Properties of Rice Straw Extract after Subcritical Water Treatment

Rice straw was separated into four parts: the upper, middle, and lower parts of the stem, and the leaf. They were treated with subcritical water at 140 to 260 °C. The yield, carbohydrate, protein, and phenolic contents were obtained as well as the UV-Vis absorption spectra and the radical scavenging activity of the extracts. The extracts obtained from the stem parts had almost the same characteristics and were different from those of the leaf part. The extracts, prepared at higher temperature, exhibited higher radical scavenging ability. The radical scavenging ability and the phenolic content showed a correlation (R ²=0.92), suggesting that the phenolic substances in the extract cause its antioxidant ability.     

Evaluation of a ristocetin bonded stationary phase for subcritical fluid chromatography of enantiomers

A stationary phase derived from ristocetin was evaluated for chiral separation in subcritical fluid chromatography. Separation of various enantiomers having different structures and pK(a) values were investigated using carbon dioxide and polar modifiers. The influence of modifiers, additives, temperature, and mobile phase flow rate on separations is presented. It is concluded that this stationary phase can be used for SFC despite its structural similarity with protein-derived stationary phases that can only be used in HPLC. The separation mechanisms could not be elucidated or predicted using these initial experiments. The separations of warfarin and, especially, efavirenz demonstrate the potential of this type of stationary phase for rapid SFC chiral separations.     

乙醇对瘤胃液接种稻秸的体外发酵产物及细菌群落结构的影响

旨在研究乙醇对山羊瘤胃液与水稻秸秆厌氧共培养的影响。利用频繁传代的体外发酵技术和高通量测序方法,分析了短链脂肪酸(SCFA)产量和细菌群落的变化。结果表明,经体外培养传代8次的稻秸发酵液的总短链脂肪酸产量显著高于瘤胃液(P<0.01);与未添加乙醇的稻秸发酵液相比,添加乙醇显著提高了乙酸、戊酸和己酸的比例,降低了丙酸和丁酸的比例(P<0.01),总SCFA产量及异丁酸和异戊酸比例无显著差异。与瘤胃液相比,稻秸发酵液的拟杆菌门(Bacteroidetes)相对丰度下降,厚壁菌门(Firmicutes)相对丰度升高(P<0.05),且添加乙醇显著提高了厚壁菌门和放线菌门(Actinobacteria)的相对丰度(P<0.05);添加乙醇使双歧杆菌属(Bifidobacterium)、未定性的毛螺菌属(unidentified Lachnospiraceae)、产琥珀酸菌属(Succiniclasticum)、脱硫弧菌属(Desulfovibrio)和未定性的梭菌属(unidentified Clostridiales)的相对丰度显著升高(P<0.05)。乙醇使稻秸发酵液的显著性差异物种(Biomarker)增加;稻秸发酵液与瘤胃液亲缘关系较近,而添加乙醇显著改变了细菌区系;短链脂肪酸比例在稻秸发酵液细菌群落多样性中具有重要作用。研究表明,体外频繁传代和添加乙醇可以提高稻秸发酵液的乙酸、戊酸和己酸产量,乙醇改变了稻秸发酵液的细菌群落结构。     

Manipulation of chiral resolution for isoxazoline-based IIb/IIIa receptor antagonists using various mobile phase additives in subcritical fluid chromatography

Subcritical fluid chromatography (SubFC) using a carbon dioxide-methanol mobile phase is used for the chiral resolution of IIb/IIIa receptor antagonist enantiomers. The chiral resolution of three analogs, each containing two chiral centers, is optimized using various mobile phase additives. The effects that acidic, basic, and neutral additives have on retention, efficiency, and resolution are examined. The additive that gives the best resolution was found to be dependent upon the functionality and charge of the chiral analyte. For charged analytes, additives that act as competing ions of the same charge as the chiral analyte dramatically improve efficiency and resolution. Resolution of neutral chiral analyte enantiomers is also greatly affected by the choice of mobile phase additive. Chirality 10:338–342, 1998. © 1998 Wiley-Liss, Inc.     

Variation in Biomass Properties among Rice Diverse Cultivars

Biomass properties of rice straws were compared among eight cultivars that formed a mini diverse set. The ethanol productivity from rice straws was evaluated employing a laboratory-scale method based on dilute acid-hydrolysis pretreatment. The results indicated significant variation in biomass properties among the cultivars.     

