影响反胶束体系萃取蛋白能力的因素及机理

该文对影响二-（2-乙基已基）琥珀酸酯磺酸钠（AOT）反胶束萃取蛋白能力的因素与机理进行了研究,可以用来解释AOT/异辛烷反胶束溶液分离萃取蛋白与油脂时,萃取率变化的原因,进一步了解反胶束分离萃取蛋白质分子的机理。试验结果表明随着反胶束体系中黏度增加,微乳液增溶水量即水的物质的量与表面活性剂物质的量之比（W0）增大时,使得反胶束萃取蛋白质与油脂的能力增强,从而使萃取率升高。根据Gibbs吸附公式,得出AOT浓度在0.08 g/mL时,反胶束液具有较高的界面活性,W0值也较大,有利于提取蛋白质。利用荧光光谱法和电导法研究AOT反胶束体系的结构,可知W0为11～14时,AOT浓度大于0.06 g/mL,反胶束体系较稳定,该体系是由渗透型和非渗透型的结合,从而可以了解反胶束体系的相行为变化。     

反胶束萃取大豆蛋白反萃取过程的动力学研究

该文通过系统地研究影响总传质系数的各个主要因素（水相pH值、离子强度，初始有机相中蛋白质浓度、振荡速度和反萃取温度）,探讨了以丁二酸二异辛酯磺酸钠(AOT)/异辛烷反胶束体系反萃取大豆蛋白的动力学。结果表明，大豆蛋白反萃取过程中总传质系数，随着反萃取水相的pH值和温度的升高而增大；随着离子强度的增大而先增大后减小；随着振荡速度和初始有机相中蛋白质浓度的增大而几乎不变。说明在反萃取过程中，大豆蛋白在有机相和水相两相内的扩散阻力可以忽略，界面阻力是传质过程中的主要阻力。由此推断出大豆蛋白的反萃取过程属于界面控制类型，“满胶束”在界面上的聚结过程是反萃取的速率控制步骤。通过研究，深入了解了大豆蛋白反萃取过程的机理，可有效地控制和强化萃取过程，提高萃取率，为今后的研究提供可靠的基础数据和理论依据。     

单宁酶处理提高茶梗儿茶素含量及茶梗提取液生物活性

为综合利用茶叶加工副产物茶叶梗,试验设计利用固态发酵得到的单宁酶处理茶梗,比较不同处理条件下的茶梗提取液中儿茶素组成的差异及还原力、DPPH和OH自由基清除率、胰α-淀粉酶和胰脂肪酶抑制活性变化,探讨单宁酶处理提高茶梗提取物中儿茶素含量和生物活性可行性。研究发现：在50℃条件下,利用2 U/mL单宁酶溶液作用于茶梗粉末60 min,茶梗提取液中酯型儿茶素（EGCG、ECG、GCG）基本被水解生成非酯型儿茶素（EGC、EC、GC）和没食子酸（GA）,从而减少单宁-蛋白质聚合物和茶乳的形成量;此外,经单宁酶处理的茶梗提取液抗氧化活性与对照比较明显增强,表现为OH和DPPH自由基清除率IC50分别降低了74%和26%;酶解茶梗提取液质量浓度为5 000 mg/L时,胰α-淀粉酶和胰脂肪酶抑制率分别提高了89%和107%。研究结果表明单宁酶可高效水解茶梗提取液中酯型儿茶素,提高茶梗提取液的抗氧化活性以及体外抑制胰α-淀粉酶和胰脂肪酶活性。     

柿子单宁的制备及其抗氧化活性研究

利用含有1％盐酸的无水甲醇提取柿子果肉中的单宁，粗提液经大孔树脂AB-8初步纯化后，再经超滤膜法制得柿子单宁两级分：高分子量单宁(High Molecular Weight Tannin，HMWT)以及小分子量单宁(Small Molecular Weight Tannin，SMWT)。HMWT具有良好的水溶性，凝胶渗透色谱(GPC)分析表明其分子量分布范围为1.16×10⁴～1.54×10⁴。抗氧化试验表明：HMWT对2-脱氧-D-核糖、甲基紫、水杨酸体系产生的羟基自由基均具有很强的清除能力，其最大清除率分别为90.47%、96.46%、87.77%，；HMWT对邻苯三酚自氧化和亚油酸脂质过氧化亦有较强的抑制作用，其最大抑制率分别为56.57%、69.63%。在所有体系中HMWT抗氧化能力呈明显的剂量效应关系，且效果均强于相同浓度的葡萄籽原花青素(OPC)及SMWT，同时表明HMWT是柿子单宁的主要抗氧化活性组分。     

