fs. AET/PET is accurately estimated from phytoliths by a transfer function: AET/PET = ?0.605 Fs ? 0.387 Iph + 0.272 (Iph – 20) 2 ( r = 0.80 ± 0.04) in the application domain (AET/PET ranging from 0.1 ± 0.04 to 0.45 ± 0.04). Phytolith and pollen estimate with similar precision ( rpollen = 0.84 ± 0.04) the AET/PET in the studied area. Conclusions This study demonstrates that we can rely on the phytolith indices Iph and Fs to distinguish the different grasslands in tropical areas. Moreover, a new phytolith proxy of AET/PET, linked to water availability, is presented. We suggest from these results that combining phytolith and pollen proxies of AET/PET would help to constrain this climate parameter better, especially when phytolith assemblages are dominated by Panicoideae and Chloridoideae C 4‐grass phytoliths, are devoid of Pooideae C 3‐grass phytoliths, and occur with a few tropical ligneous woody dicotyledon phytoliths. As AET/PET is a bioclimatic indicator commonly used in vegetation models, such a combination would help to make model/data comparisons more efficient. 相似文献
14.
The search for orally effective drugs for the treatment of iron overload disorders is an important goal in improving the health
of patients suffering diseases such as β-thalassemia major. Herein, we report the syntheses and characterization of some new
members of a series of N-aroyl- N′-picolinoyl hydrazine chelators (the H 2IPH analogs). Both 1:1 and 1:2 Fe III:L complexes were isolated and the crystal structures of Fe(HPPH)Cl 2, Fe(4BBPH)Cl 2, Fe(HAPH)(APH) and Fe(H3BBPH)(3BBPH) were determined (H 2PPH= N, N′-bis-picolinoyl hydrazine; H 2APH= N-4-aminobenzoyl- N′-picolinoyl hydrazine, H 23BBPH= N-3-bromobenzoyl- N′-picolinoylhydrazine and H 24BBPH= N-(4-bromobenzoyl)- N′-(picolinoyl)hydrazine). In each case, a tridentate N, N, O coordination mode of each chelator with Fe was observed. The Fe III complexes of these ligands have been synthesized and their structural, spectroscopic and electrochemical characterization
are reported. Five of these new chelators, namely H 2BPH ( N-(benzoyl)- N′-(picolinoyl)hydrazine), H 2TPH ( N-(2-thienyl)- N′-(picolinoyl)-hydrazine), H 2PPH, H 23BBPH and H 24BBPH, showed high efficacy at mobilizing 59Fe from cells and inhibiting 59Fe uptake from the serum Fe transport protein, transferrin (Tf). Indeed, their activity was much greater than that found for
the chelator in current clinical use, desferrioxamine (DFO), and similar to that observed for the orally active chelator,
pyridoxal isonicotinoyl hydrazone (H 2PIH). The ability of the chelators to inhibit 59Fe uptake could not be accounted for by direct chelation of 59Fe from 59Fe–Tf. The most effective chelators also showed low antiproliferative activity which was similar to or less than that observed
with DFO, which is important in terms of their potential use as agents to treat Fe-overload disease. 相似文献
15.
Background and aims Plants absorb and carry soluble silica from soils and then deposit SiO 2?·?nH 2O within themselves producing amorphous silica particles known as phytoliths. Trace amount of organic carbon is occluded during phytolith formation referred to as phytolith-occluded carbon (PhytOC). This carbon fraction has been recognized as an important way of carbon biosequestration. Previous studies have investigated the PhytOC contents of many crop plants and their contribution to global carbon sink. However, the PhytOC in soil is less focused. In this study, we investigated the distribution of soil PhytOC in the Chinese Loess Plateau (CLP). Methods Twenty-six soil profiles were collected in the Chinese Loess Plateau. A wet oxidation method was used for phytolith extraction. Occluded carbon was determined by element analyzer. Results Our results showed that the soil PhytOC density (SPCD) ranged from 0.757 to 23.110 g/m 2 among different soil profiles. The SPCD of profiles in the Southern CLP was generally higher than that in the Northern CLP. It was estimated that 5.35 Mt of PhytOC was stored in the upper soil of the CLP. We also estimated the annual phytolith flux into the Yellow River from the CLP by soil erosion and about 2.5 Mt of phytoliths eroded and transported into rivers per year. Conclusions Our study indicated that PhytOC was one of the potential biosequestration way and phytoliths had an important influence on biogeochemical cycle of silica. Our results suggested that the soil PhytOC was mainly influenced by different plant communities. 相似文献
16.
