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1.
Zhong-Yu You Zhi-Qiang Liu Yu-Guo Zheng 《Applied microbiology and biotechnology》2014,98(4):1671-1680
A carbonyl reductase (SCR2) gene was synthesized and expressed in Escherichia coli after codon optimization to investigate its biochemical properties and application in biosynthesis of ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE), which is an important chiral synthon for the side chain of cholesterol-lowering drug. The recombinant SCR2 was purified and characterized using ethyl 4-chloro-3-oxobutanoate (COBE) as substrate. The specific activity of purified enzyme was 11.9 U mg?1. The optimum temperature and pH for enzyme activity were 45 °C and pH 6.0, respectively. The half-lives of recombinant SCR2 were 16.5, 7.7, 2.2, 0.41, and 0.05 h at 30 °C, 35 °C, 40 °C, 45 °C, and 50 °C, respectively, and it was highly stable in acidic environment. This SCR2 displayed a relatively narrow substrate specificity. The apparent K m and V max values of purified enzyme for COBE are 6.4 mM and 63.3 μmol min?1 mg?1, respectively. The biocatalytic process for the synthesis of (S)-CHBE was constructed by this SCR2 in an aqueous–organic solvent system with a substrate fed-batch strategy. At the final COBE concentration of 1 M, (S)-CHBE with yield of 95.3 % and e.e. of 99 % was obtained after 6-h reaction. In this process, the space-time yield per gram of biomass (dry cell weight, DCW) and turnover number of NADP+ to (S)-CHBE were 26.5 mmol L?1 h?1 g?1 DCW and 40,000 mol/mol, respectively, which were the highest values as compared with other works. 相似文献
2.
Soil nitrous oxide emissions from a typical semiarid temperate steppe in inner Mongolia: effects of mineral nitrogen fertilizer levels and forms 总被引:1,自引:0,他引:1
Nitrous oxide (N2O) emissions can be significantly affected by the amounts and forms of nitrogen (N) available in soils, but the effect is highly dependent on local climate and soil conditions in specific ecosystem. To improve our understanding of the response of N2O emissions to different N sources of fertilizer in a typical semiarid temperate steppe in Inner Mongolia, a 2-year field experiment was conducted to investigate the effects of high, medium and low N fertilizer levels (HN: 200 kg N?ha-1y-1, MN: 100 kg N ha-1y-1, and LN: 50 kg N ha-1y-1) respectively and N fertilizer forms (CAN: calcium ammonium nitrate, AS: ammonium sulphate and NS: sodium nitrate) on N2O emissions using static closed chamber method. Our data showed that peak N2O fluxes induced by N treatments were concentrated in short periods (2 to 3 weeks) after fertilization in summer and in soil thawing periods in early spring; there were similarly low N2O fluxes from all treatments in the remaining seasons of the year. The three N levels increased annual N2O emissions significantly (P?<?0.05) in the order of MN > HN > LN compared with the CK (control) treatment in year 1; in year 2, the elevation of annual N2O emissions was significant (P?<?0.05) by HN and MN treatments but was insignificant by LN treatments (P?>?0.05). The three N forms also had strong effects on N2O emissions. Significantly (P?<?0.05) higher annual N2O emissions were observed in the soils of CAN and AS fertilizer treatments than in the soils of NS fertilizer treatments in both measured years, but the difference between CAN and AS was not significant (P?>?0.05). Annual N2O emission factors (EF) ranged from 0.060 to 0.298% for different N fertilizer treatments in the two observed years, with an overall EF value of 0.125%. The EF values were by far less than the mean default EF proposed by the Intergovernmental Panel on Climate Change (IPCC). 相似文献
3.
Glucosamine-6-phosphate (GlcN-6-P) synthase from Saccharomyces cerevisiae was expressed in Pichia pastoris SMD1168 GIVING maximum activity of 96 U ml?1 for the enzyme in the culture medium. By SDS-PAGE, the enzyme, a glycosylated protein, had an apparent molecular mass of 90 kDa. The enzyme was purified by gel exclusion chromatography to near homogeneity, with a 90 % yield and its properties were characterized. Optimal activities were at pH 5.5 and 55 °C, respectively, at which the highest specific activity was 6.8 U mg protein ?1. The enzyme was stable from pH 4.5 to 5.5 and from 45 to 60 °C. The Km and Vmax of the GlcN-6-P synthase towards d-fructose 6-phosphate were 2.8 mM and 6.9 μmol min?1 mg?1, respectively. 相似文献
4.