壳聚糖没食子酸衍生物酶法制备及对鲜切苹果的保鲜效果

为提高壳聚糖水溶性和保鲜性能,该文以没食子酸为配体,漆酶为催化剂催化壳聚糖与没食子酸发生接枝反应,得到壳聚糖没食子酸衍生物,对其结构进行了初步表征,并初步探讨了其对鲜切苹果的保鲜效果。结果表明,衍生物接枝率为72.80%,溶解度达到92.77%,没食子酸中的羧基与壳聚糖分子的氨基发生了迈克尔加成反应,在壳聚糖的C2位生成了酰胺键。14℃下贮藏4 d后,10 mg/m L衍生物处理的苹果硬度损失率仅为10.23%,比空白组、壳聚糖处理组和壳聚糖没食子酸物理复合物处理组分别低20.90%(P0.05)、16.60%(P0.05)和15.60%(P0.05);可溶性固形物、维生素C、谷胱甘肽和多酚质量分数分别为12.93%,1.23 mg/(100 g),6.26 mg/(100 g)和6.24 mg/(100 g),分别比空白组高16.47%(P0.05),48.78%(P0.05),24.92%(P0.05)和43.75%(P0.05);多酚氧化酶和过氧化物酶活性分别比空白组低36.73%(P0.05)和76.94%(P0.05);菌落总数为16.00×10~4 CFU/g,显著低于空白组、壳聚糖处理组和壳聚糖没食子酸物理复合物处理组(P0.05)。结果表明,漆酶可催化壳聚糖与没食子酸发生接枝反应,得到的壳聚糖没食子酸衍生物对鲜切苹果具有较好的保鲜效果。     

2-羟基-4-甲氧基苯甲醛和2-羟基-4-甲氧基苯甲酸对菜粉蝶多酚氧化酶的抑制作用

测定了2羟-基-4-甲氧基苯甲醛和2羟-基-4-甲氧基苯甲酸两种效应物对菜粉蝶多酚氧化酶(po lypheno lox idase,简称PPO,EC.1.14.18.1)催化L-多巴(L-DOPA)氧化活力的抑制作用。结果表明,这两种效应物对该酶的活性均有明显的抑制作用,抑制中浓度(IC50)分别为2.71和5.66 mm o l/L,抑制常数分别为2.82和3.35 mm o l/L;2羟-基-4-甲氧基苯甲醛对该酶的抑制作用显著高于2羟-基-4-甲氧基苯甲酸的;这两种抑制剂对酶的抑制作用机理完全不同,2羟-基-4-甲氧基苯甲醛对酶的作用表现为混合型抑制,而2羟-基-4-甲氧基苯甲酸对酶的作用表现为竞争性抑制。研究结果为设计以该酶为靶标的杀虫剂提供理论依据。     

生物质炭短期添加对不同类型土壤水力性质的影响

为探究生物质炭添加对农田土壤水力性质的影响，以我国10个地区农田耕层土壤为供试土样，通过室内模拟试验，研究4种生物质炭添加比例下(C0、C5、C10和C15，生物质炭体积占比分别为0%、5%、10%和15%)土壤饱和导水率(Ks)、水分特征曲线及van Genuchten模型拟合参数和水分常数的变化特征。结果表明：生物质炭添加对土壤渗透性能的影响与土壤质地密切相关；添加生物质炭后，砂粒含量较高的风砂土和黄绵土的Ks显著降低，C15的降幅分别为89.2%和85.0%；而黏粒含量较高土壤的Ks普遍升高，C15处理下赤红壤的增幅高达158.9%。生物质炭添加改变了土壤的持水能力，且变幅随着生物质炭添加量的增加而增大。生物质炭添加提升了各类土壤的饱和含水量(0.7%～17.6%)和低吸力段的持水能力；生物质炭添加对中、高吸力水平下各类土壤持水能力的影响存在差异，大致表现为砂质土持水能力提升、残余含水量增大、α值降低；而壤质、黏质土持水能力下降，残余含水量、田间持水量及凋萎系数均降低。研究结果可为考虑生物质炭施用的平衡模拟提供水力学基础参数，并为各地区农田生物质炭的合理施用提供科学依据。     

