PbPH5,an H^(+)P-ATPase on the tonoplast,is related to malic acid accumulation in pear fruit

Organic acid content is one of the most important factors influencing fruit flavors.The predominant organic acid in most pear cultivars is malic acid,but the mechanism controlling its accumulation remains unclear.In this study,by comparing gene expression levels and organic acid contents,we found that the expression of PbPH5,which encodes a P_(3A)-ATPase,is highly correlated with malic acid accumulation in four different pear species,with correlation coefficients of 0.932**,0.656*,0.900**,and 0.518*(*,P<0.05;**,P<0.01)for Pyrus bretschneideri Rehd.,P.communis Linn.,P.pyrifolia Nakai.,and P.ussuriensis Maxim.,respectively.Moreover,the overexpression of PbPH5 in pear significantly increased the malic acid content.In contrast,silencing PbPH5 via RNA interference significantly decreased both its transcript level and the pear fruit malic acid content.A subcellular localization analysis indicated that PbPH5 is located in the tonoplast.Additionally,a phylogenetic analysis indicated that PbPH5 is a PH5 homolog gene that is clustered with the Petunia hybrida,Malus domestica,and Citrus reticulata genes.Considered together,these findings suggest that PbPH5 is a functionally conserved gene.Furthermore,the accumulation of malic acid in pear fruit is at least partly related to changes in the PbPH5 transcription levels.

Trace determination of cobalt ion by using malic acid-malonic acid double substrate oscillating chemical system

A novel kinetic method for determination of trace amounts of cobalt ion was proposed and validated. The method is based on adding malic acid into classical Belousov-Zhabotinskii （B-Z） oscillating chemical system to form a double substrate one. The results showed that when the concentration of cobalt ion was in the range of 5.27× 10^-8 to 5.37 × 10^-12 mol L^-1, the change of the oscillating period was directly proportional to the negative logarithm of cobalt ion concentration. The sensitivity and precision of the developed method were quite satisfactory. The limit of detection was down to 5.20 × 10^-13 mol L^-1 which was a highest sensitivity found for determination of metal ions using oscillating chemical reaction so far. Some factors influencing the determination were also examined. The method has been successfully used to determine cobalt ion in vitamin B12 injection.

A convenient synthesis of methyl 2-hydroxy-4-oxo-4-(substituted phenyl) butanoates from malic acid

A synthesis of methyl 2-hydroxy-4-oxo-4-（substituted phenyl）butanoates has been accomplished using Friedel-Crafts acylation of substituted benzenes with 2-acetoxybutanoyl chloride. The key feature of this strategy is that various 4-arylbutanoates can be obtained conveniently, which are important intermediates for the synthesis of biologically active compounds including ACE inhibitors.？2009 Yong Sup Lee. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Complexation of Molybdenum （Ⅵ） with R—and S—malic Acid,The Crystal S

Ammonium tetramolybdate ( NH4 )4[(MoO2)4O3 (R-mal)2]·6H2O(mal= malic acid)and (NH4)4[(MoO2)4O3(S-mal)2)·6H2O have been prepared by the reaction of R and S-malic acid with ammonium heptamolybdate, respectively. The two complexes are enantiomeric and isomorphous. The complex of Risomer crystallizes in monoclinic space group C2 with unit cell parameters:a = 14. 591 (2 ), b = 10. 108(2), c=11. 464(2), β=121. 48(1)°, V=1441. 9(4),Z=2, Fω=1002. 13, Dc=2. 308, Dm=2. 3 g/cm3. F(000) = 988, MoKα radiation (λ=0. 71073 ), μ (MoKα) = 17. 7 cm-1. Final R=0. 027 for 1491 reflections with I>2. 5 σ(I). Analysis of molecular structure reveals that the complex anion contains a (Mo2O5)O(Mo2O5)core with the bridging oxo-group passing through two-fold axis. Each molybdenum is hexacoordinated , and the malate ligand is quadridentated to two molybdenum atoms by the deprotonated hydroxy-, α- and β-carboxylate groups. Principal dimensions are:[Mo=O(t)]av, 1. 705(6); [Mo-O(b)]av, 1. 920(6); Mo-O(hydroxy). 1. 925(6);Mo-O(α-carboxy), 2. 226 (6), and [Mo-O(β-carboxy)av, 2. 296 (5).Lattice water is distributed throughout the cell and together with various types of the anion oxygens, making H-bonding.