Enhanced biological denitrification of high concentration of nitrite with supplementary carbon source 总被引:3,自引:0,他引:3
Nitrite accumulates during biological denitrification processes when carbon sources are insufficient. Acetate, methanol, and ethanol were investigated as supplementary carbon sources in the nitrite denitrification process using biogranules. Without supplementary external electron donors (control), the biogranules degraded 200 mg l?1 nitrite at a rate of 0.27 mg NO2–N g?1?VSS h?1. Notably, 1,500 mg l?1 acetate and 700 mg l?1 methanol or ethanol enhanced denitrification rates for 200 mg l?1 nitrite at 2.07, 1.20, and 1.60 mg NO2–N g?1?VSS h?1, respectively; these rates were significantly higher than that of the control. The sodium dodecyl sulfate polyacrylamide gel electrophoresis of the nitrite reductase (NiR) enzyme identified three prominent bands with molecular weights of 37–41 kDa. A linear correlation existed between incremental denitrification rates and incremental activity of the NiR enzyme. The NiR enzyme activity was enhanced by the supplementary carbon sources, thereby increasing the nitrite denitrification rate. The capacity of supplementary carbon source on enhancing NiR enzyme activity follows: methanol?>?acetate?>?ethanol on molar basis or acetate?>?ethanol?>?methanol on an added weight basis. 相似文献
5.
Modelling of the carbon dynamics in arable soils is complex and the accuracy of the predictions is unknown before the model is applied to each specific site. Objectives were (i) to test the accuracy of predictions of the carbon dynamics using the Rothamsted Carbon (RothC) Model in a field trial in Quzhou, North China Plain, using different methods for initialization and estimation of carbon input into the soil and (ii) to test the applicability of the RothC model for plots with either conventional tillage (CT) or no-tillage (NT) systems. A field trial was conducted with applications of differing amounts of N (0, 112 or 187 kg N ha?1 year?1), P (0, 75 or 150 kg P2O5 ha?1 year?1) and wheat straw (0, 2.25 or 4.5 t DM ha?1 year?1) in differing combinations with either CT or NT for 18 years. CT and NT affected stocks of soil organic carbon (SOC) similarly. Carbon inputs from crops were either estimated from published regression functions that relate C inputs to crop yield including rhizodeposition (models 1 and 2) or published root:aboveground biomass ratios (model 3). Model 1, which was not calibrated to the site conditions, was successful in predicting the carbon dynamics in seven out of nine treatments (model efficiencies EF ranged from 0.28 to 0.87), whereas for two treatments, EF (?0.35 and?2.3) indicated an unsuccessful prediction. The prediction of the C dynamics in NT experiments using model 1 was generally successful, but this may have been due to the fact that NT did not have a specific effect on SOC stocks for this trial. Model 2, which was the same as model 1 except for an optimization of the stock of inert organic matter using one treatment, predicted SOC stocks in the remaining eight treatments overall better than model 1. Model 3 was less successful than models 1 and 2 in all treatments (?19 ≤ EF ≤ 0.56). The results indicate that the RothC model may successfully predict C dynamics—for the site studied even without prior calibration as in model 1—, but care should be taken in choosing an appropriate approach for estimating C inputs into the soil. 相似文献
6.
Siddhartha Kumar Mishra Neelam Singh Sangwan Rajender Singh Sangwan 《Journal of plant biochemistry and biotechnology.》2014,23(4):379-388
A highly abundant β-glucosidase from petals of Silybum marianum has been purified and characterized for its physico-kinetic properties. The 135 kDa enzyme was a homodimer with subunit molecular mass of 67.6 kDa. The characteristic catalytic properties of the enzyme included acidic pH optimum (5.5), meso-thermostability, and β-linked substrate specificity with preference for gluco-conjugate but a marked (>50 %) activity with D-fuco-conjugates and considerable (~16 %) activity towards D-galacto-conjugates. The enzyme showed high affinity for p-nitrophenyl glucoside (pNPG) with Km and Vmax values of 0.25 mM and 5.35 μkat.mg?1 enzyme protein. Thus, the enzyme had a very high (292,000 M?1.s?1) catalytic efficiency (Kcat/Km). Thermal catalytic optimum of enzyme was 40 °C with activation energy value 8.26 kCal.Mol?1. The enzyme showed significant insensitivity to D-gluconic acid lactone inhibition (57 % at 5 mM) with an apparent Ki 3.8 mM. The transglucosylating ability of enzyme was noticed for glucosylation of geraniol and withaferin-A with pNPG as glucosyl donor but cellobiose did not serve as the glycosyl donor. Partial proteomics of the enzyme revealed two peptide fragment sequences, VTPSNEVH and KRSEESNF. These motifs showed significant matching/sequence conservation with some other glycohydrolases. The novelties of purified enzyme hold potential to expand a library of catalytically characteristic members of the hydrolase family from plants for use in biotransformation applications. 相似文献
7.
