草酸脱羧酶促进草酸钙结晶溶解的体外研究

在体外实验条件下,考察了加酶量、反应pH值、反应温度及其产物甲酸根等因素对草酸脱羧酶催化草酸降解从而促进草酸钙结晶重新溶解过程的影响。结果表明,在10 mL反应体系中,添加4 U草酸脱羧酶,反应pH 3.0,反应温度为37 ℃,反应进行1 周（168 h）,可使近5%的草酸钙结晶重新溶解;实验结果表明,草酸降解产物甲酸根对草酸脱羧酶促进草酸钙结晶溶解产生抑制作用。     

间接原子吸收光谱法测定食品中的草酸

建立食品中草酸含量测定的新方法-间接原子吸收光谱。样品经处理后,加入过量且定量的氯化钙,使其与草酸根离子生成草酸钙沉淀,经离心分离后再利用原子吸收光谱(AAS)法定量测定上清液中剩余Ca2+ 的含量,间接计算出食品中草酸的含量。在最佳条件下,该法的线性范围为0～8.0mg/L,回收率为98.1%～98.4%。本方法精密度高、灵敏度高、检出限低,适用于食品中草酸含量的测定。     

响应面法优化草酸钾溶液提取菜籽饼中植酸工艺

菜籽饼是提取植酸的良好原料,植酸具有独特的生物活性.采用草酸钾溶液提取菜籽饼中的植酸,在单因素试验的基础上,通过响应面法优化植酸提取工艺,建立了以草酸钾溶液提取植酸的二次多项数学模型,并得到最佳工艺条件为:pH 8,液料比14∶1,草酸钾溶液浓度0.075 mol/L,提取时间5h.经过验证试验,在最佳工艺条件下,植酸得率为1.81％.     

Oxalate contents of species of the Polygonaceae,Amaranthaceae and Chenopodiaceae families

A high dietary oxalate intake influences mineral and trace element absorption in humans and may lead to calcium oxalate stone formation due to the ability of oxalate to form insoluble complexes with divalent cations in the gastrointestinal tract. The soluble and total oxalate contents of species in the Polygonaceae, Amaranthaceae and Chenopodiaceae families were measured using an HPLC-enzyme-reactor method. Polygonaceae, Amaranthaceae and Chenopodiaceae include most of the foods with excessively high oxalate concentrations. Amaranth is a specie of the Amaranthaceae family, Polygonaceae include buckwheat, rhubarb, and sorrel, whereas beetroot, mangold, spinach, and quinoa are species of the Chenopodiaceae family. Obviously, oxalate is accumulated in these plant families in each plant tissue, i.e., in leaves, stems, hypocotyl-root and nuts. The highest oxalate content was found in leaves and stems of plants in these families. Soluble oxalate ranged from 59 to 131 mg/100 g in roots and nuts, and from 258 to 1029 mg/100 g in leaves and stems. Total oxalate ranged from 143 to 232 mg/100 g in roots and nuts, and from 874 to 1959 mg/100 g in leaves and stems. Patients with calcium oxalate stone disease should be advised to avoid these oxalate-rich foods.     

Oxalate and Oxalate Oxidase in Malt

Barley kernels contain a single oxalate oxidase located in the embryo and aleurone. It is already present in substantial quantities in unmalted grain and increases in activity during germination. It displays a very broad pH optimum: the optimum was at pH 4.0, but the enzyme still displayed more than 50% of its activity at pH 7. Oxalate oxidase is highly resistant to heat. However, its low affinity for oxygen suggests that it probably does not play a major role in the consumption of oxygen in mashing. The decrease in oxalic acid levels late in germination may be a result of oxalate oxidase action. Oxalic acid was not detected in raw barley.     