液氨和过氧化氢预处理对稻草酶解效果的影响机制

稻草是一种重要的木质纤维素资源,可以作为纤维素乙醇转化的原料。该试验通过高温过氧化氢(高温HP)、低温过氧化氢(低温HP)和液氨预处理(liquid ammonia treatment,LAT)3种预处理方式来克服生物质原料的酶解顽抗性,促进稻草酶解转化为可发酵单糖。对预处理后的稻草进行酶解试验,利用高效液相色谱法(highperformanceliquid chromatography,HPLC)定量测定了酶解液中的单糖含量,通过酶解转化率和单糖产量对预处理效果进行了分析比较。试验结果表明高温HP、低温HP和LAT 3种预处理方式均有效提升酶解率,其中LAT预处理的酶解促进作用效果最佳,高温HP预处理次之。稻草在120℃、预处理时间为60 min、30%H2O2水溶液与原料质量比为0.75∶1的高温HP预处理下,在纤维素酶添加量为15U/g时葡聚糖和木聚糖的酶解率分别为61.55%和47.82%,每千克干基稻草原料经144h酶解可生产单糖334.5 g。稻草在90℃、含水率60%、驻留时间为5 min、液氨与原料比例为1∶1的LAT预处理下,在纤维素酶添加量为15 U/g时,葡聚糖和木聚糖的72 h酶解率分别为88.62%和79.29%,每千克干基稻草原料经144 h酶解可生产单糖554.1 g,是未处理原料的2.9倍,总糖回收率达到90%。综上所述,LAT预处理稻草的酶解率显著高于其他单一预处理方法,该研究结果可为稻草制取燃料乙醇提供基础数据。     

表面活性剂对超临界CO_2萃取人参中皂苷的影响

为了改善超临界CO2萃取在极性物质方面存在的局限性,在其体系中引入特定表面活性剂和助表面活性剂,考察了它们对超临界CO2萃取人参中皂苷的影响。试验结果发现,表面活性剂和助表面活性剂的加入均可显著提高超临界CO2萃取人参中皂苷的萃取率,其改善效果与它们的种类和加入量有关。在司盘80、吐温80、聚乙二醇辛基苯基醚和琥珀酸二(2-乙基己基)酯磺酸钠4种表面活性剂中,以琥珀酸二(2-乙基己基)酯磺酸钠的改善效果最好,其次是聚乙二醇辛基苯基醚和吐温80,而司盘80最差。在3种助表面活性剂对琥珀酸二(2-乙基己基)酯磺酸钠/超临界CO2反相微乳萃取人参皂苷的改善效果方面,以乙醇效果最好,其次是正戊醇,正丁醇效果最差。在萃取压力32MPa、萃取温度45℃、萃取时间4h和CO2流量2.5L/h的条件下,AOT和乙醇的加入量以0.036g/mL较好,此时人参皂苷的萃取率达15.9%,是没加表面活性剂和助表面活性剂下的13.3倍。     

土壤可培养真菌RAPD扩增条件的优化

以改进的CTAB-溶菌酶-蛋白酶K裂解法抽提土壤可培养真菌总DNA,直接进行随机扩增多态DNA(RAPD)分析。分别测试了镁离子浓度,4×dNTP浓度,模板DNA量,引物用量,Taq酶用量和牛血清白蛋白浓度对反应结果的影响,通过各因子的组合研究,确定了土壤可培养真菌遗传多样性分析的稳定的RAPD反应体系:15μlPCR反应体积,1×Taq酶配套缓冲液(10mmolL-1Tris·HClpH9.0,50mmolL-1KCl,0.1%TritonX-100),1.5mmolL-1MgCl2,2UTaq酶(上海华美公司),20ng模板DNA,15pmol引物(上海Sangon公司);dATP、dCTP、dGTP、dTTP各0.2mmolL-1;1mgmL-1牛血清白蛋白。     

Isolation and characterization of a novel tannase from a metagenomic library

A novel gene (designated as tan410) encoding tannase was isolated from a cotton field metagenomic library by functional screening. Sequence analysis revealed that tan410 encoded a protein of 521 amino acids. SDS-PAGE and gel filtration chromatography analysis of purified tannase suggested that Tan410 was a monomeric enzyme with a molecular mass of 55 kDa. The optimum temperature and pH of Tan410 were 30 °C and 6.4. The activity was enhanced by addition of Ca(2+), Mg(2+) and Cd(2+). In addition, Tan410 was stable in the presence of 4 M NaCl. Chlorogenic acid, rosmarinic acid, ethyl ferulate, tannic acid, epicatechin gallate and epigallocathchin gallate were efficiently hydrolyzed by recombinant tannase. All of these excellent properties make Tan410 an interesting enzyme for biotechnological application.     

