缓冲液种类对土壤酸性磷酸酶活性的影响

土壤酸性磷酸酶影响土壤有机磷矿化。选择不同的缓冲液种类和不同p H值测定土壤酸性磷酸酶活性,可影响数据的可比性。为明确缓冲液及p H值对不同土壤磷酸酶活性的影响程度,选取p H值4～8的土壤样本,测定了在醋酸盐缓冲液、柠檬酸盐缓冲液和MUB缓冲液3种不同培养条件下酸性磷酸酶活性变化。结果表明,采用MUB缓冲液条件可获得较稳定的土样区分序列,且与缓冲液的p H值的变化无关。在醋酸盐缓冲液和柠檬酸盐缓冲液条件下,不同p H值范围的不同土样之间土壤酸性磷酸酶活性变异系数变化剧烈,而采用MUB缓冲液获得的变异系数较其他缓冲液大,且趋势平稳。综合考虑,进行土壤酸性磷酸酶活性测定,可优先选用MUB缓冲溶液。     

Effect of humic amendments on inorganic N, dehydrogenase and alkaline phosphatase activities of a Mediterranean soil

Dehydrogenase activity, alkaline phosphatase activity and NH₄ ⁺, NO₂ ⁻ and NO₃ ⁻ concentrations were monitored in an aridisol treated with three commercially available humic amendments. The materials were of plant residue, lignite and peat origins. The humus plant residues, fulvic acids, with a high content of Kjeldahl-N, sustained high enzyme activities and highest levels of NH₄ ⁺, NO₂ ⁻ and NO₃ ⁻. Humus lignite (mainly humic acids) produced the highest dehydrogenase activity, whereas the alkaline phosphatase activity was not as high as that amendment with humus plant residues. The lower activity of alkaline phosphatase could not be attributed to the higher P content of humus lignite. Nitrification was also low, probably due to the low N content of this fertilizer. The amendment of humus peat origin (only humic acids) did not increase enzyme activity or inorganic N concentrations of soil. Our results show that although these materials are widely utilized and recommended as microbial and plant activators, they all behave very differently, and the effects on soil microbiological activity cannot be predicted solely on the basis of their humic and/or fulvic acid contents.     

Effect of high-pressure treatment on lipoxygenase activity

Solutions of commercial soybean lipoxygenase (100 microgram/ML in 0.2 M citrate-phosphate and 0.2 M Tris buffer were subjected to pressures of 0.1, 200, 400, and 600 MPa for 20 mm. The enzyme was stable at atmospheric pressure (0.1 MPa) over a wide pH range (5-9). In citrate phosphate buffer, the enzyme had maximum stability over the pH range 58 in untreated samples and after treatment at 200 MPa, but with increasing pressure, the pH stability range become narrower and centered around pH 78. The enzyme was more sensitive to acid than alkali, and at pH 9, it lost virtually all activity after pressurization at 600 MPa for 20 mm in both buffers. The activity of the crude enzyme extracted from tomatoes treated at 200 and 300 MPa for 10 mm was not significantly different from that of the untreated tomatoes, while a pressure of 400 MPa for 10 mm caused a significant decrease in activity and treatment at 600 MPa led to complete and irreversible activity loss. Compared to unpressurized tomatoes, treatment at 600 MPa gave significantly reduced levels of hexanal, cis-3-hexenal, and trans-2-hexenal, which are important contributors to "fresh" tomato flavor, and this was attributed to the inactivation of lipoxygenase.     

连续施用解磷菌肥对复垦土壤磷酸酶和Hedley磷形态的影响

为了研究增施解磷菌肥对土壤供磷状况的改善和土壤中磷有效性的提高状况,通过田间小区试验研究了连续施用解磷菌肥对复垦5年土壤碱性磷酸酶活性及Hedley磷形态的影响。结果表明:施用无机肥+有机肥+解磷菌肥处理的土壤碱性磷酸酶活性最高,为30.65μg/(g·h),比对照提高了83.86%。本试验年与第3年复垦土壤相比,土壤中Hedley磷形态的含量都有不同程度的增加,H_2O-Po含量以无机肥+有机肥+解磷菌肥处理为最高,比对照提高了93.90%;NaOH-Pi、HCl-Pi、HCl-Po含量以无机肥+解磷菌肥处理最大,分别比对照提高了194.2%、61.87%、105.8%;残渣态磷含量以无机肥处理影响最大,比对照提高了22.87%;H_2O-Pi、NaHCO_3-Po含量以有机肥处理最大,比对照提高了129.2%、85.89%;NaHCO_3-Pi、NaOH-Po含量以有机肥+解磷菌肥处理提高最大,分别提高了176.9%、114.4%。可以得出:施用解磷菌肥的处理增加复垦土壤中H_2O-Po、NaHCO_3-Pi、NaOH-Pi、NaOH-Po、HCl-Pi、HCl-Po含量的效果较好。H_2O-Pi、H_2O-Po、NaHCO_3-Pi、NaHCO_3-Po、NaOH-Pi、NaOH-Po、HCl-Pi与碱性磷酸酶均呈极显著相关。解磷菌肥在一定程度上增强了复垦土壤碱性磷酸酶活性,影响土壤中Hedley磷分级的各形态磷素含量,从而提高磷的有效性。     