Escherichia coli strains MC4100 (parent) and a mutant strain derived from this (IC007) were evaluated for their ability to produce H 2 and organic acids (OAs) via fermentation. Following growth, each strain was coated with Pd(0) via bioreduction of Pd(II).
Dried, sintered Pd-biomaterials (‘Bio-Pd’) were tested as anodes in a proton exchange membrane (PEM) fuel cell for their ability
to generate electricity from H 2. Both strains produced hydrogen and OAs but ‘palladised’ cells of strain IC007 (Bio-Pd IC007) produced ~threefold more power as compared to Bio-Pd MC4100 (56 and 18 mW respectively). The power output used, for comparison, commercial Pd(0) powder and Bio-Pd made from Desulfovibrio desulfuricans, was ~100 mW. The implications of these findings for an integrated energy generating process are discussed. 相似文献
17.
A genetic model is proposed for the analysis of embryo and endosperm effects as well as GE interaction effects. An investigation
of three malting quality traits in grains of seven parents and their F 2s was undertaken in a half-diallel cross of barley ( Hordeum distichum L.) over 2 years. The results indicated that the malt Kolbach index (KI), alpha-amylase activity (αAA) and wort soluble nitrogen
(Wort-N) are controlled by both embryo genetic effects and endosperm genetic effects. Variance of the endosperm additive effects
was obviously larger than that of the embryo additive effects. In the contribution of the embryo genetic effects to variation
in malt αAA and Wort-N, the dominance effects were considerably larger than the additive effects. The endosperm dominance
effects constituted a major part of the total genetic effect on the KI. Significant endosperm GE interactions were also detected
in the malt traits concerned. Endosperm general heritability ( h
2
e
) tended to be larger than interaction heritability ( h
2
oE
or h
2
eE
) for all the traits. Endosperm heterosis was observed to be significantly positive for αAA but negative for Wort-N in the
F 2 seed generation. Prediction of main gene effects for seven parents showed that ‘Ganmu 2’ and ‘Supi1’ were suitable parental
varieties for malt αAA and Wort-N improvement. Our genetic model for malting quality traits and its application in breeding
are discussed.
Received: 5 August 1997 / Accepted: 11 September 1997 相似文献
18.
A mixture of rProROL having the full-length prosequence (97 amino acids) for a recombinant lipase of Rhizopus oryzae (rROL) and r28ROL having 28 amino acids of the same prosequence has been produced as active forms by Saccharomyces cerevisiae [Takahashi et al. (1998) J Ferment Bioeng 86: 164–168]. However, the separation of rProROL and r28ROL has not been successful
due to their identical behavior on column chromatographs, presumably because of the similarity of their surface properties.
The independent production of two different molecular forms of rROL was carried out using KEX2-engineered strains of S. cerevisiae, since r28ROL was predicted to be a product from rProROL by a Kex2-like protease. rProROL was successfully obtained by expression
of the ROL gene in the S. cerevisiae kex2 strain in which the KEX2 gene encoding Kex2p was disrupted, while r28ROL was obtained by co-expression of the gene ( KEX2Δ613) encoding the soluble form of the C-terminal truncated Kex2 protease (sKex2p). The specific lipase activities of rProROL
and r28ROL were 92.9 U/mg and 140 U/mg, respectively. rProROL was stable at pH 2.2–8.0, and showed the optimal reaction temperature
to be 30–35 °C with a T
50 of 55 °C ( T
50 is the temperature resulting in 50% loss of activity). The values for r28ROL were pH 3.0–10.0, 25–30 °C, and 40 °C, respectively.