Amelioration of growth reduction of lowland rice caused by a temporary loss of soil-water saturation

Decreases in nutrient availability after loss of soil-water saturation are significant constraints to productivity in lowland rainfed rice soils. The effectiveness of soil amendments like lime and straw in ameliorating these constraints are poorly understood. This pot experiment was conducted in Cambodia to investigate changes in soil chemical properties and nutrient uptake by rice after applying lime or straw to continuously flooded or intermittently flooded soil. In continuously flooded soils, exchangeable Al decreased to below 0.2 cmolc/kg. Liming (pH 6.5–6.8) the continuously flooded soil decreased the levels of acetate extractable Fe and P, plant P uptake and shoot dry matter, but had no effect on either Bray-1 or Olsen extractable P values. By contrast, the addition of straw (3.5 g dry straw/kg soil) increased Bray-1, Olsen, and acetate extractable P, plant P uptake, shoot P, and shoot dry matter. The non-amended soils became strongly acidic after loss of soil water saturation: extractable Al increased to 1.0 cmol_c/kg, a potentially harmful level for rice. By contrast, extractable P decreased markedly under loss of soil water saturation as did plant P uptake, shoot P, and shoot dry matter. With loss of soil water saturation, liming substantially depressed the levels of Al but it did not increase plant P uptake, shoot P, and shoot dry matter. Straw addition not only decreased extractable Al levels to well below 0.6 cmol_c/kg under loss of soil water saturation, but it also increased extractability of soil P, plant P uptake, shoot P, and shoot dry matter. Thus, in rainfed environments, the incorporation of straw may be more effective than liming to pH 6.8 for minimising the negative effects of temporary loss of soil-water saturation on P availability, P uptake, and growth of rice.     

Biomethanation of rice and wheat straw

When rice or wheat straw was added to cattle dung slurry and digested anaerobically, daily gas production increased from 176 to 331 l/kg total solids with 100% rice straw and to 194 l/kg total solids with 40% wheat straw. Not only was methane production enhanced by adding chopped crop residues but a greater biodegradability of organic matter in the straws was achieved.The authors are with the Microbiology and Molecular Genetics Unit, Tata Energy Research Institute, 158 Jor Bagh, New Delhi 110 003, India     

Solubility of Saturated Fatty Acids in Water at Elevated Temperatures

The solubility in water of saturated fatty acids with even carbon numbers from 8 to 18 was measured in the temperature range of 60 to 230°C and at a pressure of 5 or 15 MPa. The pressure had no significant effect on the solubility. The solubility of the fatty acids increased with increasing temperature. At temperatures higher than about 160°C, the logarithm of the solubility in mole fraction was linearly related to the reciprocal of the absolute temperature for each fatty acid, indicating that the water containing solubilized fatty acid molecules formed a regular solution at the higher temperatures. The enthalpy of a solution of the fatty acids in water, which was evaluated from the linear relationship at the given temperatures, increased linearly with the carbon number of the fatty acid.     

烟杆还田对水稻产量和养分吸收的影响及其替代钾肥的效果

选择不同供钾能力的烟-稻轮作区稻田,研究了烟杆还田对水稻产量、钾素吸收利用的影响及其替代钾肥的效果.结果表明: 烟杆还田(2250 kg·hm^-2)和施钾肥(K₂O 75 kg·hm^-2)均能增加水稻产量和地上部钾素的累积量,其中烟杆还田配施钾肥的增幅最大,低钾(土壤速效钾含量＜100 mg·kg^-1)、中钾(土壤速效钾含量100～150 mg·kg^-1)和高钾(土壤速效钾含量＞150 mg·kg^-1)土壤的水稻分别增产13.3%、17.1%和13.5%.烟杆还田(St+NP)可以提高钾素吸收利用率和农学效率.但在水稻当前推荐施肥量(75 kg·hm^-2)条件下,烟杆还田配施钾肥(St+NPK)对钾肥(素)吸收利用率和农学效率无显著影响,说明当前推荐施钾量可能偏高.通过对烟杆还田替代钾肥的计算,发现还田烟杆可以替代10%～22%的化肥钾(K₂O),烟后晚稻在烟杆还田时钾肥施用可以减少7.2～16.5 kg·hm^-2.因此,在烟杆还田条件下,高钾田块可减少化学钾肥的施用,而中钾和低钾田块为稳定水稻产量和维持土壤钾素平衡,则应保证目前推荐钾肥量的投入.     

Degradation kinetics of passion fruit pectin in subcritical water

The degradation of passion fruit pectin by subcritical water treatment in a continuous flow-type reactor was investigated in the temperature range of 80?160 °C at a constant pressure of 5 MPa. Changes in the degree of polymerization and reducing end formation were monitored and modeled by applying the Emsley equation and zeroth-order kinetics, respectively. The results showed that both the pectin degradation rate constant and the change in the amount of reducing end were enhanced by temperature, and that the temperature dependence of these parameters obeyed the Arrhenius relationship. The activation energies for pectin degradation and reducing end formation were 62.8 and 86.9 kJ/mol, respectively. The non-linear relationship between the ratio of broken galacturonic acid units to the total galacturonic acid units and the change in the amount of reducing end indicated that pectin cleavage became easier as hydrolysis progressed.     