Rapid screening method for alkaline phosphatase activity in cheese: collaborative study

The method developed for developed for determining alkaline phosphatase activity in cheese, in which phenolphthalein monophosphate is used as the substrate, was collaboratively studied. A 7.5% butanol extract of cheese is reacted with phenolphthalein monophosphate; phenolphthalein is released and yields a red solution that is compared visually with a standard (s) prepared from the same extract. Seven collaborators analyzed 8 samples of cheese, in duplicate, by the screening method and Scharer I method. Of the 208 observations returned, only 4 were incorrect. The alkaline phosphatase method has been adopted as official first action.     

Effect of lead on soil respiration and dehydrogenase activity

The effect of added Pb on the respiration and dehydrogenase activity of two sandy soils, a clay soil and a peat soil, (all with different physico-chemical properties), was studied.A concentration of 375 μg Pb· g^? inhibited the respiration of the sandy soil by ca. 15%, 1500 μg Pb· g^?ca. 50%. In the clay soil 1500 μg Pb· g^? caused a 15% reduction in respiration. The inhibition of respiration in the sandy soil was still ca. 30% 40 months after the addition of Pb. Respiration of the peat soil was not affected by even 7500 μg Pb· g^?.Dehydrogenase activity was affected by Pb in a similar way to soil respiration. In the sandy soil a considerable reduction occurred, while in the clay and peat soils dehydrogenase activity was not reduced.It was concluded, that a relationship exists between the inhibitory effects of Pb and the buffering capacity of the soil as expressed by its cation-exchange capacity. Because of these different effects of the same Pb concentration on the various soil types, no single value for the permitted concentration of lead pollution in soil could be established.     

Comparison of phosphorus fractions and alkaline phosphatase activity in sludge,soils, and sediments

Purpose  

The land application or disposal of sewage sludge generally leads to phosphorus (P) loss in aquatic environments and often results in eutrophication. The nature of P fractions plays a key role in the transport of P within the environment, and alkaline phosphatase is important for the transformation of the P fractions. The objective of this study was to assess the P fractions and alkaline phosphatase activity in sewage sludge, soils, and sediments, in order to effectively evaluate their P bioavailability and mobility.     

Effects of high-pressure processing at low temperature on the molecular structure and surface properties of beta-lactoglobulin

High-pressure processing (HPP) was utilized to induce unfolding of beta-lactoglobulin (beta-LG). beta-Lactoglobulin solutions at concentrations of 0.5 mg/mL, in pH 7.5 phosphate buffer, were pressure treated at 510 MPa for 10 min at either 8 or 24 degrees C. The secondary structure, as determined by circular dichroism (CD), of beta-LG processed at 8 degrees C appeared to be unchanged, whereas beta-LG processed at 24 degrees C lost alpha-helix structure. Tertiary structures for beta-LG, as determined by near-UV CD, intrinsic protein fluorescence spectroscopy, hydrophobic fluorescent probe binding, and thiol group reactivity, were changed following processing at either temperature. The largest changes to tertiary structure were observed for the samples processed at 24 degrees C. Model solutions containing the pressure-treated beta-LG showed significant decreases in surface tension at liquid-air interfaces with values of 54.00 and 51.69 mN/m for the samples treated at 24 and 8 degrees C, respectively. In comparison, the surface tension for model solutions containing the untreated control was 60.60 mN/m. Changes in protein structure during frozen and freeze-dried storage were also monitored, and some renaturation was observed for both storage conditions. Significantly, the sample pressure-treated at 8 degrees C continued to display the lowest surface tension.     

Effect of high-pressure processing at elevated temperatures on thiamin and riboflavin in pork and model systems

High-pressure/high-temperature properties of vitamins in food are important with respect to the new pressure-assisted thermal sterilization method utilizing pressure-induced adiabatic temperature changes. Riboflavin, thiamin, and thiamin monophosphate (TMP) stabilities were assayed in the temperature range from 25 to 100 degrees C under normal pressure (0.1 MPa) and high pressure (600 MPa) in acetate-buffered (pH 5.5) model solutions, some with added fructose, hemoglobin, or ascorbic acid. Thiamin and riboflavin stabilities were also assayed in minced fresh pork fillet and in rehydrated pork reference material with and without pressure treatment at 600 MPa in the temperature range from 20 to 100 degrees C. In pork, the vitamins proved to be sufficiently stabile for high-pressure/high-temperature processing. Under similar conditions, vitamin decay in model solutions was up to 30 times faster, especially that of TMP. Thus, it appears that it may not be possible to draw conclusions for the pressure behavior of real food matrices from the results of investigations in food models. A further consequence is that caution is necessary when supplementing foods with synthetic B vitamins preceding high-pressure/high-temperature processing.     

