Metabolism of gallic acid and catechin by Lactobacillus hilgardii from wine

The ability of Lactobacillus hilgardii 5w to metabolize gallic acid and catechin was evaluated. It was grown in a complex medium containing gallic acid or catechin. The metabolites were analyzed by high-performance liquid chromatography and identified by comparing the retention times and spectral data with the standards of a database. In gallic acid-grown cultures, gallic acid, pyrogallol, catechol, protocatechuic acid, p-hydroxybenzoic acid, p-hydroxybenzaldehyde, and p-hydroxybenzyl alcohol were detected. In catechin-grown cultures, catechin, gallic acid, pyrogallol, catechol, p-hydroxybenzoic acid, acetovanillone, and homovanillic acid were detected. This work presents evidence of gallic acid and catechin degradation by L. hilgardii from wine.     

Effect of soil on urease inhibition by substituted urea herbicides

The effects of some substituted urea herbicides, fenuron, monuron, diuron and linuron, on soil urease were investigated. All herbicides are soil urease mixed inhibitors and the same inhibition mechanism is presumed. A kinetic relationship, which takes into account herbicide adsorption, is developed in order to calculate the inhibition constants of soil urease from adsorption constants. A linear relationship between Hammett sigma values and log K_i for fenuron, monuron and diuron is obtained, from which the formation of a complex between herbicides and enzyme is proposed By comparing kinetic constants for soil urease with those obtained for jack bean, in the presence of the same herbicides, a possible effect of the soil matrix on the enzyme-herbicide complex is also suggested.     

应用几种植物物质及化合物抑制土壤脲酶活性和提高植物尿素氮的回收率

Effects of residues of 9 plants, lemon eucalyptus (Eucalyptus citriodora Hook., P1), robust eucalyptus (E. robusta Smith, P2), Nepal camphortree (Cinnamomum glanduliferum (Wall.) Nees, P3), tea (Camellia sinensis (Linn.) O. Ktze. f., P4), oleander (Nerium indicum Mill, P5), rape (Brassica campestris L., P6),Chinese tallow tree (Sapium sebiferum L., P7), tung (Vernicia fordii (Hemsl.), P8), and croton (Croton tiglium L., P9), 7 chemicals, boric acid (C1), borax (C2), oxalic acid (C3), sodium oxalite (C4), sodium dihydrogen phosphate (C6), sodium silicate (C7) and sodium citrate (C8), and a natural organic substance,humic acid (C5), on urease activity of a neutral purple soil and recovery of urea nitrogen by maize were studied through incubation and pot experiments. Hydroquinone (HQ) was applied as the reference inhibitor. After incubation at 37 ℃ for 24 h, 7 inhibitors with higher ability to inhibit urease activity were selected and then incubated for 14 days at 25 ℃. Results of the incubation experiments showed that soil urease activity was greatly inhibited by them, and the inhibition effect followed an order of P2＞P4＞C3＞C2＞P3＞C1＞HQ＞P1.The 7 selected materials reduced the accumulative amounts of N released from urea and the maximum urease activity by 11.7%～28.4% and 26.7%～39.7%, respectively, and postponed the N release peak by 2～4 days in the incubation period of 14 days under constant temperature, as compared to the control (no inhibitor).In the pot experiment with the 7 materials at two levels of addition, low (L) and high (H), the C1 (H), C3(H), C1 (L), P4 (L) and C2 (L) treatments could significantly increase the dry weights of the aboveground parts and the total biomass of the maize plants and the apparent recovery rate of urea-N was increased by 6.3%～32.4% as compared to the control (no hibitor).     

分光光度法测定树脂包衣尿素溶出的研究

研究了对二甲氨基苯甲醛分光光度法应用于树脂包衣尿素养分溶出测定的可行性。对二甲氨基苯甲醛与尿素在酸性条件下生成黄色物质,其吸光值与尿素溶液的浓度成正比。结果表明,该方法与蒸馏后滴定法测定尿素相关性非常好,测定过程中缩二脲和硝态氮、铵态氮的干扰少。树脂包衣尿素养分溶出测定期间,尿素样品分解量少,分光光度法与蒸馏后滴定法的测定结果相关性非常好。试验证明两种方法测定包衣尿素溶出均可给出满意的结果,但分光光度法更快速、简便,适合于大批量样品的测定。     

Enhanced anaerobic degradation of hexachlorobenzene in a Hydragric Acrisol using humic acid and urea

