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1.
Temperature and pH influence the conformation of the whey protein β-lactoglobulin (β-Lg) monomer, dimer, and octamer formation, its denaturation, and solubility. Most hydrolyses have been reported at trypsin (EC 3.4.21.4) optimum conditions (pH 7.8 and 37 °C), while the hydrolysate mass spectrometry was largely limited to peptides with <4 kDa. There are few reports on trypsin peptide release patterns away from optimum. This work investigated the influence of alkaline (8.65 and 9.5) and optimum (7.8) pH at different temperatures (25, 37.5, and 50 °C) on β-Lg (7.5%, w/v) hydrolysis. Sample aliquots were drawn out before the addition of trypsin (blank sample) and at various time intervals (15 s to 10 min) thereafter. Matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF-MS/MS) was used to monitor peptide evolution over time with the use of two matrixes: α-cyano-4-hydroxycinnamic acid (HCCA) and 2.5-dihydroxyacetophenone (DHAP). Mass analysis showed that the N- and C-terminals (Lys(8)-Gly(9), Lys(100)-Lys(101), Arg(124)-Thr(125), Lys(141)-Ala(142), and Arg(148)-Leu(149)) of β-Lg were cleaved early (15 s) implying the ease of trypsinolysis at the exposed terminals. Hydrolyses at 25 °C and pH 7.8 as well as at 50 °C and pH 9.5 were slowed down and ordered. Nonspecific chymotrypsin-like behavior occurred more at higher temperatures (50 °C) than at lower ones (25 and 37.5 °C). In addition to our earlier work in the acid pH region, it can be concluded that there is potential for controlled hydrolysis outside the trypsin optimum, where different target peptides with predictable biofunctionalities could be produced.  相似文献   

2.
Low concentrations of a disulfide reducing agent were added to unheated and heated (80 °C for 30 min) skim milk, with and without added whey protein. The reduction of the β-lactoglobulin and κ-casein disulfide bonds was monitored over time using electrophoresis. The distribution of the proteins between the colloidal and serum phases was also investigated. κ-Casein disulfide bonds were reduced in preference to those of β-lactoglobulin in both unheated and heated skim milk (with or without added whey protein). In addition, in heated skim milk, while the serum κ-casein was reduced more readily than the colloidal κ-casein, the distribution of κ-casein between the two phases was not affected.  相似文献   

3.
Increasing organic carbon (OC) stocks in soils reduce atmospheric CO2, but may also cause enhanced N2O emissions. The objective of this study was to determine whether there are any differences in N2O and CO2 emissions from sandy arable soils with different soil OC and total nitrogen stocks due to the annual application of either farmyard manure (S-FYM) or mineral fertilizer (S-MIN) over 27 years. A laboratory incubation was performed to test the short-term effects of the application of different fertilizers [farmyard manure (FYM), KNO3 (MIN) and biogas waste (BW)] on N2O and CO2 emissions. The CO2 emission rates indicated that OC availability in the soil was higher after BW application than after FYM application. N2O emission for 53 days following fertilizer application amounted to 0.01% (MIN), 0.21% (FYM) and 24% (BW) of the total amount of N applied. The high emissions induced by BW were attributed to the combination of a high availability of OC and ammonium in the fermented waste. Fertilization history, which caused higher soil OC stocks in S-FYM, did not influence N2O emissions. The results suggest that characterization of C and N pools in organic fertilizers is required to assess their impact on N2O emissions.  相似文献   

4.
This study describes a detailed and systematic investigation on the effect of thermal processing in terms of temperature and time (kinetic study) on β-carotene in vitro bioaccessibility in carrots. β-Carotene in vitro bioaccessibility increased with increasing processing temperature and time until steady-state conditions were reached after prolonged heating. The bioaccessibility values in steady-state conditions were temperature dependent. The experimental bioaccessibility data could adequately be modeled with a fractional conversion model. For the first time, modeling of processing-induced bioaccessibility changes is reported in literature. The results of the present kinetic study were used to estimate the impact of industrially relevant thermal processes on β-carotene bioaccessibility in carrots by simulation. It was shown that, to achieve a high β-carotene bioaccessibility, processing of carrots is essential (i.e., on the one hand, intense thermal processing or, on the other hand, mild thermal processing combined with intense mechanical processing).  相似文献   