A solventogenic strain of Clostridium sp. BOH3 produces extracellular α-amylase (7.15 U/mg protein) in reinforced clostridial medium supplemented with sugarcane bagasse hydrolysate (1 % w/v) and a small amount of starch (0.1 % w/v), which is essential for the expression of α-amylase. In the presence of α-amylase, BOH3 utilizes starch directly without any pretreatment and produces butanol almost equivalent (~90 %) to the production of butanol from glucose. α-Amylase can be purified from culture supernatant by using one-step weak anion exchange chromatography with a yield of 43 %. In peptide fingerprinting analysis, this enzyme shows homology with α-amylase produced by Clostridium acetobutylicum ATCC824. However, the molecular weight is 54 kDa, which is smaller than α-amylase of ATCC824 (84 kDa). This enzyme has optimum temperature at 45–50 °C and optimum pH at 4.5–5.5. Under this condition, the enzyme activity is 91.32 U/mg protein, and its K m and V max values are 1.71?±?0.02 mg/ml and 96.13?±?0.15 μmol/min/mg protein, respectively. Activity of this α-amylase can be enhanced (>1.5 times) by addition of Ca2+ and Co2+ and its activity can be maintained at an acidic pH (pH 3–5) for about 24 h. These unique characteristics suggest that this enzyme can be used for saccharification of starch for production of biofuel in one pot. 相似文献
8.
M. Oviya V. Sukumaran Sib Sankar Giri 《World journal of microbiology & biotechnology》2013,29(10):1813-1820
The present investigation entails the immobilisation and characterisation of Escherichia coli MO1-derived carbonic anhydrase (CA) and its influence on the transformation of CO2 to CaCO3. CA was purified from MO1 using a combination of Sephadex G-75 and DEAE cellulose column chromatography, resulting in 4.64-fold purification. The purified CA was immobilised in chitosan-alginate polyelectrolyte complex (C-A PEC) with an immobilisation potential of 94.5 %. Both the immobilised and free forms of the enzyme were most active and stable at pH 8.2 and at 37 °C. The K m and V max of the immobilised enzyme were found to be 19.12 mM and 416.66 μmol min?1 mg?1, respectively; whereas, the K m and V max of free enzyme were 18.26 mM and 434.78 μmol min?1 mg?1, respectively. The presence of metal ions such as Cu2+, Fe2+, and Mg2+ stimulated the enzyme activity. Immobilised CA showed higher storage stability and maintained its catalytic efficiency after repeated operational cycles. Furthermore, both forms of the enzyme were tested for targeted application of the carbonation reaction to convert CO2 to CaCO3. The amounts of CaCO3 precipitated over free and immobilised CA were 267 and 253 mg/mg of enzyme, respectively. The results of this study show that immobilised CA in chitosan-alginate beads can be useful for CO2 sequestration by the biomimetic route. 相似文献
9.
β-Glucosidase from Thermus thermophilus has specific hydrolytic activity for the outer glucose at the C-20 position in protopanaxadiol-type ginsenosides without hydrolysis of the inner glucose. The hydrolytic activity of the enzyme for gypenoside XVII was optimal at pH 6.5 and 90 °C, with a half-life of 1 h with 3 g enzyme l?1 and 4 g gypenoside XVII l?1. Under the optimized conditions, the enzyme converted the substrate gypenoside XVII to ginsenoside F2 with a molar yield of 100 % and a productivity of 4 g l?1 h?1. The conversion yield and productivity of ginsenoside F2 are the highest reported thus far among enzymatic transformations. 相似文献
10.