碳氮比对模拟水稻秸秆田间厌氧发酵系统甲烷生产和秸秆降解的影响

利用自制的厌氧发酵装置模拟田间厌氧发酵产生物甲烷的条件,通过添加不同量的尿素,研究C/N对水稻秸秆厌氧发酵产生物甲烷和秸秆降解的影响。设置了C/N为15∶1、20∶1、25∶1、30∶1和对照（53∶1）等五个处理,测定各处理的产气量、甲烷含量和秸秆木质纤维素含量。结果表明C/N对厌氧发酵产气进程有一定影响,峰值出现的时间、峰值的大小在不同处理之间均有差异：以C/N为25∶1的处理峰值出现的最早,较对照早5d出现;以C/N为20∶1的峰值最高,较对照提高了27.55%。C/N对厌氧发酵累积产气量和累积甲烷产量有显著影响,以C/N为20∶1的处理累积产气量（4235.00mL）和累积甲烷产量（1526.34mL）最高,相比对照组的累积产气量和累积甲烷产量分别提高了30.78%和51.31%。C/N对水稻秸秆降解也有显著影响。以20∶1和25∶1处理对秸秆降解的效果最好,其中20∶1处理的总降解率、纤维素降解率和半纤维素降解率分别达到了51.33%、55.31%和53.05%,25∶1处理分别为50.00%、53.08%和49.42%。上述结果表明通过添加尿素调节C/N能够提高水稻秸秆厌氧发酵的产生物甲烷效率和促进秸秆降解,以C/N为（20~25）∶1处理的促进效果最好。     

Temperature effects for chiral separations using various bulk fluids in near-critical mobile phases

As supercritical fluid chromatography becomes more accepted as a facile means for the separation of chiral compounds, the need for mobile phases that can readily solubilize these polar compounds grows. Prior studies suggest that HFC-134a may prove suitable due to its very high eluotropic strength compared to carbon dioxide-based mobile phases. A comparison is made between ethanol-modified carbon dioxide, HFC-134a, and decafluoropentane as to their relative eluotropic strength, selectivity, and efficiency for three chiral compounds using a Whelk O-1 chiral bonded phase. The bulk component of the mobile phase was found to have relatively little effect on chiral selectivity over the range of 5° to 95°C. Chirality 9:693–698, 1997. © 1997 Wiley-Liss, Inc.     

不同培养条件下纤维素分解菌对稻草的分解研究

通过不同培养条件 4株纤维素分解菌对稻草的分解试验 ,发现不同纤维素分解菌对稻草纤维素的分解能力有一定的差异 ,部分菌株混合接种培养的分解率明显高于单独培养的分解率 ,混合培养时分解率受接种顺序影响不明显 ,在 1株分解木质素较强菌株 (侧孢霉 )存在情况下 ,培养前期升高培养温度能提高分解率     

微生物处理对秸秆结构的影响

使用红外光谱、X射线衍射及扫描电镜对4种经固态培养的微生物降解稻草秸秆的效果进行了研究,并与原稻草粉进行结构对比分析。结果表明：经过高碳低氮培养,秸秆木质素均有明显降解,其中黄孢原毛平革菌达到37.17%。扫描电镜发现秸秆的表面形态和内部结构发生了明显改变,红外光谱中芳香环与醚键吸收明显减少,X射线衍射得到的结晶度最大下降了5.60%。     

Chiral resolution of some antimalarial agents by sub- and supercritical fluid chromatography on an (S)-naphthylurea stationary phase

The behavior of mefloquine, halofantrine, enpiroline, quinine, quinidine, chloroquine and primaquine is studied by subcritical fluid chromatography on a (S)-naphthylurea column (250 mm × 4.6 mm ID) with a subcritical mobile phase composed of carbon dioxide, methanol and triethylamine (flow rate of 3 ml/min). Except for primaquine and chloroquine, each enantiomer was separated at a temperature between 40 and 60°C, and at a pressure below 15 MPa. A 98/2, v/v CO₂/methanol 0.1% triethylamine mixture allowed the separation of halofantrine enantiomers while the enantiomers of the more polar metabolite (N-desbutylhalofantrine) were separated with a 80–20 v/v mixture as used for mefloquine, enpiroline, quinine and quinidine. The influence of temperature, pressure and of the nature of the mobile phase is discussed. © 1993 Wiley-Liss, Inc.     

Remediation of Gulf War Oil Spill Contaminated Soil by a Subcritical Water Extraction Process: Oil Removal,Recovery, and Degradation

Due to the unique properties of subcritical water (marked change in water's dielectric constant and viscosity), the extraction by subcritical water offers a great opportunity to remediate soil contaminated with organic pollutants as an alternative and green remediation method. In this study, subcritical water extraction is proposed as an efficient remediation technique for the Gulf War oil spill contaminated soil. The subcritical water extraction experiment was carried out in a lab-scale continuous flow apparatus. The three major operating factors, temperature, time and water flow rate, were evaluated in terms of optimum removal efficiency. The results show that crude oil removal depended largely on water temperature, whereas an extraction run time higher than 1 h and a water flow rate higher than 1.5 mL/min marginally or negatively affected removal efficiency. During subcritical water treatment at 300°C for 1 h at a flow rate of 1.5 mL/min, removal efficiency was almost 95%. Under these operating conditions, the subcritical water treatment demonstrated a similar removal efficiency to those of organic solvents like acetone. In contrast, the efficiency of oil recovery decreased with an increase in extraction temperature, due to degradation by a water self-oxidizing agent. Several degradation products identified in the treated soil and in the effluent sample (which initially were absent in the contaminated soil) were oxygen-containing aromatic compounds, confirming the oxidation-degradation.