5.
Increasing soil carbon (C) in arable soils is an important strategy to achieve sustainable yields and mitigate climate change. We investigated changes in soil organic and inorganic carbon (SOC and SIC) under conservation agriculture (CA) in a calcareous soil of the eastern Indo-Gangetic Plains of India. The treatments were as follows: conventional-till rice and wheat (CT-CT), CT rice and zero-till wheat (CT-ZT), ZT direct seeded rice (DSR) and CT wheat (ZT-CT), ZTDSR and ZT wheat without crop residue retention (ZT-ZT), ZT-ZT with residue (ZT-ZT+R), and DSR and wheat both on permanent beds with residue (PB-PB+R). The ZT-ZT+R had the highest total SOC in both 0–15 and 15–30 cm soil layers (20% and 40% higher (p < .05) than CT-CT, respectively), whereas total SIC decreased by 11% and 15% in the respective layers under ZT-ZT+R compared with CT-CT. Non-labile SOC was the largest pool, followed by very labile, labile and less labile SOC. The benefits of ZT and residue retention were greatest for very labile SOC, which showed a significant (p < .05) increase (~50%) under ZT-ZT+R compared with CT-CT. The ZT-ZT+R sequestered ~2 Mg ha−1 total SOC in the 0–15 cm soil layer in 6 years, where CT registered significant losses. Thus, the adoption of CA should be recommended in calcareous soils, for C sequestration, and also as a reclamation technique.  相似文献   

6.
Abstract

Two greenhouse studies were conducted to evaluate the effect of B, Mn and Zn on nodulation and N2‐fixation of southernpea (Vigna unguiculata (L.) Halp.) cultivars ‘Freezegreen’, ‘Mississippi Silver’ and ‘Pinkeye Purple Hull’. The cultivars were grown in plastic pots with a Norfolk sandy loam (fine, loamy siliceous thermic, Typic Paleudult) soil treated with B, Mn and Zn at rates of 0, 5, 10 and 20 kg/ha each at pH levels 5.5, 6.0 and 6.5. At pH 6.5 all micronutrient treatments significantly increased nodulation and N2‐fixation over the control (no micronutrient applied). The effects of B, Mn and Zn on nodulation and N2‐fixation depended on the cultivar and soil pH. For plants given the 5 kg/ha B and Mn treatments, ‘Mississippi Silver’ produced the highest number of nodules and ‘Pinkeye Purple Hull’ the least. At 20 kg/ha Zn, nodulation of ‘Freezegreen’ was highest and ‘Pinkeye Purple Hull’ the lowest. As a whole, maximum nodulation was at 5 kg/ha B and Mn and 20 kg/ha for Zn. Nitrogen fixation rates responded similarly except that the optimum rate for Zn was 10 kg/ha. Seed yield of plants peaked at 5 kg/ha for B and 10 kg/ha for Zn, indicating a possible relation of N2‐fixation to seed yield.  相似文献   

7.
The present work aims at evaluating the effect of cycloheximide at concentrations of between 0.5 and 5mgg–1 on N2O and NO3 production in two slightly alkaline soils, sampled from deciduous woodland and arable cultivation. In the first experiment, peptone was used as the “inducing substrate” for heterotrophic activity, and soil was incubated with cycloheximide (at different concentrations) and/or acetylene (1mll–1) to block induced eukaryotic protein synthesis and ammonia monooxygenase activity, respectively. Peptone addition stimulated N2O and NO3 production significantly in woodland soil, whereas arable soil showed no significant N2O emissions and low NO3 production. Low cycloheximide concentrations drastically reduced N2O emissions in woodland soil, suggesting a potential role of fungi in N2O emissions. However, acetylene was equally effective in blocking N2O emissions and part of NO3 production, so that a possible role of ammonia monooxygenase in an organic-inorganic pathway of N nitrification in fungal metabolism can be hypothesized. A second experiment was carried out on the woodland soil to check if low cycloheximide concentrations had non-target biocidal effects on soil microorganisms. Attention was focused on the range of concentrations which had reduced N2O emission in the woodland soil. The results suggested that at concentrations of cycloheximide between 0.5 and 2mgg–1 any biocidal effect on microbial biomass was negligible in the first 48h; therefore only selective inhibition of protein synthesis could be expected. The whole nitrifier population seemed to be particularly sensitive to cycloheximide concentrations higher than 2.5mgg–1. Received: 4 July 1997  相似文献   

8.
Abstract

To determine the effect of incubation on DTPA‐extractable Fe, Zn, and Cu in soils with a wide pH range (4.2 ‐ 9.4) and to determine the nature of this effect, soils were incubated at field moisture capacity for 1 week with and without a sterilant (toluene). After incubation these soils as well as their air‐dry counterparts were analyzed for DTPA‐extractable Fe, Zn, and Cu.