Solubilization of water soluble anthocyanins in apolar medium using reverse micelle

Crude anthocyanins extracted from grape skin were solubilized in hexane containing 100 mM bis(2-ethylhexyl)sodium sulfosuccinate (AOT) by forming stable reverse micelles (RMs). Anthocyanins solubilized in RMs showed about four times greater color intensity than that in aqueous medium. The color intensity of anthocyanins in RMs was primarily affected by the interaction between sulfonate head of AOT and flavylium cation of anthocyanins. The molar ratio of water to AOT (Wo) also influenced the color properties. As the Wo increased from five to 20, the color intensity increased and resulted in a bathochromic shift. This result suggests that increased micelle size facilitates complexation between AOT and flavylium cation. The color stability of anthocyanins in RM was higher than that of buffered anthocyanins during the storage at 30 degrees C. The current study might be utilized as a model system to predict color properties of anthocyanins in apolar medium.     

Characterization of novel β-glucosidases with transglycosylation properties from Trichosporon asahii

Two novel β-glucosidases from Trichosporon asahii, named BG1 and BG2, were purified to electrophoretic homogeneity using ammonium sulfate precipitation, hydrophobic interaction, ion exchange, and gelfiltration chromatography. The molecular weight of BG1 and BG2 were estimated as 160 kDa and 30 kDa, respectively. The K(m), V(max), K(cat), and K(cat)/K(m) values of the two β-glucosidases for p-nitrophenyl-β-D-glucopyranoside were determined. Both enzymes showed relatively high affinity to p-nitrophenyl-β-D-glucopyranoside in 4-nitrophenol glycosides and gentiobiose in saccharide substrates. The enzymes exhibited optimum activity at pH 6.0 and pH 5.5, respectively. Their respective optimum temperatures were 70 and 50 °C. Metal ions and inhibitors had different effects on the enzymes activities. Circular dichroism (CD) spectroscopy demonstrated that the purified BG1 exhibited a β-sheet-rich structure and that BG2 displayed a high random coil conformation. HPLC analysis of transglycosylation and reverse hydrolysis assays revealed that only BG1 possessed transglycosylation activity and synthesized cello-oligosaccharides by the addition of glucose. This suggested that BG1 could be used to produce complex bioactive glycosides and could be considered as a potential enzyme for industrial application.     

High performance liquid chromatographic determination of nine phenolic antioxidants in oils, lards, and shortenings

A simple, rapid technique is described for the determination of 2- and 3-tert-butyl-4-hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ), 3,5-di-tert-butyl-4-hydroxytoluene (BHT), 2,6-di-tert-butyl-4-hydroxymethylphenol (Ionox-100), 2,4,5-trihydroxybutyrophenone (THBP), propyl gallate (PG), octyl gallate (OG), dodecyl gallate (DG), and nordihydroguaiaretic acid (NDGA) in vegetable oils, lards, and shortenings. The antioxidants are partitioned from hexane-oil into acetonitrile, concentrated under vacuum, and determined by reverse phase, gradient elution, high performance liquid chromatography with detection at 280 nm. The mobile phase is water-acetonitrile with 5% acetic acid. With this system, only Ionox-100 and OG are not resolved. Recoveries from soya-sunflower seed oil spiked at 16 and 100 ppm and from lard at 32 ppm for 8 of the 9 antioxidants ranged from 96 to 103%, 100 to 102%, and 98 to 102%, respectively. The recoveries of BHT, due to incomplete extraction, were 84, 85, and 87%, respectively.     

Inhibition of xanthine oxidase and suppression of intracellular reactive oxygen species in HL-60 cells by theaflavin-3,3'-digallate, (-)-epigallocatechin-3-gallate, and propyl gallate

The inhibitory effects of five tea polyphenols, namely theaflavin (TF1), theaflavin-3-gallate (TF2), theaflavin-3,3'-digallate (TF3), (-)-epigallocatechin-3-gallate (EGCG), and gallic acid, and propyl gallate (PG) on xanthine oxidase (XO) were investigated. These six antioxidant compounds reduce oxidative stress. Theaflavins and EGCG inhibit XO to produce uric acid and also act as scanvengers of superoxide. TF3 acts as a competitive inhibitor and is the most potent inhibitor of XO among these compounds. Tea polyphenols and PG all have potent inhibitory effects (>50%) on PMA-stimulated superoxide production at 20 approximately 50 microM in HL-60 cells. Gallic acid (GA) showed no inhibition under the same conditions. At 10 microM, only EGCG, TF3, and PG showed significant inhibition with potency of PG > EGCG > TF3. The superoxide scavenging abilities of these six compunds are as follows: EGCG > TF2 > TF1 > GA > TF3 > PG. PG was the most potent inhibitor of PMA-stimulated H(2)O(2) production in HL-60 cells. The order of H(2)O(2) scavenging ability was TF2 > TF3 > TF1 > EGCG > PG > GA. Therefore, the antioxidative activity of tea polyphenols and PG is due not only to their ability to scavenge superoxides but also to their ability to block XO and related oxidative signal transducers.     