The persistent edaphic stress on microbial succession due to dynamic changes during composting was explored for selection of multi-stress tolerant microbe(s) desirable for ethanol production. A total of 23 strains were isolated from mango compost using four successive enrichments in YP broth (g l?1): glucose, 100; 150; 250 with ethanol (40) and cycloheximide (0.4) at 40 °C, pH 6.0. Based on multi-gene ribotyping, 14 yeasts (61 %) of Saccharomycetaceae, 2 filamentous fungi (8.6 %) and 7 bacteria (30.4 %) were obtained. Phenetic and phylogenetic analysis of the 14 yeasts revealed 64.3 % tolerant to 500 g l?1 glucose, growth at 45 °C and resemblance to Candida sp. (14.3 %), Kluyveromyces marxianus (35.7 %), Pichia kudriavzevii (21.4 %) and Saccharomyces cerevisiae (28.6 %). Assessment of the 14 yeasts in glucose fermentation medium (pH 4.5 at 40 °C) showed ethanol productivity of ≥92 % by 12 yeasts with theoretical yields of 90–97 %. Fermentation of molasses (150 g l?1 glucose equivalent) by P. kudriavzevii D1C at 40 °C resulted in 73.70 ± 0.02 g l?1 ethanol and productivity of 4.91 ± 0.01 g l?1 h?1. Assessment of P. kudriavzevii D1C revealed multi-stress tolerance towards 5-hydroxymethyl furfural, ethanol (20 %, v/v), high gravity and H2O2 (0.3 M) indicating suitability for ethanol production using high gravity molasses and pre-treated lignocellulosic biomass fermentation. 相似文献
11.
Zhong-Yu You Zhi-Qiang Liu Yu-Guo Zheng Yin-Chu Shen 《Journal of industrial microbiology & biotechnology》2013,40(1):29-39
A codon-optimized 2-deoxyribose-5-phosphate aldolase (DERA) gene was newly synthesized and expressed in Escherichia coli to investigate its biochemical properties and applications in synthesis of statin intermediates. The expressed DERA was purified and characterized using 2-deoxyribose-5-phosphate as the substrate. The specific activity of recombinant DERA was 1.8 U/mg. The optimum pH and temperature for DERA activity were pH 7.0 and 35 °C, respectively. The recombinant DERA was stable at pH 4.0–7.0 and at temperatures below 50 °C. The enzyme activity was inhibited by 1 mM of Ni2+, Ba2+ and Fe2+. The apparent K m and V max values of purified enzyme for 2-deoxyribose-5-phosphate were 0.038 mM and 2.9 μmol min?1 mg?1, for 2-deoxyribose were 0.033 mM and 2.59 μmol min?1 mg?1, respectively, which revealed that the enzyme had similar catalytic efficiency towards phosphorylated and non-phosphorylated substrates. To synthesize statin intermediates, the bioconversion process for production of (3R, 5S)-6-chloro-2,4,6-trideoxyhexose from chloroacetaldehyde and acetaldehyde by the recombinant DERA was developed and a conversion of 94.4 % was achieved. This recombinant DERA could be a potential candidate for application in production of (3R, 5S)-6-chloro-2,4,6-trideoxyhexose. 相似文献
12.
Imene Chentir Amel Doumandji Jihene Ammar Fatma Zili Mourad Jridi Giorgos Markou Hatem Ben Ouada 《Journal of applied phycology》2018,30(3):1563-1574
The interactive effects of light intensity, NaCl, nitrogen, and phosphorus on intracellular biomass content and extracellular polymeric substance production were assessed for Arthrospira sp. (Spirulina) in a two-phase culture process using principal component analysis and central composite face design. Under high light intensity (120 μmol photons m?2?s?1) and low NaCl (1 gL?1), NaNO3, and K2HPO4 (0.5 g L?1), the carbohydrate content was maximized to 26.61%. Interaction of both K2HPO4 (1.6 gL?1) and NaCl (1.19 gL?1) with low NaNO3 (0.5 gL?1) achieved the maximum content of lipids (15.62%), while high NaCl (40 gL?1), K2HPO4, and NaNO3 (4.5 gL?1) enhanced mainly total carotenoids (0.85%). Conversely, under low light intensity of 10 μmol photons m?2?s?1 combined with 11.76 gL?1 of NaCl, 0.5 gL?1 of NaNO3, and 2.68 gL?1 of K2HPO4, the phycobiliprotein content reached its highest level (16.09%). The maximum extracellular polymeric substance (EPS) production (0.902 gg?1?DW) was triggered under moderate light of 57.25 μmol photons m?2?s?1 and interaction of high NaCl (40 gL?1) and K2HPO4 (4.5 gL?1) with low NaNO3 (0.5 gL?1). The maximization ratios of intracellular biomass content in terms of carbohydrate, lipid, total carotenoid, phycobiliprotein, and EPS production were 3.55-, 1.73-, 9.55-, 2.92-, and 1.46-fold, respectively, greater than those obtained at optimal growth conditions. This study demonstrated that the multiple stress factors applied to the adopted two-phase culture process could be a promising strategy to produce biomass enriched in various high-value compound. 相似文献
13.