Incubated soils were significantly lower in DTPA‐extractable Fe, Zn, and Cu than air‐dry soils over all soil pH values tested but there was no significant difference in mean values for incubated soils due to the addition of toluene. The results suggest that, upon incubation at field moisture capacity, the decrease in DTPA‐extractable Fe, Zn, and Cu observed was noa‐microbial in nature.  相似文献   

9.
Biological treatment systems such as biofilters offer a potential alternative to the existing physicochemical techniques for the removal of volatile organic compounds from gaseous emissions. In this experimental work, continuous phase biofiltration of xylene vapors were performed in a laboratory scale compost biofilter that was inoculated with a xylene-acclimatized consortium. The performance was assessed by continuously monitoring the removal efficiency (RE) and elimination capacity (EC) of the biofilter at loading rates varying between 2–220 g?m?3?h?1. The steady-state removal efficiencies were maintained between 60% and 90% up to a loading rate of 80 g?m?3?h?1. The removal efficiency decreased significantly at loading rates higher than 100 g?m?3?h?1. The pressure drop values were consistently less and insignificant in affecting the performance of the system. The present study also focuses in evaluating the stability of biofilter during shut down, restart, and shock-loading operations. An immediate restoration of biological activity after few days of starvation indicated their capability to handle discontinuous treatment situations which is more common to industrial biofilters. The sensitiveness of the biofilm to withstand shock loads was tested by abruptly increasing/decreasing the loading rates between 9–55 g?m?3?h?1, where, removal efficiencies between 60–90% were achieved. These results prove the resilience of the biomass and the stability of the compost biofilter. Anew, results from kinetic analysis reveal that, steady-state xylene removal in the biofilter can be adequately represented by Michaelis–Menten type kinetics, and the kinetic constants namely, ECmax (120.4 g?m?3?h?1) and K s (2.21 g?m?3) were obtained.  相似文献   

10.
11.
Solution pH, temperature, nitrate (NO3 )/yammonium (NH4 +) ratios, and inhibitors effects on the NO3 and NH4 + uptake rates of coffee (Coffea arabica L.) roots were investigated in short‐term solution culture. At intermediate pH values (4.25 to 5.75) typical of coffee soils, NH4 + and NO3 uptake rates were similar and nearly independent of pH. Nitrate uptake varied more with temperature than did ammonium. Nitrate uptake increased from 0.05 to 1.01 μmol g‐1 FWh‐1 between 4 and 16°C, and increased three‐fold between 16 to 22°C. Between 4 to 22°C, NH4 + uptake rate increased more gradually from 1.00 to 3.25 μmol g‐1 FW h‐1. In the 22–40°C temperature range, NH4 + and NO3 uptake rates were similar (averaging 3.65 and 3.56 umol g‐1 FW h‐1, respectively). At concentrations ranging from 0.5 to 3 mM, NO3 did not influence NH4 + uptake rate. However, NO3 uptake was significantly reduced when NH4 + was present at 3 mM concentration. Most importantly, total uptake (NO3 +NH4 +) at any NO3 /NH4 + ratio was higher than that of plants fed solely with either NH4 + or NO4 . Anaerobic conditions reduced NO3 and NH4 + uptake rate by 50 and 30%, respectively, whereas dinitrophenol almost completely inhibited both NH4 + and NO3 uptake. These results suggest that Arabica coffee is well adapted to acidic soil conditions and can utilize the seasonally prevalent forms of inorganic N. These observations can help optimizing coffee N nutrition by recommending cultural practices maintaining roots in the temperature range optimum for both NH4 + and NO3 uptake, and by advising N fertilization resulting in a balanced soil inorganic N availability.  相似文献   

12.
The North East India houses around 130 ethnic tribal communities which exhibits unique tradition, dialect and culture. These communities collect edible plants from wild forming a common practice for livelihood and subsistence even today. Of the varieties of plant consumed, ferns and fern–allies also constitute an important food supplement. An inventory survey was conducted in order to assess the wild edible ferns and fern–allies which are used as vegetables by various ethnic communities of North East India. Altogether, twenty-three (23) ferns and fern–allies are found to be edible, and used in preparing various cuisines. Four species viz. Diplazium esculentum (Retz.) Sw., Huperzia phlegmaria (L.) Rothm., Huperzia squarrosa (G. Forst.) Trevis. and Nephrolepis cordifolia (L.) C. Presl were cultivated in small scale for consumption and horticultural purposes, while the rest of the species were directly harvested from wild habitat. Role of these ferns in local cuisines, other reported uses and bioactive components were discussed. The study also emphasises on future development of ferns and its allies as potential vegetables in North East India.  相似文献   