Humic substances acting as an electron shuttle and nitrogen transformation process influence remarkably the electron transfer in anaerobic reaction systems and thus may affect the reductive dechlorination of hexachlorobenzene(HCB). In order to develop an efficient agricultural strategy for the remediation of organochlorine-contaminated soils, a batch incubation experiment was conducted to study the effects of humic acid, urea, and their interaction on the reductive dechlorination of HCB in a Hydragric Acrisol with high iron oxide content. After 44 d of anaerobic incubation, the five treatments, sterile control,control, humic acid, urea, and humic acid + urea decreased HCB residues by 28.8%, 47.8%, 64.7%, 57.8%, and 71.3%, respectively. The amendment of humic acid or urea significantly decreased soil Eh values and accelerated Fe(Ⅲ) reduction to Fe(Ⅱ), thus promoting markedly reductive dechlorination of HCB. Humic acid had a larger dechlorination effect than urea. Since there was a synergistic interaction between humic acid and urea that accelerated HCB dechlorination, the treatment having both amendments together was the most efficient for HCB dechlorination. The results showed that the combination of NH_4~+-N supplied by a fertilizer and humic substance is a feasible strategy for the remediation of organochlorine-contaminated soils with abundant iron oxide.     

生物工程途径降解果酒中苹果酸的研究进展

降酸是果酒生产的一个关键技术环节,利用生物工程途径降解果酒中苹果酸是非常重要的;是非常重要的该文综述了苹果酸-乳酸发酵和苹果酸-酒精发酵相关基因的克隆及其在酿酒酵母中表达的研究进展,提出了存在的问题和今后的研究方向.     

Movement of urea and its hydrolysis products as influenced by moisture content and urease inhibitors

A laboratory experiment was conducted on an Aquic Udifluvent Belgian soil in order to study the movement of urea and its hydrolysis products. This study was carried out at two moisture levels (10 and 20%) upon the addition of three types of urease inhibitors: hydroquinone, phenylphosphorodiamidate (PPDA), and N-(n-butyl)phosphorothioic triamide (NBPT). The results clearly show the effects of the inhibitors in retarding the hydrolysis of urea. The highest effect was observed with NBPT, followed by hydroquinone, and PPDA. The effect was more pronounced at 10% than at 20% moisture content. It was clear that subsequent nitrification of the NH _inf4 ^sup+ formed was inhibited at the lower moisture level. At 10% moisture, from the 7th day of incubation on, some NH _inf4 ^sup+ moved about 3 cm and reached the top of the soil column. At 20% moisture, no NH _inf4 ^sup+ reached the surface as it was quickly nitrified. After 17 days of incubation and at 20% moisture, the total mineral N was more or less homogeneously distributed within the soil column. In contrast, at 10% moisture, the remaining urea and the hydrolysis products were still concentrated at the place of application. The distribution of urea and its hydrolysis products was comparable with 7 days of incubation at 20% moisture and 17 days at 10%.     

Relationship between varietal amino acid profile of grapes and wine aromatic composition. Experiments with model solutions and chemometric study

Synthetic solutions containing amino acids, sugar, water, and yeast nutrients have been fermented by Saccharomyces cerevisiae, and the volatile composition of the fermented media has been analyzed by GC. Eleven amino acid compositions imitating the characteristic amino acid profile of 11 different grape varieties were tested. Significant differences in the levels of some important volatile compounds (ethanol, ethyl acetate, acetic acid, higher alcohols and some of their acetates, methionol, isobutyric acid, ethyl butyrate, and hexanoic and octanoic acids) were found. The levels of some of the volatile compounds are well correlated with the aromatic composition of wines made with grapes of the same varieties. A multiple linear regression study produced good models for most of the odorants for which the level was related to the must amino acid composition. Partial least-squares regression models confirm that amino acid composition explains a high proportion of the variance in the volatile composition and show that the relationship between both sets of variables is highly multivariate. According to the different models, the levels of some byproducts of fatty acid synthesis are related to threonine and serine, the level of beta-phenyletanol is closely related to the level of phenylalanine, and methionol is strongly correlated to the must methionine contents. The addition of selected amino acids to different musts confirms the previous observations.     

Effect of organic matter and urease inhibitors on urea hydrolysis and immobilization of urea nitrogen in an alkaline soil

Summary Laboratory incubation experiments with ¹⁵N-labelled urea were conducted on a Aquic Udifluvent Belgian soil amended with barley straw, in, order to study the influence of three urease inhibitors, hydroquinone, phenyl phosphorodiamidate and N-(n-butyl) phosphorothioic triamide on urea hydrolysis and N transformations. The results demonstrated that the urea was hydrolyzed more rapidly when the soil was amended with ground barley straw. A pronounced inhibition of urease inhibitors occurred with the urea hydrolysis, but it was decreased by increasing the soil organic C content. A severe N immobilization (about 82–100% of the applied urea) occurred in soil samples that were rich in organic C. The addition of urease inhibitors increased urea-N immobilization by 5–30%. N-(n-butyl) phosphorothioic triamide had a stronger effect than the other two inhibitors when they were applied at the rate of 1%. However, the inhibitors decreased N immobilization when the soil was amended with barley straw.     