Dalel Daâssi Héla Zouari-Mechichi Alicia Prieto María Jesús Martínez Moncef Nasri Tahar Mechichi 《World journal of microbiology & biotechnology》2013,29(11):2145-2155
A white-rot basidiomycete, isolated from decayed acacia wood (from Northwest of Tunisia) and identified as Trametes sp, was selected in a broad plate screening because of its ability to decolorize and dephenolize olive oil mill wastewater (OMW) efficiently. The major laccase was purified and characterized as a monomeric protein with apparent molecular mass of 61 kDa (SDS-PAGE). It exhibits high enzyme activity over broad pH and temperature ranges with optimum activity at pH 4.0 and a temperature of 60 °C. The purified laccase is stable at alkaline pH values. The enzyme retained 50 % of its activity after 90 min of incubation at 55 °C. Using ABTS, this laccase presented K m and V max values of 0.05 mM and 212.73 μmoL min?1 mg?1, respectively. It has shown a degrading activity towards a variety of phenolic compounds. The purified laccase was partially inhibited by Fe2+, Zn2+, Cd2+ and Mn2+, while Cu2+ acted as inducer. EDTA (10 mM) and NaN3 (10 mM) were found to completely inhibit its activity. 73 % OMW was dephenolized after 315 min incubation at 30 °C with 2 U mL?1 of laccase and 2 mM HBT. 相似文献
14.
Seung-Hye Hong Ho-Phuong-Thuy Ngo Lin-Woo Kang Deok-Kun Oh 《Biotechnology letters》2015,37(4):849-856
A recombinant alcohol dehydrogenase (ADH) from Kangiella koreensis was purified as a 40 kDa dimer with a specific activity of 21.3 nmol min?1 mg?1, a K m of 1.8 μM, and a k cat of 1.7 min?1 for all-trans-retinal using NADH as cofactor. The enzyme showed activity for all-trans-retinol using NAD + as a cofactor. The reaction conditions for all-trans-retinol production were optimal at pH 6.5 and 60 °C, 2 g enzyme l?1, and 2,200 mg all-trans-retinal l?1 in the presence of 5 % (v/v) methanol, 1 % (w/v) hydroquinone, and 10 mM NADH. Under optimized conditions, the ADH produced 600 mg all-trans-retinol l?1 after 3 h, with a conversion yield of 27.3 % (w/w) and a productivity of 200 mg l?1 h?1. This is the first report of the characterization of a bacterial ADH for all-trans-retinal and the biotechnological production of all-trans-retinol using ADH. 相似文献
15.
Qingqing Bi Baoqin Han Wanshun Liu Yilin Feng Zhongqing Jiang 《Biotechnology letters》2013,35(7):1115-1120
A new serine protease with fibrinolytic activity from a marine invertebrate, Urechis unicinctus, was purified to electrophoretic homogeneity using column chromatography. SDS-PAGE of the purified enzyme showed a single polypeptide chain with MW ~20.8 kDa. Its N-terminal sequence was IIGGSQAAITSY. The purified enzyme, UFEIII, was stable at pH 6–10 below 60 °C with an optimum pH of 8.5 at approx. 55 °C. The enzyme activity was significantly inhibited by PMSF and SBTI suggesting that it was a serine protease. In fibrin plate assays, UFEIII was contained 1.46 × 103 U (urokinase units) mg?1 total fibrinolytic activity, which consisted of 692 U mg?1 direct fibrinolytic activity and 769 U mg?1 plasminogen-activator activity. Km and Vmax values for azocasein were 1 mg ml?1 and 43 μg min?1 ml?1, respectively. 相似文献
16.