13.
Abstract

The effect of grinding on soil extraction was determined for two soil fractions and three extractants. Arsenic (As), beryllium (Be), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn) were extracted by aqua regia and 2 M nitric acid. Mehlich 3 extractant was used for determination of potassium (K), magnesium (Mg), calcium (Ca), phosphorus (P), iron (Fe), and aluminum (Al). One hundred forty‐seven agricultural soil samples representing all major soil types, climatic regions, and proportions of agronomic cultures in the Czech Republic were collected for the study. Particle size fractions smaller than 2 mm and smaller than 0.150 mm were chosen for investigation. Extraction of elements by aqua regia was similar for both size fractions of soil. Cold 2 M nitric acid is a weaker extractant than aqua regia, and a statistically significant increase in extractable Be (5%), Cd (6%), Co (11%), Cu (5%), Ni (5%), and V (2%) was measured with the finely ground soils. An increase for the finer fraction for K (10%) and Mn (25%) was found for Mehlich 3. A more complex nonlinear relationship was found for Mehlich 3 extractable Al and Fe. This was probably caused by a more intensive re‐adsorption of Fe and Al to the finely ground soils.  相似文献   

14.
15.
The green cracked "seasoned" Manzanilla-Alore?a table olive is a specialty with a high demand when prepared from fresh fruits; however, when stored fruits are used, the product loses its green color, presents a brownish tone, and loses demand. Different alternative storage systems for preventing such changes and preserving the freshness of the fruits were studied, and their effects on sugar, polyphenol, color, and microbiological changes were analyzed. The application of two washing waters in the presence of different compounds before brining markedly decreased the sugar and polyphenol contents in the flesh, without negatively influencing the color; it also caused the inhibition of yeasts and lactic acid bacteria (except in treatments using sodium metabisulfite and saturated carbon dioxide (CO(2)) in the storage olive brines. Salicylic acid inhibited microbial growth during washings and storage. The best long-term color was achieved in the presence of sodium metabisulfite. A combination of two washing waters (containing 5% sodium chloride (NaCl) and 0.1% sodium metabisulfite or saturated CO(2)), followed by immersion of the fruits in 15% NaCl brine with 0.1% sodium metabisulfite or brine under saturated CO(2) added, led to the best storage conditions.  相似文献   

16.
The effect of fluoride (F) on pH and solubility of organic matter (TOC), aluminium (Al), iron (Fe), calcium (Ca), magnesium (Mg) and potassium (K) in soil samples collected near an aluminium smelter in Norway was studied. Increased addition of F to the soil samples led to an increase in pH and concentrations of TOC, Al and Fe in solution. Most of the F and Al in solution were in the forms of ALFx-complexes. K solubility decreased in some soil samples, but there were no consistent effect on the solubility of Ca or Mg. The effect of NaF addition was significantly different from equimolar NaCl-treatments. The concentrations of Al, Fe, TOC and the pH-values were lower, while the concentrations of K, Mg and Ca were higher in the NaCl-treatments than in the NaF-treatments. The results from the experiment imply that F-pollution of soil induces breakdown of Al- and Fe-oxides/hydroxides and solubilize organic material in the soil. This may influence the availability of potentially toxic elements, such as AIFx-complexes, to microorganisms and plant roots.  相似文献   

17.
Abstract

Goethite, aluminum‐(Al)‐substituted goethite (GA2), and a system of kaolinite–goethite were examined for their ability to adsorb copper (Cu), zinc (Zn), and cadmium (Cd) as a function of pH, in two ionic strengths and two different metal concentrations. Specific surface area was determined by BET‐N2, whereas the charge development on the solid surface was studied in the pH range ~3.5 to ~10.0 by potentiometric titration under continuous flow of argon.

Constant capacitance (CCM) and the double‐layer model (DLM) were used to fit the titration and adsorption data with the help of the least‐square optimization program FITEQL32. In both models, surface site density was fixed at Ns=2.31 sites nm?2, whereas for CCM capacitance density was set at C=1.06. Alternatively, bibliographic suggestions for these two parameters were examined.

Aluminum‐substituted goethite exhibited higher specific surface area and adsorbed all three metals in lower pH values than the other solids. Moreover, GA2 exhibited point of zero salt effect (PZSE) higher than goethite, approaching that corresponding to Al2O3, possibly due to Al‐substitution, and the system exhibited PZSE values much higher than kaolinite, approaching that corresponding to goethite. The adsorption order for all three solids was Cu>Zn>Cd in any case, thus more Cu is adsorbed at a certain pH than Zn and even more than Cd, whereas the increase of metal concentration shifts the adsorption curve toward higher pH values.