Preliminary Study on Lipase-catalyzed Synthesis of Polyesters Containing L-Malic Acid Units

Terpolymer of 1, 8-octanediol, adipic acid, and L-malic acid was synthesized via a lipase-catalyzed direct polycondensation. The products were characterized by GPC and 1H NMR. The results indicated that the molecular weight of the prepared polymers decreased with increasing L-malic acid content in the monomer feed ratio, and that change in the L-malic acid content from 0 to 20 mol % did not remarkably influenced on the molecular weight distribution Mw /Ma of the prepared samples. The 1H NMR spectra of the obtained copolymer samples showed that hydroxyl groups of L-malic acid did not take part in the polymerization reaction.

PREPARATION AND CELL COMPATIBILITY OF FUNCTIONALIZED BIODEGRADABLE POLY(DL-LACTIDE-co-RS-β-MALIC ACID)

In order to create a functionalized biodegradable polymer for vascular tissue engineering application,poly(DL- lactide-co-RS-β-malic acid)(PDLLMAc)was synthesized.PDLLMAc was obtained after hydrogenolysis of poly(DL- lactide-co-RS-β-benzyl malolactonate)(PDLLMA),which was from the ring-opening polymerization of DL-lactide(DLLA) and RS-β-benzyl malolactonate(MA)using stannous octoate as catalyst.The copolymers were characterized by ~1H-NMR, FTIR,GPC and DSC.The tensile strength and water uptake of the copoly...

Highly selective/enantioselective Pt-ReOx/C catalyst for hydrogenation of L-malic acid at mild conditions

The catalyst preparation strategy was based on a strict introduction sequence of rhenium and platinum precursors and their strong interaction with carbon support resulted in the formation of 0.5 nm Pt-Re Ox species of atomic dispersion, where platinum is metallic, while monolayer rhenium is partially oxidized（Re2＋）. The reaction kinetics was studied taking into account the process of L-malic acid association leading to the formation of inactive cyclic oligomeric species. High TOFs（ca. 50 h-1）, selectivities（ca. 99%）and stability of Pt-Re Ox/C catalysts in aqueous-phase hydrogenation of L-malic acid, which are close to those of the homogeneous pincer type complexes, were revealed at mild conditions（T = 90–130 ℃）. Taking into account that（i） hydrogenation reaction occurred 2–3 orders of magnitude faster than its racemization and（ii） association of L-malic acid dominates at low temperatures and in a concentrated solution,special reaction conditions that allow obtaining chemically and optically（ee 〉 99%） pure（S）-3-hydroxy-γ-butyrolactone and（S）-1,2,4-butanetriol were found. Basing on HAADF-STEM, EDX, XPS, and kinetic studies, the structure of active species and basic reaction pathways are proposed.

Density Functional Theory Study of Infrared and Ultraviolet Spectra of Urea L-Malic Acid

脲 L 苹果酸的酸，一份新秒订单非线性的光水晶，用密度被学习功能的理论(DFT ) 。PBEPBE/6-31+G (d， p ) 方法，为从几个 DFT 方法比较结果的最佳的方法，被选择学习分子的结构。红外线、紫外可见的系列被获得并且与实验相比。紫外可见的光谱被分子的轨道的人口也分析。几何学，和水里的红外线、紫外可见的系列与极化的连续统模型一起在联合用 DFT 方法被学习由溶剂效果预言不安。

Separation and Structure of Chiral S-Malic Acid Hydrate

Crystals of the chiral malic acid hydrate (C_4H_6O_5·H_2O) were unexpectedlyobtained from an ethanol/water solution containing racemic D, L-malic acid and L-asparagine. Thecrystal belongs to orthorhombic space group P2_12_12_1 with cell dimensions of a = 0.5576(1), b =0.9818(2), c = 1.1793(2) nm, V = 0.6455(2) nm^3, Z = 4, μ(Mo K_a) =0.152 mm^(-1), F(000) = 320, D_c= 1.565 g·cm^(-3), R=0.051, wR = 0.136 for 657 observed reflections [ I > 2σ(I) ]. Thesignificant difference in bond distances for carboxyl groups suggests that the crystal consist ofmalate anion and protonized crystalline water. This is a report for direct separation of racemicmixture, i.e., without the formation of a molecular complex of raceme with a chiral separatingreagent.