Ebru Cayir Aysegul Erdemir Ebru Ozkan Murat Topuzogullari Zeynep Busra Bolat Ayberk Akat Dilek Turgut-Balik 《Molecular biotechnology》2014,56(8):689-696
Tropical theileriosis is a disease caused by infection with an apicomplexan parasite, Theileria annulata, and giving rise to huge economic losses. In recent years, parasite resistance has been reported against the most effective antitheilerial drug used for the treatment of this disease. This emphasizes the need for alternative methods of treatment. Enolase is a key glycolytic enzyme and can be selected as a macromolecular target of therapy of tropical theileriosis. In this study, an intron sequence present in T. annulata enolase gene was removed by PCR-directed mutagenesis, and the gene was first cloned into pGEM-T Easy vector and then subcloned into pLATE31 vector, and expressed in Escherichia coli cells. The enzyme was purified by affinity chromatography using Ni–NTA agarose column. Steady-state kinetic parameters of the enzyme were determined using GraFit 3.0. High quantities (~65 mg/l of culture) of pure recombinant T. annulata enolase have been obtained in a higly purified form (>95 %). Homodimer form of purified protein was determined from the molecular weights obtained from a single band on SDS-PAGE (48 kDa) and from size exclusion chromatography (93 kDa). Enzyme kinetic measurements using 2-PGA as substrate gave a specific activity of ~40 U/mg, K m: 106 μM, kcat: 37 s?1, and k cat/K m: 3.5 × 105 M?1 s?1. These values have been determined for the first time from this parasite enzyme, and availability of large quantities of enolase enzyme will facilitate further kinetic and structural characterization toward design of new antitheilerial drugs. 相似文献
17.
This study, comprising three independent experiments, was conducted to optimize the zinc (Zn) application through seed coating for improving the productivity and grain biofortification of wheat. Experiment 1 was conducted in petri plates, while experiment 2 was conducted in sand-filled pots to optimize the Zn seed coating using two sources (ZnSO4, ZnCl2) of Zn. In the first two experiments, seeds of two wheat cultivars Lasani-2008 and Faisalabad-2008 were coated with 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75 and 2.00 g Zn kg?1 seed using ZnSO4 and ZnCl2 as Zn sources. The results of experiment I revealed that seed coating with 1.25 and 1.50 g Zn kg?1 seed using both sources of Zn improved the seedling emergence. However, seed coated with 1.25 and 1.50 g Zn kg?1 seed using ZnSO4 was better regarding improvement in seedling growth and seedling dry weight. The results of the second experiment indicated that seed coated with 1.25 and 1.50 g Zn kg?1 seed using ZnSO4 improved the seedling emergence and seedling growth of tested wheat cultivars. However, seed coating beyond 1.5 g Zn kg?1 seed using either Zn source suppressed the seedling emergence. Third experiment was carried out in glass house in soil-filled earthen pots. Seeds of both wheat cultivars were coated with pre-optimized treatments (1.25, 1.50 g Zn kg?1 seed) using both Zn sources. Seed coating with all treatments of ZnSO4 and seed coating with 1.25 g Zn kg?1 seed using ZnCl2 improved the seedling emergence and yield-related traits of wheat cultivars. Seed coating with 1.25 g Zn kg?1 seed also improved the chlorophyll a and b contents. Maximum straw Zn contents, before and after anthesis, were recorded from seed coated with 1.5 g Zn kg?1 seed using either Zn source. Increase in grain yield from seed coating followed the sequence 1.25 g Zn kg?1 seed (ZnSO4) >1.25 g Zn kg?1 seed (ZnCl2) >1.5 g Zn kg?1 seed (ZnSO4). However, increase in grain Zn contents from seed coated was 1.5 g Zn kg?1 seed (ZnCl2) >1.25 and 1.5 g Zn kg?1 seed (ZnCl2, ZnSO4) >1.25 g Zn kg?1 seed (ZnSO4). Seed coating with Zn increased the grain Zn contents from 21 to 35 %, while 33–55 % improvement in grain yield was recorded. In conclusion, wheat seeds may be coated with 1.25 g Zn kg?1 seed using either source of Zn for improving the grain yield and grain Zn biofortification. 相似文献
18.