Constant capacitance described the titration data satisfactorily, but by altering the Ns and C values, the fit became worse. Adsorption data are described by CCM, by emphasizing the formation of monodentate surface complex. Bidentate complex, in most of the cases, was of no importance in describing the data despite the evidence of its presence in recent spectroscopic studies for Cu and Cd on goethite. Alteration of Ns and C values worsened the fit in any case, and bidentate complex vanished. The DLM exhibited the worse fit in any case.  相似文献   

18.
The relative effectiveness of Amberlite IRC‐50 resin, in a recirculating ion exchange column, and several concentrations of MES [2(N‐mor‐pholino)ethanesulfonic acid] were evaluated for control of nutrient solution pH of hydroponically cultured soybean (Glycine max [L.] Merr. cv Williams). A low buffering capacity, urea‐based nutrient solution was used. MES buffer, at the concentrations evaluated (1,2, 4, and 10 mM), was less effective at maintaining desired pH than the IRC‐50 resin system. The pH of the 4.0 mM MES buffered nutrient solution decreased from 6.5 to below 4.0 in five days with 25 to 30 day old plants. By comparison, the pH of the IRC‐50 resin buffered nutrient solution dropped from 6.5 to 5.9 during the same period. Nitrate uptake by 27 to 29 day‐old plants was significantly slower when solutions were buffered with MES than with IRC‐50 resin. Rate of nitrate uptake decreased with increasing MES buffer concentrations and decreasing pH in short‐term studies on plants previously grown on IRC‐50 resin buffered nutrient solution. Mass of the plants grown on IRC‐50 resin buffered nutrient solution equaled or exceeded that of plants grown on 1, 2, or 4 mM MES. Total elemental uptake (mg/plant) by plants grown on nutrient solution buffered by IRC‐50 resin, for the ten elements tested, was equal to or greater than uptake by plants grown on nutrient solution buffered by 1, 2, or 4 mM MES. It is concluded that IRC‐50 resin in recirculating columns provides better pH control than does MES buffer for hydroponically grown soybean.  相似文献   

19.
Abstract

Low pH is one of the most yield‐limiting factors for crop production in Cerrado soils. The objective of this study was to determine influence of soil pH on grain yield and its components, and use of nutrients by dry bean in a no‐tillage system in an Oxisol (Typic Haplorthox) of the Cerrado region of Brazil. Five field experiments were conducted for three consecutive years. The pH levels were low (5.3), medium (6.4), and high (6.8), created by applying lime at the rates of 0, 12, and 24 Mg ha?1. Grain yield and its components were significantly influenced by soil pH. Adequate pH for grain yield and its components was 6.4. Maximum variation in grain yield was measured by shoot dry weight, and minimum variation was due to 100‐grain weight. Nutrient utilization efficiency was in the order of magnesium (Mg) > phosphorus (P) > calcium (Ca) > potassium (K) > nitrogen (N) > copper (Cu) > manganese (Mn) > zinc (Zn) > iron (Fe). Soil extractable P increased linearly with increasing pH in the range of 5.3 to 7.3. These results show that adequate soil pH is an important soil acidity index in improving bean yield in Brazilian Oxisols.  相似文献   

20.

Purpose

A reclaimed tidal land along the shore has poor soil properties such as high exchangeable sodium percentage (ESP), and electrical conductivity (EC) due to excess sodium (Na) content. Therefore, Na content should be decreased to improve the land productivity, and for this, gypsum has been widely used. The objective of this study was to determine the changes in ESP and EC of the gypsum-treated reclaimed tidal soil in a field scale.

Materials and methods

For this, gypsum was applied to Daeho reclaimed tidal land (500 ha) in Korea for 5 years (2006 to 2010). The Daeho reclaimed tidal land has been used as reclaimed paddy fields since 1993. The application rate of gypsum was calculated based on exchangeable calcium (Ca) contents and soil cation exchange capacity (CEC) to maintain 60 % exchangeable calcium percentage (ECP) of CEC in soil and the average amount treated was 1570 kg ha?1 year?1. The changes in ESP and EC were monitored from 2006 to 2010, and 2013.

Results and discussion

The ESP dropped from 80 % in 2006 to 34 % in 2013. The EC of the soil was decreased by 73 %, from 11.5 dS m?1 in 2006 to 3.1 dS m?1 in 2013. Eventually, it was estimated that the ESP will be lowered below 15 % in 2023 with continuous treatment of gypsum according to ECP calculation, and EC will be declined to reach at 0.5 dS m?1 in 2035, the average EC level of Korean rice paddy.

Conclusions

This field scale study evidenced that gypsum application effectively improves the soil properties of reclaimed tidal soil by decreasing ESP and EC.
  相似文献   

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