稳定性尿素中脲酶抑制剂作用效果的快速检测方法

以尿素残留差异率作为评价指标,研究了影响脲酶抑制剂抑制作用测定的主要因素,包括浸提温度、浸提时间、脲酶液浓度、土壤用量、浸提液种类等。确立了目前测定稳定性尿素中脲酶抑制剂抑制作用效果的最佳快速检测方法:以1.0000g普通尿素作为对照肥料,称取1.0000g稳定性尿素,加入0.5昏/L脲酶缓冲溶液100mL,10g风干土,在37℃下振荡5h后测定土壤中尿素残留量,以尿素残留差异率对脲酶抑制剂作用进行评价,提高了检测效率和准确度。     

Oxidation of glycerol in the presence of hydrogen peroxide and iron in model solutions and wine. Potential effects on wine color

Wine oxidation appears to include the formation of hydroxyl radical (*OH), an exceptionally reactive and thus nonselective compound that might be involved in the production of important aldehydes and ketones. This experiment examined the *OH oxidation of glycerol, a major wine constituent, and thus a likely target of such oxidation, in model wine, generated by hydrogen peroxide and iron catalysis. The oxidation products generated were analyzed as their hydrazones using LC-DAD/MS. Glyceraldehyde and dihydroxyacetone were the main compounds identified, both of which were also observed in naturally aged and *OH-oxidized wines. As anticipated, the presence of ethanol in the model wine did not preclude the formation of these compounds. Additionally, when a young red wine was treated with these oxidation derivatives, a noteworthy increase in color was observed, most likely due to the formation of novel anthocyanin-based structures.     

Nitrification results in underestimation of soil urease activity as determined by ammonium production rate

The majority of soil urease activity measurements have been based on the rate of ammonium production under optimal conditions. However, such procedures do not exclude ammonium consumption by the nitrification process. The purpose of this study was to determine the percentage of soil urease activity that is underestimated due to soil nitrification. Six soils with diverse properties were incubated using a standard procedure for measuring soil urease activity. The dynamics of nitrite and nitrate were observed during the incubation. Our results showed that the percentage of underestimation ranged from 7.38% to 15.97%, depending on soil types and whether or not a buffer was used. We recommend that nitrification be taken into account when soil urease activity is assayed by the ammonium production rate method.     

Defining the ascorbic acid crossover from anti-oxidant to pro-oxidant in a model wine matrix containing (+)-catechin

An examination of the ascorbic acid-induced oxidation of (+)-catechin was carried out. Using varying concentrations of ascorbic acid in a model white winebase, it was observed that there are at least two distinct steps in its oxidation process. The first step involves the formation of species that absorb in the visible region of the spectrum, while the second step generates species of less or no absorbance in the visible region. The first step reaches an absorbance maximum when ascorbic acid is completely oxidized. In winebase solutions containing both ascorbic acid and (+)-catechin, the lag period prior to the onset of (+)-catechin oxidation was dependent on the concentration of ascorbic acid. It was also observed that the end of the lag period corresponds to the complete oxidation of ascorbic acid. Xanthylium cations were identified as a species responsible for the increase in absorbance at 440 nm post lag period. The implication of the results, for establishing a chemical basis to the ascorbic acid crossover from antioxidant to pro-oxidant, is discussed.     

Effects of urease and nitrification inhibitors added to urea on nitrous oxide emissions from a loess soil