Equilibrium of Extraction of Succinic, Malic, Maleic and Fumaric Acids with Trioctylamine

Extraction equilibrium features of succinic acid,malic acid,maleic acid and fumaric acid were investigated systematically with trioctylamine (TOA) in chloroform,4-methyl-2-pentanone (MIBK) and 1-octanol.Fourier transform-infrared(FTIR) spectroscopic analysis of organic samples loaded with the acid show that amine forms 1:1 complex of ion-pair association with succinic acid,malic acid and maleic acid,and 1:1,2:1 complex of ion-pair association with fumaric acid.It is proposed that the complex forms depend on the second dissociation constant of the dibasic acid,pKa2.Results of equilibrium experiments show that diluents affects extraction behavior,and depend on the solute concentration.Protic diluents,chloroform and 1-octanol,are more effective than the others when the equilibrium solute concentration.Protic diluents,chloroform and 1-octanol,are more effective tthan the others when the equilibrium solute concentration is lower than 1:1 stoichiometry of TOA to acid,otherwise the extraction ability shows that MIBK>1-octanol>chloroform for malic and maleic acids,and 1-octanol>MIBK>chloroform for succinic acid.Overloading(Solute concentration in organic phase is lager than TOA concentration) appears for all of the studied acids, and the sequence of overloading amount is the same as that of distribution constant of diluent.The results show that the sequence of extraction ability of different acid is the same as that of acidity at low equilibrium solute concentrations,while it is the same as the sequence of hydrophobicity at high equilibrium concentrations.

外源有机酸对复垦土壤中重金属Cr的活化效果研究

为了探究低分子有机酸(柠檬酸和苹果酸)对Cr污染土壤中Cr形态分布的影响,以淮南市潘一矿煤矸石山周边的复垦土壤为研究对象,通过模拟不同浓度Cr污染土壤,分析柠檬酸(CA)和苹果酸(MA)对土壤中Cr赋存形态的影响机制。结果表明:(1)随着外源Cr浓度的增加,土壤中Cr的活性有效提高。(2)柠檬酸和苹果酸的加入均可增加土壤中可交换态Cr的占比,即Cr的有效性得到提高,且随着柠檬酸和苹果酸浓度的升高,对土壤中Cr活化效果持续上升,柠檬酸的活化效果优于苹果酸。(3)随着老化时间的延长,有机酸对Cr的活化效果会减弱,弱结合态Cr将逐渐向强结合态Cr转化。因此,土壤重金属Cr污染修复中,可以考虑选用活化效果较好的柠檬酸作为修复辅助剂,来提升土壤Cr修复效率。研究结果可为矿区复垦土壤重金属Cr污染修复提供指导。

苹果酸大米淀粉酯的制备及其对面条品质特性的改善

为探究不同取代度(Degree of Substitution,DS)对苹果酸大米淀粉酯理化特性及对面条品质的影响,制备不同取代度(DS=0~0.603)苹果酸大米淀粉酯,考察了苹果酸大米淀粉酯溶解度、溶胀度、糊化特性和流变特性,以及对面条蒸煮特性、质构特性和感官特性的改善作用。结果表明,苹果酸淀粉酯的红外光谱分析显示在光谱波数约1720 cm-1处出现一个新的吸收峰。淀粉发生酯化反应后溶解度显著升高(P<0.05),但溶胀度有所下降。糊化和流变实验结果表明,低酯化淀粉(DS=0.141~0.442)的加入显著降低(P<0.05)了淀粉的峰值黏度,降低了苹果酸淀粉酯的储能模量G′和损耗模量G″,高酯化淀粉(DS=0.603)的添加不利于改善苹果酸淀粉酯的糊化和流变特性。利用相关性分析对苹果酸淀粉酯部分理化指标(溶解度、溶胀度和糊化特性)和面条的品质(蒸煮特性、质构特性和感官特性)进行了综合分析。苹果酸大米淀粉酯可以显著提升面条的整体品质,在本实验中,取代度为0.442时,小麦粉制备的面条品质较佳。