竹子碱法制浆过程中草酸根形成的研究

研究了竹子碱法制浆过程中蒸煮工艺条件对草酸根形成的影响,揭示了蒸煮过程中草酸根的形成与纸浆卡伯值的关系。结果表明,在竹子碱法蒸煮过程中,随着蒸煮反应的进行,草酸根的形成量逐渐增加,提高蒸煮最高温度、增大液比、增加用碱量均会导致草酸根形成量的增加,但当用碱量超过21%时,继续增加用碱量则不会使草酸根的形成量增加。草酸根的形成量随纸浆卡伯值的降低而增加。此外,根据H-因子、用碱量与草酸根形成量的关系,构建了竹子碱法制浆过程中草酸根形成的数学预测模型。该模型的预测准确性较高,可用于竹子碱法制浆过程中草酸根形成的预测。     

制浆和漂白过程中草酸根的产生及其控制

阐述了制浆和漂白过程草酸根的来源及其形成机理,并对制浆和漂白过程中草酸根的研究现状及其进展进行了介绍.探讨了草酸根对制浆造纸工业安全生产的影响及危害,提出了控制和减少草酸根产生的相应对策.     

重组草酸脱羧酶的表达及酶学性质研究

研究了重组草酸脱羧酶的表达及其酶学性质。经IPTG诱导,每克湿重菌体收获草酸脱羧酶活力820U,经Ni-NTA亲和层析酶液纯化2.07倍,酶活力回收60.38%。酶促反应的最适温度为50~55℃,最适pH值为3.5,添加EDTA及Fe2+对酶活力有促进作用,Mn2+抑制酶活。在pH4.0,温度37℃下Km值为14.53 mmol/l,Vmax为133.33 U/mg。     

Application of sodium oxalate in the dyeing of cotton fabric with reactive red 3BS

The feasibility of using sodium oxalate in the dyeing of cotton fabrics with reactive dyes in place of inorganic salt (sodium sulfate or sodium chlorate) was studied. Sodium oxalate was compared with sodium formate and sodium citrate in cotton dyeing with reactive dyes. The results showed that sodium oxalate could be a suitable exhausting agent in the reactive dyeing process. The effect of sodium oxalate to enhance a photochemical reaction is also researched by measuring the color removal of the reactive dye solution. The results revealed that color removal of the dye solution containing sodium oxalate is 5.62% higher than that containing sodium sulfate after irradiation for 30?min. The overall results suggested that sodium oxalate has the potential not only as an exhausting agent for reactive dyeing of cotton but also as an accelerant for photochemical reaction in the treatment of dyeing wastewater.     

大麻纤维草酸铵-酶联合脱胶工艺

为开发绿色高效的大麻脱胶工艺,提出了草酸铵-酶联合脱胶,采用正交试验优化草酸铵脱胶工艺,并与经传统化学脱胶工艺、化学-酶联合脱胶工艺处理后大麻纤维的脱胶效果进行比较,得到草酸铵-酶联合脱胶最佳工艺条件:草酸铵质量浓度为4.0 g/L,保温温度为100 ℃,保温时间为50 min。结果表明:经最佳工艺处理后大麻纤维的残胶率为2.34%,低于经传统化学脱胶后大麻纤维的残胶率12.88%和化学-酶联合脱胶后大麻纤维的残胶率8.43%;草酸铵-酶联合脱胶后大麻纤维中木质素质量分数由8.10%(大麻原麻)下降到0.94%,断裂强度为10.31 cN/dtex,且白度优于传统化学脱胶工艺和化学-酶联合脱胶工艺处理后的大麻纤维。     

The effect of cooking on the location and concentration of oxalate in three cultivars of New Zealand‐grown oca (Oxalis tuberosa Mol)

Oca (Oxalis tuberosa Mol) originates from South America but is now also grown commercially in New Zealand. It contains moderate amounts of oxalate, which is only present in its soluble form. The skin of the oca tuber is thought to contain more oxalate than the flesh. In this study the concentration of soluble oxalate was measured in the skin and outer and inner flesh and in the whole tuber of raw, boiled, baked and steamed oca. The analysis was carried out on the traditionally pinkish‐red New Zealand cultivar and on the newly introduced cultivars ‘Mellow Yellow’ and ‘Apricot Delight’. In the raw oca tuber the oxalate concentration in the skin is significantly higher than in the flesh (mean value 7.3 g kg^?1 fresh weight (FW) compared to 1.7 and 1.4 g kg^?1 FW in the outer and inner flesh respectively). The highest concentration was found in the skin of the pinkish‐red cultivar (10.9 ± 1.0 g kg^?1 FW). All cooking methods seemed to cause a migration of oxalate from the skin to the underlying flesh. On a fresh weight basis, baking significantly increased the oxalate concentration in the whole tuber, whereas boiling decreased the concentration and steaming had no significant effect (p < 0.001). Boiling might therefore be a better way of cooking oca than baking when a low intake of oxalate is desired. © 2001 Society of Chemical Industry     