Effect of high-pressure-moderate-temperature processing on the volatile profile of milk

The effects of high hydrostatic pressure on volatile generation in milk were investigated in this study. Raw milk samples were treated under different pressures (482, 586, and 620 MPa), temperatures (25 and 60 degrees C), and holding times (1, 3, and 5 min). Samples submitted to heat treatments alone (25, 60, and 80 degrees C for 1, 3, and 5 min) were used for comparison. Trace volatile sulfur compounds were analyzed using solid-phase microextraction (SPME) and gas chromatography (GC) with pulsed-flame photometric detection (PFPD), whereas the rest of the volatile compounds were analyzed using SPME-GC with flame ionization detection (FID). Multivariate analysis of variance (MANOVA) and principal component analysis (PCA) were used to study the effect of pressure, temperature, and time on volatile generation. Relative concentration increases of 27 selected volatile compounds were compared to an untreated sample. It was found that pressure, temperature, and time, as well as their interactions, all had significant effects (P < 0.001) on volatile generation in milk. Pressure and time effects were significant at 60 degrees C, whereas their effects were almost negligible at 25 degrees C. The PCA plot indicated that the volatile generation of pressure-heated samples at 60 degrees C was different from that of heated-alone samples. Heat treatment tended to promote the formation of methanethiol, hydrogen sulfide, methyl ketones, and aldehydes, whereas high-pressure treatment favored the formation of hydrogen sulfide and aldehydes.     

Effect of mild-heat and high-pressure processing on banana pectin methylesterase: a kinetic study

Pectin methylesterase (PME) was extracted from bananas and purified by affinity chromatography. The thermal-high-pressure inactivation (at moderate temperature, 30-76 degrees C, in combination with high pressure, 0.1-900 MPa) of PME was investigated in a model system at pH 7.0. Under these conditions, the stable fraction was not inactivated and isobaric-isothermal inactivation followed a fractional-conversion model. At lower pressure (< or =300-400 MPa) and higher temperature (> or =64 degrees C), an antagonistic effect of pressure and heat was observed. Third-degree polynomial models (derived from the thermodynamic model) were successfully used to describe the heat-pressure dependence of the inactivation rate constants.     

Effects of fungicides on arbuscular mycorrhizal fungi: differential responses in alkaline phosphatase activity of external and internal hyphae

 The effect of four fungicides on alkaline phosphatase (ALP) activity in internal and external hyphae of an arbuscular mycorrhizal (AM) fungus was examined. Four-week-old plants were treated with an aqueous solution of the fungicides and then harvested 3 days later. Fungicides were applied at a low and a high level corresponding to 1 and 100 times the recommended field application dose. The fungicides were the two abundantly used sterol inhibitors, fenpropimorph and propiconazole, as well as a commercial mixture of them. Benomyl served as a positive control, as this fungicide is known for its deleterious effect on AM fungi. At harvest, roots and hyphae extracted from the soil were stained for ALP activity. Benomyl inhibited fungal ALP activity of both internal and external hyphae at the low application level (1 μg g^–1 soil) corresponding to the recommended field dose. Fenpropimorph had an intermediate effect, inhibiting both internal and external hyphae but only at the high application level (125 μg g^–1 soil). Propiconazole decreased the activity of the external hyphae at the low application level (0.21 μg g^–1 soil) but did not affect the internal activity at any application level. The effect of Tilt Top was similar to that of fenpropimorph. The results showed that the external hyphae were more sensitive than internal hyphae to application of fungicides. Received: 26 May 1999     

Comparison of effects of high-pressure processing and heat treatment on immunoactivity of bovine milk immunoglobulin G in enriched soymilk under equivalent microbial inactivation levels