大豆铝激活苹果酸转运家族基因GmALMT8的鉴定与功能验证

鲜食风味是影响菜用大豆食味品质的关键因素,其形成与有机酸有着密切的关联,研究有机酸合成机制对于菜用大豆的品质改良具有重要的实际意义。本研究利用大豆毛状根系统,探究与苹果酸含量显著相关的候选基因GmALMT8、GmIF7GT5和GmAP在调控苹果酸含量方面的功能,结果表明:在GmALMT8-OE毛状根中,GmALMT8基因表达量与苹果酸的含量均显著高于空载对照毛状根,而GmIF7GT5和GmAP毛状根中苹果酸的含量无显著变化。鉴于已经报道的ALMT家族基因的苹果酸转运功能,推测大豆中GmALMT8基因可能具有相似的功能,在调控苹果酸含量方面发挥重要作用。为验证GmALMT8-OE毛状根中苹果酸含量的变化是否由GmALMT8基因表达的改变所引起,本研究采用蘸花法在拟南芥中过表达GmALMT8基因。与阳性毛状根中苹果酸测定的结果相类似,过表达GmALMT8显著提高了T2代转基因拟南芥株系种子中的苹果酸含量,进一步证明GmALMT8的稳定表达能够提高苹果酸含量,明确GmALMT8基因在大豆中具有调控苹果酸含量的生物学功能,丰富了大豆有机酸的理论研究,对菜用大豆优质育种具有参考价值。

日粮添加生物法苹果酸在中试条件下对肉鸡生产的影响

本试验旨在评估生物法苹果酸产品在肉鸡大群试验中的促生长和肉质改善效果,为生物法苹果酸在肉鸡饲粮中的推广应用提供数据支撑。选用1000只1日龄的爱拔益加肉仔鸡公雏,随机分为2个处理,每个处理10个重复,每个重复50只鸡。对照组饲喂玉米-豆粕型基础日粮,处理组在基础日粮中添加0.8%生物法苹果酸。试验持续42 d。结果表明:日粮添加0.8%生物法苹果酸对肉鸡采食量、死淘率无显著影响(P> 0.05),但能通过增加试验后期(22~42 d)平均日增重(7.53%)(P=0.001)和降低料重比(4.47%)(P=0.002)有效增加肉鸡42 d出栏重(4.93%)(P <0.001);在屠宰性能和肉品质方面,日粮添加苹果酸对全净膛率、胸肌率、腿肌率、腹脂率、胸肌肉色和pH均无显著影响(P> 0.05),但能显著降低胸肌肉的滴水损失(11.31%)(P <0.001)。日粮添加0.8%苹果酸可以在中试条件下有效提高肉鸡的生长性能,增强鸡肉保水性,改善肉品质。因此,本研究推荐生物法苹果酸作为饲料添加剂,在集约化养殖的背景下应用于肉鸡饲粮。

重组大肠杆菌全细胞转化苹果酸合成丙酮酸

拟建立一条以苹果酸为原料,通过大肠杆菌全细胞转化获得丙酮酸的合成途径。以大肠杆菌BL21(DE3)为宿主,在pET28a上共表达内源的苹果酸酶(ME)和来自博伊丁假丝酵母(Candida boidinii)的醛糖还原酶(AR),并对细胞浓度、底物浓度、温度和pH值等催化关键因素进行研究。共表达后大肠杆菌苹果酸酶和博伊丁假丝酵母醛糖还原酶酶活分别为(2.8±0.21),(3.1±0.34)U/mL。适宜的催化条件为:细胞浓度OD600nm值为30,底物苹果酸质量浓度为30 g/L,木糖和苹果酸物质的量比为1.0,温度为40℃,反应体系pH值为7.8,丙酮酸产量最高可达23.16 g/L。本研究为生物法合成丙酮酸提供了一种新的方法。