Urea fertilizer‐induced N₂O emissions from soils might be reduced by the addition of urease and nitrification inhibitors. Here, we investigated the effect of urea granule (2–3 mm) added with a new urease inhibitor, a nitrification inhibitor, and with a combined urease inhibitor and nitrification inhibitor on N₂O emissions. For comparison, the urea granules supplied with or without inhibitors were also used to prepare corresponding supergranules. The pot experiments without vegetation were conducted with a loess soil at (20 ± 2)°C and 67% water‐filled pore space. Urea was added at a dose of 86 kg N ha^–1 by surface application, by soil mixing of prills (<1 mm) and granules, and by point‐placement of supergranules (10 mm) at 5 cm soil depth. A second experiment was conducted with spring wheat grown for 70 d in a greenhouse. The second experiment included the application of urea prills and granules mixed with soil, the point‐placement of supergranules and the addition of the urease inhibitor, and the combined urease plus nitrification inhibitors at 88 kg N ha^–1. In both experiments, maximum emissions of N₂O appeared within 2 weeks after fertilization. In the pot experiments, N₂O emissions after surface application of urea were less (0.45% to 0.48% of total fertilization) than from the application followed by mixing of the soil (0.54% to 1.14%). The N₂O emissions from the point‐placed‐supergranule treatment amounted to 0.64% of total fertilization. In the pot experiment, the addition of the combined urease plus nitrification inhibitors, nitrification inhibitor, and urease inhibitor reduced N₂O emissions by 79% to 87%, 81% to 83%, and 15% to 46%, respectively, at any size of urea application. Also, the N₂O emissions from the surface application of the urease‐inhibitor treatment exceeded those of the granules mixed with soil and the point‐placed‐supergranule treatments receiving no inhibitors by 32% to 40%. In the wheat growth experiment, the N₂O losses were generally smaller, ranging from 0.16% to 0.27% of the total fertilization, than in the pot experiment, and the application of the urease inhibitor and the combined urease plus nitrification inhibitors decreased N₂O emissions by 23% to 59%. The point‐placed urea supergranule without inhibitors delayed N₂O emissions up to 7 weeks but resulted in slightly higher emissions than application of the urease inhibitor and the urease plus nitrification inhibitors under cropped conditions. Our results imply that the application of urea fertilizer added with the combined urease and nitrification inhibitors can substantially reduce N₂O emissions.     

Iron(III) tartrate as a potential precursor of light-induced oxidative degradation of white wine: studies in a model wine system

The potential for iron(III) tartrate to act as a photoactivator in light-induced oxidative degradation of white wine is described. Using a tartaric-acid-based model wine system containing 5 mg/L iron, exposure to light from a xenon arc lamp led to the oxidative degradation of tartaric acid and the production of glyoxylic acid. The critical wavelength of light for the degradation process was found to be below 520 nm. No glyoxylic acid was formed in the absence of iron and/or light. Flint glass offered little protection from the light-induced photodegradation of tartaric acid. Antique Green glass offered more protection but did not stop the photodegradation process.     

The effect of soil pH and high urea concentrations on urease activity in soil

The rate of hydrolysis of urea in soil over the wide range of concentrations, up to 10 moles N per dm³ soil solution, found in fertilizer practice, was examined in Begbroke sandy loam adjusted to different pH values. On rewetting air-dry soil, urease activity increased rapidly, reached a maximum within the first 24 h and then decreased slowly to level off after about 4 days. Pretreatment of the soil with urea or ammonium had no effect on the urease activity. Urease activity increased with substrate concentration, reached an optimum value and then decreased with rising urea concentration. The results could be explained by substrate inhibition at higher urea concentrations, and the data are well described by a modified Michaelis-Menten equation involving three parameters, V_max, K_m and K_i where K_i is an inhibition constant. K_m decreased linearily with rise in pH whereas K_i increased slightly between pH 4.9 and 7.0 and steeply between 7.0 and 8.4. V_max increased with rise in pH, reached a maximum value at pH 6.0 and then declined at higher pHs. There was a further reaction, reaching a maximum rate at a urea concentration of about 0.2 molar N in the soil solution, that followed Michaelis-Menten kinetics. K_m for this high affinity reaction increased up to pH 7.2 and then decreased at higher pH values; V_max increased up to pH 6.8 and then decreased. The contribution of the high affinity reaction was small except at low concentrations of urea.     

棕壤线虫对尿素配施尿酶抑制剂和硝化抑制剂的响应研究

Effects of urea amended with urease and nitrification inhibitors on soil nematode communities were studied in a Hapli- Udic Argosol （Cambisol, FAO） in Liaoning Province of Northeast China. A completely random design with four treatments, i.e., conventional urea （CU）, slow-release urea amended with a liquid urease inhibitor （SRU1）, SRU1 ＋nitrification inhibitor dicyandiamide （SRU2）, and SRU1 ＋ nitrification inhibitor 3,5-dimethylpyrazole （SRU3） and four replicates were applied. Thirty-nine genera of nematodes were identified, with Cephalobus and Aphelenchus being dominant; and in all treatments, the dominant trophic group was bacterivores. In addition, during the growth period of spring wheat （Triticum aestivum L.）, soil urease activity was lower in SRUs than in CU. The numbers of total nematodes and bacterivores at wheat heading and ripening stages, and omnivores-predators at ripening stage were higher in SUR3 than in CU, SRU1 and SRU2 （P 〈 0.05）.