Immunoglobulin-rich foods may provide health benefits to consumers. To extend the refrigerated shelf life of functional foods enriched with bovine immunoglobulin G (IgG), nonthermal alternatives such as high-pressure processing (HPP) may offer advantages to thermal processing for microbial reduction. To evaluate the effects of HPP on the immunoactivity of bovine IgG, a soymilk product enriched with milk protein concentrates, derived from dairy cows that were hyperimmunized with 26 human pathogens, was subjected to HPP or heat treatment. To achieve a 5 log reduction in inoculated Escherichia coli 8739, the HPP or heat treatment requirements were 345 MPa for 4 min at 30 degrees C or for 20 s at 70 degrees C, respectively. To achieve a 5 log reduction in natural flora in the enriched soymilk, the HPP or heat treatments needed were 552 MPa for 4 min at 30 degrees C or for 120 s at 78.2 degrees C, respectively. At equivalent levels for a 5 log reduction in E. coli, HPP and heat treatment caused 25% and no detectable loss in bovine IgG activity, respectively. However, at equivalent levels for a 5 log reduction in natural flora, HPP and heat resulted in 65 and 85% loss of bovine IgG activity, respectively. Results of combined pressure-thermal kinetic studies of bovine milk IgG activity were provided to determine the optimal process conditions to preserve product function.     

Effect of different treatments with crop residues on soil phosphatase activity

Summary Phosphomonoesterase (both acid and alkaline) and phosphodiesterase activity was either activated or inhibited in a soil treated with different crop residues. Phosphotriesterase activity remained unaffected. The kinetic parameters (V _max and K _m) of treated soil samples were modified in the same way: Increases or decreases in the V _max values corresponded to increases or decreases in the K _m values. The V _max values, rather than the K _m values, were found to have a predominant effect on phosphatase activity, thus indicating a fundamental role for the enzyme concentration. A positive and generally significant correlation was found between the activity of each phosphatase, which suggests an unspecific source of these enzymes. The values of the determination coefficients (R ² × 100) show that a low percentage of the variability may be ascribed to interactions among phosphatase activities.     

Determination of alkaline phosphatase in casein: collaborative study

A collaborative study was made to determine alkaline phosphatase in casein samples by the rapid colorimetric test. Six to eight collaborators tested 10 unknown casein samples containing various amounts of residual phosphatase with and without the addition of magnesium acetate. Results indicated that magnesium acetate significantly increased phosphatase activity. The collaborators correctly analyzed 95% of the samples with the added magnesium acetate. The method has been adopted official first action.     

丛枝菌根真菌根内菌丝碱性磷酸酶活性与菌根共生效应的研究

试验研究 3种丛枝菌根真菌根内菌丝碱性磷酸酶活性与菌根共生效应的结果表明 ,3种丛枝菌根真菌对宿主植物的效应不同 ,与接种G .spp处理和未接种对照相比 ,接种G .m和G .i处理显著增加玉米地上部和根系干物质量、P浓度和吸P量 ,但后两者间无显著差异 ;而接种G .spp处理与对照无显著差异。播种后 35d时接种G .m和G .i处理根内菌丝碱性磷酸酶活性显著高于接种G .spp处理 ,而前二者间无显著差异 ,且随生长时间的变化趋势相似 ,35d时酶活性最高 ,35～ 5 0d呈迅速下降趋势 ,至 70d时酶活性仍下降且趋于平缓。G .spp酶活性则一直处于较低水平 ,随生长时间的延长略有起伏。即接种不同丛枝菌根真菌时 ,根内菌丝碱性磷酸酶活性高的菌根真菌对玉米生长促进作用较大 ,可提高玉米P营养状况 ;反之则对玉米生长和P营养状况无明显促进作用 ,且与对照无显著差异。出苗后 35d时根内菌丝碱性磷酸酶活性是预测丛枝菌根真菌对玉米生长效应的有效生理指标之一。     

有机物料配比施用对土壤碱性磷酸酶活性的影响

本研究采用四因数二次回归 4 1 6A—最优设计方法 ,通过裸土盆栽试验 ,在施用少量N、P肥的基础上 ,研究了玉米秆、豆秆、麦秆和风化煤四种有机物料配合施用对石灰性褐土中碱性磷酸酶活性的影响 ,建立了上述四个因子与土壤碱性磷酸酶活性之间的数学模型 ,并分别进行了试验因子的主效应和互作效应的分析     

Inactivation of soybean trypsin inhibitors and lipoxygenase by high-pressure processing

Trypsin inhibitors (TIA), one of the antinutritional factors of soy milk, are usually inactivated by heat treatment. In the current study, high-pressure processing (HPP) was evaluated as an alternative for the inactivation of TIA in soy milk. Moreover, the effect of HPP on lipoxygenase (LOX) in whole soybeans and soy milk was studied. For complete LOX inactivation either very high pressures (800 MPa) or a combined temperature/pressure treatment (60 degrees C/600 MPa) was needed. Pressure inactivation of TIA was possible only in combination with elevated temperatures. For TIA inactivation, three process parameters, temperature, time, and pressure, were optimized using experimental design and response surface methodology. A 90% TIA inactivation with treatment times of <2 min can be reached at temperatures between 77 and 90 degrees C and pressures between 750 and 525 MPa.