产聚苹果酸出芽短梗霉的筛选、鉴定及发酵培养基优化

从自然土壤样本中筛选得到一株产聚苹果酸(PMLA)菌株,该菌株经形态学观察和分子进化分析鉴定为出芽短梗霉(Aureobasidium pullulans)。筛选菌株同时具有聚苹果酸、普鲁兰多糖和liamocin胞外聚合物的合成能力。通过单因素和响应面试验对该菌种产PMLA的发酵培养基组分进行优化,获得较优培养基组分为葡萄糖130 g/L、硝酸钠5 g/L、玉米浆1.22 g/L、氯化钾0.5 g/L、磷酸二氢钾0.1 g/L、七水硫酸镁0.2 g/L、碳酸钙30 g/L,采用该培养基获得聚苹果酸的最大产量为25.82 g/L,比优化前提高了70.72%。

一株产L-苹果酸黑曲霉菌株的诱变筛选及发酵培养基优化

为筛选一株产L-苹果酸能力强的黑曲霉菌株,通过紫外诱变与高浓度放线菌酮迭代诱变的方法,将野生型菌株诱变为一株产L-苹果酸能力强的黑曲霉菌株,并对其种子或发酵培养基成分进行优化。结果表明,诱变所得一株产L-苹果酸能力强的黑曲霉CGMCC NO.40550菌株,其摇瓶发酵时种子培养基最适葡萄糖浓度为60 g/L、最适氮源为(NH_4)_2SO_4 4.95 g/L,黑曲霉菌球形成最优转速220 r/min;发酵培养基最适葡萄糖和最适(NH_4)_2SO_4浓度分别为180 g/L和4.95 g/L,Cu SO_4·5H_2O为其生产苹果酸最佳微量元素,最适添加量为0.065 g/L。通过单因素实验的优化,优化后的培养基更有利于L-苹果酸的合成,发酵96 h时L-苹果酸产酸量达到18.15 g/L,显著提高了245%,L-苹果酸占总酸的百分比达到71.69%。本研究为L-苹果酸的工业化生产奠定基础。

大肠杆菌苹果酸有氧发酵溢出机制的解析及其应用

L苹果酸是一种重要的四碳二羧酸,以可再生生物质为原料,通过微生物发酵高效制备L苹果酸具有重要意义。本研究首先考察了氮限制条件、温度和pH对有氧条件下L苹果酸合成的影响,结果表明氮限制条件是苹果酸大量积累的重要条件,最适的温度为35℃,最优pH为6.8。进一步分析辅因子水平及呼吸链相关基因的转录水平变化后发现,苹果酸的溢出可能是由于电子呼吸链效率下降,导致NADH的氧化不足,NAD+供给不足最终无法催化苹果酸进一步转化为草酰乙酸。通过敲除大肠杆菌中呼吸链NADH脱氢酶Ⅱ编码基因ndh,可降低电子呼吸链效率。最终重组菌E.coli AFP111(Δndh)在氮源充足条件下,丁二酸也能被大量代谢并以苹果酸为主要产物,收率达到0.65 g/g。本研究成果将为通过呼吸链改造提高中间代谢产物的积累提供理论支持和借鉴。

甲基丙烯酸苹果酸酯光固化树脂的制备及性能

相比于传统的热固性树脂,光固化树脂是一种分子量较低的感光树脂,可在紫外光照射下迅速发生物理和化学变化,具有能源利用率高、固化放热低的特点。因此提出了一种甲基丙烯酸苹果酸酯光固化树脂的制备方法,利用DL-苹果酸多官能团的优点将甲基丙烯酸接枝在树脂的侧链,并研究了DL-苹果酸不同含量对树脂性能的影响。合成的树脂在侧链含有不饱和双键,树脂添加光引发剂后在光照下可以短时间内固化。由于苹果酸在架构上与丁二酸相接近,所以合成的树脂具有优异的力学性能,断裂伸长率可达38.52%,断裂强度可达19.25 MPa,是一种性能优异的光固化树脂。