水稻谷糠中的草酸氧化酶及其特性研究

在水稻谷糠中检测到草酸氧化酶(OxO, EC1.2.3.4)的活性,其主要存在于细胞壁中,最适pH 值为2.5,Km值为0.63mmol/L,当底物草酸的浓度大于2.0mmol/L 时会出现底物抑制;此外,该酶热稳定性很高,而且对胃蛋白酶、SDS 和高浓度的NaCl 不敏感;1mmol/L 的EDTA、NH4+、 Cl －、Mn2+、CO32 －、Na+、K+、H2PO4 －、SO42 －、 Fe2+ 和PO43 －对其活性没有影响,但1mmol/L 的NO3 －、 Co2+、 Zn2+、Cu2+、 Mg2+、 Ca2+ 和 Al3+ 会抑制它的活性。因此,谷糠中的OxO 可能被广泛用于测定草酸含量。     

A survey of nitrate and oxalate content in fresh vegetables

A survey of nitrate and oxalate ((COO⁻)₂) content in fresh vegetables was conducted in Bari (Italy) over 15 months (from March 1994 to May 1995). A total of 327 samples (edible portions and related sub-samples) were taken from 26 different vegetable types on the wholesale fruit and vegetable market. The data revealed that leaf vegetables (namely rocket, celery, parsley and spinach) contained higher levels of nitrate than bulb, root, shoot, inflorescence and tuber vegetables. Higher oxalate levels were found in spinach and Swiss chard. Based on consumption data for the whole population provided by the National Institute of Nutrition, daily nitrate intake from vegetables was calculated to be 71 mg. Over 30% of nitrate intake was derived from the consumption of lettuce and Swiss chard. © 1999 Society of Chemical Industry     

草酸钾添加量对卷烟纸热解性能及主流烟气的影响

通过在卷烟纸上添加不同量的草酸钾,采用常规烟气分析、同步热分析,研究其对卷烟纸热解性能及主流烟气的影响.结果表明:在卷烟纸上添加草酸钾后对卷烟主流烟气中的焦油和CO有一定的降低作用,随着添加量的继续增加,抽吸口数、CO和焦油释放量均呈先下降后缓慢上升趋势;在草酸钾添加量为1.5%时,其降焦及降CO效率最高;随着草酸钾添加量的增加,卷烟纸热解起始温度降低,在200～300℃时反应活化能降低.     

Aspects of the kinetics and solubility of silica and calcium oxalate composites in sugar solutions

Fouling of industrial surfaces by silica and calcium oxalate can be detrimental to a number of process streams. Solution chemistry plays a large roll in the rate and type of scale formed on industrial surfaces. This study is on the kinetics and thermodynamics of SiO₂ and calcium oxalate composite formation in solutions containing Mg²⁺ ions, trans-aconitic acid and sucrose, to mimic factory sugar cane juices. The induction time (t_i) of silicic acid polymerization is found to be dependent on the sucrose concentration and SiO₂ supersaturation ratio (SS). Generalized kinetic and solubility models are developed for SiO₂ and calcium oxalate in binary systems using response surface methodology. The role of sucrose, Mg, trans-aconitic acid, a mixture of Mg and trans-aconitic acid, SiO₂ SS ratio and Ca in the formation of composites is explained using the solution properties of these species including their ability to form complexes.     