Juliana L. França Marcelo R. Pinto Malson N. Lucena Daniela P. Garçon Wagner C. Valenti John C. McNamara Francisco A. Leone 《The Journal of membrane biology》2013,246(7):529-543
The stimulation by Mg2+, Na+, K+, NH4 +, and ATP of (Na+, K+)-ATPase activity in a gill microsomal fraction from the freshwater prawn Macrobrachium rosenbergii was examined. Immunofluorescence labeling revealed that the (Na+, K+)-ATPase α-subunit is distributed predominantly within the intralamellar septum, while Western blotting revealed a single α-subunit isoform of about 108 kDa M r. Under saturating Mg2+, Na+, and K+ concentrations, the enzyme hydrolyzed ATP, obeying cooperative kinetics with V M = 115.0 ± 2.3 U mg?1, K 0.5 = 0.10 ± 0.01 mmol L?1. Stimulation by Na+ (V M = 110.0 ± 3.3 U mg?1, K 0.5 = 1.30 ± 0.03 mmol L?1), Mg2+ (V M = 115.0 ± 4.6 U mg?1, K 0.5 = 0.96 ± 0.03 mmol L?1), NH4 + (V M = 141.0 ± 5.6 U mg?1, K 0.5 = 1.90 ± 0.04 mmol L?1), and K+ (V M = 120.0 ± 2.4 U mg?1, K M = 2.74 ± 0.08 mmol L?1) followed single saturation curves and, except for K+, exhibited site–site interaction kinetics. Ouabain inhibited ATPase activity by around 73 % with K I = 12.4 ± 1.3 mol L?1. Complementary inhibition studies suggest the presence of F0F1–, Na+-, or K+-ATPases, but not V(H+)- or Ca2+-ATPases, in the gill microsomal preparation. K+ and NH4 + synergistically stimulated enzyme activity (≈25 %), suggesting that these ions bind to different sites on the molecule. We propose a mechanism for the stimulation by both NH4 +, and K+ of the gill enzyme. 相似文献
19.
We evaluated the nighttime CO2 flux (ecosystem respiration) on Rishiri Island, located at the northern tip of Hokkaido, Japan, from 2009 to 2011, by using the relationship between atmospheric 222Rn and CO2 concentrations. The annual mean CO2 flux was 1.8 μmol m?2 s?1, with a maximum monthly mean in July (4.6 ± 2.6 μmol m?2 s?1) and a broad minimum from December to March (0.33 ± 0.29 μmol m?2 s?1). The annual mean was comparable to fluxes at the JapanFlux sites in northern Japan. During the season of snow cover (mid-December to early April), the CO2 flux was low (0.45 ± 0.43 μmol m?2 s?1). Total annual respiration was estimated at 679 ± 174 g cm?2, about 8 % of which occurred during the season of snow cover. 相似文献
20.
The relationships between water content of desiccated embryonic axes (using different methods of desiccation), the availability of water determined by differential scanning calorimetry (DSC) analysis and recovery percentage after liquid nitrogen (LN) exposure of Fortunella polyandra embryonic axes were investigated. The objectives were to understand thermal properties of desiccated embryonic axes during cryopreservation and to determine the critical moisture contents for successful cryopreservation of the embryonic axes. Excised embryonic axes were desiccated under laminar air flow (0, 10, 15, 30 and 45 min), over silica gel (0, 5, 15, 30 and 60 min), and ultra-rapidly (0, 5, 10, 20 and 25 min). Desiccation under laminar air flow resulted in an optimal water content of 0.150 gH2O g?1 dw and a survival of 50 % after cryopreservation, while the unfrozen water content (WCu) was 0.126 gH2O g?1 dw. After drying over silica gel, the optimal water content was 0.190 gH2O g?1 dw, where the survival was 40 % after cryopreservation and the WCu was determined as 0.177 gH2O g?1 dw. Using the flash-drying method, the optimal water content was found to be 0.145 gH2O g?1 dw, the survival was 50 % after cryopreservation and the WCu was 0.133 gH2O g?1 dw. Embryonic axes of F. polyandra showed low-to-moderate tolerance to desiccation. The results of the freezing transitions for all the desiccation times and methods showed that the onset temperature and the peak of the mean enthalpy decreased in size with decreasing water content. DSC elucidated the critical moisture contents and the cooling and melt enthalpies for successful cryopreservation of F. polyandra embryonic axes. 相似文献