rProROL was an N-linked glycosylated form, but r28ROL was not. The enhanced thermostability of rProROL did not seem to be
due to the N-linked glycosylation, as judged by the results of the Endo H treatment. rProROL had the highest esterase activity
toward p-nitrophenyl laurate (C 12), whereas r28ROL had the highest esterase activity toward p-nitrophenyl caprylate (C 8) and stearate (C 18). These results suggest that the distinct properties of these two forms of lipase are caused by the different length of the
ROL prosequence.
Received: 26 January 1999 / Received last revision: 24 May 1999 / Accepted: 4 June 1999 相似文献
19.
Tetrachloroethene (C 2Cl 4) dechlorination kinetics in upflow anaerobic sludge blanket (UASB) reactors was determined after introducing de novo activities into the granular sludge. These activities were introduced by immobilizing Dehalospirillum multivorans in a test reactor containing unsterile granular sludge, and in a reference reactor, R1, containing sterile granular sludge.
A second reference reactor, R2, contained only unsterile granular sludge and served as a control. The kinetic experiments
were performed by pulsing the reactors with C 2Cl 4 in a recirculating batch mode. Formate and acetate were added as electron donor and carbon source. Both reactors inoculated
with D. multivorans dechlorinated C 2Cl 4 to an equimolar amount of C 2H 2Cl 2 with only traces of C 2HCl 3 in the effluent. In the control reactor, C 2HCl 3 accumulated before C 2H 2Cl 2 was produced. A computer simulation program (AQUASIM) was used to estimate the kinetic parameters. The half-saturation constants
( K
s) for C 2Cl 4 and C 2HCl 3 were almost equal in the reactors containing D.␣multivorans (17 μM and 18 μM for C 2Cl 4; 26 μM and 28 μM for C 2HCl 3), indicating no influence of sludge bacteria on the affinity of D. multivorans for C 2Cl 4 and C 2HCl 3. The maximum dechlorination rates ( k
m
X
B) were about twice as high in the reactor containing D.␣multivorans immobilized in sterile sludge (11 mmol C 2Cl 4 l sludge −1 day −1 and 27 mmol C 2HCl 3 l sludge −1 day −1) than in the test reactor (4.4 mmol C 2Cl 4 l sludge −1 day −1 and 15 mmol C 2HCl 3 l sludge −1 day −1). Compared to other C 2Cl 4-degrading systems, the dechlorination rates of the inoculated reactors and their affinities for C 2Cl 4 and C 2HCl 3 were high. Therefore, introduction of de novo activity is promising for the use of anaerobic reactors to bioremediate C 2Cl 4-polluted water.
Received: 5 November 1998 / Received revision: 25 January 1999 / Accepted: 31 January 1999 相似文献
20.
Olive mill wastewater (OMW) samples from two traditional varieties (Peranzana and Ogliarola Garganica) of Apulian region (southern
Italy) and produced through continuous and traditional methods were microbiologically and chemically examined; thus, 104 yeasts
were isolated and selected for further analyses. The strains were identified as Candida boidinii, Pichia holstii, Pichia membranifaciens, and Saccharomyces cerevisiae and analyzed to assess their suitability to metabolize phenols. Based on phenol metabolism, 27 strains were selected and
inoculated into OMW aliquots to determine their ability to reduce phenols in vivo; then, five strains (identified with the
codes 682— C. boidinii and 625, 642, 647, and 941— P. holstii) were used as a cocktail in wastewaters for a final validation step. In this last experiment, the effects of the temperature
(10–30°C) and (NH 4) 2SO 4 (0.0–6.0 g l −1) were studied through a central composite design approach, and the results highlighted that the cocktail was able to reduce
phenols by 40% at 10°C with 6.0 g l −1 of (NH 4) 2SO 4 added. 相似文献
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