Synthesis, structure analyses, and characterization of novel epigallocatechin gallate (EGCG) glycosides using the glucansucrase from Leuconostoc mesenteroides B-1299CB

In this study, three epigallocatechin gallate glycosides were synthesized by the acceptor reaction of a glucansucrase produced by Leuconostoc mesenteroides B-1299CB with epigallocatechin gallate (EGCG) and sucrose. Each of these glycosides was then purified, and the structures were assigned as follows: epigallocatechin gallate 7-O-alpha-D-glucopyranoside (EGCG-G1); epigallocatechin gallate 4'-O-alpha-D-glucopyranoside (EGCG-G1'); and epigallocatechin gallate 7,4'-O-alpha-D-glucopyranoside (EGCG-G2). One of these compounds (EGCG-G1) was a novel compound. The EGCG glycosides exhibited similar or slower antioxidant effects, depending on their structures (EGCG > or = EGCG-G1 > EGCG-G1' > EGCG-G2), and also manifested a higher degree of browning resistance than was previously noted in EGCG. Also, EGCG-G1, EGCG-G1', and EGCG-G2 were 49, 55, and 114 times as water soluble, respectively, as EGCG.     

Oxidative dimers produced from protocatechuic and gallic esters in the DPPH radical scavenging reaction

DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging reactions of protocatechuic and gallic acids, and their methyl esters, have been investigated by NMR. In acetone, methyl protocatechuate was gradually converted to a Diels-Alder adduct of two molecules of the intermediate quinone in the reaction with DPPH radical, whereas methyl gallate rapidly gave a symmetrical dimer via a putative quinone precursor. Both dimers are rather unstable and their structures have been deduced by in situ NMR measurements of the reaction mixtures. Gallic acid also gave a corresponding symmetrical dimer in the same reaction as methyl gallate, although protocatechuquinone produced from protocatechuic acid did not yield a Diels-Alder adduct, unlike its methyl ester. Interestingly, these dimer formations were not observed in methanol solution.     

Simultaneous stopped-flow determination of butylated hydroxyanisole and propyl gallate using a T-format luminescence spectrometer

A simple and fast luminescent method is used for the first time to resolve a mixture of two synthetic antioxidants, propyl gallate (PG) and butylated hydroxyanisole (BHA), by the joint use of the stopped-flow mixing technique and a T-format luminescence spectrometer. The determination of these compounds involves two different and independent reactions. On the one hand, PG determination is based on an energy transfer process that involves the formation of a lanthanide chelate with terbium in the presence of Triton X-100 and tri-n-octylphosphine oxide. On the other hand, BHA is determined using a reaction between the oxidized form of Nile Blue and the antioxidant. Both systems are excited at the same excitation wavelength (310 nm), and the emission wavelengths are 545 and 665 nm for PG and BHA, respectively. The absence of overlap in the emission spectra makes it possible to measure separately the analytes in each channel of the instrument. Initial rate and equilibrium signal are used as analytical parameters and measured in 0.1 and 1 s for PG and BHA, respectively. Calibration graphs are linear over the range 0.09-3.5 microg mL(-)(1) for PG and 0.3-15 microg mL(-)(1) for BHA. The relative standard deviations of both systems are close to 2%. The proposed method is applied to the determination of these two antioxidants in several commercial food samples with recoveries ranging between 94.8 and 102.9% for PG and between 94.1 and 102.1% for BHA.     

Antioxidant activity of dodecyl gallate

Dodecyl (C12) gallate exhibits both potent chain-breaking and preventive antioxidant activity. The pyrogallol moiety is responsible for both activities. Dodecyl (lauryl) gallate prevents generation of superoxide radicals by xanthine oxidase, and this activity comes from its ability to inhibit the enzyme. The inhibition kinetics analyzed by Lineweaver-Burk plots found that dodecylgallate is a noncompetitive inhibitor for the generation of superoxide anion. Dodecyl gallate also inhibits formation of uric acid. The inhibition kinetics analyzed by Lineweaver-Burk plots found that dodecyl gallate is a competitive inhibitor for this oxidation. Mitochondrial lipid peroxidation induced by Fe(III)-adenosine 5'-diphosphate/reduced nicotinamide adenine dinucleotide was inhibited by dodecyl gallate while its parent compound, gallic acid, did not show this inhibitory activity. Dodecyl gallate protected mitochondrial functions and human red blood cells against oxidative stresses, but gallic acid showed little effect. The hydrophobic dodecyl group is largely associated with the preventive antioxidative activity.