Isolation and characterisation of scale and turbid particles in beet sugar processing and the quality of granulated sugar

The objective of this work is to unveil the nature of scale and of particles responsible for turbidity in white beet sugar. Different techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD) were applied for identification of the structure of scale and turbid particles. Results clearly showed that sugar turbidity is mainly constituted of fine crystals of calcium oxalate dihydrate (COD). These turbid particles were found comparable to the scale observed in the last effects of evaporation station. The role of anti-scale agents was studied. It was found that the chelating of calcium by anti-scales prevents the formation of calcium oxalate in evaporators. However, this chelating is temporary and the problem posed by the precipitation of oxalate particles is delayed to the crystallisation step where it was identified as responsible for stored syrup precipitate and granulated sugar turbidity.     

草酸脱羧酶的性质及应用研究进展

草酸脱羧酶（oxalate decarboxylase,Oxdc）属Cupin蛋白超家族,是一种包含Mn2+的均一聚合酶,能够在没有辅因子的条件下催化草酸转化为甲酸和CO2,是植物、微生物中促使草酸代谢降解的主要酶之一。该酶已在农业、食品、工业生产、医疗和生物监测等领域得到了广泛的应用。本文综述近年来在Oxdc来源、结构、作用以及实际应用方面的研究,着重讨论其在泌尿系统草酸盐结石病症方面的作用,为有效预防治疗泌尿系统结石症的研究提供理论参考。     

BETA-AMYLASE SULPHYDRYL AND DISULPHIDE GROUP REACTIONS. ADDITIONAL ASPECTS ON ENZYME INHIBITION BY ASCORBIC ACID

Cysteine, EDTA and certain other sulphydryl and chelating agents activated barley β-amylase at pH 7 but not at pH 4·35. Apart from oxalate and citrate the same reagents prevented ascorbic acid inhibition of the enzyme. A partial purification of the enzyme was effected on SP-Sephadex C-50 in the presence of mercaptoethanol and Ellman's reagent was reduced when incubated with ascorbic acid and the more active fraction which was isolated. When Ellman's reagent was added to an enzyme system containing additional copper which was incubated with ascorbic acid, a reduction of the synthetic disulphide reagent still occurred. An observable increase in absorbance at 360 nm was also noted in a similar enzyme system. The results suggest that the ascorbate free radical is readily attracted to the exposed disulphide bonds of β-amylase     

The effect of storage on the oxalate content of New Zealand grown oca

Four lines of oca, No. 38 and 41, Inca Gold and Market were grown in four replicated plots and the soluble oxalate content was determined on the freshly harvested tubers and tubers that had been stored for 6 weeks at 16.4 ± 0.5 °C. The mean dry matter content of freshly harvested tubers was 14.3 ± 0.5 g 100 g^?1 fresh weight (FW), and after storage was 14.6 ± 0.5 g 100 g^?1 FW. The mean soluble oxalate content of freshly harvested tubers was 162.1 ± 8.8 mg 100 g^?1 FW, and, after 6 weeks storage, 173.5 ± 0.9 mg 100 g^?1 FW. The different cultivars behaved differently during storage, the soluble oxalate content of Inca Gold tubers fell 7.2% while the soluble oxalate content of the other three cultivars increased (mean 13%).     

A soybean cultivar lacking lipoxygenase 2 and 3 has similar calcium bioavailability to a commercial variety despite higher calcium absorption inhibitors

ABSTRACT:  The aim of this study was to evaluate calcium bioavailability of a new soybean variety without 2 lipoxygenases with better taste and flavor than a commercial variety containing all 3 isozymes. Using the femur ⁴⁵Ca uptake method, calcium absorption from a new Brazilian variety, UFV-116, was compared to a common Brazilian variety, OCEPAR 19. Male Sprague–Dawley growing rats weighing 150 to 170 g (10/group) received test meals of whole fat soy flour prepared from UFV-116 or OCEPAR-19 seeds labeled with 10 μCi of ⁴⁵Ca. Femurs were removed after 48 h for determination of ⁴⁵Ca uptake. Calcium fractional absorption was equivalent between the 2 varieties. The higher oxalate:calcium molar ratio and the higher content of oxalate and phytate ( P < 0.05) found in the UFV-116 variety did not affect calcium absorption. Therefore, the new variety is a comparable source of high bioavailable calcium.